Reservoir Cannulas for Pediatric Oxygen Therapy: A Proof-of-Concept Study

Aerosol Delivery Efficiency With High-Flow Nasal Cannula Therapy in Neonatal, Pediatric, and Adult Nasal Upper-Airway and Lung Models

BACKGROUND

High-flow nasal cannula (HFNC) systems employ different methods to provide aerosol to patients. This study compared delivery efficiency, particle size, and regional deposition of aerosolized bronchodilators during HFNC in neonatal, pediatric, and adult upper-airway and lung models between a proximal aerosol adapter and distal aerosol circuit chamber.

METHODS

A filter was connected to the upper airway to a spontaneously breathing lung model. Albuterol was nebulized using the aerosol adapter and circuit at different clinical flow settings. The aerosol mass deposited in the upper airway and lung was quantified. Particle size was measured with a laser diffractometer. Regional deposition was assessed with a gamma camera at each nebulizer location and patient model with minimum flow settings.

RESULTS

Inhaled lung doses ranged from 0.2-0.8% for neonates, 0.2-2.2% for the small child, and 0.5-5.2% for the adult models. Neonatal inhaled lung doses were not different between the aerosol circuit and adapter, but the aerosol circuit showed marginally greater lung doses in the pediatric and adult patient models. Impacted aerosols and condensation in the non-heated HFNC and aerosol delivery components contributed to the dispersion of coarse liquid droplets, high deposition (11-44%), and occlusion of the supine neonatal upper airway. In contrast, the upright pediatric and adult upper-airway models had minimal deposition (0.3-7.0%) and high fugitive losses (∼24%) from liquid droplets leaking out of the nose. The high impactive losses in the aerosol adapter (56%) were better contained than in the aerosol circuit, resulting in less cannula sputter (5% vs 22%), fewer fugitive losses (18% vs 24%), and smaller inhaled aerosols (5 µm vs 13 µm).

CONCLUSIONS

The inhaled lung dose was low (1-5%) during HFNC. Approaches that streamline aerosol delivery are needed to provide safe and effective therapy to patients receiving aerosolized medications with this HFNC system.

Efficacy and safety of oxygen-sparing nasal reservoir cannula for treatment of pediatric hypoxemic pneumonia in Uganda: a pilot randomized clinical trial

Background

Oxygen is an essential therapy for hypoxemia but is scarce in low-income settings. Oxygen conserving devices optimize delivery, but to date have been designed for adults in high-income settings. Here we present the development and clinical pilot study of an oxygen-sparing nasal reservoir cannula (OSNRC) for pediatric use in low-income settings.

Methods

(1) Pre-clinical development of a novel OSNRC using a simulated respiratory circuit with metabolic simulator and anatomically accurate face-airway models. Simulated breathing waveforms were designed based on airway resistance, lung compliance, respiratory rate, and tidal volume of spontaneous breathing for three disease conditions. (2) Pilot, randomized, controlled, non-blinded, cross-over study of the OSNRC vs standard nasal cannula (SNC) among children hospitalized with hypoxemic pneumonia in Uganda. Eight children were randomized to OSNRC followed by SNC, and eight were randomized to SNC followed by OSNRC.

Results

The laboratory simulation showed that the OSNRC provided the same or higher fraction of inspired oxygen at approximately 2.5-times lower flow rate compared to SNC. The flow savings ratio exhibited a linear relationship with the OSNRC volume to tidal volume ratio with a slope that varied with breathing waveforms. The range of performance from different breathing waveforms defined a performance envelope of the OSNRC. Two mask sizes (30 mL and 50 mL) provided sufficient coverage for patients between the 3rd and 97th percentile in our targeted age range. In the clinical pilot study, the rise in capillary blood pCO₂ was similar in the OSNRC and SNC groups, suggesting that the OSNRC was not associated with CO₂ retention. There were no significant differences between OSNRC and SNC with respect to clinical adverse events, lactate levels, pH, and SpO₂. The OSNRC group had a higher mean SpO₂ than the SNC group (adjusted mean difference, 1.4, 95% confidence interval 1.1 to 1.8), showing oxygen delivery enhancement.

Conclusion

The OSNRC enhances oxygen delivery without causing CO₂ retention and appears to be well-tolerated by pediatric patients. If safety, efficacy and tolerability are confirmed in larger trials, this device has the potential to optimize oxygen delivery in children in low-resource settings, reducing the global burden of pediatric pneumonia.

Trial registration

The trial was retrospectively registered (International Standard Registered Clinical/Social Study Number (ISRCTN): 15216845; Date of registration: 15 July 2020).

Bubble CPAP devices for infants and children in resource-limited settings: review of the literature

Background: Early management of respiratory distress is critical to reducing mortality in infants and children in resource-limited settings. Bubble continuous positive airway pressure (bCPAP) can offer effective and affordable non-invasive respiratory support. Objective: To determine the best physical components of bubble CPAP circuits for respiratory support of children in low-resource settings. Methods: Using PubMed, CINAHL and LILACS, studies of any design in any language published before June 2017 which examined the physical components of bCPAP circuits were identified and reviewed. Results: After screening, the review included 45 articles: 17 clinical trials, 11 literature reviews, 10 technical assessments of bCPAP components, three reports of real-world implementation in low-resource settings, three cost analyses and one case report. There is no ideal bCPAP circuit for all settings and patients, but some choices are generally better than others in designing a circuit for low-resource settings. Oxygen concentrators are usually the best source of oxygen. As yet, there is no affordable and accurate oxygen blender. Nasal prongs are the simplest patient interface to use with the fewest complications but are not the cheapest option. Expiratory limbs should be at least 1 cm in diameter. Home-made pressure generators are effective, safe and affordable. Conclusion: This narrative review found many studies which evaluated the real clinical outcomes with bCPAP in the target population as well as technical comparison of bCPAP components. However, many studies were not blinded or randomised and there was significant heterogeneity in design and outcome measures. Abbreviations: bCPAP, bubble continuous positive airway pressure; CPAP, continuous positive airway pressure; FiO₂, fractional oxygen concentration; HFNC, high-flow nasal cannula; HIC, high-income countries; LMIC, low- and middle-income countries; NP, nasopharyngeal; O₂, oxygen; PEEP, positive end-expiratory pressure; PICO, Population, Intervention, Comparison and Outcome.