AARC Clinical Practice Guideline
Removal of the Endotracheal Tube
RET 1.0 PROCEDURE
Removal of the endotracheal tube from adult, pediatric, and newborn patients.
RET 2.0 DESCRIPTION/DEFINITION:
To ensure patient safety, the patient with a temporary, artificial translaryngeal airway should have the device removed at the earliest appropriate time. Occasionally, acute airway obstruction of the artificial airway due to mucus or mechanical deformation mandates immediate removal of the artificial airway. (This guideline pertains to the decision processes surrounding the removal of an artificial translaryngeal airway, and the procedure referred to as extubation.)
- 2.1 Prolonged translaryngeal intubation is associated with many complications including but not limited to sinusitis,(1,2) vocal cord injury,(3) laryngeal injury,(4,5) laryngeal stenosis,(4,5) tracheal injury,(6-8) hemoptysis,(9) and pulmonary infection.(10-12)
- 2.2 Extubation may result in upper airway obstruction from laryngospasm,(13-15) laryngeal edema,(16-19) or supraglottic obstruction;(20) pulmonary edema;(21-23) pulmonary aspiration syndrome;(24,25) or impaired respiratory gas exchange.
RET 3.0 SETTINGS:
The endotracheal tube should be removed in an environment in which the patient can be physiologically monitored and in which emergency equipment and appropriately trained health care providers with airway management skills are immediately available.
RET 4.0 INDICATIONS/OBJECTIVES:
When the airway control afforded by the endotracheal tube is deemed to be no longer necessary for the continued care of the patient, the tube should be removed. In general, the patient should be capable of maintaining a patent airway and adequate spontaneous ventilation and should not require high levels of positive airway pressure to maintain normal arterial blood oxygenation.
- 4.1 Patients in whom further medical care is considered (and explicitly declared) futile may have the endotracheal tube removed despite continuing indications for the artificial airway.
- 4.2 Acute artificial airway obstruction mandates immediate endotracheal tube removal if the obstruction cannot be cleared rapidly. Reintubation or other appropriate techniques for reestablishing the airway must be used to maintain effective gas exchange (ie, surgical airway management).
RET 5.0 CONTRAINDICATIONS:
There are no absolute contraindications to extubation; however, some patients will require reintubation, positive pressure ventilation, continuous positive airway pressure, noninvasive ventilation, or high inspired oxygen fraction to maintain acceptable gas exchange after extubation. Airway protective reflexes are usually depressed immediately following and for some time after extubation and, therefore, measures to prevent aspiration should be considered.
RET 6.0 HAZARDS/COMPLICATIONS:
- 6.1 Hypoxemia after extubation may result from but is not limited to
- 6.1.1 failure to deliver adequate inspired oxygen fraction through the natural upper airway;
- 6.1.2 acute upper airway obstruction;
- 6.1.3 development of postobstruction pulmonary edema;
- 6.1.4 bronchospasm;
- 6.1.5 development of atelectasis, or lung collapse;
- 6.1.6 pulmonary aspiration;
- 6.1.7 hypoventilation
- 6.2 Hypercapnia after extubation may be caused by but is not limited to:
- 6.2.1 upper airway obstruction resulting from edema of the trachea, vocal cords, or larynx;
- 6.2.2 respiratory muscle weakness;
- 6.2.3 excessive work of breathing;
- 6.2.4 bronchospasm.
- 6.3 Death may occur when medical futility is the reason for removing the endotracheal tube.
RET 7.0 LIMITATIONS OF METHODOLOGY/VALIDATION OF RESULTS
Patients may need reintubation immediately or after some interval due to inappropriate extubation, progression of underlying disease, or development of a new disorder. A trial of extubation may be used in some marginal patients with the expectation that the need for reintubation is likely.
The need to reinsert an artificial airway following extubation is not necessarily an indication of poor practice. Inadequate airway maintenance and failure of reintubation may be an indication of poor practice.
The failure and complication rates of extubation can be used as quality monitors.
RET 8.0 ASSESSMENT OF NEED
The endotracheal tube should be removed as soon as the patient no longer needs an artificial airway. Patients should be capable of adequate spontaneous ventilation and should not require high levels of positive airway pressure or inspired oxygen to maintain adequate arterial blood oxygenation. (Experience suggests PEEP <=;10 cm H2O and FIO2 <=; 0.40.)
- 8.1 Patients receiving an artificial airway to facilitate treatment of respiratory failure should be considered for extubation when they have met traditional weaning criteria.(26) Examples of weaning criteria include but are not limited to
- 8.1.1 the capacity to maintain adequate arterial partial pressure of oxygen on inspired oxygen fractions provided with simple oxygen devices and with low levels of positive airway pressure;
- 8.1.2 the capacity to maintain appropriate pH and arterial partial pressure of carbon dioxide during spontaneous ventilation;(27,28)
- 8.1.3 adequate respiratory muscle strength;
- 8.1.4 maximum negative inspiratory pressure > 30 cm H2O;(29-33)
- 8.1.5 vital capacity greater than 10 mL/kg ideal body weight;(34)
- 8.1.6 pressure measured across the diaphragm during spontaneous ventilation less than 15% of maximum;
- 8.1.7 spontaneous exhaled minute ventilation < 10 L/min.(29)
- 8.1.8 in adults, respiratory rate < 35 during spontaneous breathing;(35) in infants and children, acceptable rate decreases with age and can be predicted and measured with good repeatability when determined by stethoscope.(36)
- 8.1.9 in adults, a rapid shallow breathing index (RSB, respiratory rate-to-tidal-volume ratio) of <=; 98-130;(37-40) in infants and children, neither a modified CROP index (derived from compliance, resistance, oxygenation, and ventilating pressure) nor a modified RSB has been shown to be a superior discriminator between successful and unsuccessful extubation.(41,42))
- 8.1.10 thoracic compliance > 25 mL/cm H2O;(43)
- 8.1.11 work of breathing < 0.8 J/L;(38,39,44-46)
- 8.1.12 oxygen cost of breathing < 15% total;(47-49)
- 8.1.13 dead-space-to-tidal-volume ratio < 0.6;(50)
- 8.1.14 absolute tracheal pressure in the first 0.1 second of occlusion < 6 cm H2O;(51,52) (This measurement is primarily a research tool.)
- 8.1.15 maximum voluntary ventilation > twice resting minute ventilation.(29)
- 8.2 In addition to treatment of respiratory failure, artificial airways are sometimes placed for airway protection. Resolution of the need for airway protection may be assessed by but is not limited to
- 8.2.1 normal consciousness,(53)
- 8.2.2 adequate airway protective reflexes,(54)
- 8.2.3 easily managed secretions.
- 8.3 In addition to resolution of the processes requiring the insertion of an artificial airway, issues that should be considered in all patients prior to extubation are
- 8.3.1 no immediate need for reintubation anticipated;
- 8.3.2 no previously identified difficulties with intubation;(55-58)
- 8.3.3 presence of gas leak around the deflated cuff with positive pressure breaths;(59,60)
- 8.3.4 evidence of stable, adequate hemodynamic function;(61-64)
- 8.3.5 evidence of stable nonrespiratory functions;(65-67)
- 8.3.6 electrolyte values within normal range.(68,69)
RET 9.0 ASSESSMENT OF OUTCOME
Removal of the endotracheal tube should be followed by adequate spontaneous ventilation through the natural airway, adequate oxygenation, and no need for re-intubation.
- 9.1 Clinical outcome may be assessed by physical examination, auscultation, invasive and noninvasive measurements of arterial blood gas values, and chest radiography.
- 9.2 Quality of the procedure can be systematically assessed by monitoring extubation complications and the need for reintubation.
RET 10. RESOURCES
- 10.1 Equipment:
- 10.1.1 Oxygen source
- 10.1.2 Devices to deliver oxygen-enriched gas mixtures
- 10.1.3 High-volume suction source
- 10.1.4 Pharyngeal and tracheal suction catheters
- 10.1.5 Self-inflating or non-self-inflating manual ventilation system
- 10.1.6 Oral and pharyngeal airways
- 10.1.7 Endotracheal tubes of various sizes
- 10.1.8 Translaryngeal intubation equipment (laryngoscope blades, handles, batteries, stylettes)
- 10.1.9 Equipment for establishing an emergency surgical airway (scalpel, lidocaine with epinephrine, appropriately sized endotracheal or tracheostomy tubes)
- 10.1.10 Pulse oximeter
- 10.1.11 Supplies for arterial puncture and blood gas analysis.
- 10.2 Personnel
- 10.2.1 Level-II personnel, credentialed and/or licensed health care personnel with documented knowledge and demonstrated skills specific to patient assessment and airway management, should determine the appropriateness of extubation, be available to assess success, and begin appropriate interventions should immediate complications occur. Personnel skilled in endotracheal intubation and the insertion of invasive airways should be immediately available whenever extubation is performed.
- 10.2.2 Level-I personnel, credentialed and/or licensed health care personnel with documented knowledge and demonstrated skill in providing oxygen administration devices and suctioning the airway, may provide support to Level-II personnel during the extubation procedure.
- 10.2.3 In the event of acute obstruction of the artificial airway, anyone with airway maintenance skills may remove the endotracheal tube to save the patient's life.(70)
RET 11.0 MONITORING
The success of removal of the endotracheal tube can be monitored by examining the frequency of reintubation and frequency of complications. When a patient experiences an unplanned self-extubation and does not require reintubation, this suggests that planned extubation should have been considered sooner.(71-76)
RET 12.0 FREQUENCY
The timing of extubation is determined by improvement in the patient's condition that mandated an artificial airway. Acute, artificial airway obstruction may occur at any time and must be recognized and treated immediately.
RET 13.0 INFECTION CONTROL
Caregivers should exercise Standard Precautions for all patients, follow CDC recommendations for control of exposure to tuberculosis and droplet nuclei,(77,78) and, in addition, institute appropriate precautions empirically for airborne, droplet, and contact agents pending confirmation of diagnosis in patients suspected of having serious infections.(77)
Endotracheal Tube Removal Working Group
Charles G Durbin Jr MD, Chairman Charlottesville VA
Robert S Campbell RRT, Cincinnatti OH
Richard D Branson RRT, Cincinnati OH
- Holzapfel L, Chevret S, Madinier G, Ohen F, Demingeon G, Coupry A, Chaudet M. Influence of long-term, oro- or nasotracheal intubation on nosocomial maxillary sinusitis and pneumonia: results of a prospective, randomized, clinical trial. Crit Care Med 1993;21(8):1132-1138.
- Guerin JM, Lustman C, Meyer P, Barbotin-Larrieau F. Nosocomial sinusitis in pediatric intensive care patients (letter). Crit Care Med 1990;18(8):902.
- Kastanos N, Estopa-Miro R, Marin-Perez A, Xaubet-Mir A, Augusti-Vidal A. Laryngotracheal injury due to endotracheal intubation: incidence, evolution, and predisposing factors¬a prospective, long-term study. Crit Care Med 1983;11(5):362-367.
- Colice GL, Strukel TA, Dain B. Laryngeal complications of prolonged intubation. Chest 1989;96(4):877-884.
- Santos PM, Afrassiabi A, Weymuller EA Jr. Risk factors associated with prolonged intubation and laryngeal injury. Otolaryngol Head Neck Surg 1994;111(4):453-459.
- Stauffer JL, Olson DE, Petty TL. Complications and consequences of endotracheal intubation and tracheotomy: a prospective study of 150 critically ill adult patients. Am J Med 1981;70:65-76.
- Hoeve LJ, Eskici O, Verwoerd CD. Therapeutic reintubation for post-intubation laryngotracheal injury in preterm infants. Int J Pediatr Otorhino 1995;31(1):7-13.
- Stauffer JL, Silvestri RE. Complications of endotracheal intubation, tracheostomy, and artificial airways. Respir Care 1982;27:417-434.
- Keceligil HT, Erk MK, Kolbakir F, Yildrim A, Yilman M, Unal R. Tracheoinnominate artery fistula following tracheostomy. Cardiovasc Surg 1995;3(5):509-510.
- Garibaldi RA, Britt MR, Coleman ML, Reading JC, Pace NL. Risk factors for postoperative pneumonia. Am J Med 1981;70(3):677-680.
- Kerver AJ, Rommes JH, Mevissen-Verhage EA, Hulstaert PF, Vos A, Verhoef J, Wittebol P. Prevention of colonization and infection in critically ill patients: a prospective, randomized study. Crit Care Med 1988;16(11):99-102.
- Torres A, Aznar R, Gatell JM, Jiminez P, Gonzalez J, Ferrer A, et al. Incidence, risk, and prognosis factors of nosocomial pneumonia in mechanically ventilated patients. Am Rev Respir Dis 1990;142(3):523-528.
- Backus WW, Ward RR, Vitkun SA, Fitzgerald D, Askanazi J. Postextubation laryngeal spasm in an unanesthetized patient with Parkinson's disease. J Clin Anesth 1991;3(4):314-316.
- Guffin TN, Har-el G, Sanders A, Lucente FE, Nash M. Acute postobstructive pulmonary edema. Otolaryngol Head Neck Surg 1995;112(2):235-237.
- Wilson GW, Bircher NG. Acute pulmonary edema developing after laryngospasm: report of a case. J Oral Maxillofac Surg 1995;53(2):211-214.
- Hartley M, Vaughan RS. Problems associated with tracheal extubation. Br J Anaesth 1993;71(4):561-568.
- Darmon JY, Rauss A, Dreyfuss D, Bleichner G, Elkharrat D, Schlemmer B, et al. Evaluation of risk factors for laryngeal edema after tracheal extubation in adults and its prevention by dexamethasone: a placebo-controlled, double-blind, multicenter study. Anesthesiology 1992;77(2):245-251.
- Nutman J, Brooks LJ, Deakins KM, Baldesare KK, Witte MK, Reed MD. Racemic versus l-epinephrine aerosol in the treatment of postextubation laryngeal edema: results from a prospective, randomized, double-blind study. Crit Care Med 1994 22(10):1591-1594.
- Kemper KJ, Benson MS, Bishop MJ. Predictors of postextubation stridor in pediatric trauma patients. Crit Care Med 1991;19(3);352-355.
- Vauthy PA, Reddy R. Acute upper airway obstruction in infants and children: evaluation by the fiberoptic bronchoscope. Ann Otol Rhinol Laryngol 1980;89(5, Pt 1):417-418.
- Willms D, Shure D. Pulmonary edema due to upper airway obstruction in adults. Chest 1988;94(5):1090-1092.
- Kamal RS, Agha S. Acute pulmonary oedema: a complication of upper airway obstruction. Anaesthesia 1984;39(5):464-467.
- Guinard JP. Laryngospasm-induced pulmonary edema. Int J Pediatr Otorhinolaryngol 1990;20(2):163-168.
- Goitein KJ, Rein AJ, Gornstein A. Incidence of aspiration in endotracheally intubated infants and children. Crit Care Med 1984;12(1):19-21.
- Arandia HY, Grogono AW. Comparison of the incidence of combined "risk factors" for gastric acid aspiration: influence of two anesthetic techniques. Anesth Analg 1980;59(11):862-864.
- Ely EW, Baker AM, Dunagan DP, Burke HL, Smith AC, Kelly PT, et al. Effect on the duration of mechanical ventilation of identifying patients capable of breathing spontaneously, N Engl J Med 1996;335(25):1864-1869.
- Berman LS, Fox WW, Raphaely RC, Downes JJ Jr. Optimum levels of CPAP for tracheal extubation of newborn infants J Pediatr 1976; 89(1):109-112.
- Kim EH, Boutwell WC. Successful direct extubation of very low birth weight infants from low intermittent mandatory ventilation rate. Pediatrics 1987;80(3):409-414.
- Sahn SA, Lakshminarayan S. Bedside criteria for discontinuation of mechanical ventilation. Chest 1973; 63(6):1002-1005.
- Hess D. Measurement of maximal inspiratory pressure: a call for standardization. Respir Care 1989;34:857-559.
- Marini JJ, Smith TC, Lamb V. Estimation of inspiratory muscle strength in mechanically ventilated patients: the measurement of maximal inspiratory pressure. J Crit Care 1986;1(1):32-38.
- Branson RD, Hurst JM, Davis K Jr, Campbell R: Measurement of maximal inspiratory pressure: a comparison of three methods. Respir Care 1989;34:789-794.
- Kacmarek RM, Cycyk-Chapman MC, Young-Palazzo PJ, Romangnoli DM. Determination of maximal inspiratory pressure: a clinical study and literature review. Respir Care 1989;34:868-878.
- Bendixen HH, Egbert LD, Hedly-White J, et. al.: Management of patients undergoing prolonged artificial ventilation. Respir Care 1965;10:149-153.
- Cohen CA, Zagelbaum G, Gross D, Roussos C, Macklem PT. Clinical manifestations of inspiratory muscle fatigue. Am J Med 1982;73(3):308-316.
- Rusconi F, Castagneto M, Gagliardi L, Leo G, Pellegatta A, Porta N, Razon S. Reference values for respiratory rate in the first 3 years of life. Pediatrics 1994(3):350-355.
- Yang KL, Tobin MJ. A prospective study of indexes predicting the outcome of trials of weaning from mechanical ventilation. N Engl J Med 1991;324(21):1445-1450.
- Lee KH, Hui LP, Chan TB, Tan WC, Lim TK. Rapid shallow breathing (frequency-tidal volume ratio) did not predict extubation outcome. Chest 1994;105(2).540-543.
- Krieger BP, Isber J, Breitenbucher A, Throop G, Ershowsky P. Serial measurements of the rapid-shallow-breathing index as a predictor of weaning in outcome in elderly medical patients. Chest 1997;112(4):1029-1034.
- Vassilakopoulos T, Zakynthinos S, Roussos C. The tension-time index and the frequency/tidal volume ratio are the major pathophysiologic determinants of weaning failure and success. Am J Respir Crit Care Med 1998;158(2):378-385.
- Baumeister BL, el-Khatib M, Smith PG, Blumer JL. Evaluation of predictors of weaning from mechanical ventilation in pediatric patients. Pediatr Pulmonol 1997;24(5):344-352.
- Khan N, Brown A, Venkataraman ST. Precitors of extubation success and failure in mechanically ventilated infants and children. Crit Care Med 1996;24(9):1568-1579.
- Peters RM, Hilberman M, Hogan JS, Crawford DA: Objective indications for respiratory therapy in post-trauma and postoperative patients. Am J Surg 1972; 124(2):262-269.
- Lewis WD, Chhwals W. Benotti PN Lakshman K, O'Donnell C, Blackburn GL, Bistrian BR. Bedside assessment of the work of breathing. Crit Care Med 1988;16(2):117-122.
- Levy MM, Miyasaki A, Langston D. Work of breathing as a weaning parameter in mechanically ventilated patients. Chest 1995;108(4):1018-1020.
- Kirton OC, DeHaven B, Morgan JP, Windsor J, Civetta JM. Elevated imposed work of breathing masquerading as ventilator weaning intolerance. Chest 1995;108(4):1021-1025.
- Shikora SA, Bistrian OR, Borlase BC, Blackburn GL, Stone MD, Benotti PN. Work of breathing: reliable predictor of weaning and extubation. Crit Care Med 1990;18(2):157-162.
- Harpin RP, Baker JP, Downer JP, Whitwell J, Gallacher WN. Correlation of the oxygen cost of breathing and length of weaning from mechanical ventilation. Crit Care Med 1987;15(9):807-812.
- Shikora SA, Benotti PN, Johannigman JA. The oxygen cost of breathing may predict weaning from mechanical ventilation better than the respiratory rate to tidal volume ratio. Arch Surg 1994;129(3):269-274.
- Tahvanainen J, Salmenpera M, Nikki P. Extubation criteria after weaning from intermittent mandatory ventilation and continuous positive airway pressure. Crit Care Med 1983;11(9):702-707.
- Montgomery AB, Holle RH, Neagley SR, Pierson DJ, Schoene RB. Prediction of successful ventilator weaning using airway occlusion pressure and hypercapnic challenge. Chest 1987;91(4):496-499.
- Gandia F, Blanco J. Evaluation of indexes predicting the outcome of ventilator weaning and value of adding supplemental inspiratory load. Intensive Care Medicine 1992;18(6):327-333.
- Redmond JM, Greene PS, Goldsborough MA, Cameron DE, Stuart RS, Sussman MS, et al. Neurologic injury in cardiac surgical patients with a history of stroke. Ann Thorac Surg 1996;61(1):42-47.
- Pavlin KG, Holle RH, Schoene RB. Recovery of airway protection compared with ventilation in humans after paralysis with curare. Anesthesiology 1989;70(3):381-385.
- Deem S, Bishop MJ. Evaluation and management of the difficult airway. Crit Care Clin 1995;11(1):1-27.
- American Society of Anesthesiologists. Practice guidelines for management of the difficult airway: a report by the American Society of Anesthesiologists Task Force on Management of the Difficult Airway. Anesthesiology 1993;78(3):597-602.
- Cork R. Monk JE. Management of a suspected and unsuspected difficult laryngoscopy with the laryngeal mask airway. J Clin Anesth 1992;4(3):230-234.
- Van Boven MJ, Lengele B, Fraselle B, Butera G, Veyckemans F. Unexpected difficult tracheal reintubation after thyroglossal duct surgery: functional imbalance aggravated by the presence of a hematoma. Anesth Analg 1998;82(2):423-425.
- Fisher MM, Raper RF. The 'cuff-leak' test for extubation. Anaesthesia 1992;47(1):10-12.
- Potgieter PD, Hammond JM. "Cuff" test for safe extubation following laryngeal edema. Crit Care Med 1988;16(8):818.
- Morganroth ML, Morganroth JL, Nett LM, Petty TL. Criteria for weaning from prolonged mechanical ventilation. Arch Intern Med 1984;144(5):1012-1016.
- Clochesy JM, Daly BJ, Montenegro HO. Weaning chronically critically ill adults from mechanical ventilatory support: a descriptive study. Am J Crit Care 1995;4(2):93-99.
- Biery DR, Marks JD, Schapera A, Autry M, Schlobohm RM, Katz JA. Factors affecting perioperative pulmonary function in acute respiratory failure. Chest 1990;98(6):1455-1462.
- Hammond MD, Bauer KA, Sharp JT, Rocha RD. Respiratory muscle strength in congestive heart failure. Chest 1990;98(5):1091-1094.
- Sapijaszko MJ, Brant R, Sandham D, Berthiaume Y. Nonrespiratory predictor of mechanical ventilation dependency in intensive care unit patients. Crit Care Med 1996;24(4):601-607.
- Smith IE, Shneerson JM. A progressive care programme for prolonged ventilatory failure: analysis of outcome. Br J Anaesth 1995;75(4):399-404.
- Scheinhorn DJ, Hassenpflug M, Artinian BM, LaBree L, Catlin JL. Predictors of weaning after 6 weeks of mechanical ventilation. Chest 1995;107(2):500-505.
- Aubier M, Murciano D, Lococguic Y, Viires N, Jacquens Y, Squara P, Pariente R. Effect of hypophosphatemia on diaphragmatic contractility in patients with acute respiratory failure. N Engl J Med 1985;313(7):420-424.
- Aubier M, Viires N, Piquet J, Murciano D, Blanchet F, Marty C, Gherardi R, Pariente R. Effects of hypocalcemia on diaphragmatic strength generation. J Appl Physiol 1985;58(7):2054-2061.
- American Association for Respiratory Care. Clinical practice guideline: management of airway emergencies. Respir Care 1995(7)749-760.
- Listello D, Sessler CN. Unplanned extubation: clinical predictors for reintubation. Chest 1994;105(5):1496-1503.
- Epstein SK. Etiology of extubation failure and the predictive value of the rapid shallow breathing index. Am J Respir Crit Care Med 1995;152(2):545-549.
- Whelan J, Simpson SQ, Levy H. Unplanned extubation: predictors of successful termination of mechanical ventilatory support. Chest 1994;105(6):1808-1812.
- Tindol GA Jr, DiBenedetto RJ, Kosciuk L. Unplanned extubations. Chest 1994;105(6):1804-1807.
- Vassal T, Anh NG, Gabillet JM, Guidet B, Staikowsky F, Offenstadt G. Prospective evaluation of self-extubations in a medical intensive care unit. Intensive Care Med 1993;19(6):340-342.
- Franck LS, Vaughan B, Wallace J: Extubation and reintubation in the NICU: identifying opportunities to improve care. Pediatr Nurs 1992;18(3):267-270.
- Garner JS, Hospital Infection Control Practices Advisory Committee, Centers for Disease Control and Prevention. Guidelines for Isolation Precautions in Hospitals. Atlanta GA: Centers for Disease Control and Prevention, 1-01-1996. www.cdc.gov
- Centers for Disease Control & Prevention. Guidelines for preventing the transmission of Mycobacterium tuberculosis in health-care facilities. Washington DC: Federal Register 1994;59(208), Friday Oct 28, 1994: 54242-54303. www.cdc.gov
Interested persons may copy these Guidelines for noncommercial
purposes of scientific or educational advancement. Please credit AARC and Respiratory