To the Editor,

In reference to the article published by Miao et al.,1 we would like to provide further insight into the practices of cuff pressure manometry in the context of the Canadian Anesthesiologists’ Society (CAS) guidelines.2 Miao demonstrated that 33/113 (29%) of endotracheal tube (ETT) cuffs and 8/14 (57%) of supraglottic airway (SGA) cuffs exceeded the recommended maximum pressures of 30 cmH2O and 60 cmH2O, respectively.3,4 Palpation of the pilot balloon was reported as the most common method to determine appropriate ETT cuff pressure. Fifty of 66 respondents (76%) reported using cuff manometry less than once per month.

We conducted a two-part study: 1) a prospective evaluation of intraoperative ETT and SGA cuff pressures at four Saskatchewan hospitals, and 2) a Canada-wide survey of anesthesiologists’ airway cuff management practices (see eAppendix, available as Electronic Supplementary Material). Research ethics board approval for both projects was obtained from the Regina Qu’Appelle Health Region and was exempted by the University of Saskatchewan Biomedical Research Ethics Board. Airway cuff pressures were measured in 101 patients aged 18 yr or older between April 2017 and January 2018. The primary study outcome was median ETT and SGA cuff pressures using a cuff manometer (VBM Medizintechnik GmbH, Sulz, Germany). We designed a survey regarding cuff pressure monitoring practices according to standardized recommendations for survey development including pre-testing, pilot testing, and clinical sensibility testing amongst anesthesia residents and staff anesthesiologists at our centre. The survey was then distributed to 1,661 CAS members.

Results from our practice audit found that the median [interquartile range (IQR)] SGA cuff pressure was 110 [62-120] cmH2O, markedly above the recommended safe upper limit of 60 cmH20 (P < 0.001).4 The median [IQR] ETT cuff pressure was 48 [25-65] cmH2O, also well above the recommended safe upper limit of 30 cmH20 (P < 0.001).3 ETT cuff pressures were within the proposed safe range (20–30 cmH2O) in only 7/60 (12%) cases.3 Supraglottic airway cuff pressures were below the recommended maximum in 10/41 (24%) cases, while 17/41 (41%) had cuff pressures above the measurable limit (120 cmH2O).4

Our survey had a response rate of 215/1661 (13%). Pilot balloon palpation was reported by 109 of 215 respondents (51%) as the technique used to estimate cuff pressure, while 101/215 (47%) reported using cuff manometry. This reported use may be an overestimate considering only 60% of centres had cuff manometers immediately available and only 24% and 42% of respondents could identify the recommended safe SGA and ETT cuff pressures (Table).3,4 Common reported barriers to cuff manometry use are the lack of availability, perceived lack of clinical evidence, and “laziness”.

Table Responses to survey questions
Full size table

In summary, knowledge translation regarding the importance and implementation of airway cuff pressure management is limited. Airway cuff pressures in clinical practice often exceed recommended safe limits and are underestimated by anesthesiologists. Manometers should be used routinely as cuff pressures inflated using other methods are typically outside the recommended range. Our study adds to Miao’s results by demonstrating that current clinical practice does not meet current guidelines and potentially exposes patients to harm.3,4,5 Our study offers some insight into the barriers to the regular use of cuff manometry, notably a common lack of availability.