Cardiopulmonary responses to combined lateral and vertical acceleration.

To investigate the effects of a lateral G force, eight stress panel members were each subjected to a series of stresses using +/- 1.5, 2, or 2.5 Gy combined with either +/- 1 or +/- 2 Gz, for 30 s followed by a 60-s recovery period. Peripheral arterial oxygen saturation, utilizing a Hewlett-Packard 47201A ear oximeter and heart rate were recorded. A consistent fall in arterial oxygen saturation (SaO2) was observed during all the Gy/Gz exposures with the +Gy direction giving the lowest value of 90.1% SaO2 (PaO2 of less than 60 mmHg). A small but consistent increase in heart rate (HR) was also observed during, and for 15 to 20 s after the Gy/Gz exposure. These results indicate that the cardiopulmonary system is stressed during combined Gy/Gz acceleration and the most important change occurs in SaO2.

Cardiac function monitored by impedance cardiography during changing seatback angles and anti-G suit inflation.

Impedance cardiography (IC) appears to be a promising noninvasive technique for monitoring small changes in pilot cardiovascular status during conditions simulating flight. Heart rate (HR), stroke volume (SV), cardiac output (CO), ventricular ejection time (VET), and thoracic impedance (Zo) were monitored in ten volunteers for 5 min at each of four seatback angles from vertical: 12 degrees, 30 degrees, 45 degrees, and 60 degrees. Data were also obtained at three seatback angles (12 degrees, 30 degrees, 60 degrees) for 6 min each before, during, and after inflation of the standard USAF anti-G suit to 1.5 psi. Significant differences (p less than 0.05) in HR, SV, CO, VET and Zo were observed among the four positions. Inflation of the standard anti-G suit to 1.5 psi at 1.0 +Gz did not significantly alter HR, SV, or CO; whereas, 1 min of deflation of the anti-G suit significantly altered HR, SV, CO compared to inflation values. The results suggest IC can detect small differences in HR, SV, CO, VET, and Zo within subjects as a function of minor changes in body position.

Temperature changes during exercise measured by thermography.

The present study explores the dynamic changes of surface temperatures associated with peripheral vascular shifts during and following hand gripping, one-legged ergometric, and running exercise. An AGA 680 thermovision system, incorporating a Bolex 16-mm camera and displaying 10-colored isotherms on a slave monitor, generated synchronous infrared (IR) movies at 16 frame/s. Incremental increases in surface skin temperatures (Ts) were observed while gripping at 20, 50, and 80% of maximum with a peak rise of 1.7 degrees C. Thermographic recorded Ts changes during dynamic one-legged exercise were higher in the exercising leg than the resting leg. Surface temperatures dropped in both limbs following exercise. The advantages of the use of thermography during transient thermal states, as produced by dynamic exercise, is supported by comparative Ts data taken from thermograms and thermistors.

Thermographic evaluation of the relative heat loss by area in man after swimming.

Regional differences in skin temperature (Ts) were determined by infrared radiography in four competitive swimmers of varying body compositions, prior to, after 5 min of immersion in water (Tw) at 23.5 degrees C, and after a 500-m freestyle swim at a training pace. Decreases in skin temperature that correlated with skinfold thickness were seen post-immersion (r = 0.56, p less than 0.05). After swimming, skin temperatures were highest in regions overlying active muscle masses and were independent of skinfold thickness. These regions were the deltoids, trapezius, triceps and biceps brachi, and pectorals. Swimming increased the extent of warmer skin surface areas and gradient Ts-Tw, over which heat loss could occur.

Jackrabbit ears: surface temperatures and vascular responses.

Blood flow to the ear pinnae is curtailed at ambient temperatures of between 1.4 degrees and 24 degrees C, which minimizes heat loss across the pinnae and allows the surfaces of erect pinnae to approach ambient temperature. The pinnae are warmed by steady or pulsatile vasodilation in some animals when the ambient temperature is between 1 degree and 9 degrees C below body temperature, a response favoring heat loss. When ambient temperature exceeds body temperature by 4 degrees to 5 degrees C, the pinnae are circulated with blood cooler than ambient temperature; this response favors heat influx.