Correlation between blood alcohol concentration (BAC), breath alcohol concentration (BrAC) and psychomotor evaluation in a clinical monitored study of alcohol intake in Brazil

Policies that establish maximum blood alcohol concentrations (BACs) or breath alcohol concentration (BrACs) for drivers while driving can reduce traffic accidents by approximately 20%. In Brazil, the National Transit Council (CONTRAN) considers positive BAC and/or BrAC tests or signs of psychomotor capacity alterations as evaluated by a police authority to be an administrative infraction or even a crime. The observed clinical symptoms of alcohol intoxication based on a subject's appearance may not necessarily reflect the quantified BAC and/or BrAC. This study compared the clinical symptoms identified by a medical authority (M) and a non-medical authority (NM) with BAC and BrAC measurements. Brazilian health volunteers (n = 15) drank ethanol (40% v/v) and, at scheduled times, the subjects underwent blood draws for BAC analysis, were tested for BrAC analysis, and underwent psychomotor alteration assessments performed by M and NM. Concentration-time profiles of the BACs and BrACs of the volunteer subjects were generated. The BAC values reached a peak at 60 min and subsequently decreased with time. The average BrAC values decreased with time after ingestion. During the evaluations, M was able to identify a lack of static equilibrium until 240 min and a lack of dynamic equilibrium until 120 min. A lack of upper limb motor coordination was observed until 90 min, and a lack of coordination in the lower limbs was observed only during the first hour. Regarding the tests performed by NM, the signs related to the subjects' appearances were observed more frequently, until 60 min. The other analyzed symptoms were not identified. Naturally, the signs reported by both M and NM disappeared with time. The evaluations of psychomotor changes performed by Brazilian M were superior to those performed by NM. However, independent of the examiner, at the alcohol concentrations reached in this study, the psychomotor alteration evaluations were ineffective compared with the BAC and BrAC results.