Prehospital Noninvasive Ventilation: An NAEMSP Position Statement and Resource Document

Abstract

Noninvasive ventilation (NIV), including bilevel positive airway pressure and continuous positive airway pressure, is a safe and important therapeutic option in the management of prehospital respiratory distress.

NAEMSP recommends:

• NIV should be used in the management of prehospital patients with respiratory failure, such as those with chronic obstructive pulmonary disease, asthma, and pulmonary edema.

• NIV is a safe intervention for use by Emergency Medical Technicians.

• Medical directors must assure adequate training in NIV, including appropriate patient selection, NIV system operation, administration of adjunctive medications, and assessment of clinical response.

• Medical directors must implement quality assessment and improvement programs to assure optimal application of and outcomes from NIV.

• Novel NIV methods such as high-flow nasal cannula and helmet ventilation may have a role in prehospital care.

Key words:

• noninvasive ventilation
• prehospital
• CPAP
• BiPAP
• NIPPV

Introduction

Noninvasive ventilation (NIV) is a form of mechanical ventilatory support delivered through a face or nasal mask, without the use of an endotracheal tube, laryngeal tube, or other invasive airway device (1). NIV is a widely used method of supporting respiration that has been used by advanced life support (ALS) personnel in the prehospital setting for over two decades (2). More recently, following the addition of NIV at the Emergency Medical Technician (EMT) level in the 2019 National EMS Scope of Practice Model, basic life support (BLS) EMS systems are increasingly incorporating use of NIV (3). Methods of delivering NIV include continuous positive airway pressure (CPAP) and bilevel positive airway pressure (BiPAP) ventilation. Novel devices for the delivery of NIV, such as high-flow nasal cannula (HFNC) and positive pressure helmets, are evolving but less proven methods of NIV being used in the prehospital setting. This resource document reviews the rationale and data supporting the use of NIV in the prehospital setting.

Methods

To inform this position statement and resource document, we performed a structured rapid review of the literature relevant to the use of NIV. Rapid reviews serve as a streamlined approach to synthesize evidence based on the principles of a systematic review of the literature, simplified to produce information in a timely manner (4). We searched PubMed (via National Library of Medicine) using EndNote X9.3.3 (Clarivate, Inc., Philadelphia, PA) for articles published before June 2021. The keywords and search strategy are described in Table 1. The search strategy first identified published literature containing terms relevant to noninvasive ventilation, including variations of CPAP and BiPAP ventilation. These publications were then restricted to those containing terms relevant to emergency medical services (EMS), including prehospital and transport medicine. Non-English publications were excluded. The strategy identified 391 articles available for screening. We reviewed titles and abstracts for articles relevant to the use of NIV in the EMS setting, resulting in 125 articles retained for consideration by all authors to inform this position statement and resource document on prehospital NIV use. Additional publications were identified by the authors, including through bibliography searches.

Table 1. Search terms and strategy of rapid literature review.

#	Search Terms (All Fields)	Articles
1	nippv OR ‘noninvasive ventilation’ OR ‘noninvasive ventilation’ OR ‘noninvasive positive pressure’ OR ‘noninvasive positive pressure’ OR ‘noninvasive positive-pressure’ OR ‘noninvasive positive-pressure’ OR ‘noninvasive pressure support’ OR ‘noninvasive pressure support’	8,492
2	cpap or ‘continuous positive airway pressure’	15,333
3	bipap OR ‘bilevel positive airway pressure’ OR ‘bilevel positive pressure’ OR ‘bilevel noninvasive ventilation’ OR ‘bilevel noninvasive ventilation’ OR ‘bi-level positive airway pressure’ OR ‘bi-level positive pressure’ OR ‘bi-level noninvasive ventilation’ OR ‘bi-level noninvasive ventilation’	1,210
4	#1 OR #2 OR #3	23,064
5	#4 AND [‘emergency medical service*’ OR ‘emergency health service*’ OR prehospital OR pre-hospital OR out-of-hospital OR ambulance]	360
6	#4 AND [emt OR ‘emergency medical technician*’ OR ‘paramedic*’]	102
7	#4 AND [‘air medical’ OR ‘air medicine’ OR aeromedicine OR aeromedical OR ‘aero medicine’ OR ‘aero medical’]	12
8	#4 AND [interfacility OR ‘inter-facility‘ OR interhospital OR ‘inter-hospital’]	20
9	#5 OR #6 OR #7 OR #8	441
10	#9 AND [English]	391

Safety and Efficacy of Prehospital Noninvasive Ventilation

NIV should be used in the management of prehospital patients with respiratory failure, such as those with chronic obstructive pulmonary disease, asthma, and pulmonary edema.

Both hypoxic and hypercarbic respiratory failure are worsened by collapse of small airways. Positive airway pressure ventilation stents open these airways, allowing for better delivery of oxygen and more gas exchange to occur. Positive pressure maintained throughout the respiratory cycle allows small airways and alveoli to stay open, of particular benefit to patients with obstructive diseases that compromise exhalation and are characterized by CO₂ retention (5). Additionally, it has been postulated that positive pressure ventilation provides hydrostatic pressure that can assist with moving fluid out of the alveoli (6), a beneficial effect in the treatment of patients with pulmonary edema. These beneficial effects of positive pressure ventilation make chronic obstructive pulmonary disease, asthma, and pulmonary edema the most common targets for NIV use. In addition, for each of these conditions NIV decreases the work of breathing, providing needed support for patients in decompensated respiratory failure. NIV may also be beneficial for augmenting oxygenation prior to endotracheal intubation, though this has not been studied in the prehospital setting (7).

Of concern in the use of NIV is that excess intrathoracic pressure can decrease cardiac filling and preload, subsequently decreasing cardiac output. This is of particular concern in patients with cardiogenic or hypovolemic shock where NIV use should be considered with caution. Additionally, positive pressure ventilation may exacerbate a pneumothorax or pneumomediastinum, examples of relative contraindications to its use.

Multiple studies have investigated the use of NIV in the emergency department and intensive care unit settings, demonstrating patient-centered outcome benefits, including lower rates of intubation and decreases in mortality compared to conventional oxygen therapy (8–10). Following this experience, NIV was adapted to the prehospital setting for use by ALS personnel and supported in its early implementation primarily by observational studies establishing its safe use in prehospital patients (11–15).

An early quasi-randomized prospective trail of BiPAP use for prehospital patients with presumed congestive heart failure demonstrated improved oxygen saturation in the BiPAP versus standard care group (11). Though the study did not find a difference in hospital length of stay, intubation rate, or mortality, the authors commented on the EMS personnel’s perceived safety of using BiPAP in prehospital patients, with 97% reporting it was easy to use and appeared to improve patients' dyspnea and respiratory distress. A subsequent prospective RCT that compared the use of prehospital CPAP for acute respiratory failure versus standard care demonstrated a 30% decrease in intubation and 21% decrease in mortality for the CPAP group (16). While small in enrollment, this study demonstrated a large effect size and clinical impact of prehospital CPAP use.

Supporting these studies from the United States are several RCTs from other countries demonstrating the safety and improved outcomes for prehospital patients receiving NIV. In a physician-staffed French EMS system, prehospital patients with cardiogenic pulmonary edema randomized to CPAP, compared to usual medical care, experienced improvements in a dyspnea clinical score and in arterial blood gas measurements (17). Patients also experienced a reduced incidence of endotracheal intubation and in-hospital mortality. Similarly, another study of patients with cardiogenic pulmonary edema randomized to CPAP in addition to standard care versus standard care alone had improvement in a composite endpoint that included death, presence of intubation criteria, and persistence of respiratory distress criteria (18). These and other studies were summarized in a systematic review and meta-analysis of 10 randomized or quasi-randomized studies that found that CPAP reduced both mortality and intubation rate compared to standard care (19). A smaller systematic review of five randomized and non-randomized comparative studies found a similar effect with reductions in the number of intubations and mortality in patients treated with prehospital CPAP (20). The most recently published RCT found in our review was from an Australian EMS system with paramedics of similar practice capability to U.S. ALS-level care, where 708 prehospital patients with acute respiratory distress were randomized to receive CPAP and usual care versus usual care alone (21). While this study did not demonstrate a difference in mortality or hospital length of stay, CPAP was associated with a greater decrease in dyspnea scores and respiratory rate.

The two primary delivery modalities for administering CPAP or BiPAP are through a venturi blended air system powered by pressurized oxygen or by a turbine-driven battery-powered ventilator. No prehospital studies were identified in our literature review that have compared pressurized air versus turbine ventilator systems head-to-head; however, many EMS systems have adopted pressurized air systems as they are simpler and generally lower priced. Because of the mechanics of these devices, they require large amounts of pressurized oxygen to maintain ventilator pressure, which can limit the length of time they can be used (22). The masks are also difficult to use in patients with facial hair, edentulous patients, or other craniofacial abnormalities that limit the ability for appropriate mask fitting. Additionally, not all masks and devices are created equally. Brusasco et al. evaluated two different devices and found that many kits were unable to deliver all necessary features, such as delivering the maximal air-flow output (23). When selecting an NIV system, and EMS agency and medical director should consider the anticipated pressures and FiO₂ that are intended to be used, the availability of oxygen in the transport vehicle, and the financial costs of both the device and accessories (23).

The selection of CPAP vs BiPAP in the prehospital environment has not been sufficiently studied. However, in some retrospective reviews, both have been shown to be feasible and have potentially improved patient outcomes (24). While the majority of studies focus on CPAP, there are some that also examine BiPAP and have similar conclusions regarding safety and feasibility (11,24–26). The above cited literature suggests that, when applied to the appropriate patient population (primarily CHF and COPD), CPAP and BiPAP can improve most objective markers of respiratory distress (SpO₂ measurements, respiratory rate, and work of breathing), and can also improve clinical outcomes such as need for subsequent intubation and overall mortality. The majority of studies are small (most less than 100 patients enrolled), and many demonstrate a neutral outcome when focusing on major clinical endpoints such as decreased intubation rates and mortality. However, a meta-analysis suggests positive outcomes in many endpoints, including rates of endotracheal intubation, hospital and intensive care unit length of stay, and vital signs with the prehospital administration of NIV, making it an important branch of the prehospital treatment algorithm for respiratory distress and failure (27). Additional investigation would be beneficial to exploring the differential use of CPAP versus BiPAP in the prehospital setting.

In aggregate, the existing literature, consisting of both observational and multiple randomized controlled trials, has established the safety and efficacy of using NIV in the prehospital setting for the management of patients with acute severe dyspnea. No evidence exists to make a recommendation regarding CPAP versus BiPAP, or pressurized oxygen versus turbine-driven battery-powered ventilators in the prehospital setting.

Use of NIV by BLS Personnel

NIV is a safe intervention for use by Emergency Medical Technicians.

Improvement in patient outcomes and the relative simplicity of administering noninvasive ventilation through a simple mask interface has led to the transition of NIV from an ALS to a BLS skill in many EMS systems. Without the availability of NIV, BLS personnel otherwise have limited treatment options to assist ventilation and oxygenation other than supplemental oxygen unless the patient reaches extremis, at which point manual ventilation with a bag-valve-mask is performed.

Wisconsin was the first of several states to examine this issue (28). State officials developed a training program and subsequently implemented a pilot study in 2005 involving BLS use of CPAP. The primary question was to determine if patients who received CPAP by BLS personnel would suffer greater complications than those given CPAP by ALS personnel. After a year of study, the investigators found no difference in rate of administration or complications of CPAP between levels and noted a reduction in the need for ALS intervention in these patients. In several instances, the patients had improved significantly and did not require ALS assistance, thus freeing up ALS resources for other critical calls. This study resulted in Wisconsin becoming the first state in the country to add CPAP to the BLS scope of practice.

Cheskes et al. similarly studied the feasibility of prehospital CPAP use by paramedics trained to the primary care (PCP) level as compared to the advanced care (ACP) level in Ontario, Canada (29). For reference, a PCP possesses training similar to an Advanced EMT in the United States, while an ACP is similar to the U.S. paramedic scope of practice. Training for these providers in CPAP techniques involved 6 hours of didactic, scenario-based training and evaluation. This retrospective observational study was performed in two regions in the province of Ontario over a 1-year period. The authors defined compliance as 100% adherence to the Ontario provincial medical directive, which included specifics of patient presentation, vital signs, and appropriate documentation by the paramedic. A total of 302 cases of CPAP use were included in the study, 212 cases by ACP and 90 cases by PCP. The study identified similar rates of documentation and protocol compliance among these personnel. The authors concluded that CPAP use by PCP-level paramedics may be feasible, but that further studies were needed to determine whether compliance could translate into safety.

We identified only one study that focused on the safety of prehospital use of CPAP by BLS personnel. Sahu et al. performed a retrospective observational study over a 3-year period from 2009 to 2012 of the Delaware BLS CPAP pilot program (30). Providers at included agencies received 4 hours of training; 2 hours didactic and 2 hours hands on as part of this pilot program. In Delaware, BLS personnel arrived on-scene 4 minutes prior to ALS personnel for “respiratory distress” calls 60% of the time, demonstrating an opportunity to initiate early CPAP at the BLS level. The authors aimed to determine whether BLS personnel could appropriately identify patients who would benefit from CPAP, apply the device, and monitor the patient prior to ALS arrival. During the study period, 74 patients had CPAP applied by BLS personnel and CPAP was correctly indicated and applied for 100% of the patients. CPAP was appropriately monitored, and respiratory status appropriately managed, for 98.6% of the patients. Of the 74 patients, 89.2% showed overall improvement after CPAP administration, with 6.8% unchanged, and only 4.1% worsening. Overall, there was an 84% reduction in the proportion of patients with SpO₂ values <92%, a 55% reduction in patients experiencing respiratory rates >24 breaths per minute, and a 58% reduction in cyanosis; all of which were statistically significant. This study concluded that with appropriate training, quality review, and medical oversight, CPAP can be safely used by BLS personnel.

In July 2014, the National Association of State EMS Officials conducted a survey revealing 14 states used CPAP at the BLS level (30). The National EMS Information Systems was also queried at that time and identified that 25 out of 50 US states and territories were using CPAP at the BLS level. In 2019, the National EMS Scope of Practice Model added NIV (both CPAP and BiPAP) to the EMT level (3). Soon after, the national EMS education standards were updated to include NIV for EMTs (31). While there is no randomized controlled trial data available for BLS NIV, we feel that the limited observational data and widespread adoption supports safety of NIV at the BLS level.

Oversight of Noninvasive Ventilation Use

Medical directors must assure adequate training in NIV, including appropriate patient selection, NIV system operation, administration of adjunctive medications, and assessment of clinical response.

Training clinicians for NIV use must address the pathophysiology of various conditions resulting in respiratory failure, appropriately identifying patients who might benefit from NIV and where its use may be contraindicated, and how to successfully operate prehospital NIV systems. It is essential for medical directors to ensure adequate initial and continual education and training is provided to obtain and retain these skills. Protocols must identify clear indications and contraindications for the use of NIV to ensure it is not used in inappropriate circumstances (e.g., unresponsive patients) where adverse events such as aspiration may occur. EMS medical directors must participate in continuous quality improvement activities regularly. The broader principles of airway management training and education are addressed elsewhere in this compendium (32).

Prehospital NIV and Quality Improvement

Medical directors must implement quality assessment and improvement programs to assure optimal application of and outcomes from NIV.

Prehospital NIV requires a robust quality management program to ensure that use improves patient-centered outcomes and does not have unacceptable unintended consequences. Quality improvement processes for NIV use should focus on informing the medical director of the effectiveness of NIV within the specific service and device, as implemented by EMS personnel for their specific patient population. Subsequent observations should guide future training and skill maintenance. A comprehensive treatment of quality improvement in prehospital airway programs is discussed by Vithalani et al. in this compendium (33).

Prehospital NIV and Novel Delivery Methods

Novel NIV methods such as high-flow nasal cannula and helmet ventilation may have a role in prehospital care.

High flow nasal cannula (HFNC), sometimes termed high flow nasal oxygen, and helmet NIV and are two newer technologies that have demonstrated patient-oriented benefit for oxygenating and ventilating hospitalized patients. NIV delivered by helmet uses a collapsible clear bubble placed over the head and secured to a flexible collar that seals around the patient’s neck and is secured below the axilla. Several manufacturers produce such devices, which can be used either by Venturi-method blended air or turbine-driven ventilators (23).

HFNC is a technique that uses a large-bore nasal cannula to deliver heated and humidified oxygen at high flow rates and adjustable FiO₂. In pediatrics, 1-2 liters per kilogram per minute of flow are considered HFNC (34), whereas in adults, 15-60 liters per minute is typical (35,36). The primary benefits of HFNC are improved oxygenation and decreased work of breathing. Though the exact mechanisms of action are not fully understood, it appears that HFNC provides consistent FiO₂ regardless of tidal volume, decreases physiologic dead space via upper airway washout, provides a small amount of PEEP, and may improve mucociliary clearance compared to traditional strategies through reduced desiccation of mucus (35,36).

Low-quality evidence in hospitalized infants and children suggests that HFNC may reduce the need for mask NIV or intubation for a variety of pulmonary conditions (34). HFNC uptake in adults has increased in the past decade, primarily as result of the FLORALI trial (37) and more recently, COVID-19 (38–40). Adult HFNC has demonstrated benefit to patients with hypoxic respiratory failure based on in-hospital studies (35,36). However, very few out-of-hospital studies have been published on HFNC, and none involve adults. Several observational studies have been published of pediatric patients receiving HFNC during interhospital transport by specialist teams (41–45). These studies report HFNC can be used safely in the transport environment and its use has been associated with less need for intubation or other methods of noninvasive ventilation. No significant complications of HFNC use have been reported in this environment.

HFNC requires specific commercial devices for heating and humidification that may present operational challenges for the transport environment and must be connected to a turbine driven air blender or ventilator. These requirements likely limit HFNC to specialized teams performing primarily interfacility transports. Further, high flow rates and oxygen consumption limit the range adult patients can be transported on HFNC. Oxygen consumption calculations and proper arrangements should be undertaken in advance of mission acceptance. The lower flow rates and oxygen consumption used in pediatrics versus adults makes use of out-of-hospital HFNC more practical in children.

Helmet NIV offers several advantages over face mask NIV or HFNC. First, the neck gasket is not vulnerable to facial hair or atypical facial anatomy. Some devices have universal neck gaskets that can be trimmed to fit all patients; therefore, multiple mask sizes are not need. Second, patients appear to tolerate helmet NIV better than face masks (46). Third, helmet devices are less susceptible to air leak at high PEEP (46–48).

However, helmet NIV has several potential limitations in the out-of-hospital environment. The additional dead space of the helmet requires flow rates greater than 60 liters per minute to prevent rebreathing (23,46). Such high flow rates and oxygen consumption will limit transport range. Further, the devices are quite loud, often requiring patients to wear earplugs, thus limiting communication (49). Finally, training and familiarization for EMS personnel and hospital staff must be coordinated to ensure appropriate transitions of care, which may be burdensome.

Limited in-hospital evidence suggests that helmet NIV is at least equivalent to mask NIV (47,48). A single-center, high-quality RCT demonstrated a reduced need for intubation and lower 90-day mortality for ARDS patients treated with helmet versus mask NIV (46). Several small EMS studies have demonstrated safety and efficacy of helmet NIV (49–51). Two Italian studies applied helmet CPAP to a combined 156 patients whom they compared to standard medical therapy with high-flow oxygen, but not mask CPAP, for patients with either hypercarbic respiratory failure or acute pulmonary edema (50,51). They describe no complications, and better patient-oriented outcomes with CPAP including reduced hospital length of stay, need for intubation, and mortality. Beckl offers a descriptive case series of ten patients with COVID-19 transported with helmet CPAP with no complications or need for prehospital intubation (49).

In aggregate, limited but growing evidence suggests that HFNC or helmet NIV may be safely and effectively employed in the out-of-hospital environment (38,49–51). In pediatrics, evidence also exists that HFNC, nasal CPAP, bubble CPAP, and oxygen tent or hood devices may be used for interfacility transports (42,44,45,52,53). Further EMS-specific research on these technologies is needed.

Conclusion

Noninvasive ventilation in the form of CPAP and BiPAP is safe and effective in the prehospital environment. Use at the BLS level has been successfully and safely implemented in many EMS systems. Novel methods of noninvasive ventilation such as HFNC and helmet NIV are promising but require further research to determine optimal patient populations and deployment strategies.