A new therapy for sleep apnea?

Survival benefit of CPAP therapy among dialysis patients with obstructive sleep apnea

BACKGROUND AND HYPOTHESIS

We observed lower risk of all-cause mortally among continuous positive airway pressure (CPAP) users compared to those non-users using a large polysomnography (PSG) registry. However, the effect of CPAP on mortality risk has not been examined in dialysis patents.

METHODS

We studied 9841 patients with PSG performed from September 1990 to 2010 in Nakamura clinic, Okinawa. Among them, we found 195 dialysis patients: 16 (1.0%) dialysis patients with apnea hypopnea index (AHI) < 5/hour in 1665 subjects and 179 (2.2%) in 8176 obstructive sleep apnea (OSA) patients. CPAP users were defined as patients who had been on CPAP for more than one month. Patients qualified and eligible for CPAP but refused were assigned as CPAP non-users. The median observation was 6.6 years. Mortality rates were compared between CPAP users and non-users using multivariate logistic analysis adjusted for age, sex, body mass index (BMI), AHI and medical history.

RESULTS

Among OSA dialysis patients (men 127, women 37), 116 (2.6%) were CPAP users and 48 (2.3%) were CPAP non-users. The number of deaths was 52 (29 CPAP users and 23 (CPAP non-users) during follow-up. The death rate was 25.0% for CPAP users and 47.9% for non-users. CPAP users showed better survival; hazard ratio (HR) 0.47 and 95% confidence interval (CI) of 0.27-0.81 (P = 0.007).

CONCLUSION

Dialysis patients with OSA showed better survival rates with the use of CPAP. Screening for OSA is recommended if patients complain of sleep problems, such as insomnia, daytime sleepiness, headache, and fatigue.

In Transgenic Erythropoietin Deficient Mice, an Increase in Respiratory Response to Hypercapnia Parallels Abnormal Distribution of CO2/H+-Activated Cells in the Medulla Oblongata

Erythropoietin (Epo) and its receptor are expressed in central respiratory areas. We hypothesized that chronic Epo deficiency alters functioning of central respiratory areas and thus the respiratory adaptation to hypercapnia. The hypercapnic ventilatory response (HcVR) was evaluated by whole body plethysmography in wild type (WT) and Epo deficient (Epo-TAg^h) adult male mice under 4%CO₂. Epo-TAg^h mice showed a larger HcVR than WT mice because of an increase in both respiratory frequency and tidal volume, whereas WT mice only increased their tidal volume. A functional histological approach revealed changes in CO₂/H⁺-activated cells between Epo-TAg^h and WT mice. First, Epo-TAg^h mice showed a smaller increase under hypercapnia in c-FOS-positive number of cells in the retrotrapezoid nucleus/parafacial respiratory group than WT, and this, independently of changes in the number of PHOX2B-expressing cells. Second, we did not observe in Epo-TAg^h mice the hypercapnic increase in c-FOS-positive number of cells in the nucleus of the solitary tract present in WT mice. Finally, whereas hypercapnia did not induce an increase in the c-FOS-positive number of cells in medullary raphe nuclei in WT mice, chronic Epo deficiency leads to raphe pallidus and magnus nuclei activation by hyperacpnia, with a significant part of c-FOS positive cells displaying an immunoreactivity for serotonin in the raphe pallidus nucleus. All of these results suggest that chronic Epo-deficiency affects both the pattern of ventilatory response to hypercapnia and associated medullary respiratory network at adult stage with an increase in the sensitivity of 5-HT and non-5-HT neurons of the raphe medullary nuclei leading to stimulation of f_R for moderate level of CO₂.