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1 S.M.A.R.T. Dental Nursing Sedation Applied respiratory anatomy & physiology Day 2 Mr J. Henry The airways have 3 main functions. Oxygen delivery system (piping & tubing) Protection of lungs from foreign matter Warming and humidifying gases Oxygen Delivery i.e. The Plumbing / Piping Which facilitate the delivery of atmospheric air to the lung alveoli Airway Resistance Resistance to air flow is altered by the diameter of the bronchi and bronchioles Increased airway resistance (narrowing) is the main problem in obstructive airway diseases such as ASTHMA Protection of the lungs Air is partially filtered by nasal hairs Bacteria and other particles, which escape this, are usually trapped in the layer of mucous lining the airways. Cilia lining the trachea, bronchi and bronchioles convey the mucous back up towards the larynx and out into the pharynx were it is swallowed. Epiglottis deflects food around laryngeal opening Vocal folds prevent food foreign bodies entering the trachea (trigger cough reflex) Warming and humidifying gases By the time the air reaches the alveoli it is warmed and humidified making gas exchange much easier. J. Henry 2015 2 Respiratory tract J. Henry 2015 3 Muscles of Respiration Normal Inspiration (active process) External intercostal muscles contract (pull ribs up and out) Intercostal nerves T1-T12 Diaphragm contracts (dome of diaphragm pulled down) Phrenic nerves, C345 Accessory muscles in the neck used during maximal inspiration (elevate sternum and first 2 ribs) Normal Expiration (passive process) Elastic recoil of stretched lungs and relaxation of the inspiratory muscles Forced Expiration (active process) Internal intercostal muscles (actively pull ribs downwards and inwards) Abdominal muscles (increase abdominal pressure, forcing diaphragm upwards) Lung Volumes Volume of gas moved in and out the lungs is dependent on age, sex, body build and level of fitness Normal Tidal Volume 0.4 –0.5 L Normal Respiratory Rate 12-16 breaths per minute Respiratory minute volume = Tidal Vol x Resp Rate = 0.5 X 12 = 6 L / min J. Henry 2015 4 Dead Space Not all the inspired air will actually reach the areas within the lungs where gas exchange can takes place. Anatomical Dead Space Includes all the upper airway down to the bronchial level. No gas exchange takes place in these areas. The air, which enters these areas during inspiration, is expelled again during expiration without contributing to pulmonary oxygenation. Physiological Dead Space Anatomical dead space plus alveoli in the lung, which are ventilated but receive very little pulmonary perfusion. (Normally physiological dead space is about 150ml) Alveolar ventilation rate = (tidal volume –dead Space) x Respiratory rate ( 0.5 - .15 ) x 12 Alveolar ventilation rate = 4.2 L/min Inspiratory Reserve Volume (IRV) It is usually possible for a person to inhale a further 3 L of air over and above the tidal volume, this is called the inspiratory reserve volume (IRV). Expiratory Reserve Volume (ERV) If at the end of a normal exhalation, as much air as possible is forcibly expelled from the lungs, a further 1 L can be eliminated; this is called the expiratory reserve volume. Vital Capacity (VC) The total volume of air that can be expired after a maximum inspiration (TV + IRV + ERV) is known as the vital capacity. (VC) which is about 4.5 L for an adult. Residual Volume (RV) After maximum respiratory expiration approximately 1.5 L of air, the residual volume (RV), remains in the lungs. Total Lung Capacity The total lung capacity is around 6 L (TV + IRV + ERV + RV). J. Henry 2015 5 Oxygen Transport Vast majority O2 in blood is transported within RBC bound to haemoglobin; the reminder is dissolved in plasma. Each haemoglobin molecule has 4 globin elements, each attached to separate pigmented haem element Oxygen binds reversibly with the haem elements forming oxyhaemoglobin. Single molecule of haemoglobin can carry up to four O2 molecules Carbon Dioxide Transport 60-70% CO2 is carried in the plasma as bicarbonate ions (HCO3-) (CO2 diffuses into RBC’s where it reacts with water and is converted into bicarbonate ions by the action of carbonic anhydrase enzyme in RBC’s. The bicarbonate ions then diffuse back out into the plasma) 20-30% CO2 is carried in the blood as carbamino groups (formed by a reaction between CO2 and amino acid residues in plasma proteins) 10 % CO2 is carried in the blood as dissolved CO2 Control of Respiration The rate and depth of respiration is controlled by the respiratory (ventilation) centre, which is situated in the brain. Breathing can be altered by chemical and nervous control. There are chemoreceptors situated in the aorta and carotid arteries and the respiratory centre. They are sensitive to a rise in the level of circulating carbon dioxide (C0 2), a drop in blood pH or reduced levels of circulating oxygen (02). Stretch receptors, situated in the lungs and respiratory muscles, can stimulate the vagus nerve to inhibit inspiration. Emotions can also affect breathing by influencing the higher centers of the brain. An increased partial pressure of carbon dioxide (Paco2) (hypercapnia) is a more significant and sensitive stimulus for respiration than hypoxia; a low Pao2 will cause an increase in ventilation rate but this is far less dramatic than the hypercapnic drive. J. Henry 2015 6 The hypoxic drive is a back-up mechanism, but it may assume importance in patients with chronic lung disease. Factors, which might affect normal breathing and Oxygen Delivery to lungs Pulse Oximeter Non-invasive electromechanical monitoring of arterial SaO2 Allows early detection of a drop in Oxygen Saturation SaO2, If monitoring the patient clinically, may only notice clinical signs of hypoxia / cyanosis if saturation drops to 75 %, by then it may be to late !! Oxygen Dissociation curve Under normal conditions blood is 97% saturated at the PO2 of systemic Arterial blood (13 kPa). Saturation falls to 75% on reducing the PO2 to 5.3 kPa , the value found in systemic venous blood. J. Henry 2015 7 Factors which might affect normal breathing and oxygen delivery to lungs Anatomical Problems Narrowing of Nasopharynx - common cold, Nasal polyps, enlarged adenoids Narrowing of Oropharynx - large tongue, large soft palate, enlarged tonsils, sore throat, restricted opening Narrowing of Laryngopharynx - laryngitis, build up of mucus or catarrh in smokers Medical Problems Respiratory disorders Musculoskeletal disorders Cardiovascular disorders Haematological disorders - Asthma , chest infection, bronchitis - Multiple sclerosis, myasthesia gravis - Heart failure, atherosclerosis - Anaemia Other Problems relevant to dentistry Shared airway - Dentist drill , suction, water, mirror, matrix bands all crammed in!!!. Position of the patient Lying back , chin down tends to close airway J. Henry 2015 8 Patient upright Patient Lying back J. Henry 2015 9 What do you do if patient obstructs there airway?? Clear blockage Head tilt Chin lift Pulse Common sites Carotid Artery Brachial Artery RadialArtery Assess Rate (beats per minute) Rhythm ( regular / irregular ) Volume (strong / weak) J. Henry 2015