Correlation of end-tidal carbon dioxide with arterial carbon dioxide among patients in neurosurgical intensive care unit / 中华创伤杂志

ABSTRACT

Objective To examine the correlation between end-tidal carbon dioxide (PetCO2) and arterial CO2 (PaCO2) among patients admitted in neurosurgical intensive care unit (NICU) and the factors affecting the PaCO2-PetCO2 [P (a-et) CO2].Methods Thirty-two intubated or cut-trachea patients who presented in the NICU were enrolled.Arterial blood gas test was done at seven every morning,and values of PetCO2 were compared with simultaneously recorded PaCO2.The normal gap of P (a-et) CO2 was defined as-5 mmHg to 5 mmHg.Concordance between PaCO2 and PetCO2 was analyzed using the Bland-Altman plot.Parameters between the normal and high P(a-et) CO2 groups were compared to identify the factors affecting the P(a-et) CO2,including Glasgow Coma Scale(GCS),blood pressure (BP),heart rate (HR),respiration rate (RR),body temperature (BT),and pulse oxygen saturation (SpO2).Results Allvalues of PaCO2 and PetCO2 were in accordance with normal distribution (r =0.668,P ＜ 0.01) and concordance between PaCO2 and PetCO2 was 69.8％.Patients who had high P(aet) CO2 showed lower initial GCS,lower instant GCS,BT,as well as pH and higher actual bicarbonate (AB) and PetCO2 than the patients with normal P (a-et) CO2.Correlation between PaCO2 and PetCO2 rapidly declined when positive end expiratory pressure(PEEP) was greater than 5 mmH2O(r =0.229,P ＜ 0.01).Conclusions PetCO2 correlates well with PaCO2 and appears to be a useful monitor of respiratory function of the patients consecutively.Initial GCS,BT,AB and PEEP have an impact on P(a-et) CO2,so those factors should be considered when attempting to monitor the hyperventilation with PetCO2.