NSB231 Chapter Notes - Chapter 22: Arterial Blood Gas, Pulse Oximetry, Respiratory Tract
Week 4: Respiratory Assessment & Management
PHYSIOLOGY OF RESPIRATION
• Ventilation: inspiration (air into lungs) and expiration (air out of lungs)
• Inspiration: active process, involves muscle contraction
• Expiration: passive process.
• When elastic recoil reduces, expiration becomes more active with more
effort
• Compliance: measure of the ease of lung expansion.
• If decreased, the lungs are more difficult to inflate (stiff lungs)
• The gas exchange through the alveolar-capillary membrane is by diffusion
• Arterial blood gas (ABG) are measured to determine oxygenation status and acid-base balance.
• PaO2, PaCO2, acidity (pH) and bicarbonate (HCO3-) in arterial blood
• Oxygen delivery to the tissues depends on the amount of oxygen transported to the tissue
and the ease with which haemoglobin gives up oxygen once it reaches the tissues.
• Oxygen saturation monitored through pulse oximetry probe
STRUCTURES AND FUNCTIONS OF THE RESPIRATORY SYSTEM
• The purpose of the respiratory system is gas exchange, the transfer of oxygen and carbon
dioxide between the atmosphere and the blood
• Upper Respiratory Tract
• Nose: warms, cleanses and humidifies air before it enters the lungs
• Mouth
• Pharynx
• Adenoids
• Tonsils
• Epiglottis
• Larynx: vibrational sounds found here lead to vocalisation
• Trachea
• Lower Respiratory Tract
• Bronchi
• Bronchioles
• Alveolar Ducts
• Alveoli: where gas exchange happens
• The Upper Respiratory tract and bronchi/bronchioles are passages that conduct air to the
alveoli.
• These passages are called anatomical dead space because the air located here is not
involved in gas exchange.
• Surfactant: lipoprotein that helps keep alveoli open, preventing alveolar collapse
• Lungs have 2 different types of circulations:
• Pulmonary Circulation
• Provides lungs with blood that participates in gas exchange
• Bronchial Circulation
• Chest wall: shaped, supported and protected by 24 ribs (12 each side).
• Thoracic Cage: Ribs and the sternum that protect the lungs and the heart from injury
• The diaphragm contracts to ↓ intrathoracic pressure = air entering the lungs
• The diaphrag relaxes to ↑ itrathoracic pressure = air leaves the lugs
CONTROL OF RESPIRATION
• Respiratory centre is in the medulla of the brainstem
• It response to chemical and mechanical signals from the body
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Document Summary
Physiology of respiration: ventilation: inspiration (air into lungs) and expiration (air out of lungs) Inspiration: active process, involves muscle contraction: expiration: passive process, when elastic recoil reduces, expiration becomes more active with more effort, compliance: measure of the ease of lung expansion. Larynx: vibrational sounds found here lead to vocalisation. Surfactant: lipoprotein that helps keep alveoli open, preventing alveolar collapse. Control of respiration: respiratory centre is in the medulla of the brainstem. Irritant, muscle stretching and alveolar wall distortion: respiratory defence mechanisms. Filtration of air: mucociliary clearance system, cough reflex, reflex bronchoconstriction, alveolar macrophages. Assessment of the respiratory system: use judgment to determine whether to complete all or part of history and physical examination. Skin tests: test for allergic reactions, tb or fungi: chest x-ray: test for assessment of respiratory system and progression of disease/response to treatment, endoscopic examination: procedure where the bronchi are visualised through fibreoptic tube. Used to obtain biopsy specimens and assess changes resulting from treatment.
