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19 Rs Rs Ventilation

19 Rs Rs Ventilation - RESPIRATORY VENTILATION Page 1...

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RESPIRATORY VENTILATION AC Brown Page 1 A 7c VENTILATION PARAMETERS A. Lung Volumes 1. Basic volumes: elements a. Tidal Volume (V T , TV): volume of gas exchanged each breath; can change as ventilation pattern changes b. Inspiratory Reserve Volume (IRV): maximum volume that can be inspired, starting from the end inspiratory position (potential volume increase at the end of inspiration) c. Expiratory Reserve Volume (ERV): maximum volume that can be expired, starting from the end expiratory position (potential volume decrease at the end of expiration) d. Residual Volume (RV): volume remaining in the lungs and airways following a maximum expiratory effort (note: lungs cannot empty completely because of (1) stiffness when compressed and (2) airway collapse and gas trapping at low lung volumes) 2. Capacities: combined volumes a. Vital Capacity (VC): maximum volume of gas that can be exchanged in a single breath VC = TV + IRV + ERV b. Total Lung Capacity (TLC): maximum volume of gas that the lungs (and airways) can contain TLC = VC + RV = TV + IRV + ERV + RV c. Functional Residual Capacity (FRC): volume of gas remaining in the lungs (and airways) at the end expiratory position FRC = RV + ERV d. Inspiratory capacity (IC): maximum volume of gas that can be inspired from the end expiratory position IC = TV + IRV
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RESPIRATORY VENTILATION AC Brown Page 2 A 7c VENTILATION PARAMETERS (continued) A. Lung Volumes (continued) 3. Measurement of volumes: Spirometer/Spirometry 4. Typical Values (young male of average size) TV = 0.5 L (10% TLC) VC = 4.8 L ( 5 Liters; 80% TLC) IRV = 3.0 L (50% TLC) TLC = 6.0 L ERV = 1.3 L (20% TLC) FRC = 2.5 L RV = 1.2 L (20% TLC) IC = 3.5 L Note: "normal" values depend upon age, sex, and size Note: the above percentages for TV, IRV, and ERV are for a person at rest breathing normally; RV, VC, and TLC do not depend on whether the person is at rest or is breathing more vigorously B. Ventilation 1. frequency or respiration rate (f or RR): breaths per unit time typical value at rest: 12/min (but much individual variation) 2. ventilation rate: total volume inspired or expired per unit time (written as V’ or V-dot); sometimes called Minute Volume (MV) when measured per minute; to avoid ambiguity, usually measured as volume expired, V E MV or V E ’ = f × TV typical value at rest: MV or V E ‘ = 12/min × 0.5L = 6 L/min
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