Article, Respiratory Medicine

Endotracheal tube cuff pressures in patients intubated before transport

Original Contribution

Endotracheal tube cuff pressures in patients intubated before transport?

Jacob Chapman MD a,b,?, Daniel Pallin MD, MPH b,c, Larisa Ferrara RRT d, Sarah Mortell RRT e, John Pliakas MSN, NP, EMTP f,

Melissa Shear BS a, Stephen Thomas MD, MPH a,f

aDepartment of Emergency Medicine, Massachusetts General Hospital, Boston, MA 02114, USA bDepartment of Emergency Medicine, Brigham and Women’s Hospital, Boston, MA 02115, USA cDepartment of Emergency Medicine, Children’s Hospital Boston, Boston, MA 02115, USA dDepartment of Respiratory Therapy, Massachusetts General Hospital, Boston, MA 02114, USA eDepartment of Respiratory Therapy, Brigham and Women’s Hospital, Boston, MA 02115, USA fBoston MedFlight, Boston, MA, USA

Received 26 June 2008; accepted 19 July 2008

Abstract

Introduction: Prolonged endotracheal tube cuff pressures (ETTCPs) greater than 30 cm H2O cause complications ranging from sore throat to rare cases of tracheoesophageal fistula. In a series of patients, we sought to determine the proportion of patients with overinflated cuffs and to determine whether overinflation was associated with demographics, diagnostic category, or intubator credentials.

Methods: Between July 2007 and April 2008, we measured cuff pressures on a convenience sample of patients drawn from 2 groups. The “helicopter group” had pressure measured before transport by a single aeromedical transport service. The “hospital group” had pressure measured upon arrival to 1 of 2 emergency departments after being intubated before transport.

Results: Three hundred patients aged 4 to 92 years (median, 57) were studied: 59.7% were male; and Diagnostic categories were neurologic (33.7%), trauma (32.7%), cardiac (12.7%), and general medical/ surgical (21.0%). Intubation occurred 1 to 28 000 minutes before ETTCP assessment (median, 60). Endotracheal tube cuff pressure was greater than 30 cm H2O in 64.7% and ranged from 10 to 180 (median, 40). Forty-nine percent of patients had ETTCP greater than 40 cm H2O. There was no association between ETTCP and age group, sex, diagnostic category, ETT size, time between intubation and ETTCP assessment, or intubator credentials.

Conclusions: The most compelling results of the study are the high rates of elevated ETTCPs. Furthermore, there were no clear risk factors for elevated ETTCP. Although the risk of elevated ETTCP in the prehospital to acute care time frame is unclear, it seems reasonable to measure ETTCP after intubation in all patients.

(C) 2009

? The study was approved by our human research committee.

* Corresponding author. Department of Emergency Medicine, Massachusetts General Hospital, Boston, MA 02114, USA.

0735-6757/$ – see front matter (C) 2009 doi:10.1016/j.ajem.2008.07.025

Endotracheal tube cuff pressures in transported patients

Introduction

Endotracheal tube cuffs serve 2 main roles: to decrease the likelihood of aspiration and to prevent an air leak during ventilation. The ideal cuff pressure has not been defined with a high degree of certainty, but most anesthesiologists generally recommend a target of 20 to 30 cm H2O [1]. Modern high-volume, low-pressure cuffs have decreased the risk of devastating complications such as Tracheal rupture and fistula formation; but cuff over- inflation still carries risks ranging from sore throat to tracheal ischemia [2-4].

The length of time needed for an elevated cuff pressure to cause these complications is unclear, but mucosal damage has been demonstrated after only 15 minutes in an animal model [5]. The time between intubation and the first measurement of the cuff pressure varies between settings and institutions.

A recent study measured the cuff pressure in a series of intubated patients transported by air and found that 58% of them had initial cuff pressures greater than 40 [6]. We sought to determine whether the results of this 1 study are generalizable to our own practice setting. We now report on a study of cuff pressures in a convenience sample of patients intubated before transport. We also sought to determine whether overinflation was more likely according to physician vs nonphysician intubator, patient demo- graphics, and diagnostic category. The 2 null hypotheses of this study were that elevated endotracheal tube cuff pressure (ETTCP) is not found frequently and that there are no particular patient characteristics that are predictive of higher risk for elevated ETTCP.

Methods

We measured cuff pressures in a convenience sample of patients intubated before transport between July 2007 and April 2008. We recruited patients in 2 settings. First, we sought to enroll all patients transported by a single helicopter aeromedical transport service (the “helicopter group”). Second, we enrolled a convenience sample of patients intubated before transport; cuff pressures were measured on arrival to 1 of 2 urban academic emergency departments (EDs) (the “hospital group”).

For the helicopter group, teams from 1 air transport service measured cuff pressures upon arriving at the transferring facility or scene. All patients intubated with cuffed Endotracheal tubes were eligible for the study, and there were no exclusion criteria. A single cuff pressure measurement was done on each patient, and the pressure was then adjusted to achieve a goal of 20 to 30 cm H2O. Measurement and adjustment were done by the flight nurse or flight paramedic. All pressures were measured on the ground, at an elevation above sea level of 500 ft or less. The

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helicopter group included all intubated patients transported by the service, irrespective of destination.

For the hospital group, we measured cuff pressures in a convenience sample of patients arriving intubated at 2 urban tertiary care EDs. Some of these patients were intubated in the field and brought directly to 1 of the 2 study sites. Others were intubated in the field and brought to another hospital before transfer to 1 of the 2 study sites. Others were intubated in another hospital before transfer to 1 of the 2 study sites. Cuff pressures were measured on hospital arrival by Respiratory therapists, who adjusted their pressures to 20 to 30 cm H2O. The hospital group included all patients arriving intubated, regardless of origin.

Our goal was to enroll 300 patients, with approximately 150 in each group (helicopter/hospital). Some patients fell into both the helicopter and hospital groups because they were transported by air to 1 of the 2 study EDs. These patients were counted only once and were included in the helicopter group, not the hospital group.

Univariate comparisons of ETTCPs were performed with Fisher exact test (for categorical data) and Kruskal-Wallis testing (for ordinal or continuous nonnormal data). The nonparametric trend test (an extension of Kruskal-Wallis testing) was used to assess for trends in continuous (nonnormal) data across ordinal groups such as month. Univariate linear regression was used to evaluate for possible predictive relationships between continuous predictor vari- ables and the continuous dependent variable of ETTCP. Logistic regression was used to adjust for multiple variables, while assessing for predictors of the dichotomous end points of elevated (N30) or highly elevated (N40) ETTCPs. For all analyses, P was set at the .05 level.

Our human subjects review committee approved this study.

Results

We enrolled 300 patients. Their demographic character- istics are detailed in Table 1.

The median ETTCP was 40 (interquartile range, 28-70). One hundred ninety-four patients (64.7%) had ETTCPs greater than 30, and 147 (49.0%) had pressures greater than

40. The ETTCPs were measured 1 to 28 000 minutes after

intubation (median, 60; interquartile range, 40-120).

There was no association between ETTCP and age group (Table 1), sex, diagnostic category, month of enrollment, time between intubation and ETTCP measurement, size of ETT, intubator credentials, enrollment group (hospital vs helicopter), or hospital site.

    1. Limitations

The same manometer was not used for all measurements, and there were multiple operators of the manometers. This

982 J. Chapman et al.

Table 1

Age (y) b18 18-65 N65

Male Female

Enrollment group Helicopter Hospital

Site 1

Site 2

Diagnostic categories Neurologic

Trauma Cardiac

General medical/surgical

Patient characteristics

4-92 (median, 57)

18 (6.0%)

178 (59.3%)

104 (34.7%)

179 (59.7%)

121 (40.3%)

136 (45.3%)

164 (54.7%)

84 (28.0%)

80 (26.7%)

101 (33.7%)

98 (32.7%)

38 (12.7%)

63 (21.0%)

For those who are still unconvinced that all practitioners who intubate patients are capable of overinflating ETT cuffs, future studies could study the cuff pressures of patients intubated in EDs and intensive care units. These studies could also assess whether the risk of cuff overinflation correlates with the years of experience of the intubating physician.

The most compelling results of the study are the descriptive analyses suggesting that high ETTCPs are very common. Furthermore, there were no clearly significant variables that predicted particular situations in which elevated ETTCP was likely to be identified. Although the risk of elevated ETTCP in the prehospital to acute care time frame is not clear, it seems reasonable to measure ETTCP after intubation in all patients.

undoubtedly resulted in some degree of Interobserver variability. We attempted to minimize this by providing a brief review session to every respiratory therapist (Massa- chusetts General Hospital and Brigham and Women’s Hospital) and nurses and paramedics (Boston MedFlight) involved with the study, but intraobserver and interobserver reliability was not measured. The study was also a convenience sample.

Discussion

Although there are individual practitioners who routinely check ETTCPs soon after every intubation, this practice has not yet become the standard of care among paramedics or physicians in most areas of this country. This study adds to the growing body of evidence that suggests that checking ETTCPs immediately after intubation should be the standard of care.

Although it is common for paramedics and physicians to palpate the external balloon (contiguous with the cuff) after intubation to attempt to obtain a rough estimate of the intracuff pressure, several studies have suggested that this is unreliable [7-9]. It is necessary to use a manometer to adequately assess intracuff pressure.

References

  1. Sengupta P, Sessler D, Maglinger P, Wells S, Vogt A, Durrani J, et al. Endotracheal tube pressure in three hospitals, and the volume required to produce an appropriate cuff pressure. BMC Anesthesiol 2004;4:8.
  2. Mandoe H, Nikolajsen L, Lintrup U, Jepsen D, Molgaard J. Sore throat after endotracheal intubation. Anesth Analg 1992;74:897-900.
  3. Nordin U, Lindholm CE, Wolgast M. Blood flow in the rabbit tracheal mucosa under normal conditions and under the influence of tracheal intubation. Acta Anaesthesiol Scand 1977;21:81-94.
  4. Seegobin RD, van Hesselt GL. Endotracheal cuff pressure and tracheal mucosal blood flow: endoscopic study of effects of four large volume cuffs. Br Med J (Clin Res Ed) 1984;288:965-8.
  5. Nordin U. The trachea and cuff induced tracheal injury: an experimental study on causative factors and prevention. Acta Otolaryngol 1976;345 (Suppl 345):1-7.
  6. Svenson J, Lindsay M, O’Connor J. Endotracheal intracuff pressures in the ED and prehospital setting: is there a problem? Am J Emerg Med 2007;25:53-6.
  7. Fernandez R, Blanch L, Mancebo J, Bonsoms N, Artigas A. Endotracheal tube cuff pressure assessment: pitfalls of finger estimation and need for objective measurement. Crit Care Med 1990;18:1423-6.
  8. Braz JR, Navarro LH, Takata IH, Nascimento Junior P. Endotracheal tube cuff pressure: need for precise measurement. Sao Paulo Med J 1999;17:243-7.
  9. Parwani V, Hoffman R, Russell Bharel C, Preblick C, Hahn I. Practicing paramedics cannot generate or estimate safe endotracheal tube cuff pressure using standard techniques. Prehosp Emerg Care 2007;11(3): 307-11.