Studies

General anesthesia with an endotracheal tube (ETT) is performed safely countless times every day with an estimated anesthetic complication rate between 0.0606 to 0.0905 occurrences per 1,000 surgical discharges.¹ Post-operative sore throat (POST) and post-operative hoarseness (PH), however, remain a common complaint of intubated patients with an estimated incidence of between 14-70%.² High endotracheal tube cuff pressure and large size ETTs have been implicated as causative factors^. These two factors have also been implicated in the catastrophic complications of tracheal stenosis and recurrent laryngeal injuries.^3,4 The simple method of regulating cuff pressure with a cuff manometer and the use of smaller endotracheal tubes could limit these complications.

Literature Review:

In a thesis study by Evans ⁵ three different means of inflating the ETT pilot balloon were compared: the injection and palpation method, the minimum occlusive technique and the set volume of air. Forty-six percent of the ETT cuffs were inflated using the pilot balloon palpation technique, 28% using the set volume technique and 26% using the minimum occlusive technique. Regardless of the technique, none of the cuff pressures was within the acceptable range of 20-30 cm H₂O. pressure. Thirteen percent of cuff pressures were below the minimum value necessary to prevent aspiration and 87% were inflated above the accepted value, risking tracheal ischemia.

In a study by Liu (2010), 509 patients from 4 university hospitals requiring general anesthesia with an endotracheal tube were studied to investigate the short-term (hours) impact of endotracheal intubation and cuff pressure. They were divided into two groups: control group did not measure cuff pressure and the study group had the ETTc measured. Additionally, 20 patients whose duration of anesthesia was between 120 and 180 minutes were selected from each group for fiberoptic bronchoscopy immediately after extubation. There was no significant difference in sex, age, height, weight or procedural length, The mean endotracheal tube cuff (ETTc) pressure measured after manual palpation was 43 +/- 23.3 mmHg with the highest at 210 mmHg. The incidence of post procedural sore throat, hoarseness and blood-streaked expectoration in the control group was significantly higher than in the study group. Fiberoptic bronchoscopy in the 20 previous selected patients from each group showed that the tracheal mucosa was injured in varying degrees but the injury was more severe in the control group. The authors suggest ETTc pressure monitoring and controlling in reducing complications.⁶

                        Wujtewicz (2009) analyzed ETT cuff pressure on the basis of the aneaesthesiolgist’s experience. Results were compared to those obtained during a previous study that was done in 2002. The physicians were divided into three groups according to experience: group 1 – less than 2 years of practice, group II – 2-10 years of practice and group III – over 10 years practice. He found a “tendency toward over-inflation of endotracheal tube cuffs with the problem more common in highly experienced anesthesiologists.” He also found “over-inflation was more prevalent in 2009 than in 2002”.⁷ The graph below is the data from Wujtewicz comparing 2002 to 2009:

Curiel⁸ studied forty patients who required endotracheal intubation for elected surgery. Patients who had ETT cuff pressures equal or less that 42 mmHg were assigned to group A, and those with higher than 42 mmHg to group B. Tracheal pain was assessed at 60 minutes and 24 hours after extubation. The tracheal pain was similar at 60 minutes after extubation but at 24 hours persisted only in 10% of subjects in group A and 53.3% of the subjects in group B, p= 0.00001. The authors concluded that there is a need for routine monitoring of cuff pressure to avoid pressures that exceeds the appropriate range of 20-30 mmHg.

In a study by Galinski⁹ that measured the ETTc pressures of 107 patients intubated either by emergency out-of-hospital medical teams or transferred patients. Eighty-eight of the patients were intubated out-of-hospital and twenty-two were transfers between hospitals. The authors found 79% to be greater than 27 cm H₂O with a mean pressure of 56 cm (SD+/- 34 cm H₂O) for the out-of –hospital patients and a mean pressure of 69 cm H₂O (SD+/- 37 cm H₂O) for the transferred patients.

 In a study from 2012, researchers measured the cuff pressure of 136 patients in the operating room. Most of the pressures fell outside safe limits of 20-30 cm H₂O. The minimum cuff pressure was 1 cm H₂O to a maximum of 120 with a mean of 38 and SD of 31

            The problem of improper cuff inflation is not new. In 1988, Koay¹¹ studied 200 patients undergoing general surgery with an endotracheal tube. The patients were divided into 2 groups. The first group (control) had the pilot balloons inflated with 5 cc of air. There was no record of intra-cuff pressure in this group. In the study group, the cuffs were inflated using the ‘minimum occlusion’ technique. The mean intracuff pressure measured in the study group was 118.9 mmHg (SD = 54.3). The authors also describe that the use of an endotracheal tube causes mucosal damage at two main sites: the posterior larynx and the anterior and lateral aspect of the trachea between the third and tenth rings. The authors state, “The standard endotracheal tube acts as a curved lever and the posterior larynx, especially the arytenoid and cricoid acts, as a fulcrum when the tube is introduced into the trachea.” They also point out even a relatively short period of endotracheal intubation can result in vocal cord paralysis and tracheal stenosis.

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