Why the study?
Do patients with panic disorder exhibit respiratory pattern abnormalities in daily life compared to healthy controls?
Do patients with panic disorder exhibit respiratory pattern abnormalities in daily life compared to healthy controls?
Ambulatory monitoring reveals no evidence of stable respiratory pattern abnormalities in patients with panic disorder during daily life, challenging laboratory-based respiratory theories of the disorder.
Ambulatory monitoring shows no respiratory differences in panic disorder; leaves open whether laboratory findings reflect situational factors rather than stable traits.
Objective: To assess the external validity of laboratory baselines in panic disorder (PD), frequently associated with respiratory pattern abnormalities like increased respiratory variability and sighing, implying a stable pathophysiologic trait characteristic. Methods: Physical activity and a variety of breath-by-breath volumetric, timing, and variability measures of respiration were recorded in the daily life of 26 patients with PD and 26 healthy controls (HC), using a novel ambulatory monitoring system optimized for reliable assessment of respiratory pattern. Data were stratified for physical activity to eliminate its confounding effects. Results: Groups showed strong and consistent diurnal patterns in almost all respiratory variables. However, patients with PD did not differ from HC regarding any of the respiratory timing, volumetric and variability measures, with negligible group effect sizes for all measures. Patients with fewer self-reported respiratory symptoms of anxiety exhibited more pronounced rapid shallow breathing as well as diminished total breath time and its variability. Conclusions: Despite state-of-the-art ambulatory assessment and sufficient statistical power to detect respiratory alterations previously observed in the laboratory, we found no evidence for such alterations in PD patients’ daily life. Neither the total PD group nor patients with particularly pronounced respiratory symptomatology displayed increased respiratory variability. These results caution against interpreting results from laboratory baselines in PD as reflecting a stable trait characteristic. Rather, they likely represent a state-trait interaction due to enhanced reactivity of PD patients to novel environments. These results challenge aspects of respiratory theories of PD that were based on laboratory findings. AccM = accelerometry (motion); ASI = Anxiety Sensitivity Index; BDI = Beck Depression Inventory; f/Vt = rapid shallow breathing index; HC = healthy controls; MI = Mobility Inventory; PD = panic disorder; PDSS = Panic Disorder Severity Scale; RMSSD = root mean squared successive differences; RSQ = Respiratory Symptoms Questionnaire; Sigh% = total number of sighs/total number of breaths; STAI = State-Trait Anxiety Inventory; Ti/Tt = inspiratory breath time/total breath time ratio; Tt = total breath time; Vm = minute ventilation; Vt = tidal volume; Vt/Ti = mean inspiratory flow.
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Pfaltz et al. (2009) studied this question.