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Chapter 6 Airway Management and Oxygenation National EMS Education Standard Anatomy and Physiology Applies fundamental knowledge of the anatomy and function of all human systems to the practice of EMS. Pathophysiology Applies fundamental knowledge of the pathophysiology of respiration and perfusion to patient assessment and management. Pharmacology Applies fundamental knowledge of the medications that the EMT may assist/administer to a patient during an emergency. Airway Management, Respiration, and Artificial Ventilation Applies knowledge of general anatomy and physiology to patient assessment and management to assure a patent airway, adequate mechanical ventilation, and respiration for patients of all ages. Review Perfusion of all cells in the body with oxygen remains the number one priority in patient care. The most critical patients are those with problems with their “ABCs”: airway, breathing, and circulation. If the patient is unable to maintain an open airway, insert an oropharyngeal or nasal airway; if he or she is not breathing, provide rescue ventilations; if breathing is difficult or inadequate, provide supplemental oxygenation and consider rescue ventilations; and if the circulation of blood is absent, perform CPR. To keep the patient’s airway clear, minimize the risk for aspiration, and prevent fluids and secretions from being forced into the lungs while ventilating a patient, it may be necessary to suction the patient. There are many times when a patient needs supplemental oxygenation. The nonrebreathing mask can deliver high-flow oxygen to the patient, while a nasal cannula provides a lesser amount of oxygen. Artificial respirations can be provided by using a bag-mask device, a pocket-sized face mask, or a manually triggered ventilation device. What’s New Even as a seasoned EMT, to fully understand the respiratory conditions that a patient may have, it is important to understand the anatomy and physiology of the respiratory system in detail. In addition, full understanding of the pathophysiology of ventilation, oxygenation, and respiration will help the EMT better understand the signs and symptoms associated with certain conditions as well as management techniques for caring for a patient presenting with such conditions. In addition to the nonrebreathing mask and the nasal cannula, EMTs now have other oxygen delivery devices available to provide supplemental oxygen to the patient. These devices include the partial rebreathing mask, the Venturi mask, and the tracheostomy mask. To prevent drying of the mucous membranes in the nose, humidification of oxygen may be indicated. 09153_ch06_5989.indd 71 71 8/17/11 8:06:12 PM 72 Emergency Medical Technician Transition Manual Introduction Breathing and circulation are two separate but related processes by which oxygen reaches the body’s tissues and cells. During inhalation, oxygen moves from the atmosphere into the lungs, then passes from the air sacs in the lungs (alveoli) into the pulmonary capillaries to oxygenate the blood. At the same time, carbon dioxide produced by cells in the tissues of the body moves from the blood into the alveoli through a process called diffusion. The blood, now enriched with oxygen, travels through the body by the pumping action of the heart. The carbon dioxide then leaves the body during exhalation. Anatomy of the Respiratory System: A Review The respiratory system consists of the various structures of the body that contribute to the process of breathing Figure 1 . They include the nose, mouth, throat, larynx, trachea, bronchi, and bronchioles, which are all air pas- sages or airways. The respiratory system also includes the lungs, where oxygen is passed into the blood and carbon dioxide is removed. Finally, the respiratory system includes the diaphragm, the muscles of the chest wall, and accessory muscles of breathing, which permit normal respiratory movement Figure 2 . The respiratory and cardiovascular systems work together to ensure that a constant supply of oxygen and nutrients are delivered to every cell in the body and that carbon dioxide and waste products are removed from every cell. When one of these systems is compromised, oxygen delivery is not effective and cellular death could result. The process of breathing is typically easy and requires little muscular effort. But now imagine breathing through a straw: The smaller the diameter of the straw, the more effort needed to move air. Thus, as the resistance in the airway increases, additional muscles—namely, the abdominal and pectoral muscles—are needed to assist the diaphragm in moving air. In the respiratory system, air enters the body through the oral and nasal cavities, travels into the laryngopharynx, Nasopharynx Nasal air passage Pharynx Upper airway Oropharynx Mouth Epiglottis Larynx Trachea Alveoli Apex of the lung Bronchioles Carina Main bronchi Base of the lung Lower airway Pulmonary Capillaries Diaphragm Alveoli Figure 1 09153_ch06_5989.indd 72 The respiratory system consists of the various structures of the body that contribute to the process of breathing. 8/17/11 8:06:14 PM Chapter 6 Airway Management and Oxygenation 73 Physiology of the Respiratory System: A Review Lung THORAX Sternum Esophagus While the terms are often used interchangeably, ventilation, oxygenation, and respiration are three distinct processes. If a problem arises in any one of these processes, it can affect other body processes and systems, possibly leading to permanent damage or death table 1 . Ventilation Pulmonary ventilation is the process of moving air into and Vena cava ABDOMEN Aorta Diaphragm Vertebrae Costal arch Figure 2 The dome-shaped diaphragm divides the thorax from out of the lungs through inhalation and exhalation. It is necessary for oxygenation and respiration to occur. Adequate, continuous ventilation is essential for life and, therefore, remains one of the highest priorities in patient care. If the patient has inadequate or absent breathing, immediate action is necessary. Signs of inadequate ventilation include the following: Pulmonary ventilation The process of moving air into and out of the lungs through inhalation and exhalation. the abdomen. It is pierced by the great vessels and the esophagus. ■■ ■■ passes through the vocal cords, moves into the glottis, and flows down the trachea, where it is distributed through the mainstem bronchi into the bronchioles of the lungs. This process occurs because a negative pressure is created in the chest, as described earlier. Eventually the air reaches the alveolar sacs, where the oxygen diffuses across the alveolar membrane into the pulmonary capillaries. At the same time, carbon dioxide diffuses in the opposite direction across this membrane and is exhaled from the body. The oxygen in the pulmonary capillaries is transported to the heart, where it is distributed to the rest of the body. At this point, the circulatory system takes over, with the heart pumping the oxygen-rich blood to the tissues of the body through a series of arteries and veins. Arteries carry oxygenated blood away from the heart, branching into arterioles and capillaries as their distance from the heart increases. In the capillaries, the exchange of nutrients and waste products takes place. Oxygen and nutrients leave the capillaries and enter the cells. At the same time, waste products, such as carbon dioxide, diffuse from the cells back into the blood of the capillaries. At that point, the now oxygen-depleted blood travels through a series of venules that connect to larger veins. All veins carry deoxygenated blood to the heart. The deoxygenated blood enters the right side of the heart through the right atrium, where it is pumped through the tricuspid valve, right ventricle, and pulmonary artery before being sent to the lungs for oxygenation and removal of carbon dioxide. The oxygenated blood then travels through the pulmonary vein to the left atrium through the bicuspid valve and into the left ventricle, where it is again pumped to the rest of the body. 09153_ch06_5989.indd 73 ■■ ■■ ■■ ■■ Altered mental status Inadequate minute volume (shallow or deep respirations) Excessive use of accessory muscles Fatigue from labored breathing Cyanosis Inability to speak in complete sentences (one- or two-word dyspnea) Inhalation Inhalation is the active part of ventilation or breathing, in which a person takes air into the body through the mouth and nose. During this process, the diaphragm and intercostal muscles contract, the thoracic cavity enlarges, and air moves into the trachea and to the lungs via the bronchi, bronchioles, and eventually the alveoli. Because the lungs have no muscle tissue, they cannot move on their own. Instead, they need the help of other structures to be able to expand and contract during Table 1 Ventilation, Oxygenation, and Respiration System Function Ventilation The physical act of moving air into and out of the lungs through inhalation and exhalation Oxygenation The process of loading oxygen molecules onto hemoglobin molecules in the bloodstream Respiration The actual exchange of oxygen and carbon dioxide in the alveoli as well as in the tissues of the body 8/17/11 8:06:15 PM 74 Emergency Medical Technician Transition Manual inhalation and exhalation. As such, their ability to function properly depends on the movement of the chest and supporting structures including the thorax, thoracic cavity (chest), diaphragm, intercostal muscles, and accessory muscles of breathing. chioles; this air is called dead space. Alveolar ventilation is determined by subtracting the amount of dead space air from the tidal volume. Alveolar ventilation The volume of air that reaches the alveoli. It is determined by subtracting the amount of dead space air from the tidal volume. Transition Tip Air can reach the lungs only if it travels through the trachea. As such, maintaining a clear and open airway is essential Figure 3 . This is done by removing obstructing material, tissue, or fluids from the mouth, nose, and throat so that air can enter and leave the lungs freely. Tidal volume is the amount of air that moves into or out of the lungs during a single breath. It is measured in milliliters (mL). The average tidal volume for a man is approximately 500 mL; of that amount, 150 mL may remain in dead space and never reach the alveoli for gas exchange. Minute ventilation, also known as minute volume, is the amount of air that moves through the lungs in a minute, minus the dead space. It is calculated as follows: Minute Ventilation = Tidal Volume (minus Dead Space) ¥ Respiratory Rate Minute ventilation The volume of air moved through the lungs in 1 minute minus the dead space; it is calculated by multiplying the tidal volume (minus the dead space) and the respiratory rate. Also referred to as minute volume. Thus, if the patient is breathing at a rate of 12 breaths/min, with a tidal volume of 500 mL per breath, the minute volume would be 4,200 mL (4.2 L). It is important to understand, however, that minute ventilation is affected by variations in tidal volume and respiratory rate. For example, if a patient has shallow respirations, the minute ventilation will be decreased. Likewise, the minute ventilation will increase if the patient has deep breathing (increased tidal volume). Figure 3 Air reaches the lungs only if it travels through the trachea. Maintaining the airway means keeping the airway patent so that air can enter and leave the lungs freely. The air pressure outside the body—that is, the atmospheric pressure—is normally higher than the air pressure within the thorax. During inhalation, the thoracic cavity expands, decreasing the air pressure and creating a slight vacuum. This vacuum pulls air in through the trachea, causing the lungs to fill. When the air pressure equalizes, air stops moving and inhalation stops. The entire process of inspiration is focused on delivering oxygen to the alveoli (alveolar ventilation). However, not all the air you breathe actually reaches the alveoli. Some air remains in the mouth, nose, trachea, bronchi, and bron- 09153_ch06_5989.indd 74 Exhalation Unlike inhalation, exhalation is a passive process that does not normally require muscular effort. During exhalation, the diaphragm and intercostal muscles relax, the thoracic cavity decreases in size, and air that is in the lungs is compressed into a smaller space. The air pressure within the thorax is then higher than the outside pressure, and the air is pushed out through the trachea. Vital capacity refers to the amount of air that can be forcibly expelled from the lungs after breathing deeply. Even after forceful exhalation, however, it is impossible to completely empty the lungs of air. The amount of air that remains—known as the residual volume—averages approximately 1,200 mL in the average adult male. This residual volume is one of the reasons why CPR can circulate oxygen without providing ventilations. Vital capacity The amount of air that can be forcibly expelled from the lungs after breathing in as deeply as possible. Residual volume The air that remains in the lungs after maximal expiration. 8/17/11 8:06:17 PM Chapter 6 Airway Management and Oxygenation Regulation of Ventilation The body’s need for oxygen is dynamic, meaning it changes constantly. The respiratory system must be able to accommodate these changes in oxygen demand by altering the rate and depth of ventilation. Such changes are regulated primarily by the pH of the cerebrospinal fluid, which is directly related to the amount of carbon dioxide dissolved in the plasma portion of the blood. The regulation of ventilation involves a complex series of receptors and feedback loops that sense gas concentrations in the body fluids and send messages to the respiratory center in the brain to adjust the rate and depth of ventilation accordingly. Failure to meet the body’s needs for oxygen may result in hypoxia, a dangerous condition in which the tissues and cells of the body do not receive enough oxygen. If this process is not corrected quickly, the patient may die. For most people, the drive to breathe is based on pH changes (related to carbon dioxide levels) in the blood and cerebrospinal fluid. However, patients with chronic obstructive pulmonary disease (COPD) have difficulty eliminating carbon dioxide through exhalation; thus they always have higher levels of carbon dioxide. This factor may potentially alter their drive for breathing because the respiratory center in the brain gradually accommodates the high levels of carbon dioxide. In patients with COPD, the body uses a “backup system” to control breathing called hypoxic drive, which is based on levels of oxygen dissolved in plasma. This mechanism differs from the primary control of breathing, which uses carbon dioxide as the driving force. Hypoxic drive is typically found in end-stage COPD. Providing high concentrations of oxygen over time will increase the amount of oxygen dissolved in plasma, which could potentially negatively affect the body’s drive to breathe. Hypoxic drive A condition in which chronically low levels of oxygen in the blood stimulate the respiratory drive; it is seen in patients with chronic lung diseases. Because increased oxygen levels could eliminate a patient’s hypoxic drive, caution should be taken when administering high concentrations of oxygen to patients with COPD. At the same time, it is important to remember that high concentrations of oxygen should never be withheld from any patient who needs it. Patients with severe respiratory or circulatory compromise should receive high concentrations of oxygen regardless of their underlying medical conditions. Oxygenation Oxygenation is the process of loading oxygen molecules onto hemoglobin molecules in the bloodstream. Although adequate oxygenation is required for internal respiration to take place, it does not guarantee that internal respiration is taking place. Oxygenation requires that the air used for ventilation contain an adequate percentage of oxygen. Although 09153_ch06_5989.indd 75 75 you generally cannot oxygenate without ventilation, it is possible to ventilate without oxygenation. This situation occurs when oxygen levels in the air have been depleted, such as in mines and confined spaces, and with carbon monoxide poisoning, where the excess number of carbon monoxide molecules in the body prevent oxygenation of tissues. Ventilation without adequate oxygenation also occurs in climbers who ascend too quickly to an altitude of lower atmospheric pressure. At high altitudes, the percentage of oxygen remains the same, but the atmospheric pressure makes it difficult to adequately bring sufficient amounts of oxygen into the body. Oxygenation The process of delivering oxygen to the blood by diffusion from the alveoli following inhalation into the lungs. Transition Tip Oxygenation can be disrupted through carbon monoxide poisoning. Carbon monoxide has a much greater affinity for hemoglobin than oxygen (250 times more). As such, carbon monoxide molecules will bind to the hemoglobin in the red blood cells instead of oxygen molecules, thereby preventing the proper transport of oxygen to tissues and ultimately resulting in tissue death. Respiration All living cells perform a specific function and need energy to survive. Cells take energy from nutrients through a series of chemical processes. The name given to these processes as a whole is metabolism (or cellular respiration). During metabolism, each cell combines nutrients (such as sugar) and oxygen and produces energy and waste products, primarily water and carbon dioxide. Each cell in the body requires a continuous supply of oxygen and a regular means of disposing of waste (carbon dioxide). The body provides for these requirements through respiration. Metabolism (cellular respiration) The biochemical processes that result in production of energy from nutrients within the cells. Respiration is the process of exchanging oxygen and carbon dioxide. This exchange occurs by diffusion, during which a gas moves from an area of higher concentration to an area of lower concentration. In the body, gases diffuse rapidly across a short distance of only micrometers, and the diffusion occurs rapidly Figure 4 . Respiration The process of exchanging oxygen and carbon dioxide. 8/17/11 8:06:17 PM 76 Emergency Medical Technician Transition Manual Alveoli Pulmonary capillary Systemic capillary Red blood cell Dissolved O2 CO2 in blood Dissolved Interstitial fluid O2 CO2 O2 CO2 Tissue cells Plasma Figure 4 In the capillaries of the lungs, oxygen (O2) passes from the blood to the tissue cells, and carbon dioxide (CO2) and wastes pass from the tissue cells to the blood. Diffusion occurs when molecules move from an area of higher concentration to an area of lower concentration. External Respiration External respiration, also known as pulmonary respiration, is the process of breathing air into the respiratory system and exchanging oxygen and carbon dioxide between the alveoli and the blood in the pulmonary capillaries Figure 5 . External respiration The exchange of gases between the lungs and the blood cells in the pulmonary capillaries; also called pulmonary respiration. Pulmonary arteriole Alveoli Capillaries Pulmonary venule O2 in Alveolus CO2 out Figure 5 09153_ch06_5989.indd 76 External respiration. Capillary Transition Tip Air that is inspired into the lungs contains approximately 21% oxygen, 78% nitrogen, and 0.3% carbon dioxide. Once the oxygen crosses the alveolar membrane, it is bound to hemoglobin, an iron-containing molecule that has a great affinity for oxygen molecules. Through their presence in red blood cells, hemoglobin molecules low in oxygen concentration are pumped from the right side of the heart into the capillaries of the pulmonary circulation. The capillaries surround alveoli containing high concentrations of oxygen (from inspired air). The hemoglobin molecules pick up fresh oxygen as it crosses the alveolar membrane and transport it back to the left side of the heart, where it is pumped out to the rest of the body. Internal Respiration Internal respiration is the exchange of oxygen and carbon dioxide between the systemic circulatory system and the cells of the body. Via its circulation through the body, blood supplies oxygen and nutrients to various tissues and cells. As the oxygenated blood travels through the arteries and capillaries, the oxygen passes from the blood in the capillaries to tissue cells, while carbon dioxide and cell wastes pass in the opposite direction, from tissue cells through capillaries and into the veins Figure 6 . Internal respiration The exchange of gases between the blood cells and the tissues. 8/17/11 8:06:19 PM Chapter 6 Airway Management and Oxygenation Blood cells Tissue cells Capillary Oxygen and nutrients in Carbon dioxide and waste out Figure 6 Internal respiration. Every cell in the body needs a constant supply of oxygen to survive. Whereas some tissues are more resilient than others, eventually all cells will die if they are deprived of oxygen Figure 7 . To deliver adequate amounts of oxygen to the tissues of the body, sufficient levels of external ventilation and perfusion must take place. In the presence of oxygen, the mitochondria of the cells convert glucose into energy through a process known as aerobic metabolism. Energy in the form of adenosine triphosphate (ATP) is produced through a series of processes known as the Krebs cycle and oxidative phosphorylation. Together, these chemical processes yield nearly 40 molecules of energy-rich ATP for each molecule of glucose metabolized. Without adequate oxygen, the cells do not completely TIME IS CRITICAL! 0–1 min: cardiac irritability 0–4 min: brain damage not likely 4–6 min: brain damage possible 6–10 min: brain damage very likely More than 10 minutes: irreversible brain damage Figure 7 Cells need a constant supply of oxygen to survive. Some cells may be severely or permanently damaged after going 4 to 6 minutes without oxygen. 09153_ch06_5989.indd 77 77 convert glucose into energy, allowing lactic acid and other toxins to accumulate in the cell. This process, called anaerobic metabolism, cannot meet the metabolic demands of the cell. Although another intracellular process, glycolysis, also contributes to ATP production and does not require oxygen, it results in less ATP production and also produces lactic acid waste products and toxins. If this process is not corrected, the cells will eventually die. This phenomenon explains why adequate levels of perfusion (circulation of oxygenated blood within an organ or tissue) and external ventilation must be present for aerobic internal respiration to take place. However, while these elements are necessary for internal respiration, they do not guarantee that aerobic internal respiration will take place. Aerobic metabolism Metabolism that can proceed only in the presence of oxygen. Anaerobic metabolism Metabolism that takes place in the absence of oxygen; its principal product is lactic acid. Perfusion The circulation of oxygenated blood within an organ or tissue. When the mitochondria within each cell use oxygen to convert glucose to energy, carbon dioxide—the main waste product—accumulates in the cell. Carbon dioxide is then transported through the circulatory system and back to the lungs for exhalation. The process of ventilation, oxygenation, and respiration is an important concept for all EMTs to understand. The overall goal of these mechanisms is to deliver an adequate supply of oxygen to the cells of the body. When one of these processes fails or becomes disrupted, cells die. By recognizing the signs and symptoms of inadequate tissue perfusion and oxygenation, you can immediately intervene and correct a potentially life-threatening condition. Pathophysiology of Respiration Multiple conditions may inhibit the body’s ability to effectively deliver oxygen to the cells. In turn, disruption of pulmonary ventilation, oxygenation, and respiration will cause immediate effects on the body. As an EMT, it is important to recognize these conditions and correct them in a timely manner. Factors in the Nervous System Chemical factors are commonly involved in respiratory control issues because of the level of complexity of the human body. Complex series of chemical reactions are constantly taking place. For example, chemoreceptors monitor the levels of oxygen, carbon dioxide, hydrogen ions, and the pH of the cerebrospinal fluid (CSF), providing feedback on these parameters to the respiratory centers so that they can modify the rate and depth of breathing based on the body’s needs at any given time. Central chemoreceptors in the medulla respond quickly to slight elevations in carbon dioxide or a 8/17/11 8:06:21 PM 78 Emergency Medical Technician Transition Manual decrease in the pH of the CSF. The peripheral chemoreceptors, which are located in the carotid arteries and the aortic arch, are sensitive to decreased levels of oxygen in arterial blood as well as to low pH levels. Chemoreceptors Chemical factors that monitor the levels of oxygen, carbon dioxide, hydrogen ions, and the pH of the cerebrospinal fluid and provide feedback to the respiratory centers, which then modify the rate and depth of breathing based on the body’s needs at any given time. When serum carbon dioxide or hydrogen ion levels increase because of medical or traumatic conditions involving the respiratory system, chemoreceptors stimulate the dorsal and ventral respiratory groups in the medulla to increase the respiratory rate, thereby removing more carbon dioxide or acid from the body. The dorsal respiratory group is responsible for initiating inspiration based on the information received from the chemoreceptors. The ventral respiratory group is primarily responsible for motor control of the inspiratory and expiratory muscles. In addition, the dorsal respiratory group and the ventral respiratory group are affected by the apneustic center and the pneumotaxic (pontine) center of the pons. The apneustic center stimulates the dorsal respiratory group, resulting in longer, slower respirations. The pneumotaxic center helps shut off the dorsal respiratory group, resulting in shorter, faster respirations. If any element of this process is disrupted, then the respiratory process will be affected. Ventilation/Perfusion Ratio and Mismatch The lung has the functional role of placing ambient air in close proximity to circulating blood to permit gas exchange by simple diffusion. To accomplish this action, air and blood flow must be directed to the same place at the same time. In other words, ventilation and perfusion must be matched. A failure to match ventilation and perfusion, or V̇/Q̇ ratio mismatch, underlies most abnormalities in oxygen and carbon dioxide exchange. In most patients, the normal resting minute ventilation is approximately 6 L/min. Nearly one third of this volume fills dead space; thus resting alveolar ventilation is approximately 4 L/min. By comparison, pulmonary artery blood flow is approximately 5 L/min. These factors yield an overall ratio of ventilation to perfusion of 4⁄ 5 L/min or 0.8 L/min. Because neither ventilation nor perfusion is distributed equally, both are distributed to dependent regions at rest. However, the increase in gravity-dependent flow is more marked with perfusion (blood) than with ventilation (air). Hence, the ratio of ventilation to perfusion is highest at the apex of the lung and lowest at the base. When ventilation is compromised but perfusion continues, blood passes over some alveolar membranes without gas exchange taking place; as a consequence, not all alveoli are enriched with oxygen. This failure, in turn, results in a 09153_ch06_5989.indd 78 lack of oxygen diffusing across the membrane and into blood circulation. Along the same lines, carbon dioxide is also not able to diffuse across the membrane and is recirculated in the bloodstream. This condition results in a V̇/Q̇ ratio mismatch that could lead to severe hypoxemia if this problem is not recognized and treated. Similar problems can occur when perfusion across the alveolar membrane is disrupted. Even though the alveoli are filled with fresh oxygen, the disruption in the blood flow does not allow for optimal exchange in gases across the membrane. As a consequence, less oxygen absorption in the bloodstream and less carbon dioxide removal occur. This V̇/Q̇ ratio mismatch can also lead to hypoxemia, with immediate intervention being necessary to prevent further damage or death. Factors Affecting Pulmonary Ventilation Maintaining a patent airway is critical to the delivery of oxygen to the tissues of the body. Many intrinsic and extrinsic factors can potentially cause airway obstructions. Intrinsic factors are those internal to the body; external factors are those caused by external or environmental conditions. Intrinsic factors such as infections, allergic reactions, and unresponsiveness (tongue obstruction) can place significant restrictions on a person’s ability to maintain an open airway. In fact, swelling from infections and allergic reactions can be fatal if not aggressively managed with medications and possibly advanced airway maneuvers. The tongue is the most common airway obstruction in the unresponsive patient. This obstruction, while easily corrected, can result in hypoxia and hinder adequate tissue perfusion. Snoring respirations and the position of the head and neck are good indicators that the tongue may be obstructing the airway. Prompt correction of this obstruction is necessary to ensure adequate oxygenation. Some factors affecting pulmonary ventilation are not necessarily directly part of the respiratory system. Notably, the central and peripheral nervous systems play key roles in the regulation of breathing, such that interruptions to these systems can have a drastic effect on the ability to breathe efficiently. Medications that depress the central nervous system, for example, lower the respiratory rate and tidal volume, thereby decreasing the overall minute volume as well as alveolar ventilation. As a result, the amount of carbon dioxide in the respiratory and circulatory systems increases, leading to an overall increase of carbon dioxide levels in the bloodstream, a condition known as hypercarbia. Trauma to the head and spinal cord can also interrupt nervous control of ventilation, resulting in decreased respiratory function and even failure of the respiratory cycle. In addition, conditions such as muscular dystrophy can affect nervous control. Muscular dystrophy causes degeneration of muscle fibers, resulting in a gradual weakening of muscles, slowing motor development, and loss of muscle contractility. Curvature of the spine is also likely in patients with muscular dystrophy and can impair pulmonary function. 8/17/11 8:06:21 PM Chapter 6 Airway Management and Oxygenation Hypercarbia Increased carbon dioxide levels in the bloodstream. Patients with allergic reactions may not only suffer from a potential airway obstruction from swelling, but may also have a decrease in pulmonary ventilation from bronchoconstriction. As the bronchioles constrict, air is forced through smaller lumens, resulting in decreased ventilation. This condition is also found in patients suffering from various forms of COPD, such as asthma and emphysema. Extrinsic factors affecting pulmonary ventilation can include trauma or foreign body airway obstruction. Trauma to the airway or chest requires immediate evaluation and intervention. Blunt or penetrating trauma and burns can disrupt airflow through the trachea and into the lungs, quickly resulting in oxygenation deficiencies. In addition, trauma to the chest wall can cause structural damage to the thorax, leading to inadequate pulmonary ventilation. Swelling, punctures, and bruising have a tremendous effect on the ability to deliver oxygen to the alveoli and into the bloodstream. Proper airway management and high concentrations of oxygen are crucial to the outcome in these situations. Factors Affecting Respiration External elements in the environment can affect the overall process of respiration. For respiration to take place properly at the cellular level, both oxygenation and perfusion need to function efficiently. External Factors Adequate respiration requires proper ventilation and oxygenation. External factors such as atmospheric pressure and the partial pressure of oxygen in the ambient air play a key role in the overall process of respiration. At high altitudes, the percentage of oxygen remains the same, but the partial pressure decreases because the total atmospheric pressure decreases. The low partial pressure of oxygen can make it difficult (or impossible) to adequately oxygenate tissue, interrupting internal respiration. In addition, closed environments, such as mines and trenches, may have lower levels of ambient oxygen, resulting in poor oxygenation and respiration. Carbon monoxide, along with other toxic and poisonous gases, displaces oxygen in the environment and makes proper oxygenation and respiration difficult. Carbon monoxide, in particular, has a much greater affinity for hemoglobin than oxygen (250 times more), so its presence (eg, in carbon monoxide poisoning) does not allow for proper transport of oxygen to tissues. Internal Factors Conditions that reduce the surface area available for gas exchange also decrease the body’s oxygen supply, leading to inadequate tissue perfusion. Medical conditions such as pneumonia, pulmonary edema, and COPD/emphysema may also result in a disturbance of cellular metabolism. These conditions decrease the surface area of the alveoli either by 09153_ch06_5989.indd 79 79 damaging the alveoli or by permitting an accumulation of fluid in the lungs. Nonfunctional alveoli inhibit the diffusion of oxygen and carbon dioxide. As a result, blood entering the lungs from the right side of the heart bypasses the alveoli and returns to the left side of the heart in an unoxygenated state, a condition called intrapulmonary shunting. Drowning victims and patients with pulmonary edema have fluid in the alveoli. This accumulation of fluid prevents adequate gas exchange at the alveolar membrane, resulting in decreased oxygenation and respiration. In addition, exposure to certain environmental conditions, such as high altitudes, or occupational hazards, such as epoxy resins, over time can result in fluid accumulation or other abnormal conditions, causing overall decrease in respiration. These conditions can interrupt the process of aerobic respiration at the cellular level, leading to anaerobic respiration and lactic acid accumulation. Other conditions affecting cells of the body include hypoxia, hypoglycemia (low blood glucose), and infection. As oxygen and glucose levels decrease, the body becomes unable to maintain a homeostatic balance with regard to energy production. At this point, the energy production cannot meet the needs of the body, and cellular death is likely if the condition is not corrected. Infection also increases the metabolic needs of the body and disrupts homeostasis. If this problem is not corrected, the cells will die as well. Circulatory Compromise For respiration to take place, the circulatory system must function efficiently to deliver oxygen to the tissues of the body. When this system becomes compromised, the perfusion of oxygen is not sufficient to meet the oxygen demands of the tissues. Obstruction of blood flow to individual cells and tissue is typically related to traumatic injuries, including pulmonary embolism, simple (tension) pneumothorax, open pneumothorax (sucking chest wound), hemothorax, and hemopneumothorax. All of these conditions limit the ability of gas exchange to occur at the tissue level as a result of their effects on the respiratory and circulatory systems. In addition, conditions such as heart failure and cardiac tamponade inhibit the ability of the heart to effectively pump oxygenated blood to the tissues. Blood loss and anemia (a deficiency of red blood cells) result in a decreased ability of blood to carry oxygen. Without sufficient circulating red blood cells, the hemoglobin molecules do not have enough sites for binding. When the body is in a state of shock, oxygen is not delivered to the cells efficiently. Hypovolemic shock consists of an abnormal decrease in blood volume that causes inadequate oxygen delivery to body organs. In contrast, shock caused by vasodilation is not determined by the amount of circulating blood, but rather by the size of the blood vessels. As the diameter of the blood vessels increases, the blood pressure in the circulatory system decreases. As the systemic blood 8/17/11 8:06:22 PM 80 Emergency Medical Technician Transition Manual pressure falls, oxygen is not delivered to the tissues in an effective manner. Both forms of shock result in poor tissue perfusion that leads to anaerobic metabolism. Any patient suspected of being in shock should be treated aggressively to prevent further interruptions to tissue perfusion. Shock is discussed in more detail in the Shock and BLS Resuscitation chapter. Patient Assessment Recognizing Adequate Breathing Under normal circumstances, breathing should be a smooth flow of air moving into and out of the lungs. As a general rule, unless you are directly assessing the patient’s airway, you should not be able to see or hear a patient breathe. Signs of normal (adequate) breathing for adult patients are as follows: ■■ A normal rate of respirations (between 12 and 20 breaths/min) ■■ A regular pattern of inhalation and exhalation ■■ Clear and equal lung sounds on both sides of the chest (bilateral) ■■ Regular and equal chest rise (chest expansion) and fall ■■ Adequate depth of respirations (tidal volume) ■■ Skin that is pink, warm, and dry sory muscles include the neck muscles (sternocleidomastoid), the chest pectoralis major muscles, and the abdominal muscles Figure 8 . These muscles are not used during normal breathing. Signs of inadequate breathing in adult patients are as follows: ■■ Respiratory rate less than 8 breaths/min or greater than 24 breaths/min with poor tissue perfusion ■■ Irregular rhythm, such as the patient taking a series of deep breaths followed by periods of apnea ■■ Diminished, absent, or noisy auscultated breath sounds ■■ Reduced flow of expired air at the nose and mouth ■■ Unequal or inadequate chest expansion, resulting in reduced tidal volume ■■ Increased effort of breathing—use of accessory muscles ■■ Shallow depth (reduced tidal volume) ■■ Skin that is pale, cyanotic (blue), cool, or moist (clammy) ■■ Skin pulling in around the ribs or above the clavicles during inspiration (retractions) When you are assessing a patient with a potential airway compromise, consider the external environment. Conditions Recognizing Abnormal Breathing An adult who is awake, alert, and talking to you generally has no immediate airway or breathing problems. Even so, you should always have supplemental oxygen and a bag-mask device or pocket mask close at hand to assist with breathing if its use becomes necessary. A normal breathing rate for an adult is 12 to 20 breaths/min table 2 . The adult patient who is breathing more slowly than normal (fewer than 12 breaths/min) should be evaluated for inadequate breathing by assessing the depth of his or her respirations. A patient with a shallow depth of breathing (reduced tidal volume) may require assisted ventilations, even if his or her respiratory rate is within normal limits. A patient with inadequate breathing may appear to be working hard to breathe. This type of breathing pattern is termed labored breathing. It requires effort and, especially in children, may involve the use of accessory muscles. AccesTable 2 Normal Respiratory Rate Ranges Adults 12 to 20 breaths/min Children 15 to 30 breaths/min Infants 25 to 50 breaths/min Note: These ranges are those identified in the NHTSA 2009 National EMS Education Standards. Ranges presented in other courses may vary. 09153_ch06_5989.indd 80 Figure 8 The accessory muscles of breathing are used when a patient is having difficulty breathing, but not during normal breathing. Notice this patient is in the tripod position. 8/17/11 8:06:23 PM Chapter 6 Airway Management and Oxygenation such as high altitude and enclosed spaces alter the partial pressure of oxygen in the environment, making the process of oxygenation difficult for the patient. In addition, poisonous gases, such as carbon monoxide, displace oxygen in the environment and alter the overall metabolism of the patient. It is important to recognize these potential situations and take them into consideration when deciding on appropriate treatment for the patient. Assess for agonal respirations—occasional, gasping breaths that may appear after a patient’s heart has stopped beating. They occur when the respiratory center in the brain continues to send signals to the respiratory muscles. These respirations do not provide adequate oxygen because they are infrequent, gasping respiratory efforts. In patients with agonal respirations, artificial ventilation and, most likely, chest compressions will be necessary. Some patients may have irregular respiratory breathing patterns that are related to a specific condition. For example, Cheyne-Stokes respirations are often seen in patients with stroke and patients with serious head injuries Figure 9 . Cheyne-Stokes respirations constitute an irregular respiratory pattern in which the patient breathes with an increasing rate and depth of respirations that is followed by a period of apnea, or lack of spontaneous breathing, followed again by a pattern of increasing rate and depth of respiration. Serious head injuries may also cause changes in the normal respiratory rate and pattern of breathing. The result may be irregular, ineffective respirations that may or may not have an identifiable pattern (ataxic respirations). Patients experiencing a metabolic or toxic disorder may display other irregular respiratory patterns such as Kussmaul respirations—that is, deep, gasping respirations that are commonly seen in patients with metabolic acidosis. Although rapid breathing is a compensatory mechanism to help patients in respiratory distress, some patients are so ill that their body is not able to compensate for the insufficiency of their respiratory effort. Such patients may look like they are compensating, but no clinical improvement will be noticeable. It is essential that you remain vigilant when monitoring a patient in respiratory distress because the individual’s condition may decline rapidly. Cheyne-Stokes breathing 1 min 1 min Inspiration/expiration Figure 9 Cheyne-Stokes breathing shows irregular respirations followed by a period of apnea. 09153_ch06_5989.indd 81 81 Transition Tip Patients with inadequate breathing have inadequate minute volume and need to be treated immediately. This condition is most easily recognized in patients who are unable to speak in complete sentences when at rest (one- or two-word dyspnea) and in those who have a fast or slow respiratory rate; both of these conditions may result in a reduction in tidal volume. Emergency medical care includes airway management, supplemental oxygen, and ventilatory support. Assessment of Respiration As described earlier, respiration is the actual exchange of oxygen and carbon dioxide at the tissue level. Even though a patient may be ventilating appropriately, the process of respiration may be compromised. Therefore, assessing for signs of adequate and inadequate respiration in patients is essential. A patient’s level of consciousness and skin color are excellent indicators of respiration. During normal respiration, oxygen and carbon dioxide diffuse in and out of tissues and allow aerobic metabolism to take place. During assessment of the brain and skin tissues, it will be apparent if the patient has adequate oxygen levels reaching these areas. A patient presenting with an altered level of consciousness may not have adequate oxygen levels reaching the brain; this lack of oxygen can cause rapid changes in the patient’s mental status. Therefore, when treating patients with an altered mental status, always consider the possibility that they might not be getting adequate oxygen levels to their brain and that you might need to address the possible underlying causes. Keep in mind, however, that you must determine the baseline mental status on the patient. Some patients naturally have an abnormal mental status because of a previous medical condition. Ask family members to describe the patient’s normal mental condition for use as a comparison state. Just as an altered level of consciousness is indicative of inadequate respiration, the same is true for patients with poor skin color. When oxygen fails to reach the skin tissue of the body, because of either a lack of perfusion or poor oxygenation, the color of the skin changes to reflect the poor level of oxygenation. Pale skin and mucous membranes, commonly referred to as pallor, are typically associated with poor perfusion caused by illness or shock. As this condition worsens, cyanosis becomes noticeable first peripherally, in the fingertips, and then centrally, in the mucous membranes and around the lips Figure 10 . Eventually, if the poor perfusion or oxygenation is not corrected, anaerobic metabolism will take place. It could cause the skin to become marked with blotches of different colors, commonly referred to as mottling. Although a patient’s baseline mental status and the color of the skin and mucous membranes represent good 8/17/11 8:06:24 PM 82 Emergency Medical Technician Transition Manual indicators of respiration, EMTs should also consider proper oxygenation when assessing patients. As mentioned earlier, oxygenation is the process of loading oxygen molecules onto hemoglobin molecules in the bloodstream. Several methods can be used to assess proper oxygenation, including assessing skin color and mental status and the more recent use of pulse oximetry. Oxygen saturation (Spo2) is the measurement of the percentage of hemoglobin molecules that are bound in arterial blood. Because hemoglobin delivers 97% of the oxygen delivered to the body’s tissues, the oxygen saturation rate is an excellent indication of the amount of oxygen available to the end organs. In the past few years, the pulse oximeter has become standard equipment in the treatment of emergency patients. This device provides a rapid, reliable, noninvasive, realtime indication of respiratory efficiency. Although its results should not be used without conducting an overall clinical assessment of the patient, careful use of the pulse oximeter provides valuable information about a patient’s oxygenation status. This device can be used both to assess the adequacy of oxygenation during positive-pressure ventilation and to assess the overall impact of interventions on your patient. A pulse oximeter measures the percentage of hemoglobin saturation. Under normal conditions, the Spo2 should be 95% to 100% while a person is breathing room air. Although no definitive threshold for normal values exists, an Spo2 of less than 96% in a nonsmoker may indicate hypoxemia. A value between 91% and 94% indicates mild hypoxemia; 80% to 90% indicates significant hypoxemia; and less than 85% indicates profound hypoxemia. Oxygen delivery should be titrated to a minimum Spo2 of 95% unless the patient has a chronic condition causing perpetually low oxygen saturations, without signs of respiratory distress. Follow local protocols. Pulse oximeters are highly reliable in Spo2 readings above 85%; readings of less than 85%, while considered less reliable, certainly indicate profound hypoxemia. Pulse oximetry is considered a routine vital sign and can be used as part of any patient assessment. Although there are no true contraindications to use of pulse oximetry, EMTs must be aware of the limitations associated with this device. In patients with significant vasoconstriction or very low perfusion states (including cardiac arrest), there may not be enough peripheral perfusion to be detected by the sensor. In these cases, you should move the sensor to a more central location (eg, the bridge of the nose or an ear lobe). Always consult the manufacturer’s guidelines for proper placement and troubleshooting of these devices. An inaccurate pulse oximetry reading may be caused by any of the following conditions: ■■ Hypovolemia ■■ Anemia ■■ Severe peripheral vasoconstriction (chronic hypoxia, smoking, or hypothermia) ■■ Time delay in detecting respiratory insufficiency ■■ Dark or metallic nail polish ■■ Dirty fingers ■■ Carbon monoxide poisoning Transition Tip When carbon monoxide is present in the inspired gas, it displaces oxygen from the hemoglobin. Pulse oximetry, which measures hemoglobin saturation, is unable to distinguish between oxygen saturation and carbon monoxide saturation. Thus, in cases of carbon monoxide poisoning, even though the circulating oxygen levels are poor, the Spo2 reading will be normal. Transition Tip The pulse oximeter is a valuable adjunct to aid in decision making, but it is not a replacement for a complete assessment. For many different reasons, the pulse oximeter may give falsely high or low readings. Supplemental Oxygen Figure 10 Skin color can provide an early, fast indication of several disease processes. This photo shows cyanosis. 09153_ch06_5989.indd 82 In hypoxia, not enough oxygen is getting to the tissues and cells of the body. Thus all patients who are hypoxic should receive supplemental oxygen. Some tissues and organs, such as the heart, central nervous system, lungs, kidneys, and liver, require a constant supply of oxygen to function normally. Supplemental oxygen should be administered to any patient with potential hypoxia, regardless of his or her clinical appearance. An ongoing debate has focused on how much supplemental oxygen a patient requires. In some EMS systems, immediate high-flow oxygen is given to any trauma patient. Other systems require a full assessment prior to 8/17/11 8:06:24 PM Chapter 6 Airway Management and Oxygenation making a determination of the patient’s oxygen needs. Make sure to know your local protocols regarding oxygen administration. 83 need to be kept upright and have special requirements for filling, large-volume storage, and cylinder transfer. Oxygen-Delivery Equipment Transition Tip Never withhold oxygen from any patient who might benefit from it, especially if you must assist ventilations. When you are ventilating any patient in cardiac or respiratory arrest, always use high-concentration supplemental oxygen. Traditionally, the oxygen-delivery equipment used in the field has been limited to nonrebreathing masks, bag-mask devices, and nasal cannulas. Today, however, some other devices are available to the EMT, including the partial rebreathing face mask, Venturi mask, and tracheostomy mask. The use of humidification is also new to the EMT. Nonrebreathing Masks Oxygen Cylinders Oxygen has traditionally been stored in seamless steel or aluminum cylinders of various sizes Figure 11 . As an EMT, you should be familiar with the various sizes of cylinders, safety considerations, and operating procedures when providing supplemental oxygen using an oxygen cylinder. The nonrebreathing mask is the preferred way of giving oxygen in the prehospital setting to patients who are breathing adequately but are suspected of having or showing signs of hypoxia Figure 12 . With a good mask-to-face seal, this device is capable of providing as much as 90% inspired oxygen at a flow rate of 10 to 15 L/min. Liquid Oxygen Transition Tip Liquid oxygen is oxygen that has been cooled to a liquid state. When warmed, it converts to a gaseous state. Liquid oxygen is becoming more commonly used as an alternative to compressed gas oxygen. Liquid oxygen containers tend to be more expensive than compressed oxygen tanks; however, the containers hold a large volume of oxygen and do not need to be filled as often. Liquid oxygen units also weigh less than aluminum or steel tanks. For these reasons, many people who receive long-term oxygen therapy use liquid oxygen units. Unfortunately, liquid oxygen tanks generally Ensure that the reservoir bag of the nonrebreathing mask is full before you place the mask on the patient. If oxygen therapy is discontinued, remove the mask from the patient’s face. Leaving the mask in place, while oxygen is not flowing, allows the patient to rebreathe exhaled carbon dioxide. Figure 11 Oxygen tanks are made of steel or aluminum and come in various sizes. 09153_ch06_5989.indd 83 Nasal Cannulas A nasal cannula delivers oxygen through two small, tubelike prongs that fit into the patient’s nostrils Figure 13 . This device can provide 24% to 44% inspired oxygen at a flow rate of 1 to 6 L/min. For the comfort of your patient, flow rates greater than 6 L/min are not recommended with the nasal cannula. Figure 12 The nonrebreathing mask contains flapper valve ports at the cheek areas of the mask to prevent the patient from rebreathing exhaled gases. 8/17/11 8:06:26 PM 84 Emergency Medical Technician Transition Manual Figure 13 The nasal cannula delivers oxygen directly through the nostrils. Transition Tip The nasal cannula delivers dry oxygen directly into the nostrils, which, over prolonged periods, can cause dryness or irritate the mucous membrane lining of the nose. For this reason, you should consider the use of humidification during prolonged transport times. A nasal cannula is used for patients who simply cannot tolerate a nonrebreathing or partial rebreathing mask, and for patients who are not critical but may benefit from lower concentrations of oxygen. It is also useful when transporting a noncritical patient who is on home oxygen via a nasal cannula. Partial Rebreathing Masks The partial rebreathing mask is similar to a nonrebreathing mask except that it lacks a one-way valve between the mask and the reservoir Figure 14 . Consequently, patients rebreathe a small amount of their exhaled air. This arrangement has some benefit when you want to increase Figure 15 The Venturi mask. the patient’s partial pressure of carbon dioxide, making this device the ideal mask for patients who may develop hyperventilation syndrome. The oxygen enriches the air mixture and delivers a gas mixture consisting of approximately 80% to 90% oxygen and 2% to 3% carbon dioxide. You can easily convert a nonrebreathing mask to a partial rebreathing mask by removing the one-way valve between the mask and the reservoir bag. Venturi Masks A Venturi mask has a number of attachments that enable you to vary the percentage of oxygen delivered to the patient while a constant flow is maintained from the regulator Figure 15 . This delivery is accomplished by exploiting the Venturi principle, which causes air to be drawn into the flow of oxygen as it passes a hole in the line. The Venturi mask is a medium-flow device that delivers 24% to 40% oxygen, depending on the manufacturer’s settings. The main advantage of the Venturi mask is its fine adjustment capabilities, which has benefits in the long-term management of physiologically stable patients. When it is necessary to adjust the oxygen concentration in an emergency, the health care provider typically changes either the flow rate or the delivery device. Tracheostomy Masks Figure 14 A partial rebreathing mask. 09153_ch06_5989.indd 84 Patients with tracheostomies do not breathe through their mouth and nose. As such, a face mask or nasal cannula cannot be used to provide supplemental oxygen to these individuals. Tracheostomy masks are specially designed to cover the tracheostomy hole, with a strap that goes around the neck. These masks are usually available in intensive care units, where many patients have tracheostomies, but may not be available in an emergency setting. If you do not have a tracheostomy mask, you can improvise by placing a face mask over the stoma. Even though the mask is shaped to fit the face, you can usually get an adequate fit over the patient’s neck by adjusting the strap Figure 16 . 8/17/11 8:06:28 PM Chapter 6 Airway Management and Oxygenation 85 tidal volume) are typically unable to speak in complete sentences without becoming winded. These patients, in addition to those with an irregular breathing pattern, may require artificial ventilation to help them maintain adequate minute volume. Transition Tip Figure 16 If a tracheostomy mask is not available, use a face mask instead. Humidification Although dry oxygen is not considered harmful for shortterm use, when longer transport times are expected, the use of humidified oxygen may be beneficial to the patient to prevent drying of the nasal mucosa. An oxygen humidifier consists of a small bottle of water through which the oxygen leaving the cylinder becomes moisturized before it reaches the patient Figure 17 . Because the humidifier must be kept in an upright position, however, it is practical only for the fixed oxygen unit in the ambulance. Assisted and Artificial Ventilation A patient who is not breathing needs artificial ventilation with 100% supplemental oxygen. Assisted and artificial ventilation are probably the most important skills in EMS—at any level. Too often emphasis is placed on advanced airway techniques, making the basic airway maneuvers seem ineffective. This perception could not be further from the truth: Basic airway and ventilation techniques are extremely effective when administered appropriately. Mastery of these techniques at the EMT level is imperative. Figure 17 Giving humidified Patients who are oxygen may be preferred with long breathing inadequately transport times. However, this type of (too rapidly or too oxygen delivery system is not universlowly with reduced sally available in all EMS systems. 09153_ch06_5989.indd 85 Shallow breathing can be just as dangerous as very slow breathing. Fast, shallow breathing moves air primarily in the larger airway passages (dead air space) and does not allow for adequate exchange of air and carbon dioxide in the alveoli. Patients with inadequate breathing require assisted ventilations with some form of positive-pressure ventilation. Remember to follow standard precautions when managing the patient’s airway. Assisting Ventilation in Respiratory Distress/Failure A patient exhibiting signs of severe respiratory distress or respiratory failure requires immediate intervention. Two treatment options are available in these situations: assisted ventilation via a bag-mask device and continuous positive airway pressure (CPAP). The purpose of assisted ventilations is to improve the overall oxygenation and ventilatory status of the patient. Patients who require assisted ventilation are no longer able to maintain adequate oxygen levels for the body and need intervention to prevent further hypoxia. Indicators of inadequate ventilation include altered mental status and inadequate minute volume. In addition, excessive accessory muscle use and fatigue from labored breathing are signs of potential respiratory failure. table 3 lists the recommended ventilation rates for apneic patients with a pulse. Follow these steps to assist a patient with ventilations using a bag-mask device: 1. Explain the procedure to the patient. 2.Place the mask over the patient’s nose and mouth. 3.Squeeze the bag each time the patient breathes, maintaining the same rate as the patient. 4.After the initial 5 to 10 breaths, slowly adjust the rate and deliver an appropriate tidal volume. Table 3 Ventilation Rates for an Apneic Patient With a Pulse Adult 1 breath every 5 seconds Child 1 breath every 3 seconds Infant 1 breath every 3 seconds 8/17/11 8:06:29 PM 86 Emergency Medical Technician Transition Manual in the treatment of respiratory distress associated with obstructive pulmonary disease and acute pulmonary edema. Its use has negated the need for advanced airway devices such as the endotracheal tube, and decreased morbidity and mortality associated with conditions needing such intubation. CPAP is not a new skill to the EMT and, therefore, is not discussed further in this text. Artificial Ventilation Figure 18 Many people who have been diagnosed with obstructive sleep apnea wear a CPAP device at night to maintain their airway while they sleep. 5.Adjust the rate and tidal volume to maintain an adequate minute volume. Continuous Positive Airway Pressure Continuous positive airway pressure is a noninvasive means of providing ventilatory support to patients who are experiencing respiratory distress in which their own compensatory mechanisms are not sufficient to keep up with their oxygen demand Figure 18 . Although most patients improve after the application of CPAP, it is important to remember that this technique merely treats the symptoms; it does not necessarily address the underlying pathology. Over the past several years, the use of CPAP in the prehospital environment has proved to be an excellent adjunct Patients who are in respiratory arrest need immediate intervention. Without it, they will die. Devices for providing artificial ventilation include the pocket face mask for performing mouth-to-mask ventilations, the bag-mask device, and the manually triggered ventilation device. Normal Ventilation Versus Positive-Pressure Ventilation Although artificial ventilations are necessary to sustain life, they are not the same as normal breaths. As discussed earlier, the act of air moving in and out the lungs is based on pressure changes within the thoracic cavity. During normal ventilation, the diaphragm contracts and negative pressure is generated in the chest cavity. In response, air is essentially sucked into the chest from the trachea in an attempt to equalize the pressure in the chest with the atmospheric pressure. In contrast, positive-pressure ventilation generated by a device, such as a bag-mask device, forces air into the chest cavity from the external environment, rather than based on pressure changes. This difference between normal ventilation and positive-pressure ventilation can create some challenges for the EMT table 4 . Table 4 Normal Ventilation Versus Positive-Pressure Ventilation Normal Ventilation Positive-Pressure Ventilation Air movement Air is sucked into the lungs due to Air is forced into the lungs through a means of mechanical the negative intrathoracic pressure ventilation. created when the diaphragm contracts. Blood movement Normal breathing allows blood to naturally be pulled back to the heart. Intrathoracic pressure is increased, not allowing blood to be adequately pulled back to the heart. This causes a reduction in the amount of blood pumped by the heart. Airway wall pressure Not affected during normal breathing. More volume is required to have the same effects as normal breathing. As a result, the walls are pushed out of their normal anatomic shape. Esophageal opening pressure Not affected during normal breathing. Air is forced into the stomach, causing gastric distention that could result in vomiting and aspiration. Overventilation Overventilation is not typical of normal breathing. Forcing the volume and rate results in increased intrathoracic pressure, gastric distention, and decrease in cardiac output (hypotension). 09153_ch06_5989.indd 86 8/17/11 8:06:30 PM Chapter 6 Airway Management and Oxygenation The physical act of the chest wall expanding and retracting during breathing serves to aid the circulatory system in returning blood back to the heart. During normal ventilation, the chest wall movement works similar to a pump. The pressure changes in the thoracic cavity help draw venous return back to the heart. When positive-pressure ventilation is initiated, however, more air is needed to achieve the same oxygenation and ventilatory effects that occur during normal breathing. This increase in airway wall pressure pushes the walls of the chest cavity out of their normal anatomic shape. As a result, the overall intrathoracic pressure within the chest cavity increases. This increased pressure, in turn, causes a decrease in blood flow, resulting in poor venous return to the heart and a reduction in the amount of blood pumped out of the heart. Cardiac output (CO) is a function of stroke volume and heart rate: Cardiac Output (CO) = Stroke Volume ¥ Heart Rate Cardiac output The amount of blood ejected by the left ventricle in 1 minute. Stroke volume is the amount of blood ejected by the ventricle in one cardiac cycle or one beat. The heart rate is assessed by taking the pulse for 1 minute. The CO is the amount of blood ejected by the left ventricle in 1 minute. Stroke volume The volume of blood pumped forward with each ventricular contraction. Transition Tip To prevent a drop in cardiac output, it is imperative that the EMT regulate the rate and volume of artificial ventilations. 87 Figure 19 A manually triggered ventilation device can provide as much as 100% oxygen. Manually Triggered Ventilation Devices Another method of providing artificial ventilation is with a manually triggered ventilation device Figure 19 . Such devices—which are also known as flow-restricted, oxygenpowered ventilation devices or demand valves—have been widely available for use in EMS systems for several years, although they have not been widely used. The major advantage associated with this device is that it allows a single rescuer to use both hands to maintain a maskto-face seal while providing positive-pressure ventilation. It also reduces the rescuer fatigue associated with using a bagmask device on extended transports. Nevertheless, recent findings suggest that manually triggered ventilation devices are associated with difficulty in maintaining adequate ventilation without assistance and should not be used routinely because of the high incidence of gastric distention and possible damage to structures within the chest cavity. Another disadvantage is that a special unit and additional training are required when using the manually triggered ventilation device on infants and children. Transition Tip Another difference between normal ventilation and positive-pressure ventilation relates to the control of airflow. When a person breathes normally, air enters the trachea, but generally not the esophagus. In contrast, the force generated from positive-pressure ventilation allows air to enter both the trachea and the esophagus. Ventilations that are too forceful can lead to gastric distention (excessive air in the stomach). The manually triggered ventilation device should not be used on patients with chronic obstructive pulmonary disease or with suspected cervical spine or chest injuries. This device is typically used only on adult patients. Additional training is necessary prior to using the device on pediatric patients. illustrates the sequence for ventilating an apneic patient using the manually triggered ventilation device: 1 Choose the proper mask size to seat the mask from the bridge of the nose to the chin. (Step 1) skill drill 1 Transition Tip Mouth-to-mouth, mouth-to-mask, and bag-mask ventilations are all skills that you should have mastered by now. 09153_ch06_5989.indd 87 2 Position the mask on the patient’s face by the most appropriate method. (Step 2) 8/17/11 8:06:31 PM 88 Emergency Medical Technician Transition Manual 3 Open the patient’s airway and hold the mask in place with one hand, maintaining an adequate mask-toface seal. (Step 3) 4 5 Press the ventilation button until you see visible chest rise. (Step 4) Allow the patient to exhale passively. (Step 5) Skill Drill 1 Manually Triggered Ventilation Device for Apneic Patients 1 3 Open the patient’s airway and hold the mask with 5 Allow the patient to exhale passively. Choose the proper mask size to seat the mask from the bridge of the nose to the chin. one hand. 09153_ch06_5989.indd 88 2 Position the mask on the patient’s face by the most 4 Press the ventilation button until you see visible appropriate method. chest rise. 8/17/11 8:06:33 PM Chapter 6 Airway Management and Oxygenation 1 skill drill 2 shows the steps for administering supplemental oxygen to a spontaneously breathing patient with the manually triggered ventilation device: Prepare your equipment by attaching the appropri- ate-sized mask to the manually triggered ventilation device and ensuring that it is connected to an oxygen source. (Step 1) Transition Tip The Sellick maneuver, also known as cricoid pressure, has been used to inhibit the flow of air into the stomach (thereby reducing gastric distention) and to reduce the chance of aspiration by helping block the regurgitation of gastric contents from the esophagus. It has also been used to improve visualization of the vocal cords or positioning of the lighted stylet during intubation. In this maneuver, an EMT applies cricoid pressure on the patient by placing the thumb and index finger on either side of the cricoid cartilage (located at the inferior border of the larynx) and pressing down. According to several studies cited in the 2010 American Heart Association Guidelines, cricoid pressure may actually impede ventilation and not completely prevent aspiration. For this reason, the procedure is generally not recommended. Be sure to follow your local protocol regarding the use of the Sellick maneuver. 89 2 Whenever possible, have the patient hold the mask to his or her own face to maintain a good seal. (Step 2) 3 When the patient inhales, the negative pressure cre- ated will trigger the valve within the manually triggered ventilation device and deliver 100% oxygen. Automatic Transport Ventilator/Resuscitator The automatic transport ventilator (ATV) is essentially a manually triggered ventilation device attached to a control box that allows the user to set the variables of ventilation Figure 20 . Although an ATV lacks the sophisticated control of a hospital ventilator, it frees the EMT to perform other tasks, such as maintaining a mask seal or ensuring continued patency of the airway. You can even perform non–airwayrelated tasks if the patient has an advanced airway in place and is being ventilated with the ATV. However, even though an ATV is helpful to an EMT, a bag-mask device and mask should always be prepared and ready for use should a malfunction occur with the ATV. Skill Drill 2 Manually Triggered Ventilation for Conscious, Spontaneously Breathing Patients 1 Prepare your equipment. 09153_ch06_5989.indd 89 2 Whenever possible, have the patient hold the mask to his or her own face to maintain a good seal. 3 When the patient inhales, the negative pressure created will trigger the valve within the manually triggered ventilation device and deliver 100% oxygen. 8/17/11 8:06:36 PM 90 Emergency Medical Technician Transition Manual Figure 20 Automatic transport ventilator (ATV). 09153_ch06_5989.indd 90 Like the manually triggered ventilation device, the ATV is generally oxygen powered, although some models may require an external power source. This device generally consumes 5 L/min of oxygen; by comparison, a bag-mask device requires 15 to 25 L/min of oxygen. In addition, just like the manually triggered ventilation device, the ATV includes a pressure relief valve, which can lead to hypoventilation in patients with poor lung compliance, increased airway resistance, or airway obstruction. Compliance is the ability of the alveoli to expand when air is drawn in during inhalation; poor lung compliance is the inability of the alveoli to fully expand during inhalation. Although use of an ATV potentially frees the EMT to perform other tasks, constant reassessment of the patient is necessary. Barotrauma is a common complication associated with manually triggered ventilation devices and the ATV. In addition, the EMT needs to assess for full chest recoil when using an ATV. This step is not only essential with patients in respiratory arrest, but also with patients in cardiac arrest receiving chest compressions. 8/17/11 8:06:37 PM PREP kit Ready for Review ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■■ 91 To fully understand the respiratory conditions a patient may have, the EMT must understand the anatomy and physiology of the respiratory system in more detail. Understanding the pathophysiology of ventilation, oxygenation, and respiration will also help the EMT better understand the signs and symptoms associated with certain conditions as well as management techniques for caring for a patient presenting with such conditions. The respiratory system comprises all the structures of the body that contribute to the process of breathing, including the nose, mouth, throat, larynx, trachea, bronchi, and bronchioles. All of these structures are all air passages or airways. The respiratory system also includes the lungs, the diaphragm, the muscles of the chest wall, and accessory muscles of breathing. The respiratory and cardiovascular systems work together to ensure that a constant supply of oxygen and nutrients is delivered to every cell in the body and that carbon dioxide and waste products are removed from every cell. During inhalation, oxygen moves from the atmosphere into the lungs, then passes from the air sacs in the lungs (alveoli) into the capillaries to oxygenate the blood. At the same time, carbon dioxide produced by cells in the tissues of the body moves from the blood into the alveoli through a process called diffusion. The blood, once enriched with oxygen, travels through the body by the pumping action of the heart. The carbon dioxide ultimately leaves the body during exhalation. In the circulatory system, the heart pumps blood to the tissues of the body through a series of arteries and veins. Arteries carry oxygenated blood away from the heart and branch into arterioles and capillaries. Veins carry deoxygenated blood to the heart. Although the terms are often used interchangeably, ventilation, oxygenation, and respiration are actually three distinct processes. •• Ventilation is the physical act of moving air into and out of the lungs. •• Oxygenation is the process of loading oxygen molecules into hemoglobin molecules in the bloodstream. •• Respiration is the actual exchange of oxygen and carbon dioxide in the alveoli as well as the tissues of the body. Cells take energy from nutrients through a series of chemical processes called metabolism or cellular respiration. During metabolism, each cell combines nutrients (such as sugar) and oxygen and produces energy and waste products (primarily water and carbon dioxide). Each cell in the body requires a continuous supply of oxygen and a regular means of disposing of waste (eg, carbon Emergency Medical Technician Transition Manual 09153_ch06_5989.indd 91 ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■■ dioxide). The body provides for these requirements through respiration. Factors that may affect pulmonary ventilation include airway obstruction, swelling from infection or allergic reaction, bronchoconstriction, medications that may depress the central nervous system leading to a lower respiratory rate and tidal volume, trauma, and muscular dystrophy. External factors that may affect respiration include the atmospheric pressure and the partial pressure of oxygen in the ambient air. Internal factors include pneumonia, pulmonary edema, COPD/emphysema, hypoxia, hypoglycemia, and infection. Adequate breathing for an adult is equivalent to a rate of 12 to 20 breaths/min and includes a regular pattern of inhalation and exhalation, adequate depth, bilaterally clear and equal lung sounds, and regular and equal chest rise and fall. Inadequate breathing for an adult is defined as fewer than 12 breaths/min or more than 20 breaths/min and includes shallow depth (reduced tidal volume), an irregular pattern of inhalation and exhalation, and breath sounds that are diminished, absent, or noisy. Even though a patient may be ventilating appropriately, the process of respiration may be compromised. In such a case, the EMT must assess the patient’s skin color and mental status, and monitor oxygen levels using a pulse oximeter. Patients with inadequate breathing must be treated immediately. Emergency medical care includes airway management, supplemental oxygen, and ventilatory support. Oxygen-delivery devices include nonrebreathing masks, nasal cannulas, partial rebreathing masks, Venturi masks, tracheostomy masks, and humidified oxygen. A patient exhibiting signs of severe respiratory distress or respiratory failure requires assisted ventilation via a bag-mask device or CPAP. Artificial ventilation devices include the pocket face mask for performing mouth-to-mask ventilations, the bag-mask device, the manually triggered ventilation device, and the automatic transport ventilator. An EMT should know the difference between normal ventilation and artificial ventilation. During normal ventilation, the diaphragm essentially sucks air into the chest from the trachea in an attempt to equalize the pressure in the chest with the atmospheric pressure. Positive-pressure ventilation is generated by a device, such as a bag-mask device, that forces air into the chest cavity from the external environment, rather than based on pressure changes. The use of cricoid pressure (Sellick maneuver) during artificial ventilations is no longer recommended. Chapter 6 Airway Management and Oxygenation 91 8/17/11 8:06:38 PM PREP kit Case Study You arrive at a local nursing home, where you find an 84-year-old woman in respiratory distress. The nursing staff placed the patient on 4 L/min of oxygen via nasal cannula prior to your arrival. The nursing staff tells you that the patient has been complaining of trouble breathing over the past few days, with the difficulty becoming worse at night. They report that the patient has been sleeping in a recliner chair for the past two nights instead of a bed. As you begin your examination, you notice the patient is having obvious respiratory distress and appears to be responsive to verbal stimuli. You contact the dispatcher to confirm an Advanced Life Support (ALS) unit is responding. Just then, the patient appears to become completely unresponsive and stops breathing. 1. Which signs would suggest a patient has inadequate ventilations? 3.As this patient is now unresponsive and possibly not breathing, positive-pressure ventilation will likely be required. What are some of the pitfalls associated with positive-pressure ventilation? 4.Explain how the Venturi mask works and how its use can benefit patients. 5.What are some conditions that may produce an inac- curate pulse oximetry reading? 2.Compare and contrast the differences between oxygen- ation, respiration, and ventilation. 92 Emergency Medical Technician Transition Manual 09153_ch06_5989.indd 92 Chapter 6 Airway Management and Oxygenation 92 8/17/11 8:06:38 PM