Utility of the bispectral index for assessing natural physiological sleep stages in children and young adults.

Polysomnography (PSG) is the gold standard for the analysis of sleep architecture but is not always available in routine practice, as it is time consuming and cumbersome for patients. Bispectral index (BIS), developed to quantify the deepness of general anesthesia, may be used as a simplified tool to evaluate natural sleep depth. We objectively recorded sleep architecture in young patients using the latest BIS Vista monitor and correlated BIS values with PSG sleep stages in order to determine BIS thresholds. Patients, referred for the screening of sleep apnea/hypopnea syndrome or differential diagnosis of hypersomnia were recruited. Overnight PSG and BIS were performed simultaneously. BIS values were averaged for each sleep stage. Pre-sleep wakefulness (W) and wake after sleep onset (WASO) were also differentiated. BIS values were discarded for a signal quality index <90 %. ROC curves were plotted to discriminate sleep stages from each other. Twelve patients (5.7-29.3 years old) were included. Mean BIS values were 83 ± 8, 76 ± 12, 77 ± 11, 70 ± 10, 43 ± 10, and 75 ± 10 for W, WASO, N1, N2, N3 and R (REM) stages, respectively. BIS failed to distinguish W, WASO, N1 and R stages. BIS threshold that identified stage N2 was <73 (AUC = 0.784, p < 0.001) with low sensitivity (75 %) and poor specificity (64 %). BIS threshold that identified stage N3 was <55 (AUC = 0.964, p < 0.001) with an 87 %-sensitivity and a 93 %-specificity. BIS identified stage N3 with satisfactory sensitivity and specificity but is limited by its inability to distinguish REM sleep from wake. Further studies combining BIS with chin electromyogram and/or electrooculogram could be of interest.

Nocturnal oximetry and transcutaneous carbon dioxide in home-ventilated neuromuscular patients.

BACKGROUND: Pulse oximetry alone has been suggested to determine which patients on home mechanical ventilation (MV) require further investigation of nocturnal gas exchange. In patients with neuromuscular diseases, alveolar hypoventilation (AH) is rarely accompanied with ventilation-perfusion ratio heterogeneity, and, therefore, oximetry may be less sensitive for detecting AH than in patients with lung disease. OBJECTIVE: To determine whether pulse oximetry (S(pO(2))) and transcutaneous carbon dioxide (P(tcCO(2))) during the same night were interchangeable or complementary for assessing home MV efficiency in patients with neuromuscular diseases. METHODS: Data were collected retrospectively from the charts of 58 patients with chronic neuromuscular respiratory failure receiving follow-up at a home MV unit. S(pO(2)) and P(tcCO(2)) were recorded during a 1-night hospital stay as part of standard patient care. We compared AH detection rates by P(tcCO(2)), S(pO(2)), and both. RESULTS: AH was detected based on P(tcCO(2)) alone in 24 (41%) patients, and based on S(pO(2)) alone with 3 different cutoffs in 3 (5%), 8 (14%), and 13 (22%) patients, respectively. Using both P(tcCO(2)) and S(pO(2)) showed AH in 25 (43%) patients. CONCLUSIONS: Pulse oximetry alone is not sufficient to exclude AH when assessing home MV efficiency in patients with neuromuscular diseases. Both P(tcCO(2)) and S(pO(2)) should be recorded overnight as the first-line investigation in this population.