- Email: [email protected]
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Research Forum Abstracts par with published civilian prehospital experience. In 15 months of high acuity trauma, there were no unrecognized esophageal intubations. However, ETCO2 detection was not consistently applied to confirm intubation in the field. We found during the course of the study that many critically ill patients that, in our judgment, would have benefited from battlefield intubation. Future efforts to improve advanced prehospital airway management may be under-utilized in combat will focus on improving the simplicity of airway techniques under these highly stressful conditions.
86
Comparison of Two Common Techniques for Inflating Endotracheal Tube Cuffs: Set Volume of Air Vs. Palpation of the Pilot Balloon
Hoffman RJ, Parwani V, Kaban J, Dueffer H, Howell A, Sturmann K/Beth Israel Medical Center, Department of Emergency Medicine, New York, NY; Yale University School of Medicine, Division of Emergency Medicine, New York, NY
Study Objectives: Safe, appropriate pressure in endotacheal tube cuffs (ETTc) is between 15-25 cm H2O, which is below normal capillary perfusion pressure. Higher pressures may result in tracheal injury. Both in vivo and simulation studies of intubation practices indicate that inflation of ETTc without measurement of intracuff pressure commonly results in ETTc overinflation. The two most commonly reported methods of ETTc inflation are 1) injection of a predetermined volume of air and 2) injection of air limited by palpation of the pilot ballon for subjective estimation of ETTc pressure. These methods might result in different ETTc volumes and pressures. We compared these methods of ETTc inflation with the pressures generated and frequency of overinflation. Methods: This IRB-approved descriptive study of EM attending physicians in 5 accredited EM residency training programs in New York City and paramedics from multiple base stations in New York City used a previously tested, tracheal simulation model with a 7.5 ET tube with a high-volume low-pressure cuff (Mallinkrodt, St. Louis, MO). Using their choice of a 5 mL or 10 mL plastic syringe with standard luer lock (Becton-Dickinson, Franklin Lakes, NJ) participants inflated the ETTc by injecting air as they deemed appropriate, which was 1) injection of a predetermined volume of air or 2) injection of air limited by palpation of the pilot balloon for subjective estimation of cuff pressure. Subsequently, the ETTc pressure was measured using a highly sensitive and accurate analog manometer (Boerhinger Laboratories, Norristown, PA). Using a t-test, the mean ETTc pressure between clinicians using each method was compared to detect difference in mean pressure and frequency of overinflation. Results: 53 paramedics and 41 EM attending physicians were sampled. Using an unpaired, two sample t-test with presumption of unequal variance in groups, there was a statistically significant difference (p 0.02) in pressures generated by those using a set volume of air and those inflating with palpation of the pilot balloon. The precise mean couldn’t be determined because 61% (n⫽ 57, 22 EM attendings, 35 paramedics) inflated to pressures beyond the upper limit of manometer sensitivity (⬎ 120 cm H2O). The palpation method rsulted in lower mean pressures than injecting a set volume of air, but both methods resulted in extremely high ETTc pressures far beyond safe limits. The frequency of overinflation was respectively 99% and 92% of those using methods 1) and 2) described above. Conclusion: Palpation of the pilot balloon more commonly results in safe ETTc pressure and results in average pressures that are less extreme than inflation by injection of a set volume of air. Both methods frequently result in extremely high ETTc pressures. Although there is a statistical difference suggesting pilot balloon palpation may be superior, both methods give poor results. To avoid high ETTc pressures, clinicians should consider using devices that permit safe and accurate inflation and measurement of ETTc pressure rather than relying on standard techniques.
Volume , . : October
87
Do Endotracheal Tube Cuff Pressure and Volume Have a Linear or Nonlinear Relationship?
Hoffman RJ, Sturmann K, Dueffer H, Kilpela K, Howell A, Hahn I/Beth Israel Medical Center Department of Emergency Medicine, New York, NY; St. Luke’s-Roosevelt Hospital Center, Department of Emergency Medicine, New York, NY
Study Objectives: Standard methods of endotracheal tube (ETT) cuff inflation may result in high intracuff pressure. If a logarithmic relationship between ETTc cuff pressures and ETTc volumes exists, addition of small volumes of air may result in dramatic increases in pressure after a threshold volume is reached. If a linear relationship exists, no such precipitous increase in pressure with additional volume would occur. We sought to determine if there is a linear or logarithmic relationship between ETTc pressure and ETTc volume. Methods: In this Institutional Animal Care and Use Committee-approved study, we recorded ETTc pressure and volume in 4 anesthetized and mechanically-ventilated canines ranging between 30-40 pounds that were endotracheally intubated with a 7.0 ETT. The varying pressures associated with a distribution of 28 volumes of air in the ETTc were recorded. Using Intercooled Stata 8.2 (Stata Corporation, Plano, TX), Spearman correlation was performed to determine if a linear or non-linear relationship existed between these variables. Results: The Spearman rho coefficient of correlation between these two variables was .969, or 97%, suggesting near-perfect linear relationship between ETTc pressure and ETTc volume over the range of volume and pressure tested. Conclusion: ETTc volume and pressure in these canines has an extraordinarily strong linear correlation. It is particularly relevant that this correlation has a narrow 95% confidence interval. A logarithmic relationship clearly does not exist. The significance of these findings is that, due to the linear relationship, there is not an increase in the slope the pressure:volume curve at greater volumes; additional air injected into the ETTc at the upper end of the pressure:volume curve is not associated with precipitous rise in ETTc pressure. Thus, there does not appear to be any volume threshold associated with greater risk of overinflation. This phenomenon is likely due to compliance of the trachea and supporting tissues.
Annals of Emergency Medicine S27
86
Comparison of Two Common Techniques for Inflating Endotracheal Tube Cuffs: Set Volume of Air Vs. Palpation of the Pilot Balloon
Hoffman RJ, Parwani V, Kaban J, Dueffer H, Howell A, Sturmann K/Beth Israel Medical Center, Department of Emergency Medicine, New York, NY; Yale University School of Medicine, Division of Emergency Medicine, New York, NY
Study Objectives: Safe, appropriate pressure in endotacheal tube cuffs (ETTc) is between 15-25 cm H2O, which is below normal capillary perfusion pressure. Higher pressures may result in tracheal injury. Both in vivo and simulation studies of intubation practices indicate that inflation of ETTc without measurement of intracuff pressure commonly results in ETTc overinflation. The two most commonly reported methods of ETTc inflation are 1) injection of a predetermined volume of air and 2) injection of air limited by palpation of the pilot ballon for subjective estimation of ETTc pressure. These methods might result in different ETTc volumes and pressures. We compared these methods of ETTc inflation with the pressures generated and frequency of overinflation. Methods: This IRB-approved descriptive study of EM attending physicians in 5 accredited EM residency training programs in New York City and paramedics from multiple base stations in New York City used a previously tested, tracheal simulation model with a 7.5 ET tube with a high-volume low-pressure cuff (Mallinkrodt, St. Louis, MO). Using their choice of a 5 mL or 10 mL plastic syringe with standard luer lock (Becton-Dickinson, Franklin Lakes, NJ) participants inflated the ETTc by injecting air as they deemed appropriate, which was 1) injection of a predetermined volume of air or 2) injection of air limited by palpation of the pilot balloon for subjective estimation of cuff pressure. Subsequently, the ETTc pressure was measured using a highly sensitive and accurate analog manometer (Boerhinger Laboratories, Norristown, PA). Using a t-test, the mean ETTc pressure between clinicians using each method was compared to detect difference in mean pressure and frequency of overinflation. Results: 53 paramedics and 41 EM attending physicians were sampled. Using an unpaired, two sample t-test with presumption of unequal variance in groups, there was a statistically significant difference (p 0.02) in pressures generated by those using a set volume of air and those inflating with palpation of the pilot balloon. The precise mean couldn’t be determined because 61% (n⫽ 57, 22 EM attendings, 35 paramedics) inflated to pressures beyond the upper limit of manometer sensitivity (⬎ 120 cm H2O). The palpation method rsulted in lower mean pressures than injecting a set volume of air, but both methods resulted in extremely high ETTc pressures far beyond safe limits. The frequency of overinflation was respectively 99% and 92% of those using methods 1) and 2) described above. Conclusion: Palpation of the pilot balloon more commonly results in safe ETTc pressure and results in average pressures that are less extreme than inflation by injection of a set volume of air. Both methods frequently result in extremely high ETTc pressures. Although there is a statistical difference suggesting pilot balloon palpation may be superior, both methods give poor results. To avoid high ETTc pressures, clinicians should consider using devices that permit safe and accurate inflation and measurement of ETTc pressure rather than relying on standard techniques.
Volume , . : October
87
Do Endotracheal Tube Cuff Pressure and Volume Have a Linear or Nonlinear Relationship?
Hoffman RJ, Sturmann K, Dueffer H, Kilpela K, Howell A, Hahn I/Beth Israel Medical Center Department of Emergency Medicine, New York, NY; St. Luke’s-Roosevelt Hospital Center, Department of Emergency Medicine, New York, NY
Study Objectives: Standard methods of endotracheal tube (ETT) cuff inflation may result in high intracuff pressure. If a logarithmic relationship between ETTc cuff pressures and ETTc volumes exists, addition of small volumes of air may result in dramatic increases in pressure after a threshold volume is reached. If a linear relationship exists, no such precipitous increase in pressure with additional volume would occur. We sought to determine if there is a linear or logarithmic relationship between ETTc pressure and ETTc volume. Methods: In this Institutional Animal Care and Use Committee-approved study, we recorded ETTc pressure and volume in 4 anesthetized and mechanically-ventilated canines ranging between 30-40 pounds that were endotracheally intubated with a 7.0 ETT. The varying pressures associated with a distribution of 28 volumes of air in the ETTc were recorded. Using Intercooled Stata 8.2 (Stata Corporation, Plano, TX), Spearman correlation was performed to determine if a linear or non-linear relationship existed between these variables. Results: The Spearman rho coefficient of correlation between these two variables was .969, or 97%, suggesting near-perfect linear relationship between ETTc pressure and ETTc volume over the range of volume and pressure tested. Conclusion: ETTc volume and pressure in these canines has an extraordinarily strong linear correlation. It is particularly relevant that this correlation has a narrow 95% confidence interval. A logarithmic relationship clearly does not exist. The significance of these findings is that, due to the linear relationship, there is not an increase in the slope the pressure:volume curve at greater volumes; additional air injected into the ETTc at the upper end of the pressure:volume curve is not associated with precipitous rise in ETTc pressure. Thus, there does not appear to be any volume threshold associated with greater risk of overinflation. This phenomenon is likely due to compliance of the trachea and supporting tissues.
Annals of Emergency Medicine S27