Altitude illness is related to low hypoxic chemoresponse and low oxygenation during sleep.

Altitude illness remains a major cause of mortality. Reduced chemosensitivity, irregular breathing leading to central apnoeas/hypopnoeas, and exaggerated pulmonary vasoconstriction may compromise oxygenation. All factors could enhance susceptibility to acute mountain sickness (AMS). We compared 12 AMS-susceptible individuals with recurrent and severe symptoms (AMS+) with 12 "AMS-nonsusceptible" subjects (AMS-), assessing sleep-breathing disorders in simulated altitude as well as chemoresponsive and pulmonary vasoconstrictive responses to hypoxia. During exposure to simulated altitude, mean blood oxygen saturation during sleep was lower in AMS+ subjects (81.6 ± 2.6 versus 86.0 ± 2.4%, p<0.01), associated with a lower central apnoea/hypopnoea index (18.2 ± 18.1 versus 33.4 ± 24.8 events · h(-1) in AMS+ and AMS- subjects, respectively; p=0.038). A lower hypoxic (isocapnic) chemoresponsiveness was observed in AMS+ subjects (0.40 ± 0.49 versus 0.97 ± 0.46 L · min(-1)·%; p<0.001). This represented the only significant and independent predictive factor for altitude intolerance, despite a higher increase in pulmonary artery systolic pressure in response to hypoxia, a lower lung diffusing capacity and a higher endothelin-1 level at baseline in AMS+ subjects (p<0.05). AMS+ subjects were more hypoxaemic whilst exhibiting fewer respiratory events during sleep owing to lower hypoxic (isocapnic) chemoresponsiveness. In conclusion, the reduction in peripheral hypoxic chemosensitivity appears to be a major causative factor for altitude intolerance.

Interventions to decrease tube, line, and drain removals in intensive care units: the FRATER study.

PURPOSES: To evaluate the incidence of unintended tube, line, and drain removals (UTRs) in our ICU, to identify system factors associated with UTRs, and to evaluate interventions designed to decrease UTR occurrence. METHODS: Interventional study in the 18-bed medical ICU of a French general university hospital. We prospectively determined the incidence and circumstances of UTRs in our ICU over a 2-year period. Demographic and clinical data were collected for consecutively admitted patients, and additional information was recorded about patients experiencing UTRs. Investigators analyzed UTR data twice a month to identify possible causes and developed interventions to decrease UTRs (mainly securing tubes and sedation protocol). Conditional logistic regression stratified on length of stay was used to identify risk factors for UTRs and segmented linear regression analysis to test the effects of interventions. RESULTS: Of 2,007 admitted patients (12,256 patient days), 193 (9.6%) experienced 270 UTRs (22/1,000 patient days). Clinical or therapeutic consequences occurred for 17% of UTRs. Three factors were independently associated with UTR; two were risk factors, namely, admission for coma [OR, 2.68; 95% CI (1.87; 3.84); P < 0.0001] and mechanical ventilation in over 65% of all ICU patients [OR = 1.65 (1.19; 2.29); P = 0.003], and one was protective, namely, mean SAPS II >45 in all ICU patients [OR, 0.54; 95% CI (0.39; 0.75); P = 0.0003]. Segmented regression analysis showed a 67.4% drop [95% CI (17.2%; 117.3%); P = 0.009] in the UTR rate after the first intervention was introduced. System factors played a major role in UTR occurrence. CONCLUSION: UTRs are common. A continuous quality-improvement program can reduce UTR rates in the ICU.