Respiratory variations in pulse pressure and photoplethysmographic waveform amplitude during positive expiratory pressure and continuous positive airway pressure in a model of progressive hypovolemia
Fig 4
Respiratory variations in the photoplethysmographic waveform amplitude (dPOP) during PEP and CPAP.
The effects of LBNP and level of respiratory resistance on dPOP. Boxplots of respiratory variations in POP from all observations in all subjects at each level of LBNP and respiratory resistance (left panel). Lines with ribbons are estimates and confidence intervals from the regression models (right panel). The slopes of the regression lines represent the change of dPOP with a change in LBNP. Note that as the linear regressions were performed on the loge-values of dPOP, the lines are curved on the original scale, as presented in the figure. dPOP: respiratory variations in the photoplethysmographic waveform, PEP: positive expiratory pressure, CPAP: continuous positive airway pressure, LBNP: lower body negative pressure.