How to deliver aerosolized medications through high flow nasal cannula safely and effectively in the era of COVID-19 and beyond: A narrative review.

BACKGROUND: The treatments of COVID-19 involve some degree of uncertainty. Current evidence also shows mixed findings with regards to bioaerosol dispersion and airborne transmission of COVID-19 during high flow nasal cannula (HFNC) therapy. While coping with this global pandemic created hot debates on the use of HFNC, it is important to bring detached opinions and current evidence to the attention of health care professionals (HCPs) who may need to use HFNC in patients with COVID-19. AIM: The purpose of this paper is to provide a framework on the selection, placement, and use of nebulizers as well as HFNC prongs, gas flow, and delivery technique via HFNC to help clinicians deliver aerosolized medications through HFNC safely and effectively in the era of COVID-19 and beyond. METHODS: We searched PubMed, Medline, CINAHL, and Science Direct to identify studies on aerosol drug delivery through HFNC using the following keywords: ("aerosols," OR "nebulizers") AND ("high flow nasal cannula" OR "high flow oxygen therapy" OR "HFNC") AND ("COVID-19," OR "SARS-CoV-2"). Twenty-eight articles including in vitro studies, randomized clinical trials, scintigraphy studies, review articles, prospective and retrospective research were included in this review. DISCUSSION AND RESULTS: It is not clear if the findings of the previous studies on bacterial contamination could be applied to viral transmission because they do not provide data that could be extrapolated to the risk of SARS-CoV-2 transmission. In the face of the unknown risk with the transmission of COVID-19 during HFNC therapy, the benefits of HFNC must be weighed against the risk of infection to HCPs and other patients. Due to the limited number of ventilators available in hospitals and the confirmed effectiveness of HFNC in treating hypoxemic respiratory failure, HFNC may prevent early intubation, and prolonged intensive care unit stays in patients with COVID-19. CONCLUSION: Clinicians should review the magnitude of this risk based on current evidence and use the suggested strategies of this paper for safe and effective delivery of aerosolized medications through HFNC in the era of COVID-19 and beyond.

Quantifying continuous nebulization via high flow nasal cannula and large volume nebulizer in a pediatric model.

BACKGROUND: Use of high flow nasal cannula (HFNC) to deliver aerosolized medications to children has gained considerable interest. However, data on continuous albuterol delivery (CAD) via HFNC are lacking. This study quantified CAD via HFNC/vibrating mesh nebulizer (VMN) and large-volume jet nebulizer (LVN) with face mask (FM) in a pediatric model. Aerosol delivery with two HFNC cannula designs were also compared. METHODS: A pediatric manikin was connected to a lung simulator (Vt = 150 mL, RR = 28 breaths/minute, I:E 1:2.4) via collecting filter at the carina. XL Pediatric and SML Adult HFNC designs were tested to determine optimal cannula design for CAD. VMN was placed Before humidifier (37°C), albuterol (5 mg/mL) was nebulized at 3, 6, and 12 L/minute (n = 3). To compare HFNC/VMN with LVN and FM, albuterol (15 mg/hour) was aerosolized for 3 hours/device (n = 3). LVN was connected to FM and filled with 9 mL of albuterol (5 mg/mL) and 66 mL of normal saline to deliver 25 mL/hour at 13 L/minute. VMN was connected to the infusion pump to deliver 7.5 mL/hr of albuterol (2 mg/mL). Drug eluted from filters was assayed with UV spectrophotometry (276 nm). RESULTS: Optimal aerosol delivery occurred at 3 L/minute (12.6% ± 0.5%) with SML Adult HFNC (P = .04). When used for CAD, inhaled drug delivery with HFNC/VMN (2.2 mg/hr ± 0.1, 14.8% ± 0.7%) was significantly greater than LVN and FM (0.48 ± 0.09 mg/hour, 3.2% ± 0.6%) (P = .001). CONCLUSIONS: Administration of CAD via HFNC/VMN led to a greater than fourfold increase in drug delivery compared to LVN with FM. Optimal aerosol delivery occurred at 3 L/minute with SML Adult HFNC.

Clinical Efficacy of Vibrating Mesh and Jet Nebulizers With Different Interfaces in Pediatric Subjects With Asthma.

BACKGROUND: Nebulizers are commonly used in emergency departments to deliver bronchodilators to children with asthma exacerbations. However, no clinical study comparing a vibrating mesh nebulizer with a jet nebulizer is available in this patient population. The purpose of this study was to compare the clinical efficacy of a vibrating mesh nebulizer to a jet nebulizer combined with a mouthpiece or mask in children with asthma exacerbations admitted to the emergency department. METHODS: We conducted a single-blinded randomized clinical trial of 217 children (2-18 y old) with a moderate to severe asthma exacerbation in the emergency department. Assessment of severity was defined by our acute asthma score, adapted from the Pediatric Asthma Score. Subjects were randomized to receive bronchodilator treatment via vibrating mesh nebulizer (n = 108) or jet nebulizer (n = 109) and were treated until they achieved a mild asthma score and were discharged or until a decision to admit was made. All subjects were treated per our acute asthma clinical pathway algorithm for the emergency department with modifications to allow for blinding, assessment of treatment, and data collection. Outcome variables included hospital admission rate, number of treatments, and time to mild asthma score. RESULTS: There was a significant difference in baseline asthma score between subjects treated with the vibrating mesh nebulizer and those treated with the jet nebulizer (P = .042), but no other significant differences in demographics existed between groups. To adjust for effect of baseline asthma score, a multiple logistic regression model was used to model admission. The vibrating mesh nebulizer group had a lower probability of being admitted to the hospital (P = .062), and they required significantly fewer treatments (P < .001) and less time to reach a mild asthma score (P = .004) than those in the jet nebulizer group. In subjects with a mask interface, the vibrating mesh nebulizer significantly reduced the probability of admission (P = .032). CONCLUSIONS: Subjects treated with a vibrating mesh nebulizer required significantly fewer treatments and less time to achieve a mild asthma score. In subjects with a mask interface, the vibrating mesh nebulizer significantly reduced the probability of admission compared to jet nebulizer. (ClinicalTrials.gov registration NCT02774941.).