“Cuffs were considered overinflated above 25 cm of water,” continued Dr. Morris. “This can lead to tracheal injury, such as ciliary loss and mucosal injury to the basement membrane, in as little as two hours after intubation.” In this study, 44 cuffs (38%) were overinflated and 22 cuffs (19%) were severely overinflated (>40 cm H2O).
At Hospital A, 24 of 63 cuffs (38%) were overinflated and at Hospital B, 20 of 52 cuffs (38%) were overinflated. “Surprisingly, there was absolutely no difference in rates of overinflation between the two hospitals,” said Dr. Morris, even though studies have suggested that manometry is a more reliable method of cuff assessment than digital palpation.
This may be due to several factors. Members of the health care team may have readjusted the cuffs when they responded to ventilator alarms, perceived air leaks, or concern for aspiration. Additionally, cuff pressures might have changed throughout the day, as the tube migrated with patient repositioning or suctioning or because of air leaking out of the cuff. This may have led to increased or decreased cuff pressure, which might have triggered an air leak alarm and lead to further inflation by a physician or nurse.
Mean cuff pressures were 26.2 cm H2O (median, 22.0 cm H2O) at Hospital A and 25.3 cm H2O (median, 21.0 cm H2O) at Hospital B. Among endotracheal tubes, 29 of 68 (43%) were overinflated, compared with 15 of 47 (32%) of tracheotomy tubes. The mean orotracheal tube cuff pressure was 27.0 cm H2O and the mean tracheotomy tube cuff pressure was 24.0 cm H2O, indicating that both are equally likely to be overinflated. There was also no difference in rates of severe overinflation.
“This study reports a 38% incidence of overinflation,” said Dr. Morris. “While this number is slightly lower than those from international studies, it remains high and reflects a significant number of patients in our institutions’ ICUs at risk for tracheal injury.”
Strategies for Improving Outcomes
Possible strategies for improvement in outcomes include more frequent manometric assessment by trained respiratory therapists, since cuff pressures change and tubes are adjusted throughout the day, and education of physicians and nurses on cuff pressure management and sequelae of overinflation.
As the use of manometry to assess cuff pressures did not reduce the incidence of overinflation in this study, Dr. Morris suggested that a more vigilant management protocol, which also monitors tracheotomy tubes, may be necessary. “Most hospitals have protocols for the monitoring of tracheal tube cuff pressures and most respiratory therapists and critical care specialists—especially anesthesiologists—are very aware of this issue, even though they may not have received formal training in the subject. Ironically, nobody has ever attempted to determine if these protocols actually work and we should, at the very least, periodically assess whether their protocols are meeting the desired targets,” said Dr. Morris.
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