Adaptation of Systemic and Pulmonary Circulation to Acute Changes in Gravity and Body Position
INTRODUCTION: Changes in gravity or body position provoke changes in hydrostatic pressure in the arterial system and in venous return. Potential asymmetries between left (QLV) and right ventricular (QRV) cardiac output during transient gravity changes were
investigated. It was hypothesized that blood volume is temporarily stored in the pulmonary vessels, with amount and duration depending on the level and directions of gravity.
METHODS: Eight healthy, male subjects (32 ± 3 yr, 182 ± 7 cm, 82 ± 6 kg) were tested on a tilt seat (TS), in a long arm human centrifuge (laHC), and during parabolic flights (PF). The gravitational changes during PF were reconstructed by changing gravity in a laHC and different body positions on a TS. All participants were tested in the seated, resting position. Heart rate and blood pressure were recorded continuously and QLV was calculated, applying the Modelflow Algorithm. Gas exchange was measured breath-by-breath. QRV was calculated from these data according to the Fick Principle. Four sequences were superimposed and analyzed by ANOVA with the factors Time, Ventricle (QRV, QLV), and Mode (TS, PF, laHC).
RESULTS: After reductions in gravity QRV and QLV were transiently desynchronized. ANOVA showed no main effect for Mode, but significant changes were found for Time and Ventricle and all interactions.
DISCUSSION: Phases of reduced gravity seem to lead to transiently increased storage of blood volume inside the pulmonary vascular system. A more detailed understanding of these mechanisms might help to describe the compliance of the pulmonary vascular system in diseases of the pulmonary circulation.
Hoffmann U, Koschate J, Appell Coriolano H-J, Drescher U, Thieschäfer L, Dumitrescu D, Werner A. Adaptation of systemic and pulmonary circulation to acute changes in gravity and body position. Aerosp Med Hum Perform. 2019; 90(8):688–695.
METHODS: Eight healthy, male subjects (32 ± 3 yr, 182 ± 7 cm, 82 ± 6 kg) were tested on a tilt seat (TS), in a long arm human centrifuge (laHC), and during parabolic flights (PF). The gravitational changes during PF were reconstructed by changing gravity in a laHC and different body positions on a TS. All participants were tested in the seated, resting position. Heart rate and blood pressure were recorded continuously and QLV was calculated, applying the Modelflow Algorithm. Gas exchange was measured breath-by-breath. QRV was calculated from these data according to the Fick Principle. Four sequences were superimposed and analyzed by ANOVA with the factors Time, Ventricle (QRV, QLV), and Mode (TS, PF, laHC).
RESULTS: After reductions in gravity QRV and QLV were transiently desynchronized. ANOVA showed no main effect for Mode, but significant changes were found for Time and Ventricle and all interactions.
DISCUSSION: Phases of reduced gravity seem to lead to transiently increased storage of blood volume inside the pulmonary vascular system. A more detailed understanding of these mechanisms might help to describe the compliance of the pulmonary vascular system in diseases of the pulmonary circulation.
Hoffmann U, Koschate J, Appell Coriolano H-J, Drescher U, Thieschäfer L, Dumitrescu D, Werner A. Adaptation of systemic and pulmonary circulation to acute changes in gravity and body position. Aerosp Med Hum Perform. 2019; 90(8):688–695.
Keywords: pulmonary circulation; systemic circulation; transient gravity changes
Document Type: Research Article
Publication date: 01 August 2019
- This journal (formerly Aviation, Space, and Environmental Medicine), representing the members of the Aerospace Medical Association, is published monthly for those interested in aerospace medicine and human performance. It is devoted to serving and supporting all who explore, travel, work, or live in hazardous environments ranging from beneath the sea to the outermost reaches of space. The original scientific articles in this journal provide the latest available information on investigations into such areas as changes in ambient pressure, motion sickness, increased or decreased gravitational forces, thermal stresses, vision, fatigue, circadian rhythms, psychological stress, artificial environments, predictors of success, health maintenance, human factors engineering, clinical care, and others. This journal also publishes notes on scientific news and technical items of interest to the general reader, and provides teaching material and reviews for health care professionals.
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