title: Measurement of tidal breath by determination of chest wall volume displacement in patients with airflow obstruction.
abstract: We compared tidal volume (VT) measured from the integrated airflow signal of a pneumotachygraph (PNTG) in ten patients, seated comfortably, with airway obstruction to VT, recorded simultaneously, by three chest-wall volume-displacement methods: two-channel magnetometer, isovolume calibration (mag-isov); respiratory inductance plethysmograph, isovolume calibration (rip-isov); and, inductance plethysmograph, least squares calibration (rip-l sq). There was no difference between VT, measured without PNTG, with each of the methods. When mouthpiece, noseclips, PNTG, and finally, dead space were included in a breathing circuit, VT increased to approximately one and one-half times that measured without the mouthpiece. Inspiratory volumes were measured with similar error by each method (mag-isov, 8.61 +/- 5.73 percent SD; rip-isov, 9.30 +/- 6.12 percent SD; rip-l sq, 8.43 +/- 6.27 percent SD). We conclude that in airway obstruction patients seated in a constant position, over the range of inspiratory volumes studied, error associated with chest wall volume-displacement methods is no greater than in normal subjects.
mesh_terms: D000005:Abdomen; D000328:Adult; D000368:Aged; D001249:Asthma / Q000503:physiopathology; D002138:Calibration; D005260:Female; D006801:Humans; D008173:Lung Diseases, Obstructive / Q000503:physiopathology*; D008176:Lung Volume Measurements / Q000295:instrumentation; D008297:Male; D008875:Middle Aged; D012119:Respiration; D012272:Ribs; D013909:Thorax; D013990:Tidal Volume