Fig 1.
After instrumentation the measurements started with the subject in the supine position, followed by 30 and 70° head-up tilt with a 5 minute adjustment period in between (layer 1). Each test run encompasses three breathing conditions (layer 2, here only shown for the supine position) with and without an respiratory resistance (layer 3, here only shown for free breathing). The order of the breathing frequency and use of a respiratory resistance was randomized.
Table 1.
Hemodynamic and respiratory response to head-up tilt.
Table 2.
Pulse and systolic pressure variation (PPV and SPV) for nine different breathing conditions during the supine position and 30° and 70° head-up tilt.
Fig 2.
The influence of breathing frequency and respiratory resistance on pulse (PPV) and systolic pressure variation (SPV) during head-up tilt.
Black dot/triangle: mean value ± SD. *p<0.05 for SPV; †p<0.05 for PPV.
Fig 3.
Illustration of the effect of 6/min paced breathing against an expiratory resistance for a single recumbent subject.
AWF, airway flow; AWP, airway pressure; respCO2, respiratory CO2 partial pressure.
Fig 4.
ROC curve plots of pulse (PPV) and systolic pressure variation (SPV) during two different breathing conditions.
6/min paced breathing against an expiratory resistance significantly increased the area under the ROC curve of PPV (p = 0.047).