Evaluation of the ventilatory effects of the prone maximum restraint (PMR) position on obese human subjects

The study sought to determine the physiologic effects of the prone maximum restraint (PMR) position in obese subjects after intense exercise. We designed an experimental, randomized, cross-over trial in human subjects conducted at a university exercise physiology laboratory. Ten otherwise healthy, obese (BMI>30) subjects performed a period of heavy exertion on a cycling ergometer to 85% of maximum heart rate, and then were placed in one of three positions in random order for 15min: (1) seated with hands behind the back, (2) prone with arms to the sides, (3) PMR position. While in each position, mean arterial blood pressure (MAP), heart rate (HR), minute ventilation (V˙E), oxygen saturation (SaO2), and end tidal CO2(etCO2) were measured every 5min. There were no significant differences identified between the three positions in MAP, HR, V˙E, or O2sat at any time period. There was a slight increase in heart rate at 15min in the PMR position over the prone position (95 vs. 87). There was a decrease in end tidal CO2 at 15min in the PMR over the prone position (32mmHg vs. 35mmHg). In addition, there was no evidence of hypoxia or hypoventilation during any of the monitored 15min position periods.