Nitrous Oxide in Prehospital Care

To the Editor.— The report by Thal et al (1979;242:2418) concerning the use of nitrous oxide and oxygen mixtures in prehospital care and the comments by Richard N. Hindin, MD (1980;244: 769), raise questions that have been under study for some months at the University of Pittsburgh. The issue of environmental levels of nitrous oxide within ambulance compartments is the subject of a study now being carried out within the mobile intensive care units of the Pittsburgh Emergency Medical Services Department. Preliminary results would indicate that paramedical personnel, while attending patients breathing a self-administered gas mixture, are exposed to higher concentrations of nitrous oxide than have been documented in operating theaters. This exposure is of brief duration, however, and occurs infrequently during an average working day. In initial testing designed to evaluate performance of the ambulance crew, we have been unable to detect any change from control values. The results