A Modified Aerosol Mask Could Significantly Save Oxygen Supplies during SARS COV 2 Pandemic.

Dear Editor:

Coronavirus disease (COVID-19) is predominantly a respiratory illness that can evolve to hypoxemic respiratory failure. In those cases, oxygen therapy is used as first-line treatment and is still the most supportive treatment of the disease. Therefore, oxygen supply is key for an effective health care response, and meeting the surging oxygen demand is vital during the COVID-19 emergency. Of note, the World Health Organization recently published an interim guide on oxygen source and distribution during the COVID-19 pandemic, estimating that an average of 90 m3 of oxygen per hour would be necessary to cover the needs of a hospital managing 100 concurrent COVID-19 cases.

Unfortunately, epidemic waves have put health care systems under stress, and oxygen supply scarcity has been encountered in some regions of the world, such as India, Africa and Latin America. Oxygen supply and oxygen-saving strategies are thus of utmost importance for those regions.

To treat severe hypoxemia, the main systems currently used are the non-rebreathing mask or high flow nasal oxygen. However, these systems consume large amounts of oxygen and have thus limited usefulness in places where hospital capacities are overwhelmed and oxygen storages have been depleted.

The Modified Aerosol Mask (MAM) is an original handmade oxygen delivery system that can be self-assembled with few and easily available disposables. Indeed, the MAM is made of 1 aerosol mask onto which 2 pieces of corrugated tubing (15 cm length) are connected (Figure 1 ). The whole system is placed above the classical nasal cannula (NC), which remains the source of oxygen distribution. During expiration, the continuous oxygen flow from the NC is collected in the 2 tubes instead of being immediately dispersed into the room. During the next inspiration, the patient will receive, when inspiratory flow exceeds NC flow, this oxygen-enriched gas mixture from the tubes instead of atmospheric room air. Of course, once the tidal volume exceeds the mask and tubing volume (210 mL), atmospheric air will penetrate the tubes and will be inspired by the patient. In doing so, the increased dead space from the corrugated tubes of the MAM theoretically acts as a collector of wasted oxygen during the expiratory phase or in the case of mouth breathing (Figure 2 ). This set up may have the advantage of increasing the fraction of inspired oxygen for a given oxygen flow delivered by NC, without clinically significant arterial CO2 increase. Hence, for this fraction of inspired oxygen, the addition of the MAM allows lower oxygen flows and thereby saves oxygen supplies. The MAM can spare up to 50% of oxygen flow while preserving a target arterial oxygen pressure. This mask is an experimental prototype, used under an emergency exemption and with approval from the two main ethics committees of our country. The device has not yet been approved for use in the United States. The MAM can be used with either oxygen cylinders or oxygen concentrators. This device could thus be valuable in those countries in need of enormous amounts of oxygen and undergoing actual oxygen scarcity. In addition to hospital use, an online video tutorial (shared by a Quick Response-code on oxygen bottles) or documentation included with oxygen bottles could allow implementation of this simple device among the population for at-home care. In addition to saving oxygen, proper use of this device could have a significant economic impact on and reduce the risk of catastrophic health expenditure faced by families taking care of their relatives at home because of overwhelmed hospitals.—Duprez F, PT, RT, PhD, ICU Epicura Hospital Hornu Belgium and Laboratory of Motion and Respiratory Physiology Condorcet School, Tournai, Belgium; De Terwangne Ch, MD, PhDs, Deparment of Geriatric Medicine, Université Catholique de Louvain, Brussels, Belgium; Poncin W, RT, PhD, Service de Pneumologie, Cliniques; and secteur de Kinésithérapie et Ergothérapie, Cliniques Universitaires Saint-Luc, Brussels, Belgium; Bruyneel A, RN, CCRN, PhDs, Health Economics, Hospital Management and Nursing Research Department, School of Public Health, Université Libre de Bruxelles, Brussels, Belgium. Twitter: @ArnaudBruyneel. ORCID identifier: https://orcid.org/0000-0001-6276-2762; De Greef J, MD, PhDs, Service de Médecine Interne et Maladies Infectieuses, Cliniques Universitaires Saint-Luc, Brussels, Belgium and Louvain Centre for Toxicology and Applied Pharmacology, Institut de Recherche Expérimentale et Clinique (IREC), Université Catholique de Louvain, Brussels, Belgium; and Wittebole X, MD, PhD, ICU, Cliniques Universitaires Saint-Luc, Brussels, Belgium.

FIGURE 1

(A) Subject receiving low flow oxygen by classical NC. (B) The first image depicts the MAM: a classical aerosol mask with 2 lateral holes on which 2 corrugated tubes ISO (tube radius 22 mm ± 15 cm length for adult) are connected. The second image depicts a subject with a MAM and classical NC (subject always receives oxygen low flow by classical NC). MAM, Modified Aerosol Mask; NC, nasal cannula; ISO, International Organization for Standardization.

FIGURE 2

How does MAM work? During expiration (left side), the continuous oxygen flow from the nasal cannula is collected in the 2 tubes instead of being immediately (with expiratory CO2) dispersed into the room. During the next inspiration (right side), the patient receives this oxygen-enriched gas mixture from the tubes instead of atmospheric room air. MAM, Modified Aerosol Mask; CO2, carbon dioxide; O2, oxygen.