Volumes, Capacities, and Function Tests

1. Respiratory VOLUMES (20 yr old healthy male, 155 lbs.)
1. tidal volume (TV) - normal volume moving in/out (0.5 L)
2. inspiratory reserve volume (IRV) - volume inhaled AFTER normal tidal volume when asked to take deepest possible breath (2.1-3.2 L)
3. expiratory reserve volume (ERV) - volume exhaled AFTER normal tidal volume when asked to force out all air possible (1.0-2.0 L)
4. residual volume (RV) - air that remains in lungs even after totally forced exhalation (1.2 L)
2. Respiratory CAPACITIES
1. inspiratory capacity (IC) = TV + IRV (MAXIMUM volume of air that can be inhaled)
2. functional residual capacity (FRC) = ERV + RV (all non-tidal volume expiration)
3. vital capacity (VC) = TV + IRV + ERV (TOTAL volume of air that can be moved)
4. total lung capacity (TLC) = TV + IRV + ERV + RV (the SUM of all volumes; about 6.0 L)
3. Dead Space
1. anatomical dead space - all areas where gas exchange does not occur (all but alveoli)
2. alveolar dead space - non-functional alveoli
3. total dead space - anatomical + alveolar
4. Pulmonary Function Tests
1. spirometer - measures volume changes during breathing
• obstructive pulmonary disease - increased resistance to air flow (bronchitis or asthma)
• restrictive disorders - decrease in Total Lung Capacity (TB or polio)
2. minute respiratory volume (MRV) - total volume flowing in & out in 1 minute (resting rate = 6 L per minute)
3. forced vital capacity (FVC) - total volume exhaled after forceful exhalation of a deep breath
4. forced expiratory volume (FEV) - FVC volume measured in 1 second intervals (FEV1....)
5. Alveolar Retention Rate (AVR)
• AVR = breath rate X (TV - dead space)
• (NORMAL) AVR = 2/minute X (500 ml - 150 ml)
• (NORMAL) AVR = 4.2 L

Category: Physiology Notes