Are Respiratory Abnormalities Specific for Panic Disorder? A Meta-Analysis

Objectives:There is evidence of baseline respiratory abnormalities in panic disorder (PD), but whether they are specific to PD remains unclear. To investigate this issue, we meta-analyzed results from studies comparing baseline respiratory and hematic variables between subjects with PD and subjects with other anxiety disorders. Methods: A literature search in bibliographic databases was performed. Fixed-effects models were applied. Several moderator analyses and publication bias diagnostics were performed. Results: We found: (1) significantly lower mean end-tidal partial pressure of CO2 (et-pCO(2)) in subjects with PD than in those with social phobia (SP) or generalized anxiety disorder (GAD), and (2) higher mean respiratory rate, lower venous et-pCO(2) and HCO3- concentration in subjects with PD than in those with SP. No publication bias was found. Conclusions: Subjects with PD show a condition of baseline hyperventilation when compared to subjects with SP or GAD. Hematic variables suggest that the hyperventilation may be chronic. These results support the idea that baseline respiratory abnormalities are specific to PD pathophysiology. Further studies are needed to clarify whether these abnormalities are related to a malfunction of the respiratory system or to specific cognitive/emotional/behavioral factors in this population.