Table of Contents

 

Placing a patient on a ventilator in the ED presents an emergency clinician with an array of decisions regarding the initial approach and ventilator settings. While ventilation can be a life-saving intervention, there are primary principles involving pressure settings, PEEP, flow rate, tidal volume, and blood gas.

Volume assist-control ventilation versus pressure-regulated volume control ventilation: what are the circumstances for each?

How does predicted body weight dictate the tidal volume?

How will adjusting the inspirator-expiratory ratio (I:E) affect patient comfort?

Based on current evidence, what are the circumstances where patients should not be given supplemental oxygen?

How will the obstructive physiology of COPD and asthma affect ventilator settings? What are the particular concerns you should watch for?

For patients with acute respiratory distress syndrome, what does the evidence say on higher-PEEP or lower-PEEP strategies, and what are the indications for paralytics, recruitment maneuvers, and proning?

How is ARDS in patients with coronavirus disease infection different from what has been seen before? Is there good evidence on how to manage these patients?

What are the best ways to monitor and manage ventilated patients: pulse oximetry, waveform capnography, assessing for breath-stacking?

1. Abstract
2. Case Presentations
3. Introduction
4. Critical Appraisal of the Literature
5. Prehospital Care
6. Approach to Initial Ventilator Settings
   1. Modes of Ventilation
      1. Volume Assist-Control Mode
      2. Pressure-Regulated Volume Control
         • Tidal Volume
         • Inspiratory Peak Flow Rate (Inspiratory Time)
         • Respiratory Rate
         • Positive End-Expiratory Pressure
         • Fraction of Inspired Oxygen
         • Inspiratory to Expiratory Time (I:E Ratio)
   2. Other Modes of Ventilation
      1. Synchronous Intermittent Mandatory Ventilation With Pressure Support
      2. Airway Pressure Release Ventilation
   3. Oxygen Delivery
7. Approach to Specific Types of Patients Requiring Mechanical Ventilation
   1. Obstructive Physiology (Asthma and Chronic Obstructive Pulmonary Disease)
   2. Acute Respiratory Distress Syndrome
      1. Use of Paralytic Agents in ARDS
      2. Recruitment Maneuvers in ARDS
      3. Prone Positioning in ARDS
      4. Nontraditional Ventilator Settings in ARDS
   3. ARDS and Coronavirus Disease Infection
   4. Severe Metabolic Acidosis
8. Monitoring and Making Changes to the Ventilator Settings
   1. Arterial Blood Gas
   2. Pulse Oximetry
   3. Waveform Capnography
   4. Ventilator Pressures
   5. Assessing for Breath-Stacking
9. Special Populations
   1. Obese Patients
10. Controversies and Cutting Edge
    1. Extracorporeal Membrane Oxygenation
    2. Esophageal Pressure Monitoring
11. Summary
12. Risk Management Pitfalls in Mechanical Ventilation in the Emergency Department
13. Case Conclusions
14. Clinical Pathway for Ventilator Management in the Emergency Department
15. Tables and Figures
    1. Table 1. Predicted Body Weight for Females of Various Heights and Associated Tidal Volumes
    2. Table 2. Predicted Body Weight for Males of Various Heights and Associated Tidal Volumes
    3. Table 3. Examples of Initial Ventilator Settings for Obstructive Physiology (Asthma/COPD), Volume Assist-Control Mode
    4. Table 4. Examples of Initial Ventilator Settings for ARDS Patients, Volume Assist-Control Mode
    5. Table 5. ARDSNet Trial FiO2/PEEP (cm H2O) Protocol, Lower Versus Higher Strategy
    6. Table 6. Example of Initial Ventilator Settings for Patients With a Severe Metabolic Acidosis, Volume Assist-Control Mode
    7. Table 7. Scenarios and Their Associated Peak Pressure and Plateau Pressure Changes
    8. Figure 1. Normal Output of Waveform Capnography
    9. Figure 2. Waveform Capnography Demonstrating Bronchospasm
    10. Figure 3. Peak Versus Plateau Pressure
    11. Figure 4. Graph of Flow Versus Time
    12. Figure 5. An Expiratory Hold Demonstrating Auto-PEEP (Pressure Above the Set PEEP)
16. References

Abstract

There are a variety of ventilator options available to the emergency clinician, and decisions on choosing optimal settings will depend on the clinical circumstances. Understanding the latest literature in ventilator management can improve patient outcomes by ensuring optimal oxygenation and ventilation and reducing the potential for ventilator-induced lung injury. This article reviews the most appropriate ventilator settings for a variety of conditions in intubated adult patients presenting to the emergency department, and gives recommendations on monitoring the ventilated patient and making ventilator adjustments. An update on managing COVID-19-associated acute respiratory distress syndrome is also included.

Case Presentations

Your very first patient is wheeled into the resuscitation bay as you are walking through the doors to start your shift. A 30-year-old woman (5’3” tall, 120 kg) is in respiratory failure from an acute asthma exacerbation and requires a crash airway despite your best efforts to avoid endotracheal intubation. After intubation, the respiratory therapist asks for initial ventilator settings. You recall that these patients are at risk for breath-stacking and you start to devise your ventilator strategy...

Halfway into your shift, a 21-year-old man with type 1 diabetes mellitus presents, obtunded, with Kussmaul breathing. You start your standard resuscitation, but the patient requires endotracheal intubation, as he is unresponsive to all stimuli. You consider whether you should use the bag-valve mask during the apneic period during rapid sequence intubation...

At the end of your shift, a 50-year-old man who was seen 2 days ago at an outside hospital for pneumonia now presents in severe hypoxemic respiratory failure. The patient is intubated, but is difficult to oxygenate. A chest x-ray demonstrates good endotracheal tube placement, but bilateral diffuse infiltrates. You suspect acute respiratory distress syndrome and start thinking about the strategies you will use if your initial approach is ineffective in oxygenating the patient...

Introduction

When it becomes necessary to place a patient on a ventilator in the emergency department (ED), there are many options regarding ventilator settings, and understanding the strategies for each clinical scenario can improve patient outcomes.^1,2 A pre/post study on a multifaceted ED-based mechanical ventilator protocol found that initiating best ventilator management practice in the ED decreased mortality, duration of ventilation, and hospital length of stay.³

Fundamental to successful airway management is the optimization of oxygenation and perfusion prior to intubation and placement on a ventilator, if possible; failure to do this has been associated with an increased risk of peri-intubation cardiac arrest.^4,5 Most cases of intubation-related cardiac arrest occur within 10 minutes of intubation.⁶

Because patients require mechanical ventilation for a wide variety of conditions, the considerations and initial approach to ventilator management could be substantially different in different scenarios. This issue of Emergency Medicine Practice reviews general approaches to ventilator management, with a focus on specific conditions where a different approach to mechanical ventilation would be advantageous.

Critical Appraisal of the Literature

A literature search was performed using the PubMed Medical Subject Headings (MeSH) with key words respiratory distress syndrome (432 articles); ventilator-induced lung injury (72 articles); respiration, artificial (2528 articles); and ventilators, mechanical (66 articles) restricted to adults and trials in the past 10 years. Literature on randomized trials specific to the ED is relatively uncommon, as most are longitudinal studies performed in the intensive care unit (ICU). Many of the studies included patients who were enrolled in the ED, with the majority of the interventions carried out in the ICU. Nonetheless, there are supportive quasi-experimental (pre/post) and observational data with outcomes that mirror the randomized ICU-conducted trials. Therefore, it is reasonable to assume that the benefits found in the ICU ventilator trials are applicable to the ED population. Specific trials analyzing most individual components of ventilator management are lacking, except for trials regarding acute respiratory distress syndrome (ARDS), where literature is robust. All major trials on ventilator management were reviewed, as well as expert opinion articles regarding ED ventilator management.

Prehospital Care

If mechanical ventilation is within the scope of practice of the prehospital provider, the guidelines in this article apply. Most recent data show that hyperoxia in acutely ill medical patients is harmful, and expert recommendations advise following the same oxygenation guidelines in the prehospital setting as in the ED/inpatient setting by generally avoiding hyperoxia. (See the “Oxygen Delivery” section.)

If using bag-valve mask (BVM) ventilation for hypoxia during transport, utilize a positive end-expiratory pressure (PEEP) valve to provide PEEP where it is necessary, as adjusting PEEP on a ventilator. A PEEP valve may be integrated with the BVM or it may be an optional add-on, and it typically allows for the application of 0 to 20 cm H₂O of PEEP. PEEP provides pressure to the airways at the end of expiration, which can increase alveolar patency and improve oxygenation, especially in areas of shunting. Shunting refers to areas where alveoli are being perfused but not being ventilated (eg, shunting due to alveolar fluid accumulation in pulmonary edema, alveolar hemorrhage, pneumonia, etc). PEEP can keep these alveoli patent and participating in gas exchange. Following the same recommendations for PEEP as discussed in ventilated patients in the following sections is appropriate.

Risk Management Pitfalls in Mechanical Ventilation in the Emergency Department

1. “The patient with ARDS had difficulty oxygenating, so I increased the tidal volume to 12 mL/ kg as my first intervention.”

Increased tidal volumes have been shown to increase mortality in ARDS. Using lung-protective lower tidal volume strategies is preferred, using the FiO₂ and PEEP to maintain appropriate oxygenation. If this fails, prone positioning and/or APRV should be considered.

4. “This patient with severe DKA coded 5 minutes after I intubated him. I don’t understand why, since I used normal ventilator settings.”

Patients with severe metabolic acidosis need adequate respiratory compensation by using a high minute ventilation. Patients who receive longer-acting paralytics (such as rocuronium), are initially unable to over-breathe the ventilator since they are still paralyzed. Taking away their respiratory compensation with a lower minute ventilation after intubation can cause a precipitous decline in pH and lead to cardiac arrest.

10. “My patient with asthma was intubated, and the PaCO₂ was 70 mm Hg, so I increased the respiratory rate to increase his minute ventilation to ‘blow off’ some CO₂.”

Patients with asthma are at high risk for breath-stacking, and the high PaCO₂ reflects poor air movement from severe bronchospasm. Increasing the respiratory rate indiscriminately in this case is likely to lead to breath-stacking, which is dangerous. Monitoring the patient for breath-stacking is critical prior to any increases in respiratory rate, and hypercapnia in this situation should be tolerated as long as the pH remains above 7.20 (permissive hypercapnia).

Tables and Figures

References

Evidence-based medicine requires a critical appraisal of the literature based upon study methodology 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 is included in bold type following the references, where available. In addition, the most informative references cited in this paper, as determined by the author, are highlighted.

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3. Fuller BM, Ferguson IT, Mohr NM, et al. Lung-protective ventilation initiated in the emergency department (LOV-ED): a quasi-experimental, before-after trial. Ann Emerg Med. 2017;70(3):406-418. (Quasi-experimental before-after study; 1192 patients)
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8. Weingart SD. Managing initial mechanical ventilation in the emergency department. Ann Emerg Med. 2016;68(5):614-617. (Expert opinion)
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11. Page D, Ablordeppey E, Wessman BT, et al. Emergency department hyperoxia is associated with increased mortality in mechanically ventilated patients: a cohort study. Crit Care. 2018;22(1):9. (Observational cohort study; 688 patients)
12. Chu DK, Kim LH, Young PJ, et al. Mortality and morbidity in acutely ill adults treated with liberal versus conservative oxygen therapy (IOTA): a systematic review and meta-analysis. Lancet. 2018;391(10131):1693-1705. (Systematic review and meta-analysis; 16,037 patients)
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15. Siemieniuk RAC, Chu DK, Kim LH, et al. Oxygen therapy for acutely ill medical patients: a clinical practice guideline. BMJ. 2018;363:k4169. (Clinical practice guideline)
16. Girardis M, Busani S, Damiani E, et al. Effect of conservative vs conventional oxygen therapy on mortality among patients in an intensive care unit: the Oxygen-ICU Randomized Clinical Trial. JAMA. 2016;316(15):1583-1589. (Randomized trial; 480 patients)
17. Barrot L, Asfar P, Mauny F, et al. Liberal or conservative oxygen therapy for acute respiratory distress syndrome. N Engl J Med. 2020;382(11):999-1008. (Randomized trial; 205 patients)
18. Marini JJ. Dynamic hyperinflation and auto-positive end-expiratory pressure: lessons learned over 30 years. Am J Respir Crit Care Med. 2011;184(7):756-762. (Expert opinion)
19. Hickling KG, Walsh J, Henderson S, et al. Low mortality rate in adult respiratory distress syndrome using low-volume, pressure-limited ventilation with permissive hypercapnia: a prospective study. Crit Care Med. 1994;22(10):1568-1578. (Prospective descriptive study; 53 patients with ARDS)
20. Ambrosino N, Foglio K, Rubini F, et al. Non-invasive mechanical ventilation in acute respiratory failure due to chronic obstructive pulmonary disease: correlates for success. Thorax. 1995;50(7):755-757. (Prospective cohort study; 47 patients)
21. Acute Respiratory Distress Syndrome Network, Brower RG, Matthay MA, et al. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. N Engl J Med. 2000;342(18):1301-1308. (Randomized controlled trial; 861 patients)
22. Brower RG, Lanken PN, MacIntyre N, et al. Higher versus lower positive end-expiratory pressures in patients with the acute respiratory distress syndrome. N Engl J Med. 2004;351(4):327-336. (Randomized controlled trial; 549 patients)
23. Briel M, Meade M, Mercat A, et al. Higher vs lower positive end-expiratory pressure in patients with acute lung injury and acute respiratory distress syndrome: systematic review and meta-analysis. JAMA. 2010;303(9):865-873. (Systematic review and meta-analysis; 2299 patients)
24. van der Zee P, Gommers D. Recruitment maneuvers and higher PEEP, the so-called open lung concept, in patients with ARDS. Crit Care. 2019;23(1):73. (Review)
25. Papazian L, Forel JM, Gacouin A, et al. Neuromuscular blockers in early acute respiratory distress syndrome. N Engl J Med. 2010;363(12):1107-1116. (Randomized controlled trial; 340 patients)
26. National Heart Lung, and Blood Institute PETAL Clinical Trials Network, Moss M, Huang DT, et al. Early neuromuscular blockade in the acute respiratory distress syndrome. N Engl J Med. 2019; 380(21):1997-2008. (Randomized controlled trial; 1006 patients)
27. Writing Group for the Alveolar Recruitment for Acute Respiratory Distress Syndrome Trial Investigators, Cavalcanti AB, Suzumura EA, et al. Effect of lung recruitment and titrated positive end-expiratory pressure (PEEP) vs low PEEP on mortality in patients with acute respiratory distress syndrome: a randomized clinical trial. JAMA. 2017;318(14):1335-1345. (Randomized controlled trial; 1010 patients)
28. Gattinoni L, Taccone P, Carlesso E, et al. Prone position in acute respiratory distress syndrome. Rationale, indications, and limits. Am J Respir Crit Care Med. 2013;188(11):1286-1293. (Review)
29. Guerin C, Reignier J, Richard JC, et al. Prone positioning in severe acute respiratory distress syndrome. N Engl J Med. 2013;368(23):2159-2168. (Randomized controlled trial; 466 patients)
30. Munshi L, Del Sorbo L, Adhikari NKJ, et al. Prone position for acute respiratory distress syndrome. A systematic review and meta-analysis. Ann Am Thorac Soc. 2017;14(Supplement_4):S280-S288. (Systematic review and meta-analysis; 2129 patients)
31. Zhou Y, Jin X, Lv Y, et al. Early application of airway pressure release ventilation may reduce the duration of mechanical ventilation in acute respiratory distress syndrome. Intensive Care Med. 2017;43(11):1648-1659. (Randomized controlled trial; 138 patients)
32. Ferguson ND, Cook DJ, Guyatt GH, et al. High-frequency oscillation in early acute respiratory distress syndrome. N Engl J Med. 2013;368(9):795-805. (Randomized controlled trial; 548 patients)
33. Young D, Lamb SE, Shah S, et al. High-frequency oscillation for acute respiratory distress syndrome. N Engl J Med. 2013;368(9):806-813. (Randomized controlled trial; 795 patients)
34. Goligher EC, Munshi L, Adhikari NKJ, et al. High-frequency oscillation for adult patients with acute respiratory distress syndrome. A systematic review and meta-analysis. Ann Am Thorac Soc. 2017;14(Supplement_4):S289-S296. (Systematic review and meta-analysis; 1715 patients)
35. Meade MO, Young D, Hanna S, et al. Severity of hypoxemia and effect of high-frequency oscillatory ventilation in acute respiratory distress syndrome. Am J Respir Crit Care Med. 2017;196(6):727-733. (Meta-analysis; 4 HFOV trials, 1552 patients with ARDS)
36. Marini JJ. Dealing With the CARDS of COVID-19. Crit Care Med. 2020, May 13. Online ahead of print. (Expert opinion)
37. Marini JJ, Gattinoni L. Management of COVID-19 respiratory distress. JAMA. 2020, Apr 24. Online ahead of print. (Expert opinion)
38. Gattinoni L, Chiumello D, Caironi P, et al. COVID-19 pneumonia: different respiratory treatments for different phenotypes? Intensive Care Med. 2020, Apr 14. Online ahead of print. (Expert opinion)
39. Elharrar X, Trigui Y, Dols AM, et al. Use of prone positioning in nonintubated patients with COVID-19 and hypoxemic acute respiratory failure. JAMA. 2020, May 15;e208255. Online ahead of print. (Prospective, single-center before-after study; 24 patients)
40. Sartini C, Tresoldi M, Scarpellini P, et al. Respiratory parameters in patients with COVID-19 after using noninvasive ventilation in the prone position outside the intensive care unit. JAMA. 2020, May 15;e207861. Online ahead of print. (1-day cross-sectional before/after study; 15 patients)
41. Pan C, Chen L, Lu C, et al. Lung recruitability in COVID-19-associated acute respiratory distress syndrome: a single-center observational study. Am J Respir Crit Care Med. 2020;201(10):1294-1297. (Single-center observational trial; 12 patients)
42. Casey JD, Janz DR, Russell DW, et al. Bag-mask ventilation during tracheal intubation of critically ill adults. N Engl J Med. 2019;380(9):811-821. (Randomized controlled trial; 401 patients)
43. Lui CT, Poon KM, Tsui KL. Abrupt rise of end tidal carbon dioxide level was a specific but non-sensitive marker of return of spontaneous circulation in patient with out-of-hospital cardiac arrest. Resuscitation. 2016;104:53-58. (Cross sectional study; 2 EDs)
44. Paiva EF, Paxton JH, O’Neil BJ. The use of end-tidal carbon dioxide (EtCO₂) measurement to guide management of cardiac arrest: a systematic review. Resuscitation. 2018;123:1-7. (Systematic review; 17 studies, 6198 patients; 5 studies in meta-analysis)
45. Gong MN, Bajwa EK, Thompson BT, et al. Body mass index is associated with the development of acute respiratory distress syndrome. Thorax. 2010;65(1):44-50. (Cohort study; 1795 patients)
46. Zhao Y, Li Z, Yang T, et al. Is body mass index associated with outcomes of mechanically ventilated adult patients in intensive critical units? A systematic review and meta-analysis. PLoS One. 2018;13(6):e0198669. (Systematic review and meta-analysis; 199,421 patients)
47. Ni YN, Luo J, Yu H, et al. Can body mass index predict clinical outcomes for patients with acute lung injury/acute respiratory distress syndrome? A meta-analysis. Crit Care. 2017;21(1):36. (Systematic review and meta-analysis; 6268 patients)
48. De Jong A, Verzilli D, Jaber S. ARDS in obese patients: specificities and management. Crit Care. 2019;23(1):74. (Review)
49. Combes A, Hajage D, Capellier G, et al. Extracorporeal membrane oxygenation for severe acute respiratory distress syndrome. N Engl J Med. 2018;378(21):1965-1975. (Randomized controlled trial; 249 patients)
50. Talmor D, Sarge T, Malhotra A, et al. Mechanical ventilation guided by esophageal pressure in acute lung injury. N Engl J Med. 2008;359(20):2095-2104. (Randomized controlled trial; 61 patients)
51. Beitler JR, Sarge T, Banner-Goodspeed VM, et al. Effect of titrating positive end-expiratory pressure (PEEP) with an esophageal pressure-guided strategy vs an empirical high PEEP-FiO₂ strategy on death and days free from mechanical ventilation among patients with acute respiratory distress syndrome: a randomized clinical trial. JAMA. 2019;321(9):846-857. (Randomized controlled trial; 200 patients)

Points and Pearls Excerpt

• Initiating best-practice ventilation management in the ED has been shown to decrease duration of ventilation, hospital stay, and mortality.
• Failure to optimize oxygenation and perfusion prior to intubation and mechanical ventilation has been associated with an increased risk of peri-intubation cardiac arrest.
• Hyperoxia in acutely ill patients is harmful. Large reviews have demonstrated an increase in mortality with a liberal oxygenation strategy compared to a more conservative approach.
• Start the newly mechanically ventilated patient at 100% FiO₂, but then rapidly titrate down the oxygen until the oxygen saturation is 93%-96%.

Most Important References

• Weingart SD. Managing initial mechanical ventilation in the emergency department. Ann Emerg Med. 2016;68(5):614-617. (Expert opinion) 
• Siemieniuk RAC, Chu DK, Kim LH, et al. Oxygen therapy for acutely ill medical patients: a clinical practice guideline. BJM. 2018;363:K4169. (Clinical practice guideline) 
• Guerin C, Reignier J, Richard JC, et al. Prone positioning in severe acute respiratory distress syndrome. N Engl J Med. 2013;368(23):2159-2168. (Randomized controlled trial; 466 patients) 
• Casey JD, Janz DR, Russell DW, et al. Bag-mask ventilation during tracheal intubation of critically ill adults. N Engl J Med. 2019;380(9):811-821. (Randomized controlled trial; 401 patients) 
• Combes A, Hajage D, Capellier G, et al. Extracorporeal membrane oxygenation for severe acute respiratory distress syndrome. N Engl J Med. 2018;378(21):1965-1975. (Randomized controlled trial; 249 patients)