PULMONARY FUNCTION TESTING

1. PULMONARY FUNCTION TESTING

2. Objectives Conduct spirometry tests and make calculations from raw test results. Interpret results in light of published norms.

4. Basic spirometry and terminology Tidal volume (TV): volume of air inhaled or exhaled in one normal breath. Inspiratory reserve volume (IRV): maximal amount of air that can be inhaled following a normal inhalation. Expiratory reserve volume (ERV): maximal volume of air that can be exhaled following a normal exhalation. Inspiratory Capacity (IC): maximal amount of air a subject can inhale following a normal exhalation. Vital capacity (VC): maximal amount of air that a subject can exhale after a maximal inhalation.

5. Volumes not easily measured with spirometer Residual volume (RV): volume of air remaining in lungs after maximal inhalation. Functional residual capacity (FRC): volume of air left in lungs after a normal exhalation. Total lung capacity (TLC): total volume of air the lungs can hold.

6. Calculated forced volumes and flows Forced vital capacity (FVC): total volume of air expired after a maximal inhalation when the subject is attempting to exhale as rapidly and forcefully as possible. In healthy subject, FVC = SVC. Forced expiratory volume - one second (FEV1.0): the amount of air exhaled in the first one second of FVC maneuver. Forced expiratory flow from 25-75% (FEF25-75) or Maximal Mid-Expiratory Flow (MMEF): the flow rate during the middle 50% of the FVC maneuver (from 25% to 75% of expired volume). Maximal voluntary ventilation (MVV): the maximal amount of air that a person can breathe in or out in a short period of time - usually 10, 12, or 15 seconds.

7. Use of data Deviations from normal indicators of pulmonary disease Asthma - constriction - restricts flow Emphysema - destruction of alveoli and trapping of air - inability to rapidly exhale and increase in residual volume. Smoking and air pollution effects on lungs

8. Residual volume important in body composition measurements. FEV, FEV1.0, best predictors of disease. FEV/FEV1.0 also used to detect disease MVV sometimes used to evaluate respiratory muscle weakness.

10. Pulmonary Function  Issues Related to Measured Values Overinflation of Lungs Emphysema - COPD - Permanently Asthma - Acutely ? 8 RV + Ratio RV/TLC FEV1/ FVC ratio falls below 80% - Also flow rates fall � With age (lungs less compliant) � Falls with obstructive diseases; e.g. asthma/bronchitis

11. Asthma - obstructive disease 6 increased collapsing force of large airways � obstruction to expiratory flow ? lung volume � bronchodilators may return flow to normal

12. Early COPD - characterized by irreversible 8 in small airway resistance that reduces expiratory flow � not very responsive to dilators

13. Severe COPD - 8 small & large airway resist � severe flow limitations � bronchodilators ? little help � chronic bronchitis and emphysema

14. Emphysema - loss of elastic recoil 6 8 small airway collapse during expiration, thereby 8 resistance � Max Expiratory Flow ? � Bronchodilators have no effect � ? FRC + TLC

15. Training (Ref: Wilmore & Costil, pg 226) In general, lung volumes and capacities � little with training. VC may 8 slightly. TLC doesn�t change much, slightly 8 possible MVV may 8 considerably Due to 8 TV and 8 rate of respiration

16. Procedure Notes Conversion to Body Temperature Pressure Saturated (BTPS) Body Temp . 37o C Saturation with water vapor = 100% All pulmonary function values reported in BTPS, but measurements taken at Ambient Temperature Pressure Saturated (ATPS)

17. Conversion (Ref: CCJ, p. 50) VBTPS = VATPS * BTPSCF Where: BTPSCF = TB(?C) + 273 X PB � PH2O at room temp TR(?C) +273 PB � PH2O at body temp TB = body temp in degrees Celsius (? 37? C) TR = room (or spirometer) temp in degrees Celsius 273 = factor to convert Celsius to Kelvin PB = barometric pressure PH2O = water vapor pressure at room and body temp (CCJ,p. 50)

18. FRC by Nitrogen Washout - Breathing Pure Oxygen (Source: West, Respiratory Physiology, pp. 146-147) General Formula V1 * C1 = (V1 * C3) + (V2 * C2) Where: V1 = Lung Volume V2 = Volume of gas exhaled over washout procedure C1 = [N2] in lungs before washout (atmospheric ? 80%) C2 = [N2] of exhaled gas over washout ([N2] in V2) C3 = [N2] left in lungs after washout measured at end-expiration

19. Solve for unknown V1: (V1 * C1) - (V1 * C3) = V2 * C2 V1 * (C1 - C3) = V2 * C2 V1 = V2 * C2) C1 � C3

20. Remember general constants given for atmospheric air Pb at sea level = 760 mm Hg FIO2 = 0.2093 (or 20.93%) FICO2 = 0.0004 (or 0.04%) FIN2 = 0.7903 (or 79.03%) ? PIO2 = 0.2093 x 760 = 159 mm Hg PICO2 = 0.0004 x 760 = 0.3 mm Hg PIN2 = 0.7903 x 760 = 600 mm Hg

21. Assumption: since atmosphere is composed almost entirely of N2, O2, and CO2, then:  N2% = 100 - O2% - CO2%

22. Calculate residual volume as: (Ref. Wilmore, MSSE, 1980): RV (L) = VO2bag (L) * (b-a) � (c-d) Where: RV = residual volume in liters VO2bag = volume of oxygen in liters added to bag (usually 3-5 L) a = % nitrogen impurity in original oxygen (assume to be 0.0 for practical purposes) b = % nitrogen in rebreathing bag after subject completes breathing maneuver c = % nitrogen in alveolar air at beginning of test (assume 80.0%) d = % nitrogen in alveolar air during last maximal breath (assume 0.2% nitrogen higher than equilibrium %, I.e., b + 0.2% nitrogen)

23. Simplified (CCJ, p. 49): RV = VO2bag * b or VO2bag * b 8.0.0 � (b + 0.2) 79.8 - b Where: VO2bag = volume of O2 in bag at start b = percent of N2 in bag after rebreathing N2 = 100% - %O2 - % CO2 NOTE: If nitrogen analyzer is available, bag nitrogen concentration can be measured directly from the bag.