SESSION TITLE: Sleep Disorders I
SESSION TYPE: Original Investigation Slide
PRESENTED ON: Tuesday, October 29, 2013 at 02:45 PM - 04:15 PM
PURPOSE: Some visitors to high altitude have obstructive sleep apnea (OSA) treated with positive airway pressure (PAP). In healthy individuals ascending to high altitude, previous studies demonstrate increased pulmonary artery pressure, worsened left ventricular (LV) diastolic function, and improved LV systolic function. It is unknown, however, whether cardiac morphologic or functional changes occur in patients treated with PAP during sleep after acute ascent to high altitude. The objective of our study is to measure cardiac morphologic and functional parameters using transthoracic echocardiography in persons with OSA who are treated with PAP before and after acute ascent to high altitude.
METHODS: Ten residents of 1500 m altitude (645 mm Hg ambient pressure) with PAP treated OSA were acutely exposed to a simulated altitude of 2750 m (545 mm Hg atmospheric pressure) in a hypobaric chamber and slept overnight while wearing PAP. A baseline transthoracic echocardiogram was obtained at ambient barometric pressure prior to sleep and repeated the next morning at altitude after the subject had slept overnight on PAP at altitude. Echocardiographic measures were recorded.
RESULTS: LV systolic function improved after using PAP at altitude, ejection fraction was 51.3 (7.0) % at 2750 m and 46.0 (10.6) % at 1500 m, p=0.04, while diastolic function worsened, isovolumic relaxation time 0.11 (0.02) sec at 2750 m and 0.08 (0.02) sec at 1500 m, p=0.01. Right ventricular systolic pressure (RVSP) increased 17.1 (6.5) mm Hg at 2750 m and 14.4 (5.8) mm Hg at 1500 m, p=0.04 and right ventricular diameter increased 4.1 (0.7) cm at 2750 m and 3.7 (0.7) at 1500 m, p=0.04; but, RV systolic function was unchanged at 2750 m compared to 1500 m.
CONCLUSIONS: In patients with OSA treated with PAP who slept at high altitude, LV systolic function mildly improved and LV diastolic function mildly worsened. RV systolic function was unchanged but the RV was mildly dilated and RVSP increased after sleep at high altitude. These findings are consistent with prior studies on healthy persons without OSA who ascend to high altitude.
CLINICAL IMPLICATIONS: When exposed to high altitude, the echocardiogram changes in OSA patients treated with PAP are similar to those found in healthy individuals. This suggests that these alterations may not be attributable solely to OSA. Caution should be exercised in patients with OSA who acutely ascend to altitude.
DISCLOSURE: The following authors have nothing to disclose: Katsufumi Nishida, James Bell, Samuel Brown, Tom Cloward, Michael Lanspa, Lindell Weaver, Colin Grissom
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