Panic disorder and the respiratory system: clinical subtype and challenge tests.
BACKGROUND
Respiratory changes are associated with anxiety disorders, particularly panic disorder (PD). The stimulation of respiration in PD patients during panic attacks is well documented in the literature, and a number of abnormalities in respiration, such as enhanced CO2 sensitivity, have been detected in PD patients. Investigators hypothesized that there is a fundamental abnormality in the physiological mechanisms that control breathing in PD.


METHODS
The authors searched for articles regarding the connection between the respiratory system and PD, more specifically papers on respiratory challenges, respiratory subtype, and current mechanistic concepts.


CONCLUSIONS
Recent evidences support the presence of subclinical changes in respiration and other functions related to body homeostasis in PD patients. The fear network, comprising the hippocampus, medial prefrontal cortex, amygdala and its brainstem projections, may be abnormally sensitive in PD patients, and respiratory stimulants like CO2 may trigger panic attacks. Studies indicate that PD patients with dominant respiratory symptoms are particularly sensitive to respiratory tests compared to those who do not manifest dominant respiratory symptoms, representing a distinct subtype. The evidence of changes in several neurochemical systems might be the expression of the complex interaction among brain circuits.
Laboratory of Panic and Respiration, National Institute for Translational Medicine Institute of Psychiatry, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil. rafaelcrfreire@gmail.com
Rafael C
RC
Freire
Antonio E
AE
Nardi
D002245:Carbon Dioxide / Q000009:adverse effects / Q000502:physiology; D006801:Humans; D006985:Hyperventilation / Q000523:psychology; D016584:Panic Disorder / Q000503:physiopathology* / Q000523:psychology; D012120:Respiration Disorders / Q000503:physiopathology* / Q000523:psychology; D012129:Respiratory Function Tests
D002245:Carbon Dioxide