The Panic Disorder Respiratory Ratio: A Dimensional Approach to the Respiratory Subtype

ObjectiveThe respiratory ratio is a dimensional construct of the respiratory subtype of panic disorder (PD). The respiratory subtype has been correlated with an increased sensitivity to CO2 inhalation, positive family history of PD and low comorbidity with depression. The objective of our study was to determine whether the respiratory ratio is correlated with CO2-induced panic attacks and other clinical and demographic features.MethodsWe examined 91 patients with PD and submitted them to a double-breath 35% CO2 challenge test. The respiratory ratio was calculated based on the Diagnostic Symptom Questionnaire (DSQ) scores recorded in a diary in the days preceding the CO2 challenge. The scores of the respiratory symptoms were summed and divided by the total DSQ score.ResultsThe respiratory ratio was correlated with CO2 sensitivity, and there was a non-statistically significant trend towards a correlation with a family history of PD.ConclusionsThe positive correlation between the respiratory ratio and the anxiety elicited by the CO2 inhalation indicates that the intensity of respiratory symptoms may be proportional to the sensitivity to carbon dioxide.