Mechanistic scheme and effect of "extended sigh" as a recruitment maneuver in patients with acute respiratory distress syndrome: a preliminary study

Crit Care Med. 2001 Jun;29(6):1255-60. doi: 10.1097/00003246-200106000-00037.


Objective: To devise a new form of sigh ("extended sigh") capable of providing a sufficient recruiting pressure x time, and to test it as a recruitment maneuver in patients with acute respiratory distress syndrome.

Design: Prospective uncontrolled clinical trial.

Setting: Medical intensive care unit of a university-affiliated hospital.

Patients: Twenty consecutive patients diagnosed with acute respiratory distress syndrome (18 men, 2 women, age 59 +/- 10 yrs).

Interventions: From baseline settings of tidal volume (Vt) 8 mL/kg and positive end-expiratory pressure (PEEP) 10 cm H2O on volume control mode with the high pressure limit at 40 cm H2O, the Vt-PEEP values were changed to 6-15, 4-20, and 2-25, each step being 30 secs (inflation phase). After Vt-PEEP 2-25, the mode was switched to continuous positive airway pressure of 30 cm H2O for a duration of 30 secs (pause), after which the baseline setting was resumed following the reverse sequence of inflation (deflation phase). This extended sigh was performed twice with 1 min of baseline ventilation between.

Measurements and results: Airway pressures and hemodynamic parameters were traced at each step during the extended sigh. Arterial blood gases and physiologic parameters were determined before the extended sigh (pre-extended sigh), at 5 mins after two extended sighs (post-extended sigh), and then every 15 mins for 1 hr. In our average patient, the recruiting pressure x time of the inflation phase was estimated to be 32.8-35.4 cm H2O x 90 secs. Compared with the inflation phase, inspiratory pause pressure of the deflation phase was lower at Vt-PEEP 6-15 (28.9 +/- 2.7 cm H2O vs. 27.3 +/- 2.8 cm H2O) and 4-20 (31.8 +/- 2.9 cm H2O vs. 31.1 +/- 2.9 cm H2O; both p <.05). Compared with pre-extended sigh, Pao2 (81.5 +/- 15.3 mm Hg vs. 104.8 +/- 25.0 mm Hg; p <.001) and static respiratory compliance both increased post-extended sigh (27.9 +/- 7.9 mL/cm H2O vs. 30.2 +/- 9.7 mL/cm H2O; p =.009). Improvement in these parameters was sustained above pre-extended sigh for the duration of the study. Major hemodynamic or respiratory complications were not noted during the study.

Conclusion: We present a new form of sigh (i.e., extended sigh) capable of achieving an augmented recruiting pressure x time through a prolonged inflation on a gradually increased end-expiratory pressure. In view of the sustained effect and absence of major complications in our patients, extended sigh could be a useful recruitment maneuver in acute respiratory distress syndrome.

Publication types

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

MeSH terms

  • Airway Resistance
  • Female
  • Hemodynamics
  • Humans
  • Intensive Care Units
  • Male
  • Middle Aged
  • Oxygen / metabolism
  • Positive-Pressure Respiration
  • Prospective Studies
  • Respiratory Distress Syndrome / physiopathology*
  • Respiratory Mechanics / physiology*
  • Statistics, Nonparametric
  • Tidal Volume


  • Oxygen