Landmark Papers in Critical Care: the duration of mechanical ventilation

Ely EW, et al. Effect on the duration of mechanical ventilation of identifying patients capable of breathing spontaneously. N Engl J Med 1996;335:1864-9.

Question: There are no hard and fast rules about when to extubate patients. Could screening them daily with certain criteria lead to earlier and more appropriate extubations?

300 patients who had been ventilated for less than 2 weeks at the time of enrollment underwent daily screening by a respiratory therapist. The screening standards included:

  • Ratio of PaO2: FiO2 >200
  • PEEP could not exceed 5 cm H2O
  • Adequate cough reflex during suctioning
  • Ratio of respiratory frequency to the tidal volume could not exceed 105 breaths/min/L
  • No infusions of vasopressor agents or sedatives could be used (dopamine could be given in doses not exceeding 5 μg per kilogram of body weight per minute, and intermittent dosing of sedatives was allowed).

Patients in the intervention group who met this criteria underwent a trial of spontaneous breathing (were extubated). They had to maintain the same level of FiO2 and PEEP for two hours. They were considered to have failed the spontaneous breathing trial (SBT) if:

  • Respiratory rate > 35
  • O2 sat <90%
  • Heart rate >140 or changed by over 20%,
  • Blood pressure >180 or < 90 mm Hg
  • Increased anxiety or diaphoresis

If the patient did not tolerate the trial, they were re-intubated and the whole process was repeated on subsequent days.

The intervention group that got screenings was given an SBT, on average, 1 day earlier than the control group and was ventilated for 4.5 days (p=0.003), compared to the control group, which was ventilated for a median of 6 days. The intervention group also had fewer complications than the controls (p=0.001) including fewer reintubations and ventilation >21 days.

There were no significant differences between groups in the number of days of intensive care or overall hospitalization, although cost of care for the intervention group was lower (p<0.04).

Also of some amusement was this quote:

Our observations also underscore the key role of nonphysician health professionals in providing safe, efficient ventilatory care. During the study, the commitment of time by physicians appeared minimal, since most monitoring was done by respiratory therapists and nurses as part of their standard patient care.

Bottom line: This RCT shows that daily screening and SBT can reduce the number of days that a patient is mechanically ventilated for, and leads to earlier and more appropriate extubation, fewer medical complications, and a less costly hospital stay.

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