Positive End-expiratory Pressure Is Associated With Apparent Increases in Single-beat Left-ventricular End-systolic...

Single-beat estimates of left-ventricular end-systolic elastance (Ees) and ventriculoarterial coupling are increasingly used in perioperative and critical care settings. However, their presumed load independence may not hold during ventilatory interventions. This study was designed to investigate the effect of graded positive end-expiratory pressure (PEEP) on these estimates.

Prospective observational study.

Single tertiary-care hospital.

A total of 105 adults undergoing elective noncardiac surgery under general anesthesia.

PEEP was increased stepwise (0, 5, 10, and 15 cmH₂O) during controlled mechanical ventilation.

Transthoracic echocardiography and invasive arterial pressure were recorded at each PEEP level. Single-beat Ees, Ea, and Ea/Ees were calculated using the Chen method and analyzed using linear mixed-effects models. For each 5 cmH₂O increase in PEEP, Ees increased by 0.55 mmHg/mL (95% confidence interval [CI]: 0.49 to 0.61; p < 0.001), Ea increased by 0.24 mmHg/mL (95% CI: 0.20 to 0.27; p < 0.001), and Ea/Ees decreased by 0.04 (95% CI: -0.05 to -0.03; p < 0.001). Stroke volume decreased by 9.1 mL (95% CI: -9.9 to -8.4; p < 0.001), whereas heart rate remained unchanged. In sensitivity analyses, the apparent increase in Ees disappeared when assuming a stroke volume at PEEP of 0 cmH₂O but persisted when assuming baseline-estimated normalized ventricular elastance at arterial end-diastole or applying transmural pressure correction.

Apparent increases in single-beat left-ventricular Ees during PEEP titration were consistent with substantial stroke volume-related mathematical sensitivity of the single-beat formulation. These findings suggest that such increases should not be interpreted as direct evidence of improved left-ventricular systolic function.