Smoking, physical activity and respiratory irregularities in patients with panic disorder.

Background. In the past decades different evidences suggested a relationship between panic disorder (PD) and respiration, among which the presence of different respiratory irregularities at rest in PD patients. It has been hypothesized that PD could be characterized by a dysfunction of those areas involved in the central control of respiration. The aim of the present study was to elucidate possible differences in breath-by-breath respiratory function at rest between a sample of PD patients with agoraphobia and healthy controls (HC), with particular attention to smoking and physical activity as possible relevant factors in the understanding of respiratory dynamics in PD. Methods. Respiratory physiology was assessed in 32 PD patients and 24 HC. Respiratory rate (RR), tidal volume (VT), minute ventilation (VE), and end-tidal CO2 (pCO2) have been assessed. Results.A significant diagnosis-by-smoking interaction was found for mean RR and VT. Mean pCO2 was significantly higher in active than in sedentary patients. Anxiety state did not account for the results. Conclusions. Our findings suggest an abnormal regulation of the respiratory system as a key mechanism in PD. In future studies it should be useful to stratify data taking into account level and intensity of physical activity and smoking behaviour, as well as to consider the cardiac profile and the effect of those variables able to modulate the homeostatic brain functioning.