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Respiration My notes Learning Objectives • Relate structure to function of the respiratory system • Give an account of the mechanisms of ventilation: at rest, during exercise, swallowing & during vocalisation • Be aware of how a selection of common conditions may affect lung function and the relevance for SLTs • Demonstrate knowledge of assessment and treatment options for clients with lung conditions Anatomy • Refer to self directed study The Thoracic Cavity The Sternum • Manubrium • Body of sternum • Xiphoid process The Respiratory Tree (Airway) The Diaphragm The Plura • 2 cavities-each containing a lung • Outer parietal membrane, inner visceral membrane, with fluid filled pleural cavity between them Functions of fluid: Acts as a lubricant Surface tension forces ‘hold membrane together’ Blood supply Separate blood supplies: Parietal supply is systemic Visceral supply is pulmonary This has implications for fluid exchange Ventilation • Breathing or ventilation is a collective term for two processes: inspiration and expiration. • Inspiration is an active process requiring energy to drive muscular contraction. • Expiration is largely a passive process, achieved through relaxation and elastic recoil of chest and lung structures. Inspiration • Inspiration is an active process driven by nerve impulses from respiratory centres in brain. • Activity in the phrenic and thoracic spinal nerves results in contraction of the diaphragm and external intercostal muscles. • Expansion of chest cavity creates a lower air pressure relative to outside of the body. Expiration • When the body is at rest, the process of expiration is passive, and is the result of elastic recoil of airway tissues. • Expiration can be made active during body exertions, by using additional muscles in the ribcage (internal intercostal muscles) and abdomen (abdominus rectus). • This use of energy during forced expiration is an important clinical consideration for persons with airway disease. The muscles of respiration Muscle Action Diaphragm Draws central tendon inferiorly facilitating inspiration External intercostals Draws the ribs upwards increasing volume of thoracic cavity for inspiration Internal intercostals Draws the ventral part of the ribs downwards decreasing volume of thoracic cavity for expiration Abdominal muscles External oblique Internal oblique Expiratory: Pulls abdominal wall inwards increasing intra-abdominal pressure and causing diaphragm to move into thoracic cavity Displace rib cage downwards and inwards Inspiratory: Direct fascilitation of diaphragmatic action Contract in phase with expiration Transversus abdominis Rectus abdominis Scalenius Anterior Raises first rib for inspiration Scalenius Posterior Raises the first rib of inspiration Scalenius Posterior Raises second rib for inspiration Sternocleidomastoid Raises the first rib and sternum ‘pump handle’ action The respiratory tree • • • • • • • • Upper respiratory tract: nasal cavity and pharynx Trachea Primary (or main) bronchi Secondary bronchi 12-13 generations of tertiary bronchi Terminal bronchioles at generation 16 Then 3 generations of respiratory bronchioles 3 generations of alveolar ducts open into 300 million alveoli Alveoli • Alveoli are the structures of gaseous exchange in the lung Alveolar capillary membrane: where gas exchange takes place • The alveolar membrane is composed primarily of Simple Squamous epithelium which is very thin so as to provide the minimum distance possible for gaseous exchange. Gas exchange • Exchange of gasses (O2 & C02) across the alveolar membrane occurs as a result of the pressure differences across the alveolar capillary membrane • Diffusion requires a concentration gradient. • The concentration (pressure) of O2 in the alveoli must be kept higher than the level in the blood to allow O2 to move into the blood. • Conversely the concentration (or pressure) of CO2 in the alveoli must be kept at a lower level than in the blood. This allows CO2 to move into the alveoli and ultimately be expired Pulmonary Clearance • The lining of the respiratory system is ciliated • Mucus is produced in goblet cells Removal of inhaled particles Particles trapped in mucous and moved by cilia Particles >4.5 micrometres trapped in nasal passage Smaller particles trapped in bronchial tree by mucociliary escalator Process can be effected by • Stress • Heavy dust exposure • Cigarette exposure • Infectious agents • Temperature (cold) • Poor ventilation Lung volumes Volume Volume and description Total lung capacity The total volume the lung can accommodate (4-8L) Tidal volume Volume of air moved during a normal breath (0.4-1L) Residual Volume Volume of air remaining in the lungs despite maximal exertion (1-1.5L) Forced vital capacity FVC The maximal volume of air which can be moved in and out during a single breath following a maximal inspiration (4-5L) FVC1 Lung Volumes Control of Respiration • Respiration is largely controlled by nervous activity. • Mediated by the respiratory centres found in the brainstem. • Breathing is largely an involuntary process, controlled by rhythmic nerve impulses originating in the respiratory centres. • Three major areas of the brainstem involved in breathing have been identified.. Respiratory centres • Dorsal respiratory group (DRG) in the medulla: – Appears to be the respiratory pacemaker (inspiratory centre).Has cyclic on/off activity producing12-15 breaths per minute. • Pontine respiratory group (PRG): – also called pneumotaxic centre. Inhibitory impulses from here fine tune breathing. • Ventral respiratory group (VRG) in the medulla: – Role not exactly clear, but has mixture of neurons involved in inspiration & expiration. Mainly involved in forced breathing. Influences on the respiratory centres • Higher brain centres in the cerebral cortex can exert voluntary control over breathing as well as hypothalamic centres involved in emotion & pain. • Peripheral chemoreceptors in vascular system and central chemoreceptors in brain detect changes to oxygen, carbon dioxide and acidity levels. • Stretch receptors and irritant receptors in lungs and activity receptors in muscles and joints also send messages to respiratory centres. Ventilation during exercise/excursion Ventilation during speech. To achieve phonation and articulation, the normal pressurized air stream of expiration is transformed into a series of pulses by constricting the air stream at the vocal folds in the larynx or at other locations in the respiratory tract and oral cavity (the vocal tract) For each phoneme* or physical segment of a sound a specific frequency of vibration is generated which passes through the vocal tract. This is a highly complex process in which certain frequencies are enhanced and others are damped down by manipulating the shape of the vocal tract and the pressure and rate of airflow. . The demands of speech production are so different from the other functional demands that the normal control and pattern of ventilation have to be overridden. Speech is created during the expiratory phase and respiratory muscle activity and elastic recoil has to be used to maintain and vary the pressure gradient across the vocal cords. The respiratory cycle must also be coordinated so that appropriate divisions of speech into phonemes, syllables, words, phrases and sentences can occur. The inspiratory cycle increases in volume and becomes more rapid, taking about 0.6 sec compared to about 2 seconds in normal quiet breathing. The expiratory cycle is prolonged to conserve the speech divisions. In some instances it may occur over a period of about 30 seconds. For speech to be maintained in an effective manner, an adequate pressure must be maintained across the vocal cords. This would become difficult if the expiration was to proceed to residual volume (as in a maximal forced expiration) and normally the next inspiratory cycle occurs at a lung volume well above residual volume. In normal conversation this will occur at a volume of about 1.5 litres above residual capacity. In loud speech this volume will have to be increased to a point were it approaches inspiratory capacity. Clearly any increased inspiratory capacity requires greater involvement of the external intercostal muscles and possibly the accessory muscles of inspiration The control of air pressure across the vocal cords during the expiratory phase requires a complex interaction of the muscles of inspiration (to counteract the tendency for elastic recoil) as well as the muscles of expiration (particularly as the expiratory movement proceeds and lung volume declines). The complexity and particularly the rapidity of the controls is such that normal mechanisms of efferent (motor) activity and associated afferent (sensory) feedback would take too long and as a result vocalisation involves a complex series of learned neural patterns. 1. 2. Respiration during swallowing INVESTIGATION Observations • Respiratory rate • Breathing pattern – Diaphragmatic – Thoracic – Clavicular Think yourselves lucky, when I trained we had to wear just bra and were very, very embarrassed Pulse Oximetry Vitaolgraph ‘alpha’ Mini Wright Peak Flow meter http://www.youtube.com/watch?v=6kbgZWS5wH0 The Forced Expired Volume (FEV1) An indication of lung compliance (ability to breathe efficiently). LUNG CONDITIONS Pneumonia • Inflammatory condition of the lung Pneumonia and SLT • Aspiration pneumonia Chronic Obstructive Pulmonary Disease Chronic Bronchitis Excess mucus production form the large airways Daily cough. 3 months/year. 2 consecutive years No obstruction Obstructive Bronchitis • Small airway obstruction with inflammation and fibrosis Emphysema • Destruction of alveolar walls • Abnormal enlargement of air spaces • Loss of elasticity • Impaired gas transfer • Obstruction of airways • Smoking is biggest cause • A1antitripsin deficiency COPD and SLT • Dysphagia • Communication Management Voice/ Communication Swallowing • Team working • Medication • Nutrition and hydration • Anxiety • Breathing techniques and pacing • Specific techniques