Effective patient blinding during hyperbaric trials.

Hyperbaric medicine is applied for several disease states. Laboratory evidence is compelling but clinical efficacy remains incompletely validated. The standard by which supportive research is measured is termed evidence-based medicine, with results of randomized, blinded trials being most desirable. Blinding patients during hyperbaric exposure poses unique challenges. Few such studies are reported and confirmation of its success lacking. A study of patients suffering radiation-induced proctitis was conducted. It involved blinding of sham controls via a minimal air compression technique. Prior to unblinding 72 patients were surveyed using a standardized questionnaire to determine if they had been aware of their treatment allocation. Twenty of the 33 in the treatment group answered that they were in the treatment group, one answered sham and 12 did not know. Twenty-three of 39 in the sham group thought they were in the treatment group, two said sham and 14 did not know. A Chi-square analysis detected no relationship between what treatment was provided and what patients thought they received (p = 0.9058). Eliminating those who did not know, a Kappa statistic was p = 0.0299, indicating that there was no agreement beyond chance. Minimal air compression is an effective blinding tool for patients enrolled in hyperbaric trials.