ENDOTRACHEAL TUBE CUFF PRESSURE BEFORE, DURING, AND AFTER

FIXED-WING AIR MEDICAL RETRIEVAL

Peter Brendt, MD, FANZCA, Marc Schnekenburger, MD, Karen Paxton, Anthony Brown, MD,FAFPHM, FAFOEM, Kumara Mendis, MD

Abstract

Background. Increased endotracheal tube (ETT) cuff pres-sure is associated with compromised tracheal mucosal per-fusion and injuries. No published data are available forAustralia on pressures in the fixed-wing air medical re-trieval setting. Objective. After introduction of a cuff pres-sure manometer (Mallinckrodt, Hennef, Germany) at theRoyal Flying Doctor Service (RFDS) Base in Dubbo, NewSouth Wales (NSW), Australia, we assessed the prevalence ofincreased cuff pressures before, during, and after air medicalretrieval. Methods. This was a retrospective audit in 35 ven-tilated patients during fixed-wing retrievals by the RFDS inNSW, Australia. Explicit chart review of ventilated patientswas performed for cuff pressures and changes during med-ical retrievals with pressurized aircrafts. Pearson correlationwas calculated to determine the relation of ascent and ETTcuff pressure change from ground to flight level. Results. Themean (± standard deviation) of the first ETT cuff pressuremeasurement on the ground was 44 ± 20 cmH2O. Prior to re-trieval in 11 patients, the ETT cuff pressure was >30 cmH2Oand in 11 patients >50 cmH2O. After ascent to cruising alti-tude, the cuff pressure was >30 cmH2O in 22 patients and>50 cmH2O in eight patients. The cuff pressure was reduced1) in 72% of cases prior to take off and 2) in 85% of cases dur-ing flight, and 3) after landing, the cuff pressure increasedin 85% of cases. The correlation between ascent in cabin al-titude and ETT cuff pressure was r = 0.3901, p = 0.0205.Conclusions. The high prevalence of excessive cuff pressuresduring air medical retrieval can be avoided by the use of cuff

Received July 14, 2012, from Royal Flying Doctor Service Australia,South Eastern Section (PB, MS), Dubbo, NSW, Australia; and theSchool of Rural Health Dubbo, University of Sydney (PB, MS, KP,AB, KM), Dubbo, NSW, Australia. Revision received August 20,2012; accepted for publication September 5, 2012; published onlineDecember 19, 2013.

Dr. Brendt is currently at the Klinik fur Anasthesiologie und Inten-sivmedizin, Universitatsklinikum Essen, Essen, Germany; and Dr.Schnekenburger is currently at the Emergency & Trauma CentreAlfred Hospital, Melbourne, VIC, Australia.

The authors report no conflicts of interest. The authors alone are re-sponsible for the content and writing of the paper.

Address correspondence and reprint requests to: Dr. med. PeterBrendt, Klinik fur Anasthesiologie und Intensivmedizin, Univer-sitatsklinikum Essen, Hufelandstr. 55, D-45122 Essen, Germany.e-mail: p.brendt@web.de

doi: 10.3109/10903127.2012.744787

pressure manometers. Key words: cuff pressure; air medicalretrieval; prehospital

PREHOSPITAL EMERGENCY CARE 2013;17:177–180

INTRODUCTION

In the prehospital setting, endotracheal intubationprior to transport is a common practice performed bydoctors or paramedics. When the endotracheal tube(ETT) cuff pressure exceeds 30 cmH2O, tracheal mu-cosal perfusion starts to be compromised. Increasedcuff pressures above 40 cmH2O prior to transport orto the arrival in the emergency department have beenreported from different retrieval services.1–3 When thecuff pressure exceeds 50 cmH2O, a critical perfusionpressure is reached. Tracheal injury may occur afteras little as 15 minutes.4 Furthermore, high-altitude airmedical transport is a significant risk factor for la-ryngeal nerve injury due to increased cuff pressure.5

During ascent in altitude of the air medical retrievalaircraft, barometric pressure in the cabin decreasesand therefore the cuff volume rises. In vivo6 and invitro,7 this altitude-related increase in ETT cuff pres-sure above the critical value of 50 cmH2O has been ob-served.

The Royal Flying Doctor Service (RFDS) South East-ern Section in Dubbo, New South Wales, Australia,provides emergency retrievals using Beechcraft B200King Air twin turboprop aircrafts usually cruisingfrom 15,000 to 25,000 feet. The aircraft cabin is pres-surized, and medical retrievals are conducted with acabin pressure around 3,000 feet above sea level. ETTcuff pressure manometers (Mallinckrodt, Hennef, Ger-many) were introduced in 2010 to improve our patientcare. To integrate the use of these new devices into clin-ical practice, flight nurses and doctors had to fill outa ventilation documentation sheet when the patientwas handed over to or intubated by the retrieval team.Because of the lack of good clinical data for the preva-lence of increased ETT cuff pressures during air medi-cal retrieval, we analyzed our documentation. The ob-jectives of this retrospective audit were to determine1) the prevalence of increased ETT cuff pressures priorto transport, 2) the changes of ETT cuff pressure withascent, and 3) the changes of ETT cuff pressure withdescent during fixed-wing retrievals.

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METHODS

This was a retrospective audit in 35 ventilated pa-tients during with fixed-wing retrievals by the RFDSSouth Eastern Section, New South Wales, Australia.Twelve months after introduction of a cuff pressuremanometer (Mallinckrodt, Hennef, Germany) and aventilation documentation sheet into clinical practice,all files of ventilated patients were analyzed for ETTcuff pressures and changes of pressure during med-ical retrievals with pressurized aircraft. Patient fileswere analyzed by using explicit chart review for ven-tilation details, cuff pressures on the ground beforeflight, during flight at cruising altitude, and on theground after landing. Cuff pressures were measuredonly once at every designated point. Additionally, ad-justments of the cuff pressures by the retrieval teamswere documented. Cabin pressure was measured withthe cabin altitude differential gauge (Aerosonic Corp,Clearwater, FL). Data are expressed as means ± stan-dard deviation (±SD). We calculated the change of ETTcuff pressure during ascent to cruising cabin pressureand the change of this pressure during descent fromcruising cabin pressure to ground level. We also de-termined the proportion of cases with adjustment ofETT cuff pressures at the different measurement timesand values over 30 and 50 cmH2O. The correlation(Pearson) between change in cabin pressure during as-cent and cuff pressure for each case was calculated. Anα-error p-value of less than 0.05 was considered statis-tically significant. Statistical analyses were performedwith SPSS v. 17.0 (SPSS, Chicago, IL). This project wasapproved by the Human Research Ethics CommitteeUniversity of Sydney (Ref. No. 14764).

RESULTS

Thirty-five patient files were analyzed. In 22 cases,the patients were already intubated by the timethe retrieval team arrived. Patients were ventilatedbecause of medical conditions such as respiratoryfailure or sepsis (40%), trauma (23%), post cardiacarrest/cardiogenic shock (14%), intoxications (5%), air-way compromise (5%), and other causes (13%). All re-trievals were from either minor hospitals or base hos-pitals to rural base hospitals or tertiary hospitals. Allpatients were adults and intubated with ETT: one pa-tient with size 6.5, one size 9, six size 7, 10 size 7.5,15 size 8, and two size 8.5. All patients were venti-lated with either an Oxylog 3000 or Oxylog 3000 plus(Draeger Medical, Best, The Netherlands). The modeof ventilation was either synchronous intermittentmandatory ventilation (SIMV) 43%, volume-controlledventilation (VCV) 9%, or pressure-controlled ventila-tion (PCV) 48%. Mean airway ventilation pressuresduring flight were maximum pressure (Pmax) 25 ± 8mbar (range 10–40 mbar) and positive end-expiratory

pressure (PEEP) 7 ± 2 mbar (range 4–15 mbar), andinspired oxygen concentration was 67% ± 17% (range40%–100%). All patients were monitored with end-tidal carbon dioxide (CO2) measurement. Mean du-ration of retrieval from arrival to handover at the re-ceiving hospital of our patients was 382 ± 72 minutes;mean flight time was 45 ± 13 minutes.

The mean of the first ETT cuff pressure measure-ment on the ground was 44 ± 20 cmH2O. In 63%of the patients, the cuff pressure was too high, i.e.,>30 cmH2O (in 11 patients >30 cmH2O and in 11 pa-tients >50 cmH2O). In 72% of the cases, the ETT cuffpressure was adjusted prior to takeoff. After adjust-ment, the ETT cuff pressure was 32 cmH2O in five casesand ≤30 cmH2O in the rest of the patients. After as-cent to cruising altitude, the cuff pressure was 42 ±13 cmH2O. Consequently, in 85% of cases, the pressurewas too high (22 patients >30 cmH2O and eight pa-tients >50 cmH2O), and in these patients the ETT cuffpressure was changed during flight. On ground levelafter landing, the pressure was 21 ± 5 cmH2O. In 85%of cases, the ETT cuff pressure was adjusted to a highercuff pressure. The distribution of ETT cuff pressurespreflight on the ground, after adjustment prior to take-off, in flight at cruising altitude, after adjustment dur-ing flight, and after landing are depicted in Figure 1.The mean cabin pressure during flight was 3,594 ±1,333 feet. The mean increase in ETT cuff pressure afterascent to cruising altitude was 14 ± 12 cmH2O (Fig. 2).The mean ascent from ground level was to cabinpressure of 2,674 ± 1,529 feet (Fig. 2). The Pearsoncorrelation for the increase of ETT cuff pressure afterascent to the real increase in cabin pressure (differenceof ground level and cabin pressure at cruising altitude)was weak (r = 0.3901), but statistically significant (p =0.0205).

DISCUSSION

This study clearly shows a high prevalence of ETT cuffpressures above 30 cmH2O. Despite adjusting thesepressures prior to takeoff, in 85% of our retrievals, thecuff pressure exceeded the safe margin at cruising alti-tude. If the ETT cuff pressures had not been adjustedprior to takeoff in our study, it is very likely that wewould have seen a much higher proportion of patientswith a pressure above 50 cmH2O in flight.

The high prevalence of high cuff pressure in theretrieval setting is well described from around theworld.1–3,8 Although ETT cuff pressure manometry isthe optimal method to determine safe ETT cuff pres-sure, it was standard practice in our retrieval serviceto palpate the ETT cuff ‘s pilot balloon to estimate thecuff pressure. Paramedics and emergency physicianshave been shown not to be able to monitor cuff pres-sure appropriately by palpation,9,10 and we assumethat we also misjudged the cuff pressures in the past.

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Brendt et al. ETT CUFF PRESSURE IN AIR MEDICAL RETRIEVAL 179

FIGURE 1. Distribution of cuff pressures: on arrival of the retrievalteam or after intubation, after the first adjustment by the retrievalteam on the ground, at cruising altitude in flight, after in-flight ad-justment by the retrieval team, and after landing.

The time frame for injuries due to increased ETT cuffpressures is not fully understood. However, in anes-thesia for short procedures (one to three hours), con-trolling of ETT cuff pressures reduces postprocedu-ral complications such as sore throat, hoarseness, andblood-streaked expectoration.11 Tracheal rupture dueto increased ETT cuff pressure has been reported forprehospital intubation,12 in the critical care setting andalso after general anesthesia.13,14 Therefore, we thinkthat increased cuff pressure can cause severe complica-tion in the early hours after intubation during the timeof an aeromedical retrieval. After our one-year experi-ence, we think using a cuff manometer is a safe alterna-tive to palpating the cuff’s pilot balloon pressure andshould be used in the aeromedical retrieval setting.

Interestingly, we found a weak correlation betweenincreases in cabin altitude and increases in cuff pres-

FIGURE 2. Scatterplot of the individual changes in endotrachealcuff pressure (� pressureascent cmH2O) from ground level to in-flight measurement in relation to the increase of cabin pressure (�pressureascent feet) from ground to flight level.

sure. In vitro observations of cuff volume of ETTand laryngeal mask airways showed a nearly lin-ear correlation between increase in altitude and cuffpressures.15,16 However, our observation of slight cor-relation between ascent and ETT cuff pressure is simi-lar to an observation from a helicopter-based Switzer-land air rescue service.1 An explanation for this couldbe that different tube types have different expandingcharacteristics.7 Unfortunately, we did not record tubetypes and cannot address this confounder. Addition-ally, confusion could be added if the tube size was notappropriate for the patients. Furthermore, there is nota strictly linear relationship between air pressure andaltitude.

LIMITATIONS

Limitations in our study largely relate to availabledata, since this was a retrospective review rather thanprospectively planned. We did not document the man-ufacturer and type of the ETT used in each of our pa-tients. We did not document whether in patients withcuff pressures above 30 cmH2O air leaks occurred withadjusted pressures below 30 cmH2O. Furthermore, wedid not calibrate our cuff manometer to zero prior tothe measurements and the manometer is dependent oncabin pressure.

CONCLUSION

Using cuff manometry helps to detect excessive cuffpressures in the rural and remote retrieval settingin New South Wales, Australia. Furthermore, it canbe used in flight to recognize ETT cuff pressurechanges related to ascent in altitude in air medicalretrievals.

References

1. Bassi M, Zuercher M, Erne JJ, Ummenhofer W. Endotrachealtube intracuff pressure during helicopter transport. Ann EmergMed. 2010;56:89–93, e81.

2. Chapman J, Pallin D, Ferrara L, et al. Endotracheal tube cuffpressures in patients intubated before transport. Am J EmergMed. 2009;27:980–2.

3. Svenson JE, Lindsay MB, O’Connor JE. Endotracheal intracuffpressures in the ED and prehospital setting: is there a problem?Am J Emerg Med. 2007;25:53–6.

4. Seegobin RD, van Hasselt GL. Endotracheal cuff pressure andtracheal mucosal blood flow: endoscopic study of effects of fourlarge volume cuffs. Br Med J (Clin Res Ed). 1984;288:965–8.

5. Pfannenstiel TJ, Gal TJ, Hayes DK, Myers KV. Vocal fold im-mobility following burn intensive care. Otolaryngol Head NeckSurg. 2007;137:152–6.

6. Henning J, Sharley P, Young R. Pressures within air-filledtracheal cuffs at altitude—an in vivo study. Anaesthesia.2004;59:252–4.

Preh

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180 PREHOSPITAL EMERGENCY CARE APRIL/JUNE 2013 VOLUME 17 / NUMBER 2

7. Smith RP, McArdle BH. Pressure in the cuffs of tracheal tubesat altitude. Anaesthesia. 2002;57:374–8.

8. Chopra M, Jones L, Boulanger C, et al. Prospective observa-tional measurement of tracheal tube cuff pressures in the emer-gency department. Emerg Med J. 2010;27:270–1.

9. Hoffman RJ, Parwani V, Hahn IH. Experienced emergencymedicine physicians cannot safely inflate or estimate endotra-cheal tube cuff pressure using standard techniques. Am J EmergMed. 2006;24:139–43.

10. Stein C, Berkowitz G, Kramer E. Assessment of safe endotra-cheal tube cuff pressures in emergency care—time for change?S Afr Med J. 2011;101:172–3.

11. Liu J, Zhang X, Gong W, et al. Correlations between con-trolled endotracheal tube cuff pressure and postproceduralcomplications: a multicenter study. Anesth Analg. 2010;111:1133–7.

12. Harris R, Joseph A. Acute tracheal rupture related to endotra-cheal intubation: case report. J Emerg Med. 2000;18:35–9.

13. Lim H, Kim JH, Kim D, et al. Tracheal rupture after endotra-cheal intubation—a report of three cases. Korean J Anesthesiol.2012;62:277–80.

14. Marty-Ane CH, Picard E, Jonquet O, Mary H. Membranous tra-cheal rupture after endotracheal intubation. Ann Thorac Surg.1995;60:1367–71.

15. Mann C, Parkinson N, Bleetman A. Endotracheal tube andlaryngeal mask airway cuff volume changes with altitude:a rule of thumb for aeromedical transport. Emerg Med J.2007;24:165–7.

16. Miyashiro RM, Yamamoto LG. Endotracheal tube and la-ryngeal mask airway cuff pressures can exceed critical val-ues during ascent to higher altitude. Pediatr Emerg Care.2011;27:367–70.

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