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Noninvasive Intracranial Pressure and Tissue Oxygen Measurements for Space and EarthThe paper discusses the following: Increasing intracranial pressure in humans during simulated microgravity. and near-infrared monitoring of model chronic compartment syndrome in exercising skeletal muscle. Compared to upright-seated posture, 0 deg. supine, 6 deg. HDT, and 15 deg. HDT produced TMD changes of 317 +/- 112, 403 +/- 114, and 474 +/- 112 n1 (means +/- S.E.), respectively. Furthermore, postural transitions from 0 deg. supine to 6 deg. HDT and from 6 deg. to 15 deg. HDT generated significant TMD changes (p less than 0.05). There was no hysteresis when postural transitions to HDT were compared to reciprocal transitions toward upright seated posture. Currently, diagnosis of chronic compartment syndrome (CCS) depends on measurement of intramuscular pressure by invasive catheterization. We hypothesized that this syndrome can be detected noninvasively by near-infrared (NIR) spectroscopy, which tracks variations in muscle hemoglobin/myoglobin oxygen saturation. CCS was simulated in the tibialis anterior muscle of 7 male and 3 female subjects by gradual inflation of a cuff placed around the leg to 40 mmHg during 14 minutes of cyclic isokinetic dorsiflexion exercise. On a separate day, subjects underwent the identical exercise protocol with no external compression. In both cases, tissue oxygenation (T(sub O2) was measured in the tibialis anterior by NIR spectroscopy and normalized to a percentage scale between baseline and a T(sub O2) nadir reached during exercise to ischemic exhaustion. Over the course of exercise, T(sub O2) declined at a rate of 1.4 +/- 0.3% per minute with model CCS, yet did not decrease during control exercise. Post-exercise recovery of T(sub O2) was slower with model CCS (2.5 +/- 0.6 min) than in control (1.3 +/- 0.2 min). These results demonstrate that NIR spectroscopy can detect muscle deoxygenation caused by pathologically elevated intramuscular pressure in exercising skeletal muscle. Consequently, this technique shows promise as a noninvasive diagnostic tool for CCS.
Document ID
20020009559
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Hargens, A. R.
Ballard, R. E.
Murthy, G.
Watenpaugh, D. E.
Date Acquired
August 20, 2013
Publication Date
January 1, 1994
Subject Category
Life Sciences (General)
Meeting Information
Meeting: AIAA/NASA Life Sciences and Space Medicine Conference
Location: Houston, TX
Country: United States
Start Date: April 3, 1995
End Date: April 6, 1995
Sponsors: American Inst. of Aeronautics and Astronautics, NASA Headquarters
Funding Number(s)
PROJECT: RTOP 199-14-12-04
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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