Diseases Increasing Airway Resistance II - Fundamentals of Physiology | BMS 360, Study notes of Biology

Download Diseases Increasing Airway Resistance II - Fundamentals of Physiology | BMS 360 and more Study notes Biology in PDF only on Docsity! 23 April Diseases Increasing Airway Resistance II Chronic obstructive pulmonary disease (COPD): Major cause of disability and death Emphysema: Lung tissue loss around alveoli, causing airway collapse. Difficult to inflate lungs due to loss of elastic tissue. Shortness of breath. Smoking is a major cause Chronic bronchitis: Loss of ciliated cells Excess mucous production in the bronchi, causing obstruction; chronic inflammation of small airways Airway resistance is very high Smoking is a major cause Emphysema with chronic bronchitis Smoking can cause both Similar to figure 13 – 18 Respiratory Volumes Tidal volume: Volume of air inhaled or exhaled in a single breath. Relaxed breathing, about 500 mL Inspiratory reserve volume (IRV): The maximum volume in deep inspiration (minus the relaxed tidal volume) Functional residual capacity: Volume of air remaining in the lungs after normal relaxed expiration Residual volume: Amount of air remaining in lungs after maximal exhalation Expiratory reserve volume (ERV): Volume that can be exhaled with maximal effort, less the relaxed tidal volume Pulmonary Function Tests Vital capacity: The maximal volume of air that can be exhaled after maximal inhalation. Equals (tidal volume + IRV + ERV) = about 4.7 L Forced expiratory volume 1 sec (FEV1): Maximum inhalation followed by expiration as fast as possible in 1 sec. Normal: about 80% of the vital capacity Obstructive pulmonary disease (emphysema, bronchitis, asthma) Increased airway resistance cause low FEV1 values Narrowed airways may cause wheezing sound Vital capacity remains normal Restrictive lung disease Abnormal lung tissue (fibrosis), pleura, chest wall, respiratory muscles or respiratory nerves Impaired respiratory movement Restricted lung expansion reduces vital capacity Reduced FEV1 Normal ratio (FEV1/vital capacity) as both values are reduced about equally Alveolar Ventilation Minute ventilation rate: Total ventilation in 1 minute = (respiratory rate) x (tidal volume) Example: Minute ventilation rate during quiet breathing = (12 breaths/min) x 500 mL/breath = 6,000 mL/min Not all of this air is available for respiration because some of it is dead space Physiological dead space Anatomical dead space is the volume of air which is NOT participating in diffusion, which is the air in the conducting zone (about 150 mL0 Alveolar dead space is due to some alveoli without blood supply. Normally quite small, but in disease can be larger Fig 13 – 21: Sea level, resting The partial pressures of oxygen in the alveoli determines its pressures in blood pO2 is 160 mm Hg in the atmosphere vs. only 105 mm in alveoli, because some oxygen has diffused into blood pO2 alveoli (105 mm) nearly the same as in pulmonary vein (100 mm) in accordance with Henry’s Law; slightly lower in the vein due to ventilation-perfusion mismatching pO2 in alveoli pO2 lower in air and alveoli at higher elevations Faster ventilation rate increases alveolar pO2 Faster oxygen consumption in tissues reduces alveolar pO2 pCO2 in alveoli pCO2 of the atmospheric air is nearly zero at sea level, so elevation has little effect Faster ventilation rate decreases alveolar pCO2 Faster tissue carbon dioxide production increases alveolar pCO2 Figure 13 – 22 Changes in the rate of ventilation alter the concentration of gases in the alveolar air CO2 Ventilation Relative to Its Production Adequacy of ventilation Hypoventilation: Alveolar pCO2 higher than normal. Tissue production rate of CO2 greater than its ventilation rate Example: respiratory depression with opiates Hyperventilation: Alveolar pCO2 lower than normal. Ventilation rate of CO2 greater than its production rate Blood pCO2 then falls. Example: panic attack Hyperventilation does NOT mean faster ventilation In exercise, faster CO2 production is proportionately matched to faster ventilation, and pCO2 remains normal