CITATION:
Chan TC, Clausen J.
Reply To The Letter To The Editor, from Howard JD and Reay DT.
Ann Emerg Med July 1998; 32(1):117-118.
Although the "old" version of this letter remains on this page,
in December, 2005, I created and posted a PDF file of it!
If you're going to print it, I strongly suggest you print it from the PDF file:
Chan et al Reply to
Howard and Reay's Letter
CORRESPONDENCE section:
Reply To The Letter To The Editor, from Howard JD and Reay DT.
Ann Emerg Med July 1998; 32(1):117-118.
In reply:
We thank Reay et al for their interest in the sudden deaths of physically restrained individuals in custody and appreciate the opportunity to discuss our study recently published in the Annals as well as prior work on the subject.(1)
We agree sudden deaths of individuals in custody remains a complex issue and determining the cause of death in these cases is difficult. Our study focused on one issue: whether body position in the "hogtie" or "hobble" restraint position leads to respiratory dysfunction to the point that an individual is at risk for asphyxiation.
The study by Reay et al reported in 1988 that healthy volunteers placed in the prone hogtie restraint position had prolonged recovery times for oxygen saturation and heart rate after mild exercise; observations appropriately summarized by the limited claim that "the study found positional restraint to have measurable physiologic effects."12) Unfortunately, others have interpreted reports in the literature as evidence the restraint position causes death from asphyxiation by impeding chest and abdominal movement.(3-5)
There were significant limitations to the 1988 study and we, therefore, concluded these findings needed confirmation. First, their study used cutaneous oximetry, an indirect measure of blood oxygenation, which is frequently inaccurate under conditions of exercise.(6,7) Second, their study reported oxygen desaturations down to 85%, substantially lower than what would have been expected at such relatively mild exercise levels in healthy subjects.(8,9) Finally, a single outlier significantly skewed their data on oxygen saturation recovery: whereas the mean increase was 68%, the median difference was only 13% (less than 8 seconds, a finding that is of marginal clinical and physiologic significance).(2)
Our study used direct assessments of blood oxygenation from arterial blood gas analyses as well as cutaneous oximetry. None of these measures demonstrated evidence of hypoxia or desaturation when subjects were in the restraint position after exercise and, in fact, mean PaO2 increased when compared with measurements in the sitting position before exercise.(1) In addition, direct measurements of PCO2 showed no evidence of limitations of ventilation in the restraint position and, in fact, mean PCO2 values were lower than at sitting rest. Finally, even though the levels of exercise were greater, we found no significant difference in heart rate recovery in the restraint position versus controls.(1)
We did observe measurable physiologic effects on pulmonary mechanics when results in various body positions were compared, reflecting expected effects of posture on pulmonary physiology. Placing unrestrained subjects in the supine position resulted in lower values for FVC, FEV1, and maximal voluntary ventilation as compared with sitting, which were statistically significant. However, the clinical or forensic relevance of such physiologic effects requires thoughtful consideration unless, for example, one is prepared to recommend the sitting position during sleep to prevent asphyxiation.
Reay et al suggest our findings may not be applicable by citing the example of low blood morphine levels at times found in individuals who have died of opiate intoxication. Asphyxiation, however, is directly related to oxygenation and ventilation. Thus measuring these physiologic parameters gives a clear indication of respiratory function and concomitant risk of asphyxiation.
As our study focused on the impact of the restraint position on respiratory function, we made no comment on the issue of "restraint stress" other than to state that factors such as "drug use . . . physiological stress, hyperactivity, hyperthermia, catechol hyperstimulation, and trauma resulting from struggle may be more important factors in the deaths of these individuals."(1) To what extent any restraint causes increased physiologic stress and its contribution to custody death remains speculative.
We disagree with the suggestion made by Reay et al that only forensic pathologists have "insight into the spectrum of illness, injury, and death that occur . . . in the 'street'" and that these "are not well known to clinicians." As emergency physicians we confront these same issues in dealing with acutely ill patients, and believe our insight may be of value in understanding the factors and challenges associated with these deaths.
We agree additional studies should be conducted to further elucidate the pathophysiology behind these cases in the future. Improving the methods used by public safety officers and medical personnel for restraining violent individuals would be substantially expedited by the availability of scientific and clinical studies identifying the specific causes of mortality and morbidity during restraint. It would also be expedited by thoughtful and expert consideration of the results from such studies.
Theodore C Chan, MD
Gary M Vilke, MD
Tom Neuman, MD
Department of Emergency Medicine
Jack Clausen, MD
Pulmonary Division, Department of Medicine
University of California San Diego Medical Center
San Diego, CA
References
1. Chan TC, Vilke GM, Neuman T, et al: Restraint position and positional asphyxia. Ann Emerg Med 1997;30:578-586.
2. Reay DT, Howard JD, Fligner CL, et al: Effects of positional restraint on oxygen saturation and heart rate following exercise. Am J Forensic Med Pathol 1988;9:16-18.
3. Reay DT, Fligner CL, Stilwell AD, et al: Positional asphyxia during law enforcement transport. Am J Forensic Med Pathol 1992;13:90-95.
4. O'Halloran RL, Lewman LV: Restraint asphyxiation in excited delirium. Am J Forensic Med Pathol 1993;14:289.
5. Stratton SJ, Rogers C, Green K: Sudden death in individuals in hobble restraints during paramedic transport. Ann Emerg Med 1995;25:710-712.
6. Barthelemy JC, Geyssant A, Riffat J, et al: Accuracy of pulse oximetry during moderate exercise: A comparative study. Scand J Clin Lab Invest 1990;50:533-539.
7. Norton LH, Squires B, Craig NP, et al: Accuracy of pulse oximetry during exercise stress testing. Int J Sports Med 1992;13:523-527.
8. Whipp BJ, Wasserman K: Alveolar-arterial gas tension differences during graded exercise. J Appl Physiol 1969;27: 361-365.
9. Hammond MD, Gale GE, Kapitan KS, et al: Pulmonary gas exchange in humans during exercise at sea level. J Appl Physiol 1986;60:1590-1598.
Email Charly at: c-d-miller@neb.rr.com