Central sleep apnea treated by a constant low-dose CO2 supplied by a novel device.

CO2 inhalation has been previously reported as a treatment for central sleep apnea both when associated with heart failure or where the cause is unknown. Here, we evaluated a novel CO2 supply system using a novel open mask capable of comfortably delivering a constantly inspired fraction of CO2 ([Formula: see text]) during sleep. We recruited 18 patients with central sleep apnea (13 patients with cardiac disease, and 5 patients idiopathic) diagnosed by diaphragm electromyogram (EMG) recordings made during overnight full polysomnography (PSG) (night 1). In each case, the optimal [Formula: see text] was determined by an overnight manual titration with PSG (night 2). Titration commenced at 1% CO2 and increased by 0.2% increments until central sleep apnea (CSA) disappeared. Patients were then treated on the third night (night 3) with the lowest therapeutically effective concentration of CO2 derived from night 2. Comparing night 1 and night 3, both apnea-hypopnea index (AHI; 31 ± 14 vs. 6 ± 3 events/h, P < 0.01) and arousal index (22 ± 8 vs. 15 ± 8 events/h, P < 0.01) were significantly improved during CO2 treatment. Sleep efficiency improved from 71 ± 18 to 80 ± 11%, P < 0.05, and sleep latency was shorter (23 ± 18 vs. 10 ± 10 min, P < 0.01). Heart rate was not different between night 1 and night 3. Our data confirm the feasibility of our CO2 delivery system and indicate that individually titrated CO2 supplementation with a novel device including a special open mask can reduce sleep disordered breathing severity and improve sleep quality. Randomized controlled studies should now be undertaken to assess therapeutic benefit for patients with CSA.NEW & NOTEWORTHY A novel device using a special mask was developed and proved that CO2 therapy using the device could eliminate central sleep apnea (CSA) events and improve sleep quality including reducing arousal index in patients with heart failure. The device would become a useful clinical treatment for heart failure patients with CSA.

Effects of microbial diversity loss on the stability of CO2 production and N2O emission in agricultural soils.

The relationship between biodiversity and ecosystem stability is a hot topic in ecology. However, current studies focus mainly on aboveground system with plants, little attention has been paid to belowground system with soils. In this study, we constructed three soil suspensions with varying microbial diversity (100, 10-2, 10-6) by the dilution method and inoculated separately into agricultural Mollisols and Oxisols to examine the stability (indicated by resistance and resilience) of soil CO2 production and N2O emission to copper pollution and heat stress. Results showed that the stability of CO2 production in Mollisols was not influenced by microbial diversity loss, while the resistance and resilience of N2O emission in Mollisols were significantly decreased at the 10-6 diversity. In the Oxisols, the resistance and resilience of N2O emission to copper pollution and heat stress started to decrease even at the 10-2 diversity, and the stability of CO2 production decreased at the 10-6 diversity. These results suggested that both soil types and the identity of soil functions influenced the relationship between microbial diversity and the stability of function. It was concluded that soils with ample nutrients and resistant microbial communities tend to have higher functional stability, and that the fundamental soil functions (e.g., CO2 production) are more resistant and resilient than the specific soil functions (e.g., N2O emission) in response to environmental stress.

Treatment of obstructive sleep apnea with a simple CPAP device.

PURPOSE: CPAP is the "gold standard" treatment for obstructive sleep apnea (OSA). Current CPAP models have developed additional functions including automatic CPAP and pressure relief. However, CPAP adherence has not improved over the last three decades. Many patients in low-income countries cannot afford these CPAP devices. A novel simple CPAP device with a fixed pressure without pressure controller was developed. METHODS: Manual CPAP pressure titration was performed in 127 patients with OSA. Six patients with a titration pressure higher than 11 cmH2O and 14 patients who could not tolerate CPAP were excluded, leaving 107 participating in the following 2 studies. In study one, 54 of 107 patients were treated by both conventional fixed CPAP and simple CPAP in random order. In the second study, another 53 patients were treated by both autoCPAP in automatic function and simple CPAP in random order. Simple CPAP was fixed at 10 cmH2O, 8 cmH2O, and 6 cmH2O for patients whose titration pressure was between 9-10, 7-8, and ≤ 6 cmH2O, respectively. Conventional fixed CPAP device was set exactly the same as manual titration pressure. RESULTS: All patients whose manual titration pressure ≤ 10 cmH2O were effectively treated by simple CPAP (AHI 40.7 ± 2.3 events/h before vs 2.5 ± 0.3 events/h after, p < 0.001). Patients expressed similar preferences for simple CPAP, autoCPAP, and conventional fixed CPAP (p > 0.05). CONCLUSIONS: We conclude that a novel simple CPAP is an alternative treatment for most patients with OSA, which may widen access to CPAP therapy in the developing countries because of its low cost.