Abstract
To determine whether end-tidal PCO2 (PETCO2) measurements obtained with two infrared capnometers accurately approximates the arterial PCO2 PaCO2) in critically ill neonates, simultaneous measurements of PETCO2 were obtained from the distal and proximal ends of the tracheal tube with a sidestream capnometer (Puritan Bennett/Datex — BP/D) and from the proximal end with a mainstream capnometer (Hewlett-Packard — HP) in 20 intubated neonates. Distal sidestream PETCO2 and mainstream PetCO2 correlated with the PaCO2 (r2 = 0.66 and 0.61, respectively) within the range of 26–57 mmHg PaCO2. However, proximal PETCO2 with the sidestream capnometer correlated very poorly (r2 = 0.09) with PaCO2. The slope of the least square regression line for the distal sidestream capnometer, 0.67, was significantly less than that for the mainstream capnometer, 0.78 but both were significantly greater than that for the proximal sidestream capnometer, 0.39 (P < 0.05). The slope of the regression for the proximal sidestream capnometer did not differ significantly from horizontal. Insertion of the mainstream sensor for the HP capnometer significantly increased the transcutaneous CO2 when compared with preinsertion values. We conclude that both distal sidestream and mainstream capnometry provide accurate estimates of the PaCO2 in critically ill neonates.
Résumé
En enregistrant simultanément la PCO2 en fin d’expiration (PETCO2) par capnomètre aspirant (Puritan Bennett/Datex —PB/D) à partir du bout distal et du bout proximal d’un tube endotrachéal et par capnomètre passif (Hewlett-Packard — HP) au bout proximal du tube, nous avons mesuré l’efficacité de ces techniques d’estimation à l’infrarouge de la PCO2 artérielle (PaCO2) chez 20 nouveauxnés. Pour des PaCO2 de l’ordre de 26 à 57 mmHg, la pente de la ligne de régression entre la PETCO2 et la PaCO2 était de 0,78 avec le capnomètre passif (r2 = 0,61), significativement plus grande que la pente de 0,67 du capnomètre aspirant au bout distal (r2 = 0,66) mais toutes deux se détachaient (P < 0,05) de celle du capnomètre aspirant au bout proximal qui, avec une valeur de 0,39, pouvait être confondue avec l’horizontale (r2 = 0,09). Pour sa part, l’insertion dans le circuit de la fenêtre de mesure du capnomètre passif contribuait à augmenter la PCO2 transcutanée. La capnométrie passive ou par aspiration du bout distal donne donc un bon estimé de la PaCO2 des nouveauxnés gravement malades.
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McEvedy, B.A.B., McLeod, M.E., Kirpalani, H. et al. End-tidal carbon dioxide measurements in critically ill neonates: a comparison of side-stream and mainstream capnometers. Can J Anaesth 37, 322–326 (1990). https://doi.org/10.1007/BF03005583
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DOI: https://doi.org/10.1007/BF03005583