key: cord-0964929-wt7k9cwq
authors: Kedzierewicz, Romain; Derkenne, Clément; Fraudin, Adrien; Vanhaecke, Paola; Jouffroy, Romain; Jost, Daniel; Prunet, Bertrand
title: Logistical challenge with prehospital use of high-flow nasal oxygen therapy in COVID-19-induced respiratory distress: a case report
date: 2021-03-05
journal: J Emerg Med
DOI: 10.1016/j.jemermed.2021.03.006
sha: 6715488aa6d8c3732848245027eae15fa30e6249
doc_id: 964929
cord_uid: wt7k9cwq

BACKGROUND: Although commonly used inside hospitals, no previous case report has been published on high-flow nasal oxygen (HFNO) therapy in an adult in the prehospital setting. CASE REPORT: A 46-year-old non-smoking man presented with a cough and fever. He suddenly deteriorated five days later. When the basic life support team arrived, his peripheral oxygen saturation (SpO(2)) in ambient air was 56% and respiratory rate 46 per minute. The man was weak with thoracoabdominal asynchrony. An emergency medical team with a physician was sent. As France was still under lockdown for the SARS-CoV-2 pandemic, COVID-19 was suspected. Despite 15 L/min of oxygen delivered with a non-rebreathing mask, the patient's SpO(2) tended to drop below 90% at the slightest effort and during transport from home to the ambulance. It was therefore decided to start HFNO therapy. The patient was transferred to an intensive care unit where HFNO was continued. Why should an emergency physician be aware of this? As trend in emergency medical services may move toward prehospital HFNO, this case report is an opportunity to question the feasibility of HFNO therapy in the prehospital setting.

High-flow nasal oxygen (HFNO) therapy is an oxygenation supplementation technique currently evaluated in many clinical situations, including the management of acute hypoxemic respiratory failure (AHRF). A clinical review discussed respiratory support for adults with COVID-19. This review recommended HFNO therapy as the second-line therapy of choice when it was not possible to maintain SpO 2 above 90% or when patients had increased work breathing. (1) This was in accordance with unpublished hospital guidelines in the area of case onset since the end of March 2020. Since then, several articles on the use of HFNO in COVID-19 have been published. (2, 3) Prehospital use of this technique represents a logistical challenge due to the amount of oxygen available and power supply. Our emergency medical service (EMS) was discussing the feasibility of HFNO therapy in the prehospital setting when SARS-CoV-2 pandemic occurred.

In regard to feedbacks from physicians working in intensive care unit (ICU), it was decided to place one device of HFNO therapy in a logistic vehicle that can be called upon on scene whatever the time of the day.

A 46-year-old non-smoking man (body mass index = 24 kg/m 2 ) with only a history of glaucoma treated with dorzolamide has had weakness accompanied by cough and fever. His treating physician prescribed an anti-inflammatory (diclofenac) and analgesic treatment (acetaminophen, codeine) for lower back pain. The patient's respiratory condition suddenly deteriorated five days later. Upon arrival of the basic life support team equipped accordingly to the recommendations of the World Health Organization in case of suspicion of COVID-19, the patient was slightly confused (Glasgow Coma Scale = 14) and had mild thoracoabdominal asynchrony. His peripheral oxygen saturation (SpO 2 ) was 56% in ambient air, and his respiratory rate (RR) was 46 per minute. His temperature was 36.7° C (98° F), blood pressure 122/80 mmHg, and pulse rate 100 beats per minute. An EMS team including an emergency physician experienced in prehospital medicine was dispatched to the scene, as well as the vehicle equipped with HFNO therapy device. Under 15 L/min of oxygen delivered with a non-rebreathing mask, SpO 2 increased very slowly, reaching, at best and only for a few minutes, 95%. When the medical team arrived, the RR was still elevated at 40 per minute and the patient was still a bit confused. He was able to speak few words at a time.

Thoracoabdominal asynchrony was still present. Lung auscultation found bilateral dry crackles. Each time the patient tried to make the slightest effort (during his repositioning for instance), SpO 2 dropped below 85% despite 15 L/min of oxygen, with the greatest difficulty thereafter in rising again above 90%.

Given the SARS-CoV-2 pandemic and the large number of patients with COVID-19 at the time of care in the region, given the relatively typical evolution of the disease and despite the absence of fever (which may have been absent at the scene due to the prior intake of nonsteroidal anti-inflammatory or acetaminophen), the most likely diagnosis was COVID-19 even though it was not possible, at this stage, to rule out a pulmonary infection from another cause. The absence of cardiac history, relatively young age and non-smoking habit were not in favor of pulmonary edema or acute exacerbation of chronic obstructive pulmonary disease.

Exacerbation of asthma was unlikely as the patient had no previous history of such disease.

Patient's rapid worsening could however have been a pulmonary embolism complicating an inflammatory state in a lung infection.

Despite the patient's relatively precarious clinical condition, it was decided not to immediately intubate him. It seemed, however, that his oxygenation profile remained, despite oxygen therapy, intermediate with a tendency to improve slowly in the absence of mobilization but to worsen rapidly with the slightest effort or added stressor. As the prehospital phase necessarily involves moving the patient and can be a major stressor, it was decided to start a session of HFNO while the patient was being transferred to the ICU (direct admission to an ICU from the field is a standard practice in France for the most serious cases).

The available HFNO device (AIRVO TM 2; FISHER & PAYKEL HEALTHCARE, Auckland, New Zealand) was not dedicated to prehospital practice and operated only on main power (no internal battery). The patient was quickly transferred half-seated from the apartment to the resuscitation ambulance under 15 L/min of oxygen. In the meantime, the HFNO therapy kit was prepared and connected to a dedicated 15 L 200 bar oxygen cylinder (figure 1). The HFNO device was powered via a plug in the ambulance. Once in the ambulance, as the patient's SpO 2 level was below 90%, HFNO was started with a 60 L/min flow rate. The fraction of oxygen in inspired air (FiO 2 ) was titrated in order to maintain SpO 2 above 94%. A surgical mask was applied on top of high-flow nasal cannula and the window of the ambulance was opened in order to allow ventilation. The patient was transferred to the closest ICU and had a total of 18 minutes of HFNO therapy during the prehospital phase. Patient's SpO 2 rapidly increased above 94% during transport but this improvement in oxygenation was only partially associated with clinical improvement : he was still weak and unable to speak without pause but his RR had decreased to 31 per minute. When the ambulance arrived at the hospital, as the HFNO device used didn't run on battery power (the HFNO device was powered via a plug in the ambulance), it was necessary to put the patient back on a nonrebreathing mask at 15 L/min of oxygen during the transfer on a wheeled stretcher to the ICU.

As the patient was no longer receiving HFNO, SpO 2 dropped just below 90% for a few minutes when he arrived in the ICU. Upon arrival at the ICU, HFNO therapy was reinstated ; SpO 2 improved above 90% in less than ten minutes.

Ten years after the first published use of HFNO in AHRF,(4) this case report presents for the first time logistical challenges with the prehospital use of HFNO in an adult with COVID-19induced respiratory distress.

The heating and humidification of gases seem to be particularly energy consuming. As the HFNO device used doesn't have internal batteries, its use is only possible where it can be plugged in. This raises the question of transfer phases (from the patient's home to the ambulance and from the ambulance to the definitive bed). As previously noted, the patient's saturation and dyspnea worsened during the transfer phase from the ambulance to the ICU.

The explanation is probably multimodal, partly related to the need to put the patient back under a non-rebreathing mask at 15 L/min of oxygen instead of HFNO, but also to the fact that the transfer phases can be long, uncomfortable, and increase patients respiratory work (this is even more true concerning the transfer phase between home and ambulance). We have tried to anticipate this problem by aiming for a high target of SpO 2 during ambulance transport in the hope that the patient wouldn't desaturate below 90% on arrival at the hospital during the transfer phase from the ambulance to the ICU bed, but we were not successful regarding that matter. Therefore, for future uses, in order to overcome this problem, we have decided to acquire an external and portable battery to power the HFNO device (lithium power cases, TECSUP, Annecy-le-Vieux, France).

Although HFNO therapy has been used in interhospital transport of critically ill children for several years, there is less constraint in terms of oxygen consumption in children than in adults. In the worst case scenario, a 4.5 L (277 in 3 ) ME36 cylinder at 207 bar (3000 psi) can be emptied in less than 16 minutes at 60 L/min and FiO 2 1. Therefore, it is necessary to have large-capacity cylinders permanently in the ambulance in case of prolonged field care and transport. In our EMS, there is currently only one HFNO device for six resuscitation ambulances. Therefore, it was decided to put the HFNO device in a logistics support vehicle where there are usually six 15 L 200 bar oxygen cylinders permanently. This organization overcomes the oxygen consumption problem but still requires good anticipation as soon as the call to the dispatch center is made and potential use of HFNO identified in order not to lose time during the prehospital care phase. To simplify this organization, one HFNO device and increased oxygen capacity could be available in every EMS ambulance.

In the context of the SARS-CoV-2 pandemic, one concern has been the risk of spreading the virus and contaminating healthcare workers. The risk of aerosolization with HFNO appeared to be only slightly higher than with a non-rebreather mask and much lower than with Venturi devices or non-invasive ventilation.(5) Caregivers must wear personal protective equipment (including gown, gloves, FFP2/FFP3 masks and goggles). As air volume in the ambulance is limited, the ambulance window can be opened to facilitate ventilation. As mentioned in the case report, a surgical mask was placed on the face of the patient, on top of the cannula. Since the case occurred, several studies have shown that this strategy can reduce the risk of aerosolization.(6,7) An additional mask on top of the cannula even seems to improve the oxygenation of the patient without any clinically significant side effect. (8) HFNO could also be of interest for per-apneic oxygenation during orotracheal intubation, or for some patients with "do-not-intubate" orders when orotracheal intubation seems too aggressive.

This case report describes the first prehospital use of HFNO therapy on an adult with AHRF.

It allows the discussion of strategies to manage the risk of aerosolization in patients with COVID-19 treated with HFNO in an ambulance. It proposes solutions, such as the use of external batteries to power the HFNO device, to apprehend logistical challenges.

Respiratory support for adult patients with covid-19

Use of high-flow nasal cannula and noninvasive ventilation in patients with COVID-19: a multicenter observational study

High-flow nasal cannula for acute respiratory distress syndrome (ARDS) due to COVID-19

High-flow oxygen nasal cannula in acute hypoxemic respiratory failure

Aerosol dispersion during various respiratory therapies: a risk assessment model of nosocomial infection to health care workers

Preliminary findings on control of dispersion of aerosols and droplets during high-velocity nasal insufflation therapy using a simple surgical mask: implications for the high-flow nasal cannula

Wearing of medical mask over the high-flow nasal cannula for safer oxygen therapy in the covid-19 era

Surgical mask on to of high-flow nasal cannula improves oxygenation in critically ill COVID-19 patients with hypoxemic respiratory failure

Figure Figure 1: High-flow nasal oxygen therapy device being used in a resuscitation ambulance

Why should an emergency physician be aware of this?As trend in emergency medical services may move toward prehospital HFNO, this case report is an opportunity to question the feasibility of HFNO therapy in the prehospital setting.