CPAP in the Prehospital Setting

It’s the middle of your 24-hour shift, and you get a call: “Male found down.” That’s it—nothing more. You arrive to find a 20ish male who is barely breathing after taking an unknown substance. He was dropped off by some friends at his girlfriend’s house. 

You and your partner start bagging him and decide to give naloxone. The patient starts breathing on his own but still has apneic periods. You place him on a 15-liter nonrebreather facemask, but you think he might need something more. You consider putting him on a continuous positive airway pressure (CPAP) machine but are concerned his altered mental status might make the attempt futile. 

This article will discuss the use of CPAP in the prehospital setting: when it can be used, when it should be avoided, and special populations. 

Continuous positive airway pressure is a type of positive airway pressure in which airflow is conducted into the airways at a constant pressure that stents them open. Positive end-expiratory pressure (PEEP) is the pressure in the alveoli above the normal atmospheric pressure at the end of expiration. CPAP allows the delivery of PEEP at a set steady pressure throughout inhalation and exhalation. CPAP is similar to another concept, bilevel positive airway pressure (BiPAP). BiPAP delivers differing pressures based on whether the patient is breathing in or out. Using CPAP maintains PEEP, which results in decreased atelectasis, increases surface area on the alveolus, improves V/Q matching, and thereby improves oxygenation.¹ 

There are times when a patient requires more breathing assistance than can be provided by a simple nasal cannula or even nonrebreather, but intubation might not be the best option. Common situations where CPAP can help include heart failure, chronic obstructive pulmonary disease, pneumonia, blunt chest wall trauma including flail chest, toxic inhalations, obese patients, near drownings, neonatal patients with respiratory distress, and patients with do-not-resuscitate status.² 

Using CPAP in the above situations offers a number of advantages. The most obvious is that it allows for increased respiratory support compared to nasal cannula or nonrebreather, without an invasive procedure or additional medications. If you do not have access to CPAP and intubation is your only or best option in some of the above situations, you put an already at-risk patient at further risk: If you are intubating because you cannot oxygenate, you place the patient at risk of further hypoxia prior to intubation, not to mention risk of being unable to ventilate a paralyzed patient if using a rapid sequence intubation protocol. 

Yet there are situations where using CPAP would put the patient at unnecessary risk or is contraindicated. Conditions where CPAP should be avoided include impaired coughing or swallowing, depressed sensorium and lethargy, gastrointestinal bleeding with intractable emesis and/or uncontrollable bleeding, status epilepticus, anaphylaxis, severe facial burns, tracheal injuries, maxillofacial or basilar skull fractures, and external masses compressing the airway. In general, if a provider is worried about the patient’s ability to maintain their airway, whether from mechanical/anatomical complications or mental status changes, they should avoid CPAP. In particular, a patient with a high aspiration risk could be further injured by the use of CPAP, not only by the potential for hypoxia as a result of inappropriate oxygen delivery but from the risk of aspiration pneumonitis.² 

CPAP is useful in a variety of situations, but one has to be careful in patients who are not able to tolerate the device. If a patient is anxious or continuously removing the device due to discomfort, CPAP might not be the best modality for them. CPAP requires the user to participate to work best—the patient has to be able to initiate her/his own breaths. 

COVID-19

There is a discussion to be had about populations for whom CPAP might have special considerations, but let’s focus for now just on COVID-19. Every day the data on COVID-19 is being revised, and it would be both impossible and impractical to give specific recommendations; yet certain considerations can be addressed. The CDC has put out a video showing how intubation is an aerosolizing procedure, and similar examples have been cited for CPAP as well. Approach patients you suspect have COVID-19 cautiously—and ideally only have CPAP used when viral filters are available. Wear N95 masks for every patient encounter, regardless of whether the patient has a respiratory complaint. 

With these safety considerations in mind, let’s discuss some of the preliminary data on CPAP in COVID-19. In an Italian ED during February and March of 2020, patients with respiratory distress due to presumed COVID were given ventilatory support, in most cases via CPAP. Authors found while many of those in severe distress were ultimately intubated, CPAP was a very useful bridging mechanism.³ Another study from Italy found that of patients who presented to an emergency department and were subsequently placed on CPAP, 83% recovered with CPAP alone, without the need for intubation.⁴ While this was a select population, it does show the benefit CPAP can have for COVID-19 patients. 

The American College of Emergency Physicians has published guidelines on airway management of suspected and confirmed COVID-19 patients. These first and foremost emphasize the importance of proper personal protective equipment with any patient with a respiratory complaint. They also discuss the benefit of using bag-valve masks and high-flow oxygen as well as CPAP to avoid intubation but recommend inline viral filters as well as the above PPE alongside end-tidal CO₂ placed with the CPAP.⁵  

The ACEP guidelines highlight the importance of doing a risk-benefit analysis when using CPAP in suspected COVID-19 patients.⁵ If there is serious concern about their ability to protect their airway during transport, consider intubation. 

Should BLS Use It?

In conjunction with the above discussion, it is worthwhile to discuss the use of CPAP by BLS crews. CPAP has been shown beneficial in many scenarios, including acute pulmonary edema as well as COPD and asthma, and requires less operator expertise than intubation. Yet there is debate to whether BLS crews should be allowed to utilize CPAP.

This debate is very relevant, because more than half of all EMS agencies today are licensed at the EMT-Basic level.⁶ An observational study in Delaware looked at 74 patients who received CPAP by BLS crews; of those patients who were placed on CPAP by BLS providers, all had respiratory status appropriately monitored and documented during transport. This study suggests that BLS crews can safely and effectively utilize CPAP in the prehospital setting.⁷  

Case Reviews

With the above considerations in mind, let’s review our initial case. In this situation we have a young patient who has received naloxone and is beginning to wake up with occasional apneic periods. While opioid overdose patients do have altered mental status and might have some difficulty participating in providers’ attempts to oxygenate and ventilate them, after response to naloxone these patients begin to breathe on their own, and CPAP can be used to bridge them until they are able to more fully participate in their own oxygenation. 

Consider another case: You and your partner respond to a call and find an 80-year-old female with past medical history of asthma and smoking, as well as prior myocardial infarction. When your partner checks her vital signs, you notice she has an oxygen saturation of 80% on room air. You place her on a nonrebreather, but her oxygen saturation only increases to 85%, and her respiratory rate is 45. You listen to her lungs and hear crackles/rales. Being the perceptive EMS provider you are, you decide to place her on CPAP, and her oxygen saturation increases to 90% and respiratory rate decreases to 28. This case is an ideal example of the benefits of CPAP in patients with heart failure exacerbation—something shown numerous times in the primary literature.⁸ 

You and your partner are having quite the day—first an opioid overdose and then a COPD/heart failure patient who both required CPAP to help with oxygenation!—and you grab some lunch with the hope the rest of your day will be more relaxed. While at lunch you get a call for a patient with known epilepsy having a seizure. You arrive to find the patient still seizing; the family thinks it’s been going on for about 15–20 minutes. You give the patient 10 mg of IM midazolam and he continues seizing, so you decide to give an additional dose of antiepileptic medication, but still without success. You check the patient’s oxygen saturation, which is at 70%. You quickly consider your options and decide to intubate. Your reasons for intubation instead of CPAP in this patient include concern for aspiration and inability of the patient to protect their own airway.⁹  

Conclusion

Let’s briefly summarize the key learning points:

• CPAP provides PEEP, which in turn stents open the airways; 
• CPAP can be used as a temporizing measure in patients who have respiratory distress but for whom intubation is not available or not indicated; 
• CPAP cannot be used in patients who are not initiating breaths on their own, have facial trauma or burns, or are otherwise not protecting their airway; 
• CPAP can be safely and effectively utilized by BLS providers. 

CPAP utilization in the prehospital setting has increased drastically in the last 10 years, and many providers are now familiar with the benefits of, indications for, and contraindications for its use.

References

1. Pinto VL, Sharma S. Continuous Positive Airway Pressure. StatPearls [Internet], www.ncbi.nlm.nih.gov/books/NBK482178/.

2. Schwerin DL, Goldstein S. EMS Prehospital CPAP Devices. StatPearls [Internet], www.ncbi.nlm.nih.gov/books/NBK470429.

3. Duca A, Memaj I, Zanardi F. Severity of respiratory failure and outcome of patients needing a ventilatory support in the emergency department during Italian novel coronavirus SARS-CoV2 outbreak: Preliminary data on the role of helmet CPAP and non-invasive positive pressure ventilation. E Clin Med, 2020 Jul 1; 24: 100419.

4. Brusasco C, Corradi F, Domenico AD, et al. Continuous positive airway pressure in Covid-19 patients with moderate-to-severe respiratory failure. Eur Resp J, 2020 Jan; 2002524.

5. American College of Emergency Physicians. ACEP COVID-19 Field Guide: Air Method Guidelines for the Care of Patients With Suspected or Confirmed COVID-19, www.acep.org/corona/covid-19-field-guide/ems/air-method-guidelines-for-the-care-of-patients-with-suspected-or-confirmed-covid-19.

6. National Highway Traffic Safety Administration. EMS System Demographics, www.ems.gov/pdf/National_EMS_Assessment_Demographics_2011.pdf.

7. Sahu N, Matthews P, Groner K, Papas MA, Megargel R. Observational Study on Safety of Prehospital BLS CPAP in Dyspnea. Prehosp Disaster Med, 2017 Dec; 32(6): 610–4.

8. Pang D, Keenan SP, Cook DJ, Sibbald WJ. The effect of positive pressure airway support on mortality and the need for intubation in cardiogenic pulmonary edema: a systematic review. Chest, 1998 Oct; 114(4): 1,185–92.

9. Vohra TT, Miller JB, Nicholas KS, et al. Endotracheal intubation in patients treated for prehospital status epilepticus. Neurocrit Care, 2015 Aug; 23(1): 33–43. 

Sidebar: Learn More About CPAP

For a more in-depth look at CPAP in the prehospital setting, check out these articles: 

• “EMS Prehospital CPAP Devices,” by Daniel Schwerin and Scott Goldstein, www.ncbi.nlm.nih.gov/books/NBK470429; 
• “Prehospital Noninvasive Ventilation for Acute Respiratory Failure: Systematic Review, Network Meta-Analysis, and Individual Patient Data Meta-Analysis,” by Steve Goodacre, et al., https://pubmed.ncbi.nlm.nih.gov/25269576; 
• “The Effect of Positive Pressure Airway Support on Mortality and the Need for Intubation in Cardiogenic Pulmonary Edema: a Systematic Review,” by David Pang, et al., https://pubmed.ncbi.nlm.nih.gov/9792593. 

Nathanael Smith, MD, is an emergency medicine resident at Washington University in St. Louis. He attended medical school at Meharry Medical College, Nashville, Tenn.

Hawnwan Philip Moy, MD, is an assistant medical director of the St. Louis City Fire Department and emergency medicine clinical instructor and core faculty in the EMS Section of the Division of Emergency Medicine at Washington University in St. Louis.