Original Article
Endotracheal Tube Cuff Pressure Monitoring in Peripheral Hospitals Maj R Goyal* Lt Col G Kumar + Maj Gen M R Waghray# Abstract Background: An improvised monitor was designed in a peripheral hospital to measure the tracheal tube cuff pressures in patients intubated under anaesthesia. The aim of the study was to assess the efficacy of assessment of cuff pressure by the traditional palpatory method and to compare the improvised monitor with the standard monitor commercially available. The effect of nitrous oxide on the cuff-pressure was also studied. Methods: The tracheal tube cuff pressure of 80 patients undergoing general anaesthesia was assessed by palpation and measured with an improvised and standard monitor. Results: The study showed that the tracheal cuff pressure recorded were higher than normal tracheal perfusion pressure in 40% of the cases with satisfactory palpatory assessment. The pressures recorded by the improvised monitor were comparable to that of the standard monitor. The use of nitrous oxide resulted in increase in cuff pressures over a period of time. Conclusion: An objective measurement by any equipment is superior to assessment of cuff pressure by palpation. The improvised monitor can be used to give a fair idea of the cuff pressures, in places where a standard monitor is not available. MJAFI 2006; 62 : 243-245 Keywords: Tracheal tube cuff pressure; Tracheal ischaemia; Tracheal cuff pressure monitor
Introduction large number of patients are being artificially ventilated in the operation theatres (OT) or in the intensive care units (ICU), for duration ranging from a few hours to weeks . The cuffs of the endotracheal tubes (ETT) are routinely inflated with air and assessed by digital palpation. Previous studies have demonstrated that cuff palpation is an unreliable and a subjective method, unable to detect high cuff pressures [1]. Tracheal tube cuff pressure monitor, a small hand-held device, is the ideal method for objective measurement of cuff pressures. It has been established that excessive cuff pressures beyond the tracheal mucosal perfusion pressure (normal being 30mm Hg) [2], are related to tracheal mucosal ischaemia and its complications [3].The use of nitrous oxide in patients under general anaesthesia is also likely to increase the cuff pressures over a period of time, due to its passage into the cuff filled with air [4].
A
Materials and Methods A simple improvised tracheal tube cuff pressure monitor, as shown in Fig. 1, was designed with the help of commonly available parts i.e. the circular pressure gauge of an aneroid sphygmomanometer with calibration from 20 to 300 mm Hg,
Fig. 1. Improvised Endotracheal tube cuff-pressure monitor
*Graded Specialist (Anaesthesia), 164 MH C/o 99 APO. +Graded Specialist (Surgery), 167 MH C/o 56 APO. # Addl DGMS (H &PS&IS), Office of DGMS (A), AHQ, New Delhi. Received : 13.05.2005; Accepted : 14.12.2005
244
Goyal, Kumar and Waghray
Fig. 4. Endotracheal tube cuff-pressure under anaesthesia Fig. 2. Standard Endotracheal tube cuff-pressure monitor
Table 1 Demographic data Age (years) Weight (Kg) Sex (Male:Female) Duration of surgery (min)
20-60 52± 5 3:2 90±10
Table 2 Endotracheal tube cuff pressure Fig. 3. Cuff pressure distribution in the satisfactory group
Subjective assessment *
2.5cm long rubber tubing cut from any sphygmomanometer and a small plastic connector, from intravenous sets. After taking approval from the hospital ethics committee, 80 patients of American Society of Anaesthesiologists (ASA) grade I or II undergoing general anaesthesia with the use of muscle relaxants and nitrous oxide were studied over a period of one year. ETTs (Portex, high volume-low pressure cuff) sized 7.5mm and 8.5 mm ID, were used for female and male patients respectively. After intubation, the tracheal cuffs were filled with air by an operating room assistant (ORA), blinded to the study design. One of the five ORAs, each with at least 15 years of experience, was randomly asked to assess the cuff pressures by digital palpation and rate it as overinflated (OI), satisfactory (S) or underinflated (UI). The pressures were measured by both monitors and then readjusted to 25 mm Hg by altering the cuff-volume. Thereafter, pressures were checked every 15 min for 90 minutes, by both monitors. Any patient with an audible air leak at this pressure was excluded from the study.
OI S UI
Results The demographic data is shown in Table 1. Two patients with an air leak at 25 mm Hg, due to an undersized ETT, were excluded from the study. The palpatory assessment and the recorded cuff-pressures, at the time of intubation, were tabulated (Table 2). Table 3 shows the statistical analysis of the readings by the two monitors in the satisfactory group. The cuff pressure distribution in this group (Fig. 3), reveals that 40% cases had higher than desired cuff pressure. The mean values in both groups were also high, with maximum upto 60mm Hg, as measured on the standard monitor. The difference between
n=5 n=66 n=7
Cuff pressure** Improvised Standard 80 35.6 15.1
80.8 36 17
* overinflated (OI), satisfactory (S), underinflated (UI); ** mean value (mm Hg) Table 3 Improvised vs Standard monitor in satisfactory group – z test
Mean Range Pearson Correlation z
Improvised
Standard
35.5 22-60 0.98 0.32
36 24-60
the two monitors was not significant, at 95% confidence limits (z= 0.32). The Pearson Correlation (0.98) between the two monitors was close to 1, which signifies the high degree of correlation between the readings of the two groups. Fig. 4 shows the rise of pressures beyond the normal range with the use of nitrous oxide.
Discussion Tracheal intubation provides a reliable and patent airway in general anaesthesia and critical care setting. Low cuff pressure increases the risk of gas leak, pulmonary aspiration and nosocomial infections whereas overinflation may lead to mucosal ischaemia and its complications [5, 6]. Assessment of the adequacy of cuff pressure by digital palpation is only a subjective method unable to detect high cuff pressures [7]. Some MJAFI, Vol. 62, No. 3, 2006
Tracheal Cuff Pressure Monitoring
authors have also observed that in high-compliance endotracheal tube, cuff pressure increases very slowly, between pressures of 13 and 27mmHg, after which the addition of small volumes increases the cuff pressure substantially [8]. Macroscopic examination of the tracheal mucosa by a fiberoscope via an ETT during general anaesthesia by Sajedi et al [9], has shown significantly large number of tracheal mucosal lesions at the site of cuff, associated with high cuff pressures. The tracheal cuff pressures should be routinely checked for all intubated patients [10]. Low tissue perfusion, hypoxaemia, anaemia, metabolic acidosis and uncontrolled diabetes mellitus are some of the conditions in the critically ill which predispose patients to develop morbid postintubation sequelae [3, 11]. Spittle and Beavis, [12] in their survey found that only 13% of ICUs routinely monitor cuff pressures and 3% record the pressure on the patient chart. Vyas et al [10] studied 32 patients in the ICU and found that 62% had higher than acceptable cuff pressures. They surveyed a part of United Kingdom and discovered that 75% ICUs never routinely checked cuff pressures. The improvised tracheal cuff pressure monitor can provide a fair degree of cuff-pressure assessment in the absence of a standard monitor. However, the improvised monitor has several limitations. The scale is 2mm Hg as compared to 1mm Hg in the standard monitor. The commercially available monitor can auto correct, and maintain pressure once corrected. The improvised monitor, cannot autocorrect and results in a small amount of air leak when detached from the pilot balloon. Further modification to the improvised equipment, with the addition of a three-way stop cock with a syringe attached to one end, is suggested to minimise this air pressure leak. It is also recommended by the authors that this monitor be connected and left attached to the pilot cuff for continuous monitoring. During anaesthesia, it should be considered that nitrous oxide, diffuses easily into the endotracheal tube cuffs, increasing the cuff pressure [4]. Various methods have been used to prevent the unpredictable rise in cuff pressures during general anaesthesia including filling of cuffs with anaesthetic mixtures or isotonic saline [13]. Special ETTs like Brandt or Lanz are also described in contemporary literature, which have pressure regulating
MJAFI, Vol. 62, No. 3, 2006
245
system in their cuffs, but their prohibitive high costs is the limiting factor. The authors recommend that every institution should have a protocol for monitoring tracheal cuff pressures [14] and further studies on the subject would help in formulating a standard protocol. Conflicts of Interest None identified References 1. Fernandez R, Blanch L, Mancebo J, Bonsoms N. Endotracheal tube cuff pressure assessment: pitfalls of finger estimation and need for objective measurement. Crit Care Med 1990; 18: 1423-6. 2. Guyton AC. The systemic circulation. In: Guyton AC, editor. Medical Physiology. 10th ed. Philadelphia : WB Saunders, 2000; 218-28. 3. Henkel H, Gretcher C. Relation of tracheal cuff pressure to tracheal morbidity after extubation. Anaesthesiology 2001; 95: 5. 4. Dullenkopf A, Gerber AC. Nitrous oxide diffuses into tracheal tube cuffs: comparison of 5 different tracheal tube cuffs. Acta Anaesthesiol Scand 2004; 48:1180. 5. Sathish SK, Young PJ. Overinflation of tracheal tube cuff: a case for routine monitoring. Critical Care 2002; 6 (Supp 1) : 37S. 6. Spittle N, McCluskey A. Lesson of the week: tracheal stenosis after intubation. Br J Anaesth 2000; 321:1000-2. 7. Blaz JRC, Navarro, et al. Endotracheal tube cuff pressure: need for precise measurement. Sao Paulo Med J 1999; 117: 230-8. 8. Byrd RA, Mascia MF. What is the endotracheal tube cuff pressure in a cross-section of intubated patients? Anesthesiology 1996; 85 (Suppl 3A): 982S. 9. Sajedi P, Marooffi V. The macroscopic changes of tracheal mucosa following tight vs loose control of tracheal tube cuff pressure. Acta Anaesthesiol 2002; (Suppl 40):117S-120S. 10. Vyas DI, Inweregbn K, Pittard A. Measurement of tracheal cuff pressure in critical care. Anaesthesia 2002; 57: 275-7. 11. A Millard. Double respiratory sequelae of head injury: subglottic stenosis and bilateral pneumothoraces. Br J Anaesth 2003; 90: 94-6. 12. Spittle CSN, Beavis SE. Do you measure tracheal cuff pressure? A survey of clinical practice. Br J Anaesth 2001; 87:344-5. 13. Pivoz, Reuven MD. Intracuff pressure and tracheal morbidity: Influence of filling cuff with saline during nitrous oxide anaesthesia. Survey of Anaesthesiology 2002; 46: 222. 14. Nightangle P, Clayton J. Intensive care services. In : Royal College of Anaesthetists Compendium, Tracheal Tube Cuff Pressure. Raising the standard. 2000; Chapter 8, Audit 2.
Endotracheal Tube Cuff Pressure Monitoring in Peripheral Hospitals Maj R Goyal* Lt Col G Kumar + Maj Gen M R Waghray# Abstract Background: An improvised monitor was designed in a peripheral hospital to measure the tracheal tube cuff pressures in patients intubated under anaesthesia. The aim of the study was to assess the efficacy of assessment of cuff pressure by the traditional palpatory method and to compare the improvised monitor with the standard monitor commercially available. The effect of nitrous oxide on the cuff-pressure was also studied. Methods: The tracheal tube cuff pressure of 80 patients undergoing general anaesthesia was assessed by palpation and measured with an improvised and standard monitor. Results: The study showed that the tracheal cuff pressure recorded were higher than normal tracheal perfusion pressure in 40% of the cases with satisfactory palpatory assessment. The pressures recorded by the improvised monitor were comparable to that of the standard monitor. The use of nitrous oxide resulted in increase in cuff pressures over a period of time. Conclusion: An objective measurement by any equipment is superior to assessment of cuff pressure by palpation. The improvised monitor can be used to give a fair idea of the cuff pressures, in places where a standard monitor is not available. MJAFI 2006; 62 : 243-245 Keywords: Tracheal tube cuff pressure; Tracheal ischaemia; Tracheal cuff pressure monitor
Introduction large number of patients are being artificially ventilated in the operation theatres (OT) or in the intensive care units (ICU), for duration ranging from a few hours to weeks . The cuffs of the endotracheal tubes (ETT) are routinely inflated with air and assessed by digital palpation. Previous studies have demonstrated that cuff palpation is an unreliable and a subjective method, unable to detect high cuff pressures [1]. Tracheal tube cuff pressure monitor, a small hand-held device, is the ideal method for objective measurement of cuff pressures. It has been established that excessive cuff pressures beyond the tracheal mucosal perfusion pressure (normal being 30mm Hg) [2], are related to tracheal mucosal ischaemia and its complications [3].The use of nitrous oxide in patients under general anaesthesia is also likely to increase the cuff pressures over a period of time, due to its passage into the cuff filled with air [4].
A
Materials and Methods A simple improvised tracheal tube cuff pressure monitor, as shown in Fig. 1, was designed with the help of commonly available parts i.e. the circular pressure gauge of an aneroid sphygmomanometer with calibration from 20 to 300 mm Hg,
Fig. 1. Improvised Endotracheal tube cuff-pressure monitor
*Graded Specialist (Anaesthesia), 164 MH C/o 99 APO. +Graded Specialist (Surgery), 167 MH C/o 56 APO. # Addl DGMS (H &PS&IS), Office of DGMS (A), AHQ, New Delhi. Received : 13.05.2005; Accepted : 14.12.2005
244
Goyal, Kumar and Waghray
Fig. 4. Endotracheal tube cuff-pressure under anaesthesia Fig. 2. Standard Endotracheal tube cuff-pressure monitor
Table 1 Demographic data Age (years) Weight (Kg) Sex (Male:Female) Duration of surgery (min)
20-60 52± 5 3:2 90±10
Table 2 Endotracheal tube cuff pressure Fig. 3. Cuff pressure distribution in the satisfactory group
Subjective assessment *
2.5cm long rubber tubing cut from any sphygmomanometer and a small plastic connector, from intravenous sets. After taking approval from the hospital ethics committee, 80 patients of American Society of Anaesthesiologists (ASA) grade I or II undergoing general anaesthesia with the use of muscle relaxants and nitrous oxide were studied over a period of one year. ETTs (Portex, high volume-low pressure cuff) sized 7.5mm and 8.5 mm ID, were used for female and male patients respectively. After intubation, the tracheal cuffs were filled with air by an operating room assistant (ORA), blinded to the study design. One of the five ORAs, each with at least 15 years of experience, was randomly asked to assess the cuff pressures by digital palpation and rate it as overinflated (OI), satisfactory (S) or underinflated (UI). The pressures were measured by both monitors and then readjusted to 25 mm Hg by altering the cuff-volume. Thereafter, pressures were checked every 15 min for 90 minutes, by both monitors. Any patient with an audible air leak at this pressure was excluded from the study.
OI S UI
Results The demographic data is shown in Table 1. Two patients with an air leak at 25 mm Hg, due to an undersized ETT, were excluded from the study. The palpatory assessment and the recorded cuff-pressures, at the time of intubation, were tabulated (Table 2). Table 3 shows the statistical analysis of the readings by the two monitors in the satisfactory group. The cuff pressure distribution in this group (Fig. 3), reveals that 40% cases had higher than desired cuff pressure. The mean values in both groups were also high, with maximum upto 60mm Hg, as measured on the standard monitor. The difference between
n=5 n=66 n=7
Cuff pressure** Improvised Standard 80 35.6 15.1
80.8 36 17
* overinflated (OI), satisfactory (S), underinflated (UI); ** mean value (mm Hg) Table 3 Improvised vs Standard monitor in satisfactory group – z test
Mean Range Pearson Correlation z
Improvised
Standard
35.5 22-60 0.98 0.32
36 24-60
the two monitors was not significant, at 95% confidence limits (z= 0.32). The Pearson Correlation (0.98) between the two monitors was close to 1, which signifies the high degree of correlation between the readings of the two groups. Fig. 4 shows the rise of pressures beyond the normal range with the use of nitrous oxide.
Discussion Tracheal intubation provides a reliable and patent airway in general anaesthesia and critical care setting. Low cuff pressure increases the risk of gas leak, pulmonary aspiration and nosocomial infections whereas overinflation may lead to mucosal ischaemia and its complications [5, 6]. Assessment of the adequacy of cuff pressure by digital palpation is only a subjective method unable to detect high cuff pressures [7]. Some MJAFI, Vol. 62, No. 3, 2006
Tracheal Cuff Pressure Monitoring
authors have also observed that in high-compliance endotracheal tube, cuff pressure increases very slowly, between pressures of 13 and 27mmHg, after which the addition of small volumes increases the cuff pressure substantially [8]. Macroscopic examination of the tracheal mucosa by a fiberoscope via an ETT during general anaesthesia by Sajedi et al [9], has shown significantly large number of tracheal mucosal lesions at the site of cuff, associated with high cuff pressures. The tracheal cuff pressures should be routinely checked for all intubated patients [10]. Low tissue perfusion, hypoxaemia, anaemia, metabolic acidosis and uncontrolled diabetes mellitus are some of the conditions in the critically ill which predispose patients to develop morbid postintubation sequelae [3, 11]. Spittle and Beavis, [12] in their survey found that only 13% of ICUs routinely monitor cuff pressures and 3% record the pressure on the patient chart. Vyas et al [10] studied 32 patients in the ICU and found that 62% had higher than acceptable cuff pressures. They surveyed a part of United Kingdom and discovered that 75% ICUs never routinely checked cuff pressures. The improvised tracheal cuff pressure monitor can provide a fair degree of cuff-pressure assessment in the absence of a standard monitor. However, the improvised monitor has several limitations. The scale is 2mm Hg as compared to 1mm Hg in the standard monitor. The commercially available monitor can auto correct, and maintain pressure once corrected. The improvised monitor, cannot autocorrect and results in a small amount of air leak when detached from the pilot balloon. Further modification to the improvised equipment, with the addition of a three-way stop cock with a syringe attached to one end, is suggested to minimise this air pressure leak. It is also recommended by the authors that this monitor be connected and left attached to the pilot cuff for continuous monitoring. During anaesthesia, it should be considered that nitrous oxide, diffuses easily into the endotracheal tube cuffs, increasing the cuff pressure [4]. Various methods have been used to prevent the unpredictable rise in cuff pressures during general anaesthesia including filling of cuffs with anaesthetic mixtures or isotonic saline [13]. Special ETTs like Brandt or Lanz are also described in contemporary literature, which have pressure regulating
MJAFI, Vol. 62, No. 3, 2006
245
system in their cuffs, but their prohibitive high costs is the limiting factor. The authors recommend that every institution should have a protocol for monitoring tracheal cuff pressures [14] and further studies on the subject would help in formulating a standard protocol. Conflicts of Interest None identified References 1. Fernandez R, Blanch L, Mancebo J, Bonsoms N. Endotracheal tube cuff pressure assessment: pitfalls of finger estimation and need for objective measurement. Crit Care Med 1990; 18: 1423-6. 2. Guyton AC. The systemic circulation. In: Guyton AC, editor. Medical Physiology. 10th ed. Philadelphia : WB Saunders, 2000; 218-28. 3. Henkel H, Gretcher C. Relation of tracheal cuff pressure to tracheal morbidity after extubation. Anaesthesiology 2001; 95: 5. 4. Dullenkopf A, Gerber AC. Nitrous oxide diffuses into tracheal tube cuffs: comparison of 5 different tracheal tube cuffs. Acta Anaesthesiol Scand 2004; 48:1180. 5. Sathish SK, Young PJ. Overinflation of tracheal tube cuff: a case for routine monitoring. Critical Care 2002; 6 (Supp 1) : 37S. 6. Spittle N, McCluskey A. Lesson of the week: tracheal stenosis after intubation. Br J Anaesth 2000; 321:1000-2. 7. Blaz JRC, Navarro, et al. Endotracheal tube cuff pressure: need for precise measurement. Sao Paulo Med J 1999; 117: 230-8. 8. Byrd RA, Mascia MF. What is the endotracheal tube cuff pressure in a cross-section of intubated patients? Anesthesiology 1996; 85 (Suppl 3A): 982S. 9. Sajedi P, Marooffi V. The macroscopic changes of tracheal mucosa following tight vs loose control of tracheal tube cuff pressure. Acta Anaesthesiol 2002; (Suppl 40):117S-120S. 10. Vyas DI, Inweregbn K, Pittard A. Measurement of tracheal cuff pressure in critical care. Anaesthesia 2002; 57: 275-7. 11. A Millard. Double respiratory sequelae of head injury: subglottic stenosis and bilateral pneumothoraces. Br J Anaesth 2003; 90: 94-6. 12. Spittle CSN, Beavis SE. Do you measure tracheal cuff pressure? A survey of clinical practice. Br J Anaesth 2001; 87:344-5. 13. Pivoz, Reuven MD. Intracuff pressure and tracheal morbidity: Influence of filling cuff with saline during nitrous oxide anaesthesia. Survey of Anaesthesiology 2002; 46: 222. 14. Nightangle P, Clayton J. Intensive care services. In : Royal College of Anaesthetists Compendium, Tracheal Tube Cuff Pressure. Raising the standard. 2000; Chapter 8, Audit 2.
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