Aviat Space Envir Md
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Aviat Space Envir Md · Aug 1999
ReviewThe non-invasive assessment of stroke volume and cardiac output by impedance cardiography: a review.
Impedance cardiography (IC) is an inexpensive, reliable and noninvasive technique for determining stroke volume (SV) and cardiac output (CO). It relies on the measurement of phasic changes in transthoracic electrical resistivity, related to ejection of blood into the ascending aorta with each heart beat. Because of its non-invasive nature, IC is becoming increasingly used in clinical settings, as well as in many areas of physiological research. ⋯ The question of accuracy of IC in terms of absolute values of SV and CO remains to be determined. The methodological limitations, accuracy, reliability and reproducibility of IC are examined, as are some of the methods developed to improve these aspects of the technique. The application and utility of IC in aerospace medicine research is also addressed.
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Aviat Space Envir Md · Aug 1999
Comparative StudyPositive pressure generation by pneumatic and electronic O2 regulators: a bench experimental evaluation.
The introduction of advanced anti-G protection into agile fast fighter aircraft may result in the regular use of positive pressure breathing (PPB) for G protection by aircrew. Since PPB results in an external additional work of breathing (WoB), we compared the mechanical performance of the pneumatic and electronic O2 regulators designed for "Mirage 2000" and "Rafale" aircraft. ⋯ We concluded that the electronic control of mask pressure is relatively efficient but that the device would be improved by placing the site of the pressure measurement into the mask.