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

Abstract

We have previously found that compression of the non-dependent lung improves arterial oxygenation during one-lung ventilation (OLV) in patients undergoing esophagectomy. The purpose of this study was to investigate the effects of compression of the non-dependent lung on hemodynamic indices and oxygen delivery using a minimally invasive cardiac output (CO) monitor. Sixteen consecutive patients undergoing esophagectomy through a right thoracotomy were studied. Under general anesthesia, a left-sided double-lumen tube was placed for OLV, and the dependent lung was mechanically ventilated with a tidal volume of 8 ml kg(-1) body weight and a fraction of inspiratory oxygen of 0.8 during OLV. CO was monitored continuously using a FloTrac/Vigileo (Edwards Lifesciences) system. Surgeons compressed the non-dependent lung several times during surgery using a lung retractor to improve exposure of the surgical field. The oxygen delivery index was roughly estimated as the product of the cardiac index (CI) and arterial oxygen saturation as monitored by pulse oximetry (Spo2). Just before non-dependent lung compression, mean (+/- SD) CI and Spo2 were 2.6 +/- 0.6 L min(-1) m(-2) and 95.0 +/- 3.9%, respectively. At 1 min after non-dependent lung compression, Spo2 increased significantly to 97.8 +/- 2.2% (P < 0.05), but CI decreased significantly to 2.0 +/- 0.4 L min(-1) m(-2) (P < 0.05). The product of CI and Spo2 at 1 min was significantly lower (192.7 +/- 37.3) than baseline levels (250.5 +/- 66.3, P < 0.05). 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.