Body plethysmographic measurement of thoracic gas volume without
panting against a shutter.
Agrawal, Anurag, and Krishna P. Agrawal.
INMAS Asthma Research Cell, VP Chest Institute, Delhi-110007,
INDIA
APStracts 3:0213A, 1996.
When a subject breathes through a pneumotachograph in a body box, the
measured value of specific airway resistance (SRaw1) is equal to the
product of TGV and the sum of the airway resistance (Raw) and the
instrumental resistance(Rins). If an additional resistance (Radd) is
put in the breathing path, the measured specific airway resistance
(SRaw2) exceeds SRaw1 by the product of TGV and Radd and can be used
for determining TGV. Using a device to increase the instrumental
resistance by a known amount (Radd) during normal breathing, SRaw1
and SRaw2 were measured in 3 normal subjects, 16 asthmatics, 2
patients with COPD and 1 patient with restrictive lung disease, from
the slopes of the X-Y plots of airflow vs box signals, obtained
before and after adding Radd and TGV was calculated by dividing
(SRaw2 - SRaw1) by Radd. We also determined their TGV by the panting
method of DuBois et al. and FRC by the helium dilution method. The
results of the new method were quite reproducible (coefficient of
variation = 5.6) and equivalent to those obtained by the other two
methods.
Received 21 September 1995; accepted in final form 20 March 1996.
APS Manuscript Number A1024-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 1 May 96