Can a central blood volume deficit be detected by systolic pressure variation during spontaneous breathing?

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.

Trial registration: ClinicalTrials.gov number NCT02549482 Registered September 10(th) 2015.

Keywords: Fluid responsiveness; Head-up tilt; Pulse pressure variation; Spontaneous breathing; Stroke volume variation; Systolic pressure variation.

Figures

Fig. 1

Left: four respiratory resistors: no resistance, expiratory resistance, inspiratory resistance, and both inspiratory and expiratory resistances. Right: facemask applied with combined inspiratory and expiratory resistors (Model photo)

Fig. 2

Three postures representing normovolemia (supine), central hypovolemia (head-up tilt), and central hypervolemia (head-down tilt)

Fig. 3

Receiver operating characteristic (ROC) curves during head-up tilt for systolic pressure variation (SPV) with the four different respiratory resistors. Area under the ROC curve 0.43 (0.10; 0.77 ) (confidence interval) for no resistor, 0.67 (0.25 ;1.00) for the inspiratory resistor, 0.70 (0.37; 1.00) for the expiratory resistor, and 0.96 (0.86; 1.00) for the combined inspiratory and expiratory resistor

Fig. 4

Receiver operating characteristic (ROC) curves during head-up tilt with the four different respiratory resistors. a: Pulse pressure variation (PPV) with area under the ROC curve 0.83 (0.61;1.00) (confidence interval) for no resistor, 0.73 (0.42;1.00) for the inspiratory resistor, 0.73 (0.40;1.00) for the expiratory resistor, and 0.59 (0.25;0.93) for the combined inspiratory and expiratory resistor. b: Stroke volume variation (SVV) with area under the ROC curve 0.73 (0.46;1.00) for no resistor, 0.75 (0.46;1.00) for the inspiratory resistor, 0.82 (0.58;1.00) for the expiratory resistor, and 0.58 (0.28;0.88) for the combined inspiratory and expiratory resistor. c: Central venous oxygen saturation (ScvO2) with area under the ROC curve 0.67 (0.29;1.00) for no resistor, 0.42 (0.00;0.88) for the inspiratory resistor, 0.46 (0.02;0.90) for the expiratory resistor, and 0.50 (0.08;0.92) for the combined inspiratory and expiratory resistor. d: Systolic blood pressure with area under the ROC curve 0.70 (0.37;1.00) for no resistor, 0.75 (0.46;1.00) for the inspiratory resistor, 0.68 (0.31;1.00) for the expiratory resistor, and 0.67 (0.34;0.99) for the combined inspiratory and expiratory resistor. e: Heart rate (HR) with area under the ROC curve 0.52 (0.08;0.95) for no resistor, 0.53 (0.11;0.96) for the inspiratory resistor, 0.68 (0.29;1.00) for the expiratory resistor, and 0.63 (0.22;1.00) for the combined inspiratory and expiratory resistor. f: Stroke volume (SV) with area under the ROC curve 0.63 (0.22;1.00) for no resistor, 0.70 (0.36;1.00) for the inspiratory resistor, 0.67 (0.25;1.00) for the expiratory resistor, and 0.60 (0.19;1.00) for the combined inspiratory and expiratory resistor