Hemodynamic and respiratory changes during lung recruitment and descending optimal positive end-expiratory pressure titration in patients with acute respiratory distress syndrome

Crit Care Med. 2007 Mar;35(3):787-93. doi: 10.1097/01.CCM.0000257330.54882.BE.

Abstract

Objectives: To investigate respiratory and hemodynamic changes during lung recruitment and descending optimal positive end-expiratory pressure (PEEP) titration.

Design: Prospective auto-control clinical trial.

Setting: Adult general intensive care unit in a university hospital.

Patients: Eighteen patients with acute respiratory distress syndrome.

Interventions: Following baseline measurements (T0), PEEP was set at 26 cm H2O and lung recruitment was performed (40/40-maneuver). Then tidal volume was set at 4 mL/kg (T26R) and PEEP was lowered by 2 cm H2O in every 4 mins. Optimal PEEP was defined at 2 cm H2O above the PEEP where Pao2 dropped by > 10%. After setting the optimal PEEP, the 40/40-maneuver was repeated and tidal volume set at 6 mL/kg (T(end)).

Measurements and main results: Arterial blood gas analysis was done every 4 mins and hemodynamic measurements every 8 mins until T(end), then in 30 (T30) and 60 (T60) mins. The Pao2 increased from T0 to T(end) (203 +/- 108 vs. 322 +/- 101 mm Hg, p < .001), but the extravascular lung water (EVLW) did not change significantly. Cardiac index (CI) and the intrathoracic blood volume (ITBV) decreased from T0 to T26R (CI, 3.90 +/- 1.04 vs. 3.62 +/- 0.91 L/min/m2, p < .05; ITBVI, 832 +/- 205 vs. 795 +/- 188 m/m2, p < .05). There was a positive correlation between CI and ITBVI (r = .699, p < .01), a negative correlation between CI and central venous pressure (r = -.294, p < .01), and no correlation between CI and mean arterial pressure (MAP).

Conclusions: Following lung recruitment and descending optimal PEEP titration, the Pao2 improves significantly, without any change in the EVLW up to 1 hr. This suggests a decrease in atelectasis as a result of recruitment rather than a reduction of EVLW. There is a significant change in CI during the maneuver, but neither central venous pressure, heart rate, nor MAP can reflect these changes.

Publication types

  • Controlled Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Air Pressure
  • Blood Pressure / physiology
  • Blood Volume / physiology*
  • Cardiac Output / physiology*
  • Central Venous Pressure / physiology
  • Extravascular Lung Water / physiology
  • Female
  • Heart Rate / physiology
  • Hospitals, University
  • Humans
  • Lung / physiopathology*
  • Male
  • Middle Aged
  • Oxygen / blood*
  • Positive-Pressure Respiration / methods*
  • Pulmonary Alveoli / physiopathology
  • Pulmonary Atelectasis / physiopathology
  • Pulmonary Atelectasis / therapy
  • Pulmonary Ventilation / physiology*
  • Respiratory Distress Syndrome, Adult / physiopathology*
  • Respiratory Distress Syndrome, Adult / therapy
  • Stroke Volume / physiology*
  • Tidal Volume / physiology*

Substances

  • Oxygen