Home-Based Overnight Transcutaneous Capnography/Pulse Oximetry for Diagnosing Nocturnal Hypoventilation Associated With Neuromuscular Disorders

Abstract

ObjectiveTo determine the utility of home-based, unsupervised transcutaneous partial pressure of carbon dioxide (tc-Pco2) monitoring/oxygen saturation by pulse oximetry (Spo2) for detecting nocturnal hypoventilation (NH) in individuals with neuromuscular disorders. DesignRetrospective case series analyzed consecutively. SettingMultidisciplinary neuromuscular respiratory failure (NMRF) clinic at an academic institution. ParticipantsSubjects (N=35, 68.6% men; mean age, 46.9y) with spinal cord injury (45.7%) or other neuromuscular disorders underwent overnight tests with tc-Pco2/Spo2 monitoring. Fifteen (42.9%) were using nocturnal ventilatory support, either bilevel positive airway pressure (BiPAP) or tracheostomy ventilation (TV). InterventionsA respiratory therapist brought a calibrated tc-Pco2/Spo2 monitor to the patient’s home and provided instructions for data collection during the subject’s normal sleep period. Forced vital capacity (FVC), body mass index (BMI), and exhaled end-tidal Pco2 (ET-Pco2) were recorded at a clinic visit before monitoring. Main Outcome MeasuresDetection of NH (tc-Pco2 ≥50mmHg for ≥5% of monitoring time). Data were also analyzed to determine whether nocturnal oxygen desaturation (Spo2 ≤88% for ≥5% of monitoring time), FVC, BMI, or daytime ET-Pco2 could predict the presence of NH. ResultsNH was detected in 18 subjects (51.4%), including 53.3% of those using BiPAP or TV. NH was detected in 43.8% of ventilator-independent subjects with normal daytime ET-Pco2 (present for 49.4%±31.5% [mean ± SD] of the study period), and in 75% of subjects with an elevated daytime ET-Pco2 (present for 92.3%±8.7% of the study period). Oxygen desaturation, BMI, and FVC were poor predictors of NH. Only 3 attempted monitoring studies failed to produce acceptable results. ConclusionsHome-based, unsupervised monitoring with tc-Pco2/Spo2 is a useful method for diagnosing NH in NMRF.