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Prevention of complications from prolonged tracheal intubation
Prevention of Complications from Prolonged Tracheal lntubation Frank R. Lewis, Jr, MD, San Francisco, California Richard M. Schlobohm, MD, San Francisco, California Arthur N. Thomas, MD, San Francisco, California
Prolonged intubation of the trachea in the treatment of acute respiratory failure has become commonplace in intensive care units (ICU) during the last decade. In our experience one fourth of all intubated and ventilated ICU patients require ventilator support for more than one week and 10 per cent require it for more than two weeks [I]. Severe complications such as tracheoesophageal fistula, tracheal stenosis, tracheoarterial fistula, and cuff trachiectasis can follow prolonged intubation [Z]. Most major tracheal complications result from excessive pressure by the endotracheal tube cuff, which may produce mucosal ulceration, cartilaginous destruction, tracheomalacia, and tracheal wall necrosis. The mucosa becomes ischemic when pressure exerted by the cuff exceeds capillary perfusion pressure, approximately 30 mm Hg [3]. If a pressure greater than 30 mm Hg is maintained for a prolonged period, progressive tracheal wall necrosis results with erosion into adjacent structures. Even though we understand what causes them, major tracheal complications continue to be frequently reported. Most physicians believe that a soft cuff on the endotracheal or tracheostomy tube provides adequate tracheal protection. Soft cuffs, however, can produce surprisingly high mucosal pressures and tracheal necrosis if the pressure used to inflate the cuff is not controlled. In the present report we studied eight commercially available soft cuff endotracheal tubes in vitro to determine what kind of pressures can result when these tubes are inflated within the trachea. We also analyzed how efforts to control inflation pressures in the cuffs of endotracheal tubes affected the incidence of major tracheal complications in our patients. From the Departments of Surgery and Anesthesiology, University of California School of Medicine, San Francisco General Hospital. This work was supported by USPHS Contract # 1-HR-429 15. Reprint requests should be addressed to Arthur N. Thomas, MD, Department of Surgery, University of California, San Francisco General Hospital, 1001 Potrero Avenue, San Francisco, California 94110.
459
In Vitro Experiments Methods
The following commercially marketed soft cuff endotracheal tubes of similar sizes were studied: Argyle; Harris-Lake; Lanz; National Catheter, Ohio; Portex; Shiley; and Surgitek. Each cuff was connected by a three-way stopcock to a 30 ml syringe and aneroid manometer. (Figure 1.) The aneroid manometer was calibrated with a reference mercury manometer. Air was aspirated from the cuff until it was empty. Then increments of air were introduced and the pressure within the cuff determined up to a final pressure of 100 mm Hg. This procedure was performed with each tube under three experimental conditions: (1) the cuff was inflated without being confined; (2) the cuff was inflated within an artificial trachea (a rigid plastic tube) 20.5 mm in diameter; and (3) the cuff was inflated within an artificial trachea 18.5 mm in diameter. These two sizes correspond to the upper limits of normal for the trachea in adult men and women, respectively [4-61. Results Results of the in vitro studies are presented in Figures 2 to 5. The symbols are explained in the legends. Figure 6 shows the eight tubes inflated simultaneously to a pressure of 20 mm Hg. Note that at this pressure the cuffs of the two
PRESSURE GAUGE
O-WAY
INFLATING SYRING
Figure 1. Schematic diagram of apparatus for measuring lntracuff pressure as a function of inflation volume.
The American Journal of Surgery
Complications of Tracheal lntubation
WARKIWAKE
10 VOLUME
15
20
ET TUBR O.Omm
25
OF AIR INJECTED
30 (ml)
35 VOLUME
OF AIR INJECTED (ml)
OVSB ; lb 115:o :5 ;o 3k VOLUME
OF AIR INJECTED (ml)
VOLUME
OF AIR INJECTED (ml)
Figures 2-5. intracuff pressure versus inflation volume for eight commercially available endotracheai tubes. The solid line represents inflation in open air, unconfined. The dashed line is inflation udthin a 20.5 mm artifkiai trachea and the doffed line is infiatkn in an 18.5 mm artificial trachea. The shaded horizontal band is tfte safe range of intracuff pressure, from 20 to 30 mm #g. The anow indicates tha point at which the endotracheai tube cuff seais wHhin the 20.5 mm atiifkiai trachea. Names of specific tubes are shown on each graph. Note that the horizontal scale is expanded twofold in Figure 3A.
Vdum9
135, March 1975
453
Lewis, Schlobohm, and Thomas
Figurye 6A. Simultaneous inflation of all eight tube cuffs to 20 mm Hg. The tubes are arranged alphabetically from left to right,, as follows: Argyle, Harris-Lake, Lanz, National Catheter, Ohio, Portex, Shiley, and Surgttek.
tubes on the left have not d&ended to the point where they would seal a large trachea, and the cuff of the tube on the right has not yet begun to distend.
Clinical Experience
cheostomy tubes were used. These tubes have an external pilot balloon connected to a soft, high compliance cuff. The physicial characteristics of the pilot balloon limit its pressure to less than 25 mm Hg over a wide range of inflation volumes. Thus, the pressure within the intratracheal cuff remains 25 mm Hg or less.
Methods
Results All patients admitted to the Medical-Surgical Intensive Care Unit of San Francisco General Hospital from 1970 to 1975 who required intubation and mechanical ventilation for more than 6 hours were included in the study. Ventilated patients represented 44 per cent of all ICU admissions during this period. Data regarding these patients were collected at the time of their discharge from the ICU and were stored in computer files. The patients were divided into two groups, corresponding to the periods when two different endotracheal tubes were used. During the initial thirty months of the study, from January 1970 to June 1972, Portex endotracheal and tracheostomy tubes were used, with the cuff prestretched before insertion according to the method described by Geffin and Pontoppidan [7]. This converts the slim silhouette, low volume cuff to a more distensible high volume cuff. During the latter forty-two months of the study, from July 1972 to December 1975, Lanz endotracheal and tra-
454
Table I presents the results of the clinical study. The incidence of major tracheal complications and related deaths decreased sharply after introduction of the controlled pressure tube. The eleven major complications during the first period consisted of four tracheoesophageal fistulas, one tracheoinnominate artery fistula, four cases of cuff trachiectasis, and two cases of tracheal stenosis. In the later period the two complications were tracheal stenosis and tracheoinnominate artery fistula. Tracheal stenosis developed in a patient who survived mechanical ventilation for adult respiratory distress syndrome for seventy-six days. At the time of operative resection his stenosis was found to be at the site of the tracheostomy stoma, not at the position of the endotracheal cuff. The tracheoinnominate artery fistula in the patient who died was shown at autopsy to be caused by erosion at the tip of the tracheostomy tube, not by tracheal ulceration at the cuff site. Neither complication, therefore, appeared to result from the endotracheal tube cuff.
The American Journal of Surgery
Complications of Tracheal lntubation
Figuj ‘e 68. Same as 6A, close up view. Note variability in distention of cuffs at same pressure.
Figur‘8 t?C. Same tube arrangement, with all cuffs inflated to 70 mm Hg. Note minimal change in volume of cuffs on first, seco nd, and seventh tubes.
455
Lewis, Schlobohm, and Thomas
TABLE I
l
Comparison of Major Tracheal Complications and Related Deaths with Use of 2 Different Endotracheal Tubes
Time Period
Number of Patients lntubated and Ventilated
Average Number of Days Ventilated per Patient
7/7Q to 6172 7172 to 72175
403 747
3.9 6.0
7 7 (2.7%) 2 (0.3%) (p <0.005)’
Deaths Due to Major Tracheal Complications 7 (7.7%) 7 (0.7 %) (p <0.07)’
Significance level by x2 test.
Although methods of mechanical ventilation changed during the time of this study, we are unaware of any factors that could have influenced these results other than introduction of the Lanz tube. During both periods, ventilation was normally maintained at a tidal volume of 10 to 15 ml/kg, using a volume-controlled ventilator. The mean duration of ventilation per patient increased from 3.9 days during the earlier period to 6.0 days during the later one, which would have been expected to increase the number of complications. The use of pulmonary end-expiratory pressure (PEEP) increased during the later period, which would be associated with increased intratracheal pressures. Thus, if PEEP had any influence, it should have increased the incidence of tracheal complications.
Comments
Figures 2 to 5 show that soft cuff tubes have major differences in distensibility, which significantly affect their safety. The tubes represented in Figures 2A, 2B, 5A, and 5B have steep pressure-volume inflation curves, even when unconfined. A change of inflation volume of 2 to 3 ml results in an intracuff pressure change of 30 to 40 mm Hg. In addition, none of the cuffs of these four tubes occluded the 20.5 mm artificial trachea at cuff pressures below 50 mm Hg. The tubes represented in Figures 3B, 4A, and 4B all have more distensible cuffs and all seal the large artificial trachea at cuff pressures below 20 mm Hg. Inevitably, however, they all have steep pressurevolume curves when confined within a trachea. The volume of air necessary to raise the cuff from the point of seal to an unsafe pressure (greater than 30 mm Hg) is only 2 to 3 ml. As shown by Ching and Nealon [B], it is unrealistic to expect that the inflation volume can be monitored this closely in a busy critical care unit. The Lanz tube, with characteristics defined in Figure 3A, was the only one tested that offered a wide enough latitude in inflation volume for safe operation. From the point of tracheal occlusion to an unsafe cuff pressure required 45 ml of additional air, and the pilot balloon had to be overdistended to
456
Number of Patients with Major Tracheal Complications
reach a cuff pressure above 30 mm Hg. The construction of the pilot balloon provides easy visual indication of the degree of inflation, and obviates the need to measure cuff pressures. The principal point is that any inflatable cuff, no matter how soft, is potentially hazardous when confined within the tracheal lumen with no safety mechanism. Pressure control is essential, preferably by some means that does not require much attention by ICU personnel. The external pressure regulating pilot balloon is the simplest practical method we are aware of that provides this control.* The use of intracuff pressure as a measure of cuff safety assumes that intracuff pressure is equal to lateral pressure exerted on the tracheal mucosa. The lateral pressure exerted on a confining cylinder may be less than the intracuff pressure, depending on the elasticity of the cuff. In actual use, there are two reasons why intracuff pressure is more relevant. First, in endotracheal tubes with soft, easily distensible cuffs (those in Figures 3B, 4A, and 4B) the cuff pressure required at the point of tracheal occlusion is minimal. Thus, the lateral wall pressure will be only 2 to 4 mm Hg less than intracuff pressure and the two may be considered to be the same. Second, and more importantly, measurement of lateral wall pressure in a cylindrical model may not be relevant to conditions of use. For example, a firm nasogastric tube in the esophagus of an intubated patient will displace the soft posterior wall of the trachea and indent the tracheal balloon. At the point of indentation the tracheal mucosa will be subjected to the full intracuff pressure because the compliant property of the elastic balloon is lost when it is indented to a flat or concave shape. Since this situation occurs commonly in practice, the tracheal mucosa will often be subjected to the full intracuff pressure. The clinical results show that continuous control * The Bivona, or Kamen-Wilkinson, endotracheal tube is specifically excluded from this discussion because it does not require cuff inflation and could not be tested by the technics used in this experiment.
The American Journal of Surgery
Complications of Tracheal lntubation
of endotracheal cuff pressure can sharply decrease cuff complications. The incidence of complications during the first thirty months of this study are similar to those reported by others [9,10]. To our knowledge this is the first large clinical series which has shown the value of a controlled pressure tube. Complications will continue to occur as a result of erosion at the tip of rigid tracheostomy tubes, but they appear to be infrequent. Complications related to the tracheostomy stoma remain a major problem after prolonged intubation, as exemplified by our patient with tracheal stenosis described earlier. Complications at this site may be minimized by relying on nasotracheal or orotracheal intubation in as many patients as possible. In our experience nasotracheal tubes are generally well tolerated, and can usually be maintained for 3 to 4 weeks. Thus, complications of tracheostomy can be decreased by avoiding tracheostomy in many patients who in the past would have been candidates for this procedure. We conclude that any endotracheal or tracheostomy tube must satisfy two conditions to be safe for prolonged use: (1) The endotracheal cuff must be compliant, deformable, and easily inflated to a diameter larger than the adult trachea at pressures below 30 mm Hg. (2) While in use the pressure within the cuff must be maintained below 30 mm Hg. This is most easily done with an external pilot balloon which automatically regulates pressure and does not require frequent checking or adjustment by ICU personnel. The importance of the first principle has been generally recognized, and there are many endotracheal tubes with high volume, low pressure cuffs currently available. The second principle, which has received less attention, is important and difficult to achieve in practice. This present study shows that major tracheal complications from prolonged endotracheal intubation can be decreased by attention to these principles.
Volume 135. March 1975
Summary
Eight commercially available soft cuff endotracheal tubes were studied to determine the relationship between inflation pressure distention of the cuff. Although the balloon cuff may be easily distensible in open air, when confined within the trachea small increments in the inflation volume may produce high pressures. This means that continuous external control of cuff pressure is required to prevent ischemia of the tracheal wall. Major tracheal complications in a busy ICU were examined before and after the introduction of a controlled pressure tube. Control of intratracheal cuff pressures decreased major tracheal complications tenfold and eliminated complications specifically related to the cuff. References 1. Lewis FR Jr, Blaisdell FW. Schlobohm RM: Incidence and outcome of posttraumatic respiratory failure. Arch Surg 112: 436, 1977. 2. Thomas AN: The diagnosis and treatment of tracheo-esophageal fistula caused by cuffed tracheal tubes. J Thorac Cardiovasc Surg 65: 2, 1973. 3. Knowlson GTG, Bassett HFM: The pressures exerted on the trachea by endotracheal inflatable cuffs. Br J Anaesfhesiol 42: 634, 1970. 4. Engel S: Lung Structure. Springfield, Illinois, Charles C Thomas, 1962, p 6. 5. von Hayek H: The Human Lung. New York, Hafner, 1960, p 65. 6. Jackson CM (ed): Morris’s Human Anatomy, 8th ed. P. Blakiston’s Sons, 1925, p 1256. 7. Geff in B, Pontoppidan H: Reduction of tracheal damage by the prestretching of inflatable cuffs. Anaesfhesiology 31: 462. 1969. 6. Ching NPH, Nealon TF Jr: Clinical experience with new lowpressure high-volume tracheostomy cuffs. NY State J A&d 74: 2379. 7974. 9. Andrews MJ, Pearson FG: Incidence and pathogenesis of tracheal injury following cuffed tube tracheostomy with assisted ventilation. Ann Surg 173: 249, 197 1. 10. Dane TEB. King EG: A prospective study of complications after tracheostomy for assisted ventilation. Chest 67: 398, 1975.
457
Prolonged intubation of the trachea in the treatment of acute respiratory failure has become commonplace in intensive care units (ICU) during the last decade. In our experience one fourth of all intubated and ventilated ICU patients require ventilator support for more than one week and 10 per cent require it for more than two weeks [I]. Severe complications such as tracheoesophageal fistula, tracheal stenosis, tracheoarterial fistula, and cuff trachiectasis can follow prolonged intubation [Z]. Most major tracheal complications result from excessive pressure by the endotracheal tube cuff, which may produce mucosal ulceration, cartilaginous destruction, tracheomalacia, and tracheal wall necrosis. The mucosa becomes ischemic when pressure exerted by the cuff exceeds capillary perfusion pressure, approximately 30 mm Hg [3]. If a pressure greater than 30 mm Hg is maintained for a prolonged period, progressive tracheal wall necrosis results with erosion into adjacent structures. Even though we understand what causes them, major tracheal complications continue to be frequently reported. Most physicians believe that a soft cuff on the endotracheal or tracheostomy tube provides adequate tracheal protection. Soft cuffs, however, can produce surprisingly high mucosal pressures and tracheal necrosis if the pressure used to inflate the cuff is not controlled. In the present report we studied eight commercially available soft cuff endotracheal tubes in vitro to determine what kind of pressures can result when these tubes are inflated within the trachea. We also analyzed how efforts to control inflation pressures in the cuffs of endotracheal tubes affected the incidence of major tracheal complications in our patients. From the Departments of Surgery and Anesthesiology, University of California School of Medicine, San Francisco General Hospital. This work was supported by USPHS Contract # 1-HR-429 15. Reprint requests should be addressed to Arthur N. Thomas, MD, Department of Surgery, University of California, San Francisco General Hospital, 1001 Potrero Avenue, San Francisco, California 94110.
459
In Vitro Experiments Methods
The following commercially marketed soft cuff endotracheal tubes of similar sizes were studied: Argyle; Harris-Lake; Lanz; National Catheter, Ohio; Portex; Shiley; and Surgitek. Each cuff was connected by a three-way stopcock to a 30 ml syringe and aneroid manometer. (Figure 1.) The aneroid manometer was calibrated with a reference mercury manometer. Air was aspirated from the cuff until it was empty. Then increments of air were introduced and the pressure within the cuff determined up to a final pressure of 100 mm Hg. This procedure was performed with each tube under three experimental conditions: (1) the cuff was inflated without being confined; (2) the cuff was inflated within an artificial trachea (a rigid plastic tube) 20.5 mm in diameter; and (3) the cuff was inflated within an artificial trachea 18.5 mm in diameter. These two sizes correspond to the upper limits of normal for the trachea in adult men and women, respectively [4-61. Results Results of the in vitro studies are presented in Figures 2 to 5. The symbols are explained in the legends. Figure 6 shows the eight tubes inflated simultaneously to a pressure of 20 mm Hg. Note that at this pressure the cuffs of the two
PRESSURE GAUGE
O-WAY
INFLATING SYRING
Figure 1. Schematic diagram of apparatus for measuring lntracuff pressure as a function of inflation volume.
The American Journal of Surgery
Complications of Tracheal lntubation
WARKIWAKE
10 VOLUME
15
20
ET TUBR O.Omm
25
OF AIR INJECTED
30 (ml)
35 VOLUME
OF AIR INJECTED (ml)
OVSB ; lb 115:o :5 ;o 3k VOLUME
OF AIR INJECTED (ml)
VOLUME
OF AIR INJECTED (ml)
Figures 2-5. intracuff pressure versus inflation volume for eight commercially available endotracheai tubes. The solid line represents inflation in open air, unconfined. The dashed line is inflation udthin a 20.5 mm artifkiai trachea and the doffed line is infiatkn in an 18.5 mm artificial trachea. The shaded horizontal band is tfte safe range of intracuff pressure, from 20 to 30 mm #g. The anow indicates tha point at which the endotracheai tube cuff seais wHhin the 20.5 mm atiifkiai trachea. Names of specific tubes are shown on each graph. Note that the horizontal scale is expanded twofold in Figure 3A.
Vdum9
135, March 1975
453
Lewis, Schlobohm, and Thomas
Figurye 6A. Simultaneous inflation of all eight tube cuffs to 20 mm Hg. The tubes are arranged alphabetically from left to right,, as follows: Argyle, Harris-Lake, Lanz, National Catheter, Ohio, Portex, Shiley, and Surgttek.
tubes on the left have not d&ended to the point where they would seal a large trachea, and the cuff of the tube on the right has not yet begun to distend.
Clinical Experience
cheostomy tubes were used. These tubes have an external pilot balloon connected to a soft, high compliance cuff. The physicial characteristics of the pilot balloon limit its pressure to less than 25 mm Hg over a wide range of inflation volumes. Thus, the pressure within the intratracheal cuff remains 25 mm Hg or less.
Methods
Results All patients admitted to the Medical-Surgical Intensive Care Unit of San Francisco General Hospital from 1970 to 1975 who required intubation and mechanical ventilation for more than 6 hours were included in the study. Ventilated patients represented 44 per cent of all ICU admissions during this period. Data regarding these patients were collected at the time of their discharge from the ICU and were stored in computer files. The patients were divided into two groups, corresponding to the periods when two different endotracheal tubes were used. During the initial thirty months of the study, from January 1970 to June 1972, Portex endotracheal and tracheostomy tubes were used, with the cuff prestretched before insertion according to the method described by Geffin and Pontoppidan [7]. This converts the slim silhouette, low volume cuff to a more distensible high volume cuff. During the latter forty-two months of the study, from July 1972 to December 1975, Lanz endotracheal and tra-
454
Table I presents the results of the clinical study. The incidence of major tracheal complications and related deaths decreased sharply after introduction of the controlled pressure tube. The eleven major complications during the first period consisted of four tracheoesophageal fistulas, one tracheoinnominate artery fistula, four cases of cuff trachiectasis, and two cases of tracheal stenosis. In the later period the two complications were tracheal stenosis and tracheoinnominate artery fistula. Tracheal stenosis developed in a patient who survived mechanical ventilation for adult respiratory distress syndrome for seventy-six days. At the time of operative resection his stenosis was found to be at the site of the tracheostomy stoma, not at the position of the endotracheal cuff. The tracheoinnominate artery fistula in the patient who died was shown at autopsy to be caused by erosion at the tip of the tracheostomy tube, not by tracheal ulceration at the cuff site. Neither complication, therefore, appeared to result from the endotracheal tube cuff.
The American Journal of Surgery
Complications of Tracheal lntubation
Figuj ‘e 68. Same as 6A, close up view. Note variability in distention of cuffs at same pressure.
Figur‘8 t?C. Same tube arrangement, with all cuffs inflated to 70 mm Hg. Note minimal change in volume of cuffs on first, seco nd, and seventh tubes.
455
Lewis, Schlobohm, and Thomas
TABLE I
l
Comparison of Major Tracheal Complications and Related Deaths with Use of 2 Different Endotracheal Tubes
Time Period
Number of Patients lntubated and Ventilated
Average Number of Days Ventilated per Patient
7/7Q to 6172 7172 to 72175
403 747
3.9 6.0
7 7 (2.7%) 2 (0.3%) (p <0.005)’
Deaths Due to Major Tracheal Complications 7 (7.7%) 7 (0.7 %) (p <0.07)’
Significance level by x2 test.
Although methods of mechanical ventilation changed during the time of this study, we are unaware of any factors that could have influenced these results other than introduction of the Lanz tube. During both periods, ventilation was normally maintained at a tidal volume of 10 to 15 ml/kg, using a volume-controlled ventilator. The mean duration of ventilation per patient increased from 3.9 days during the earlier period to 6.0 days during the later one, which would have been expected to increase the number of complications. The use of pulmonary end-expiratory pressure (PEEP) increased during the later period, which would be associated with increased intratracheal pressures. Thus, if PEEP had any influence, it should have increased the incidence of tracheal complications.
Comments
Figures 2 to 5 show that soft cuff tubes have major differences in distensibility, which significantly affect their safety. The tubes represented in Figures 2A, 2B, 5A, and 5B have steep pressure-volume inflation curves, even when unconfined. A change of inflation volume of 2 to 3 ml results in an intracuff pressure change of 30 to 40 mm Hg. In addition, none of the cuffs of these four tubes occluded the 20.5 mm artificial trachea at cuff pressures below 50 mm Hg. The tubes represented in Figures 3B, 4A, and 4B all have more distensible cuffs and all seal the large artificial trachea at cuff pressures below 20 mm Hg. Inevitably, however, they all have steep pressurevolume curves when confined within a trachea. The volume of air necessary to raise the cuff from the point of seal to an unsafe pressure (greater than 30 mm Hg) is only 2 to 3 ml. As shown by Ching and Nealon [B], it is unrealistic to expect that the inflation volume can be monitored this closely in a busy critical care unit. The Lanz tube, with characteristics defined in Figure 3A, was the only one tested that offered a wide enough latitude in inflation volume for safe operation. From the point of tracheal occlusion to an unsafe cuff pressure required 45 ml of additional air, and the pilot balloon had to be overdistended to
456
Number of Patients with Major Tracheal Complications
reach a cuff pressure above 30 mm Hg. The construction of the pilot balloon provides easy visual indication of the degree of inflation, and obviates the need to measure cuff pressures. The principal point is that any inflatable cuff, no matter how soft, is potentially hazardous when confined within the tracheal lumen with no safety mechanism. Pressure control is essential, preferably by some means that does not require much attention by ICU personnel. The external pressure regulating pilot balloon is the simplest practical method we are aware of that provides this control.* The use of intracuff pressure as a measure of cuff safety assumes that intracuff pressure is equal to lateral pressure exerted on the tracheal mucosa. The lateral pressure exerted on a confining cylinder may be less than the intracuff pressure, depending on the elasticity of the cuff. In actual use, there are two reasons why intracuff pressure is more relevant. First, in endotracheal tubes with soft, easily distensible cuffs (those in Figures 3B, 4A, and 4B) the cuff pressure required at the point of tracheal occlusion is minimal. Thus, the lateral wall pressure will be only 2 to 4 mm Hg less than intracuff pressure and the two may be considered to be the same. Second, and more importantly, measurement of lateral wall pressure in a cylindrical model may not be relevant to conditions of use. For example, a firm nasogastric tube in the esophagus of an intubated patient will displace the soft posterior wall of the trachea and indent the tracheal balloon. At the point of indentation the tracheal mucosa will be subjected to the full intracuff pressure because the compliant property of the elastic balloon is lost when it is indented to a flat or concave shape. Since this situation occurs commonly in practice, the tracheal mucosa will often be subjected to the full intracuff pressure. The clinical results show that continuous control * The Bivona, or Kamen-Wilkinson, endotracheal tube is specifically excluded from this discussion because it does not require cuff inflation and could not be tested by the technics used in this experiment.
The American Journal of Surgery
Complications of Tracheal lntubation
of endotracheal cuff pressure can sharply decrease cuff complications. The incidence of complications during the first thirty months of this study are similar to those reported by others [9,10]. To our knowledge this is the first large clinical series which has shown the value of a controlled pressure tube. Complications will continue to occur as a result of erosion at the tip of rigid tracheostomy tubes, but they appear to be infrequent. Complications related to the tracheostomy stoma remain a major problem after prolonged intubation, as exemplified by our patient with tracheal stenosis described earlier. Complications at this site may be minimized by relying on nasotracheal or orotracheal intubation in as many patients as possible. In our experience nasotracheal tubes are generally well tolerated, and can usually be maintained for 3 to 4 weeks. Thus, complications of tracheostomy can be decreased by avoiding tracheostomy in many patients who in the past would have been candidates for this procedure. We conclude that any endotracheal or tracheostomy tube must satisfy two conditions to be safe for prolonged use: (1) The endotracheal cuff must be compliant, deformable, and easily inflated to a diameter larger than the adult trachea at pressures below 30 mm Hg. (2) While in use the pressure within the cuff must be maintained below 30 mm Hg. This is most easily done with an external pilot balloon which automatically regulates pressure and does not require frequent checking or adjustment by ICU personnel. The importance of the first principle has been generally recognized, and there are many endotracheal tubes with high volume, low pressure cuffs currently available. The second principle, which has received less attention, is important and difficult to achieve in practice. This present study shows that major tracheal complications from prolonged endotracheal intubation can be decreased by attention to these principles.
Volume 135. March 1975
Summary
Eight commercially available soft cuff endotracheal tubes were studied to determine the relationship between inflation pressure distention of the cuff. Although the balloon cuff may be easily distensible in open air, when confined within the trachea small increments in the inflation volume may produce high pressures. This means that continuous external control of cuff pressure is required to prevent ischemia of the tracheal wall. Major tracheal complications in a busy ICU were examined before and after the introduction of a controlled pressure tube. Control of intratracheal cuff pressures decreased major tracheal complications tenfold and eliminated complications specifically related to the cuff. References 1. Lewis FR Jr, Blaisdell FW. Schlobohm RM: Incidence and outcome of posttraumatic respiratory failure. Arch Surg 112: 436, 1977. 2. Thomas AN: The diagnosis and treatment of tracheo-esophageal fistula caused by cuffed tracheal tubes. J Thorac Cardiovasc Surg 65: 2, 1973. 3. Knowlson GTG, Bassett HFM: The pressures exerted on the trachea by endotracheal inflatable cuffs. Br J Anaesfhesiol 42: 634, 1970. 4. Engel S: Lung Structure. Springfield, Illinois, Charles C Thomas, 1962, p 6. 5. von Hayek H: The Human Lung. New York, Hafner, 1960, p 65. 6. Jackson CM (ed): Morris’s Human Anatomy, 8th ed. P. Blakiston’s Sons, 1925, p 1256. 7. Geff in B, Pontoppidan H: Reduction of tracheal damage by the prestretching of inflatable cuffs. Anaesfhesiology 31: 462. 1969. 6. Ching NPH, Nealon TF Jr: Clinical experience with new lowpressure high-volume tracheostomy cuffs. NY State J A&d 74: 2379. 7974. 9. Andrews MJ, Pearson FG: Incidence and pathogenesis of tracheal injury following cuffed tube tracheostomy with assisted ventilation. Ann Surg 173: 249, 197 1. 10. Dane TEB. King EG: A prospective study of complications after tracheostomy for assisted ventilation. Chest 67: 398, 1975.
457