Abstract
The purpose of this study was to test the hypothesis that voluntary changes in thoracoabdominal pattern of breathing may increase total respiratory resistance. Thirty-one normal subjects were asked to control their thoracoabdominal pattern of breathing by using a visual feedback. Thoracic and abdominal volume changes were measured by inductance plethysmography. Respiratory resistance and elastance were measured by forced oscillometry. The mean (±SD) percent thoracic contributions to tidal volume during thoracic or abdominal breathing were 75 (±11) and 25% (±9), respectively. These changes induced small but significant increases in resistance ( P<0.005) and elastance ( P<0.002). The increased resistance was observed in 22 subjects for thoracic breathing ( P<0.016) and in 21 subjects for abdominal breathing ( P<0.043). The mean value (±SD) of individual increases in resistance during thoracic or abdominal breathing, compared with normal breathing, were 9.2±17.5 and 9.4±19.9%, respectively. The fact that departing from spontaneous pattern increases respiratory resistance is consistent with the notion that breathing pattern is optimally adjusted on the basis of mechanical criteria.
Published Version
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