The mechanisms leading to hypoxemia during sleep in patients with respiratory failure remain poorly understood, with few studies providing a measure of minute ventilation (V I) during sleep. The aim of this study was to measure ventilation during sleep in patients with nocturnal desaturation secondary to different respiratory diseases. The 26 patients studied had diagnoses of chronic obstructive pulmonary disease (COPD) (n = 9), cystic fibrosis (CF) (n = 2), neuromusculoskeletal disease (n = 4), and obesity hypoventilation syndrome (OHS) (n = 11). Also reported are the results for seven normal subjects and seven patients with effectively treated obstructive sleep apnea (OSA) without desaturation during sleep. Ventilation was measured with a pneumotachograph attached to a nasal mask. In the treated patients with OSA and in the normal subjects, only minor alterations in V I were observed during sleep. In contrast, mean V I for the group with nocturnal desaturation decreased by 21% during non-rapid-eye-movement (NREM) sleep and by 39% during rapid-eye-movement (REM) sleep as compared with wakefulness. This reduction was due mainly to a decrease in tidal volume (V T). Hypoventilation was most pronounced during REM sleep, irrespective of the underlying disease. These data indicate that hypoventilation may be the major factor leading to hypoxia during sleep, and that reversal of hypoventilation during sleep should be a major therapeutic strategy for these patients.

Aversion thresholds for electrical shock were obtained from 5 males, 6 females who were taking oral contraceptives, and 12 females who were not. All subjects were volunteers from introductorylevel psychology courses. Measures were repeated 3 times per week for 5 weeks. Males and females taking oral contraceptives showed no cyclic fluctuations in threshold. The other female group had significant (p < .025) fluctuations in threshold, from a maximum at ovulation to a minimum 1 week after the onset of the menses.

Cheyne-Stokes respiration (CSR) during sleep is common in patients with congestive heart failure (CHF). This pattern of breathing fragments sleep, leading to daytime symptoms of sleepiness and fatigue. It was hypothesized that by controlling CSR with noninvasive pressure preset ventilation (NPPV), there would be a decrease in sleep fragmentation and an improvement in sleep quality.Nine patients (eight males, one female; mean±sd 65±11 yrs) with symptomatic CSR diagnosed on overnight polysomnography (apnoea/hypopnoea index (AHI) 49±10·h−1, minimum arterial oxygen saturation (Sa,O2, 77±7%) and CHF (left ventricular ejection fraction 25±8%) were studied. After a period of acclimatization to NPPV (variable positive airway pressure (VPAP) II STTM, Sydney, NSW, Australia and bilevel positive airway pressure (BiPAP)TM, Murraysville, PA, USA), sleep studies were repeated on therapy.NPPV almost completely abolished CSR in all patients with a reduction in AHI from 49±10 to 6±5·h−1(p<0.001). Residual respiratory events were primarily due to upper airway obstruction at sleep on-set. Arousal index was markedly decreased from 42±6 to 17±7·h−1(p<0.001). Sleep architecture showed a trend toward improvement with a reduction in stage 1 and 2 (79±7% during the diagnostic nightversus72±10% during NPPV, (p=0.057)), whilst sleep efficiency, slow-wave sleep (SWS), and rapid eye movement (REM) were not altered.Controlling Cheyne-Stokes respiration with noninvasive pressure preset ventilation resulted in reduced arousal and improved sleep quality in the patients with congestive heart failure. Noninvasive pressure preset ventilation should be considered a potential therapy for Cheyne-Stokes respiration in congestive heart failure in those patients who do not respond or fail to tolerate nasal continuous positive airway pressure therapy.

Slides were made from Munsell color chips in three sizes, four hues, and two chromas; all had the same intensity. A direct-comparisons, forced-choice procedure was used with 100 male and female volunteers from psychology courses. When pairs of slides had the same size and chroma, the order of decreasing apparent size was red-purple, yellow-red, purple-blue, and green. At chroma/8, all comparisons were significant except yellow-red over purple-blue. At chroma/4, the same order was found, but the effect was not pronounced. When pairs were made up of identical hues but different chromas, the square with chroma/4 (less saturation) appeared significantly larger.