Resistance of Colorimetric Carbon Dioxide Detectors Commonly Utilized in Neonates

BACKGROUND: Colorimetric end-tidal carbon dioxide (ETCO₂) detectors can identify airway obstruction during noninvasive ventilation and successful intubation during newborn resuscitation. The resistance of these devices is not well described, and the information provided by manufacturers is incomplete.

METHODS: We compared the resistance of 3 colorimetric ETCO₂ detectors (Neo-StatCO₂, Pedi-Cap, and Mini StatCO₂,) and 2 mainstream capnograph sensors (EMMA infant airway adapter 17449 and neonatal/infant airway adapter YG-213T). Endotracheal tubes, 2.5–4.0-mm inner diameter (Portex) were measured as a reference range. A differential pressure transducer was placed between the device and a T-piece resuscitator. The other side of the device was open to air. Resistance to flow was tested at 1–10 L/min. Resistance was calculated as the change in pressure over change in flow and expressed as cm H₂O/L/s.

RESULTS: There was a significantly higher mean resistance across all flows tested for the Neo-StatCO₂ compared with the other ETCO₂ devices (P < .001). There was a 6-fold difference between the least and most resistive colorimetric detectors. At the commonly utilized flow of 10 L/min, the resistance of the Neo-StatCO₂ was 61.1 cm H₂O/L/s, comparable with that of a 3.0 endotracheal tube, which we measured at 62.7 cm H₂O/L/s. The resistance values of the Pedi-Cap and Mini StatCO₂ were 9.9 and 8.4 cm H₂O/L/s, respectively. Those of the EMMA and YG-213T were 7.1 and 2.6 cm H₂O/L/s, respectively.

CONCLUSIONS: We found significant differences in resistance between devices used to detect ETCO₂ during resuscitation of premature infants. Future trials are needed to determine the effects of this resistance on work of breathing, particularly on very premature newborns receiving mask CPAP.