ATS Pulmonary Function Laboratory Manual

ATS Pulmonary Function Laboratory Management & Procedure Manual | 3rd Edition

Calculations Calculations are usually performed by a computerized data acquisition system and include the following terms (49):

1.

uptake

Maximal O 2

˙ V o 2

max

2.

Minute ventilation (expired)

˙ V e

CO 2

output

3.

˙ V co 2

4.

pulse

O 2

˙ V o 2

/HR

5.

Ventilatory equivalent for oxygen

˙ V e/ ˙ V o 2 ˙ V e/ ˙ V co 2

6.

Ventilatory equivalent for carbon dioxide

7. 8.

AT, VT, GET RER, RQ, R

Anaerobic, ventilatory, or gas exchange threshold

Respiratory exchange ratio, ˙ V co 2

/ ˙ V o 2

9.

Vd/Vt%

Dead space to tidal volume ratio as a percent

Arterial partial pressure of O 2 Arterial partial pressure of CO 2 End-tidal partial pressure of CO 2 End-tidal partial pressure of O 2

10. 11. 12. 13.

Pa O 2

Pa CO 2

Pet CO 2 Pet O 2

Though the precise form of equations will vary depending on the technique used, the equations should conform to the following general guidelines: 1. ˙ V e is calculated from the timed collection of expired gas, with gas volumes being corrected to BTPS condi- tions: ˙ V , BTPS = ˙ V , ATPS × ( ATPS to BTPS factor ) t ( min ) where: ˙ V e,BTPS = expired minute ventilation in L/min at BTPS ˙ V e,ATPS = expired volume (L) at ambient temperature and pressure conditions collected over sampling time (t). ATPS to BTPS factor = conversion from ATPS to BTPS conditions

( PB − PH 2 O ) × ( 310 ) ( PB − 47 ) × ( TA + 273 )

ATPS to BTPS factor =

where: PH 2 O = water vapor pressure at the ambient temperature (TA). Must be obtained from tables of water vapor pressure versus temperature. PB = barometric pressure.

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