The Significance of Transcutaneous Continuous Overnight CO(2) Monitoring in Determining Initial Mechanical Ventilator Application for Patients with Neuromuscular Disease

OBJECTIVE: To reveal the significance of continuous transcutaneous carbon dioxide (CO(2)) level monitoring through reviewing cases which showed a discrepancy in CO(2) levels between arterial blood gas analysis (ABGA) and continuous transcutaneous blood gas monitoring. METHOD: Medical record review was conducted retrospectively of patients with neuromuscular diseases who had started home mechanical ventilation between June 2008 and May 2010. The 89 patients underwent ABGA at the 1st hospital day, and changes to their CO(2) level were continuously monitored overnight with a transcutaneous blood gas analysis device. The number of patients who initially appeared to show normal PaCO(2) through ABGA, yet displayed hypercapnea through overnight continuous monitoring, was counted. RESULTS: 36 patients (40.45%) presented inconsistent CO(2) level results between ABGA and continuous overnight monitoring. The mean CO(2) level of the 36 patients using ABGA was 37.23±5.11 mmHg. However, the maximum and mean CO(2) levels from the continuous monitoring device were 52.25±6.87 mmHg and 46.16±6.08 mmHg, respectively. From the total monitoring period (357.28±150.12 minutes), CO(2) retention over 45 mmHg was detected in 198.97 minutes (55.69%). CONCLUSION: Although ABGA only reflects ventilatory status at the puncturing moment, ABGA results are commonly used to monitor ventilatory status in most clinical settings. In order to decide the starting point of home mechanical ventilation in neuromuscular patients, continuous overnight monitoring should be considered to assess latent CO(2) retention.