Original Article
Preliminary study on a proposal of an interdisciplinary flowchart of tracheostomy decannulation Estudo preliminar sobre a proposta de um fluxograma de decanulação em traqueostomia com atuação interdisciplinar Telma de Almeida Busch Mendes1, Leny Vieira Cavalheiro2, Rosana Tiepo Arevalo3, Renata Sonegth4
ABSTRACT Objective: To evaluate the weaning steps of decanulation in patients admitted at the Semi-intensive Care Unit of the Hospital Israelita Albert Einstein, following a protocol proposed and developed by Physical Therapy and Phonoaudiology specialists, with a focus on interdisciplinary actions and also to analyze the values of ventilatory measurements, weaning complications and the relation between success and decanulation mean time. Methods: A weaning and decanulation flowchart was applied to a population of 21 tracheostomized patients with several diagnoses. All patients met the basic criteria for the weaning procedure. Maximum inspiratory pressure (MIP), maximum expiratory (MEP), vital capacity and peak cough flow data were analyzed. Results: In the population subject of this study, patients presented an average peak cough flow value of 174.74 l/min in the beginning of the weaning, standard deviation = 58.03, with a lower value of 80 and higher of 310 l/min. All patients who were decanulated presented MIP > -30cmH2O. In this preliminary study, the MEP and the MIP measure have not demonstrated to be an effective measure for the sake of data analysis as success predictors. Conclusions: This study revealed that the weaning and decanulation of tracheomatized patients is more efficient and safer when there is an interdisciplinary participation and that available data are still at a preliminary stage and they point out the need of further studies over a larger population. Keywords: Weaning; Tracheostomy
RESUMO Objetivo: Avaliar as etapas do desmame e decanulação dos pacientes traqueostomizados da Unidade Semi-intensiva do Hospital Israelita Albert Einstein, seguindo um protocolo proposto pela Fisioterapia
e desenvolvido em parceria com a equipe de Fonoaudiologia, com foco na ação interdisciplinar. Analisar os valores encontrados de medidas ventilatórias, as complicações do desmame e relacionálas ao sucesso e ao tempo médio para decanulação. Métodos: Foi aplicado um fluxograma de desmame e decanulação a uma população de 21 pacientes traqueostomizados com diversos diagnósticos. Todos os pacientes se encaixavam nos critérios básicos para desmame da traqueostomia. Foram analisados dados da pressão inspiratória máxima (PImax), pressão expiratória máxima (PEmax), capacidade vital e peak cough flow. Resultados: Em nossa população de estudo, os pacientes apresentaram, no início do desmame, um valor médio de peak cough flow de 174,74 l/min, desvio padrão = 58,03, com o menor valor de 80 l/min e o maior valor de 310 l/min. Todos os pacientes que decanularam apresentaram PImax > -30 cmH2O. Neste estudo preliminar, a medida de PEmax e PImax tiveram seus valores corrigidos pela fórmula e não se mostraram efetivas na análise dos dados como preditores de sucesso. Conclusões: Este estudo revelou que o processo de desmame e decanulação dos pacientes traqueostomizados se torna mais eficaz e seguro quando a participação é interdisciplinar; os dados do presente trabalho ainda são preliminares e apontam para a necessidade de novos estudos em uma população maior. Descritores: Desmame; Traqueostomia
INTRODUCTION Tracheostomy is a procedure used very frequently in general hospitals to treat respiratory insufficiency from many different causes. It is common for specific rules to be followed regarding the indications of a tracheostomy, but there are no decisive guidelines for the process of removing the tracheostomy, id est, rules
Study carried out at Departamento de Fisioterapia e Fonoaudiologia of Hospital Israelita Albert Einstein – HIAE, São Paulo (SP), Brazil. 1
Master’s degree, Physical therapist at Hospital Israelita Albert Einstein – HIAE, São Paulo (SP), Brazil.
2
Master’s degree, Physical therapist at Hospital Israelita Albert Einstein – HIAE, São Paulo (SP), Brazil.
3
Master’s degree, Speech therapist at Hospital Israelita Albert Einstein – HIAE, São Paulo (SP), Brazil.
4
Master’s degree, Speech therapist at Hospital Israelita Albert Einstein – HIAE, São Paulo (SP), Brazil.
Corresponding author: Telma de Almeida Busch Mendes – Rua Deputado João Sussumo Hirata, 770, apto. 12 – Morumbi – CEP 05715-010 – São Paulo (SP), Brasil – Tel.: 3742-7565 – e-mail:
[email protected] The authors declare there is no conflict of interest Received on Jun 19, 2006 – Accepted on Jan 15, 2008
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for tracheostomy weaning until its total removal. In most hospitals, physical therapists are responsible for the weaning and decannulation process. In the joint project carried out at the Semi-intensive Care Unit of the Hospital Israelita Albert Einstein (HIAE), it was possible to observe that interaction between physicians, nurses, physical therapists and speech therapists has allowed a reduction in time of use of tracheostomy, accelerating the weaning process and making it safer for patients, thus lowering the risk of non-success and complications. Evidence-based guidelines have confirmed the benefit of protocols for weaning patients from ventilators and the important participation of physical therapists in this process, but very little has been published on the importance of the multiprofessional team in tracheostomy weaning(1). Tracheostomy weaning is considered as the moment when the cuff starts to be deflated, followed by the plastic-to-metal exchange of the cannula (without the cuff), until the removal of the tracheostomy cannula and occlusive dressing of the stoma. The decision as to when to initiate weaning requires teamwork and an absence of factors that might predict failure. The reasons that lead to the indication of a tracheostomy must be considered before the weaning process is begun(2). For a successful weaning process, attention should be given to the need for sedation, mechanical ventilation time, acute or chronic respiratory insufficiency, presence of airway obstruction (due to edema, tumor or other causes), prior surgery on the head and neck, vocal fold paralysis and glottic or subglottic stenosis. All problems must be solved and the upper airway must be restored for an adequate flow of air. Other factors that predict success in decannulation include the patient’s clinical stability, absence of secretions in quantities that might compromise the breathing pattern, total weaning from ventilator and the ability to swallow in the absence of the cuff with no signs of bronchoaspiration. The patient must be able to breathe through upper airways (nasally) with the removal of the pressure of the cuff and occlusion of the tracheostomy, with no sign of obstruction or resistance. Expiratory flow must also be sufficient to generate strength, so that the patient can cough and speak(3). If the patient’s medical conditions allow, the physician authorizes the process of weaning from the ventilator. In the presence of any clinical sign of aspiration, such as frequent coughing with the cuff deflated suggesting the presence of saliva in the airway, change in pulse oximeter values and voice revealing the presence of secretion(4), the physical therapist should suggest to the primary physician an assessment of the patient by a speech therapist. This evaluation may be einstein. 2008; 6(1):1-6
made early on during the weaning process from the ventilator parameters. The speech therapist’s objective is that the patient be able to effectively swallow saliva, demonstrate swallowing and breathing coordination, and, if possible, begin to speak – which are aspects that may be altered by the presence of the tracheostomy or by the patient’s illness(3). The focus of Physical Therapy during this period is to decrease ventilator pressures, facilitating adaptation to the speaking valve. The muscle strength evaluation in patients undergoing the process of decannulation is also extremely important, considering that patients submitted to tracheostomies and prolonged mechanical ventilation lose strength and endurance for lack of use. All professionals involved must be attentive to the following warning signs of complications: residue of saliva or food in the trachea, change in coloring or aspect of secretions, fever, worsening of oxygenation, lowered level of consciousness and abrupt change in radiographic images(3).
OBJECTIVE The present study aimed to present a flowchart of interdisciplinary action in tracheostomy weaning and its applicability in a general hospital, besides reporting preliminary results. METHODS For this preliminary descriptive study, a flowchart was designed (Figure 1) to exemplify step by step decannulation with interdisciplinary participation. Data were collected by physical therapists in routine care of tracheostomized patients, demonstrating its applicability. All patients with tracheostomies in the Semiintensive Care Unit of HIAE, with prescriptions for Physical Therapy and who met protocol inclusion criteria during the period from April 2004 to December 2006, were included, regardless of their diagnoses, sex or age, totaling up 21 patients. Patients with no prognosis for weaning from tracheostomy, id est, who had a clinical criterion for maintenance of the artificial airway, were excluded. Also excluded were patients with a prognosis for decannulation whose data had been lost and who had difficulties in measurements. The steps for tracheostomy weaning were clarified for patients and their family members or responsible companion, as is routine for the Physical Therapy Service. Patients or the persons responsible for them signed the informed consent and commitment forms upon admittance, as is standard procedure. In this way, no other participation and consent forms were proposed, since
Preliminary study on a proposal of an interdisciplinary flowchart of tracheostomy decannulation
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Patient weaned from ventilator is assessed by physical therapist after medical order Physical therapist measures: cuff pressure, VC, MIP, MEP and peak cough flow
Physical therapist deflates the cuff: observes clinical signs of airway obstruction and aspiration Physical therapist suggests primary physician to assess airways (AA)
S
Does primary physician agree with AA?
3
N
S
1
N
Patient will not be decannulated
S N
N Is the patient on free oral diet?
Assessment of airways
2
Physical therapist suggests speech therapy assessment to primary physician
N Clinical sign – aspiration?
S 4
Obstructed airway?
Physical therapist performs interventions in agreement with the primary physician
Any parameter to decannulate?
S
3
Does the primary physician authorize continuity of weaning without AA?
S
Physical therapist keeps cuff deflated for 12 hours
S
N Clinical
S
Normal airway?
1
worsening?
Physical therapist suggests speech therapy assessment to primary physician for PO feeding with deflated cuff
N 4
N Does physician agree?
Patient will not be decannulated
2
S
Signs aspiration?
N
N
Physical therapist indicates to physician exchanging to smaller metal cannula (5 or 4) and reduction after 48 hours
S Speech therapy assessment
N
Is swallowing efficient to decannulate?
N
S
After 56 hours, the cannula is removed and the stoma occluded, with physician’s agreement
Patient will be decannulated
Speech therapy
Figure 1. Flowchart of tracheostomy decanulation in adults
the data used in this article were necessarily collected for patient’s treatment. Data were pooled here to exemplify the flowchart, sparing the patient unnecessary tests and precluding identification of the subjects. The flowchart was developed by the authors, members of the Physical Therapy and Speech Therapy teams of HIAE, based on their own clinical experience and incremented by data from specific scientific literature. The physical therapist initiates the decannulation process subject to authorization from the physician. The parameters used are MIP, MEP, peak cough flow, vital capacity (VC) and cuff pressure. Each step of this flow was analyzed for each patient, and the reasons for it not being followed in some cases were recorded.
For statistical studies, initially descriptive data analysis was performed. Qualitative variables are presented by absolute frequencies (n) and category percentages for each. Quantitative variables are presented as means, standard deviations (sd), medians, and minimum and maximum values. The analyses were carried out using Statistical Package for Social Sciences (SPSS) version 10.0 for Windows (1999)(5).
RESULTS All patients included in the sample followed the proposed flowchart. In all cases, weaning was initiated only after an assessment by a physical therapist and after all decannulation criteria had been met. Average
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time for decannulation was 20.94 ± 23.21 days, with a minimum of four days and a maximum of 87 days. Out of 21 patients, six were females (28.6%) and 15 were males (71.4%), with an average age of 62.43 ± 20.37 years (range 20 to 89 years). The main diagnoses and reasons for admittance were acute respiratory insufficiency (ARI, 19.0%), polytrauma (14.3%), and tumor resection (9.5%), as shown on Table 1. Table 1. Number and percentage of diagnoses and reasons for admittance of 21 tracheostomized patients to the Semi-intensive Care Unit of Hospital Israelita Albert Einstein Diagnosis at admission Myocardial infarction Laparotomy Abcess drainage Uncompensated heart failure Non Hodgkin lymphoma Pancreatitis Tumor resection Parcial laryngectomy Meningocele Acute respiratory failure Bronchopneumonia Hemorrhagic stroke Laparotomy Head trauma Retroperitonial linphadenopathy Polytrauma
n 1 1 1 1 1 1 2 1 1 4 2 1 1 1 1 3
% 4.8 4.8 4.8 4.8 4.8 4.8 9.5 4.8 4.8 19.0 9.5 4.8 4.8 4.8 4.8 14.3
The past event most frequently found was myocardial revascularization (MR) in 38.1%; cancer (CA) and respiratory insufficiency (RI) in 19.0%; and systemic arterial hypertension (SAH) in 14.3%, among others with the same percentage, as shown on Table 2. Table 2. Number and percentage of past events in 21 tracheostomized patients in the Semi-intensive Care Unit of Hospital Israelita Albert Einstein Previous history Head trauma Respiratory failure Acute respiratory failure Tracheomalacia Granuloma Heart failure Depression Arterial hypertension Diabetes Chronic obstructive pulmonary disease Larynx cancer Myocardial revascularization Coronary insufficiency Cancer Morbid obesity Dysphagia Hiydrocephalus Others
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n 1 1 4 1 1 2 2 3 2 1 1 8 1 4 1 2 1 3
% 4.8 4.8 19.0 4.8 4.8 9.5 9.5 14.3 9.5 4.8 4.8 38.1 4.8 19.0 4.8 9.5 4.8 14.3
Among 21 patients with tracheostomies, only three had not been previously intubated. The mean intubation time before tracheostomy was 7.95 ± 5.21 days. Of the 21 tracheostomies carried out, 12 (57.1%) were surgical and nine (42.9%) were percutaneous. The number of cannulas used were ten (4.8%), nine (9.5%) and eight (85.7%). The most frequently used cannula was Shiley®, in 20 cases (95.2%). Table 3 shows the values found for MIP, MEP, peak cough flow and VC among patients, with descriptive and normal values. Table 3. Descriptive values of maximum inspiratory pressure, maximum expiratory pressure, peak cough flow and vital capacity of 21 tracheostomized patients at the Semi-intensive Care Unit of Hospital Israelita Albert Einstein Values Cuff pressure Vital capacity MIP Predicted value MIP* LLN MIP* MEP Predicted value MEP* LLN MEP* Peak cough flow (l/min)
Mean 26.52 382.19 -59.10 97.89 74.07 81.67 103.15 79.63 174.74
Median 26.00 120.0 -60.00 97.76 76.72 72.00 103.30 81.40 180.00
sd 4.76 427.00 -21.72 15.15 13.51 42.31 17.10 15.16 58.03
Minimum Maximum 15 38 30 1500 -120 -30 69.34 140.66 52.32 113.28 24 150 63.62 146.67 45.26 121.09 80 310
Key: * values corrected by formula per gender; sd = standard deviation; MIP = maximum inspiratory pressure; MEP = maximum expiratory pressure; LLN = lower limit of normal
Most (17) patients were decannulated (81.0%). There were no deaths among these patients. Table 4 shows patients with successful and unsuccessful decannulation procedures relative to normal MIP values. Table 4. Number and percentage of patients with normal values and values below the lower limit of normal of maximum inspiratory pressure and success in decannulation in 21 tracheostomized patients at the Semi-intensive Care Unit of Hospital Israelita Albert Einstein Success in decannulation Yes No Total
Maximum inspiratory pressure normality Normal value 5 (29.4%) 5 (23.8%)
Below LLN 12 (70.6%) 4 (100%) 16 (76.2%)
Total 17 (100.0%) 4 (100.0%) 21 (100.0%)
LLN = lower limit of normal
Table 5 shows the patients with successful and unsuccessful decannulation procedures relative to normal MEP values. Table 5. Number and percentage of patients with normal values and values below the lower limit of normal of maximum expiratory pressure and success in decannulation in 21 tracheostomized patients at the Semi-intensive Care Unit of Hospital Israelita Albert Einstein Success in decannulation Yes No Total LLN = lower limit of normal
Maximum expiratory pressure normality Normal value 7 (41.2%) 1 (25%) 8 (38.1%)
Below LLN 10 (58.8%) 3 (75%) 13 (61.9%)
Total 17 (100.0%) 4 (100.0%) 21 (100.0%)
Preliminary study on a proposal of an interdisciplinary flowchart of tracheostomy decannulation
Nine patients (42.9%) experienced complications during weaning: there were four cases of dysphagia; two cases of worsening clinical status with progression to total dependency on mechanical ventilation; and three cases of delayed weaning and decannulation (one because of the need for surgery, another because of the presence of facial edema and a third because of the lowered level of consciousness and surgery). Of the four patients who experienced dysphagia, two were successfully decannulated and two were not.
DISCUSSION The sample was chosen randomly as to sex, age and primary diagnosis, considering the presence of a tracheostomy as the inclusion factor. Of all patients analyzed in this study, few were not decannulated, and a minority had not been previously intubated. The mean intubation time before tracheostomy proved to be in concurrence with findings reported in literature(6-7). Several factors can hinder decannulation. Studies described in medical literature confirm that the respiratory muscles of patients submitted to prolonged mechanical ventilation lose strength and endurance for lack of use. Those who depend on mechanical ventilation show a greater predisposition towards respiratory muscle fatigue, a greater tendency towards an abnormal respiratory pattern and are more susceptible to respiratory insufficiency, which can hinder their weaning from mechanical ventilation(8-9). Consequently, this may hinder or even impede the decannulation process. Promptness in returning to spontaneous ventilation, when muscle deficiency is the main cause of insufficiency, and training comprise the best guidelines for treatment(10-11). Researchers agree that the lowest MIP value for maintaining spontaneous ventilation is -25 cm H2O(12). In this study, all patients had normal MIP values as per Hejidra(12), but normal values were considered according to Neder(13). In this study, few patients had trouble in the decannulation process with a prolonged decannulation time, whether due to difficulties in achieving total weaning from the ventilator or related to dysphagia, but the difficulties were resolved with intervention of the speech therapist. Half of the patients had trouble during weaning. Of these, some cases were due to dysphagia and others to a worsening of their clinical status leading to total dependency on mechanical ventilation. The presence of severe dysphagia and difficulty in weaning from mechanical ventilation are conditions that may not be favorable and preclude decannulation. The intention of this protocol is to identify these difficulties and propose early intervention.
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Oropharyngeal dysphagia may be a complicating factor in weaning from a tracheostomy. At HIAE, the recommendation is that the patient with signs of altered swallowing be submitted to an assessment by a speech therapist after medical prescription, as well as an evaluation of airways. Identification of a clinical sign suggestive of aspiration not only expedites intervention by a speech therapist, but also allows the assessment of airways, excluding any factor that may hinder or impede weaning (stenosis, granuloma, tracheomalacia and significant dysphagia). In the present sample, of those patients who experienced dysphagia, half were able to decannulate after the participation of the speech therapist. Among those who were not decannulated, in one case a video swallow test showed the presence of severe dysphagia, and in another case, the patient was discharged with the tracheostomy and was to receive home-based speech therapy care. In this study, some patients were allowed their oral diets with the cuff still inflated, with no accompaniment by a speech therapist. This protocol gives the physician freedom to make clinical decisions as to ordering specific assessments or not, which are always carried out with teamwork, clinical evaluations and discussion. According to Hejidra(12), MIP is related to success of ventilator weaning. In this study, no direct correlation was found between normal measurements of MIP, MEP and success in decannulation. Nevertheless, in cases of decannulation failure, the values found were below the normal limits(13). There are no reports in literature on the predictive value for successful decannulation, except for patients with neuromuscular disease. The study performed by Bach and Saporito among patients with neuromuscular diseases identified the peak cough flow > 160 l/ min as a success predictor in decannulation(14). The measurement of the peak cough flow in this study could not be considered a predictive factor for decannulation success, possibly because of the heterogeneous aspect of the sample. Several authors(15-19) recommend monitoring the cuff pressure regularly with the use of a manometer. This verification is necessary because of the risk of tracheal complications that can interfere in the process of weaning from the tracheostomy. Lomholt(16) and Bernhard et al.(19) recommend 25 cmH2O cuff pressure as the minimum value necessary to prevent aspiration around the cuff and diminish the risk of nosocomial acquired pneumonia. In clinical practice, cuff measurements are often in disagreement with the values recommended in literature. In this study, the pressures identified were between 20 and 30 cmH2O in most of the subjects, and none was more than 40 cmH2O. In the study conducted by Sengupta et al.(15), einstein. 2008; 6(1):1-6
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in merely 27% of sample the cuff pressure was between 20 and 30 cmH2O and, in 27%, the pressure exceeded 40 cmH2O. The sample of the present study showed that a little more than half of the cuff pressure measurements were over 25 cmH2O and approximately one third were below what is recommended (< 25 cmH2O). Several abnormalities may occur because of excessive cuff pressure – among them, tracheomalacia. Despite having been seen in only one case, the cause cannot be safely stated, since there are several factors related. The patient may have had tracheomalacia before tracheostomy was done and no prior study (bronchoscopy) had been performed for analysis. Intubation time was at the limit of what is recommended, but without the prior assessment, this complication cannot be correlated with the cuff pressure, especially since the cuff pressure is routinely checked at the HIAE – id est, daily, two times each period.
CONCLUSIONS There was no direct correlation between the measurements observed and decannulation. It is possible to establish, however, that normal respiratory parameters associated with the participation of a multiprofissional team increase the chances of quicker decannulation, free of complications and safer for patients. Based on the aspects discussed, we suggest that a flowchart with interdisciplinary participation can make the process of weaning and decannulation safer, minimizing the risk of complications and saving time, material, and specialized or skilled labor. Further studies with larger samples are necessary in order to define the peak cough flow cutoff point as a success predictor for decannulation in the population studied. References 1. Lewis RJ. Tracheostomies. Indications, timing, and complications. Clin Chest Med. 1992;1(13):137-49. 2. Godwing JE, Heffner JE. Special critical care considerations in tracheostomy management. Clin Chest Med. 1991;12(3):573-83. 3. Pannunzio TG. Aspiration of oral feedings in patients with tracheostomies. AACN Clinical Issues. 1996;7(4):560-9.
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4. Shapiro J, Downey L. The evaluation and management of swallowing disorders in the elderly. Geriatric Times. 2003 [cited 2006 Out 22]; 4(6):[about 11 p.] Available http://www.cmellc.com/geriatrictimes/g031217.html 5. The SPSS Statistical package for the social sciences: base users guide [computer program]. Version 10.0. Chicago: SPSS; 1999. 6. Griffiths J, Barber VS, Morgan L, Young JD. Systematic review and metaanalysis of studies of the timing of tracheostomy in adult patients undergoing artificial ventilation. BMJ. 2005;330(7502):1243. 7. Rumbak MJ, Newton M, Truncale T, Schwartz SW, Adams JW, Hazard PB. A prospective, randomized, study comparing early percutaneous dilational tracheotomy to prolonged translaryngeal intubation (delayed tracheotomy) in critically ill medical patients.Crit Care Med.;32(8):1689-94. Erratum in: Crit Care Med. 2004 Dec;32(12):2566. 8. Le Bourdelles G, Viires N, Boczkowski J, Seta N, Pavlovic D, Aubier M. Effects of mechanical ventilation on diaphragmatic contractile properties in rats. Am J Respir Crit Care Med. 1994;149(6):1539-44. 9. Tobin MJ, Alex CG. Discontinuation of mechanical ventilation. In: Tobin MJ. Principles and practice of mechanical ventilation. New York: McGraw-Hill; 1994. p. 1177-206. 10. Hulzebos EH, Helders PJ, Favié NJ, De Bie RA, Brutel de la Riviere A, van Meeteren NL. Preoperative intensive inspiratory muscle training to prevent postoperative pulmonary complications in high-risk patients undergoing CABG surgery: a randomized clinical trial. JAMA. 2006;296(15):1851-7. 11. Enright SJ, Unnithan VB, Heward C, Withnall L, Davies DH. Effect of high-intensity inspiratory muscle training on lung volumes, diaphragm thickness, and exercise capacity in subjects who are healthy. Phys Ther. 2006;86(3):345-54. 12. Heijdra YF, Pinto-Plata V, Frants R, Rassulo J, Kenney L, Celli BR. Muscle strength and exercise kinetics in COPD patients with a normal fat-free mass index are comparable to control subjects. Chest. 2003 Jul;124(1):75-82. 13. Neder JA, Andreoni S, Lerario MC, Nery L. Reference values for lung function tests. II. Maximal respiratory pressures and voluntary ventilation. Bras J Med Biol Res. 1999;32(6):719-27. 14. Bach JR, Saporito LR. Criteria for extubation and tracheostomy tube removal for patients with ventilatory failure. A different approach to weaning. Chest. 1996;110(6):1566-71. 15. Sengupta P, Sessler DI, Maglinger P, Wells S, Vogt A, Durrani J, et al. Endotracheal tube cuff pressure in three hospitals, and the volume required to produce an appropriate cuff pressure. BMC Anesthesiol. 2004;4(1):8. 16. Lomholt N. A device for measuring the lateral wall cuff pressure of endotracheal tubes. Acta Anaesthesiol Scand. 1992;36(8):775-8. 17. Seegobin RD, van Hasselt GL. Endotracheal cuff pressure and tracheal mucosal blood flow: endoscopic study of effects of four large volume cuffs. Br Med J (Clin Res Ed). 1984;288(6422):965-8. 18. Sanada Y, Kojima Y, Fonkalsrud EW. Injury of cilia induced by tracheal tube cuffs. Surg Gynecol Obstet. 1982;154(5):648-52. 19. Bernhard WN, Yost L, Joynes D, Cothalis S, Turndorf H. Intracuff pressures in endotracheal and tracheostomy tubes. Related cuff physical characteristics. Chest. 1985;87(6):720-5.
