Assistant professor, Critical Care Medicine, Kobe University Hospital, Hyogo

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1 Changes in endotracheal tube cuff pressure in mechanically ventilated adult patients Asuka Motoyama1, Shota Asai1, Hiroyuki Konami1, Yuri Matsumoto1, Takuyo Misumi2, Hideaki Imanaka, MD3, Masaji Nishimura, MD4 1 Medical student, The University of Tokushima Graduate School, Tokushima asuka.motoyama214@gmail.com, showter.-_-.q0v0p.-o-.v-.-v@docomo.ne.jp, m-fc17.team-mik.ykkn@softbank.ne.jp, yurimatsu@mb4.tcn.ne.jp 2 Assistant professor, Critical Care Medicine, Kobe University Hospital, Hyogo misumi@med.kobe-u.ac.jp 3 Professor, Emergency and Disaster Medicine, Tokushima University Hospital imanakah@clin.med.tokushima-u.ac.jp 4 Professor, Emergency and Critical Care Medicine, Tokushima University Hospital nmasaji@clin.med.tokushima-u.ac.jp Corresponding author: Hideaki Imanaka, M.D. Department of Emergency and Disaster Medicine, The Tokushima University Hospital Kuramoto Tokushima, Japan Telephone No: 088(633)9347, Fax No: 088(633)9339 This study was performed in the ICU of Tokushima University Hospital. No parts of this study have been presented elsewhere. No author has any conflict of interest concerning the devices discussed in this report. Support was provided from institutional and departmental sources. Page 1/ Motoyama A ABSTRACT Background: When an endotracheal tube (ETT) with a cuff is used for mechanical ventilation, to prevent gas leakage and injury to the trachea, cuff pressure should be maintained within proper range. Although cuff pressure is affected by many factors, changes in cuff pressure have not been fully investigated in critically ill patients. For example, it is unknown whether frequent adjustment can avoid cuff pressure variation. We investigated the effect of frequent adjustment on cuff pressure variation when mechanically ventilating critically ill patients. Methods: In a prospective observational design, we enrolled 27 patients undergoing mechanical ventilation in our ICU. Cuff pressure was recorded every 2 hours and was

2 adjusted to 24 cmh2o each time. We analyzed the distribution of cuff pressure and investigated the relationships of cuff pressure to body position, severity score, intubation period, ventilatory settings and other patient conditions. Results: Cuff pressure decreased by 4.9 ± 2.9 cmh2o from the target value: in 45% of all measurements, cuff pressure was less than 20 cmh2o. No correlations were found between the decrease in cuff pressure and body position, severity score, intubation period or ventilatory settings. Conclusions: In half of critically ill patients, even after frequent readjustment to 24 cmh2o, cuff pressures fell to less than 20 cmh2o. Key words: Cuff pressure, endotracheal tube, critically ill patients, mechanical ventilation. Page 2/ Motoyama A Background To prevent gas leakage and aspiration, an endotracheal tube (ETT) with a cuff is generally used for mechanically ventilated patients. Because excessive cuff pressure may decrease tracheal capillary perfusion, and insufficient cuff pressure may lead to hypoventilation by the air leakage and aspiration of oropharyngeal contents,1,2,3 cuff pressure should be maintained within the proper range (20 to 30 cmh2o). Cuff pressure is affected by several factors, including tracheal muscular tone, body temperature, and ETT position.3,4 In critically ill patients, however, the variations in cuff pressure have not been fully evaluated. Cuff pressure measurements may be routinely taken every 8 to 24 hours in many ICUs, and during the interval, air inside the cuff may escape from the ETT cuff surface or through the pilot balloon valve. It is possible that severe lung status and high airway pressure may enhance the leakage of cuff air. Because it remains unknown whether, through frequent adjustment, cuff pressure can be maintained within the target range, we conducted a study of critically ill patients to investigate the effects of frequent pressure adjustment. Page 3/ Motoyama A Methods In a prospective observational study, we collected cuff pressure measurements at an ICU in a university hospital from May to July in We serially enrolled adult patients who were receiving mechanical ventilation for longer than 48 hours with cuffed

3 ETTs. ETTs with a standard high-volume low-pressure cuff (Hi-Lo Mallinckrodt Medical, Ireland) were inserted orotracheally, and the same brand of ventilator circuit and heat-and-moisture exchanger were used. Pressure-controlled ventilation was applied in assist-control mode with pressure control, PEEP, and ventilatory rate determined by attending physicians. After training, nurses measured cuff pressure every 2 hours using a cuff inflator (Cuff Pressure Gauge, VBM Medizintechnik GmbH, Sulz am Neckar, Germany) each time readjusting the pressure to 24 cmh2o. They also recorded patient body position, along with ventilatory settings such as peak inspiratory pressure (PIP), mean airway pressure (MAP) and positive end-expiratory pressure (PEEP). In addition, the incidence of the newly developed pneumonia, and mortality during ICU stay were also assessed. The study was approved by the hospital research board, which waived the requirement for informed consent for this observational study that was part of routine care and did not pose additional risk to the patients. Statistical analysis Numerical data are shown as mean ± SD. We used chi-square testing to determine whether cuff pressure was related to body position, intubation duration, PIP, MAP, PEEP, or APACHE Page 4/ Motoyama A II scores. We used three categories for body position (supine, right lateral or left lateral decubitus), two for intubation period (< or 7days), for PIP (< or 24 cmh2o), for MAP (< or 12 cmh2o), for PEEP (< or 6 cmh2o) and for Acute Physiology and Chronic Health Evaluation (APACHE) II score (< or 20).5 When significant (P <0.05) was detected, we applied multivariate analysis to investigate the effects of the variables. Statistical analysis was performed using commercial statistical software (SPSS Inc., Chicago, IL). Page 5/ Motoyama A Results We collected 1,846 data points from 27 patients. Table 1 summarizes patent characteristics. Cuff pressure deviation from the target value (24 cmh2o) was 4.9 ± 2.9 cmh2o: cuff pressure was below 20 cmh2o in 45% of the measurements, below 24 cmh2o in 93% and over 30 cmh2o in 0.05% (Fig. 1). Distribution of cuff pressure

4 was not related to body position (P = 0.60), intubation period (P >0.99), PIP (P >0.99), MAP (P >0.99), PEEP (P >0.99), or APACHE II score (P = 0.85). No cases of mortality, or newly developed pneumonia were recorded. All patients discharged from the ICU after average intubation period of 6.4 days. Page 6/ Motoyama A Discussion Our study demonstrated that cuff pressure decreased and was below 20 cmh2o in about half of the measurements, taken from the enrolled critically ill patients. Although no complications from mechanical ventilation were apparent in this study, loss of cuff pressure is known to increase the risk of complications: cuff pressure below 20 cmh2o is associated with the development of ventilator-associated pneumonia.1,2,6,7 During invasive mechanical ventilation, maintenance of appropriate cuff pressure is an important part of patient care. Despite frequent regular adjustment, in 45% of the measurements from critically ill patients, we found that cuff pressure decreased to less than 20 cmh2o. Nseir et al3, measuring cuff pressure every 8 hours, found that cuff pressure was maintained within recommended range (20 to 30 cmh2o) in only 18% of patients, that it was lower than 20 cmh2o at least once for 54% of patients, and that it was over 30 cmh2o at least once for 73% of patients. Our findings suggest, even frequent adjustment, that it is not possible to reliably maintain cuff pressure with the appropriate range. In our study, cuff tended to deflate: probably owing to different patient characteristics than in Nseir s study, we found very few instances of pressure higher than 30 cmh2o. Cuff pressure is known to change in response to several factors.2,3,8,9,10,11 Godoy et al8 have reported that patient body positioning affects cuff pressure. If patients have severe damage to the tracheal wall, poor ETT-cuff conformation increases the risk of cuff leakage and pressure loss.2,3,9,10 Nseir et al3 found that extended periods of intubation were associated with decreased cuff pressure. We also had speculated that severe status shown as high APACHE score would be associated with deterioration of respiratory conditions and increase the risk of cuff leakage. Page 7/ Motoyama A Sole et al11 found tendencies for cuff pressure to increase with patients with higher Glasgow coma scale scores and with those in the head-up position. In our study,

5 however, we found no correlations between cuff pressure and body position, intubation period, ventilatory settings, or severity of condition. Other factors may contribute to the loss of cuff pressure. Because frequent readjustment did not prevent cuff pressure loss, we suspected that the measurement procedure itself might contribute to changes in cuff pressure. The air compressed in the cuff might escape to the measurement system during the connection procedure. In a preliminary bench study simulating an ETT (8.0-mm of internal diameter) in an artificial trachea, we continuously measured cuff pressure during the connection procedure. The cuff pressure decreased by 4.5 ± 1.5 cmh2o when a cuff inflator was connected to a pilot balloon. Although similar to the observed deviation (4.9 ± 2.9 cmh2o), further study is needed to clarify the effect of measurement procedures in a broader variety of situations. Our study has several limitations. First, the population was small and observation time varied depending on the ventilation requirements of individual patients. We also focused on changes in cuff pressure, not on the occurrence of micro-aspiration or clinically significant outcomes. Second, we did not evaluate the effect of body temperature on cuff pressure changes, or the effect of cuff pressure on clinical outcome. In conclusion, even after frequent adjustment to 24 cmh2o, cuff pressure decreased to less than 20 cmh2o in half of the measurements taken from critically ill patients. Page 8/ Motoyama A List of abbreviations: ICU, intensive care unit; ETT, endotracheal tube Competing interests: The authors declare that they have no competing interests. Authors contributions: AM, SA, HK, and YM established the design of the study, collected the data, and drafted the manuscript. TM participated in the design of the study and revised the manuscript. HI performed statistical analysis and revised the manuscript. MN revised the manuscript. All authors read and approved the final manuscript. Page 9/ Motoyama A Page 10/ Motoyama A Figure legends Fig. 1 Distribution of cuff pressure Reference Sengupta P, Sessler DI, Maglinger P, Wells S, Vogt A, Durrani J, Wadhwa A:

6 Endotracheal tube cuff pressure in three hospitals, and the volume required to produce an appropriate cuff pressure. BMC Anesthesiol 2004, 4: Boqué MC, Gualis B, Sandiumenge A, Rello J: Endotracheal tube intraluminal diameter narrowing after mechanical ventilation: use of acoustic reflectometry. Intensive Care Med 2004, 30: Sole ML, Penoyer DA, Su X, Jimenez E, Kalita SJ, Poalillo E,Byers JF, Bennett M, Ludy JE: Assessment of endotracheal cuff pressure by continuous monitoring: a pilot study. Am J Crit Care 2009, 18: Sole ML, Su X, Talbert S, Penoyer DA, Kalita S, Jimenez E, Ludy JE, Bennett M: Evaluation of an intervention to maintain endotracheal tube cuff pressure within therapeutic range. Am J Crit Care 2011, 20: Nseir S, Brisson H, Marquette CH, Chaud P, Di Pompeo C, Diarra M, Durocher A: Variations in endotracheal cuff pressure in intubated critically ill patients: prevalence and risk factors. Eur J Anaesthesiol 2009, 26: Vyas D, Inweregbu K, Pittard A: Measurement of tracheal tube cuff pressure in critical care. Anaesthesia 2002, 57: Knaus WA, Draper EA, Wagner DP, Zimmerman JE: APACHE II: a severity of disease classification system. Crit Care Med 1985, 13: Pneumatikos IA, Dragoumanis CK, Bouros DE: Ventilator-associated pneumonia or endotracheal tube-associated pneumonia? An approach to the pathogenesis and preventive strategies emphasizing the importance of endotracheal tube. Anesthesiology 2009, 110: Nseir S, Zerimech F, Fournier C, Lubret R, Ramon P, Durocher A, Balduyck M: Continuous control of tracheal cuff pressure and microaspiration of gastric contents in critically ill patients. Am J Respir Crit Care Med 2011, 184:

7 Godoy AC, Vieira RJ, Capitani EM: Endotracheal tube cuff pressure alteration after changes in position in patients under mechanical ventilation. J Bras Pneumol 2008, 34: Matic I, Titlic M, Dikanovic M, Jurjevic M, Jukic I, Tonkic A: Effects of APACHE II score on mechanical ventilation; prediction and outcome. Acta Anaesthesiol Belg 2007, 58: