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PubMed2003

[Means and methods of improving pilot's tolerance for g-loads following an extended flight in a one-seat fighter].

G-loads tolerance following hypodynamia during extended flights and effectiveness of countermeasures against possible negative impacts were studied. Subjects performed 5-hr simulated flights after which they were centrifuged with a g-gradient of 0.1 u/s in the relaxed state, and with a g-gradient of 1.0 u/s at complex-profiled 2 to 9 units in anti-g suit VKK-15. Tested were three sets of countermeasures (A, B, C) combining the following methods: physical exercises, VKK-15 provided massage of the lower body, 30-s exposure to 5 g, use of the profiled stiff and cushioned seats, electrical stimulation of the back and waist, and an air-cushion. The countermeasures were applied every hour on flight. Hypodynamia during the five-hour fighter flight was shown to have a weak detrimental effect on the pilot's functional state, performance and g-tolerance which were tempered by the proposed combinations of countermeasures.

Adult↗
PubMedDate not supplied

The conductivity of dialysis fluid.

Dialysis fluid consists of a solution of inorganic salts that are dissociated in electrically charged ions. These ions can move in an electric field giving the salt solution electrically conducting properties, called conductivity. The conductivity of the dialysis fluid is a parameter well suited for measuring the total concentration of salt. The conductivity is easy to measure with reasonable accuracy and the measuring device is usually very stable over time. It can be used for both proportioning and monitoring of the concentrate intermixing. The conductivity behaviour of a salt solution is however complicated and depends in a non-linear way on temperature, total salt concentration and salt/glucose composition. The accuracy of the conductivity measurement is given by the calibration. A successful calibration requires good knowledge about the measuring device and the calibration solutions.

Calibration↗
PubMedDate not supplied

Accuracy of intravenous infusion pumps in continuous renal replacement therapies.

Most extracorporeal continuous renal replacement therapies (CRRT) require inflow pumping of either dialysate, filtrate replacement solution, or both. Outflow of spent dialysate and ultrafiltrate can be accomplished by gravity drainage or pump. Intravenous infusion pumps have been commonly used for these purposes, although little is known about the accuracy of these pumps. To evaluate accuracy of two different types of intravenous infusion pumps used in CRRT, we studied flow rates at nine different pressure variations in three piston type and three linear peristaltic pumps. The results showed that error of either pump was not different for flow rates of 4 and 16 ml/min. Both types of pumps were affected by fluid circuit pressures, although pressure conditions under which error was low were different for each pump type. The linear peristaltic pumps were most accurate under conditions of low pump inlet pressure, whereas piston pumps were most accurate under conditions of low pump pressure gradient (outlet minus inlet) of 0 or -100 mmHg. The magnitude of error outside these conditions was substantial, reaching 12.5% for the linear peristaltic pump when inlet pressure was -100 mmHg and outlet pressure was 100 mmHg. Error may be minimized in the clinical setting by choosing the pump type best suited for the pressure conditions expected for the renal replacement modality in use.

Equipment Design↗
PubMedDate not supplied

Physiological and biomechanical considerations for a human Mars mission.

Evolving on Earth has made humans perfectly adapted, both physiologically and biomechanically, to its gravity and atmospheric conditions. Leaving the Earth and its protective environment, therefore, results in the degradation of a number of human systems. Long-duration stays on the International Space Station (ISS) are accompanied by significant effects on crew's cardiovascular, vestibular and musculoskeletal systems. Bone loss and muscle atrophy are experienced at a rate of 1-3% and 5% per month respectively, while VO2 (oxygen consumption) measurements are reduced by approximately 25% after a few weeks in space. If these figures are simply extrapolated, a future human mission to Mars will be seriously jeopardised and crews may find they cross the threshold of bone and muscle loss and aerobic fitness--ultimately with them being unable to return to Earth. When arriving on Mars, considerable biomechanical alterations will also occur. Optimum walking speeds will be approximately 30% lower and transitioning from a walk to a run will occur at a speed 25% slower. Peak vertical forces will be reduced by as much as 50%, while stride length, stride time and airborne time will all increase. On Mars, half as much energy will be required to travel the equivalent distance on Earth and it will be 65% more economical to run rather than to walk.

Acceleration↗