https://orcid.org/0000-0001-5279-260X
Positive end-expiratory pressure (PEEP) is commonly applied to avoid atelectasis and improve oxygenation in patients during general anesthesia but affects cardiac pressures, volumes, and loading conditions through cardiorespiratory interactions. PEEP may therefore alter stroke work, which is the area enclosed by the pressure-volume loop and corresponds to the external work performed by the ventricles to eject blood. The low-pressure right ventricle may be even more susceptible to PEEP than the left ventricle. The authors hypothesized that increasing levels of PEEP would reduce stroke work in both ventricles.
This was a prospective, observational, experimental study. Six healthy female pigs of approximately 60 kg were used. PEEP was stepwise increased from 0 to 5, 7, 9, 11, 13, 15, 17, and 20 cm H2O to cover the clinical spectrum of PEEP. Simultaneous, biventricular invasive pressure-volume loops, invasive blood pressures, and ventilator data were recorded.
Increasing PEEP resulted in stepwise reductions in left (5,740 ± 973 vs. 2,303 ± 1,154 mmHg · ml; P < 0.001) and right (2,064 ± 769 vs. 468 ± 133 mmHg · ml; P < 0.001) ventricular stroke work. The relative stroke work reduction was similar between the two ventricles. Left ventricular ejection fraction, afterload, and coupling were preserved. On the contrary, PEEP increased right ventricular afterload and caused right ventriculo-arterial uncoupling (0.74 ± 0.30 vs. 0.19 ± 0.13; P = 0.01) with right ventricular ejection fraction reduction (64 ± 8% vs. 37 ± 7%, P < 0.001).
A stepwise increase in PEEP caused stepwise reduction in biventricular stroke work. However, there are important interventricular differences in response to increased PEEP levels. PEEP increased right ventricular afterload leading to uncoupling and right ventricular ejection fraction decline. These findings may support clinical decision-making to further optimize PEEP as a means to balance between improving lung ventilation and preserving right ventricular function.
Positive end-expiratory pressure (PEEP) is commonly applied to avoid atelectasis and improve oxygenation in patients undergoing mechanical ventilation during general anesthesia or while receiving intensive care unit care.
It is known that increased PEEP can decrease left ventricular stroke work, but it is not known how stepwise increases in PEEP correspond with biventricular cardiac function.
This study of six healthy, anesthetized female pigs found that stepwise increases in PEEP were associated with biventricular decreased stroke work as assessed using biventricular pressure-volume loop recordings.
Higher PEEP had divergent effects on right versus left ventricle for key hemodynamic variables including arterial elastance, ejection fraction, ventriculo-arterial coupling, and end-systolic pressures. The impact of PEEP was more notable and potentially detrimental for the right ventricle compared to the left ventricle.
