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Biomedical subjects

K K Gillingham

Publications and source records attributed to K K Gillingham.

32 records · Page 2Linked to original sources
PubMed1978

Relaxed +GZ tolerance in healthy men: effect of age.

Fifty-three healthy US Air Force aircrewmen, 26-55 yr old, volunteered for a centrifuge study designed to determine the effect of age on relaxed +GZ tolerance. Each was subjected to G forces of gradual and rapid onset, with G tolerance determined by standardized contraction of peripheral visual fields. Of the subject characteristics studied, only age was positively correlated with rapid-onset G tolerance; both age and weight were positively correlated with gradual-onset G tolerance. A combination of age and weight gave a stronger positive correlation with G tolerance (rapid- and gradual-onset) than did either characteristic alone. No significant negative correlations were observed. We conclude that aging may offer some protection from G stress; there is no evidence that aging leads to a decrement in G tolerance.

Adaptation, Physiological↗
PubMed1977

Visual field contraction during G stress at 13 degrees, 45 degrees, and 65 degrees seatback angles.

In support of the High Acceleration Cockpit program, two groups of six experienced subjects, operating a high-resolution visual field limit tracker, were exposed to gradual-onset (0.067 G/s) G stress to a 7-G maximum on the USAFSAM human centrifuge. Data obtained from one group described the G-induced vertical visual field contraction, and that from the other described horizontal visual field contraction--as they occurred in relaxed subjects in seats with 13 degrees, 45 degrees, and 65 degrees seatback angles. Curves of peripheral vision remaining vs. G level indicated a statistically significant difference in tolerance provided by the 65 degrees seat over that provided by the 13 degrees and 45 degrees seats in the 5- to 7-G range, and a significant difference in tolerance provided by the 45 degrees and 65 degrees seats over that provided by the 13 degrees seat in the 4- to 5-G range. Two-dimensional reconstructions of the superior half of mean binocular vision remaining at the various levels of G stress showed complete visual loss near 5 G in the 13 degrees seat, complete loss near 6 G in the 45 degrees seat, and substantial peripheral vision remaining at 7 G in the 65 degrees seat.

Aerospace Medicine↗
PubMed1977

Transfer functions for eye-level blood pressure during +Gz stress.

A description of the eye-level blood-pressure response to +Gz stress in relaxed humans was obtained as an empirical, ensemble-average, G-to-blood-pressure transfer function based on three subjects' responses to a total of 23 simulated aerial combat maneuvering runs on the USAFSAM human centrifuge. Three different analytic transfer functions were fitted to the empirical function for frequencies from 5 to 200 mHz, and predictive performance of the empirical and three analytic functions was examined. The double-zero, double-pole mathematical model most closely fit the empirical transfer function and displayed reasonable predictive ability.

Adult↗
PubMed1976

Physiologic and anti-G suit performance data from YF-16 flight tests.

Biomedical data were collected during high-G portions of 11 YF-16 test flights. Test pilots monitored revealed increased respiratory rate and volume, decreased tidal volume, and increased heart rate at higher G levels, with one pilot exhibiting various cardiac arrhythmias. Anti-G suit inflation and pressurization lags varied inversely with G-onset rate, and suit pressurization slope was near the design value.

Adaptation, Physiological↗
PubMed1976

Changes in clinical cardiologic measurements associated with high +Gz stress.

Because of reports of subendocardial hemorrhage and myofibrillar degeneration in animals exposed to sustained high G loads (greater than +6 Gz for 15 s or more), questions have been raised regarding the safety of exposing pilots and human subjects to the similar G-stress levels likely to be encountered in the new high-performance fighter aircraft. Noninvasive clinical cardiologic data, including ECGs, vectorcardiograms, systolic time intervals, and maximal treadmill stress tests, were obtained from two groups of subjects before and at several times after exposure to high-G stress. The group exposed to the greater G stress (three 40-s runs at 8 G and two 40-s runs at 10 G, all in one day) developed moderate cutaneous petechiasis and had other minor physical findings after the G stress, but showed few significant changes in cardiologic data: serum total CPK and LDH levels rose, and preejection period shortened at 48 h poststress. The group exposed to the lesser G stress (one 100-s variable-G maneuver peaking twice at 8 G for 3 s, once a week for 3 weeks) had no symptoms following the G stress, but the vectorcardiograms revealed transient T-loop angle changes, and preejection period measured at 1 week poststress was significantly decreased. Because the serum enzyme changes were noncardiac in origin, and because the few other changes were not in a direction indicative of cardiac damage, we conclude that the G stresses imposed in these studies were not significantly injurious.

Electrocardiography↗
PubMed1975

Transfer functions for arterial oxygen saturation during +Gz stress.

Discrete, finite, Fourier transforms of input +Gz stress and output arterial oxygen saturation (Sao2) were used to obtain transfer functions between G and Sao2 in 12 subjects. Ensemble averaging of transfer functions based on responses to variable G stress provided reasonable capability for predicting Sao2 responses to sustained 6-G stress. Prediction of responses to variable G stress from transfer functions based on responses to sustained G stress was unsuccessful, however. A synthetic transfer function with physiologic explicability and substantial predictive ability was obtained from an impulse response fabricated from simple mathematical functions.

Aerospace Medicine↗