Comparison between Central Venous Carbon Dioxide and End Tidal Carbon Dioxide as Surrogate to Arterial Carbon Dioxide During Spontaneous Breath Trial of Mechanically Ventilated COPD Patients

Abstract

During spontaneous breath trial (SBT) for COPD patients, monitoring of PCO2 level may be required to assure adequate ventilation before the decision of extubation. An arterial blood gas (ABG) provides important information during weaning process. However, obtaining an ABG may be extremely difficult in some patients and it may cause serious complications such as arterial injury and is more painful than venous sampling. The aim of this study is to compare central venous CO2 and end tidal CO2 as a less invasive and accurate surrogate to arterial CO2 during spontaneous breath trial (SBT) of mechanically ventilated COPD patients as a weaning method from mechanical ventilation. This study was conducted on 62 of mechanically ventilated COPD patients at the Respiratory Intensive Care Unit of Abbassia Chest Hospital. In this study, 77.4% of the patients were males and 22.6% were females. The mean of age was 64.3years. The special habits detected among the studied cases were tobacco smoking. The most common co-morbidities associated with COPD in the studied cases were diabetes (19.4%),hypertension (30.6%), ischemic heart disease (11.3%), chronic liver disease (1.6%) and old pulmonary TB (4.8%). The outcome of spontaneous breath trial (SBT) of the studied cases was (83.9%) passed 2 hours of successful SBT and extubated for at least 48 hours and (16.1%) with failed SBT and not extubated. The mortality rate of the studied cases was (74.2%) lived after 2 hours successful SBT and successful extubation for at least 48 hours and (25.8%) died after failed SBT and failed extubation. In this study the average mean differences (MD) between arterial and central venous PCO2 values at the start of SBT was 4.5±2.2 mmHg, and at the end of SBT was 5.9±2.1mmHg, with significant positive correlation between them (p<0.001). In this study the average mean differences (MD) between arterial and end tidal CO2 values at the start of SBT was 3.4±1.9 mmHg, and at the end of SBT was 4.2±2.2mmHg, with significant positive correlation between them (p<0.001). In this study the average mean differences (MD) between central venous PCO2 and end tidal PCO2 values at the start of SBT was 3.1±0.4mmHg, and at the end of SBT was 3.4±0.4mmHg, with significant positive correlation between them (p<0.001).