The Significance of Transcutaneous Continuous Overnight CO₂Monitoring in Determining Initial Mechanical Ventilator Application for Patients with Neuromuscular Disease

Abstract

ObjectiveTo reveal the significance of continuous transcutaneous carbon dioxide (CO2) level monitoring through reviewing cases which showed a discrepancy in CO2 levels between arterial blood gas analysis (ABGA) and continuous transcutaneous blood gas monitoring.MethodMedical 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 CO2 level were continuously monitored overnight with a transcutaneous blood gas analysis device. The number of patients who initially appeared to show normal PaCO2 through ABGA, yet displayed hypercapnea through overnight continuous monitoring, was counted.Results36 patients (40.45%) presented inconsistent CO2 level results between ABGA and continuous overnight monitoring. The mean CO2 level of the 36 patients using ABGA was 37.23±5.11 mmHg. However, the maximum and mean CO2 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), CO2 retention over 45 mmHg was detected in 198.97 minutes (55.69%).ConclusionAlthough 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 CO2 retention.

Detection of early nocturnal hypoventilation in neuromuscular disorders

“…A previous report suggested that nocturnal transcutaneous assessment of pCO 2 was more reliable than CO 2 measured by morning arterial blood gases. 13 In contrast, Georges et al 15 reported similar findings to our current data but their study group included a much wider population of respiratory restrictive disorders, not only neuromuscular diseases. Finally, Ogna et al 14 demonstrated the usefulness of tcPCO 2 /SpO 2 monitoring among the NH diagnostic tools, and the need to better define the threshold for NH itself.…”

“…Few studies have specifically evaluated whether nocturnal hypercapnia is present in clinically asymptomatic patients with NMD. 13 – 15 If this is the case, this finding could further expand the indications for NIV support.…”

Validity of transcutaneous PCO 2 in monitoring chronic hypoventilation treated with non-invasive ventilation

“…ABG analysis, although necessary, yields limited information. For instance, daytime ABG are poor predictors of nocturnal hypoventilation [9,10]. Sampling of ABG during sleep may detect nocturnal hypoventilation, but will not reflect variations of PaCO 2 related to sleep stages, position or mask leaks.…”

Contribution of Transcutaneous PCO2in Obesity Hypoventilation Syndrome

“…ABGs were sampled when the subject was awake during the medical consultation and thus these subjects may have a normalized P aCO 2 . Daytime ABGs only partially reflect nighttime ventilation, 14 which certainly reduces the sensitivity of this test. The American Thoracic Society guideline 13 recommends the use of a bicarbonate level < 27 mmol/L to exclude OHS when the suspicion is not very high.…”