Tolerance of Centrifuge-induced Acceleration in Subjects With Diabetes Mellitus and Cardiac Arrhythmia

Diabetes Mellitus, Arrhythmias, Cardiac

The study will involve exposing individuals with a known past medical history of diabetes mellitus and/or cardiac arrhythmias to centrifuge-induced acceleration force (G-force) in the NASTAR AFTS-400 simulator to evaluate their response to such forces. Subjects without a history of these conditions will also undergo centrifuge-induced G-forces as controls. This study will contribute to the knowledge of how individuals with such medical conditions experience G-forces that may be experienced during commercial spaceflights.

UTMB has received grant funding from the Federal Aviation Administration (FAA) under the Center of Excellence for Commercial Space Transportation to investigate these topics. The concern is whether spaceflight, an already hazardous endeavor, would be a greater hazard for the less healthy individual. It remains difficult to predict how particular disease processes will respond to the hypergravity environment during launch and landing of spacecraft, and exactly what these hazards may entail. Conditions such as diabetes mellitus and cardiac arrhythmias may be prevalent in the population group of potential future spaceflight participants and may present additional risk factors in the hypergravity environment, from acceleration tolerance to the ability to carry out moderately complex tasks in emergency or high-stress operational scenarios. While certain disease-related sequelae (such as severe retinopathy, nephropathy, autonomic dysfunction, cardiac ischemia, etc) are likely to represent criteria for exclusion from near-future spaceflight activity, the inclusion of individuals with well-controlled disease without significant sequelae is desirable in the commercial spaceflight industry. The purpose of this study is to evaluate the tolerance of acceleration forces, induced by centrifuge, in individuals with diabetes mellitus and cardiac arrhythmias. Investigators will include in the study individuals known to have either of the following: 1. Well-controlled diabetes (type I or type II, controlled with diet, oral medications, or insulin injections, with HbA1c of \<8% and baseline pre-prandial blood glucose of \<250). 2. Well-controlled cardiac arrhythmias (including control via oral medications, implanted pacemakers, or prior ablation or similar intervention). Cardiac arrhythmias of interest include Wolff-Parkinson-White (WPW), atrial fibrillation, atrial flutter, supraventricular tachycardia, accelerated idioventricular rhythms, junctional rhythms, A-V block. Use of an implanted pacemaker, if demonstrated to be successful in controlling prior dysrhythmia, is acceptable. Investigators will further screen individuals with no known history of these diseases to act as a control group. It is anticipated that individuals with the controlled disease processes included in this study will tolerate acceleration forces well, with changes in cardiovascular responses related primarily to use of medications (primarily beta-blockers; see above for explanation). Investigators will also examine the performance, of both those with medical conditions and the controls, during a simulated emergency with a moderately difficult assigned task. It is hypothesized that these diseases, when well-controlled, are not a contraindication to space travel.

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