Respiratory Medicine

Helmet CPAP in the emergency department: A narrative review

a b s t r a c t

Background: The choice of correct interface for the right patient is crucial for the success of non-invasive ventila- tion (NIV) therapy. Helmet CPAP is a type of interface used to deliver NIV. Helmet CPAP improves oxygenation by keeping the airway open throughout the breathing cycle with positive end-expiratory pressure (PEEP).

Objective: This narrative review describes the Technical aspects and clinical indications of helmet continuous pos- itive airway pressure (CPAP). In addition, we explore the advantages and challenges faced using this device at the Emergency Department (ED).

Discussion: Helmet CPAP is tolerable than other NIV interfaces, provides a good seal and has good airway stability. During Covid-19 pandemic, there are evidences it reduced the risk of aerosolization. The potential clinical benefit of helmet CPAP is demonstrated in acute cardiogenic pulmonary oedema (ACPO), Covid-19 pneumonia, immu- nocompromised patient, acute chest trauma and palliative patient. Compare to conventional oxygen therapy, helmet CPAP had been shown to reduce Intubation rate and decrease mortality.

Conclusion: Helmet CPAP is one of the potential NIV interface in patients with acute respiratory failure presenting to the emergency department. It is better tolerated for prolonged usage, reduced intubation rate, improved respi- ratory parameters, and offers protection against aerosolization in infectious diseases.

(C) 2023

  1. Introduction

non-invasive ventilation (NIV) is an established strategy in the provision of oxygen for the treatment of patients with acute respira- tory failure [1]. NIV has gained traction in the emergency depart- ment (ED) in recent years due to increasing evidence that early initiation improves outcomes [2,3]. In the year 2020, the Food and Drug Association (FDA) of the United States issued the “Umbrella Emergency Use Authorization for Ventilators and Ventilator Acces- sories”, which removed restrictions on the use of NIV for manage- ment of Covid-19 [4]. This had led to a sudden surge in NIV usage outside the ICU due to the shortage of ventilators and ICU beds in the Covid-19 pandemic [5,6].

The helmet CPAP was invented by Mr. Maurizio Borsari, an Italian, in 1991 [7]. It was popularized by the Europeans in the 1990s for usage in non-invasive ventilation [8]. At present, helmet CPAP is one of the alter- native interface as oxygen delivery device to support patients with acute respiratory failure in EDs and wards with a 60-70% success

* Corresponding author.

E-mail address: [email protected] (O. Adi).

rate [9-11]. The helmet interface had also been reported to be effective in lowering the risk of endotracheal intubation and reducing mortality, followed by the facemask interface, high flow nasal oxygen, and regular oxygen therapy [12].

Choosing the correct interface for the right patient is crucial for the success of NIV therapy [13]. This is especially so at the emergency department, which may be overwhelmed with critically ill patients due to a lack of intensive care unit (ICU) resources [14,15]. In this review, we aim to update the latest evidence of helmet CPAP in the ED concerning the role, benefits and challenges faced in utilization of this interface.

  1. Methodology

A search was performed using PubMed National Library, MEDLINE, Cochrane Database and Google Scholar until 15 December 2022. The key words entered were “acute respiratory failure”, “non-invasive ven- tilation”, “NIV”, “non-invasive positive pressure ventilation”, “NIPPV” and “continuous positive airway pressure”, “CPAP”, “helmet NIV”, “helmet CPAP”, and “oxygen therapy”. We excluded studies of pediat- rics, animal subjects and languages other than English. Authors decided which studies to include for the review by consensus.

https://doi.org/10.1016/j.ajem.2023.02.030

0735-6757/(C) 2023

  1. Results

A total of 54 articles, which included 40 clinical and 14 physiological studies were identified for this review. The clinical studies included 7 meta-analysis, 10 randomized controlled trial, 4 systematic reviews, and 19 observational studies [refer to Fig. 1]. The summary and charac- teristics of the reviewed articles were presented in Supplementary 13.

  1. Technical aspect of Helmet CPAP

Helmet CPAP consists of a transparent hood with a plastic ring base that encloses a patient’s head entirely. The hood comes in various sizes, and the correct size is determined by the measurement of the patient’s neck circumference. There is a soft neck seal that interfaces with the patient. When the helmet is inflated, the neck seal creates a gentle air cushion, effectively separating the breathing circuit from the outside environment. The helmet is fastened in place by padded underarm braces [15].

There are two air-flow ports on the helmet. Some models have addi- tional ports for other purposes, such as drinking, feeding, drainage, suc- tion, or temporary access to the patient [16]. Helmet CPAP can also feature an anti-suffocation valve that draws in fresh air while maintain- ing pressure when gas flow is interrupted [17].

Helmet CPAP is typically set up in a free-flow configuration, with air supply delivered via the inspiratory limb and an adjustable PEEP valve on the expiratory limb. It requires a high-flow air supply of at least 40 l per minute [18]. The air supply is generated either by a venturi sys- tem or an air/oxygen blender [19,20]. When using an air/oxygen blender, a medical air source is required in addition to the oxygen

supply. Flow rate and fraction of inspired oxygen (FiO2) are titrated using the air supply system [refer to Fig. 2]. Helmet CPAP improves oxy- genation by keeping the airway open throughout the breathing cycle with positive end-expiratory pressure (PEEP). PEEP is usually titrated to 10-15cmH20 [21]. Although helmet CPAP can be setup in a closed- circuit configuration, with air supply from a ventilator or turbine gener- ator, a closed-circuit is only mandatory for BiPAP delivery.

  1. The evidence for Helmet CPAP in specific diseases
    1. Acute cardiogenic pulmonary oedema (ACPO)

NIV had been shown in Cochrane reviews to reduce intubation and mortality rates in acute cardiogenic pulmonary oedema (ACPO) com- pared to standard oxygen therapy alone [22,23]. The early landmark 3CPO trial, which recruited 1069 ACPO patients from 26 EDs, found that there was no difference in 7-day mortality for CPAP (11.7%) versus NIPPV (11.1%; p = 0.81) [24].

The use of CPAP in pre-hospital setting for presumed ACPO had been shown to be safe and feasible [25-27]. In 2008, helmet CPAP was de- scribed in a prospective cohort study on 121 patients in an out-of- hospital setting. 104 (86%) of the patients were confirmed to be ACPO. The patients showed significant improvement in oxygenation and re- spiratory rate, with none of them needing intubation at the pre- hospital level [25].

Adi et al. published 2 RCTs on the use of helmet CPAP at the emer- gency department in 2021. In the first study, 188 ACPO patients were randomized to receive helmet CPAP or HFNC. Helmet CPAP was found to be better than HFNC in improving respiratory rate, heart rate, PaO2/

Image of Fig. 1

Fig. 1. Flow diagram of studies included in this review.

Image of Fig. 2

Fig. 2. Free-flow configuration of helmet CPAP.

Oxygen supply can use either an air/oxygen blender (A) or a venturi system (B). The addition of heat and moisture exchanger (HME) filter (C) improves air humidity and reduces noise level. The hood (D) is fastened with padded underarm braces (E). Helmet CPAP may feature an anti-suffocation valve (F) that draw in air when oxygen supply is interrupted. A high-ef- ficiency particulate air (HEPA) filter (H) is added to prevent aerosol dispersion. Positive end-expiratory pressure can be titrated with an adjustable valve (I) and the pressure level is mon- itored using a barometer (G). For aerosol therapy, a nebulizer circuit (J) can be added by utilizing the anti-suffocation valve port.

FiO2 ratio, HACOR score and Dyspnea Scale. However, no significant dif- ference was found in terms of intubation rate and survival between the two interfaces [28]. In another RCT, Adi Osman and colleagues studied 224 AHRF patients in the ED, out of which 194 (87%) patients were di- agnosed with ACPO. They found that the intubation rate was lower for helmet CPAP compared to face mask CPAP (4.4% versus 18%, p = 0.003) [29] (Refer to Table 2).

    1. Acute exacerbation of chronic obstructive pulmonary disease (AECOPD)

International guidelines recommend NIV as first line respiratory support in hypercapnic respiratory failure caused by AECOPD [30]. A Cochrane review on 1264 patients with AECOPD from 17 clinical trials found that NIV via delivery of Bilevel positive airway pressure decreased the risk of mortality by 46% and need for endotracheal intu- bation by 65% [31]. Although a face mask interface was more commonly used in the literature, helmet had also been described for delivery of NIV in AECOPD patients [32]. A randomized controlled trial by Pisani and colleagues on 80 patients with AECOPD treated with helmet NIV showed no difference in arterial blood gas (ABG improvement) or toler- ance compared to face mask NIV [33].

There is paucity of study evaluating CPAP as a mode of respiratory support for AECOPD regardless of interface. A retrospective observa- tional audit on 237 patients with AECOPD who were treated with face mask CPAP showed Mortality benefit, less intubation and reduced in- tensive care unit (ICU) length of stay [34]. In a subgroup analysis of 38 patients presenting to the ED with AECOPD, Osman et al. they found that there was no significant difference in oxygenation improvement or CO2 clearance between helmet CPAP and face mask CPAP [29]. This is in contrast to the study by Antonelli et al. earlier, which found that CO2 clearance was less efficient with helmet interface on COPD patients

[32] (refer to Table 2).

Before the Covid-19 era, NIV was used with reported varying success of 20-76% in patients with AHRF due to community acquired

pneumonia [35]. In an RCT by Consentini et al. on 47 pneumonia pa- tients with AHRF at the ED, 95% of the patients treated with helmet CPAP achieved target oxygenation faster within 1.5 h compared to stan- dard oxygen therapy, which reached the end point of a paO2/FiO2 ratio > 315 at 46.6 h [36]. Another RCT on 40 patients with pneumonia at the high dependency unit (HDU) by Brambilla et al., found that the rate of endotracheal intubation in the helmet CPA group is lower at 15% compared to 63% in the oxygen therapy group [37].

For ARDS, Patel et al. successfully used helmet CPAP on 83 patients at an adult medical ICU in 2016. The RCT, which compared helmet with face mask NIV, demonstrated a significant reduction in intubation rates (18% versus 61.5%) and lower 90-day mortality (34.1% versus 56.4%) [38]. However, the LUNG SAFE (Large Observational Study to Un- derstand the Global Impact of Severe Acute Respiratory Failure) study cautioned the use of NIV in ARDS after higher ICU mortality was re- ported in patients with PaO2/FiO2 lower than 150 mmHg [39]. For now, the use of helmet NIV is better be reserved for patients with mild to moderate ARDS [40] (refer to Table 2).

    1. Covid-19 pneumonia

Covid-19 pneumonia can present as a spectrum of disease and may progress from mild pneumonia to severe ARDS [41]. Two Covid-19 phe- notypes had been identified: the L-type (low elastance), happening at the earlier part of the disease, and type H (high elastance), signifying a more severe disease. NIV might improve Covid-19 patients with the L- phenotype and, if used for the H-phenotype, should not delay intuba- tion [42]. According to a meta-analysis of 17 studies, helmet CPAP was the predominant NIV device used for Covid-19 outside the ICU during the peak of the pandemic [11]. During the early days of the pandemic, observational studies showed that helmet CPAP use outside ICU was able to sustain patients who failed conventional oxygen therapy, with Bellani reporting a success rate of 75% and Coppadoro 69% in avoiding intubation and death [9,10]. Franco et al. who studied 670 patients with Covid-19 pneumonia, found no difference between CPAP and other NIV modalities in terms of mortality, intubation rates, or length of stay [43].

During the Covid-19 pandemic, helmet CPAP improved mortality of 24% of the hypoxic patients at an emergency department in Italy, who

were on maximal oxygen therapy and could not be intubated due to lack of resources [5]. Brusasco et al. also used CPAP successfully on 64 patients with moderate to severe COVID-19 pneumonia, with a reported 83% recovery without intubation [44].

Awake Prone positioning had been advocated in spontaneously breathing patients with Covid-19 pneumonia [45]. The combination of prone positioning and NIV had been shown to improve oxygena- tion, with a Pa/FiO2 ratio of 314 compared to 166 in the supine posi- tion. 65% of the patients who were prone also had reduced Work of breathing by 10% [46]. A more recent systematic review on the use of helmet CPAP with Awake prone positioning found it to be a feasi- ble and safe strategy for Covid-19 pneumonia patients at the emer- gency department [47].

    1. Immunocompromised

There are accumulating evidence supporting the role of NIV in im- munocompromised patients with acute respiratory failure. A meta- analysis by Huang et al. on 5 RCTs involving 592 patients found that NIV in the immunocompromised had short term mortality benefit (Pooled risk ratio 0.62, p = 0.01) and reduced intubation (Pooled risk ratio 0.52, p = 0.01) and shortened length of ICU stay (Mean differ- ence -1.7 days, p = 0.008) compared to oxygen therapy [48]. A small case control study on a similar group of patients by Rocco et al. showed that helmet is a viable alternative to face mask NIV with better patient tolerance and less complications [49].

    1. Traumatic chest injury

Helmet CPAP may also play a role in traumatic chest injuries that present with AHRF. A meta-analysis by Chiumello et al. in 2013 on chest trauma patients at ICUs and emergency departments also showed that face mask NIV conferred mortality benefits with a relative risk of

0.26 (p = 0.003) compared with the standard of care [50]. A recent

RCT conducted by Liu et al. at an emergency ICU showed that NIV deliv- ered via helmet compared to face mask interface was associated with better patient tolerance (69% versus 30%), greater improvement in oxy- genation (PaO2/Fio2 ratio 277 versus 225) and less NIV related compli- cations (10% versus 43%) [51].

Clinical practice guidelines are guarded in making recommendations on the use of NIV in asthma due to lack of strong evidence [1,52]. A large retrospective cohort study by Althoff et al. found that NIV use in asthma exacerbations was associated with reduction in endotracheal intubation (odds ratio 0.36) and in-hospital mortality (odds ratio 0.48) [53]. When looking specifically at ED patient population with acute asthma, a retrospective analysis by Manglani and colleagues on 109 patients who received face mask NIV found the rate of NIV failure to be low at 10% [54]. To date, there is no study published on the use of helmet CPAP in patients with AHRF secondary to asthma exac- erbation in the ED.

    1. Palliative

NIV can be used as a treatment strategy for palliative care of patients who are suffering dyspnea at the end of life [55,56]. A meta-analysis by Wilson et al. in 2018 on 30 studies, reported a pool survival rate of 56% at hospital discharge with data showing no decrease in quality of life among survivors [57]. However, a study by Vilaca and colleagues per- formed specifically on 70 ED patients with “do not intubate” order found that 59% of the patients had their NIV stopped as they did not ex- perience improvement in symptoms [58]. To date, there is no study spe- cifically on helmet interface as palliative NIV.

  1. Advantages and limitations of Helmet CPAP

Helmet CPAP provides good airway pressure stability. The large con- tact area of the neck seal with the patient is effective in preventing air leaks [59]. As the helmet is fastened to the patient’s body, the integ- rity of its seal is not affected by facial features [16]. Patients feel less claustrophobic, as there is more space and their head movements are not restricted. Furthermore, the presence of ports for drinking and feeding results in less interruption of NIV. Because of this, the helmet interface is well tolerated for prolonged usage with less risk of NIV failure [60,61].

The use of NIV may produce aerosols that may increase the transmis- sion of diseases in the crowded ED [43]. Helmet CPAP has a lower risk of aerosol dispersion, making it a good choice for the treatment of Covid-

19 hypoxic respiratory failure [42,62,63]. The addition of high- efficiency particulate air (HEPA) filter on the expiratory limb can reduce the risk of environmental contamination [64,65]. However, moisture build-up will increase resistance in this configuration. Therefore, the HEPA filter should be placed after the expiratory valve [66].

CO2 rebreathing risk exists for all NIV interfaces. CO2 level within the helmet CPAP is primarily determined by the flow rate of air sup- ply and expired CO2 of the patient [67]. Therefore, the flow rate must be greater than the patient’s peak inspiratory flow. Flow rate above 40 l per min for helmet CPAP prevents clinically relevant CO2 rebreathing [18,19,68].

Air humidity and temperature that approximate ambient air is bet- ter tolerated. At high flow rate, the air inside the helmet becomes dry [14,21,69], which can lead to mucosal dryness during prolonged usage [61,70]. The noise level inside the helmet is substantially loud. Adding a heat and moisture exchanger (HME) at the inspiratory limb of the breathing circuit, makes the air humidity and temperature within the helmet more comfortable for the patient [69,71]. The addition of HME also reduced noise level to some extend [72]. The use of earplugs should also be considered, especially during sleep [61].

The pressure point of the helmet CPAP is at its underarm braces. This can increase the risk of developing upper extremities deep vein throm- bosis (UEDVT), especially in Covid-19 patients [73]. A counter-weight fixation method had been proposed to replace the underarm braces for prolonged usage [74].

Aerosol therapy may be required for patients started on helmet CPAP. Beta-adrenergic agonist aerosol therapy delivered via facemask NIV had been shown to produce faster clinical improve- ment in patients when compared to delivery using small-volume nebulizer [75]. To administer aerosol therapy, an additional circuit can be added to the helmet interface via the patient’s access port. However, no study has been done on the clinical efficacy of aerosol therapy via helmet NIV.

  1. Comparison between Helmet CPAP and other oxygen modalities
    1. Helmet CPAP versus conventional oxygen therapy

In the emergency setting, COT is usually started at the first medical contact for hypoxemic patients with a patent airway. The COT is usually delivered by a non-rebreather mask with a reservoir bag at 15 l per min to maintain a target saturation of 94-98% [76]. However, when oxygen- ation cannot be maintained with COT, helmet CPAP can be used to im- prove oxygenation [77,78].

Helmet CPAP provides High-flow oxygen delivery, regardless of the patient’s breathing pattern. This ensures a constant fraction of inspired oxygen (FiO2) compared to conventional oxygen therapy [79,80]. Conventional oxygen therapy (COT) with the exception of the venturi mask, are unable to provide a constant inspiratory oxygen fraction (FiO2), as the oxygen provided is diluted with the surrounding air and dependent on the patient’s inspiratory demands (refer to Table 1).

Table 1

Table Comparing Helmet CPAP with Different Oxygen Therapy.

Interface

COT

HFNC

Mask

Helmet

Setting

Nasal prong

oxygen flow rate

Oxygen flow rate

Oxygen flow rate

Flow rate

20 to 60 l/min

Fixed according to ventilator

Minimum 40 l/min

-1 to 6 l/min

CPAP

CPAP

FiO2-0.21-0.45

Face mask

5 to 10cmH20

5 to 10cmH20

Flow rate

Temperature

-5 to 10 l/min

31 ?C to 37 ?C

FiO2-0.35-0.55

Venturi mask

FiO2

BIPAP:

BIPAP:

Flow rate

0.21 to 1.0

IPAP 10 to 20cmH20

IPAP

-4-12 l/min

EPAP 5 to 10cmH20

(50% higher than usual)

FiO2-0.24 to 0.60

EPAP

Non-rebreather mask

(50% higher than usual)

Flow rate

-10-15 LPM

FiO2-0.6-0.8

Technical Parameters

Air leak High incidence of leakage High incidence of leakage Low-air leak incidence Low-air leak incidence

CO2 rebreathing Not present Wash out dead space with flow >30 l/min Present but negligible Present but negligible

The nasal mask-fit must be <50% of the nares area

Slightly higher than anatomical d

ead space volume-175 ml

The mechanical dead space volume was 15-20 L

Tolerability Tolerable Tolerable Less tolerable Tolerable

Noise Very low Low Low Loud noise

Mucosa dryness Higher incidence at higher flow

rate

Low incidence Low incidence Low incidence,

Skin ulceration Present, in prolonged usage Insignificant Present, around the mask Present, over the neck and under-arm

    1. Helmet CPAP versus face mask NIV

The best NIV interface is one that provides comfort, provides a good seal, has a low dead space and is not too noisy [15]. Despite improve- ment in the design and modification of the years, no perfect interface exists. The use of NIV dates back to 1940s, when the anesthesia mask was used to deliver positive pressure ventilation [81]. Subsequently var- ious types of mask interfaces had been invented, which cover the mouth, nose and whole face. Before the introduction of helmet, the oro-nasal interface, also known as face mask NIV is the most commonly used and studied interface [16].

The helmet CPAP was developed to overcome the limitations of the face mask interface, which causes discomfort with prolonged usage [61]. The lack of contact with the face with helmet CPAP provides more comfort compare to the face mask NIV. There is less risk of pres- sure sores, eye complications and upper airway obstruction due to back- ward jaw displacement [15].

In a poorly fitted mask, air leak may interfere with effective ventila- tion [82]. Helmet CPAP has less issue with air leaks, enabling a constant

Table 2

Summary of current evidence of helmet CPAP in specific diseases.

Disease Evidence Recommendations

delivery of positive end expiratory pressure (PEEP) and a consistent supply of oxygen [19]. In comparison to face mask interface, helmet CPAP also has less risk of aerosolization, which enhances safety during respiratory infection outbreaks [62,83].

In terms of CO2 removal, the helmet CPAP with its larger dead space may lose out to face mask NIV. Compare to face mask, helmet CPAP is more susceptible to CO2 rebreathing, due to the mixture of the inhaled and exhaled gas in the large dead space created by the internal volume of the helmet [21,68]. Nevertheless, Adi Osman et al. demonstrated that neither the face mask CPAP nor the helmet CPAP had a significant effect on CO2 removal in both ACPO and AECOPD population [29] (refer to Table 1).

high flow nasal cannula is a form of oxygen therapy that provides heated and humidified high flow oxygen to the patient. Ini- tially used in neonates, the HFNC gained popularity in the adult critically ill patients in the late 2000s after it was made popular by the FLORALI trial for its usage in hypoxemic patients [84].

Although the HFNC generates some positive pressure effect, the hel- met CPAP is better and more predictable in providing a higher PEEP [21,28,85]. The first randomized controlled trial (RCT) done in the emer- gency department in patients with ACPO by Adi Osman et al., found that

ACPO Meta-analysis

Systematic review RCT

AECOPD Meta-analysis

Systematic Review RCT

Strongly recommended

Limited evidence

helmet CPAP is better than HFNC in improving respiratory and hemody- namic parameters [28. The findings could be explained by the unreliable PEEP effect in the HFNC group, which could be lost when the patient’s mouth is not closed [86].

For patients with moderate to severe hypoxemia due to Covid-19,

AHRF secondary to pneumonia and ARDS

RCT Recommended for mild to moderate hypoxemia

the HENIVOT RCT showed that the helmet NIV is more successful in re-

ducing intubation rates (30% versus 51%, p-0.03) compared to HFNC, al-

Immunocompromised Meta-analysis

Case control study

Chest trauma Meta-analysis RCT

Asthma exacerbation No study performed on

helmet NIV or CPAP

Palliative care No study on helmet NIV or CPAP

Limited evidence Limited evidence Not Applicable Not Applicable

though the duration of respiratory support remained the same [87]. In terms of the risk of viral transmission, both HFNC and helmet CPAP had been demonstrated to have low risk of aerosol generation [88-90]. A physiological study by Grieco et al. in 2020 comparing the two in- terfaces also found helmet NIV to be more effective than HFNC in hyp- oxemic respiratory failure due to its ability to increase PaO2/FiO2 (255 versus 138, p = 0.001)), reduced dyspnea (visual analog scale 3 versus

8, p = 0.002) and improve inspiratory effort (7cmH20 versus 15, p = 0.001) [91]. However, the latest meta-analysis by Chaudhuri et al. com- paring helmet NIV with HFNC, did not find any difference in outcomes or mortality between the two devices [92] (refer to Table 1).

  1. Challenges faced in usage of Helmet CPAP at the emergency department

When choosing the preferred configuration of helmet CPAP for the emergency department, there are several key points that should be taken into consideration. With experience from the Covid-19 pandemic, scalability in response to demand is important [93]. A reliable source of medical gases from the pipelines must not be overlooked. Many emer- gency departments expanded their capacity with make-shift areas. The existing hospital medical gas pipeline system may not meet the surge in demand. It is important to be prepared for a sudden drop in supplied gas pressure [94,95].

With a high healthcare provider-to-patient ratio in the emergency department, monitoring of patients on helmet CPAP is a challenge [96]. It is important to assess the patient’s condition and detect signs of deterioration to avoid delay in intubation [97]. HACOR score is a ro- bust predictor of NIV failure, and its use on helmet NIV has been de- scribed in Covid-19 patients [98,99].

Staff training is important to ensure competency in setting up the helmet NIV and monitoring during therapy. Multi-pronged strategies can be deployed to enhance learning. This includes distribution of edu- cational videos, regular teaching and organization of practical sessions for emergency department staff [100].

  1. Conclusion

Helmet CPAP use has been shown to be beneficial in many diseases and its efficacy is comparable to face mask NIV and HFNC. It should be recommended as an alternative interface in patients with acute respira- tory failure presenting to the emergency department. It is better toler- ated for prolonged usage and offers protection against aerosolization in infectious diseases.

Authors’ contribution

AO, CPF, YKY,FNA and NLR was involved in the initial conception and drafting of the manuscript. All authors contributed to the iwriting and revision of the manuscript.

Ethics approval and consent to participate

Not applicable.

Funding information

Authors received no funding for this review from any institution/ in- dividual.

CRediT authorship contribution statement

Osman Adi: Writing – review & editing, Writing – original draft, Visualization, Validation, Supervision, Resources, Methodology, Formal analysis, Data curation, Conceptualization. Chan Pei Fong: Writing – review & editing, Writing – original draft, Validation, Supervision, Resources, Project administration, Formal analysis, Data curation, Conceptualization. Yip Yat Keong: Writing – review & editing, Writing – original draft, Resources, Methodology, Data curation, Conceptualization. Farah Nuradhwa Apoo: Writing – review & editing, Writing – original draft, Validation, Formal analysis, Data curation. Nurul Liana Roslan: Writing – review & editing,

Writing – original draft, Project administration, Methodology, Formal analysis, Data curation, Conceptualization.

Data availability

The material available from the corresponding author on reasonable request.

Declaration of Competing Interest

The authors declare that they have no competing interests.

Acknowledgements

We would like to thank Ipoh Emergency Critical Care Society (IECCS) for their assistance and the Director General of Ministry of Health, Malaysia for his permission to publish this article.

Appendix A. Supplementary data

Supplementary data to this article can be found online at https://doi. org/10.1016/j.ajem.2023.02.030.

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