J.-P. Derenne

Unawareness of naps in Parkinson's disease and in disorders with excessive daytime sleepiness.

Sudden episodes of falling asleep while driving occur in patients with PD treated with dopamine agonists or levodopa.1 However, one may not adequately perceive the wake-sleep transition at sleep onset2 or when awakening from a sleep episode. We examine whether patients with and without PD who fall asleep during daytime naps realize afterward that they have been asleep.nnForty-seven somnolent patients with PD (table) were being treated with levodopa (all patients) and dopamine agonists (23 patients) and were free of other sedative drugs. They underwent a daytime multiple sleep latency test with five nap opportunities.3 After each nap, they had to state if they had slept or dozed. Those who slept during a test and firmly answered they did not were considered as misperceiving daytime sleepiness. Their responses were compared with those of 51 patients with sleep disorders (mainly hypersomnia …

Source of human ventilatory chaos: lessons from switching controlled mechanical ventilation to inspiratory pressure support in critically ill patients.

Ventilatory flow measured at the airway opening in humans exhibits a complex dynamics that has the features of chaos. Currently available data point to a neural origin of this feature, but the role of respiratory mechanics has not been specifically assessed. In this aim, we studied 17 critically ill mechanically ventilated patients during a switch form an entirely machine-controlled assistance mode (assist-controlled ventilation ACV) to a patient-driven mode (inspiratory pressure support IPS). Breath-by-breath respiratory variability was assessed with the coefficient of variation of tidal volume, total cycle time, inspiratory time, expiratory time, mean inspiratory flow, duty cycle. The detection of chaos was performed with the noise titration technique. When present, chaos was characterized with numerical indexes (correlation dimension, irregularity; largest Lyapunov exponent, sensitivity to initial conditions). Expectedly, the coefficients of variations of the respiratory variables were higher during IPS than during ACV. During ACV, noise titration failed to detect nonlinearities in 12 patients who did not exhibit signs of spontaneous respiratory activity. This indicates that the mechanical properties of the respiratory system were not sufficient to produce ventilatory chaos in the presence of a nonlinear command (ventilator clock). A positive noise limit was found in the remaining 5 cases, but these patients exhibited signs of active expiratory control (highly variable expiratory time, respiratory frequency higher than the set frequency). A positive noise limit was also observed in 16/17 patients during IPS (p<0.001). These observations suggest that ventilatory chaos predominantly has a neural origin (intrinsic to the respiratory central pattern generators, resulting from their perturbation by respiratory afferents, or both), with little contribution of respiratory mechanics, if any.

Expiratory-synchronized sleep in a quadriplegic patient using inspiratory neck muscles to breathe.

In a patient with C3 quadriplegia causing complete diaphragm paralysis who developed inspiratory neck muscles (INM) hypertrophy to sustain ventilation, spontaneous breathing deeply altered sleep architecture, relegating sleep to the expiratory phase of the ventilatory cycle. A polysomnographic recording performed during mechanical ventilation (without INM activity), showed that sleep was abnormal but unaffected by the respiratory cycle. During spontaneous breathing, the polygraphic recordings showed expiratory microsleep episodes, with inspiratory arousals synchronous to bursts of INM activity. This case report illustrates the powerful adaptability of the respiratory and sleep control systems to maintain each vital function.