Comparison of the lower inflection point on the static total respiratory compliance curve with outcomes in postoperative cardiothoracic patients.

BACKGROUND

Routine use of positive end-expiratory pressure (based on the pressure at the lower inflection point on the static total respiratory compliance curve) along with a maneuver to recruit atelectatic lung has been advocated after cardiothoracic surgery.

OBJECTIVES

To determine if the lower inflection point is related to outcomes in patients after sternotomy and cardiopulmonary bypass.

METHOD

A prospective observational study involving estimation of the lower inflection point on the inflation pressure-volume plot obtained with a low-flow technique. Duration of intubation, length of stay, respiratory complications, and results of spirometry were compared between patients with a "high " inflection point (> or =10 cm H2O) and patients with a "low" inflection point (< or =5 cm H2O).

RESULTS

Ninety-five patients were enrolled. After exclusion for incomplete data, 65 patients (49 men, 16 women; mean age, 66.1 years; SD, 9.5 years) were included. The mean lower inflection point was 6.33 cm H2O (SD, 3.4 cm H2O). A second lower inflection point was observed on 5 plots (mean, 21 cm H2O; SD, 1.4 cm H2O). Nine patients had high inflection points (mean, 13.1 cm H2O; SD, 3.0 cm H2O), and 33 had low inflection points (mean, 3.9 cm H2O; SD, 0.98 cm H2O). No outcome measures differed between groups.

CONCLUSIONS

In patients with short intubation times and predictable postoperative course, general use of a lung recruitment strategy involving sustained inflations and adjustment of positive end-expiratory pressure based on the lower inflection point is difficult to justify.