Size of Cuff Leak Predicts Post-Extubation Stridor
February 1, 1997 3 minutes read
Size of Cuff Leak Predicts Post-Extubation Stridor
Abstract & Commentary
Synopsis: When ventilated prior to extubation with a deflated endotracheal tube cuff, patients who subsequently developed post-extubation stridor had half the measured air leak of those who did not develop stridor.
Source: Miller RL, et al. Chest 1996;110:1035-1040.
One of the complications of weaning and extubating patients after a period of mechanical ventilation is that some patients develop immediate upper airway obstruction from airway edema. Treatment of this complication includes high-dose steroids and racemic epinephrine inhalation. Occasionally, reintubation is required to prevent fatal airway obstruction. Qualitative evaluation of the presence of a leak around the tube during a sustained inflation with the endotracheal tube cuff deflated has been suggested as a way of identifying patients at risk of this problem, with a small or no leak predicting problems with obstruction. Miller et al have proposed an easy way to quantitate the degree of leak and have shown that those with smaller leaks are more likely to have post-extubation stridor.
One hundred consecutive intubations in 88 patients were studied. Each day, a leak volume was determined. This volume was determined by placing the patient on assist/control ventilation with other parameters as set by the individual clinician. After suctioning of tracheal and oral secretions, the endotracheal tube cuff was deflated and, after 4-6 breaths, the difference between inhaled and exhaled tidal volume calculated and corrected for body temperature, barometric pressure, and humidity (Puritan-Bennett 7200 ventilator).
Post-extubation stridor developed in six patients with an average cuff leak of 180 mL ± 156 mL compared to 360 mL ± 157 mL in those not developing stridor (P = 0.012). This included two patients who experienced unplanned extubation, one in each group, who removed their own tubes with the cuffs inflated. When only the planned extubations were included, the difference became even more marked, 115 mL ± 96 mL leak in those with stridor, 355 mL ± 153 mL without stridor (P = 0.0014). Patients with a leak volume of 110 mL or less had an 80% chance of developing stridor, those with greater than 110 mL had a 98% chance of not developing stridor. Excluding the self-extubations increased the sensitivity from 67% to 80%.
COMMENT BY CHARLES G. DURBIN, Jr., MD, FCCM
Identification of patients likely to develop postextubation stridor is important because prevention and treatment may be possible. These patients may need reintubation to prevent fatal airway obstruction. In this study, half of the patients with stridor required reintubation.
Evaluation of the degree of air leak around a deflated cuff has been a subjective observation. The absence of any leak has been associated with development of stridor; however, the details of the "leak test" are usually not specified (i.e., airway pressure, sedated vs paralyzed patient). These authors have introduced an easily reproducible way of performing a quantitative analysis of leak. Because the number of patients that developed stridor was small, larger series must be studied to confirm the ease and use of this evaluation method. The use of other ventilators to make the measurements and use in different groups of patients will determine if this method is universally applicable and should become "a standard extubation criterion," much like vital capacity or negative inspiratory pressure measurement.
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