Redesign of an open-system oxygen face mask with mainstream capnometer for children

Abstract

BACKGROUND: Partial pressure of end-tidal carbon dioxide (PETCO2) monitoring in children is important to detect apnea or hypopnea early to intervene before hypoxemia develops. Monitoring PETCO2 in children without a tracheal tube is challenging. To improve PETCO2 measurement accuracy in a commercially available mask with a mainstream CO2 detector, we implemented design changes with deform-and-hold shaping technology and anterior-posterior adjustment of the expiratory gas flow cup. METHODS: Two sizes of redesigned face masks (small for 7–20 kg, medium for 10–40 kg) were evaluated. Initial bench testing used a simulator modeling a spontaneously breathing infant and child with a natural airway. An infant/child manikin head was connected to the breathing lung simulator. A mass flow controller provided expiratory CO2. Mask fit was then evaluated on healthy human subjects to identify anatomical features associated with good fit, defined as square shape capnography waveform during expiration. A 3-dimensional digital scan was used to quantify anatomical features. The gaps between face mask rims and facial surface were manually measured. RESULTS: Bench testing revealed a PETCO2 difference of 3.4 ± 1.5 mm Hg between a measured PETCO2 by the redesigned mask and CO2 concentration at trachea, as compared with 6.7 ± 6.2 mm Hg between PETCO2 measured by nasal cannula and trachea (P