Evaluation of a mainstream capnometer and end-tidal carbon dioxide monitoring in mechanically ventilated infants^†

We evaluated a new lightweight capnometer with a < 1 mL deadspace neonatal airway adapter and endotracheal tube connector unit (NAC) for use in mechanically ventilated neonates. The evaluation consisted of: 1) a bench test comparison of air flow resistance between the standard endotracheal tube and connector with the new NAC (flow rates, 1.5 to 12.8 L/min); 2) a determination of the effect of NAC placement on Pa; 3) pre- and post-NAC pulmonary mechanics; and 4) an analysis of paired Pet and Pa in 16 infants requiring mechanical ventilation. Paired t test of the slopes of the resistance curves was significant (P = 0.002) while analysis of variance of differential pressures was not (P = 0.29). All post-NAC placement Pa were smaller than pre-placement values; there were no differences in pulmonary mechanics, and Pet correlated closely with Pa (n = 132, r = 0.79) defined as Pet = 0.68 • Pa + 5.21; x̄ ± 1 SD, Pa–Pet was 4.7 ± 4.7 torr and Pet/Pa was 0.86 ± 0.14. Pediatr Pulmonal 1990; 9:254–259.