Evaluation of the ventilatory effects on human subjects in prolonged hip-flexed/head-down restraint position

The restraint chair is a tool used by law enforcement and correction personnel to control aggressive, agitated individuals. When initiating its use, subjects are often placed in a hip-flexed/head-down (HFHD) position to remove handcuffs. Usually, this period of time is less than two minutes but can become more prolonged in particularly agitated patients. Some have proposed this positioning limits ventilation and can result in asphyxia. The aim of this study is to evaluate if a prolonged HFHD restraint position causes significant ventilatory compromise.

Subjects exercised on a stationary bicycle until they reached 85% of their predicted maximal heart rate. They were then handcuffed with their hands behind their back and placed into a HFHD seated position for five minutes. The primary outcome measurement was maximal voluntary ventilation (MVV). This was measured at baseline, after initial placement into the HFHD position, and after five minutes of being in the position while still maintaining the HFHD position. Baseline measurements were compared with final measurements for statistically significant differences.

We analyzed data for 15 subjects. Subjects had a mean MVV of 165.3 L/min at baseline, 157.8 L/min after initially being placed into the HFHD position, and a mean of 138.7 L/min after 5 min in the position. The mean baseline % predicted MVV was 115%; after 5 min in the HFHD position the mean was 96%. This 19% absolute difference was statistically significant (p = 0.001).

In healthy seated male subjects with recent exertion, up to five minutes in a HFHD position results in a small decrease in MVV compared with baseline MVV levels. Even with this decrease, mean MVV levels were still 96% of predicted after five minutes. Though a measurable decrease was found, there was no clinically significant change that would support that this positioning would lead to asphyxia over a five-minute time period.