Carbon dioxide provocation of anxiety and respiratory response in bipolar disorder

BackgroundFrequent bipolar/panic comorbidity implies bipolar individuals may experience CO2-provoked anxiety and changes in respiratory patterns similar to those experienced by individuals with panic disorder.Methods16 euthymic bipolar individuals breathed air and air combined with 5% CO2 for 15 min each. Respiratory and subjective anxiety measures were collected.ResultsOn CO2 subjects were more anxious and breathed more deeply and rapidly than with air; the degree of increase in anxiety attributable to CO2 was directly correlated with the degree of increase in minute ventilation. Five individuals were assessed as having a panic attack. Panic response to CO2 was predicted by the degree of anxiety experienced with air alone.ConclusionsComparison with the results of similar panic studies shows bipolar disorder is associated with enhanced respiratory response to CO2. Hypersensitivity to CO2 among bipolar individuals suggests a possible pathological mechanism common to both bipolar and panic disorders. These preliminary data support the expanded application of CO2 challenges in bipolar subjects.