ETT Cuff Inflation Assessment

     As first responders, paramedics are expected to perform endotracheal intubations safely and effectively. Endotracheal intubation is a complex procedure which requires a skill set and specific fund of knowledge.

     Inflation and assessment of the endotracheal tube cuff (ETTc) pressure is often underappreciated as a critical aspect of endotracheal intubation. Using appropriate ETTc pressure, endotracheal intubation lets the clinician seal the airway to prevent aspiration and provide positive-pressure ventilation without air leaking. If the ETTc pressure exceeds the tracheal mucosal capillary perfusion pressure, the ETTc quickly begins to injure the mucosa and surrounding tissues.¹ Complications resulting from excessive ETTc pressure include tracheal necrosis and stenosis, post-intubation tracheal pain, tracheal perforation, vocal cord paralysis or immobility and tracheo-esophageal fistula formation.^2–6

     Using a method of measuring or estimating ETTc pressure that adequately identifies overinflated cuffs may allow clinicians to avoid the complications of excessive ETTc pressure.^7–10 Previous studies of clinician groups, including paramedic students, emergency medicine physicians, anesthesia providers and ICU teams,^11–15 show they all grossly overestimate safe inflation volume and/or pressure when performing endotracheal intubation or using fingertip estimation palpating the pilot balloon.

     Standardized instruments to measure cuff pressures might help decrease the possibility of injury resulting from endotracheal intubation. However, commercially available cuff inflators and manometers are not widely available in the prehospital setting, and the minimal air seal/leak technique is not widely utilized.

     Correlations between clinician experience, fewer complications and better outcomes have been shown in many medical procedures.¹⁶ Paramedics are expected to perform endotracheal intubation frequently enough to maintain their skills and expertise. But most paramedics fail to perform even one endotracheal intubation per year.¹⁷

     The purpose of this descriptive study was to survey urban-based paramedics to determine how they inflated endotracheal tubes and assessed cuff pressures. A secondary aim was to determine if their methods of cuff inflation were correlated with their experience as paramedics, as well as to describe the frequency with which Fire Department of New York paramedics performed endotracheal intubations.

     This study surveyed licensed paramedics to determine 1) their years in practice, 2) how frequently they performed endotracheal intubations and 3) how they determined volume or pressure of endotracheal tube cuffs. This study was approved by the Institutional Review Board of St. Luke's-Roosevelt Hospital Center in New York City. All participants gave their informed consent to participation in the study.

     The study surveyed 53 urban-based licensed paramedics at a paramedic CME course that included participants from each of the five boroughs of New York City.

     We sought to determine the methods by which these paramedics determined cuff pressures following endotracheal intubation. Safe pressure for cuff inflation is commonly defined as less than or equal to 25 cm H₂O. Below this pressure, capillary perfusion pressure is not typically impaired, and there are no expected risks of long-term compression damage to the human airway. A secondary outcome assessed the frequency of endotracheal intubations by these paramedics.

     The survey asked medics to choose from options regarding their preferred method to estimate cuff inflation. These options were 1) using a fixed volume of air; 2) palpation of the pilot balloon; or 3) other (medics could write in their method). Participants were also asked if they ever used a Cufflator or manometer in their practice.

     This was a convenience sample that included multiple paramedics from each of at least five base stations. We included multiple base stations and multiple paramedics from each station to account for possible station-to-station variability, as well as to eliminate the possibility of having a nonrepresentative paramedic, such as the most experienced or least experienced from a given base station, be assessed as representative of their entire station crew.

     Using Intercooled Stata 8.2 (Stata Corp., Plano, TX), we produced summary statistics, including means and corresponding 95% confidence intervals.

     The sample included participants with an average career length of 6.6 years (95% CI, 5.7–7.4). The estimated frequency of participants' endotracheal intubations was an average of 3.6 times per year (95% CI, 3.5–3.9). When inflating ETTcs after endotracheal intubation, 87% (n=46) preferred injecting a set volume of air into the cuff. The remaining 13% of participants (n=7) inflated cuffs using palpation of the pilot balloon. No participants inflated ETTcs by injecting air until they perceived resistance, used the minimum air/seal technique, or used a cuff inflation device other than a standard syringe.

     The 95% confidence interval for this average was quite narrow, indicating tremendous uniformity in experiences across the sampled group. Additionally, there was great uniformity to preferred methods of endotracheal tube cuff inflation.

     The number of endotracheal intubations performed annually by these Fire Department of New York paramedics is congruent with those reported elsewhere. It is beyond the scope of this article to assess how frequently endotracheal intubation needs to be performed for paramedics to maintain competence in this procedure. We report the frequency (3.6/year average) here simply as a benchmark that others may refer to or use as a basis for addressing issues surrounding the varying viewpoints on endotracheal intubation in the prehospital setting.

     In the trachea, capillary blood flow becomes obstructed when the pressure in an ETTc exceeds the capillary perfusion pressure of the tracheal mucosa. Reports suggest that 25 cm H₂O is a "safe" pressure, although the precise pressure at which capillary perfusion is impaired certainly will vary from patient to patient.¹⁸ The precise pressure at which any individual will experience impaired or obstructed tracheal mucosal blood flow will depend upon numerous factors, most important their blood pressure.¹ Other factors are also important in avoiding damage; these include adjusting cuff inflation for altitude, correct positioning of the patient's head and neck during intubation, avoiding infection involving the patient's secretions, preventing severe respiratory failure, and avoiding prolonged intubation.^19–21

     Severe overinflation of the ETTc may result in severe, even fatal injury. Less severe, but significant adverse effects are tracheal pain or stridor, injury to the recurrent laryngeal nerve and direct damage to the vocal cords.^3,5,22

     This study demonstrated that FDNY paramedics overwhelmingly inflated ETTcs by only two methods: either by injecting a fixed volume of air or by palpation of the pilot balloon. None reported using the minimal air seal technique or using standardized instruments to attain safe cuff pressure.

     Previous studies have demonstrated that graduating paramedic students, paramedics, emergency medicine physicians, anesthesiologists and respiratory therapists all grossly overestimate safe inflation pressures.^12,15 Using standardized instruments to measure cuff pressures might help increase safety by decreasing the possibility of injury resulting from endotracheal intubation. Whether this is practical for paramedics to do in the field is unknown. Use of such instruments might interfere with the top priority of securing an airway or rapidly transporting the patient to a hospital. Additionally, since there is little data available on short-term complications, it is unclear what difference in outcomes would result from measuring inflation pressures in the field relative to measuring them in the hospital.

     Prehospital professionals should consider available information suggesting that clinicians cannot detect overinflation of ETTcs by palpating the pilot balloon. This has been addressed in numerous other publications.^{3,7,11,12,15,23} Emergency department staff should measure cuff pressures after endotracheal intubations themselves, whether the intubations occurred in the field or in the ED. Many patients who remain intubated eventually have their ETTc pressures checked by respiratory therapists or ICU staff. However, since overinflation of ETTcs is potentially injurious, prehospital personnel and emergency medicine clinicians should consider screening for it.

     As conducted, this study has several potential limitations. The first is the rate of survey response. The second is that this was an urban-based study, and its results might not be comparable to those of other areas. The rates of intubation per paramedic, as well as the methods and preferences of techniques, may be different elsewhere.

     The risk of injury resulting from overinflated ETTcs warrants evaluation of current endotracheal intubation practices. The practice of inflating ETTcs without precisely measuring their pressure, in particular, should be closely scrutinized. We believe the information described here should be considered in addressing the significant issues of safety of endotracheal intubation performed in the prehospital setting and how to make such intubations as successful and safe as possible.

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19. Henning J, Sharley P, Young R. Pressures within air-filled tracheal cuffs at altitude: An in vivo study. Anaesthesia 59(3):252–4, Mar 2004.

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     Robert J. Hoffman, MD, MS, is director of research in the Department of Emergency Medicine at Beth Israel Medical Center in New York, NY. He has a graduate degree in clinical research methods from the Columbia University Mailman School of Public Health in New York, NY.

     Yoichi Kato, MD, is an emergency medicine resident in the Department of Emergency Medicine at Beth Israel Medical Center in New York, NY.

     Louis Rivera, MD, is an emergency medicine resident in the Department of Emergency Medicine at Beth Israel Medical Center in New York, NY.

     Sujatha Sheth, MD, is an emergency medicine resident in the Department of Emergency Medicine at Beth Israel Medical Center in New York, NY.

     Ann Prokofieva, MD, is an emergency medicine resident in the Department of Emergency Medicine at Beth Israel Medical Center in New York, NY.

     Vivek Parwani, MD, graduated Beth Israel Medical Center emergency medicine residency in 2004. He completed a fellowship in Emergency Medical Services at Yale University in 2005. He is currently a board-certified practicing emergency medicine physician and is a member of the New Haven Regional EMS Physician Response Team.