CARDIOVASCULAR CHANGES IN HUMANBODY AFTER CHANGING POSITION SUPINE TO PRONE

Prone position is known to be accompanied by several physiologic changes, but they are not described comprehensively in modern literature and sometimes controversial. Aim was to examine cardio-vascular changes in non-anesthetized humans after turning them into prone position and influence on these changes by age and body mass index. We performed an observational prospective study without control group of 200 (118 male and 82 female) patients 18-75 y.o. The patients were examined the day before elective lumbar spine surgery using thoracic electrical bioimpedance and non-invasive measurement of blood pressure in supine position (SP), 5 min and 20 min after turning into prone position (PP5 and PP20). Diastolic BP increased significantly after turning (PP5) and stayed increased during the time of investigation (PP20). Stroke volume index (SVI) decreased after turning into prone position (PP5 and PP20) by 18%. Systemic vascular resistance index (SVRI) increased by 34% (PP5). The duration of asynchronous contraction phase increased by 35% and the duration of all ejection phases decreased after changing the position from supine to prone. Rapid ejection reduced by 30%, reduced ejection - by 7%. We found the influence of age >60 y.o. on increasing of SVRI (p=0.006) and influence of age > 60 y.o. and BMI > 25 on decreasing of SVI (p=0.01 and p=0.04 respectively). In healthy non-anesthetized people turning from supine to prone position leads to decreasing of SVI by 18%, increasing of SVRI by 34% and increasing of diastolic blood pressure increased by 7%. Changes of SVRI are influenced by age and changes of SVI are influenced by age and BMI. Positioning prone are accompanied by shortening of both ejection periods and prolonging of asynchronous contraction period.