Simulated model revealed significant continuous positive airway pressure fluctuations with facemasks

There is an ongoing debate about whether facemasks or binasal prongs provide the optimal respiratory interface.1 It has been suggested that prongs provide more stable target continuous positive airway pressure (CPAP). Explanations for the possible inferiority of facemasks have included mask leaks and airway obstructions, due to inadequate mask seals or poor positioning activating the trigeminocardiac reflex.2 This German simulated patient study compared pressure variances during CPAP mode using a facemask or binasal prongs and explored the influence the operator had on mask position and the resulting CPAP dynamics. We configured a NALM Neonatal Active Lung Model (Dr Schaller Medizintechnik, Dresden, Germany) to emulate a 1000-g preterm infant, with a respiratory rate of 80/min, tidal volume of 4.5 mL, compliance of 1 mL/kPa and inspiration time of 30 ms. A 3D-printed nasopharyngeal space dummy was created using a transparent AR-M2 photopolymer (PFM medical, Koeln, Germany). It was connected to a Perivent CPAP device (Fisher & Paykel Healthcare, Auckland, New Zealand) using a 35 mm neonatal facemask (Fisher & Paykel) or equivalent size M prongs (Fitz Stephan GmbH, Gackenbach, Germany). The New Life Box acquisition system (Advanced Life Diagnostics UG, Weener, Germany) eliminated mask leaks, by detecting the flow and pressure through a sensor, with a dead space of 0.7 mL and precision of ±5%. This was located between the facemask or prongs and the CPAP system. We recruited 16 medical personnel with previous or no previous experience of using the two methods. The operators were blinded, as they did not receive any information regarding potential mask leak or the actual applied pressure determined in the simulated patient. Their only source of information was the display on the Perivent device. They were instructed to maintain the facemask over the mouth and nose for two periods of 45 s and apply a pressure of 5 cmH2O. We measured the pressure at the y piece at the beginning of the intervention, and after 5 s, and the pressure and volume fluctuations once a simulated intrinsic respiratory pattern had been initiated during simulated breathing, using the NALM TDM file. This was imported into Excel version 1808 (Microsoft Corp, Washington, USA) using TDM Importer Version 21.3.049496 (National Instruments, Texas, USA). Ventilation breaths were defined and analysed based on the decrease in pressure at the y piece during expiration and its increase during inspiration. The pressure level and its fluctuations, namely the minimum and maximum pressure at the y piece, were calculated using custom scripts in Matlab R2022b (Natick, Massachusetts, USA). The t-test was used for the statistical assessment of the attained pressure levels. Levene's test was used to compare variances between the facemask and prong conditions across the operators. The analysis comprised 1600 ventilator breaths during 64 respiratory cycles with no mask leaks. Each of the 16 operators performed two procedures with the facemask. In analogy, 32 cycles with the binasal prongs were performed. The mean target CPAP with the facemask was 5.0 cmH2O and the operators achieved 5.4 ± 0.41 cmH2O. Pronounced fluctuations for individual operators were detected during CPAP after the intrinsic respiratory pattern was initiative, after 5 s at steady state. The mean variation in the pressure at the y piece was 3.0 cmH2O. Particularly, noteworthy variations were observed among individual operators, resulting in a migration of respiratory loops along the x-axis during respiratory cycles (Figure 1). The standard deviation for pressure at the y piece in individual breaths during the mask applications were up to 16 times higher than those observed with the binasal prongs: ΔPmin-max 0.40–0.48 versus 0.03–0.03 cmH2O, respectively, (p < 0.001). Significant differences in the coefficient of variation were observed between the 5 experienced and 11 inexperienced operators: ΔPmin–max 0.45–0.55 versus 0.37–0.44, respectively (p < 0.001). Until now, failures in neonatal respiratory support have been attributed to a limited number of factors, such as leaks at the mask interface, which may be deemed the primary cause, the trigeminocardiac reflex and airway obstruction.2 It is noteworthy that the trigeminocardiac reflex3 may not just be attributable to the patient as it may be more plausibly correlated with variable facemask positions. One study documented varying levels of force during the facemask application, particularly elevated positive pressure ventilation, and their correlation with apnoea and bradycardia during neonatal transition.4 Substantial CPAP fluctuations may be linked to facemask positioning, particularly the pressure exerted on the mask. The influence this would have on the magnitude and stability of CPAP levels has not been previously addressed. Our findings highlight the challenges associated with maintaining consistent CPAP levels during real-life scenarios, as significant changes in the pressure on the ventilation mask during initial care are highly likely. In addition, operators cannot consistently be reassured by the target CPAP displayed on the ventilation device. A comprehensive understanding of the impact of differently applied facemasks seems essential. When recommending them as the first-line treatment during neonatal transition.5 Our simulated data reveal previously undetected, but significant, CPAP fluctuations with facemasks. These fluctuations could provide an additional factor that explains CPAP failure and suggests that using binasal prongs could be preferable. However, further research is needed. Hanna Sterzik: Conceptualization; investigation; writing – review and editing; visualization; data curation; software; formal analysis. Matthias Kumpf: Conceptualization; investigation; writing – review and editing; supervision; data curation; validation. Christian F. Poets: Writing – review and editing; validation; methodology; supervision. Bianca Haase: Conceptualization; investigation; funding acquisition; writing – original draft; data curation; methodology; software; formal analysis; visualization; writing – review and editing. Open Access funding enabled and organized by Projekt DEAL. BH works as a consultant for PFM Cologne. CFP has received funding from Fritz Stephan GmbH and Loewenstein Medical. The other authors have no conflicts of interest to declare. STEP files for 3D-printed nasopharyngeal space dummies are available upon reasonable request.