Interaction of mental and orthostatic stressors |
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| Authors: | Nandu Goswami Helmut K Lackner Ilona Papousek Daniela Jezova Jean-Pierre Montani Helmut G Hinghofer-Szalkay |
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| Institution: | 1. Institute of Physiology, Center of Physiological Medicine, Medical University of Graz, Harrachgasse 21/5, Graz, Austria;2. Institute of Adaptive and Spaceflight Physiology, Wormgasse 9, Graz, Austria;3. Department of Psychology, Karl Franzens University, Graz, Austria;4. Institute of Experimental Endocrinology, Slovak Academy of Sciences, Bratislava, Slovakia;5. Department of Medicine/Physiology, University of Fribourg, Switzerland;1. School of Life Sciences, Ulsan National Institute of Science and Technology, Ulsan, Republic of Korea;2. Division of Molecular and Life Science, Pohang University of Science and Technology, Pohang, Kyungbuk, Republic of Korea;3. Cancer Experimental Resources Branch, National Cancer Center, Goyang-si, Gyeonggi-do, Republic of Korea;1. Institute of Astronautics, Technische Universität München, Boltzmannstr. 15, 85748 Garching, Germany;2. Department of Mechanical and Aerospace Engineering, Naval Postgraduate School, Monterey, 93943-5107 CA, United States;1. Department of Psychiatry, Faculty of Medicine, Saga University, 5-1-1 Nabeshima, Saga, Japan;2. Institute of Comparative Studies of International Cultures and Societies, Kurume University, Fukuoka, Japan;3. Kojima Hospital, Saga, Japan;4. Nakataku Hospital, Saga, Japan;5. St Lucia?s Hospital, Fukuoka, Japan;1. University of Colorado, Boulder, CO 80309, USA;2. Applied Defense Solutions, Columbia, MD 21044, USA |
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| Abstract: | We assessed hemodynamic responses induced by orthostatic and mental stressors, using passive head up tilt (HUT) and mental arithmetic (MA), respectively. The 15 healthy males underwent three protocols: (1) HUT alone, (2) MA in supine position and (3) MA+HUT, with sessions randomized and ≥2 weeks apart. In relation to baseline, HUT increased heart rate (HR) (+20.4±7.1 bpm; p<0.001), mean blood pressure (MBP) (+4.7±11.3 mmHg; p<0.05), diastolic blood pressure (DBP) (+6.1±11.6 mmHg; p<0.05) and total peripheral resistance (TPR) (+155±232 dyne*s/cm5; p<0.001) but decreased stroke volume (SV) (?33.1±13.4 ml; p<0.001) and cardiac output (CO) (?0.6±1.0 l/min; p<0.01). MA increased HR (+8.0±6.0 bpm; p<0.001), systolic blood pressure (SBP) (+9.0±7.7 mmHg; p<0.001), MBP (+10.0±6.5 mmHg; p<0.001), DBP (+9.5±7.2 mmHg; p<0.001) and CO (+0.6±0.8 l/min; p<0.01). MA+HUT increased HR (+28.8±8.4 bpm; p<0.001), SBP (+4.6±14.3 mmHg; p<0.05), MBP (+11.2±11.6 mmHg; p<0.001), DBP (+13.5±10.1 mmHg; p<0.001) and TPR (+160±199 dyne*s/cm5; p<0.001) but SV (?34.5±14.6 ml; p<0.001) decreased. Mental challenge during orthostatic challenge elicited greater increases in heart rate, despite similar reductions in stroke volume such as those during orthostatic stress alone. Overall, cardiac output decreases were less with combinations of mental and orthostatic challenges in comparison to orthostasis alone. This would suggest that carefully chosen mental stressors might affect orthostatic responses of people on standing up. Therefore, additional mental loading could be a useful countermeasure to alleviate the orthostatic responses of persons, particularly in those with histories of dizziness on standing up or on return to earth from the spaceflight environment of microgravity. |
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