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EM Critical Care UNDERSTANDING AND CARING FOR CRITICAL ILLNESS IN EMERGENCY MEDICINE Noninvasive Ventilation: Update On Uses For The Critically Ill Patient Abstract N Robert T. Arntfield, MD, FRCPC Instructor, Department of Emergency Medicine, Mount Sinai School of Medicine, New York, NY Associate Editor Scott Weingart, MD, FACEP Assistant Professor, Department of Emergency Medicine, Mount Sinai School of Medicine, New York, NY; Director of Emergency Critical Care, Elmhurst Hospital Center, New York, NY Editorial Board Benjamin S. Abella, MD, MPhil, FACEP Assistant Professor, Department of Emergency Medicine and Department of Medicine / Section of Pulmonary Allergy and Critical Care, University of Pennsylvania School of Medicine, Philadelphia, PA; Clinical Research Director, Center for Resuscitation Science, Philadelphia, PA Jose Dionisio Torres, Jr., MD Clinical Instructor in Emergency Medicine, New York Hospital Queens, Flushing, NY Michael S. Radeos, MD, MPH Research Director, Department of Emergency Medicine, Flushing, NY; Assistant Professor of Emergency Medicine, Weill Cornell Medical College, New York, NY Peer Reviewers oninvasive ventilation (NIV) is a method of delivering oxygen by positive pressure mask that allows the clinician to postpone or prevent invasive tracheal intubation in patients who present to the emergency department (ED) with acute respiratory failure (ARF). There are 2 primary modalities of NIV: continuous positive airway pressure (CPAP) and bi-level positive pressure ventilation (BPAP) where the inspiratory positive airway pressure (IPAP) is higher than the expiratory positive airway pressure (EPAP). Continuous positive airway pressure appears to be more effective in reducing the need for tracheal intubation and possibly mortality in patients presenting with acute cardiogenic pulmonary edema (ACPE). Bi-level positive pressure ventilation appears to be more effective in reducing mortality and the need for tracheal intubation in patients with an acute decompensation of chronic obstructive pulmonary disease (COPD). Proper patient selection is critical in the use of NIV for ED patients. They must be able to cooperate with the respiratory therapist and tolerate the often uncomfortable nasal or face mask. The emergency clinician must be vigilant for signs of clinical deterioration in these patients as they may need an emergent definitive airway placed. This issue of EMCC examines the evidence supporting the use of NIV in various causes of ARF and reviews potential complications. Editor-in-Chief Volume 1, Number 2 Authors Lillian L. Emlet, MD, MS, FACEP Assistant Professor, Department of Critical Care Medicine, Department of Emergency Medicine, University of Pittsburgh Medical Center, Pittsburgh, PA; Program Director, EM-CCM Fellowship of the Multidisciplinary Critical Care Training Program, Pittsburgh, PA Thomas J. Abramo, MD, FAAP, FACEP Professor of Pediatrics & Emergency Medicine, Division Chief, Medical Director of Pediatric Emergency Medicine, Department of Pediatrics, Division of Pediatric Emergency Medicine, Director, Pediatric Emergency Medicine Fellowship Program, Medical Director of Pediatric Transport, Monroe Carell Jr. Children’s Hospital at Vanderbilt, Nashville, TN John M. Litell, DO Chief Fellow, Division of Pulmonary and Critical Care Medicine, Mayo Clinic, Rochester, MN Ryan G. K. Mihata, MD, MPH, FAAEM Clinical Assistant Professor of Emergency Medicine, Wright State University, Boonshoft School of Medicine, Dayton, OH CME Objectives Upon completion of this article, you should be able to: 1. 2. 3. 4. 5. Describe the potential advantages of NIV over endotracheal intubation. Describe the various forms of NIV. Describe techniques for initiation of NIV in the ED. Recognize the contraindications to NIV. Summarize the current evidence relating to the use of NIV. Date of original release: August 1, 2011 Date of most recent review: July 10, 2011 Termination date: August 1, 2014 Medium: Print and Online Method of participation: Print or online answer form and evaluation Prior to beginning this activity, see “CME Information” on the back page. Andy Jagoda, MD, FACEP Julie Mayglothling, MD Professor and Chair, Department Assistant Professor, Department of Emergency Medicine, Mount of Emergency Medicine, Sinai School of Medicine; Medical Department of Surgery, Division Director, Mount Sinai Hospital, New of Trauma/Critical Care, Virginia York, NY Commonwealth University, Richmond, VA William A. Knight, IV, MD Assistant Professor of Emergency Christopher P. Nickson, MBChB, Medicine, Assistant Professor MClinEpid Michael A. Gibbs, MD, FACEP of Neurosurgery, Emergency Supervising Registrar, Department Professor and Chief, Department Medicine Mid-Level Program of Emergency Medicine, Sir of Emergency Medicine, Maine Medical Director, University of Charles Gairdner Hospital, Perth, Medical Center, Portland, ME; Tufts Cincinnati College of Medicine, Australia University School of Medicine, Cincinnati, OH Boston, MA Jon Rittenberger, MD, MS Haney Mallemat, MD Assistant Professor, Department Robert Green, MD, BSc, DABEM, Associate Professor, Department of Emergency Medicine, of Critical Care / Emergency FRCPC University of Pittsburgh School Medicine, University of Maryland Associate Professor, Department of Medicine, Pittsburgh, PA; Medical Center, Baltimore, MD; of Anaesthesia: Division of Critical Attending, Emergency Medicine Department of Critical Care, Shock Care Medicine, Department of and Post-Cardiac Arrest Services, Trauma Center, Baltimore, MD Emergency Medicine, Dalhousie UPMC-Presbyterian Hospital, University, Halifax, Nova Scotia, Pittsburgh, PA Canada Evie Marcolini, MD, FAAEM Assistant Professor, Department of Emergency Medicine and Critical Care, Yale School of Medicine, New Haven, CT Emanuel P. Rivers, MD, MPH, IOM Vice Chairman and Director of Research, Department of Emergency Medicine, Senior Staff Attending, Departments of Emergency Medicine and Surgery (Surgical Critical Care), Henry Ford Hospital, Detroit, MI; Clinical Professor, Department of Emergency Medicine and Surgery, Wayne State University School of Medicine, Detroit, MI Isaac Tawil, MD Assistant Professor, Department of Surgery, Department of Emergency Medicine, University of New Mexico Health Science Center, Albuquerque, NM Research Editor Jennifer L. Galjour, MD, MPH Department of Emergency Medicine, Mount Sinai School of Medicine, New York, NY Case Presentation needs immediate tracheal intubation. In this issue of EMCC, we will examine the evidence and various recommendations for the use of NIV in a variety of patient presentations. The triage nurse calls you to the resuscitation room where you find a morbidly obese male who is gasping for air and is cool, pale, and diaphoretic. He is seated in the tripod position with nasal flaring, pursed-lip breathing, and rales to the apices, and he is speaking in 1-2 word sentences. His blood pressure is 240/160. EMS providers have given sublingual nitroglycerin but were unable to obtain IV access and have therefore not given furosemide. You realize that attempting tracheal intubation on this patient is a recipe for disaster. You have used NIV for patients with COPD, but you haven’t tried it in patients with ACPE. You page the respiratory therapist to bring the noninvasive ventilator, hoping that NIV will help the patient avoid the need for a difficult intubation. The respiratory therapist asks whether you want bi-level NIV or CPAP. You are not sure, so you ask the respiratory therapist which modality she believes is best. She recommends CPAP but wants to know what pressure to deliver. Again you defer to her knowledge, and she replies “10 cm H2O.” Finally, she wants to know whether you prefer a nasal mask, a face mask, or a helmet. You reply: “Whatever you think is best is fine with me.” As you closely monitor the patient on NIV, you set up for RSI, just in case. Indications For Noninvasive Ventilation In Acute Respiratory Failure There is no clear consensus on the indications for NIV in the various forms of ARF, and each study has unique inclusion and exclusion criteria. A simple way to approach the use of NIV in ARF is to assess for the presence of certain commonly accepted absolute contraindications. (See Table 2.) Unfortunately, there is no clear threshold for determining who needs immediate intubation. In the absence of contraindications, many dyspneic patients may be suitable candidates for a trial of NIV. Furthermore, in those patients needing definitive airway control, some authors have suggested that NIV may be useful in the preoxygenation phase of rapid sequence intubation (RSI). Note that a blood gas result may not return fast enough to guide decision-making. Introduction Acute respiratory failure is encountered in the prehospital setting, the ED, the medical wards, and the intensive care unit (ICU). In these challenging clinical scenarios, NIV can provide emergency clinicians with a promising treatment modality for acutely dyspneic patients. While tracheal intubation is considered the definitive method of airway control, this intervention is associated with additional risks and morbidity, related both to induction and tube placement, as well as ventilator-associated complications. While intubation is often instinctual for emergency clinicians confronted with a patient in respiratory failure, accumulating evidence suggests that NIV can decrease the need for tracheal intubation, decrease hospital length of stay, and save lives. Despite this, NIV is a temporizing measure that must be used selectively. Patients must be closely monitored to detect failure of therapy so that more definitive management is not delayed. Acute exacerbations of asthma and/or COPD and ACPE are 2 of the diagnoses that appear to benefit the most from NIV. The terminology used to describe NIV (Table 1) can be confusing, a fact that can interfere with communication between emergency clinicians and respiratory therapists, complicating the prompt application of time-sensitive therapy. In this article, the term NIV will be used routinely to refer to all modes of noninvasive ventilation. It is critical to recognize the patient in whom it is safe to try NIV and to avoid NIV in the patient who EMCC © 2011 Table 1. Noninvasive Ventilation Glossary 2 ACPE Acute cardiogenic pulmonary edema ARF Acute respiratory failure BPAP Bi-level positive airway pressure, in which the ventilator delivers different levels of pressure during inspiration and expiration. (While often used as a generic term, “BiPAP” and “BIPAP” are actually trademarked modes of NIV.) CPAP Continuous positive airway pressure; a fixed positive pressure throughout the respiratory cycle EPAP Expiratory positive airway pressure HARF Hypoxemic acute respiratory failure IPAP Inspiratory positive airway pressure NIV Ventilation delivered without an orotracheal or tracheostomy tube, including bi-level NIV via mask as well as negative pressure or abdominal compressive devices NPPV Noninvasive positive pressure ventilation; this differs from the term NIV only by its exclusion of negative pressure ventilation. Due to the rarity of the latter approach, NPPV and NIV are frequently used interchangeably PEEP Positive end-expiratory pressure Pressure Support The difference between inspiratory and expiratory positive airway pressure (IPAP - EPAP) VE Minute ventilation VT Tidal volume www.ebmedicine.net • Volume 1, Number 2 Critical Appraisal Of The Literature blood gases. Finally, is the timing of NIV important? Does faster door-to-mask time improve outcomes? This review of the existing data will take all of these considerations into account. Ovid MEDLINE® and PubMed were searched for the best literature pertaining to NIV in ARF from 1950 to the present. The Cochrane Library, CINAHL, and EMBASE were also searched. Over 300 articles were retrieved, and the references from relevant articles were searched for any articles that the search may have missed. In addition, the National Guideline Clearinghouse (www.guidelines.gov) was searched for NIV guidelines pertinent to the patient with acute respiratory distress. (See Table 3 on page pages 4 & 5.) When reviewing the sizable literature on NIV, it is important to remember an issue that makes the interpretation of results difficult. The point at which an eligible patient is enrolled in an NIV study is challenging to standardize. Studies that compare NIV with emergent intubation can suffer from confounding by indication. In other words, the intubated group is often sicker at baseline and may be more likely to have increased morbidity and mortality than the NIV group. However, as Voltaire said, “the perfect is the enemy of the good.” The evidence base for NIV in various indications and for its use in the ED setting is far from complete. Readers are encouraged to tread cautiously through the dense thicket of literature as it pertains to the acutely dyspneic patient in the ED. In addition to the difficulty in choosing eligible patients and comparing groups with equal chances of outcomes, it is essential to agree on relevant outcomes. Published outcomes range from decreased mortality to increased comfort of breathing. Additional possibilities include decreased respiratory rates, ease of breathing, decreased work of breathing, improved patient comfort, rates of tracheal intubation, ICU length of stay, and improvement in Going Deeper: How Noninvasive Ventilation Works In acute respiratory failures of any etiology, the patient is at risk of hypoxemic cardiac arrest. Historically, if these patients did not improve with a 100% nonrebreather mask, the clinician prepared for RSI. Noninvasive ventilation provides the clinician an opportunity to avoid tracheal intubation with its inherent complications,2 including hypoxemia due to prolonged attempts, esophageal intubation, dental or airway trauma, loss of protective reflexes with aspiration, and barotrauma. Nasal intubation, an occasional alternative to RSI, can result in sinusitis and posterior epistaxis.3 In simple terms, the various forms of NIV involve a pressurized oxygen/air mixture delivered by a mechanical ventilator through several types of mask. When a fixed pressure is used, this is referred to as CPAP. Alternatively, this fixed EPAP can be combined with a higher IPAP that is triggered by the patient’s inspiratory effort. The difference between EPAP and IPAP, called pressure support, augments ventilation and reduces work of breathing, both of which can reverse hypercapneic respiratory failure. This mode is called bi-level positive airway pressure, which is commonly referred to as BiPAP, although this is a proprietary name. Noninvasive ventilation improves lung mechanics by improving laminar airway flow by stenting closed airways or semi-obstructed airways thus decreasing atelectatic alveoli, improving pulmonary compliance, and reducing the work of breathing. Continuous positive airway pressure appears to mediate its therapeutic effects in ACPE through several interesting mechanisms. Contrary to popular belief, NIV does not simply force edema fluid out of flooded alveoli. Rather, the effects are due to the addition of positive pressure to the thoracic compartment, resulting in both preload and afterload reduction.4 In a study of acute lung injury (ALI) in pigs, Carvalho et al used invasive monitoring and computed tomography scanning to determine that improvements in oxygenation in pressure support ventilation were due to redistribution of pulmonary blood flow rather than recruitment of dependent zones.5 In addition, positive airway pressure reduces venous return to the heart. In patients without congestive heart failure (CHF), this decrease in preload may be clinically insignificant. In one study of 19 patients with COPD and acute respiratory failure, Confalonieri and colleagues found no significant changes in pulmonary artery pressures and cardiac output by Doppler echo- Table 2. Absolute And Relative Contraindications To Noninvasive Ventilation1 Absolute Contraindications • Need for immediate endotracheal intubation • Decreased level of consciousness • Excess respiratory secretions and risk of vomiting and aspiration • Past facial surgery precluding mask fitting Relative Contraindications • Hemodynamic instability • Severe hypoxia and/or hypercapnia, PaO2/FiO2 ratio of < 200 mm Hg, PaCO2 > 60 mm Hg • Poor patient cooperation • Lack of trained or experienced staff Used with permission from European Respiratory Society © 2010. www.ebmedicine.net • Volume 1, Number 2 3 EMCC © 2011 Patient Selection cardiography in 15 patients; 4 patients (21%) showed a significant reduction (> 15%) of cardiac output during NIV.6 Naughton and colleagues demonstrated another important hemodynamic benefit of CPAP in CHF.7 They studied 15 patients with CHF and 9 healthy controls, applying CPAP for 75 minutes and measuring inspiratory esophageal pressures and calculated left ventricular wall stress. Among CHF patients, CPAP seems to benefit patients with ACPE by decreasing left ventricular (LV) afterload and decreasing the inspiratory work of breathing without negatively affecting the cardiac index. Continuous positive airway pressure had no effect on healthy volunteers. While NIV has reported benefits in various etiologies of ARF, it is important to avoid its use in patients with absolute contraindications. There are no uniform indications for NIV, as each study focuses on one type of ARF and often excludes patients with alternative diagnoses. Table 4 on page 7 shows indications and initial ventilator settings described in the methods sections of selected clinical trials. Noninvasive Ventilation In The Prehospital Setting Plaisance and colleagues performed a prehospital Table 3. Selected Published Guidelines For The Use Of Noninvasive Ventilation (continued on page 5) Organization Topic Type of Guideline Recommendations American College of Emergency Physicians (ACEP) Clinical Policies Subcommittee (Writing Committee) on Acute Heart Failure Syndromes8 Clinical Policy: Critical Issues in the Evaluation and Management of Adult Patients Presenting to the Emergency Department with Acute Heart Failure Syndromes Evidence-based Use 5 to 10 cm H2O CPAP by nasal or face mask as therapy for dyspneic patients with AHF syndrome without hypotension or the need for emergent intubation to improve heart rate, respiratory rate, and blood pressure and to reduce the need for intubation and possibly inhospital mortality (Grade B). Consider using bi-level NIV as an alternative to CPAP for dyspneic patients with AHF syndrome; however, data about the possible association between bi-level NIV and myocardial infarction remain unclear (Grade C). British Thoracic Society9 Update of 2002 British Thoracic Society guideline for ARF in COPD Evidence-based NIV should be considered in all patients with an acute exacerbation of COPD in whom a respiratory acidosis (pH < 7.35, PaCO2 > 6 kPa [45 mm Hg]) is present (Not graded). Quality Standards Subcommittee of the American Academy of Neurology10 Practice Parameter Update: The Care of the Patient with Amyotrophic Lateral Sclerosis: Drug, Nutritional, and Respiratory Therapies Evidence-based NIV should be considered to treat respiratory insufficiency in ALS, both to lengthen survival (Level B) and to slow the decline of forced vital capacity (Level B). NIV may be considered to improve quality of life (Level C). American College of Physicians – American Society of Internal Medicine (ACPASIM) and the American College of Chest Physicians (ACCP)11 Management of Acute Exacerbations of Chronic Obstructive Pulmonary Disease: A Summary and Appraisal of Published Evidence Evidence-based Bi-level NIV is a beneficial support strategy that decreases the risk for invasive mechanical ventilation and possibly improves survival in selected hospitalized patients with respiratory failure (Not graded). Global Initiative for Chronic Obstructive Lung Disease (GOLD)12 Global Strategy for the Diagnosis, Management, and Prevention of Chronic Obstructive Pulmonary Disease Evidence-based NIV improves respiratory acidosis (increases pH and decreases PaCO2) and decreases respiratory rate, severity of breathlessness, and length of hospital stay in patients with acute exacerbations of COPD (Evidence A). Mortality—or its surrogate, intubation rate—is reduced by this intervention (Not graded). American College of Critical Care Medicine13 Recommendations for end-of-life care in the intensive care unit: a consensus statement by the American Academy of Critical Care Medicine Consensus A patient who has specifically refused intubation but desires other aspects of intensive care with the goal of prolonging survival may choose NIV (Not graded). NIV may be used as a palliative technique to minimize dyspnea. When used for the latter indication, NIV should be stopped when it is no longer effective at relieving that symptom (Not graded). EMCC © 2011 4 www.ebmedicine.net • Volume 1, Number 2 study to determine whether the timing of NIV mattered.14 They enrolled patients with clinical signs of pulmonary edema and SpO2 < 90% but excluded anyone with COPD. They compared immediate CPAP versus a 15-minute delay in administering CPAP and found that dyspnea scores were significantly improved in the early group compared with the delayed group at 15 minutes (4 ± 2 vs 7 ± 2, P = 0.003). There was an impressive reduction in tracheal intubation between the groups, which was statistically significant (1 of 63 in the early CPAP group vs 8 of 61 in the late group, P = 0.01). In a systematic review, Simpson and Bendall found only 3 randomized trials that enrolled mostly patients with ACPE.15 Their results suggest that prehospital NIV may reduce both mortality and tracheal intubation by approximately 75%. The number of patients remains small, but the potential benefits of the relatively unexplored area of prehospital NIV may be substantial. Overall, noninvasive ventilation shows promise in the prehospital setting, but more research is needed to determine its cost-effectiveness. Acute Exacerbation Of Chronic Obstructive Pulmonary Disease Ram and colleagues performed a Cochrane systematic review of NIV in acute exacerbations of COPD based on 14 clinical trials including 758 total Table 3. Selected Published Guidelines For The Use Of Noninvasive Ventilation (continued from page 4) Organization Topic Type of Guideline Recommendations Infectious Diseases Society of America/American Thoracic Society16 Consensus Guidelines on the Management of CommunityAcquired Pneumonia in Adults Consensus Patients with hypoxemia or respiratory distress should receive a cautious trial of NIV unless they require immediate intubation because of severe hypoxemia (PaO2/FiO2 ratio < 150) and bilateral alveolar infiltrates (Moderate recommendation; level I evidence). National Heart, Lung, and Blood Institute Expert Panel Report 317 Expert Panel Report 3: Guidelines for the Diagnosis and Management of Asthma Evidence-based Other adjunct therapies to avoid intubation include intravenous beta2-agonists, intravenous LTRAs, and NIV; however, insufficient data are available to make recommendations regarding these possible adjunct therapies (Evidence D). European Society of Cardiology18 European Society of Cardiology Guidelines for the Diagnosis and Treatment of Acute and Chronic Heart Failure Evidence-based NIV with PEEP should be considered as early as possible in every patient with acute cardiogenic pulmonary oedema and hypertensive AHF as it improves clinical parameters including respiratory distress. NIV with PEEP improves LV function by reducing LV afterload. NIV should be used with caution in cardiogenic shock and RV failure; however, the authors were unable to find evidence to support this cautious approach in RV failure or cardiogenic shock (Class I, Level C). Early application of NIV in patients with acute cardiogenic pulmonary oedema reduces both the need for intubation and short-term mortality (Class IIa, Level B). Intubation and mechanical ventilation should be restricted to patients in whom oxygen delivery is not adequate by oxygen mask or NIV and patients with increasing respiratory failure or exhaustion as assessed by hypercapnia (Class IIa, Level B). Surviving sepsis campaign19 International Guidelines for Management of Severe Sepsis and Septic Shock Evidence-based The guideline committee suggests that noninvasive mask ventilation only be considered in the minority of ALI/ARDS patients with mild-moderate hypoxemic respiratory failure (responsive to relatively low levels of pressure support and PEEP) with stable hemodynamics who can be made comfortable and easily arousable, are able to protect the airway, are able to spontaneously clear the airway of secretions, and are anticipated to recover rapidly from the precipitating insult. A low threshold for airway intubation should be maintained (Grade 2B). Abbreviations: AHF, acute heart failure; ALI, acute lung injury; ALS, amyotrophic lateral sclerosis; ARDS, acute respiratory distress syndrome; ARF, acute respiratory failure; COPD, chronic obstructive pulmonary disease; CPAP, continuous positive airway pressure; LTRAs, leukotriene receptor antagonists; LV, left ventricular; NIV, noninvasive ventilation; PEEP, positive end-expiratory pressure; RV, right ventricular. www.ebmedicine.net • Volume 1, Number 2 5 EMCC © 2011 patients. They found that it reduced mortality by approximately 50% (risk ratio [RR] 0.52; 95% CI, 0.35-0.76), decreased the need for intubation by approximately 60% (RR 0.41; 95% CI, 0.33-0.53), and reduced treatment failures by 52% (RR 0.48; 95% CI, 0.37-0.63). Additionally, patients on NIV showed a rapid improvement within the first hour in pH (weighted mean difference [WMD] 0.03; 95% CI, 0.02-0.04), PaCO2 (WMD -0.40 kPa; 95% CI. -0.78 to -0.03), and respiratory rate (WMD -3.08 breaths per minute; 95% CI, -4.26 to -1.89). Complications associated with treatment and length of hospital stay were also reduced in the bi-level group.20 The evidence shows impressive results in patients with an acute exacerbation of COPD. Its use should be strongly considered in these patients upon their arrival to the ED. bi-level NIV group and 28.5 ± 22.6% in the control group (P = 0.006). Hospitalization was required for 3 of 17 patients (17.6%) in the bi-level NIV group as compared to 10 of 16 patients (62.5%) in the control group (P = 0.0134). Among the studies included in the Cochrane review was one by Meduri and colleagues. They performed an observational study of 17 patients with acute asthma and provided bi-level NIV using a face mask connected to a conventional ventilator.23 While first applying the mask, initial settings included 10 cm H2O IPAP and 0 cm H2O EPAP. Once the mask was sealed to prevent air leaks, 3 to 5 cm H2O EPAP was added on, and pressure support ventilation was increased to maintain a tidal volume (VT) of 7 mL/kg. All but 1 of the patients tolerated NIV, demonstrating improvements in PCO2 and PaO2/FiO2. The other patients did not show improvement in the blood gas and were intubated. A few other studies suggest that there may be a benefit of NIV in acute asthma. Subsequent to the Cochrane review, Soma and colleagues enrolled 44 patients with acute exacerbation of asthma who received nebulized medications and hydrocortisone. The patients were randomized into either high pressure (8 cm H2O IPAP and 6 cm H2O EPAP) or low-pressure (6 cm H2O IPAP and 4 cm H2O EPAP) bi-level NIV groups. The only improvements they noted were in wheezing and accessory muscle use scores.24 Summarizing these findings, it is reasonable to consider NIV for patients with an acute exacerbation of asthma, but the effect will likely be modest, and the emergency clinician must remain prepared to intubate. Acute Exacerbation Of Asthma While NIV is considered an effective first-line treatment for acute exacerbation of COPD, the evidence supporting NIV for asthma is less convincing. This may be explained by the fundamental difference between asthma and COPD. The hallmark of emphysema is the destruction of pulmonary architecture that leads to premature collapse of the airways. This leads to inadequate ventilation and retention of CO2. Inspiratory positive airway pressure may functionally stent these terminal airways and allow for more effective ventilation. On the other hand, asthma is manifested by inflammation, edema, and partial or complete obstruction of small airways. Noninvasive ventilation pressures, as they are currently used, may not be sufficient to overcome this degree of obstruction and associated resistance. This is reflected by the inconsistent pressure support settings that appear in the literature regarding NIV in acute asthma. Ram and colleagues performed a Cochrane systematic review and meta-analysis. Starting with 11 clinical trials, they excluded 10, leaving only 1 randomized controlled trial.21 They concluded that the evidence supporting NIV for exacerbations of asthma was potentially promising but that a large randomized controlled trial was needed. In a pilot prospective randomized trial, Soroksky and colleagues enrolled ED patients whose forced expiratory volume in 1 second (FEV1) was < 60% predicted after 30 minutes of standard treatment.22 They excluded patients with hemodynamic instability or who smoked for more than 10 years. Patients were randomized to either bi-level NIV or a sham NIV, which was set at 1 cm H2O of positive airway pressure and had holes drilled in the tubing to eliminate positive pressure. Eighty percent of patients in the bi-level NIV group reached the predetermined primary end points (an increase of at least 50% in FEV1 as compared to baseline) versus 20% of control patients (P < 0.004). Mean rise in FEV1 was 53.5 ± 23.4% in the EMCC © 2011 Acute Cardiogenic Pulmonary Edema For years, it appeared that CPAP might be effective in reducing mortality in patients with ACPE. However, a large multicenter randomized controlled trial comparing CPAP, bi-level NIV, and standard oxygen therapy brings the mortality benefit into question. The Three Interventions in Cardiogenic Pulmonary Oedema (3CPO) trial enrolled 1069 patients, of which 367 received standard oxygen therapy, 346 received CPAP, and 356 received bi-level NIV.25 There was no significant difference in 7-day mortality between the groups. There was also no difference in rates of tracheal intubation. The only significant improvements seen with either NIV group were modest reductions in dyspnea score, heart rate, acidosis, and hypercapnia. It also made no difference if the patient used CPAP or bi-level NIV. In a recent meta-analysis by Weng and colleagues, the authors reviewed 31 randomized controlled trials involving 2887 patients, including the 3CPO trial.33 They concluded that CPAP versus standard therapy reduces mortality (RR 0.64; 95% CI, 0.44-0.92), and both CPAP and bi-level ventilation reduce the need 6 www.ebmedicine.net • Volume 1, Number 2 Table 4. Indications For Noninvasive Ventilation Study Diagnosis Enrollment Criteria NIV Settings 26 Gupta et al. Asthma RR > 30 HR > 100 SpO2 < 92% or PaO2 < 60 mm Hg 8 cm H2O IPAP, 4 cm H2O EPAP, titrated in 2 cm H2O increments to a maximum of 20 cm H2O IPAP and 10 cm H2O EPAP Soma et al.24 Asthma SpO2 > 90% on room air EXCLUDED COPD, CHF, pneumonia, and pregnancy Low pressure group: 6 cm H2O IPAP and 4 cm H2O EPAP High pressure group: 8 cm H2O IPAP and 6 cm H2O EPAP Delay et al.27 Morbid obesity BMI > 40 kg/m2 Elective surgery EXCUDED emergency procedures and other comorbidities 6 cm H2O IPAP and 4 cm H2O EPAP, after 20 seconds increased to 8-10 cm H2O IPAP and 6 cm H2O EPAP Plaisance et al.14 ACPE Clinical ACPE, SpO2 < 90% on 15 L/min face mask EXCLUDED COPD Early CPAP at 7.5 cm H2O Late CPAP at 7.5 cm H2O begun 15 minutes after early CPAP group Moritz et al.28 ACPE Clinical ACPE, SpO2 < 90% on > 5 L/min face mask EXCLUDED COPD, pneumonia, and renal failure CPAP at 10 cm H2O delivered by Boussignac mask compared with bi-level NIV with EPAP of 5 cm H2O and IPAP that was adjusted to maintain a VT of 8 to 10 mL/kg. The pressure support needed to reach this VT was approximately 12. Thus, IPAP was approximately 17 cm H2O. Ferrer et al.29 AHRF ICU patients PaO2 < 60 mm Hg for > 6 hours or SpO2 < 90% on > 5 L/min face mask EXCLUDED hypercapnia PaCO2 > 45 mm Hg 16 ± 3 cm H2O IPAP (range 10-24) 7 ± 2 cm H2O EPAP (range 4-12) Conti et al.30 Acute exacerbation of COPD ICU consults of ED patients pH < 7.32 Bicarbonate > 30 mEq/L PaCO2 > 45 mm Hg PaO2 < 45 mm Hg on room air Bi-level NIV at IPAP of 21 ± 2 cm H2O and EPAP of 5 cm H2O (pressure support 16 ± 2 cm H2O) compared with mechanical ventilation Jolliet et al.31 Severe CAP ICU Focal or multilobar pneumonia RR ≥ 30/min PaCO2 ≥ 45 mm Hg PaO2/FiO2 < 300 BP systolic ≤ 90 mm Hg and diastolic ≤ 60 mm Hg Vasopressor use ≥ 4 hours Bi-level NIV at 20 cm H2O IPAP and 5 cm H2O EPAP (pressure support 15 cm H2O) Confalonieri et al.32 CAP RR > 35/min PaO2 > 68 mm Hg while on FiO2 ≥ 0.4 PaO2/FiO2 < 250 while on FiO2 ≥ 0.5 PaCO2 ≥ 50 mm Hg BP systolic ≤ 90 mm Hg and diastolic ≤ 60 mm Hg Vasopressor use ≥ 4 hours Bi-level NIV with 19.7 ± 4.7 cm H2O IPAP and 4.9 ± 1.7 cm H2O EPAP (pressure support 14.8 ± 4.7 cm H2O) Abbreviations: ACPE, acute cardiogenic pulmonary edema; AHRF, acute hypoxemic respiratory failure; BMI, body mass index; BP, blood pressure; CAP, community-acquired pneumonia; CHF, congestive heart failure; COPD, chronic obstructive pulmonary disease; CPAP, continuous positive airway pressure; ED, emergency department; EPAP, expiratory positive airway pressure; HR, heart rate; ICU, intensive care unit; NIV, noninvasive ventilation; RR, respiratory rate; VT, tidal volume. www.ebmedicine.net • Volume 1, Number 2 7 EMCC © 2011 Clinical Pathway: Management Of Patients With Respiratory Distress And Special Circumstances Using Noninvasive Ventilation Does the patient have blunt thoracic trauma? YES Is the patient hypoxic despite 100% oxygen supplementation? NO YES Use bi-level NIV, start at 10 cm H2O IPAP and 6 cm H2O (Class II) NO Does patient appear to have a neuromuscular cause for their respiratory failure? YES Continue conventional trauma resuscitation (Class I) Improving with oxygen? NO YES Does patient appear to have a DNI order or is patient on palliative care? Use bi-level NIV, start at 10 cm H2O IPAP and 5 cm H2O EPAP (Class II) Continue conventional therapy (Class I) NO YES Improving with oxygen and care appropriate for underlying disease process? NO YES NO Does patient appear to have ALI/ARDS or acute chest syndrome from sickle cell as a reason for their respiratory distress? Use NIV, depending on underlying disease process (Class I for COPD and ACPE) Continue conventional therapy (Class I) YES NIV cannot be recommended at this time (Class Indeterminate) Please see Class of Evidence definitions on page 10 Abbreviations: ACPE, acute cardiogenic pulmonary edema; ALI, acute lung injury; ARDS, acute respiratory distress syndrome; COPD, chronic obstructive pulmonary disease; DNI, do not intubate; EPAP, expiratory positive airway pressure; IPAP, inspiratory positive airway pressure; NIV, noninvasive ventilation EMCC © 2011 8 www.ebmedicine.net • Volume 1, Number 2 Clinical Pathway: Management Of Patients With Respiratory Distress With Noninvasive Ventilation Is patient obtunded, hypoxemic, or unable to protect airway? YES • • Prepare for rapid sequence tracheal intubation (Class I) Consider using NIV for pretreatment to intubation (Class I) NO Does patient appear to have an acute exacerbation of COPD or asthma? YES Improving with albuterol, ipratropium and methylprednisolone? YES NO Continue conventional therapy (Class I) Use bi-level NIV, start at 10 cm H2O IPAP and 5 cm H2O EPAP (COPD: Class I; Asthma: Class II) NO Does patient appear to have ACPE? YES Improving with oxygen, nitoglycerin and furosemide or other diuretic? YES Continue conventional therapy (Class I) NO Does patient appear to have pneumonia with hypoxia? YES Continue conventional therapy (Class I) NO YES Use CPAP, start at 10 cm H2O (Class I) Improving with oxygen and IV antibiotics? YES Does patient appear to have another reason for their respiratory distress? NO NO Use bi-level NIV, start at 10 cm H2O IPAP and 5 cm H2O EPAP (Class I) Go to Clinical Pathway: Management Of Patients With Respiratory Distress And Special Circumstances Using Noninvasive Ventilation on page 8 Please see Class of Evidence definitions on page 10 Abbreviations: ACPE, acute cardiogenic pulmonary edema; CPAP, continuous positive airway pressure; COPD, chronic obstructive pulmonary disease; EPAP, expiratory positive airway pressure; IPAP, inspiratory positive airway pressure; IV, intravenous; NIV, noninvasive ventilation www.ebmedicine.net • Volume 1, Number 2 9 EMCC © 2011 Clinical Pathway: The Reevaluation Of Patients Placed On Noninvasive Ventilation Is the patient deteriorating clinically (decreasing mental status, hypotension, hypoxemia rising PCO2? YES Prepare for immediate tracheal intubation (Class I) YES Consider sedation with remifentanil or dexmedetomidine (Class III) YES Improving with change of mask? NO Is the patient complaining or becoming more anxious? NO Is the patient complaining about the mask or is there air leak? NO YES Change NIV settings to maximize tidal volume, oxygenation, and PCO2 (Class I) Continue conventional therapy (Class I) NO Does patient appear to be tolerating NIV and improving clinically? YES Admit to appropriate service and level of care (Class Indeterminate) Abbreviations: EPAP, expiratory positive airway pressure; IPAP, inspiratory positive airway pressure; NIV, noninvasive ventilation Class Of Evidence Definitions Each action in the clinical pathways section of EMCC receives a score based on the following definitions. Class I • Always acceptable, safe • Definitely useful • Proven in both efficacy and effectiveness Level of Evidence: • One or more large prospective studies are present (with rare exceptions) • High-quality meta-analyses • Study results consistently positive and compelling Class II • Safe, acceptable • Probably useful Level of Evidence: • Generally higher levels of evidence • Non-randomized or retrospective studies: historic, cohort, or case control studies • Less robust RCTs • Results consistently positive Class III • May be acceptable • Possibly useful • Considered optional or alternative treatments Level of Evidence: • Generally lower or intermediate levels of evidence • Case series, animal studies, consensus panels • Occasionally positive results Indeterminate • Continuing area of research • No recommendations until further research Level of Evidence: • Evidence not available • Higher studies in progress • Results inconsistent, contradictory • Results not compelling Significantly modified from: The Emergency Cardiovascular Care Committees of the American Heart Association and represen- tatives from the resuscitation councils of ILCOR: How to Develop Evidence-Based Guidelines for Emergency Cardiac Care: Quality of Evidence and Classes of Recommendations; also: Anonymous. Guidelines for cardiopulmonary resuscitation and emergency cardiac care. Emergency Cardiac Care Committee and Subcommittees, American Heart Association. Part IX. Ensuring effectiveness of communitywide emergency cardiac care. JAMA. 1992;268(16):2289-2295. This clinical pathway is intended to supplement, rather than substitute for, professional judgment and may be changed depending upon a patient’s individual needs. Failure to comply with this pathway does not represent a breach of the standard of care. Copyright © 2011 EB Medicine. 1-800-249-5770. No part of this publication may be reproduced in any format without written consent of EB Medicine. EMCC © 2011 10 www.ebmedicine.net • Volume 1, Number 2 for tracheal intubation. Adverse effects of the hemodynamic changes associated with NIV have been reported. Hypotension is possible in hypovolemic patients, due the reduction in preload and cardiac output. A randomized controlled trial by Mehta and colleagues comparing CPAP to bi-level NIV in patients with ACPE suggested a concerning relationship between NIV and myocardial ischemia.34 This study was terminated early due to an excess of myocardial infarction (MI) in the bi-level NIV group. Newer and larger trials have refuted these findings, including the 3CPO trial. Bellone and colleagues specifically examined the occurrence of MI in patients presenting with ACPE and found no statistical difference in MI between the CPAP and bi-level NIV groups.35 Pediatric Use Of Noninvasive Ventilation Community Acquired Pneumonia There are many ways to deliver NIV, and it is essential for the emergency clinician to communicate with the respiratory therapy department to know what is available in their facility. For a detailed overview of equipment options, we refer the reader to excellent reviews by Scala and Naldi38 and Schönhofer and Sorter-Leger.39 We will cover the key issues regarding the application of NIV in the ED. The goal of NIV in the ED patient is to stabilize their respiratory status. Using the techniques discussed in this article – mask sizing, delivery of sufficient but not excessive pressures, and management of patient anxiety by offering reassurance and possibly sedation – the patient’s ED course will be optimized. The evidence base for NIV in pediatrics is limited but suggests that there may be benefit in ARF. Yanez and colleagues performed a randomized controlled trial in 50 patients in 2 pediatric ICUs.40 Patients predominantly had respiratory syncytial virus/ bronchiolitis. Noninvasive ventilation was applied as bi-level NIV with IPAP ranging from 12 to 18 cm H2O and EPAP ranging from 6 to 12 cm H2O. The investigators found a significant reduction in tracheal intubation: 7 of 25 NIV patients versus 15 of 25 controls (RR 0.47; 95% CI, 0.23-0.9, P = 0.046). Tools And Techniques: Practical Considerations For Noninvasive Ventilation The evidence supporting NIV in CAP is also conflicting. Carron and colleagues studied 64 patients on ICU admission and placed them on bi-level NIV starting at 15 cm H2O IPAP and 5 cm H2O EPAP (thus providing 10 cm H2O of pressure support).36 Noninvasive ventilation was successful in avoiding intubation in 28 (44%) patients and failed in 36 (56%) patients. In a logistic regression model, the change in PaO2/FiO2 and the oxygenation index (OI = mean airway pressure × FiO2 × 100/PaO2) was statistically associated with failure of NIV and need for intubation.36 In their guidelines on the management of CAP,16 the Infectious Diseases Society of America and the American Thoracic Society recommend cautious usage of NIV. They suggest that NIV be tried in patients with CAP and hypoxia and respiratory distress unless they require immediate intubation. They define need for immediate intubation as severe hypoxemia (PaO2/ FiO2 < 150) or bilateral alveolar infiltrates. Confalionieri and colleagues performed a casecontrol study of patients with pneumocystis carinii pneumonia (PCP) and ARF admitted to an infectious disease ICU.37 They applied bi-level NIV to 24 patients and matched them with controls that had been intubated prior to arriving at the ICU. They found that 67% of the bi-level NIV patients avoided tracheal intubation and had a shorter course in the ICU. While the authors tried to match the controls as closely as possible to the cases, there is still potential for bias, which might inflate the benefits of bi-level NIV. Yet, it is tempting to believe that a trial of bi-level NIV may prevent intubation in patients with PCP. Thus, a cautious trial of bi-level NIV in CAP is warranted, with tracheal intubation equipment on standby. Patients in respiratory distress should be tracheally intubated immediately if there is any doubt that they would be able to tolerate NIV.16 www.ebmedicine.net • Volume 1, Number 2 Pressure Settings For CPAP, it is reasonable to set the pressure at 10 cm H2O for suspected ACPE. The pressure can be adjusted up or down depending on patient comfort. For bi-level NIV, start at 15 cm H2O IPAP and 5 cm H2O EPAP. The pressure support in this case is 10 cm H2O (IPAP minus EPAP). These pressures may be titrated up or down depending on the combination of clinical effect as well as patient comfort. Based on the available literature, pressures should not exceed 25 cm H2O at any point, regardless of the mode of NIV being used. In order to maintain the desired pressures, it is important to achieve a good seal with the NIV mask. Nasal masks are the simplest, but the patient must keep their mouth closed or the pressures will drop. The more common facial masks may achieve a better seal. Finally, the patient is key to the success of NIV. If the patient does not tolerate the mask or is anxious, the NIV trial may fail. The patient may also trigger the NIV machine prematurely and initiate an inappropriate breath. Newer NIV models have been developed with much more sophisticated circuitry that adjust the pressures and inspiratory and expiratory times when there is a leak. An experienced respiratory therapist is essential in successfully implementing NIV in the ED. 11 EMCC © 2011 Mask Options And Sizing pared to the facemask, while leading to significantly fewer interruptions due to discomfort and complications, such as skin necrosis.45 Nasal Mask Nasal NIV is often used for the patient who has a history of obstructive sleep apnea (typically CPAP mode) or COPD who needs nocturnal ventilation (typically bi-level NIV mode). With the nasal mask, the airway is depressurized and no longer a closed system when the patient opens his or her mouth. It causes less claustrophobia than the oronasal/facial or helmet masks. It also minimizes aspiration if vomiting occurs. In order to prevent pressure drop when the patient opens their mouth, nasal masks should only be used in ED patients who can reliably keep their mouth closed or cannot tolerate a face mask. Boussignac Mask The Boussignac mask is a promising new mask that provides CPAP up to 7.5 cm H2O without requiring a separate flow generator or ventilator. The apparatus operates with high flow oxygen and compares favorably with bi-level NIV in hypercapnic patients.28 This modality seems ideal for prehospital management of ARF in remote areas, but more research is needed before it can be recommended as an option for NIV in the ED. (See Figures 3 and 4.) Oronasal (Face) Mask Delivery of NIV via a facemask is the most common method used by emergency medical service personnel, in the ED, and in the ICU. One mask does not fit all when it comes to patients’ faces, and it is therefore important to stock a variety of sizes. A good fit will allow less air leak and improve patient comfort. Along with being attentive to the size of the patient’s face, the clinician should take note of both the edentulous patient who has no teeth to give the mouth firm structure and the bearded patient, both of whom are at risk for a poor mask fit and consequential air leaks. One small randomized controlled trial demonstrated that facemasks are significantly better tolerated by patients when compared to nasal masks for ARF from CHF.41 There was no difference in performance, however, with similar rates of intubation between these 2 groups. Another study found that the facemask was less tolerable despite allowing less air leakage than the nasal mask in patients with COPD exacerbation.42 (See Figures 1 and 2.) Figure 1. Typical Noninvasive Ventilation Interface And Displays Settings of 5 cm H2O IPAP, 4 cm H2O EPAP, RR 13, FiO2 40% Cephalic Mask There are facemasks that cover the entire anterior surface of the face. The theoretical advantage is that it spreads out the pressure, reducing the nasal bridge breakdown of nasal or facial masks. Cuvelier and colleagues found no difference in 34 patients that they randomized to cephalic and oronasal masks.43 However, 1 patient from the cephalic group dropped out due to claustrophobia. Helmet The helmet is an uncommonly used interface for NIV in the ED, though studies outside the ED suggest that it may hold promise for patients who are intolerant of other masks. In a small study of postabdominal surgery patients, the helmet was better tolerated with fewer complications (such as air leaks and pneumonia) compared to face mask.44 In a small case-control study in immunocompromised ICU patients with hypoxemic ARF, the helmet was shown to be of equal benefit in avoiding intubation, com- EMCC © 2011 Classic settings of 10 cm H2O IPAP, 5 cm H2O EPAP, RR 12. FiO2 40% 12 www.ebmedicine.net • Volume 1, Number 2 Clinical Course In The ED • Oxygen requirement in relation to the pulse oximetry • Pulse oximetry • Blood gases (see below) • Tidal volumes and minute ventilation Once the patient is placed on NIV, it is important to monitor the patient closely for clinical deterioration. Assume that NIV will fail, and prepare the necessary equipment for RSI. Consult with the respiratory therapist to ensure that the mask interface is comfortable for the patient and that the NIV modality – CPAP versus bi-level NIV – is set up as needed for the specific disease process. Clinical parameters that one should follow include: • Patient tolerance of NIV • Increase in secretions • Mental status change • Synchronous breathing with the ventilator • Air leaks • Respiratory rate • Tidal volume changes in relation to respiratory rate Respiratory rate and work of breathing should decrease with intervention. However, respiratory rate is not the same as ventilation, so it is important to check an arterial blood gas for pH and PCO2. There is promising data that pH – but not PCO2 – in venous blood gases correlates with arterial blood gases. This is exciting because it is more convenient to sample venous blood rather than performing an arterial puncture.46 A recent meta-analysis by Lim and Kelly suggests that in COPD patients, pH and bicarbonate show good correlation, but the correlation between venous and arterial PCO2 is less reliable.47 There is not enough evidence to support the use of venous PCO2 in patients with COPD, but pH may be useful. A rise in pH in a patient placed on NIV may well reflect improved ventilation and improvement of their hypercapnia. Furthermore, Kelly and Klim studied a convenience sample of 46 patients on NIV who needed a blood gas.48 They measured transcutaneous CO2 (PtCO2) and compared it with the PCO2 from the arterial blood gas (PaCO2). They found very poor correlation between PtCO2 and PaCO2. Indeed, the transcutaneous measurement sometimes dramatically underestimated the true arterial CO2. This is understandable as each modality of measuring the partial pressure of CO2 has limitations. The gold standard is the arterial gas, where CO2 is measured after diffusion has occurred at the alveolar level. The venous CO2 may reflect hypercapnia, but this value may drop significantly upon passage through the lung. End-tidal CO2 varies with dead space ventilation and may grossly underestimate the arterial CO2. Transcutaneous CO2 is dependent upon diffusion through the skin and may approach arterial levels when the skin is warm and well perfused. Thus, caution must be exercised when using PtCO2 in patients on NIV as there is no support for PtCO2 in this setting. Due to the poor agreement between PtCO2 and PaCO2, transcutaneous CO2 monitoring in NIV cannot be recommended. Figure 2. Ideal Fit For Noninvasive Ventilation Face Mask Note the tight fit of the mask with head straps to secure it on. Deterioration Parameters of failure in a patient on NIV include: • Vomiting • Persistent coughing • Aspiration • Progressive respiratory distress • Respiratory arrest • Loss of consciousness • Respiratory rate rising greater than 35-40 • Persistent hypoxia despite supplemental oxygenation • Hemodynamic instability or shock www.ebmedicine.net • Volume 1, Number 2 13 EMCC © 2011 Do-Not-Intubate And Palliative Care Patients • Worsening arterial pH, PCO2, PO2, or venous pH • Worsening PaO2/FiO2 ratio Nursing home or hospice patients often present to the ED in respiratory distress. While a clear do-notintubate (DNI) order accompanying the patient makes the decision on whether to intubate less vexing, there is always the option of NIV. By definition, NIV is not invasive. It is important to explain to the patient and caregiver that this modality is an option. There is very little guidance on what the right course of action is in these cases. Levy and colleagues enrolled 114 patients on bi-level NIV who also happened to have DNI status. Noninvasive positive pressure ventilation was provided with 13.4 ± 0.3 cm H2O IPAP and 5.0 ± 1 cm H2O EPAP.51 There was a 43% survival to discharge. Patients most likely to survive were those with ACPE and COPD. Additional markers of survival were alert mental status and good, strong cough. Bulow and colleagues studied 38 patients who had a DNI order and were given NIV.52 The group with the highest survival was patients with COPD. They concluded that NIV is an option for patients with a DNI order and COPD, while other diagnoses may not fare as well. Curtis and colleagues from the Society of Critical Care Medicine Palliative Noninvasive Positive Pressure Ventilation Task Force developed an approach for considering the use of NIV for those who wish to forego tracheal intubation.53 They provide a detailed approach to communicating with the patient Complications Of Noninvasive Ventilation In a comprehensive review, Gay described several potential complications of NIV.49 Problems start at the interface, as each type of mask has its problems. Obstructed nasal passages would preclude using the nasal mask. Problems related to pressure include sinus pain, gastric insufflation, and pneumothorax. Problems related to airflow include dryness, nasal congestion, and eye irritation. Major complications include severe hypoxemia and aspiration as well as the rare occurrences of hypotension and mucus plugging. Other complications include claustrophobia, air leaks from poor mask seal, and pressure sores at the nasal bridge. Special Circumstances Acute Respiratory Distress Syndrome And Acute Lung Injury Acute lung injury is a common condition that is characterized by acute severe hypoxia that is not due to left atrial hypertension. The term ALI encompasses a continuum of clinical and radiographic changes that affect the lungs, with the acute respiratory distress syndrome (ARDS) representing the more severe end of this continuum. Clinically, these patients present as non-cardiogenic pulmonary edema and respiratory failure in a critically ill patient. Despite advances in our understanding of the pathophysiology and management of ALI, it is still associated with a high mortality. Agarwal and colleagues performed a meta-analysis of NIV use in ALI and ARDS.50 They found an estimated 50% NIV failure rate, with a pooled intubation rate of 48% (95% CI, 39-58) and a pooled mortality rate of 35% (95% CI, 26-45). The authors urge caution in this clearly high-risk group. Figure 4. Boussignac CPAP Schematic Boussignac CPAP works the same way as the turbines of a jet engine Oxygen Supply Oxygen molecules enter the chamber Oxygen Acceleration The molecules of oxygen are accelerated at the speed of sound as they pass through micro channels Figure 3. Boussignac CPAP Virtual Valve To Patient Oxygen Braking Establishment of a Virtual Valve The molecules of oxygen strike The collision of the molecules genera deflector which sends them ates a turbulence which transforms back to the central zone (mixthe speed into pressure ing zone) Used with permission by Vitaid. EMCC © 2011 Used with permission by Vitaid. 14 www.ebmedicine.net • Volume 1, Number 2 and family as well as defining the goals of NIV. For example, an end-stage COPD patient may wish to forego tracheal intubation but agree to NIV to ease the discomfort of dyspnea. trial was stopped early. The length of stay inhospital was also shorter in the bi-level NIV group. There was no change in survival rate. This study demonstrates the potential for bi-level NIV in blunt chest trauma. The mortality in each group was 1 patient (4%), which precludes an assessment of mortality benefit. Neuromuscular Respiratory Failure Miller and colleagues from the Quality Standards Subcommittee of the American College of Neurology published an evidence-based update of guidelines on the management of amyotrophic lateral sclerosis (ALS).10 They recommend that NIV be considered to treat respiratory insufficiency in ALS, both to lengthen survival and to slow the rate of forced vital capacity decline. They give this recommendation a Level B based upon 1 Class I study and 3 Class III studies. Bourke and colleagues, who conducted the Class I study,54 randomized ALS patients to either bi-level NIV at a mean 15 cm H2O IPAP and mean 4 cm H2O EPAP compared with standard care. Noninvasive ventilation was associated with a survival benefit of 205 days among patients with ALS and good bulbar function but not in ALS patients with poor bulbar function. Seneviratne and colleagues studied a retrospective cohort of 52 patients who presented with myasthenic crisis and were admitted to the ICU.55 Fourteen (58%) of the 24 patients initially given bilevel NIV (mean maximal IPAP/EPAP was 15/4 cm H2O) successfully avoided tracheal intubation. In general, there is limited evidence of the efficacy of NIV in patients with neuromuscular respiratory failure. A cautious trial may be helpful in either ALS (with good bulbar function) or myasthenic crisis. Cystic Fibrosis Moran and colleagues addressed the use of NIV in cystic fibrosis in a Cochrane review.58 Their review included many small studies that examined outcomes such as clearance of secretions and sleep latency. At present, there is insufficient evidence to suggest that NIV would be helpful in cystic fibrosis patients who present to the ED, although NIV has been used with good effect in other settings. Controversies/Cutting Edge Sedation In The Anxious Patient Sedation of a patient in respiratory distress is a double-edged sword. The benefit is that the patient may become more cooperative. The risk is that they may decline due to the underlying respiratory insult and need for urgent intubation. A few studies have shown that some agents may benefit the anxious patient in whom an NIV trial is attempted. Rocco and colleagues studied 36 patients with hypoxemic ARF who were not tolerating NIV and who received remifentanil.59 Twenty-two (61%) patients were able to continue the NIV and 14 (29%) required intubation. Constantin and colleagues performed a similar study using remifentanil in patients who were not able to tolerate NIV.60 For patients still not sufficiently sedated, they added propofol. Twelve of 13 patients were able to avoid intubation. The sedative dexmedetomidine has also shown promise. Akada and colleagues administered dexmedetomidine to 10 ICU patients who were agitated while receiving NIV for ARF.61 All patients were successfully weaned from NIV with no intubations and no clinically recognized episodes of aspiration. Acute Chest Syndrome In Sickle Cell Patients In a pilot study, Fartoukh and colleagues randomized 67 patients with symptoms suggestive of acute chest syndrome to either standard oxygen therapy or bi-level NIV with 12 cm H2O IPAP and 5 cm H2O EPAP.56 There was no improvement in the primary outcome of hypoxemia at day 3. Neither was there a decrease in pain, transfusions, or length of hospital stay. At this time, NIV cannot be recommended for acute chest syndrome in sickle cell patients. Noninvasive Ventilation For Preoxygenation During Tracheal Intubation Futier and colleagues randomized 66 morbidly obese patients undergoing preoxygenation for tracheal intubation.62 They compared 5 minutes of spontaneous breathing of 100% O2 with 2 types of NIV. The first intervention group received bi-level NIV with no more than 18 cm H2O IPAP and 6-8 cm H2O EPAP. The other NIV group received these settings plus a recruitment maneuver of 40 cm H2O for 40 seconds immediately following tracheal intubation. At the end of preoxygenation, PaO2 was higher in both NIV groups compared with conventional preoxygenation. Delay and colleagues randomized morbidly obese patients needing tracheal intubation Blunt Chest Trauma Hernandez and colleagues studied 50 patients admitted to the ICU within 48 hours of blunt thoracic trauma whose PaO2/FiO2 ratio remained below 200 for more than 8 hours on high flow oxygen.57 Most patients in this study developed ARF secondary to lung contusion. Bi-level NIV was applied at 10 to 12 cm H2O IPAP and 6 cm H2O EPAP, adjusting IPAP upwards by 2 cm H2O increments and EPAP at 1 cm H2O increments as needed to maintain oxygenation and inspiratory volumes. The intubation rate was higher in the oxygen-only group: 40% compared to 12% in the bi-level NIV group. For this reason, the www.ebmedicine.net • Volume 1, Number 2 15 EMCC © 2011 Summary preoxygenation using either spontaneous breathing of O2 by mask or NIV with 14 cm H2O IPAP and 6 cm H2O EPAP.27 Patients in the NIV group showed superior preoxygenation and did so more rapidly than the conventional O2 group. Jaber and colleagues examined NIV as part of an intubation care bundle.63 Noninvasive ventilation was given as pressure support of 5 to 15 cm H2O (specific IPAP and EPAP levels were not provided). They found a significant decrease in life-threatening complications at 1 hour post intubation: 21% in the bundled care intervention versus 34% in the pre-bundled care intervention. How much of that improvement in complication rate was due to NIV is unclear. Weingart provides a useful review on the topic of issues surrounding preoxygenation and proposes the use of NIV and ketamine to preoxygenate patients with tenuous oxygenation status, an approach he calls “delayed sequence intubation.”64 Noninvasive ventilation is a valuable tool that should be considered for patients who present to the ED in respiratory failure. While there is strong evidence for improved outcomes using NIV in certain subtypes of ARF, one should avoid using NIV for patients in whom it is absolutely contraindicated. Potential problems will usually become apparent in the first 60 minutes of applying NIV. Any patient who deteriorates clinically must be rescued with a definitive airway intervention. Case Conclusion The respiratory therapist recommended CPAP at 10 cm H2O. The oxygen saturation rose from the high 60s to the high 80s, and the patient was no longer diaphoretic. You placed a large bore peripheral IV, collected blood, and administered IV furosemide and nitroglycerin. You sent off a venous blood gas to follow the pH and PCO2. These returned as pH = 7.20 and PCO2 = 60. Based on the landmark studies by Kelly and colleagues - having kept in mind that they studied patients with acute COPD you repeated the venous blood gas and noted that the pH had risen by 0.10 to 7.30, and the PCO2 had dropped to 50. While the venous PCO2 result may not have correlated well with arterial PCO2, you felt confident that the pH was going in the right direction. The patient was no longer diaphoretic and even smiled for the first time. Chest radiograph confirmed acutely decompensated heart failure, and you felt satisfied that this patient would not need tracheal intubation. At least not for now… Noninvasive Ventilation As An Adjunct To Procedural Sedation The maintenance of a patent airway and preservation of spontaneous respiration is what distinguishes deep sedation from general anesthesia. However, significant relaxation of the muscles of the upper airway may occur, resulting in upper airway obstruction. Though only described in a case report, NIV may be a useful adjunct in supporting effective ventilation during procedural sedation. Must-Do Markers Of Quality ED Critical Care • Be prepared – a protocol in partnership with respiratory therapy is needed. • Start NIV early in eligible patients – it may increase chances for a good outcome. • Reassure the patient – NIV may be frightening to an already anxious patient. • Use sedation/analgesia with extreme care. • Have definitive airway equipment ready in case the patient deteriorates. • Venous blood gas pH correlates well with arterial pH and may be followed as an objective marker of improved ventilation. References Evidence-based medicine requires a critical ap praisal of the literature based upon study methodol ogy and number of subjects. Not all references are equally robust. The findings of a large, prospective, randomized, and blinded trial should carry more weight than a case report. To help the reader judge the strength of each reference, pertinent information about the study, such as the type of study and the number of patients in the study, are included in bold type following the reference, where available. In addition, the most informative references cited in this paper, as determined by the authors, are noted by an asterisk (*) next to the number of the reference. Disposition The disposition of patients who require NIV is complex. Unless the patient uses NIV at home, discharging them home may not be possible or desirable. For patients who need admission, there will be those who demonstrate a real improvement clinically and could be admitted to a regular ward, although institutional protocols will vary. Patients who still demonstrate insufficient clinical improvement should be evaluated for ICU admission, as many may eventually require tracheal intubation. EMCC © 2011 1. Soroksky A, Klinowski E, Ilgyev E, et al. Noninvasive positive pressure ventilation in acute asthmatic attack. Eur Respir Rev. 2010;19(115):39-45. (Review; 58 references) 2.* Pingleton SK. Complications of acute respiratory failure. Am Rev Respir Dis. 1988;137(6):1463-1493. (Review; 420 references) 3. Deutschman CS, Wilton P, Sinow J, et al. Paranasal sinusitis associated with nasotracheal intubation: a frequently 16 www.ebmedicine.net • Volume 1, Number 2 4.* 5. 6.* 7. 8.* 9. 10. 11. 12.* 13. 14.* 15.* 16.* 17.* unrecognized and treatable source of sepsis. Crit Care Med. 1986;14(2):111-114. 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(Nonrandomized; 24 patients who served as their own controls) Silvers SM, Howell JM, Kosowksy JM, et al. Clinical Policy: Critical Issues in the Evaluation and Management of Adult Patients Presenting to the Emergency Department with Acute Heart Failure Syndromes. Ann Emerg Med. 2007;49(5):627-669. (Evidence-based review; 84 references) Roberts CM, Brown JL, Reinhardt AK, et al. Non-invasive ventilation in chronic obstructive pulmonary disease: management of acute type 2 respiratory failure. Clin Med. 2008;8(5):517-521. (Concise guideline from the UK National Institute for Health and Clinical Evidence [NICE]) Miller RG, Jackson CE, Kasarskis EJ, et al. Practice parameter update: The care of the patient with amyotrophic lateral sclerosis: multidisciplinary care, symptom management, and cognitive/behavioral impairment (an evidence-based review): report of the Quality Standards Subcommittee of the American Academy of Neurology. Neurology. 2009;73(15):1218-1226. 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(Randomized; 27 patients) 35.* Bellone A, Monari A, Cortellaro F, et al. Myocardial infarction rate in acute pulmonary edema: noninvasive pressure support ventilation versus continuous positive airway pressure. Crit Care Med. 2004;32(9):1860-1865. (Randomized; 46 patients) 36.* Carron M, Freo U, Zorzi M, et al. Predictors of failure of noninvasive ventilation in patients with severe community-acquired pneumonia. J Crit Care. 2010; 25(3):540.e9-14. (Cohort; 64 patients) 37.* Confalionieri M, Calderini E, Terraciano S, et al. Noninvasive ventilation for treating acute respiratory failure in AIDS patients with Pneumocystis carinii pneumonia. Intensive Care Med. 2002;28(9):1233-1238. (Case-control; 48 patients) 38. Scala R, Naldi M. Ventilators for noninvasive ventilation to treat acute respiratory failure. Respir Care. 2008;53(8):10541080. (Review; 140 references) 39.* Schönhofer B, Sortor-Leger S. Equipment needs for noninvasive mechanical ventilation. Eur Respir J. 2002;20(4):10291036. (Review; 57 references) 40.* Yanez LJ, Yunge M, Emilfork M, et al. A prospective, randomized, controlled trial of noninvasive ventilation in pediatric acute respiratory failure. Pediatric Crit Care Med. 2008;9(5):484-489. (Randomized trial; 50 pediatric patients) 41. Kwok H, McCormack J, Cece R, et al. Controlled trial of oronasal versus nasal mask ventilation in the treatment of acute respiratory failure. Crit Care Med. 2003;31(2):468-473. (Randomized; 72 patients) 42. Girault C, Briel A, Benichou J, et al. Interface strategy during noninvasive positive pressure ventilation for hypercapnic acute respiratory failure. Crit Care Med. 2009;37(1):124-131. (Randomized; 90 patients) 43.* Cuvelier A, Pujol W, Pramil S, et al. Cephalic versus oronasal mask for noninvasive ventilation in acute hypercapnic respiratory failure. Intensive Care Med. 2009;35(3):519-526. (Randomized; 34 patients) 44. Conti G, Cavaliere F, Costa R, et al. Noninvasive positivepressure ventilation with different interfaces in patients with respiratory failure after abdominal surgery: a matched-control study. Respir Care. 2007;52(11):1463-1471. (Matched case control; 25 patients) 45.* Rocco M, Dell’Utri D, Morelli A, et al. Noninvasive ventilation by helmet or face mask in immunocompromised patients: a case-control study. Chest. 2004;126(5):1508-1515. (Randomized; 38 patients) 46.* Gillies ID, Morgan M, Sykes MK, et al. The nature and incidence of complications of peripheral arterial puncture. Anaesthesia. 1979;34(5):506-509. (Observational; 839 patients) 47.* Lim BL, Kelly AM. A meta-analysis on the utility of peripheral venous blood gas analyses in exacerbations of chronic obstructive pulmonary disease in the emergency department. Eur J Emerg Med. 2010;17(5):246-248. (Meta-analysis; 6 studies) 48.* Kelly AM, Klim S. Agreement between arterial and transcutaneous PCO2 in patients undergoing non-invasive ventilation. Respir Med. 2011;105(2):226-229. (Clinical trial; 46 patients) 49. Gay PC. Complications of noninvasive ventilation in acute care. Respir Care. 2009;54(2):246-257. (Review; 56 references) 50. Agarwal R, Aggarwal AN, Gupta D. Role of noninvasive ventilation in acute lung injury/acute respiratory distress syndrome: a proportion meta-analysis. Respir Care. 2010;55(12):1653-1660. (Meta-analysis; 13 studies, 540 patients) 51. Levy M, Tanios MA, Nelson D, et al. Outcomes of patients with do-not-intubate orders treated with noninvasive ven- EMCC © 2011 52. 53. 54.* 55.* 56. 57. 58. 59. 60. 61. 62. 63. 64. 18 tilation. Crit Care Med. 2004;32(10):2002-2007. (Multi-center cohort; 114 patients) Bulow HH, Thorsager B. Non-invasive ventilation in donot-intubate patients: five-year follow-up on a two-year prospective, consecutive cohort study. Acta anaesthesiol Scand. 2009;53(9):1153-1157. (Retrospective; 38 patients) Curtis JR, Cook DJ, Sinuff T, et al. Noninvasive positive pressure ventilation in critical and palliative care settings: understanding the goals of therapy. Crit Care Med. 2007;35(3):932939. (Consensus document, Task Force recommendation) Bourke SC, Tomlinson M, Williams TL, et al. Effects of noninvasive ventilation on survival and quality of life in patients with amyotrophic lateral sclerosis: a randomised controlled trial. Lancet Neurol. 2006;5(2):140-147. (Randomized trial; 92 patients) Seneviratne J, Mandrekar J, Wijdicks EF, et al. Noninvasive ventilation in myasthenic crisis. Arch Neurol. 2008;65(1):5458. (Retrospective cohort; 52 patients) Fartoukh M, Lefort Y, Habibi A, et al. Early intermittent noninvasive ventilation for acute chest syndrome in adults with sickle cell disease: a pilot study. Intensive Care Med. 2010;36(8):1355-1362. (Randomized trial; 67 patients) Hernandez G, Fernandez R, Lopez-Reina P, et al. Noninvasive ventilation reduces intubation in chest trauma-related hypoxemia. Chest. 2010;137(1):74-80. (Randomized trial; 50 patients with early termination) Moran F, Bradley JM, Piper AJ. Non-invasive ventilation for cystic fibrosis. Cochrane Database Syst Rev. 2009;21(1):CD002769. (Cochrane meta-analysis; 15 trials, 106 patients) Rocco M, Conti G, Alessandri E, et al. Rescue treatment for noninvasive ventilation failure due to interface intolerance with remifentanil analgosedation: a pilot study. Intensive Care Med. 2010;36(12):2060-2065. (Clinical trial; 36 patients) Constantin JM, Schneider E, Cayot-Constanti S, et al. Remifentanil-based sedation to treat noninvasive ventilation failure: a preliminary study. Intensive Care Med. 2007;33(1):8287. (Clinical trial; 13 patients) Akada S, Takeda S, Yoshida Y, et al. The efficacy of dexmedetomidine in patients with noninvasive ventilation: a preliminary study. Anesth Analg. 2008;107(1):167-170. (Clinical trial; 10 patients) Futier E, Constantin JM, Pelosi P, et al. Noninvasive Ventilation and Alveolar Recruitment Maneuver Improve Respiratory Function during and after Intubation of Morbidly Obese Patients: A Randomized Controlled Study. Anesthesiology. 2011;114(6):1354-1363. (Randomized trial; 66 patients) Jaber S, Jung B, Corne P, et al. An intervention to decrease complications related to endotracheal intubation in the intensive care unit: a prospective, multiple-center study. Intensive Care Med. 2010;36(2):248-255. (Clinical trial; 244 patients) Weingart SD. Preoxygenation, Reoxygenation, and Delayed Sequence Intubation in the Emergency Department. J Emerg Med. 2010. [Epub ahead of print]. (Review; 5 references) www.ebmedicine.net • Volume 1, Number 2 Limited-Time Discount For Our Valued Customers: Save 70% on ED Overcrowding Solutions! The editors of ED Overcrowding Solutions scrutinize dozens of sources every day to find the most novel solutions available and then ask the hard questions you would ask yourself. 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