Endotracheal tube cuff pressures – still a problem!
Endotracheal intubation for mechanical ventilation has a central role in the intensive care unit (ICU), but is associated with numerous complications. One serious – but largely preventable – complication is tracheal stenosis, secondary to excessive pressure in the cuff of the endotracheal or tracheostomy tube. The high pressure in the cuff compresses the mucosa against the rigid tracheal cartilage rings, resulting in mucosal damage and ischaemic necrosis.1 Fibrotic healing of this lesion leads to the gradual stenosis of a section of the trachea. Patients may present weeks to months after discharge from the ICU when obstruction in the trachea reaches a critical degree. Stenosis may also make subsequent intubation of the trachea impossible. Other complications of high cuff pressure (Pcuff) range from frequent sore throat to rare but disastrous events such as tracheo-oesophageal fistula.2
In the early days of critical care, rubber endotracheal tubes were used with high-pressure, low-volume cuffs that inevitably transmitted a high pressure to the tracheal wall when inflated to occlusive pressures. Large-volume, low-pressure cuffs were developed, which could occlude the trachea at low pressure, but the same complication occurs if a pressure >30 cmH2O is applied for any length of time.3
Too low a Pcuff, however, results in decreased ventilation due to leakage and a risk of aspiration. A Pcuff of <20 cmH2O is associated with an increased incidence of ventilator-associated pneumonia.4 A recent observational study has suggested that combining continuous Pcuff control with subglottic drainage reduces the incidence of ventilator-associated pneumonia.5
This Journal recently published a survey of ICU nurses by Jordan et al.,6 which showed that only 22% of nurses were aware of the recommended pressure range (25 - 30 cmH2O) and that Pcuff measurements were performed less frequently than 6-hourly by more than half the respondents. Another report from Cape Town noted an increased incidence of tracheal stenosis following mechanical ventilation, and found, in a snap survey of ICUs, that Pcuffs exceeded 30 cmH2O in 30% of patients.7
In this issue, Memela and Gopalan8 report on their study of continuous Pcuff measurement. Although the mean Pcuff values were in the acceptable range, and there was no difference between the means of the intermittent pressure readings and the continuous readings, the continuous readings revealed that patients spent an average of 13% of the time below the acceptable range and 23% of the time above the acceptable range. Indeed, one patient was exposed to high pressures, averaging 66 cmH2O, for the whole of the study period!
The failure to maintain safe Pcuffs seems to be a particular problem, even in units that otherwise provide excellent critical care nursing. Suggested reasons include the lack of appropriate pressure gauges, the widespread use of agency staff, and the lack of clear, evidence-based protocols.7 Another reason could be that bedside nurses are focused on the clear and present dangers of aspiration and hypoventilation, and regard tracheal stenosis as a remote and theoretical event.
Whatever the reasons, awareness of the problem is growing. Simple aneroid pressure gauges are not expensive and there is no good reason not to monitor Pcuffs on all intubated patients continuously, in order to maintain them in the 25 - 30 cmH2O range, and to document this at least 4-hourly.
1. Cooper JD, Grillo HC. The evolution of tracheal injury due to ventilatory assistance through cuffed tubes: A pathologic study. Ann Surg 1969;169(3):334-348.
2. Streitz JM Jr, Shapshay SM. Airway injury after tracheotomy and endotracheal intubation. Surg Clin North Am 1991;71(6):1211-1230.
3. Seegobin RD, van Hasselt GL. Endotracheal cuff pressure and tracheal mucosal blood flow: Endoscopic study of effects of four large volume cuffs. BMJ 1984;288(6422):965-968.
4. Rello J, Sonora R, Jubert P, et al. Pneumonia in intubated patients: Role of respiratory airway care. Am J Respir Crit Care Med 1996;154(1):111-115.
5. Lorente L, Lecuona M, Jiménez A, Cabrera J, Mora ML. Subglottic secretion drainage and continuous control of cuff pressure used together save health care costs. Am J Infect Control 2014;42(10):1101-1105. [http://dx.doi.org/10.1016/j.ajic.2014.06.028]
6. Jordan P, van Rooyen D, Venter D. Endotracheal tube cuff pressure management in adult critical care units. South African Journal of Critical Care 2012;28(1):15-19.
7. Raynham OW, Lubbe DE, Fagan JJ. Tracheal stenosis: Preventable morbidity on the increase in our intensive care units. S Afr Med J 2009;99(9):645-656.
8. Memela ME, Gopalan DP. Variations in endotracheal tube cuff pressure: Is 8-hourly monitoring enough? South African Journal of Critical Care 2014;30(2):35-40. [http://dx.doi.org/10.7196/SAJCC.159]
S Afr J Crit Care 2014;30(2):34. DOI:10.7196/SAJCC.221
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