ATS Pulmonary Function Laboratory Manual

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

Appendix 9.4  Sample Raw Calculation Conditions Calibration (cal) and calculation factors: Flow ˙ V = 1.0 L/s/cm

Mouth pressure (Pao) = 2.5 cm H 2 O/cm Body box pressure (Pbox) = 10 ml/cm Body Box breathing system resistance (Rapp) = 0.2 cm H 2 O/L/s PB (corrected for water vapor pressure at 37° C) = 970 cm H 2 O

Step 1: Calculate Raw

Raw = slope of closed − shutter panting maneuver slope of open − shutter panting maneuver

× cal factors − Rapp

Raw = Δ Pao/ Δ Pbox Δ ˙ V/ Δ Pbox

× Pao cal factor/Pbox cal factor V cal factor/Pbox cal factor

− Rapp

The slopes can be measured as the tangent of the angle. The slope of the open-shutter panting maneuver is mea- sured to be 55°, resulting in a tangent of 1.428. The slope of the closed-shutter panting maneuver is measured to be 45°, resulting in a tangent of 1.000. Substituting these values and the calibration factors yields: Raw = 1 . 000 1 . 428 × 2 . 5 cm H 2 O/cm − Rapp

10 ml/cm 1 L/s/cm 10 mL/cm

Raw = 0 . 700 × 2 . 5 cm H 2 O/L/s − 0 . 2 Raw = 1 . 55 cm H 2 O/L/s

Step 2: TGV

1 slope of closed − shutter panting

× Pbox cal factor Pao cal factor

TGV = PB ×

TGV = 970 cm H 2 O × 1 1 . 00 ×

10 ml/cm 2 . 5 cm H 2 O/cm

TGV = 970 cm H 2 O × 4 ml/cm H 2 O TGV = 3 , 880 ml , or 3 . 88 L

Step 3: Calculate Gaw, sGaw, and sRaw Use the Raw and TGV results to calculate lung volume–adjusted Raw values: Gaw, sGaw, and sRaw Gaw = 1 Raw = 1 1 . 55 = 0 . 65 sGaw = Gaw TGV = 0 . 65 3 . 88 = 0 . 17 cm H 2 O/L/s/L sRaw = Raw × TGV = 1 . 55 × 3 . 88 − 6 . 01

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