Tracheal tube cuff pressure depends on the anaesthesiologist’s experience. A follow-up study
*Magdalena A. Wujtewicz, Wioletta Sawicka, Radosław Owczuk, Anna Dylczyk-Sommer, Maria Wujtewicz
Department of Anaesthesiology and Intensive Therapy, Medical University of Gdańsk
- Fig. 1. Distribution of CP values in 2002
- Fig. 2. Distribution of CP values in the present study
- Fig. 3. Comparison of CP values in the respective groups of physicians (x; 95% confidence interval)
- Table 1. The number of physicians in the respective study groups and number of measurements in each group
Background. Excessive tracheal tube cuff pressure can cause ischemia of the tracheal mucosa, and possible serious complications, such as tracheal stenosis, formation of tracheo-oesophageal fistula or even life-threatening haemorrhage. Inadequate cuff pressure increases the risk of aspiration of gastric contents.
Methods. The cuff pressures were analysed on the basis of the anaesthesiologists’ experience. The results were compared to those obtained during the previous study which had been conducted seven years earlier (2002). The physicians were divided into three groups, according to their experience: group I – less than 2 years of practice; group II – 2 to 10 years of practice; and group III – over 10 years of practice. High-volume, low-pressure tubes were used for intubation. The anaesthesiologists were not informed of the planned audit.
Results. Statistical analysis demonstrated significant differences between cuff pressure readings in the respective study groups. Cuff pressures in group II (p<0.05) and group III (p<0.0005) were greater than those in group I. In 2002, no statistically significant differences had been observed between the three groups (p=0.1156). When comparing results from 2002 and present one differences were observed inside individual groups, concerning group II (p<0.05) and group III (p<0.0005).
Conclusion. There is a tendency to overinflation of endotracheal tube cuffs in all groups. This problem is more common in the group of highly experienced anaesthesiologists, and is more more prevalent at present than in 2002.
High pressure in the tracheal tube cuff may result in various complications, of which tracheal mucosal ischaemia is the one most commonly reported . It may also lead to tracheal stenosis, formation of tracheo-oesophageal fistula or even life-threatening haemorrhage . Overinflation of the sealing cuff may induce its herniation and thus result in airway obstruction. The most grave yet rare complication is the rupture of the tracheal wall [3, 4, 5, 6]. Less severe side effects, producing discomfort reported by patients, include post-intubation pharyngodynia and hoarseness .
Moreover, cuff hypoinflation increases the risk of aspiration of gastric contents.
It should be expected that the greater the seniority and professional experience of anaesthetists, the higher the level of their awareness of such risks. In the previous report , the authors demonstrated that the seniority and the professional experience of anaesthetists had no influence on reaching the desired pressures in the tracheal tube cuff. Moreover, the tendency to overinflate the cuff was observed. The results described then were presented to the anaesthetic staff; the necessity of cuff pressure (CP) monitoring was emphasized, and after seven years the study was conducted again to compare the results.
The Independent Bioethics Committee for Scientific Research of the Medical University of Gdansk, Poland approved the study protocol. The design of the study required no deviation from the routine clinical practice; therefore patients` informed consent was not needed.
As in the previous study, the anaesthetists were divided into three groups of different seniority and the resultant various levels of experience in anaesthetic practice. Group I included physicians of less than 2 years of seniority, group II – 2-10 years of seniority, group III – over 10 years of experience.
CPs in tracheal tubes were measured exclusively in patients qualified for elective surgical interventions. High-volume low-pressure tubes were used for intubation: Kendall-Curity (The Kendall Comp, USA), Portex Profile Soft-Seal Cuff (Portex Ltd, UK) and Mallinckrodt Hi-Lo (Mallinckrodt Medical, Ireland). Tracheal tube cuffs were filled with air using standard syringes. Each cuff was filled by a qualified member of the anaesthetic staff.
CP values were measured using the manual manometer (PORTEX, Smiths Medical Inc., UK); the normal value range was 16-26 cm H2O (1.56-2.54 kPa). The mixture of 30% oxygen and 70% nitrous oxide was used for inhalation general anaesthesia. Measurements were performed up to 30 min after intubation. Both the physicians and anaesthetic nurses were not previously informed of the planned audit. If an abnormal pressure finding was observed, cuff filling was corrected. Results were analysed according to the physician’s experience and seniority and compared to the ones from the previous study .
Data were tested for normality with the Shapiro and Wilk W test. Intergroup comparisons were performed using the ANOVA test, followed by the Fisher’s post-hoc LSD test. In most groups, the distribution of a variable (cuff pressure) was right-skewed. Distributions were normalized using logarithmization of data (natural logarithm); it resulted in exclusion of 3 measurements, in which the result was 0 (one in group I in the present study and two in group III in 2002). P<0.05 was considered to be significant.
Table 1 presents the number of physicians in the respective study groups and the number of measurements in each group performed in 2002 and presently.
At present, in group I, 13 (25.5%) measurements of CP were within the reference range, 26 (51%) – above and 12 (23.5%) – below this range. In 2002, the following numbers and percentages were found: 16 (33%), 23 (47.9%) and 9 (18.75%), respectively.
In the present study, in group II, 15 (22.4%) measurements were within normal limits, 46 (68.65%) – higher and 6 (8.95%) – lower than the normal levels whereas in 2002, 17 (27.5%), 36 (58%) and 9 (14.5%), respectively.
In the present study, in group III only 2 (4.8%) CP measurements were within the normal limits, 39 (92.8%) were above and 1 (2.4%) result was below the limits. In 2002, those measurements in group III were: 10 (23.5%), 20 (46.5%) and 13 (30%) respectively. Median values of CP in each group of the present study exceeded the upper limit. Figure 1 presents the distribution of values recorded in 2002 and Figure 2 – at present.
The present findings showed considerably lower values of CP in group I compared to group II (p<0.05) and III (p<0.0005). In 2002, no significant differences were observed between the three groups (p=0.1156). When comparing our two study periods, differences were observed inside individual groups, which concerned group II (p<0.05) and group III (p<0.0005) (Fig. 3).
Widespread use of tracheal tubes with low-pressure high-volume cuffs resulted in decreased risk of excessive pressure upon the tracheal wall. It was demonstrated, however, that application of such tubes couldn’t prevent cuff overinflation; since safe CP values can easily be exceeded, CP should be routinely monitored .
According to Sathish Kumar and Young , cuff pressures higher than normal limits are observed more often than those below them. Our observations revealed similar tendency. Prolonged excessive cuff inflation may lead to post-intubation tracheal stenosis . Such a complication may be dangerous for the patient, difficult to manage and at times surgical correction may be necessary .
Macroscopic lesions of the tracheal mucosa can be observed both during cuff inflation with monitoring air leakage without or with manometer. In the latter case, patients had less severe lesions and experienced lesser post-intubation pharyngeal pain . On the other hand, relationship between hypoinflation and increased risk of aspiration of gastric contents with pulmonary complications was confirmed in patients treated in intensive therapy units . Cuff pressures below the desired range of values were also observed in some patients in the presented study. The introduction of a new type of tubes (low-volume, low-pressure) may reduce the risk of air shunting along the cuff folds .
The results of the presented study and of other investigators  suggest that anaesthetists should measure the pressure in the tracheal tube cuff using a manometer routinely, irrespective of their seniority and professional experience. This should result in adequate cuff filling and decrease the risk of both hyper- and hypoinflation-related complications. Palpation in order to assess the adequacy of cuff inflation is not sufficient, as demonstrated by some authors .
Comparison of CP readings from two periods of our measurements indicates that monitoring of the cuff filling remains insufficient.
Hyperinflation of the cuff is most prominent in the group of highly experienced anaesthetists. This fact is extremely alarming, particularly that in the Polish system of medical education the residents during specialist trainings in anaesthesiology are not entitled to administer anaesthesia and work on their own unless supervised by experienced anaesthetists.
Despite the necessity of cuff pressure measurements after intubation, as demonstrated by the results of the 2002 study, a tendency to overinflate the cuff is found in all the groups of various professional experiences in anaesthesiology, which is more commonly observed amongst highly experienced anaesthetists of the greatest seniority, who should guide their junior colleagues during anaesthetic trainings.
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*Magdalena A. Wujtewicz
Katedra i Klinika Anestezjologii
i Intensywnej Terapii UM w Gdańsku
ul. Dębinki 7, 80-211 Gdańsk
tel.: 0-58 349 24 06, fax: 0-58 349 11 82