Lung Volume Reduction in Emphysema Improves Chest Wall Asynchrony

Abstract

Background: Lung volume reduction (LVR) techniques improve lung function in selected patients with emphysema, but the impact of LVR procedures on the asynchronous movement of different chest wall compartments, which is a feature of emphysema, is not known.

Methods: We used optoelectronic plethysmography to assess the effect of surgical and bronchoscopic LVR on chest wall asynchrony. Twenty-six patients were assessed before and 3 months after LVR (surgical [n = 9] or bronchoscopic [n = 7]) or a sham/unsuccessful bronchoscopic treatment (control subjects, n = 10). Chest wall volumes were divided into six compartments (left and right of each of pulmonary ribcage [Vrc,p], abdominal ribcage [Vrc,a], and abdomen [Vab]) and phase shift angles (θ) calculated for the asynchrony between Vrc,p and Vrc,a (θRC), and between Vrc,a and Vab (θDIA).

Results: Participants had an FEV₁ of 34.6 ± 18% predicted and a residual volume of 217.8 ± 46.0% predicted with significant chest wall asynchrony during quiet breathing at baseline (θRC, 31.3° ± 38.4°; and θDIA, -38.7° ± 36.3°). Between-group difference in the change in θRC and θDIA during quiet breathing following treatment was 44.3° (95% CI, -78 to -10.6; P = .003) and 34.5° (95% CI, 1.4 to 67.5; P = .007) toward 0° (representing perfect synchrony), respectively, favoring the LVR group. Changes in θRC and θDIA were statistically significant on the treated but not the untreated sides.

Conclusions: Successful LVR significantly reduces chest wall asynchrony in patients with emphysema.

Figure 1 –

Optoelectronic plethysmography. A, B, Infrared cameras. C, D, Marker positioning. E-G, Geometric model. 3D = three-dimensional; V_ab = abdominal compartment volume; V_cw = total chest wall volume; V_rc,a = abdominal ribcage volume; V_rc,p = pulmonary ribcage volume. (The patients provided written consent for the use of the photographs.)

Figure 2 –

A, B, Time courses of V_rc,p, V_rc,a, V_ab, and V_cw during a typical respiratory cycle during quiet breathing at rest in a representative patient before (A) and after (B) lung volume reduction surgery (LVRS). Black line represents the inspiratory portion of the respiratory cycle, and asynchronous movement of abdominal ribcage compartment (RC,a) before LVRS is clearly demonstrated, as is the improvement thereof after LVRS. Lissajou figures of the dynamic loops of ΔV_rc,p vs ΔV_rc,a (θRC) and ΔV_rc,a vs ΔV_ab (θDIA) during quiet breathing are used to calculate θ. m = line parallel to the x axis at 50% of one compartment’s tidal volume; s = the second compartment’s tidal volume. Phase shift is calculated as θ = sin⁻¹ (ms⁻¹). θDIA = phase shift angle between V_rc,p and V_rc,a; θRC = phase shift angle between V_rc,p and V_rc,a. See Figure 1 legend for expansion of other abbreviations.