Swallowing during provision of helmet ventilation: Review and provisional multidisciplinary guidance

Abstract

Use of noninvasive ventilation provided by a helmet increased globally during and after the COVID-19 pandemic. This approach may reduce need for intubation and its associated clinical complications in critically ill patients. Use of helmet interface minimizes virus aerosolization while enabling verbal communication, oral feeding and coughing/expectoration of secretions during its administration. Although improved oral hydration is a recognized benefit of helmet NIV, relatively little is known about the safety and efficiency of swallowing during helmet NIV. Risk of aspiration is a key consideration given the fragile pulmonary status of critically ill patients requiring respiratory support, and therefore the decision to initiate oral intake is best made based on multidisciplinary input. We reviewed the current published evidence on NIV and its effects on upper airway physiology and swallowing function. We then presented a case example demonstrating preservation of swallowing performance with helmet NIV. Last, we offer provisional multidisciplinary guidance for clinical practice, and provide directions for future research.

Introduction

An external interface is required to provide positive pressure during noninvasive ventilation (NIV). Several interface types are available (e.g. full face mask, oronasal mask, helmet, or nasal). Interface selection is based on patient preference, tolerance considering the possible upper airway obstruction, type and/or level of respiratory distress, and ventilation mode (e.g. PSV or CPAP).^1,2 Facial and oronasal masks are more likely to generate aerosols, potentially increasing the risk of viral transmission and clinician exposure. ³ As a result, a helmet interface was designed to serve as a physical barrier, reducing exposure to airborne particles during NIV.^4,5

The helmet is a transparent plastic hood that covers the patient’s head, similar in structure to a clinician’s powered air-purifying respirator (PAPR). ⁶ Different from a PAPR, the helmet is connected to a ventilator through inspiratory and expiratory ports rather than a portable powered air filter. Helmet NIV has assumed a growing role in caring for critically ill patients with acute respiratory distress syndrome (ARDS),^{7 –9} especially using pressure support ventilation (PSV) and noninvasive continuous positive airway pressure ventilation (CPAP), avoiding many adverse effects of prolonged invasive mechanical ventilation.^10,11

Compared with facial masks, the helmet can be equally effective for treating ARDS ¹² and may reduce intubation rate, clinical complications, and mortality.^7,13 Other potential benefits compared to facial masks include reduced risk of device related pressure injuries, less eye irritation, and reduced air leakage. ¹⁴

In addition to delivering NIV to patients with ARDS (resulting from the SARS-CoV-2 virus or other etiologies), helmet ventilation can be used for patients with acute cardiogenic pulmonary edema, exacerbation of chronic obstructive pulmonary disease (COPD) ¹⁴ and neuromuscular disorders, ¹⁵ both inside and outside the intensive care unit (ICU), including home care. The benefits of improved tolerability and reduced risk of aerosolization apply to any airborne or droplet-transmissible disease.^3,4,7 The helmet interface is beneficial for those patients who require healthcare professionals in close proximity for safe ambulation, transport, or medical procedures such as nasal/laryngeal endoscopy.

Helmet NIV enables patients to speak, consume oral intake, cough, and expectorate pulmonary secretions during active ventilation.^13,14 A soft rubber collar is fitted to the neck that pneumatically seals and prevents air leakage.^{3 –5} In addition, access ports can be used for emergency procedures (e.g. delivery of oxygen in the event of hypoxia), insertion of suction catheters, delivery of nutrition via feeding tubes, and use of straws for oral feeding and hydration while using helmet NIV (Figure 1).^4,5,13,14

Figure 1.

Helmet schematics.

Although the advantages of oral feeding and hydration during helmet ventilation have previously been noted,^4,5,13,14 no prior studies have addressed the safety and efficiency of swallowing in patients who receive NIV with a helmet, nor are there published guidelines to inform clinical practice in this population. As a result, this work presents a case example that illustrates the feasibility of instrumental swallowing assessment, as well as our preliminary experience with oral feeding during helmet NIV. Following, our review discusses the available evidence on swallowing and NIV, presents data on the known effects of helmet ventilation on swallowing physiology; and discusses the possible implications of these findings for oral feeding in critically ill patients receiving helmet NIV. Lastly, we offer provisional multidisciplinary guidance for swallowing with helmet NIV and propose future research directions.

Methods

Case example

To analyze the feasibility of instrumental swallowing assessment during helmet NIV and describe the possible effects of helmet NIV on swallowing function, we assessed a 53-year-old woman with bilateral vocal cord paralysis and dysphonia after a thyroidectomy performed 3 years ago. The patient had not used helmet ventilation previously and had no critical illness. At the time of this study, she had a functional swallow and normal respiratory parameters, tolerating a normal diet and thin liquids. The presentation of this case example was approved by the institutional review board (Code: 3981050).

We performed the Videofluoroscopic Swallowing Study (VFSS) using the OEC-9900-Elite-Mobile-C-arm (GE-Healthcare, USA), recording 30 frames per second; the patient was instructed to swallow (a) one self-regulated sip and (b) sequential swallows of thin liquid barium sulfate (Bariogel^®, Cristália, Brazil) self-administered from a straw. The patient remained seated in a 90° upright position, and the VFSS images were captured only in the lateral view.

The swallowing tasks were performed under two conditions:

• (a) First, swallowing was assessed during baseline ventilation (without helmet).

• (b) Second, swallowing was evaluated while using the helmet. For this purpose, was used a 7lives helmet (Agile Med, Brazil) connected to a Synchrony II BiPAP (Philips Respironics, USA) in continuous positive airway pressure (CPAP) mode set to 10 cm H₂O with 21% FiO₂.

To compare swallowing function between the two conditions, we used two validated outcome tools: the Penetration-Aspiration Scale (PAS) ¹⁶ for assessment of airway invasion and patient response (range: 1–8; normal = PAS ⩽ 2) and the Modified Barium Swallow Impairment Profile (MBSImP) ¹⁷ a clinical tool used to score the severity of oropharyngeal swallowing and esophageal clearance (component score range: 0–4; 0 = unimpaired, 4 severe).

To evaluate the effect of the helmet CPAP on swallowing, two blinded speech-language pathologists (SLP) with MBSImP registrations independently analyzed the videos using a scoring form. Both SLPs had experience in the management of dysphagia with ⩾5 years experience in performing/analyzing VFSS (SLP 1 = 14 years; SLP 2 = 6 years). Disagreement was reconciled by a third SLP evaluator (SLP 3 = 8 years experience). A descriptive analysis was performed to compare swallowing results with and without helmet CPAP.

Multidisciplinary guidance

To generate a multidisciplinary guidance, a modified Delphi structure was used. The lead researchers (JV and MBB) collected the initial questions through a review of the literature, prepared a semi-structured document and presented it to the experts to begin the search process. ¹⁸ The bibliographic research also made it possible to establish a list of references that served as central bibliographic material for preparing the recommendations. The lead author convened an international multidisciplinary team of experts to collaborate in developing a consensus, each with a minimum of 12 years experience (range 12–22 years). This team had specialization from diverse disciplines involved in NIV, swallowing, and dysphagia; participants were from professions of respiratory therapy, SLPs, nursing, and otolaryngology–head and neck surgery, each with relevant publications.

Round 1

The modified Delphi method consisted of two rounds and were carried out between February and September 2022. Voting in both rounds took place electronically (i.e. email discussion, editing a shared document). Anonymity was not maintained. In round 1, the team had access to a document that included a clear explanation of the study objectives and specific instructions for participation, the literature search, the case study, and some draft guidelines prepared by the lead researchers (JV and MBB). All contributors were able to offer guidance, make comments, and suggest additional items supported by their own clinical experience and available evidence. Afterward, team members examined each recommendation according to a binary decision (“agree” or “disagree”). Statements that did not reach 100% agreement were modified according to the feedback provided and redistributed by the organizers for the second round.

Round 2

The second round included discussion of discrepancies electronically to refine recommendations. Panel members provided clarification on each issue and presented evidence-based (i.e. literature, experience) arguments to justify their points of view. Participants discussed the remaining statements until unanimous consensus was reached to maintain, modify, or eliminate the statement from the final guidance document. All recommendations were approved by 100% of the expert panel. Finally, the lead researchers convened a video conference to present the final results and structure the final content of the manuscript.

Results and discussion

Case presentation and literature review

In this case presentation, swallowing assessment using VFSS was feasible, accessible, and safe during helmet ventilation. Specifically, it was possible to analyze 14 of 17 MBSimP components (see Table 1). Since the anteroposterior view was not possible to assess, and solid food could not be introduced into the helmet, components 3, 13, and 17 (bolus preparation/mastication, pharyngeal contraction, and esophageal clearance, respectively) were not assessed. When comparing swallowing outcomes (i.e. MBSImP and PAS) with and without helmet CPAP, the two blinded SLPs agreed 100% on the changes observed in both testing conditions.

Table 1.

MBSImP components assessed (green) and not assessed (red) with the helmet NIV.

The table shows the MBSImP components evaluated (green) and not evaluated (red) with the VNI helmet.

As a result, helmet CPAP showed mixed effects on the oral phase of swallowing, specifically, MBSImP components 2 (hold position/tongue control) and 6 (initiation of the pharyngeal swallow) showed lower scores compared to baseline ventilation (baseline ventilation score: 1; helmet CPAP score: 0 for both components). Additionally, component 1 (lip closure) was negatively affected (baseline ventilation score: 0; helmet CPAP score: 1). Regarding the pharyngeal phase of swallowing, no change was observed in MBSImP components and PAS scores with the use of the helmet CPAP (PAS 2 in all conditions).

Our case example showed that the helmet CPAP can have both positive (better hold position/lingual control and initiation of swallowing) and negative effects (impaired lip closure) on the oral phase of swallowing. These encouraging findings with helmet CPAP differ from those with nasal CPAP, inhibiting swallowing initiation. ¹⁹ Previous studies have suggested that the pressure provided by full-face mask CPAP may aid in swallowing initiation, improve breathing-swallowing coordination, and decrease the risk of aspiration. These benefits occurred both in healthy individuals ²⁰ and in individuals with COPD, ²¹ suggesting that CPAP may offer positive swallowing effects in patients with COPD who aspirate. ²¹ Unlike our study, previous research on CPAP and swallowing modifications did not use a gold standard method, such as videofluoroscopy or Flexible Endoscopic Evaluation of Swallowing (FEES), to analyze swallowing physiology during NIV. There remains a knowledge gap about the effects of different forms of NIV on swallowing physiology. We assessed an adult female with a functional swallow; therefore, we do not know the effects, if any, a helmet CPAP might have on swallowing in patients with dysphagia, critical illness and/or respiratory conditions.

Previously, it was proposed that pressures generated during NIV might distort or deform pharyngeal and laryngeal structures as lung volumes increased,^19,22 and it was postulated that these alterations could alter swallowing. ²³ However, in the case evaluated in this study, no impairment of swallowing safety or efficiency was observed during helmet CPAP. Swallowing function was preserved during sequential sips of thin liquid, a type of swallowing task that is considered challenging, complex, and sensitive for detecting aspiration risk. ²⁴ We emphasize that these results do not necessarily generalize to critically ill patients—our focus was on feasibility of swallowing assessment with the helmet in place. Patients with ARDS or other critical illnesses are likely to have impaired neurocognitive status, diminished pulmonary reserve, and greatly reduced compensatory mechanisms for adapting to alterations in airflow. ²⁵ Patients with prior intubation also have a high incidence of laryngotracheal pressure injuries,^{26 –29} and may manifest generalized ventilator-associated muscle atrophy ³⁰ or other effects from the cumulative doses of sedation.^{29 –32}

Similar to what has been observed for other respiratory support with low pressure, such as a high-flow nasal cannula (HFNC), our findings suggest that a patient without critical/respiratory illness can likely adapt their pharyngeal swallowing during helmet CPAP.^23,33,34 As seen in our case example, the HFNC can also modify some parameters of the oral phase of swallowing, such as lip closure ³³ ; but the clinical relevance of the lip closure impairment observed during helmet use is not important (baseline ventilation score: 0; helmet CPAP score: 1) and does not necessarily demonstrate an important deviation in the swallowing function. However, parallels between the studies with HFNC and our helmet CPAP study should be interpreted with caution, due the pressure provided during HFNC is much lower than that generated during NIV. In addition, studies on HFNC have used cups to supply liquids during swallowing trials, unlike our case example in which it was only possible to evaluate liquids consumed via a straw. These data do not allow for firm conclusions on how NIV provided by a helmetalters swallowing function. Direct evidence testing swallowing with helmet NIV in a cohort of critical patients is warranted.

Multidisciplinary considerations

Little is known about how the positive pressure delivered by a helmet affects the upper aerodigestive tract; therefore, the timing for initiation of an oral diet should be based on a comprehensive patient assessment.

Clinicians should assess the risks and benefits of oral intake in patients using helmet NIV. Table 2 presents the assessment considerations between non-helmet/regular assessment and helmet NIV assessment. Assessment begins with a thorough medical chart review, including pertinent medical history. The clinician should assess the number, grade and duration of orotracheal intubations (including endotracheal tube size used); length of hospital stay; current medications; cumulative effects of sedation; respiratory status; cognitive, neuromuscular, and pulmonary condition (including cough strength); and the state of mobility and general weakness.

Table 2.

Assessment considerations between typical clinical/instrumental swallowing assessment with and without helmet NIV.

Procedure	Non-helmet/typical assessment	Helmet assessment
Clinical swallowing assessment	Cervical auscultation, laryngeal palpation, and comprehensive orofacial physical examinations (e.g. tactile feedback of lip and tongue force/pressure, masseter, and temporalis contraction with biting) may be performed. Trials of different viscosities of foods and liquids are possible. Changes in voice quality and physiological status (e.g. respiratory rate) after swallow, as well as visual examination of the oral cavity for residue can be considered.	The helmet restricts comprehensive physical examination of the head and neck area, limiting assessments to visual observation of the muscles at rest, during speech, and during swallowing. Just trials with liquids can be performed and straws can be used for these purposes. Changes in voice quality and physiological status (e.g. respiratory rate) after swallow, as well as visual examination of the oral cavity for residue can be considered too.
Videofluoroscopy swallowing study (VFSS)	Trial of different viscosities of foods and liquids, offered by different utensils (e.g. spoon, fork, straw, cup).	Liquids can only be offered through a straw. Clinicians can use straws with different diameters, allowing the introduction of liquids with different viscosities and volumes.
Flexible endoscopic evaluation of swallowing (FEES)	Endoscopic evaluation allows visualization of the anatomy and function of the upper aerodigestive tract while all types of foods and liquids can be visualized. Aerosol and droplet exposure risks are present.	The flexible endoscope is introduced through the feeding tube port (Figure 2), allowing the clinician to assess the structures of the upper aerodigestive tract and permitting visualization of secretions, saliva, and liquids with low aerosol and droplet production.

Clinical assessment in patients with helmet NIV is limited due to the plastic hood that covers the patient’s head. For example, testing the sensory integrity of cranial nerve V’s three branches (i.e. V1, V2, and V3) is not possible. Moreover, it only permits the assessment of liquid consistencies via straw because there is no port/window to administer drink or food in any other manner. Instrumental assessments of swallowing using straws (e.g. VFSS, FEES) remain the standard of practice for all patients who use a helmet.

The helmet permits safe transfer of patients with infectious respiratory diseases, such as COVID-19, to the radiology suite by limiting aerosolization risk. FEES may be considered as well, given its portability and ability to determine the laryngeal effects of orotracheal intubation. The flexible scope can be introduced through the same port used for the passage of the feeding tube without the need for the removal of the helmet, thereby minimizing aerosolization (Figure 2). Discussion with the multidisciplinary team may facilitate decision-making about the patient’s readiness to start a liquid diet orally. This may be especially beneficial for surgical patients not ready for solid food diets.

Figure 2.

Frontal and lateral images during the flexible endoscopic evaluation of swallowing with helmet non-invasive ventilation. Individual pictured is not a patient.

Limitations

Although our work is a useful starting point for moving our practice forward, it has limitations. For example, we assessed the swallowing of a single individual who had functional swallowing and was not dependent on NIV; therefore, these results may not be generalizable to populations of critically ill patients or patients with acute or chronic respiratory diseases who use NIV. In addition, this patient performed relatively few swallowing trials during a short period without increasing or decreasing the CPAP pressure settings. Our review did not include a systematic method for searching and synthesizing available evidence. Furthermore, the multidisciplinary guidance offered here reflects experts’ opinion, not validated methods for developing guidelines or expert consensus statements. Despite these shortcomings, this work provides direction for future research.

Future Directions

It will be necessary to investigate the impact of changes in mode of ventilation within the helmet NIV environment and its other interfaces (e.g. oro-nasal mask, nasal cannula) on swallowing physiology using instrumental methods such as VFSS and FEES. Especially, an endoscopic evaluation, such as the FEES, may provide additional information about the upper aerodigestive tract and anatomical changes associated with continuous pressure in the upper aerodigestive tract. Furthermore, it is relevant that future research evaluates the swallowing of critically ill patients who receive NIV by helmet, especially those with swallowing disorders. These assessments should include a significant number of swallowing trials to reliably simulate normal eating with NIV, during which the patient would need to compensate for the positive airway pressure over longer durations during mealtime. Finally, future studies should explore the effects of the helmet NIV on different ventilation modes, such as CPAP and PSV.

Conclusions

Our experience with Helmet CPAP showed mixed effects on oral swallow function but did not impair airway protection during feeding. Based on our experience and what we have reviewed, decisions for initiating oral intake should be based on thorough patient history and examination, evidence-based protocols that incorporate clinical and/or instrumental assessments, and collaborative decision making with a multidisciplinary team. Future studies should focus on the methods and clinical use of helmet NIV in patients with dysphagia.