Acute Effect of E-Cigarette Inhalation on Mucociliary Clearance in E-Cigarette Users.

Background: Recent studies show e-cigarette (EC) users have increased rates of chronic bronchitic symptoms that may be associated with depressed mucociliary clearance (MCC). Little is known about the acute or chronic effects of EC inhalation on in vivo MCC. Methods: In vivo MCC was measured in young adult vapers (n = 5 males, mean age = 21) after controlled inhalation of a radiolabeled (Tc99m sulfur colloid) aerosol. Whole-lung clearance of radiolabeled deposited particles was measured over a 90-minute period for baseline MCC and associated with controlled periodic vaping over the first 60 minutes of MCC measurements. The vaping challenge was administered from a fourth generation box mod EC containing unflavored e-liquid (65% propylene glycol/35% vegetable glycerin, 3 mg/mL freebase nicotine). The challenge was administered at the start of each 10-minute interval of MCC measurements and consisted of 1 puff every 30 seconds for 5 minutes (i.e., 10 puffs for each 10-minute period for a total of 60 puffs during the initial 60 minutes of MCC measurements). Results: Compared with baseline, peripheral lung average clearance (%) over the 90 minutes of MCC measures was enhanced, associated with EC challenge, 12 (±6) versus 24 (±6), respectively (p < 0.05 by Wilcoxon signed-rank test). Conclusions: Acute enhancement of in vivo MCC during EC challenge is contrary to recent studies showing nicotine-associated slowing of ciliary beat and mucus transport at higher nicotine levels than those used here. However, our findings are consistent with an acute increase in fluid volume and mucin secretion to the bronchial airway surface that is likely short lived. Research reported in this publication was supported by the National Institutes of Health R01HL139369 and registered with ClinicalTrials.gov (NCT03700892).

The effects of flow settings during high-flow nasal cannula oxygen therapy for neonates and young children.

BACKGROUND: During neonatal and paediatric high-flow nasal cannula therapy, optimising the flow setting is crucial for favourable physiological and clinical outcomes. However, considerable variability exists in clinical practice regarding initial flows and subsequent adjustments for these patients. Our review aimed to summarise the impact of various flows during high-flow nasal cannula treatment in neonates and children. METHODS: Two investigators independently searched PubMed, Embase, Web of Science, Scopus and Cochrane for in vitro and in vivo studies published in English before 30 April 2023. Studies enrolling adults (≥18 years) or those using a single flow setting were excluded. Data extraction and risk of bias assessments were performed independently by two investigators. The study protocol was prospectively registered with PROSPERO (CRD42022345419). RESULTS: 38 406 studies were identified, with 44 included. In vitro studies explored flow settings' effects on airway pressures, humidity and carbon dioxide clearance; all were flow-dependent. Observational clinical studies consistently reported that higher flows led to increased pharyngeal pressure and potentially increased intrathoracic airway pressure (especially among neonates), improved oxygenation, and reduced respiratory rate and work of breathing up to a certain threshold. Three randomised controlled trials found no significant differences in treatment failure among different flow settings. Flow impacts exhibited significant heterogeneity among different patients. CONCLUSION: Individualising flow settings in neonates and young children requires consideration of the patient's peak inspiratory flow, respiratory rate, heart rate, tolerance, work of breathing and lung aeration for optimal care.