COMPARISON OF THORACOABDOMINAL CALIBRATION METHODS IN NORMAL HUMAN-SUBJECTS

In 19 normal subjects in the supine posture, we compared accuracy and precision of calibration methods that utilized different ranges of tid al volumes and thoracoabdominal partitioning: spontaneous quiet breath ing (QB), isovolume maneuvers, and voluntary efforts to breathe with v ariable tidal volume and thoracoabdominal partitioning. Thoracic and a bdominal movements were measured with the respiratory area fluxometer. Calibration methods utilizing one or more types of respiratory effort s were applied to three measurement situations: QB, variable breathing (volume and thoracoabdominal partitioning), and simulated obstructive apnea (isovolume efforts). Qualitative diagnostic calibration (QDC) i ncluded QB data only. The isovolume method (ISOCAL) included isovolume tric efforts at end expiration (functional residual capacity) and QB. Multilinear regression analyses were performed on data sets that inclu ded 1) voluntary efforts to breathe with variable volume and thoracoab dominal partitioning (CAL 1), 2) QB in addition to variable volume and partitioning (CAL 2), and 3) isovolume maneuvers in addition to QB an d variable volume and partitioning efforts (CAL 3). When calibration d ata included a wide range of tidal volume, variable thoracoabdominal p artitioning, and isovolume efforts (CAL 3), a stable calibration with small bias and scatter during all respiratory patterns was obtained. E xcluding isovolume maneuvers (CAL 2) and QB (CAL 1) did not diminish a ccuracy. Limiting data to isovolume efforts at functional residual cap acity plus QB (ISO-CAL) caused a significant increase in scatter durin g variable breathing patterns. Limiting calibration data to that porti on of QB with small variation in the uncalibrated sum of thoracic and abdominal movements (QDC) caused significant increases in scatter in b oth isovolume efforts and variable breathing.