PURPOSE: Neuromuscular respiratory failure (NMRF) often begins with nocturnal hypoventilation, but early diagnosis is limited because facility-based polysomnograms can be difficult to obtain for severely disabled patients. To address this problem, we have employed in-home monitoring with pulse oximety/transcutaneous capnography. This study describes our experience with this approach.
METHODS: Medical record review of patients with neuromuscular disorders studied between December 2009 and April 2011. A SenTec Digital Monitor (SenTec AG, Therwil, Switzerland) was placed to collect overnight transcutaneous pCO2/spO2 data throughout the normal sleep period. Clinical data, forced vital capacity (FVC), end-tidal (ET)-CO2, and CPAP/BiPAP use were reviewed.
RESULTS: 28 studies were performed successfully; only 2 were rejected as technically unacceptable. 16 (57.1%) patients had a spinal cord injury (SCI), and 12 (42.9%) had other neuromuscular disorders. All had restrictive ventilatory defects (mean FVC 37.2% predicted, range 17-74%). 13 (46.4%) were using CPAP /BiPAP. 15 patients (53.6%) had nocturnal hypoventilation (defined as transcutaneous pCO2 ≥ 50mmHg for ≥ 5% of study time) for 64.3% of the study time (mean; range 11-100%). This included 54% of patients using CPAP/BiPAP. Nocturnal hypoventilation was confirmed in 53.8% of patients with normal daytime ET-CO2 (≤ 47mmHg) and no CPAP/BiPAP support. Patients with elevated daytime ET-CO2 had nocturnal hypoventilation more commonly (85.7%, including patients using CPAP/BiPAP). Oxygen desaturation (O2 sat ≤88% for ≥ 5% of study time) was detected in 46.7% with, and 23% without, nocturnal hypoventilation. In SCI patients, FVC was 34.2± 13.3% predicted with, and 41.7± 8.9% predicted without, nocturnal hypoventilation.
CONCLUSIONS: Home-based unsupervised monitoring with pulse oximetry/transcutaneous capnography can be used to diagnose nocturnal hypoventilation in NMRF. Unsuspected nocturnal hypoventilation is common even when CPAP/BiPAP is being used, and cannot be predicted by nocturnal O2 desaturation or FVC.
CLINICAL IMPLICATIONS: Home-based unsupervised pulse oximetry/transcutaneous capnography can facilitate early recognition of nocturnal hypoventilation, obviating the need for most facility-based sleep studies. Future implications include earlier institution of ventilatory support, cost savings, and greater patient acceptance.
DISCLOSURE: The following authors have nothing to disclose: Kristy Bauman, Armando Kurili, Janice Peploski, Gianna Rodriguez, Anthony Chiodo, Robert Sitrin
No Product/Research Disclosure Information