Deposition studies of aerosol delivery by nasal cannula to infants.

AIM: Nasal cannulas are used to provide oxygen support for infants and have been considered as a means for delivering aerosols to the lungs. To measure mucociliary clearance in the lungs of infants with congenital heart defects, we delivered radiopharmaceutical aerosols via a nasal cannula. Here we report on the pulmonary and nasal deposition of these aerosols. METHOD: A total of 18 infants (median age = 26 days; quartiles = 11-74 days) performed clearance measurements soon before or after corrective cardiac surgery. The regional aerosol deposition was assessed using gamma camera imaging. RESULTS: Cannula flow rate significantly affected pulmonary dosing. Flow rates useful for oxygen support were associated with low pulmonary deposition (2 L/min; mean, 4.5% of deposited dose; range, 2%-9%; n = 7) and high nasal deposition. Much lower cannula flow rates increased the pulmonary deposition (0.2 L/min; mean, 33.5% of deposited dose; range, 15%-51%; n = 5; P = 0.005 vs 2 L/min). The ratio of nose/lung dosing was approximately 26:1 at 2 L/min and 2:1 at 0.2 L/min. Bench studies demonstrated cannula output rates of 10.2 ± 1.7% (2 L/min) and 3.3 ± 0.4% (0.2 L/min) of the loaded nebulizer dose during a 2-minute delivery. Combining in vitro and in vivo results, we estimate that 0.46% of the loaded nebulizer dose reaches the lungs at 2 L/min vs 1.10% at 0.2 L/min during a 2-minute delivery. CONCLUSION: With the delivery system used here, pulmonary aerosol delivery via nasal cannula was very inefficient at the flow rates required to provide oxygen support. Even at low flows, nasal deposition was substantial and local toxicity must be considered.

Helium-oxygen therapy for infants with bronchiolitis: a randomized controlled trial.

OBJECTIVE: To compare nebulized racemic epinephrine delivered by 70% helium and 30% oxygen or 100% oxygen followed by helium-oxygen inhalation therapy via high-flow nasal cannula (HFNC) vs oxygen inhalation via HFNC in the treatment of bronchiolitis. DESIGN: Prospective, randomized, controlled, single-blind trial. SETTING: This study was conducted from October 1, 2004, through May 31, 2008, in the emergency department of an urban, tertiary care children's hospital. Patients Infants aged 2 to 12 months with a Modified Wood's Clinical Asthma Score (M-WCAS) of 3 or higher. INTERVENTIONS: Patients initially received nebulized albuterol treatment driven by 100% oxygen. Patients were randomized to the helium-oxygen or oxygen group and received nebulized racemic epinephrine via a face mask. After nebulization, humidified helium-oxygen or oxygen was delivered by HFNC. After 60 minutes of inhalation therapy, patients with an M-WCAS of 2 or higher received a second delivery of nebulized racemic epinephrine followed by helium-oxygen or oxygen delivered by HFNC. Main Outcome Measure Degree of improvement of M-WCAS for 240 minutes or until emergency department discharge. RESULTS: Of 69 infants enrolled, 34 were randomized to the helium-oxygen group and 35 to the oxygen group. The mean change in M-WCAS from baseline to 240 minutes or emergency department discharge was 1.84 for the helium-oxygen group compared with 0.31 for the oxygen group (P < .001). The mean M-WCAS was significantly improved for the helium-oxygen group compared with the oxygen group at 60 minutes (P = .005), 120 minutes (P < .001), 180 minutes (P < .001), and 240 minutes (P < .001). CONCLUSION: Nebulized racemic epinephrine delivered by helium-oxygen followed by helium-oxygen inhalation therapy delivered by HFNC was associated with a greater degree of clinical improvement compared with that delivered by oxygen among infants with bronchiolitis. Trial Registration clinicaltrials.gov Identifier: NCT00116584.

Aerosol delivery through nasal cannulas: an in vitro study.

In most circumstances, a nasal route for the delivery of pulmonary aerosol medications is rarely considered; however, in specific instances, this route may be quite useful. Consider, for example, the delivery of aerosol treatments during humidified high-flow nasal cannula use in pediatric critical care, or continuous aerosol delivery via cannula for medications with short durations of action. The goal of this study was to evaluate the potential for delivering aerosols via nasal cannula through in vitro studies of aerosol output and size. The system utilized for testing included an Aerogen Solo nebulizer downstream of a heater/humidifier system, followed by a nasal cannula and an aerosol collection apparatus. Adult, pediatric, and infant cannulas were tested with and without an inhalation-only breathing simulator. The cannulas were driven by 3 lpm (50 psig) oxygen flows. Dose quantification was performed using radioisotope techniques. Total cannula output and system losses were measured. Aerosol size measurements were made from the nebulizer, from the heating tube, and from the prongs of the adult and pediatric cannulas, using laser-diffraction techniques. Total cannula output ranged from 8.4-25.1% and 18.6-26.9% of loaded dose, without and with the addition of inhalation flows. Volume median diameters were 2.2 +/- 0.2 microm from the adult cannula and 1.9 +/- 0.3 microm from the pediatric cannula. Ninety percent of the aerosol volume was in sizes smaller than 4.2 +/- 0.4 microm (adult) and 3.8 +/- 0.5 microm (pediatric). System losses were highest in the nebulizer-humidifier connectors, heated tube, and humidifier. Losses in the nebulizer were very low (2.2-3.5%). This study demonstrates that aerosols can be efficiently delivered through a humidified high-flow nasal cannula system. Further study is required to determine if this route is viable for pulmonary delivery.

Helium/oxygen-driven albuterol nebulization in the treatment of children with moderate to severe asthma exacerbations: a randomized, controlled trial.

BACKGROUND: Helium and oxygen mixtures (heliox) increase both pulmonary aerosol delivery and gas delivery relative to oxygen. We aimed to compare the effectiveness of a 70%:30% helium/oxygen (heliox)-driven continuous aerosol delivery versus 100% oxygen-driven delivery in the treatment of asthmatic children with moderate to severe exacerbations. METHODS: We enrolled 30 children aged 2 to 18 years who presented to an urban, pediatric emergency department (ED) with moderate to severe asthma as defined by a pulmonary index (PI) score of > or =8. PI scores can range from 0 to 15. In this randomized, controlled, single-blind trial conducted in a convenience sample of children, all patients in the trial received an initial nebulized albuterol (5 mg) treatment driven by 100% oxygen and a dose of oral prednisone or prednisolone. Subsequently, patients were randomly assigned to receive continuously nebulized albuterol (15 mg/hour) delivered by either heliox or oxygen using a nonrebreathing face mask. The primary outcome measure was degree of improvement as assessed in blinded video-recorded PI scores over 240 minutes (at 30-minute intervals for the first 3 hours) or until ED discharge (if <240 minutes). RESULTS: The mean change in PI score from baseline to 240 minutes or ED discharge was 6.67 for the heliox group compared with 3.33 for the oxygen group. Eleven (73%) patients in the heliox group were discharged from the hospital in <12 hours compared with 5 (33%) patients in the conventional group. CONCLUSION: Continuously nebulized albuterol delivered by heliox was associated with a greater degree of clinical improvement compared with that delivered by oxygen among children with moderate to severe asthma exacerbations.