Sumario Vol.43 - Nº 3 Julio-Septiembre 2014 Imprimir sólo la columna central

Association between Corrected Endotracheal Cuff Pressures
in Upper Airway with Post-Extubation Complications

Juan Ignacio Fernández, Gisel Ramírez,
Carla Guimelli, Diana Romberg, Eduardo Perna

Servicio de Kinesiología, Servicio de Hematología. División de Insuficiencia Cardíaca. Instituto de Cardiología de Corrientes "Juana F. Cabral". (3400) Corrientes, Argentina.
E-mail
 
Recibido 30-MAR-2014- ACEPTADO después de revisión 30-MAYO-2014.
The authors declare not having conflicts of interest
 
Rev Fed Arg Cardiol. 2014; 43(3): 121-124
ABSTRACT

Background: While it is recommended to keep the value of the endotracheal cuff pressure (ECP) between 20 and 40 cmH2O in critically ill and intubated patients, with invasive mechanical ventilation (IMV) with positive pressure, the optimum value associated with lower incidence of complications has not been established.
Objectives: To correlate the ECP between 20 and 40 cmH2O and the complication rate in post-extubationupper airway.
Methods: This prospective study included patients admitted at the Instituto de Cardiología Corrientes receiving IMV for over 4 hours and survived until extubation without tracheostomy. The population was divided into groups 1, 2 and 3 according to the calibration performed by a manometer of the ECP to 20, 30 and 40 cmH2O, respectively. A structured questionnaire was performed 48 to 72 hours post-extubation, to identify respiratory complications.
Results: One hundred and twenty seven patients were included with a mean age of 61 (± 14) years. The cause of IMV was surgical in 89% of cases and 11% for clinical diagnosis, during 37±7 hours. Mean ECP was 65 cmH2O before setting to recommended values. The incidence of complications in groups of 20, 30 and 40 cmH2O was coughing (76, 87, and 90%, p = NS), odynophagia (45, 52, and 62%, p = NS), expectoration (13, 5 and 19%, p = NS) and dysphonia (33, 40, and 38%, p = NS), respectively.
Conclusions: Despite a high incidence of diseases related to upper airway post-extubation, no differences related to level of ECP were found. These results demonstrate that maintaining levels of 20 to 40 cmH2O is equivalent.
Key words: Endotracheal cuff.Mechanical ventilation.Post-extubation complications.

 

INTRODUCTION
In patients with invasive mechanical ventilation (IMV), insufflating the endotracheal cuff is a necessary strategy to ensure a proper occlusion of the airway and protecting from aspiring contaminated oropharyngeal secretions. Current recommendations from experts advice keeping the endotracheal tube cuff pressures (ETCP) between 20 and 30 cmH2O with a maximumlimit of 40 cmH2O, although other papers mention that even 40-50 cmH2O could be reached [1-4].

However, cuff pressure control is not a usual practice. A tube cuff with insufficient or too much pressure is associated to complications like coughing, dysphonia, odynophagia, hemoptoic expectoration, tracheal stenosis, tracheomalacia and pneumonia associated to the ventilator [5]. This has been shown mainly in patients with extended intubation periods.

In different clinical institutions the routine practice consists of estimating the endotracheal tube cuff pressure feeling the external pilot cuff; however, this technique is inaccurate, and in it only 1/3 of measurements is within the desired range [6-8].

There are no standards as to the method and the frequency to monitor ETCP, and in most of American institutions, respiratory therapists are in charge of controlling it, with a reported interval of 8 to 12 hours [9].

The goal of this study was to record the pressures used in the usual practice, and to correlate ETCP between 20 and 40 cmH2O with the rate of complications in the post-extubation upper airway.

 

METHODS

Patients
Prospective study that included patients older than 18 years that required orotracheal intubation and IMV for at least 4 hours, admitted into the ICU, coronary unit and cardiovascular recovery unit, who survived without requiring tracheostomy until extubation and were capable of answering a set of questions evaluating complications. Those that were admitted intubated, referred from other centers or with history of tracheotomy were excluded.

Protocol
In all cases the intubation procedure was performed by anesthesiologists and MD therapists using ALFADOVES endotracheal tubes (ETT) with inner diameter between 7.5 and 8.5 mm with high volume and low pressure cuffs. Initially the cuff was insufflated using the traditional methods by a syringe and feeling the pilot cuff without requiring instrumentation assistance. After 4 hours, the first measurement was made by a SIMS-Portex manometer, Keene, New Hampshire, and later the patients were assigned to the following groups: Group 1: 20 cmH2O, Group 2: 30 cmH2O, and Group 3: 40 cmH2O, pressures that were kept for the ventilation period, monitoring their value every 6 hours until extubation.

Between the 48 and 72 hours after extubation, the patients were questioned by a kinesiologist who did not know the assigned group, using a closed set of questions (Appendix 1), with dichotomous answers, recording the complications, which included coughing, odynophagia, dysphonia, and hemoptoic expectoration, which represented the primary endpoint [10]. The incidence of post-extubation events was evaluated.

Statistical analysis
The analysis of data was made with the SPSS Inc. software, version 21.0. The qualitative variables were expressed in percentages and were compared with the Chi-squared test or Fisher’s exact test. The quantitative variables were expressed as average ± standard deviation and were compared with the Anova test. A P ≤0.05 was considered significant.

 

RESULTS
During the term of the study between July 1st, 2011 and March 31st 2012, 166 patients met the inclusion criteria, with 10 being excluded by tracheotomy and 29 by death. The final sample was of 127 individuals assigned to the different groups of 20 (n=45), 30 (n=42) and 40 cmH2O (n=40). The general characteristics of the population are found in Table 1, where it is possible to verify that two thirds were males, with differences between the arms in risk factors.

Table 1. Characteristics of the population

 

Group 1

Group 2

Group 3

 

N patients 45 42 40  
Age in years, average ±SD 62±14 60±14 61±14 0,906
Male gender, (%) 69 81 72 0,42
Weight in kg, average ± SD 75,5±14,3 77,8±13,9 77±15,8 0,76
COPD (%) 15 19 12 0,718
Smoking (%) 51 69 60 0,234
Diabetes (%) 15 21 37 0,054

The average of initial pressures, before the calibration of the maintenance pressure, were for groups 1, 2 and 3 of 68 ±35, 57±30 and 68±32 mmHg respectively (p=0.21).

The incidence of complications for the arms of 20, 30 and 40 cmH2O was: coughing 76, 87 and 90% (p=NS), odynophagia 45, 52 and 62% (p=NS), expectoration 13, 5 and 19% (p=NS) and dysphonia 33, 40 and 38% (p=NS), respectively (Figure 1).

Figura 1

In Table 2 we provide details on the average time of intubation and post-extubation events in every arm. Only respiratory infection was diagnosed with a higher frequency in the 40 cmH2O group.

Table 2. Post-extubation events

 

Group 1

Group 2

Group 3

P=

Intubation hours (average) 25 37 43 0,28
Atelectasis, N (%) 27 (60) 23(55) 22(55) 0,85
Pleural effusion, N (%) 18 (40) 22(52) 22(55) 0,32
Respiratory infection, N (%) 3 (7) 2(5) 9(22) 0,01
Mediastinitis, N (%) 1 (2) 2(5) 1(2) 0,76

 

 

DISCUSSION
This study shows that the maintenance of ETCP between 20 and 40 cmH2O, frequently monitored by trained staff, has a similar incidence of complications.

The cause of injury is considered in several studies as of multifactorial origin, caused by the artificial airway, the excessive tube cuff pressures, the term of the intubation, ETT movement, creating stress forces that lead to injury in the laryngotracheal mucosa [11]. Seegobin et al [1] in an in vitro study in 40 patients who underwent surgery, who were evaluated by endoscopic technique, showed a reduction in the tracheal mucosa blood flow when pressures greater than 40 cmH2O were used, and total obstruction with pressures greater than 50 cmH2O.

However, it is not clear whether there is a good correlation between the degree of damage to the mucosa and the severity of the symptoms in the patients, since the former are always subjective.

In our study, it was observed that only 30% of the population was within the study range in the first measurement, determining that the pilot cuff feeling as a method results in an ETCP higher than required to seal the airway. Parwani et al [12] showed that the pressure generated was greater than 108 cmH2O when this method was used. Jianhui Liu et al [10] determined that a proper control of ETCP with a manometer, even in terms that last only 1 to 3 hours, helps to reduce the complications related to endotracheal intubation.

This paper presents certain limitations. Between them, the small number of patients and the strict adjustment of the maintenance ETCP value. The questionnaire technique may have been a questionable instrument to evaluate and differentiate the pathogenesis of the complications. No histological studies or evaluations with fibrobronchoscopy were made to confirm tracheal injury, since it could be associated to other factors such as respiratory infection. The patients were followed for 48 hours after extubation, with no follow-up plan, until their recovery, and no long-term complications evaluation.

 

CONCLUSIONS
A proper control of ETCP at different levels within the recommended range did not show differences in the incidence of post-extubation complications. These results showed that maintaining levels from 20 to 40 cmH2O is equivalent.

 

• APPENDIX 1. Questionnaire of complications obtained from reference [10].

Have you suffered any of these symptoms in the post-extubation period?

Coughing Yes No
Sore throat Yes No
Hemoptoic expectoration Yes No
Dysphonia Yes No

 

REFERENCES

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  2. Nordin U, Lindholm CE, Wolgast M.Blood flow in the rabbit tracheal mucosa under normal conditions and under the influence of tracheal intubation.ActaAnaesthesiolScand1977; 21(2):81-94.
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  8. Stewart SL, Secrest JA, Norwood BR, et al. A comparison of endotracheal tube cuff pressures using estimation techniques and direct intracuff measurement. AANA J2003; 71(6): 443-7.
  9. Sole ML, Penoyer DA et al.Assessment of Endotracheal Cuff Pressure by Continuous Monitoring: A Pilot Study. Am J Crit Care 2009;18(2):133-43.
  10. Liu J, Zhang X, Gong W, et al. Correlations between controlled endotracheal tube cuff pressure and postprocedural complications: a multicenter study. AnesthAnalg. 2010;111(5):1133-7.
  11. Sue RD, Susanto I. Long-term complications of artificial airways. Clin Chest Med 2003; 24(3):457-71.
  12. Parwani V, Hoffman RJ, Russell A, et al.Practing paramedics cannot generate or estimate safe endotracheal tube cuff pressure using standard techniques. PrehospEmerg Care 2007; 11(3): 307-11.

 

Publication: September 2014



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