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. 2015 Apr 3:407–435.e18. doi: 10.1016/B978-1-4557-3383-5.00025-7

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Copyright © 2016 Elsevier Inc. All rights reserved.

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Figure 25-12 — A closed, constant-volume, variable-pressure whole-body plethysmograph.

As described in eFigure 25-5, at end-expiration airflow is zero, thoracic gas volume (V) = functional residual capacity, and alveolar pressure (Palv) = mouth pressure (Pm) = barometric pressure (Pbar). The rectangle represents the plethysmograph. When the subject inhales against an occluded shutter in the airway, airflow remains zero, but V increases by ΔV to V′ and Pm (= Palv) increases by ΔP (P + ΔP) to equal P′. When Pm is plotted against box pressure (Pbox), the slope of the line (α) yields ΔV/ΔPalv, and V=ΔV/ΔPalv × Pbar, as indicated in the text. , airflow.

(Modified from Comroe JH Jr, Forster RE II, DuBois AB, et al: The lung: clinical physiology and pulmonary function tests, ed 2, Chicago, 1962, Year Book.)

Inline graphic — A closed, constant-volume, variable-pressure whole-body plethysmograph.

As described in eFigure 25-5, at end-expiration airflow is zero, thoracic gas volume (V) = functional residual capacity, and alveolar pressure (Palv) = mouth pressure (Pm) = barometric pressure (Pbar). The rectangle represents the plethysmograph. When the subject inhales against an occluded shutter in the airway, airflow remains zero, but V increases by ΔV to V′ and Pm (= Palv) increases by ΔP (P + ΔP) to equal P′. When Pm is plotted against box pressure (Pbox), the slope of the line (α) yields ΔV/ΔPalv, and V=ΔV/ΔPalv × Pbar, as indicated in the text. , airflow.

(Modified from Comroe JH Jr, Forster RE II, DuBois AB, et al: The lung: clinical physiology and pulmonary function tests, ed 2, Chicago, 1962, Year Book.)