Sudden death during restraint: do some positions affect lung function?

Abstract

Small but significant numbers of people die during restraint following violent incidents. Current guidance within the NHS states that all restraint positions should be considered to present equal risk. We used a repeated measures design to compare lung function in four restraint positions with a standing control position. Participants restrained flat on the floor, prone or supine, showed non-significant reductions in forced vital capacity (FVC) and forced expiratory volume FEV1 compared with the standing control position. Participants restrained face down with the body weight of the restraining persons pressed on their upper torso and/or in a flexed restraint position showed a significant reduction in lung function (mean reductions in FVC of 23.8% and 27.4% respectively). Recommendations that all restraint positions pose equal risk, or that all prone restraint is dangerous, are not supported by these findings. Some, but not all, prone restraint positions show significant restriction of lung function.

A review of the scientific literature related to the adverse impact of physical restraint: gaining a clearer understanding of the physiological factors involved in cases of restraint-related death

“…Since spirometry measures were the variable that showed the most dramatic and consistent reduction as a consequence of restraint, we calculated where possible the effect size (ES) and 95% confidence intervals. The percentage reductions given above and the ES calculations of 23.1, 20.8, 20.5 and 21.5 for FVC and 23.9, 21.2, 20.7 and 21.5 8,9,13,16 for FEV1, respectively, and tidal volume ES of 20.4 11 shows the restraint positions investigated can be expected to reduce lung volumes.…”

“…8,17 Three studies 9,11,15 measured maximal voluntary ventilation finding that it is reduced by between 23% and 35%. Reductions observed in ventilatory capacity were proportional to the degree of external restriction imposed upon participants either by having weight applied to the back when lying prone, 12,13,15,16 lying prone with abdominal compression, 11 sitting in a flexed position, 17 sitting flexed and being increasingly obese. 17 One study 13 found that a longer duration of hog-tie restraint (5 minutes vs. 1 minute) resulted in a further 5.1% decrease in spirometry values.…”

“…'Some, but not all, prone restraint positions cause significant restriction of lung function [and] some restraint positions are demonstrated to present a greater risk than others' ( p. 141). 16 The stresses imposed during restraint ( physical, pharmacological, psychological) need to be considered as cumulative with future research seeking to tease out the exact contribution of each element. Future research should also seek to investigate the effect of other restraint positions/techniques on populations other than apparently healthy male adults.…”

Death in Abnormal Positions: Physical Restraint

“…handcuffs) to straps, may impair breathing non-trivially when the subject is prone (i.e. More recent controlled laboratory studies comparing four different restraint positions prompted the investigators to conclude that some positions are riskier than others, and caused a significant deterioration in pulmonary function (Parkes 2008). To conclude that restraint asphyxia was causal in death, the forensic pathologist should consider the following features: 1.…”

Perceptions of supported and unsupported prone‐restraint positions

“…). Parkes & Carson () and Parkes et al . () demonstrated that seated restraint could match and in some cases exceed the ventilatory compromise observed in the prone position.…”