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   CO   2; 3) pre‐ and post‐NAC pulmonary mechanics; and 4) an analysis of paired Pet   CO   2and Pa   CO   2in 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   CO   2were smaller than pre‐placement values; there were no differences in pulmonary mechanics, and Pet   CO   2correlated closely with Pa   CO   2(n = 132, r = 0.79) defined as Pet   CO   2= 0.68 • Pa   CO   2+ 5.21; x̄ ± 1 SD, Pa   CO   2–Pet   CO   2was 4.7 ± 4.7 torr and Pet   CO   2/Pa   CO   2was 0.86 ± 0.14. Pediatr Pulmonal 1990; 9:254–259 .