A randomized controlled trial of positive end-expiratory pressure on pulmonary oxygenation and biventricular function in esophageal cancer patients receiving one-lung ventilation under a lower FiO2

Abstract

Background: Arterial oxygenation is often impaired during one-lung ventilation (OLV), due to both pulmonary shunt and atelectasis. Lower fraction of inspiration O₂ (FiO₂) may reduce inflammation and complications, but may increase the risk of hypoxemia. The aim of this randomized controlled parallel trial was to analyze whether higher positive end-expiratory pressure (PEEP) could improve oxygenation and maintain lower levels of inflammation during OLV under a lower FiO₂.

Methods: One hundred and twenty patients with selective thoracotomy for esophageal cancer (EC) were classified randomly into four groups on a ratio of 1:1:1:1 using a computer-generated list, including Group A (FiO₂ =0.6, PEEP =0), Group B (FiO₂ =0.6, PEEP =5 cmH₂O), Group C (FiO₂ =1.0, PEEP =8 cmH₂O), and Group D (FiO₂ =1.0, PEEP =10 cmH₂O). The oxygenation and pulmonary shunt were primary outcomes. Haemodynamics, respiratory mechanics, serum IL-6 and IL-10 levels, and complications were taken as secondary outcomes. Follow-up was terminated until discharge.

Results: Two patients in Group A and two in Group D were excluded due to hypoxemia and hypotension, respectively. Then the data of 116 patients (Group A =28, Group B =30 Group C =30, and Group D =28) were assessed for final analysis. Compared with Group B, the partial pressure of oxygen (PaO₂) and dynamic compliance during OLV in Group D were significantly increased from 15 minutes to 60 minutes, while pulmonary shunt was significantly decreased (P>0.05). Patients in Group D had higher levels of central venous pressure (CVP) and airway pressure (Paw) during OLV and higher levels of IL-6 and IL-10 after OLV compared with Group B (P>0.05). No statistical differences were found in oxygen saturation (SaO₂), PvO₂ (partial pressure of oxygen in venous blood), partial pressure of end-tidal carbon dioxide (ETCO₂), partial pressure of carbon dioxide in artery (PaCO₂), heart rate (HR), mean arterial pressure (MAP), and complications among the four groups (P>0.05).

Conclusions: Higher PEEP increased the oxygenation under 60% O₂ during OLV. However, the haemodynamics and respiratory mechanics changed, and the levels of inflammation increased. A higher PEEP under 60% O₂ during OLV is not recommended.

Trial registration: Chinese Clinical Trial Registry ChiCTR1900024726.

Keywords: Positive end-expiratory pressure (PEEP); low FiO2; one-lung ventilation.

Figure 1

Flowchart for the randomized controlled trial. FiO₂, fraction of inspiration O₂; PEEP, positive end-expiratory pressure.

Figure 2

Dynamic changes of PaO₂ and Qs/Qt among EC patients during OLV in four groups. Comparison of the level of PaO₂ (A) and Qs/Qt (B) in Group A, Group B, Group C, and Group D at pre-OLV (T1), OLV 10 minutes (T2), OLV 15 minutes (T3), OLV 30 minutes (T4), OLV 60 minutes (T5), and OLV 120 minutes (T6). *, P<0.05 (compared with Group B). PaO₂, partial pressure of oxygen; Qs/Qt, pulmonary shunt; EC, esophageal cancer. OLV, one-lung ventilation.

Figure 3

Dynamic changes of dynamic compliance, CVP, and Paw among EC patients during OLV in four groups. Comparison of the levels of dynamic compliance (A) CVP (B) and Paw (C) in Group A, Group B, Group C, and Group D at pre-OLV (T1), OLV 10 minutes (T2), OLV 15 minutes (T3), OLV 30 minutes (T4), OLV 60 minutes (T5), and OLV 120 minutes (T6). *, P<0.05 (compared with Group B). CVP, central venous pressure; Paw, airway pressure; EC, esophageal cancer; OLV, one-lung ventilation.

Figure 4

Serum IL-6 and IL-10 levels among EC patients in four groups. Comparison of serum IL-6 (A) and IL-10 levels (B) in Groups A, B, C, and D at T1 (pre-OLV), T5 (OLV 60 minutes), T7 (30 minutes after switching back to TLV), and T8 (24 hours post-operation). *, P<0.05 (compared with Group C); ^#, P<0.05 (compared with Group D). EC, esophageal cancer; OLV, one-lung ventilation; TLV, two-lung ventilation.