Table 4.
Study measures and outcomes.
| Study Measures | ||||
|---|---|---|---|---|
| Study Reference | Objective Measures | Subjective Measures | Custom Measures | Primary Findings |
| Bonn et al. [61] | Panic attack frequency, resting breathing rate | NA | Phobia and agoraphobia scores, somatic symptoms | Significant improvement in all measures compared with control, maintained at 6-month follow-up |
| Conrad et al. [53] | Skin conductance, pCO2, tidal volume, HR | ASI, BAI, BDI, PSS, PSWQ | Mood questionnaire | No change in respiratory or autonomic measures in direction of relaxation, except for attention to breathing |
| de Ruiter et al. [64] | pCO2, RR | FBSQ, FSS-III, SCL-90 | Phobic anxiety and avoidance scales, panic attack diary | Significant improvement in all measures, except panic frequency, with reduction in RR; no significant differences between groups |
| Gorman et al. [54] | pCO2 | API, RPE, SADS-LA | Anxiety and apprehension scales | Significant sensitivity to anxiogenic effects of CO2 compared with controls; 7% CO2 discriminated best. CO2 is a more potent anxiogenic stimulus than room-air hyperventilation. |
| Herhaus et al. [67] | HR, BMP, EEG signals | ACQ, ASI, BDI, BSQ, MI, PAS | NA | Improved HRV and panic symptoms compared with controls |
| Hibbert and Chan [62] | NA | BDI, FQ, HARS | Panic attack and exposure diary | Significant improvement in anxiety measures compared with controls; no significant differences in hyperventilators compared with non-hyperventilators |
| Ito et al. [63] | NA | ACQ, BDI, BSQ, FQ, HARS, PT, disability (measure not defined) | Panic attack diary | Significant improvement in all measures at post-treatment and follow-up; no significant differences between groups, but a slightly greater number of patients in the treatment group showed improvement in phobic avoidance and fear |
| Kim et al. [55] | pCO2, RR | ACQ, ACQ, ASI, BAI, BDI, MIA, PDSS | NA | Significant improvement in panic severity by using both breathing training methods, maintained at 6-month follow-up; patients learned to alter pCO2 and RR via therapy |
| Meuret et al. [56] | pCO2, RR | BSQ, ASI, BSQ/ASI, ACQ, PDSS, CEQ | NA | Significant improvement in panic symptoms, panic-related cognitions, and perceived control in both treatment groups; corrections from hypocapnic to normocapnic levels only in capnometry-assisted respiratory training group |
| Meuret et al. [57] | pCO2, RR | PDSS, clinician-rated PD severity, CGI, ASI, SDS, MI-AAL, BDI | NA | Significant improvement in all measures in treated but not untreated patients; psychological outcomes maintained at 2- and 12-month follow-up |
| Wollburg et al. [58] | Expired CO2, end-tidal pCO2, RR, respiratory rate instability, TV, TV instability, HR, skin conductance | ASI, MI, BDI, ASQ | PDSS, ASI, mobility inventory for agoraphobia, BDI, anxiety symptom checklist, pCO2, expired CO2, RR, RR instability, tidal volume, TV instability, HR, respiratory sinus arrhythmia, skin conductance | Before treatment: higher respiration rates, tidal volume instability and sighing at rest of panic patients compared with non-anxious controls. After lowering pCO2 therapy: lower pCO2 during testing of panic patients but no significant differences in reactivity, recovery, or treatment effect between groups; baseline abnormalities somewhat specific to PD |
| Yamada et al. [68] | VC, %VC | Diaphragmatic breathing assessment | NA | %VC was significantly reduced in patients with impaired diaphragmatic breathing, which was equally recoverable compared with controls, with breathing retraining |
| Doria et al. [65] | NA | HRSA, HRSD, SCL-90, ZSAS, ZSDS | NA | Significant improvement in anxiety and depression |
| Han et al. [66] | pCO2, inspiratory time, inspiratory volume, expiratory time, expiratory volume | NQ, STAI, ZBV-DY1, ZBV-DY2 | NA | Significantly improved daily life complaints and state anxiety; markedly changed breathing pattern |
| Meuret et al. [59] | pCO2, RR | PDSS, ASI, STAIT-T, BDI | Rate average anxiety, depression, anticipation, and worry daily; panic attack diary | Significant improvement in PD symptoms and pCO2 that continued through follow-up; equal reductions in fear, anxiety and depression |
| Tolin et al. [60] | pCO2, RR | PDSS, NINI, CGI-S, SDS, MI-AAL, ASI, BDI, panic frequency | Patient satisfaction | Significant improvement in PD severity, with high treatment response and remission maintained at 12-month follow-up. Decrease in functional impairment and global illness severity. |
ACQ = Agoraphobic Cognitions Questionnaire; API= Acute Panic Inventory; ASI = Anxiety Sensitivity Index; ASQ = Attributional Style Questionnaire; BAI = Beck Anxiety Inventory; BDI = Beck Depression Inventory; BSQ = Body Sensations Questionnaire; CEQ = Credibility/Expectancy Questionnaire; CGI = Clinician Global Impression; CGI-S = Clinician Global Impression-Severity; FBSQ = Fear of Bodily Sensations Questionnaire; FQ = Fear Questionnaire; FSS-III = Fear Surrey Schedule-III; HARS = Hamilton Anxiety Rating Scale; HR = heart rate; HRS-A = Hamilton Rating Scale for Anxiety; HRS-D = Hamilton Rating Scale for Depression; HRV = heart rate variability; MI = Mobility Inventory; MIA = Mobility Inventory for Agoraphobia; MI-AAL = Mobility Inventory for Agoraphobia; MINl = Mini International Diagnostic Interview; NQ = Nijmegen Questionnaire; PAS = Panic and Agoraphobia Scale; pC02 = carbon dioxide pressure; PD = panic disorder; PDSS = Panic Disorder Severity Scale; PSS = Perceived Stress Scale; PSWQ = Penn State Worry Questionnaire; PT = Phobic Target; RPE = Rating of Perceived Exertion; RR = respiratory rate; SADS-LA = Lifetime Version Modified for the Study of Anxiety Disorders; SCL-90 = Symptom CheckIist-90; SDS = Sheehan Disability Scale; STAI = State-Trait Anxiety Inventory; STAI-T = State-Trait Anxiety Inventory–Trait subscale; ZSAS = Zung Self-Rating Anxiety Scale; ZSDS = Zung Self-Rating Depression Scale; ZBV DYl, ZBV-DY2 = state and trait versions of the Zelfbeoordelingsvragenlijst.