PETCO2 measured by a new lightweight mainstream capnometer with very low dead space volume offers accurate and reliable noninvasive estimation of PaCO2

Abstract

Objective: Although capnometers are widely used in adult and pediatric intensive care units, they are not widely used in neonatal intensive care units due to issues such as the weight of sensors, dead space, and leakage from tracheal intubation tubes. These authors developed a light and low dead space airway adaptor of end-tidal carbon dioxide pressure (P ET CO 2 ) and evaluated the correlations between P ET CO 2 and partial CO 2 pressure (PaCO 2 ) in rabbits while changing tidal volume and leakage volume. Methods: Firstly, Japanese rabbits weighing 2 kg were divided into three tidal volumes (6 mL/kg, 10 mL/kg, or 15 mL/kg), and P ET CO 2 and PaCO 2 were measured. Secondly, the respiratory apparatus was set to a tidal volume/body weight ratio of 10 mL/kg, leakage rates were divided into seven groups, and P ET CO 2 and PaCO 2 were measured. Results: P ET CO 2 and PaCO 2 were significantly correlated (r 2 = 0.9099, P , 0.0001) when there was no leakage in the tracheal intubation tubes. No significant differences were observed between PaCO 2 and P ET CO 2 (P a-ET CO 2 ) in the three tidal volume/body weight groups or for groups in which leakage rate was ,60%, but significant deviations in P a-ET CO 2 were noted in groups with leakage rate 60%. Conclusion:There was a strong correlation between P ET CO 2 and PaCO 2 when tidal volume/ body weight ratio was 6-15 mL/kg with leakage rate ,60%. Lightweight mainstream capnometer with a low amount of dead space airway adaptor might be useful in very low birth weight infants with small tidal volume.

Effect of tidal volume and end tracheal tube leakage on end-tidal CO2 in very low birth weight infants

“…Figure 2 shows the quadratic discriminant analysis for VT and percentage of ETT leak. The differences between ETCO 2 and PaCO 2 (bias) were compared to the bias of a previous study [ 7 ] to determine the degree of agreement between ETCO 2 and PaCO 2 . A discrimination analysis for the VT and the percentage of ETT leak yielded 70.4% [95% CI, 65.1 to 75.7] discrimination for the agreement between ETCO 2 and PaCO 2 .…”

“…And if the discriminant function is negative ( Z < 0), there is no agreement between ETCO 2 and PaCO 2 . We defined a bias (ETCO 2 –PaCO 2 ) level of −6.74 mmHg as the acceptable lower limit for the difference between ETCO 2 and PaCO 2 based on our previous experiments examining ETCO 2 in rabbits [ 7 ], which showed that the limits of agreement were −6.74 to 4.99 mmHg based on Bland–Altman plots. Values of p < 0.05 were determined to be significant.…”

“…Several investigators have demonstrated that ETCO 2 was in good correlation with PaCO 2 values in infants, including extremely low birth weight infants [ 7 – 12 ]. However, capnography has not been widely accepted by neonatologists for physiological and technical reasons, such as the weight of sensors or water droplets within circuits, dead space, and leakage from tracheal intubation tubes [ 13 , 14 ].…”

Mainstream capnography system for nonintubated children in the postanesthesia care unit: Performance with changing flow rates, and a comparison to side stream capnography

“…The mainstream capnography probe and mask invented by Nihon Kohden have been tested in nonintubated adults (12,13,15). The cap-ONE infant and pediatric masks have been specifically designed for (Figure 1a) (14).…”

A lightweight mainstream capnometer with very low dead space volume is useful monitor for neonates with spontanous and mechanical ventilation: Pilot study

“…We have previously reported a strong correlation between P ET CO 2 and PaCO 2 under controlled ventilation when tidal volume/body weight (TV/BW) was 6 -15 mL/kg and the leakage rate was <60% in rabbits. Furthermore, under conditions of 6 mL/kg of tidal volume (TV), PaCO 2 was significantly increased by a dead space increase of only 1 mL, representing >7% of TV [4].…”