Evaluation of Cardiac Circadian Rhythm Deconditioning Induced by 5-to-60 Days of Head-Down Bed Rest.

Head-down tilt (HDT) bed rest elicits changes in cardiac circadian rhythms, generating possible adverse health outcomes such as increased arrhythmic risk. Our aim was to study the impact of HDT duration on the circadian rhythms of heart beat (RR) and ventricular repolarization (QTend) duration intervals from 24-h Holter ECG recordings acquired in 63 subjects during six different HDT bed rest campaigns of different duration (two 5-day, two 21-day, and two 60-day). Circadian rhythms of RR and QTend intervals series were evaluated by Cosinor analysis, resulting in a value of midline (MESOR), oscillation amplitude (OA) and acrophase (φ).

Beat-to-beat agreement of noninvasive tonometric and intra-radial arterial blood pressure during microgravity and hypergravity generated by parabolic flights.

Background: Accurate measurement of beat-to-beat arterial blood pressure is essential for understanding the cardiovascular adaptation to weightlessness; however, the intra-arterial standard of beat-to-beat blood pressure measurement has never been used during space flight because of its invasive nature.

Objectives: The aim of the present study was to compare noninvasive radial artery tonometry blood pressure measurement with intra-radial pressure measurement during microgravity and hypergravity generated by parabolic flights.

Methods: Two study participants, equipped with an intra-radial pressure line on the left arm and a Colin CBM-7000 (Colin Corp.

Microsurgery in microgravity is possible.

The aim of this experiment was to evaluate the feasibility of a microsurgical procedure in the context of microgravity during parabolic flights. The surgical procedure included the sectioning and repair of a rat sciatic nerve and tail artery with 10/0 monofilament sutures. Both procedures were successful.

Variations of intrathoracic amount of blood as a reason of ECG voltage changes.

Background: It is known that electroconduction of intrathoracic organs and tissues significantly influences the ECG voltage. It changes during therapy or exercise test due to redistribution and/or volume variations of blood and body fluids and their electroconductivity variations. This fact must be taken into consideration during interpretation of corresponding ECG.