Nasal high flow (NHF) is an efficient oxygenation tool for the treatment of respiratory failure. The study investigated the effect of breathing pattern on positive airway pressure and dead-space clearance by NHF. The breathing cycle during NHF was characterized in 27 patients with acute respiratory failure (ARF), stable COPD and after mechanical ventilation (post-MV) via tracheostomy where also pressure was measured in the trachea. Dead-space clearance was measured in airway models during different breathing patterns. NHF reduced the respiratory rate (RR) and TI/TE through prolonging the TE; the TI/TE ranged between ≤0.5 observed in the COPD patients and ~1.0 in the ARF patients. NHF via standard medium-sized cannula generated a low-level expiratory pressure proportional to NHF rate and breathing flow; the median generated PEEP was only 1.71 cmH2O at NHF 45 L/min. The dilution and purging of expired gas from a nasal cavity model were observed to occur at the end of expiration as the expiratory flow slowed and the dynamic pressure decreased. The higher RR with shorter end-expiratory period resulted in reduced dead-space clearance by NHF; 20 L/min cleared 43±2 ml at RR 15 min-1 vs. 9±5 ml at RR 45 min-1, P<0.001, which was increased at higher NHF rate. At lower RR the clearance was similar across the range of NHF rates 20 - 60 L/min. Higher NHF elevates positive airway pressure and at the increased RR can improve the clearance. This may enhance gas exchange and lead to a reduction in the work of breathing.

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Background: The use of Bubble Continuous Positive Airway Pressure (BCPAP) and High Flow Nasal Cannula (HFNC) in premature infants post extubation are two of the numerous modalities to prevent re-intubation in this fragile population. However, there is a lack of studies that evaluates these modalities in 32 weekers or less post extubation. Therefore, the purpose of this study was to evaluate re-intubation rate within the first 72, 48, and 36 hours post extubation in 32 weekers or less admitted to the neonatal intensive care unit (NICU) using BCPAP and/or HFNC. Method: This was a retrospective study in a level 4 NICU Children's Hospital in Southern California from the following years January 2015 to May 2020. Inclusion criteria were: 1) 24-32 weekers, 2: On BCPAP, 3: and/or HFNC. Primary outcome measure was reintubation within 72 hours. Re-intubation was also assessed at the 48 and 36-hours interval. Subjects were divided into three groups for comparison: Group1: BCPAP, Group2: HFNC, Group3: Both (both modalities were used during selected time frame). Results: A total 392 subjects met the inclusion criteria. Mean ± Standard Deviation for Gestational Age was 27.95 ± 2.54 weeks, Length of Stay (LOS) was 83.31 ± 44.18 days (median=82.5; quartile range=62.5). Patients characteristics were: 114 (29.8%) had patent ductus arteriosus, 82 (20.92%) had respiratory failure, 36 (9.18%) had respiratory distress syndrome, 33 (8.42%) had bronchopulmonary dysplasia, 30 (7.65%) had anemia of prematurity, 23 (5.87%) had apnea of prematurity, and 6 (1.53%) had acute respiratory distress. Within 72 hours of extubation, 77 (19.6%) were re-intubated (n=7 (19.44%) in BCPAP; n=20 (23.53%) in HFNC; and n=50 (18.45%) in both. Within 48 hours of extubation,71 (18%) were re-intubated (n=7 (19.44%) in BCPAP; n=18 (21.2%) in HFNC; and n=46 (17%) in both. Within 36 hours of extubation,67 (17%) were re-intubated (n=6 (16.67%) in BCPAP; n=17 (20%) in HFNC; and n=44 (16.24%) in both. Chi-Square within all reported time intervals 72, 48, and 36 hours showed no significant difference between groups, p>0.05. A significant difference was found in mean LOS between groups (p<0.0001) and specifically between HFNC and BCPAP (mean difference=45.43, standard error=7.90, p<0.0001), Table 1. Conclusion: In this preliminary analysis, the use of BCPAP compared to HFNC showed no significant difference in re-intubation rates at the 72, 48, or 36-hours interval. However, LOS was noted to be significantly lower in the BCPAP group. Further analysis and studies are needed to investigate this further.

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