Can a central blood volume deficit be detected by systolic p
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Abstract
Background
Whether during spontaneous breathing arterial pressure variations (APV) can detect a volume deficit is not established. We hypothesized that amplification of intra-thoracic pressure oscillations by breathing through resistors would enhance APV to allow identification of a reduced cardiac output (CO). This study tested that hypothesis in healthy volunteers exposed to central hypovolemia by head-up tilt.

Methods
Thirteen healthy volunteers were exposed to central hypovolemia by 45° head-up tilt while breathing through a facemask with 7.5 cmH2O inspiratory and/or expiratory resistors. A brachial arterial catheter was used to measure blood pressure and thus systolic pressure variation (SPV), pulse pressure variation and stroke volume variation . Pulse contour analysis determined stroke volume (SV) and CO and we evaluated whether APV could detect a 10 % decrease in CO.

Results
During head-up tilt SV decreased form 91 (±46) to 55 (±24) mL (mean?±?SD) and CO from 5.8 (±2.9) to 4.0 (±1.8) L/min (p?<?0.05), while heart rate increased (65 (±11) to 75 (±13) bpm; P?<?0.05). Systolic pressure decreased from 127 (±14) to 121 (±13) mmHg during head-up tilt, while SPV tended to increase (from 21 (±15)% to 30 (±13)%). Yet during head-up tilt, a SPV???37 % predicted a decrease in CO???10 % with a sensitivity and specificity of 78 % and 100 %, respectively.

Conclusion
In spontaneously breathing healthy volunteers combined inspiratory and expiratory resistors enhance SPV during head-up tilted induced central hypovolemia and allow identifying a 10 % reduction in CO. Applying inspiratory and expiratory resistors might detect a fluid deficit in spontaneously breathing patients....

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4982018/
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