• Jaap W De Vries, Frans B Plötz, and A Johannes Van Vught.
• Department of Anesthesia, Intensive Care and Pain, Mesos Medical Center, PO box 8605, 3503 RP Utrecht, The Netherlands. jwdvries@mesos.nl
• Intensive Care Med. 2002 Sep 1; 28 (9): 1336-9.

ObjectivesTo evaluate the relationship between the arterial end-tidal partial pressure of carbon dioxide (PCO2) difference (deltapCO2) and the degree of desaturation in children with cyanotic heart disease (CHD) and to come to a more reliable estimation of the arterial carbon dioxide partial pressure (PaCO2) from the end-tidal carbon dioxide partial pressure (PET-CO2).Design And SettingIn part retrospective, in part prospective observational study at a university children's hospital.Subjects And InterventionsWe retrospectively assessed the relationship between the arterial oxygen saturation as measured by means of pulse oximetry (SpO2) and the arterial to end-tidal PCO2 differences (deltaPCO2) from the records of medical or surgical interventions in 43 patients with CHD. We derived a PaCO2-PET-CO2 correction formula that was prospectively validated in 34 patients with CHD.Measurements And ResultsIn the retrospective part we found a significant correlation between SpO2 and deltaPCO2 ( r (2)=0.84, p<0.001). The regression equation (corrected PET-CO2=raw PET-CO2-0.36xSpO2+39) was used in the prospective part to calculate the corrected PET-CO2. The r (2)s for the correlations between PaCO(2) and uncorrected and corrected PET-CO2 were 0.17 ( p<0.05) and 0.94 ( p<0.001), respectively. The uncorrected PET-CO2 bias was 13.0 mmHg, the bias +/- 2SDs was -0.1 and 26.2 mmHg. The corrected PET-CO2 bias was -0.6 mmHg, the bias +/- 2SD's was -4.0 and 2.9 mmHg.ConclusionsCorrecting the PET-CO2 for the degree of hypoxia using the SpO2 in artificially ventilated infants and children with CHD results in a clinically applicable estimation of the PaCO2. As both SpO2 and PET-CO2 can be monitored continuously and non-invasively, this could facilitate artificial ventilation management in children with CHD.

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