title: Left ventricular contractility using isovolumic phase indices during PEEP in ARDS patients.
abstract: The effects of incremental increases in PEEP during mechanical ventilation on left ventricular (LV) contractility before and after intravascular volume expansion (IVE) were studied in 10 patients treated for ARDS. A pulmonary artery (PA) catheter, a LV catheter-tip micromanometer, and an esophageal balloon catheter were inserted in these patients. We measured transmural right atrial and PA pressures, transmural LV end-diastolic and systemic arterial pressures, the first derivative of LV pressure (LV dP/dt), the ratio of LV dP/dt at transmural developed LV pressure (dP/dt/DPt) with DPt = 5, 10, 40 mm Hg, cardiac index (CI) at every level of PEEP and after IVE at the highest PEEP. Stepwise increases in PEEP (from 0-20 cm H2O) were associated with progressive fall in CI whereas heart rate remained unchanged. Transmural right atrial and PA pressures did not change; transmural LV end-diastolic and systemic arterial pressures and peak dP/dt decreased significantly with PEEP, except for dT/dt/dPt. IVE reversed this fall in CI and peak dP/dt. Whereas transmural LV end-diastolic pressure rose markedly. We conclude that the observed fall in LV performance during PEEP is not the result of a depressed LV contractility because PEEP does not induce a decrease in dP/dt/DPt, the least sensitive to change in preload isovolumic phase indices of contractility.
mesh_terms: D000328:Adult; D001810:Blood Volume; D005260:Female; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008875:Middle Aged; D009200:Myocardial Contraction; D011175:Positive-Pressure Respiration; D011312:Pressure; D012128:Respiratory Distress Syndrome / Q000503:physiopathology / Q000628:therapy*