The effect of left heart bypass on pulmonary blood flow and arterial oxygenation during one-lung ventilation in patients undergoing descending thoracic aortic surgery

Abstracts 

Study Objective

To study the effect of left heart bypass (LHB) on regional pulmonary blood flow and arterial oxygenation during one-lung ventilation (OLV).

Design

Prospective, observational study

Setting

Operating room

Patients

14 ASA physical status II and III patients scheduled to undergo descending thoracic or thoracoabdominal aortic surgery using LHB.

Interventions and Measurements

Parameters studied during OLV with 100% oxygen before and during LHB mean arterial pressure, heart rate, pulmonary artery pressure, pulmonary capillary wedge pressure, central venous pressure, cardiac index, cardiac output, arterial oxygen tension (PaO₂), mixed venous oxygen pressure, alveolar arterial oxygen difference (P_(A-a)O2), and right upper pulmonary venous flow (RUPVF). Right upper pulmonary venous flow was measured using transesophageal echocardiography.

Main Results

With the transition to OLV, there was a significant decrease in PaO₂ and a significant increase in P_(A-a)O2. However once LHB was initiated, these values improved significantly (P = 0.0007 and 0.0004, respectively) with the simultaneous increase in RUPVF (P = 0.0018).

Conclusions

LHB improved pulmonary blood flow to the dependent lung and arterial oxygenation during OLV in descending thoracic aortic surgery.

Keywords: Left heart bypass, One-lung ventilation, Oxygenation, Pulmonary blood flow