• Tim L Ullrich, Christoph Czernik, Christoph Bührer, Gerd Schmalisch, and Hendrik S Fischer.
• Department of Neonatology, Charité University Medical Center, Berlin, Germany.
• Pediatr. Pulmonol. 2017 Nov 1; 52 (11): 1455-1460.

ObjectiveNasal high-frequency oscillatory ventilation (nHFOV) is a novel mode of non-invasive ventilation used in neonates. However, upper airway obstructions due to viscous secretions have been described as specific adverse effects. We hypothesized that high-frequency oscillations reduce air humidity in the oropharynx, resulting in upper airway desiccation. Therefore, we aimed to investigate the effects of nHFOV ventilatory settings on oropharyngeal gas conditions.MethodsNHFOV or nasal continuous positive airway pressure (nCPAP) was applied, along with heated humidification, to a previously established neonatal bench model that simulates oropharyngeal gas conditions during spontaneous breathing through an open mouth. A digital thermo-hygro sensor measured oropharyngeal temperature (T) and humidity at various nHFOV frequencies (7, 10, 13 Hz), amplitudes (10, 20, 30 cmH2 O), and inspiratory-to-expiratory (I:E) ratios (25:75, 33:66, 50:50), and also during nCPAP.ResultsRelative humidity was always >99%, but nHFOV resulted in lower mean T and absolute humidity (AH) in comparison to nCPAP (P < 0.001). Specifically, decreasing the nHFOV frequency and increasing nHFOV amplitude caused a decline in T and AH (P < 0.001). Mean T and AH were highest during nCPAP (T 34.8 ± 0.6°C, AH 39.3 ± 1.3 g · m-3 ) and lowest during nHFOV at a frequency of 7 Hz and an amplitude of 30 cmH2 O (T 32.4 ± 0.3°C, AH 34.7 ± 0.5 g · m-3 ). Increasing the I:E ratio also reduced T and AH (P = 0.03).ConclusionIntensified nHFOV settings with low frequencies, high amplitudes, and high I:E ratios may place infants at an increased risk of upper airway desiccation. Future studies should investigate strategies to optimize heated humidification during nHFOV.© 2017 Wiley Periodicals, Inc.

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