Positioning effects on arterial oxygen and relative pulmonary shunt in patients receiving mechanical ventilation after CABG

Abstract

Objective: To examine the effects of three different positions on arterial oxygen and relative pulmonary shunt in patients after coronary artery bypass graft (CABG) who are receiving mechanical ventilation with an effective tidal volume of 15 ml/kg and a minimum of 5 cm H2O positive end-expiratory pressure.

Design: Repeated measures, counterbalanced.

Setting: Adult cardiovascular intensive care unit in a major tertiary referral hospital.

Subjects: Convenience sample of 30 patients who had undergone CABG, 90% of whom had postoperative atelectasis.

Outcome measures: Partial pressure arterial oxygen (PaO2) and relative pulmonary shunt (areas of low ventilation-perfusion ratio).

Intervention: Supine, right lateral, and left lateral positions with head of bed elevated 30 degrees.

Results: No statistically significant differences in arterial oxygen and relative pulmonary shunt were found among the three positions.

Conclusions: For a selected cohort, positioning may not be an important consideration in arterial oxygenation in patients who have undergone CABG and are receiving mechanical ventilation with a high tidal volume and positive end-expiratory pressure.