Immediate effects of phototherapy on sleep in very preterm neonates: an observational study.

Process C (internal clock) and Process S (sleep-wake homeostasis) are the basis of sleep-wake regulation. In the last trimester of pregnancy, foetal heart rate is synchronized with the maternal circadian rhythm. At birth, this interaction fails and an ultradian rhythm appears. Light exposure is a strong factor influencing the synchronization of sleep-wake processes. However, little is known about the effects of phototherapy on the sleep rhythm of premature babies. It was hypothesized that sleep in preterm infants would not differ during phototherapy, but that a maturation effect would be seen. Sleep states were studied in 38 infants born < 32 weeks gestational age and/or < 1 500 g birth weight. Videos of 3 h were taken over the first 5 days of life. Based on breathing and movement patterns, behavioural states were defined as: awake; active sleep; or quiet sleep. Videos with and without phototherapy were compared for amounts of quiet sleep and active states (awake + active sleep). No significant association between phototherapy and amount of quiet sleep was found (P = 0.083). Analysis of videos in infants not under phototherapy revealed an increase in time spent awake with increasing gestational age. The current data suggest that the ultradian rhythm of preterm infants seems to be independent of phototherapy, supporting the notion that sleep rhythm in this population is mainly driven by their internal clock.

Single-Breath Washout Tests to Assess Small Airway Disease in COPD.

BACKGROUND: Current functional assessments do not allow a reliable assessment of small airways, which are a major site of disease in COPD. Single-breath washout (SBW) tests are feasible and reproducible methods for evaluating small airway disease. Their relevance in COPD remains unknown. METHODS: We performed a cross-sectional study in 65 patients with moderate to severe COPD. Phase III slope of nitrogen (SIIIN2) and double tracer gas (SIIIDTG) SBW tests were used as a measure of ventilation inhomogeneity. The association of both markers with established physiological and clinical features of COPD was assessed. RESULTS: Ventilation inhomogeneity as measured by SIIIN2 and SIIIDTG was increased in patients with COPD compared with healthy subjects (P < .001 and P < .001, respectively). SIIIN2 was associated with FEV1 predicted, residual volume (RV)/total lung capacity (TLC) and diffusing capacity of the lung for carbon monoxide (Dlco) (all P < .001). Furthermore, SIIIN2 was related to dyspnea, exercise-induced desaturation, and exercise capacity (P = .001, P < .001, and P = .047, respectively). SIIIDTG was associated with TLC, Dlco, and cough (P < .001, P = .001, and P = .009, respectively). In multivariate regression models, we demonstrated that these associations are largely independent of FEV1 and mostly stronger than associations with FEV1. In contrast, FEV1 was superior in predicting emphysema severity. CONCLUSIONS: SIIIN2 and SIIIDTG, two fast and clinically applicable measures of small airway disease, reflect different physiological and clinical aspects of COPD, largely independent of spirometry. TRIAL REGISTRY: ISRCTN99586989, Ethics committee Beider Basel (approval number 295/07).