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Abstract
This single-subject case examined oxyhemoglobin saturation and alveolar end-tidal carbon dioxide levels in a ventilator-dependent tetraplegic patient undergoing electrical stimulation cycle ergometry. When exercising with a closed tracheostomy cuff under resting ventilator settings (resting intermittent mandatory ventilation; frequency = 6breaths/min, tidal volume = 83.3m-L, minute ventilation =5L/min), his oxyhemoglobin saturation decreased from 100% to 92%, while alveolar end-tidal carbon dioxide increased linearly to 47mmHg. These undesirable changes were corrected under adjusted intermittent mandatory ventilation conditions (frequency = 12breaths/min, tidal volume = 83.3mL, minute ventilation = 10L/min), during which oxyhemoglobin saturation remained above 98% and the alveolar end-tidal carbon dioxide trend resembled that of ventilator-independent tetraplegic individuals undergoing the same exercise. Because the subject's heart rate was higher under adjusted ventilation conditions, these responses may have been caused by augmented venous return resulting from greater abdominothoracic pumping at the higher breathing frequency. These findings support the need to modify ventilator settings in ventilator-dependent tetraplegic persons while undergoing exercise to maintain oxyhemoglobin saturation and carbon dioxide homeostasis.
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Article info
Publication history
Accepted:
October 2,
1997
Received:
September 19,
1997
Footnotes
☆Supported by the Miami Project to Cure Paralysis.
☆☆No commercial party having a direct or indirect interest in the subject matter of this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated.
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© 1998 Published by Elsevier Inc.
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