CLINICAL FEATURE KEYWORDS Endotracheal tube / Cuff pressure / Cuff inflation techniques Provenance and Peer review: Unsolicited contribution; Peer reviewed; Accepted for publication June 2013.
Do current methods for endotracheal tube cuff inflation create pressures above the recommended range? A review of the evidence by Thomas Grant Correspondence address: c/o AfPP, Daisy Ayris House, 42 Freeman’s Way, Harrogate, HG£ 1DH. Email: [email protected]
Inflation and measurement of endotracheal (ET) tube cuff pressure is often not seen as a critical aspect of care in surgical patients. The morbidity associated by an overinflated cuff has been regularly highlighted in literature, for example mucosal ulceration (Combes et al 2001) and vocal cord paralysis (Holley & Gildea 1971). This article will outline techniques for the methods of inflation based on the latest scientific evidence. The author will seek to examine if intraoperative cuff assessment and monitoring should become routine for the anaesthetic practitioner and if current practice for inflating cuffs creates pressures outside the safe range. Introduction
Pathophysiology
Endotracheal tubes are used to maintain a patient’s airway when they are unable to breathe for themselves, paralysed under general anaesthetic (Al-metwalli et al 2011). The cuff that encompasses the lower part of the tube sits in the trachea where it is inflated by the anaesthetist or anaesthetic practitioner to a desired level. This level of inflation must ensure that gas cannot leak around the cuff, and that stomach contents cannot reflux, which could lead to pulmonary aspiration (Dullenkopf et al 2003).
An inflated cuff exerts pressure on the tracheal wall. The pressure inside the cuff is a good representation of the pressure on the tracheal wall (Sultan et al
Intubation with an ET tube is a very common procedure worldwide. It is performed up to 20 million times annually in the United States alone. The earliest use of tracheal intubation to support ventilation in humans is thought to have been around 460-380 BC by Hippocrates (Sultan et al 2011). The invention of the Macintosh curved laryngoscope blade in 1943 made tracheal intubation more accessible to physicians and it then became very popular in surgery and anaesthesia (Roth & Katz 2008). This literature review will focus on endotracheal tubes and their use in the perioperative environment. It is not within the scope of this review to cover long term endotrachael use for ventilation of intensive care patients. 292
2011). The pressure caused by the cuff on the trachea creates a seal. The first reason for this seal is to improve the likelihood that set ventilator volumes will be delivered to the patient, along with accurate end tidal
HIGH-VOLUME LOW-PRESSURE (HVLP) CUFFS
LOW-VOLUME HIGH-PRESSURE (LVHP) CUFFS
FEATURE
• More of the cuff is in contact with the trachea so the pressure is spread across the surface area. • There are folds in the cuff walls which allow fluid leakage.
• Only a small part of the cuff is in contact with the trachea so there is less surface area to spread the pressure. • There are no folds in the cuff.
OUTCOME FOR THE PATIENT
• Less pressure on trachea resulting in fewer postoperative complications secondary to cuff pressure e.g. sore throat. • Fluid could leak into the lungs causing infection and a longer hospital stay.
• Very high pressure on the trachea with the potential to cause pressure injury. • Assuming there is a seal, no fluids will leak past the cuff.
Table 1 HVLP and LVHP cuffs (Yarham & Young 2008) December 2013 / Volume 23 / Issue 12 / ISSN 1750-4589
CLINICAL FEATURE
The pressure caused by the cuff on the trachea creates a seal
volumes (Guyton et al 1997). Secondly, the seal prevents fluid passing the cuff and entering the lungs (Vyas et al 2002) which could cause postoperative complications such as nosocomial pulmonary infections (Tobin & Grenvik 1984). The amount of pressure from the cuff to occlude the trachea successfully is measured in centimetres of water (cmH2O) and can range from 20-50cmH2O (Sengupta el al 2004, Rose et al 2009). Serious complications can arise from overinflation of the ET tube cuff, for example a rupture of the trachea or even eventual death (Gottschalk et al 2003). These have been reduced since the introduction of low-pressure, high-volume cuffs, however the newer tubes at high pressures can still cause unnecessary damage and pain, in addition to the surgical pain felt by the patient emerging from anaesthesia in the recovery room. The advantages and disadvantages of the different cuffs are listed in Table 1. Brimacome et al (1999) and other authors (Seegobin & van Hasselt 1984, Cooper & Grillo 1969) have described the locations where pressure is exerted on the trachea and the consequences of high pressure on these areas. Their studies showed that
pressure is highest on the anterior wall and lowest posteriorly. This was shown to be due to the membranous features of the posterior wall and the tougher cartilaginous wall on the anterior side. On this softer, membranous posterior wall, pressures above 30cmH2O proved too much and hypoperfusion was evident. Hypoperfusion is a result of circulatory deficiencies (in this case pressure on the trachea occluding local capillaries) and is evidenced by an insufficient supply of oxygen to sustain the demand of tissues in the area, leading to cellular damage and death (Hu et al 2012). The blood supply reduced further as the pressure increased until it was completely obstructed at pressures above 50cmH2O (Mehta & Mickiewicz 1984). High pressures such as these could cause tracheal rupture (Fan et al 2004) and mucosal bleeding (Berlauk 1986). Many other studies have agreed with these pressure ranges and a safe range between 20-30cmH2O is consistent in the literature (Coffin et al 2008, Lucangelo et al 2008, Seegobin & van Hasselt 1986, Rello et al 1996).
Cuff pressure Table 2 shows factors which affect cuff pressure during anaesthesia and surgery.
Cuff assessment Al-metwalli et al (2011) conducted a randomised, blind study to determine the safest method of cuff inflation and assessment. Seventy-five patients took part in the study and were randomly assigned into three groups: • the control group (n=25) where the cuff was inflated to 25cmH2O • the sealing group (n=25) where the cuff was inflated to prevent air leaks at airway pressure of 20cmH2O • the finger group (n=25) where the cuff was inflated using the pilot balloon palpitation method. All cuffs were tested on the volume of air used to fill the cuff and the cuff pressure using a manometer. None of the patients developed an air leak around the cuff. The mean cuff pressure was significantly higher in the finger group (48cmH2O), as was the incidence of post operative airway complaints. In the finger group 40% of patients reported a sore throat, compared with 12% in both the control group and the sealing group. It is interesting to note the volume of air required to fill the cuffs in all three groups. Only tube sizes of 7.5mm (for females)
NITROUS OXIDE ANAESTHESIA
Cuff pressure increases when nitrous oxide is used because the gas diffuses into the cuff (Stanley et al 1974, Raeder et al 1985).
LAPAROSCOPIC SURGERY
As the intra-abdominal pressure increases due to carbon dioxide insufflation, the pressure in the cuff also increases (Yildirim et al 2012).
HEAD POSITION
In the flexed position, the pressure of the anterior part of the tube on the laryngopharynx was higher than in the neutral position. Pressure on tracheal mucosa does not increase, despite an increase in cuff pressure, probably due to a more even distribution of pressure over the cuff surface in this position. In the extended position, the pressure against the anterior tip and posterior cuff increased (Knowlson & Basset 1970). In the rotated position, the pressure at the anterior tip and lateral wall increased (Brimacombe et al 1999).
TEMPERATURE
As the air inside the cuff heats from room temperature to body temperature, a small rise in cuff pressure is seen. A greater increase would be seen in hypothermic patients who are warmed after intubation (Atlas 2005).
Table 2 Factors affecting cuff pressure December 2013 / Volume 23 / Issue 12 / ISSN 1750-4589
293
CLINICAL FEATURE
Do current methods for endotracheal tube cuff inflation create pressures above the recommended range? A review of the evidence Continued
and 8mm (for males) were used and the mean volume required for the control group (25cmH2O) was 4.3ml; the sealing group (20cmH2O) required 3.8ml and the finger group (48cmH2O) required 6.8ml. The study concluded that, although using the pilot balloon for estimation of cuff pressure is the most commonly used technique, it is unreliable and could result in a higher incidence of laryngotracheal complaints post operatively. This conclusion is supported by other studies (Fernandez et al 1990, Parwani et al 2007). The study was relatively small and compared only two different tube sizes on seventy-five patients. Different results may have been found with a larger number of participants and a range of different tube sizes, which would have reflected a more accurate analysis of an average cuff pressure and encompassed more variables. Jain and Tripathi (2011) also showed the unreliability of the manual method of cuff assessment. The authors wanted to see if the cuffs would stay within the recommended range of 20-30cmH2O by using the pilot balloon. Two groups were pressure exerted on the trachea depends of the compliance of the cuff and the trachea. Having the correct cuff pressure is important for patient safety, but it is not straightforward thing to measure. Simply connecting the manometer to the pilot balloon can cause a drop in pressure, by approximately 2cmH2O per measurement (Sole et al 2008, Blanch 2004), which has the potential to cause a leak. Precision in measurements of lung ventilation control, ventilator measurements and capnography may also be lost. This is particularly important in patients with reduced lung compliance that require a tight pulmonary pressure control (de Souza & Botrel 2003). Studies have shown that a single measurement of cuff pressure could cause a 9.87% drop on end-tidal volume (Bolzan et al 2012).
Complications of changing practice Whilst there is evidence to suggest that cuff pressure has a direct link to postoperative airway complications, morbidity secondary to the use of ET tubes is contributed to by a variety of 294
factors. If new methods for cuff inflation are to be commonly used in practice, this may create further complications. For example, if stethoscope guided inflation was to become mandatory, evidence from the small trial suggests that it would create lower pressures on the trachea. Lower pressures could allow micro aspirations into the lungs (Yarham & Young 2008).
Conclusion At present, endotracheal tube cuffs are too often being overinflated by clinicians. Current practice for cuff inflation is below the standard needed to maintain a consistent safe pressure and this may in turn cause damage to the patient. In trials which looked into complications from overinflating ET tube cuffs, there has been a lack of standardised intubating conditions and this may distort the results. Further research is needed in many aspects of cuff inflation and assessment before intraoperative assessment becomes compulsory. However, if inflation methods were improved, there may not be a need for such assessment. Stethoscope guided inflation had the best results in trials; however the small patient size used makes the results less reliable. A larger study should be constructed to assess the viability of this technique. In summary, correct cuff inflation techniques could be one method of reducing the number of patients with postoperative airway complaints.
References Al-metwalli RR, Al-Ghamdi AA, Sayed Sadek HA et al 2011 Is sealing cuff pressure, easy, reliable and safe technique for endotracheal tube cuff inflation? A comparative study Saudi Journal of Anaesthesia 5 (2) 185-9 Atlas GM 2005 A mathematical model of differential tracheal tube cuff pressure: effects of diffusion and temperature Journal of Clinical Monitoring and Computing 19 415-25 Berlauk JF 1986 Prolonged endotracheal intubation vs tracheostomy Critical Care Medicine 14 742-5 Blanch PB 2004 Laboratory evaluation of 4 brands of endotracheal tube cuff inflator Respiratory Care 49 (2) 166-73 Bolzan DW, Guizilini S, Faresin SM et al 2012 Endotracheal tube cuff pressure assessment manoeuvre induces drop of expired tidal volume in the postoperative of coronary artery bypass grafting Journal of Cardiothoracic Surgery 7 53 Brimacombe J, Keller C, Giampalmo M et al 1999 Direct measurement of mucosal pressures exerted by cuff and non-cuff portions of tracheal tubes
with different cuff volumes and head and neck positions British Journal of Anaesthesia 73 786-7 Coffin S, Klompas M, Classen D 2008 Strategies to prevent ventilator-associated pneumonia in acute care hospitals Infection Control and Hospital Epidemiology 29 31-40 Combes X, Schauvliege F, Peyrouset O 2001 Intracuff pressure and tracheal morbidity: influence of filling with saline during nitrous oxide anaesthesia Anesthesiology 95 1120-4 Cooper JD, Grillo HC 1969 Experimental production and prevention of injury due to cuffed tracheal tubes Surgery, Gynaecology & Obstetrics 129 1235-41 de Souza H, Botrel SR, Esophageal temperature probe as a cause of air leak around the endotracheal tube cuff Internet Journal of Anesthesiology 7 Dullenkopf A, Gerber A, Weiss A 2003 Fluid leakage past tracheal tube cuffs: Evaluation of the new microcuff endotracheal tube Intensive Care Medicine 29 1849-53 Fan CM, Ko PC, Tsai KC 2004 Tracheal rupture complicating emergent endotracheal intubation American Journal of Emergency Medicine 22 289-93 Fernandez R, Blanch L, Mancebo J et al 1990 Endotracheal tube cuff pressure assessment: Pitfalls of finger estimation and need for objective measurement Critical Care Medicine 18 1426-32 Guyton DC, Barlow MR, Besselievre TR 1997 Influence of airway pressure on minimum occlusive endotracheal tube cuff pressure Critical Care Medicine 25 91-4 Holley HS, Gildea JE 1971 Vocal cord paralysis after tracheal intubation Journal of the American Medical Association 215 281-4 Hu YB, Laine AG, Wang S, Solis TR 2012 Combined central venous oxygen saturation and lactate as markers of occult hypoperfusion and outcome following cardiac surgery Journal of Cardiothoracic & Vascular Anaesthesia 26 52-7 Jain MK, Tripathi CB 2011 Endotracheal tube cuff pressure monitoring during neurosurgery - manual vs. automatic method Journal of Anaesthesiology Clinical Pharmacology 27 (3) 358-361 Knowlson GT, Bassett HF 1970 The pressure exerted on the trachea by endotracheal inflatable cuffs British Journal of Anaesthesia 48 105-10 Kumar RD, Hirsch NP 2011 Clinical evaluation of stethoscope-guided inflation of tracheal tube cuffs Anaesthesia 66 1012-16 Lucangelo U, Zin W, Antonaglia V et al 2008 Effect of positive expiratory pressure and type of tracheal cuff on the incidence of aspiration in mechanically ventilated patients in an intensive care unit Critical Care Medicine 36 409-13 Mehta S, Mickiewicz M 1984 Pressure in large volume, low pressure cuffs: its significance, measurement and regulation Intensive Care Medicine 11 267-72 Parwani V, Hoffman RJ, Russell BC et al 2007 Practicing paramedics cannot generate or estimate safe endotracheal tube cuff pressure using standard techniques Prehospital Emergency Care 11 307-11
December 2013 / Volume 23 / Issue 12 / ISSN 1750-4589
CLINICAL FEATURE
Raeder JC, Borchgrevnik PC, Sellevold OM 1985 Tracheal tube cuff pressures: the effects of different gas mixtures Anaesthesia 40 (5) 444-7 Rello J, Sonora R, Jubert P et al 1996 Pneumonia in intubated patients: role of respiratory airway care American Journal of Critical Care Medicine 154 111-15 Rose BO, Kyle B, Koshy-Delaffon A, Cregg R 2009 Endotracheal tube cuff pressure are too high during anaesthesia European Journal of Anaesthesiology 26 Roth Y, Katz J 2008 A brief history of tracheostomy and tracheal intubation, from the Bronze Age to the Space Age Critical Care Medicine 44 222-8 Seegobin RD, van Hasselt GL 1984 Endotracheal cuff pressure and tracheal mucosal blood flow: endoscopic study of effects of four large volume cuffs British Medical Journal 288 965-8 Seegobin R, van Hasselt G 1986 Aspiration beyond endotracheal cuffs Canadian Anaesthetists’ Society Journal 33 273-9 Sengupta P, Sessler D, Maglinger P et al 2004 Endotracheal tube cuff pressure in three hospitals, and the volume required to produce an appropriate cuff pressure BMC Anesthesiology 4
Sole ML, Aragon D, Bennett M, Johnson RL 2008 Measurement of endotracheal tube cuff pressure: how difficult can it be? AACN Advance Critical Care 19 (2) 235-243 Stanley TH, Kawamura R, Graves C 1974 The effects of nitrous oxide on the volume and pressure of endotracheal tube cuffs Anaesthesiology 41 256-62 Sultan P, Carvalho B, Rose BO, Cregg R 2011 Endotracheal tube cuff pressure monitoring: a review of the evidence Journal of Perioperative Practice 21 379-86 Tobin MJ, Grenvik A 1984 Nosocomial lung infection and its diagnosis Critical Care Medicine 12 191-9 Vyas D, Inweregbu K, Pittard A 2002 Measurement of tracheal tube cuff pressure in critical care Anaesthesia 57 275-7
About the author Thomas Grant Studying for: DipHE Operating Department Practice Student ODP with placements in anaesthetics, surgery and recovery, Royal Bournemouth Hospital
No competing interests declared
Members can search all issues of the BJPN/JPP published since 1998 and download articles free of charge at www.afpp.org.uk. Access is also available to non-members who pay a small fee for each article download.
Yarham S, Young P 2008 Ventilator associated pneumonia and new airway technologies Trauma 10 71-83 Yildirim ZP, Uzunkov A, Cigdem A et al 2012 Changes in cuff pressure of endotracheal tube during laparoscopic and open abdominal surgery Surgical Endoscopy 26 298-401
December 2013 / Volume 23 / Issue 12 / ISSN 1750-4589
295
Disclaimer The views expressed in articles published by the Association for Perioperative Practice are those of the writers and do not necessarily reflect the policy, opinions or beliefs of AfPP. Manuscripts submitted to the editor for consideration must be the original work of the author(s). © 2013 The Association for Perioperative Practice All legal and moral rights reserved.
The Association for Perioperative Practice Daisy Ayris House 42 Freemans Way Harrogate HG3 1DH United Kingdom Email: [email protected] Telephone: 01423 881300 Fax: 01423 880997 www.afpp.org.uk
Do current methods for endotracheal tube cuff inflation create pressures above the recommended range? A review of the evidence by Thomas Grant Correspondence address: c/o AfPP, Daisy Ayris House, 42 Freeman’s Way, Harrogate, HG£ 1DH. Email: [email protected]
Inflation and measurement of endotracheal (ET) tube cuff pressure is often not seen as a critical aspect of care in surgical patients. The morbidity associated by an overinflated cuff has been regularly highlighted in literature, for example mucosal ulceration (Combes et al 2001) and vocal cord paralysis (Holley & Gildea 1971). This article will outline techniques for the methods of inflation based on the latest scientific evidence. The author will seek to examine if intraoperative cuff assessment and monitoring should become routine for the anaesthetic practitioner and if current practice for inflating cuffs creates pressures outside the safe range. Introduction
Pathophysiology
Endotracheal tubes are used to maintain a patient’s airway when they are unable to breathe for themselves, paralysed under general anaesthetic (Al-metwalli et al 2011). The cuff that encompasses the lower part of the tube sits in the trachea where it is inflated by the anaesthetist or anaesthetic practitioner to a desired level. This level of inflation must ensure that gas cannot leak around the cuff, and that stomach contents cannot reflux, which could lead to pulmonary aspiration (Dullenkopf et al 2003).
An inflated cuff exerts pressure on the tracheal wall. The pressure inside the cuff is a good representation of the pressure on the tracheal wall (Sultan et al
Intubation with an ET tube is a very common procedure worldwide. It is performed up to 20 million times annually in the United States alone. The earliest use of tracheal intubation to support ventilation in humans is thought to have been around 460-380 BC by Hippocrates (Sultan et al 2011). The invention of the Macintosh curved laryngoscope blade in 1943 made tracheal intubation more accessible to physicians and it then became very popular in surgery and anaesthesia (Roth & Katz 2008). This literature review will focus on endotracheal tubes and their use in the perioperative environment. It is not within the scope of this review to cover long term endotrachael use for ventilation of intensive care patients. 292
2011). The pressure caused by the cuff on the trachea creates a seal. The first reason for this seal is to improve the likelihood that set ventilator volumes will be delivered to the patient, along with accurate end tidal
HIGH-VOLUME LOW-PRESSURE (HVLP) CUFFS
LOW-VOLUME HIGH-PRESSURE (LVHP) CUFFS
FEATURE
• More of the cuff is in contact with the trachea so the pressure is spread across the surface area. • There are folds in the cuff walls which allow fluid leakage.
• Only a small part of the cuff is in contact with the trachea so there is less surface area to spread the pressure. • There are no folds in the cuff.
OUTCOME FOR THE PATIENT
• Less pressure on trachea resulting in fewer postoperative complications secondary to cuff pressure e.g. sore throat. • Fluid could leak into the lungs causing infection and a longer hospital stay.
• Very high pressure on the trachea with the potential to cause pressure injury. • Assuming there is a seal, no fluids will leak past the cuff.
Table 1 HVLP and LVHP cuffs (Yarham & Young 2008) December 2013 / Volume 23 / Issue 12 / ISSN 1750-4589
CLINICAL FEATURE
The pressure caused by the cuff on the trachea creates a seal
volumes (Guyton et al 1997). Secondly, the seal prevents fluid passing the cuff and entering the lungs (Vyas et al 2002) which could cause postoperative complications such as nosocomial pulmonary infections (Tobin & Grenvik 1984). The amount of pressure from the cuff to occlude the trachea successfully is measured in centimetres of water (cmH2O) and can range from 20-50cmH2O (Sengupta el al 2004, Rose et al 2009). Serious complications can arise from overinflation of the ET tube cuff, for example a rupture of the trachea or even eventual death (Gottschalk et al 2003). These have been reduced since the introduction of low-pressure, high-volume cuffs, however the newer tubes at high pressures can still cause unnecessary damage and pain, in addition to the surgical pain felt by the patient emerging from anaesthesia in the recovery room. The advantages and disadvantages of the different cuffs are listed in Table 1. Brimacome et al (1999) and other authors (Seegobin & van Hasselt 1984, Cooper & Grillo 1969) have described the locations where pressure is exerted on the trachea and the consequences of high pressure on these areas. Their studies showed that
pressure is highest on the anterior wall and lowest posteriorly. This was shown to be due to the membranous features of the posterior wall and the tougher cartilaginous wall on the anterior side. On this softer, membranous posterior wall, pressures above 30cmH2O proved too much and hypoperfusion was evident. Hypoperfusion is a result of circulatory deficiencies (in this case pressure on the trachea occluding local capillaries) and is evidenced by an insufficient supply of oxygen to sustain the demand of tissues in the area, leading to cellular damage and death (Hu et al 2012). The blood supply reduced further as the pressure increased until it was completely obstructed at pressures above 50cmH2O (Mehta & Mickiewicz 1984). High pressures such as these could cause tracheal rupture (Fan et al 2004) and mucosal bleeding (Berlauk 1986). Many other studies have agreed with these pressure ranges and a safe range between 20-30cmH2O is consistent in the literature (Coffin et al 2008, Lucangelo et al 2008, Seegobin & van Hasselt 1986, Rello et al 1996).
Cuff pressure Table 2 shows factors which affect cuff pressure during anaesthesia and surgery.
Cuff assessment Al-metwalli et al (2011) conducted a randomised, blind study to determine the safest method of cuff inflation and assessment. Seventy-five patients took part in the study and were randomly assigned into three groups: • the control group (n=25) where the cuff was inflated to 25cmH2O • the sealing group (n=25) where the cuff was inflated to prevent air leaks at airway pressure of 20cmH2O • the finger group (n=25) where the cuff was inflated using the pilot balloon palpitation method. All cuffs were tested on the volume of air used to fill the cuff and the cuff pressure using a manometer. None of the patients developed an air leak around the cuff. The mean cuff pressure was significantly higher in the finger group (48cmH2O), as was the incidence of post operative airway complaints. In the finger group 40% of patients reported a sore throat, compared with 12% in both the control group and the sealing group. It is interesting to note the volume of air required to fill the cuffs in all three groups. Only tube sizes of 7.5mm (for females)
NITROUS OXIDE ANAESTHESIA
Cuff pressure increases when nitrous oxide is used because the gas diffuses into the cuff (Stanley et al 1974, Raeder et al 1985).
LAPAROSCOPIC SURGERY
As the intra-abdominal pressure increases due to carbon dioxide insufflation, the pressure in the cuff also increases (Yildirim et al 2012).
HEAD POSITION
In the flexed position, the pressure of the anterior part of the tube on the laryngopharynx was higher than in the neutral position. Pressure on tracheal mucosa does not increase, despite an increase in cuff pressure, probably due to a more even distribution of pressure over the cuff surface in this position. In the extended position, the pressure against the anterior tip and posterior cuff increased (Knowlson & Basset 1970). In the rotated position, the pressure at the anterior tip and lateral wall increased (Brimacombe et al 1999).
TEMPERATURE
As the air inside the cuff heats from room temperature to body temperature, a small rise in cuff pressure is seen. A greater increase would be seen in hypothermic patients who are warmed after intubation (Atlas 2005).
Table 2 Factors affecting cuff pressure December 2013 / Volume 23 / Issue 12 / ISSN 1750-4589
293
CLINICAL FEATURE
Do current methods for endotracheal tube cuff inflation create pressures above the recommended range? A review of the evidence Continued
and 8mm (for males) were used and the mean volume required for the control group (25cmH2O) was 4.3ml; the sealing group (20cmH2O) required 3.8ml and the finger group (48cmH2O) required 6.8ml. The study concluded that, although using the pilot balloon for estimation of cuff pressure is the most commonly used technique, it is unreliable and could result in a higher incidence of laryngotracheal complaints post operatively. This conclusion is supported by other studies (Fernandez et al 1990, Parwani et al 2007). The study was relatively small and compared only two different tube sizes on seventy-five patients. Different results may have been found with a larger number of participants and a range of different tube sizes, which would have reflected a more accurate analysis of an average cuff pressure and encompassed more variables. Jain and Tripathi (2011) also showed the unreliability of the manual method of cuff assessment. The authors wanted to see if the cuffs would stay within the recommended range of 20-30cmH2O by using the pilot balloon. Two groups were pressure exerted on the trachea depends of the compliance of the cuff and the trachea. Having the correct cuff pressure is important for patient safety, but it is not straightforward thing to measure. Simply connecting the manometer to the pilot balloon can cause a drop in pressure, by approximately 2cmH2O per measurement (Sole et al 2008, Blanch 2004), which has the potential to cause a leak. Precision in measurements of lung ventilation control, ventilator measurements and capnography may also be lost. This is particularly important in patients with reduced lung compliance that require a tight pulmonary pressure control (de Souza & Botrel 2003). Studies have shown that a single measurement of cuff pressure could cause a 9.87% drop on end-tidal volume (Bolzan et al 2012).
Complications of changing practice Whilst there is evidence to suggest that cuff pressure has a direct link to postoperative airway complications, morbidity secondary to the use of ET tubes is contributed to by a variety of 294
factors. If new methods for cuff inflation are to be commonly used in practice, this may create further complications. For example, if stethoscope guided inflation was to become mandatory, evidence from the small trial suggests that it would create lower pressures on the trachea. Lower pressures could allow micro aspirations into the lungs (Yarham & Young 2008).
Conclusion At present, endotracheal tube cuffs are too often being overinflated by clinicians. Current practice for cuff inflation is below the standard needed to maintain a consistent safe pressure and this may in turn cause damage to the patient. In trials which looked into complications from overinflating ET tube cuffs, there has been a lack of standardised intubating conditions and this may distort the results. Further research is needed in many aspects of cuff inflation and assessment before intraoperative assessment becomes compulsory. However, if inflation methods were improved, there may not be a need for such assessment. Stethoscope guided inflation had the best results in trials; however the small patient size used makes the results less reliable. A larger study should be constructed to assess the viability of this technique. In summary, correct cuff inflation techniques could be one method of reducing the number of patients with postoperative airway complaints.
References Al-metwalli RR, Al-Ghamdi AA, Sayed Sadek HA et al 2011 Is sealing cuff pressure, easy, reliable and safe technique for endotracheal tube cuff inflation? A comparative study Saudi Journal of Anaesthesia 5 (2) 185-9 Atlas GM 2005 A mathematical model of differential tracheal tube cuff pressure: effects of diffusion and temperature Journal of Clinical Monitoring and Computing 19 415-25 Berlauk JF 1986 Prolonged endotracheal intubation vs tracheostomy Critical Care Medicine 14 742-5 Blanch PB 2004 Laboratory evaluation of 4 brands of endotracheal tube cuff inflator Respiratory Care 49 (2) 166-73 Bolzan DW, Guizilini S, Faresin SM et al 2012 Endotracheal tube cuff pressure assessment manoeuvre induces drop of expired tidal volume in the postoperative of coronary artery bypass grafting Journal of Cardiothoracic Surgery 7 53 Brimacombe J, Keller C, Giampalmo M et al 1999 Direct measurement of mucosal pressures exerted by cuff and non-cuff portions of tracheal tubes
with different cuff volumes and head and neck positions British Journal of Anaesthesia 73 786-7 Coffin S, Klompas M, Classen D 2008 Strategies to prevent ventilator-associated pneumonia in acute care hospitals Infection Control and Hospital Epidemiology 29 31-40 Combes X, Schauvliege F, Peyrouset O 2001 Intracuff pressure and tracheal morbidity: influence of filling with saline during nitrous oxide anaesthesia Anesthesiology 95 1120-4 Cooper JD, Grillo HC 1969 Experimental production and prevention of injury due to cuffed tracheal tubes Surgery, Gynaecology & Obstetrics 129 1235-41 de Souza H, Botrel SR, Esophageal temperature probe as a cause of air leak around the endotracheal tube cuff Internet Journal of Anesthesiology 7 Dullenkopf A, Gerber A, Weiss A 2003 Fluid leakage past tracheal tube cuffs: Evaluation of the new microcuff endotracheal tube Intensive Care Medicine 29 1849-53 Fan CM, Ko PC, Tsai KC 2004 Tracheal rupture complicating emergent endotracheal intubation American Journal of Emergency Medicine 22 289-93 Fernandez R, Blanch L, Mancebo J et al 1990 Endotracheal tube cuff pressure assessment: Pitfalls of finger estimation and need for objective measurement Critical Care Medicine 18 1426-32 Guyton DC, Barlow MR, Besselievre TR 1997 Influence of airway pressure on minimum occlusive endotracheal tube cuff pressure Critical Care Medicine 25 91-4 Holley HS, Gildea JE 1971 Vocal cord paralysis after tracheal intubation Journal of the American Medical Association 215 281-4 Hu YB, Laine AG, Wang S, Solis TR 2012 Combined central venous oxygen saturation and lactate as markers of occult hypoperfusion and outcome following cardiac surgery Journal of Cardiothoracic & Vascular Anaesthesia 26 52-7 Jain MK, Tripathi CB 2011 Endotracheal tube cuff pressure monitoring during neurosurgery - manual vs. automatic method Journal of Anaesthesiology Clinical Pharmacology 27 (3) 358-361 Knowlson GT, Bassett HF 1970 The pressure exerted on the trachea by endotracheal inflatable cuffs British Journal of Anaesthesia 48 105-10 Kumar RD, Hirsch NP 2011 Clinical evaluation of stethoscope-guided inflation of tracheal tube cuffs Anaesthesia 66 1012-16 Lucangelo U, Zin W, Antonaglia V et al 2008 Effect of positive expiratory pressure and type of tracheal cuff on the incidence of aspiration in mechanically ventilated patients in an intensive care unit Critical Care Medicine 36 409-13 Mehta S, Mickiewicz M 1984 Pressure in large volume, low pressure cuffs: its significance, measurement and regulation Intensive Care Medicine 11 267-72 Parwani V, Hoffman RJ, Russell BC et al 2007 Practicing paramedics cannot generate or estimate safe endotracheal tube cuff pressure using standard techniques Prehospital Emergency Care 11 307-11
December 2013 / Volume 23 / Issue 12 / ISSN 1750-4589
CLINICAL FEATURE
Raeder JC, Borchgrevnik PC, Sellevold OM 1985 Tracheal tube cuff pressures: the effects of different gas mixtures Anaesthesia 40 (5) 444-7 Rello J, Sonora R, Jubert P et al 1996 Pneumonia in intubated patients: role of respiratory airway care American Journal of Critical Care Medicine 154 111-15 Rose BO, Kyle B, Koshy-Delaffon A, Cregg R 2009 Endotracheal tube cuff pressure are too high during anaesthesia European Journal of Anaesthesiology 26 Roth Y, Katz J 2008 A brief history of tracheostomy and tracheal intubation, from the Bronze Age to the Space Age Critical Care Medicine 44 222-8 Seegobin RD, van Hasselt GL 1984 Endotracheal cuff pressure and tracheal mucosal blood flow: endoscopic study of effects of four large volume cuffs British Medical Journal 288 965-8 Seegobin R, van Hasselt G 1986 Aspiration beyond endotracheal cuffs Canadian Anaesthetists’ Society Journal 33 273-9 Sengupta P, Sessler D, Maglinger P et al 2004 Endotracheal tube cuff pressure in three hospitals, and the volume required to produce an appropriate cuff pressure BMC Anesthesiology 4
Sole ML, Aragon D, Bennett M, Johnson RL 2008 Measurement of endotracheal tube cuff pressure: how difficult can it be? AACN Advance Critical Care 19 (2) 235-243 Stanley TH, Kawamura R, Graves C 1974 The effects of nitrous oxide on the volume and pressure of endotracheal tube cuffs Anaesthesiology 41 256-62 Sultan P, Carvalho B, Rose BO, Cregg R 2011 Endotracheal tube cuff pressure monitoring: a review of the evidence Journal of Perioperative Practice 21 379-86 Tobin MJ, Grenvik A 1984 Nosocomial lung infection and its diagnosis Critical Care Medicine 12 191-9 Vyas D, Inweregbu K, Pittard A 2002 Measurement of tracheal tube cuff pressure in critical care Anaesthesia 57 275-7
About the author Thomas Grant Studying for: DipHE Operating Department Practice Student ODP with placements in anaesthetics, surgery and recovery, Royal Bournemouth Hospital
No competing interests declared
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Yarham S, Young P 2008 Ventilator associated pneumonia and new airway technologies Trauma 10 71-83 Yildirim ZP, Uzunkov A, Cigdem A et al 2012 Changes in cuff pressure of endotracheal tube during laparoscopic and open abdominal surgery Surgical Endoscopy 26 298-401
December 2013 / Volume 23 / Issue 12 / ISSN 1750-4589
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