Criteria for acceptance and reproducibility were observed. The values of the spirometric variables were compared to predicted values according to published Pereira values (Pereira, 2002). Respiratory Metabolism inhibitor inductive plethysmography (Respitrace®, Nims, Miami,
FL, USA) was used to assess breathing patterns and to measure thoracoabdominal motion. The accuracy of plethysmography in the evaluation of breathing patterns has been determined at rest and during physical activity in both adults and children (Chadha et al., 1982). Tidal volume measurements are satisfactory as long as the body position remains constant after the calibration procedure (Chadha et al., 1982). The VE-822 price system consists of two bands (Teflon®-coated inductance bands) that measure changes in the cross-sectional area of the rib cage (RC) and abdomen (AB). Bands of appropriate size were placed around the RC and AB; the upper edge of the RC band was placed at the level of the axilla, and the abdominal band was placed at the level of the umbilicus. Signals were calibrated using qualitative diagnostic calibration (QDC) (Sackner et al., 1989) during natural breathing. This method is a two-step procedure whereby the rib cage and abdominal electrical gains of the respiratory inductive plethysmography amplifiers are correctly partitioned during tidal breathing and are
subsequently the output of the spirometer was adjusted to correspond to the plethysmograph values. The subject subsequently breathed into a spirometer using a mouthpiece (Vitatrace, Pro Médico, Rio de Janeiro, RJ, Brazil) with the nose clipped for 30–60 s, and the electrical spirometer output was recorded with
a computer and was used to calibrate the respiratory inductive plethysmographic sum signal for absolute volume in ml. The spirometer was calibrated with a 1-liter syringe (Vitalograph, Buckingham, England) using computer software (RespiPanel 4.0, Nims), and signals were recorded with a digital acquisition system (RespiEvents 5.2, Nims). Transcutaneous oxygen saturation (SaO2) and pulse rate were recorded by pulse oximetry (Datex-Ohmeda Inc., Louisville, CO, USA) nearly using a finger probe (Bloch et al., 1995 and Sackner et al., 1989). The following variables were measured using a digital acquisition system on a breath-by-breath basis: tidal volume (VT), respiratory frequency (f), minute ventilation (VE), inspiratory duty cycle (TI/TTOT), mean inspiratory flow (VT/TI), percentage of rib cage motion (%RC), percentage of abdomen motion (%AB = 100 − %RC) and phase angle (PhAng). The PhAng is related to thoracoabdominal motion and reflects the delay between RC and AB excursions: values range from 0° (perfect synchrony) to 180° (paradoxal movement). After 30 min of recording, 6–10 min of steady-state readings were selected for analysis.