RETENTION OF INHALED ACETALDEHYDE IN MAN

¹ Department of Pharmacology, Medical College of Virginia, Richmond, Virginia

This study was conducted with the objectives of determining the percentage of inhaled acetaldehyde retained upon varying the ventilatory rate, depth of inhalation and concentration of acetaldehyde inhaled. In these experiments eight subjects inhaled-acetaldehyde vapor (0.1-0.8 µg/ml) from a recording respirometer. Experiments were performed to measure total respiratory tract retention by both mouth breathing and nose breathing. The percentage retained was calculated from the difference in acetaldehyde in the system before and after the inhalation period and the amount inhaled. Analysis of acetaldehyde was by a colorimetric method with 3-methyl-2-benzothiazolinone hydrazone. The retention of acetaldehyde was found to range from 45 to 70% as the respiratory rate was decreased from 40 to 5/min. There was no difference between mouth breathing and nose breathing in total retention. Experiments involving oral uptake alone showed an inverse relationship between retention and flow rate through the mouth. Varying the tidal volume over a broad range did not affect uptake when other factors remained constant. There was a tendency for percent retention to decline as the concentration inhaled increased. A direct relationship was found between contact time and uptake, independent of rate. It is concluded that percent retention of acetaldehyde under these conditions is dependent primarily upon the duration of the ventilatory cycle.