Cardiovascular and subjective responses to inhalation of carbon dioxide. A controlled test with anxious patients.

Cardiovascular and subjective responses to inhalation of a 35% CO2 mixture were studied in a sample of anxious neurotics. Inhalation of air was used as a placebo control treatment. In comparison with the inhalation of air, CO2 produced a significant drop in diastolic blood pressure. A drop in heart rate frequency was observed both after inhalation of CO2 and air. CO2 inhalation did not produce an average decline in subjective feelings of distress. Explanations of these data are offered and they are compared with earlier findings. Some speculations are made on the clinical usefulness of CO2 inhalation in the treatment of anxious neurotics.