Compressing the non-dependent lung during one-lung ventilation improves arterial oxygenation, but impairs systemic oxygen delivery by decreasing cardiac output

Abstract

Although non-dependent lung compression may be a potentially effective measure to treat hypoxemia during OLV, it should be noted that CO and systemic oxygen delivery may be decreased by this maneuver.

Co-administration of ephedrine prevents reductions in cardiac output and systemic oxygen delivery secondary to lung compression maneuvers during one-lung ventilation, without reducing arterial oxygenation

“…The most likely explanation for changes in arterial oxygenation after compression of the nondependent lung is the diversion of blood flow to the dependent lung by physical compression and kinking of the lung vessels. However, our recent follow-up study using a minimally invasive CO monitor suggested that nondependent lung compression reduced DO 2 despite improvement in arterial oxygen saturation [12]. Because the decrease in DO 2 was mainly caused by the reduction of CO associated with the compression of the nondependent lung [12], we aimed to maintain CO without compromising arterial oxygenation in the present study.…”

“…However, our recent follow-up study using a minimally invasive CO monitor suggested that nondependent lung compression reduced DO 2 despite improvement in arterial oxygen saturation [12]. Because the decrease in DO 2 was mainly caused by the reduction of CO associated with the compression of the nondependent lung [12], we aimed to maintain CO without compromising arterial oxygenation in the present study. Ephedrine was selected as an inotropic agent because it anecdotally had been found to be effective in case of hypotension during lung retractor application in our institution, but also because of its favorable pharmacodynamic and safety profile.…”

“…Even though the effects of repetitive nondependent lung compression on arterial oxygen partial pressure may be long lasting [17], the effects of a single nondependent lung compression on hemodynamic parameters and arterial oxygen saturation may be observed for only a couple of minutes [12]. We therefore chose to use a more vigorous inotropic effect that could be obtained by a single bolus administration of ephedrine rather than that gradually exerted by an increasing continuous intravenous infusion of dopamine for the purpose of proving our hypothesis.…”

“…Application of the retractor is usually accompanied by a decrease in blood pressure [12]. Hemodynamic parameters were managed differently during the first 5 min after application of the lung retractor than the rest of the study period, where SBP was maintained within 20% of the baseline value.…”

“…Based on these findings, we advocated that nondependent lung compression may be used as a measure to improve arterial oxygenation (PaO 2 ) in patients during OLV [11]. However, we later found that cardiac output (CO) and systemic oxygen delivery (DO 2 ) were impaired by this technique, presumably because of direct cardiac compression by the retractor, restriction of vena cava preload, or right ventricular impairment caused by high pulmonary vascular resistance [12].…”