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In this study, we applied time- and frequency-domain signal processing techniques to the analysis of respiratory and arterial O2saturation (SaO2) oscillations during nonapneic periodic breathing (PB) in 37 supine awake chronic heart failure patients. O2was administered to eight of them at 3 l/min. Instantaneous tidal volume and instantaneous minute ventilation (IMV) signals were obtained from the lung volume signal. The main objectives were to verify 1) whether the timing relationship between IMV and SaO2was consistent with modeling predictions derived from the instability hypothesis of PB and 2) whether O2administration, by decreasing loop gain and increasing O2stores, would have increased system stability reducing or abolishing the ventilatory oscillation. PB was centered around 0.021 Hz, whereas respiratory rate was centered around 0.33 Hz and was almost stable between hyperventilation and hypopnea. The average phase shift between IMV and SaO2at the PB frequency was 205° (95% confidence interval 198–212°). In 12 of 37 patients in whom we measured the pure circulatory delay, the predicted lung-to-ear delay was 28.8 ± 5.2 s and the corresponding observed delay was 30.9 ± 8.8 s (P= 0.13). In seven of eight patients, O2administration abolished PB (in the eighth patient, SaO2did not increase). These results show a remarkable consistency between theoretical expectations derived from the instability hypothesis and experimental observations and clearly indicate that a condition of loss of stability in the chemical feedback control of ventilation might play a determinant role in the genesis of PB in awake chronic heart failure patients.

Erectile dysfunction (ED) is common in men with obstructive sleep apnea (OSAS) but no completely convincing hypotheses about the underlying pathogenic mechanisms have been published in the literature. The aims of the present study were to assess the presence of ED in a group of OSAS patients without daytime respiratory failure and to determine whether this dysfunction was related to peripheral nerve involvement. Evaluation of the bulbocavernosus reflex (BCR) and the somato-sensory evoked potentials of pudendal nerve (PSEPs), the most widely established method of documenting pudendal neuropathies as being the cause of impotence, was performed in 25 patients. Data on BCR were compared with those of 25 healthy males volunteers matched for age. BCR was altered in 17 patients: in 6 it was elicited while in 11 it had a prolonged latency and reduced amplitude. Patients with altered BCR presented an higher AHI, an higher percentage of sleep time spent with SaO2 <90% (TST90) and a lower daytime PaO2. Six patient had clinically silent neurophysiological signs of mild polyneuropathy. The degree of OSAS and gas exchange alteration was more severe in patients with polyneuropathy than in those with isolated BCR alteration. ED is a common finding in OSAS patients and this alteration seems to be related to a nerve dysfunction. The development of nerve dysfunction is associated with a more severe degree of OSAS and nocturnal hypoxia.

A clinical and polygraphic study of nocturnal sleep was performed in 8 (4 males, 4 females; age range 10–37 years) patients with spinal muscular atrophy, whose baseline respiratory function assessment during wakefulness showed restrictive ventilatory syndrome but blood-gas tension within normal limits. No patient reported any significant sleep complaint suggestive of sleepdisordered breathing. However, in 4 patients HbSaO2 desaturations below 90% (HbSaO2 nadir 68%) were detected during nocturnal polysomnography. The HbSaO2 desaturations occurred during brief central apneas or hypopneas, mainly during REM sleep, the apnoea hypopnea index being within normal limits in all cases. The data suggest that nocturnal polysomnography can detect otherwise clinically silent hypoxemia in SMA patients without any predisposing factor to sleep-disordered breathing other than their illness and still showing normal blood-gas tensions during wakefulness. Further studies are needed to determine the long-term evolution and the prognostic significance of nocturnal hypoxemia in these patients. Sono illustrati i risultati di una indagine clinica e polisonnografica sugli aspetti del sonno notturno e della respirazione durante sonno in 8 pazienti affetti da Amiotrofia Spinale (4 maschi, 4 femmine, di età compresa tra 10 e 37 anni) e che mostravano in veglia una sindrome restrittiva toracica ma valori emogasanalitici ancora nei limiti della norma. Nessun paziente riportava disturbi soggettivi del sonno tra quelli suggestivi di un sottostante disordine respiratorio sonno-relato. In 4 pazienti sono state documentate ricorrenti desaturazioni emoglobiniche di O2 sotto il 90% (valore minimo osservato 68%) nel corso della polisonnografia notturna, in relazione ad apnee o ipopnee non ostruttive, principalmente durante sonno REM. L'Indice di Apnea/Ipopnea è risultato essere nei limiti in tutti i pazienti. I dati suggeriscono che una iniziale tendenza alla desaturazione di O2 sonno relata può essere presente in pazienti con Amiotrofia Spinale senza apparenti disturbi clinici del sonno e che mostrano ancora un quadro di compenso emogasanalitico in veglia. L'evoluzione, la rilevanza clinica e dunque il significato prognostico di tali patterns di ipossiemia notturna andranno verificati in studi clinici e polisonnografici più estesi e con sviluppo longitudinale.

The aim of this study was to assess breathing patterns during sleep in patients with generalized mild myasthenia gravis. Fourteen patients (13 F; 1M, age range 20–40 years) in a stable clinical and functional state underwent a sleep questionnaire, baseline respiratory function tests and standard nocturnal polysomnography.