Monitoring carbon dioxide in
mechanically ventilated patients during hyperbaric treatmen
BACKGROUND: Measurement of the arterial carbon dioxide
(PaCO2) is an established part of the monitoring of mechanically ventilated
patients. Other ways to get information about carbon dioxide in the patient are
measurement of end-tidal carbon dioxide (PETCO2) and transcutaneous carbon
dioxide (PTCCO2). Carbon dioxide in the blood and cerebral tissue has great
influence on vasoactivity and thereby blood volume of the brain. We have found
no studies on the correlation between PETCO2 or PTCCO2, and PaCO2 during
hyperbaric oxygen therapy (HBOT).
METHOD: We studied 10 intubated and ventilatory stable patients during HBOT. End-tidal and transcutaneous measurements provided continuous data. Arterial blood samples were collected after reaching the operational pressure of 284 kPa (2.8 ATA) and analysed outside the chamber. A total of 17 paired samples of PETCO2, PTCCO2 and PaCO2 were obtained.
RESULTS: There was a good correlation between PETCO2 and PaCO2 using linear regression (r2 = 0.83). Bland-Altman analysis showed that PETCO2 on average was 2.22 kPa higher than PaCO2 with limits of agreement (LoA) at ± 2.4 kPa. PTCCO2, on average, was 2.16 kPa lower than PaCO2 and the correlation using linear regression was poor (r2 = 0.24). Bland-Altman analysis revealed LoA at ± 3.2 kPa.
CONCLUSION: During hyperbaric conditions we found that PETCO2 as opposed to PTCCO2 offered the greater precision, but there was great variability among patients. Care must be taken when using PETCO2 or PTCCO2 as an estimate of PaCO2.
METHOD: We studied 10 intubated and ventilatory stable patients during HBOT. End-tidal and transcutaneous measurements provided continuous data. Arterial blood samples were collected after reaching the operational pressure of 284 kPa (2.8 ATA) and analysed outside the chamber. A total of 17 paired samples of PETCO2, PTCCO2 and PaCO2 were obtained.
RESULTS: There was a good correlation between PETCO2 and PaCO2 using linear regression (r2 = 0.83). Bland-Altman analysis showed that PETCO2 on average was 2.22 kPa higher than PaCO2 with limits of agreement (LoA) at ± 2.4 kPa. PTCCO2, on average, was 2.16 kPa lower than PaCO2 and the correlation using linear regression was poor (r2 = 0.24). Bland-Altman analysis revealed LoA at ± 3.2 kPa.
CONCLUSION: During hyperbaric conditions we found that PETCO2 as opposed to PTCCO2 offered the greater precision, but there was great variability among patients. Care must be taken when using PETCO2 or PTCCO2 as an estimate of PaCO2.
Ditayangkan
ulang olh dr.Erick Supondha (Hyperbaric&Diving Medicine Consultant) Jakarta
Indonesia, hyperbaric&diving medicine hotline 021 99070050.
www.indodivinghealth.com
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