691 - Pharyngeal Pressures Delivered by CPAP and Nasal High Flow in Preterm Infants as Continuously Measured over Several Days by a New Monitoring Device

Publication Number: 4675.691

Amy Yu, The Royal Women's Hospital, Pascoe Vale, Victoria, Australia; Alison G. Martin, Royal Women's Hospital Melbourne, Parkville, Victoria, Australia; Edward Buijs, The Royal Women's Hospital, Melbourne, Melbourne, Victoria, Australia; Kai Heinemann, The University of Melbourne, Melbourne, Victoria, Australia; Kate Hodgson, Royal Women’s Hospital, Parkville, Victoria, Australia; Christiane Theda, Royal Women's Hospital, Parkville, Victoria, Australia

Background: Non-invasive respiratory support methods such as continuous positive airway pressure (CPAP) and nasal high flow therapy (HF) are widely used in neonatal intensive care. However, leaks (system or patient) and variable nasal resistance create uncertainty in the actual pressures delivered to the upper airways. CPAP has a set target pressure, while HF relies on loose-fitting nasal cannula, resulting in variable pressure delivery. Previous studies have investigated pharyngeal pressures (Pp) delivered by CPAP/HF for short durations, but prolonged measurement data remain limited.

Objective: To continuously measure delivered Pp over several (3-8) days in infants receiving CPAP or HF, using a novel Airway Pressure Monitor (APM) prototype device. Secondary aims are to identify factors influencing Pp delivery (eg. interface type, pressure/flow settings) and evaluate intra-patient variability during periods of unchanged respiratory support.

Design/Methods: This ongoing observational feasibility study supports development of the APM device, by continuously measuring Pp in infants (≥1kg) receiving CPAP or HF. The APM device employs a study-specific dual-lumen gastric feeding tube (nasal or oral) with a side port positioned at the pharynx to measure Pp, while feeding continues via the primary lumen. Pp data is continuously acquired, processed for signal quality, converted to a rolling mean pressure and compared with set CPAP or HF levels to characterise variability in delivered pressure.

Results: Preliminary data are presented (study ongoing; completion anticipated before PAS 2026). Figure 1 shows the distribution of delivered mean Pp relative to the set CPAP (n=10). Delivered Pp was within ±0.5cmH2O of the set pressure for 34% of the time, >0.5cmH2O above for 23% and >0.5cmH2O below for 43%. Figure 2 displays delivered mean Pp during HF (flows 4-8L/min). Both modalities exhibited marked intra-patient variability in delivered mean Pp despite constant support settings. Further analysis (not shown) includes the effect of CPAP interface type (mask/prongs) and other clinical factors on delivered Pp.

Conclusion(s): Delivered pharyngeal pressures in neonates are variable for both CPAP and HF, due to controlled parameters such as pressure/flow setting and interface type (data not shown) and uncontrolled parameters (such as leak). In this study, HF consistently generated lower pressures than CPAP. The prototype device performed well and continuous monitoring of airway pressure is clinically feasible, may provide new insights into non-invasive respiratory support and could guide more consistent pressure delivery in neonatal care.

Figure 1: CPAP - Distribution of Delivered Mean Pharyngeal Pressure Relative to Set Pressure
Figure 1: Distribution of delivered pharyngeal pressure relative to set CPAP level. Bars represent aggregate data across all study CPAP participants, showing the proportion of time, the delivered pharyngeal pressure was at a specific pressure level (+/- 0.5 cmH2O) relative to set pressure. Dotted lines are individual participant profiles.

Figure 2: Nasal High Flow - Delivered Mean Pharyngeal Pressure vs Set Flow
Figure 2: Delivered mean pharyngeal pressure across set high flow levels (4-8 L/min). Each box represents inter-patient variability in mean delivered pressure at a given flow rate.