The psychometric and cardiac effects of pseudoephedrine in the hyperbaric environment

Study Objectives. To examine the psychometric and cardiac effects of pseudo ephedrine at 1 and 3 atmospheres (atm) of pressure (0 and 66 feet of sea wa ter, respectively), and to make recommendations about the agent's safety in the diving environment. Design. Double-blind, placebo-controlled, crossover study. Setting. Monoplace hyperbaric chamber of a university hospital. Subjects. Thirty active divers (mean age 38 yrs). Intervention. A bank of seven tests was used to assess cognitive function d uring four different simulated dive combinations: placebo-1 atm, placebo-3 atm, pseudoephedrine-l atm, and pseudoephedrine-3 atm. Measurements and Main Results. Heart rate and cardiac rhythm were recorded during all dives. Repeated-measures analysis of variance was used to analyz e the effects of pseudoephedrine, depth, and drug-depth interaction. No sig nificant, independent effects of pseudoephedrine were seen on any of the se ven psychometric test scores (p>0.05), although the drug tended to increase anxiety scores (p=0.092). Depth resulted in a significant increase in anxi ety scores (p=0.021) and a significant decrease in verbal fluency test scor es (p=0.041); it had no significant effects on the other five psychometric tests (p>0.05). Pseudoephedrine caused a significant increase (p=0.036) in mean heart rate, and depth caused a significant decrease (p=0.013). Neither pseudoephedrine nor depth affected cardiac rhythm. Conclusion. Pseudoephedrine does not cause significant alterations in psych ometric performance at 3 atm of pressure that might increase the risk of di ving. Depth causes significant adverse effects on anxiety levels and semant ic memory at 3 atm. Pseudoephedrine and depth have significant but opposite effects on heart rate; although, these effects are unlikely to be clinical ly significant during diving. It is unlikely that pseudoephedrine adds sign ificant risk to the diver.