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Recent studies have challenged the traditional hypothesis that excessive environmental noise is central to the etiology of sleep disruption in the intensive care unit (ICU). We characterized potentially disruptive ICU noise stimuli and patient-care activities and determined their relative contributions to sleep disruption. Furthermore, we studied the effect of noise in isolation by placing healthy subjects in the ICU in both normal and noise-reduced locations. Seven mechanically ventilated patients and six healthy subjects were studied by continuous 24-hour polysomnography with time-synchronized environmental monitoring. Sound elevations occurred 36.5 +/- 20.1 times per hour of sleep and were responsible for 20.9 +/- 11.3% of total arousals and awakenings. Patient-care activities occurred 7.8 +/- 4.2 times per hour of sleep and were responsible for 7.1 +/- 4.4% of total arousals and awakenings. Healthy subjects slept relatively well in the typically loud ICU environment and experienced a quantitative, but not qualitative, improvement in sleep in a noise-reduced, single-patient ICU room. Our data indicate that noise and patient-care activities account for less than 30% of arousals and awakenings and suggest that other elements of the critically ill patient's environment or treatment should be investigated in the pathogenesis of ICU sleep disruption. [ABSTRACT FROM AUTHOR]

Rationale: Periodic occlusion of the upper airway in patients with obstructive sleep apnea leads to chronic intermittent hypoxia, which increases the acute hypoxic ventilatory response (AHVR). Animal studies suggest that oxidative stress may modulate AHVR by increasing carotid body sensitivity to hypoxia. This has not been shown in humans. Objectives: To determine whether 4 days of exposure to chronic intermittent hypoxia increases AHVR and oxidative stress and to determine the strength of the association between oxidative stress and AHVR. Methods: After two normoxic control days (Day -4 and Day 0), 10 young healthy men were exposed awake to 4 days (Days 1-4) of intermittent hypoxia for 6 hours per day. Measurements and Main Results: AHVR, assessed using an isocapnic hypoxia protocol, was determined as the slope of the linear regression between ventilation and oxygen desaturation. Oxidative stress was evaluated by measuring plasma DNA, lipid and protein oxidation, uric acid and antioxidant status by measuring alpha-tocopherol, total vitamin C, and antioxidant enzymatic activities. Between baseline and Day 4, there were significant increases in AHVR, DNA oxidation, uric acid, and vitamin C, whereas antioxidant enzymatic activities and alpha-tocopherol were unchanged. There were strong correlations between the changes in AHVR and DNA oxidation (r = 0.88; P = 0.002). Conclusions: Chronic intermittent hypoxia increases oxidative stress by increasing production of reactive oxygen species without a compensatory increase in antioxidant activity. This human study shows that reactive oxygen species overproduction modulates increased AHVR. These mechanisms may be responsible for increased AHVR in patients with obstructive sleep apnea. [ABSTRACT FROM AUTHOR]

Study Objectives: To determine whether differences in sleep apnea severity between men and women referred to a sleep clinic are related to the differences in neck circumference (NC).Study Design: Case series.Setting: University hospital sleep disorders clinic.Participants: A total of 3,942 patients (2,753 men and 1,189 women) referred to the sleep clinic.Measurements and Results: All patients underwent nocturnal polysomnography. NC was used as a surrogate measure of upper airway obesity. We found that sleep apnea, defined an the apnea/hypopnea index (AHI) > 10/h, was significantly more frequent (60% vs 32%, chi(2) < 0.0001) and severe (mean +/- SE, 25 +/- 26/h vs 12 +/- 19/h, p < 0.0001) in men than in women. Men had significantly larger NC than women, but the difference became much less pronounced when we normalized NC to body height (0.24 +/- 0.02 vs 0.23 +/- 0.03, p < 0.0001). Men had significantly higher AHI than women even after controlling for age, body mass index (BMI), and neck/height ratio (NHR); analysis of covariance showed that mean AHI was 24.4 +/- 0.4 in men vs 14.8 +/- 0.7 in women (p < 0.0001). This difference persisted even when we matched men and women for NHR and BMI. Finally, multiple regression analysis revealed the following: (1) NHR was the most significant predictor of AHI, accounting for 19% of the variability; and (2) the slope of AHI vs NHR was significantly higher in men than in women.Conclusions: We conclude the following: (1) the frequency and severity of sleep apnea in the sleep clinic population is greater in men than women, and (2) factors other than NC, age, and BMI must contribute to these gender differences. [ABSTRACT FROM AUTHOR]