The prone position slightly increased free water clearance (447 vs 349 ml/6 h, P=0.05) and reduced stroke volume (102 vs 122 ml, P<0.05) compared with the supine position in healthy males.
Does the prone or lateral position alter cardiovascular and renal variables compared to the supine position in healthy males?
The prone position reduces stroke volume and increases sympathetic nervous activity compared to the supine position in healthy males, likely due to mechanical compression of the thorax.
Absolute Event Rate: 447% vs 349%
p-value: p=0.05
The hypothesis was tested that changing the direction of the transverse gravitational stress in horizontal humans modulates cardiovascular and renal variables. On different study days, 14 healthy males were placed for 6 h in either the horizontal supine or prone position following 3 h of being supine. Eight of the subjects were in addition investigated in the horizontal left lateral position. Compared with supine, the prone position slightly increased free water clearance (349 +/- 38 vs. 447 +/- 39 ml/6 h, P = 0.05) and urine output (1,387 +/- 55 vs. 1,533 +/- 52 ml/6 h, P = 0.06) with no statistically significant effect on renal sodium excretion (69 +/- 3 vs. 76 +/- 5 mmol/6 h, P = 0.21). Mean arterial pressure and left atrial diameter were similar comparing effects of supine with prone. The prone position induced an increase in heart rate (54 +/- 2 to 58 +/- 2 beats/min, P < 0.05), total peripheral vascular resistance (13 +/- 1 to 16 +/- 1 mmHg. min(-1). l(-1), P < 0.05), forearm venous plasma concentration of norepinephrine (97 +/- 9 to 123 +/- 16 pg/ml, P < 0.05), and atrial natriuretic peptide (49 +/- 4 to 79 +/- 12 pg/ml, P < 0.05), whereas stroke volume decreased (122 +/- 5 to 102 +/- 3 ml, P < 0.05, n = 6). The left lateral position had no effect on renal variables, whereas left atrial diameter increased (32 +/- 1 to 35 +/- 1 mm, P < 0.05) and mean arterial pressure decreased (90 +/- 2 to mean value of 85 +/- 2 mmHg, P < 0.05). In conclusion, the prone position reduced stroke volume and increased sympathetic nervous activity, possibly because of mechanical compression of the thorax with slight impediment of arterial filling. The mechanisms of the slightly augmented urine output in prone position require further experimentation.
Pump et al. (Mon,) conducted a other in Healthy (n=14). Prone position vs. Supine position was evaluated on Free water clearance (p=0.05). The prone position slightly increased free water clearance (447 vs 349 ml/6 h, P=0.05) and reduced stroke volume (102 vs 122 ml, P<0.05) compared with the supine position in healthy males.