Defining hyperinflation as 'dynamic': moving toward the slope

Impact of bronchoscopic lung volume reduction with endobronchial valves on dynamic hyperinflation: Results from the PIERCE study

BACKGROUND AND OBJECTIVE

Dynamic hyperinflation (DH) is a major marker of exertional dyspnoea in severe emphysema. We hypothesized that bronchoscopic lung volume reduction (BLVR) using endobronchial valves (EBVs) decreases DH.

METHODS

In this prospective bi-centre study from both Toulouse and Limoges Hospitals, we assessed DH during an incremental cycle ergometry before and 3 months after EBVs treatment. The primary objective was to observe the change in inspiratory capacity (IC) at isotime. Target lobe volume reduction (TLVR) and changes in residual volume (RV), forced expiratory volume in one-second (FEV₁ ), mMRC, 6 minutes walking distance (6MWD), BODE and other dynamic measures like tele-expiratory volume (EELV) were also analysed.

RESULTS

Thirty-nine patients were included, of whom thirty-eight presented DH. IC and EELV at isotime significantly improved (+214 mL, p = 0.004; -713 mL, p ˂ 0.001, respectively). Mean changes were +177 mL for FEV₁ (+19%, p < 0.001), -600 mL for RV (p < 0.0001), +33 m for 6MWD (p < 0.0001), respectively. Patients who responded on RV (>430 mL decrease) and FEV₁ (>12% gain) had better improvements compared to non-responders (+368 mL vs. +2 mL; +398 mL vs. -40 mL IC isotime, respectively). On the opposite, in patients who responded on DH (>200 mL IC isotime increase), changes in TLV (-1216 mL vs. -576 mL), FEV₁ (+261 mL vs. +101 mL), FVC (+496 mL vs. +128 mL) and RV (-805 mL vs. -418 mL) were greater compared to non-responders.

CONCLUSIONS

DH decreases after EBVs treatment, and this improvement is correlated with static changes.

Flow limitation and dysanapsis in children and adolescents with exertional dyspnea

The consequence of dysanapsis, quantitated by dysanapsis ratio (DR), on expiratory flow limitation (EFL) during exercise in pediatric subjects was examined. EFL occurred in 80 (56%) subjects from an enriched sample of children and adolescents tested during investigation of exertional dyspnea. DR was lower in subjects with vs without EFL during exercise: (0.055 ± 0.015 vs 0.067 ± 0.017, p < 0.001), and lower ratio correlated with greater extent of EFL (r = -0.64, p < 0.001). EFL was seen more often in boys: 67% vs 46% (p = 0.01), as girls had higher DR (0.063 ± 0.016 vs 0.056 ± 0.018, p = 0.007). Lower FEV₁ (95 ± 17 vs 102 ± 15%predicted, p < 0.005) and FEF₅₀ (3.47 ± 1.28 vs 4.08 ± 1.20 L s^-1, p = 0.002) distinguished those with vs without EFL. Inspiratory capacity rose (IC) steadily, as work increased among those with EFL, whereas it fell to back resting levels after an initial rise in subjects without EFL. Low DR predicts EFL in pediatric subjects. Adjusting operating lung volume during exercise can mitigate EFL but this strategy may contribute to exertional dyspnea.

Effects of inspiratory muscle training on dyspnoea in severe COPD patients during pulmonary rehabilitation: controlled randomised trial

The benefit of inspiratory muscle training (IMT) combined with a pulmonary rehabilitation programme (PRP) is uncertain. We aimed to demonstrate that, in severe and very severe chronic obstructive pulmonary disease (COPD) patients, IMT performed during a PRP is associated with an improvement of dyspnoea.In a single-blind randomised controlled trial, 150 severe or very severe COPD patients were allocated to follow PRP+IMT versus PRP alone. The evaluations were performed at inclusion and after 4 weeks. The primary outcome was the change in dyspnoea using the Multidimensional Dyspnoea Profile questionnaire at the end of a 6-min walk test (6MWT) at 4 weeks. Secondary outcomes were changes in dyspnoea using the Borg (end of the 6MWT) and modified Medical Research Council scales and in functional parameters (maximal inspiratory pressure (P_Imax), inspiratory capacity, 6MWT and quality of life). All analyses were performed on an intention-to-treat basis.Dyspnoea decreased significantly in both groups; however, the improvement of dyspnoea was not statistically different between the two groups. We only found a statistically significant greater increase of P_Imax after IMT+PRP than after PRP alone.In this trial including severe or very severe COPD patients, we did not find a significant benefit of IMT during PRP+IMT as compared to PRP alone on dyspnoea, despite a significantly higher improvement of P_Imax in the IMT group.

The effects of dynamic hyperinflation on CT emphysema measurements in patients with COPD

OBJECTIVES

Dynamic hyperinflation (DH) significantly affects dyspnea and intolerance to exercise in patients with chronic obstructive pulmonary disease (COPD). Quantitative computed tomography (QCT) of the chest is the modality of choice for quantification of the extent of anatomical lung damage in patients with COPD. The purpose of this article is to assess the effects of DH on QCT measurements.

METHODS

The study sample comprised patients with Global initiative for Chronic Obstructive Lung Disease (GOLD) stages III and IV COPD referred for chest CT. We examined differences in total lung volume (TLV), emphysema volume (EV), and emphysema index (EI) determined by QCT before and after DH induction by metronome-paced tachypnea (MPT). Initial (resting) and post-MPT CT examinations were performed with the same parameters.

RESULTS

Images from 66 CT scans (33 patients) were evaluated. EV and EI, but not TLV, increased significantly (p<0.0001) after DH induction.

CONCLUSION

QCT showed significant increases in EV and EI after MPT-induced DH in patients with GOLD stages III and IV COPD. For longitudinal assessment of patients with COPD using QCT, we recommend the application of a pre-examination rest period, as DH could mimic disease progression. QCT studies of the effects of DH-preventive therapy before exercise could expand our knowledge of effective measures to delay DH-related progression of COPD.

Lung hyperinflation in chronic obstructive pulmonary disease: mechanisms, clinical implications and treatment

Lung hyperinflation is highly prevalent in patients with chronic obstructive pulmonary disease and occurs across the continuum of the disease. A growing body of evidence suggests that lung hyperinflation contributes to dyspnea and activity limitation in chronic obstructive pulmonary disease and is an important independent risk factor for mortality. In this review, we will summarize the recent literature on pathogenesis and clinical implications of lung hyperinflation. We will outline the contribution of lung hyperinflation to exercise limitation and discuss its impact on symptoms and physical activity. Finally, we will examine the physiological rationale and efficacy of selected pharmacological and non-pharmacological 'lung deflating' interventions aimed at improving symptoms and physical functioning.

Pathogenesis of hyperinflation in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a preventable and treatable lung disease characterized by airflow limitation that is not fully reversible. In a significant proportion of patients with COPD, reduced lung elastic recoil combined with expiratory flow limitation leads to lung hyperinflation during the course of the disease. Development of hyperinflation during the course of COPD is insidious. Dynamic hyperinflation is highly prevalent in the advanced stages of COPD, and new evidence suggests that it also occurs in many patients with mild disease, independently of the presence of resting hyperinflation. Hyperinflation is clinically relevant for patients with COPD mainly because it contributes to dyspnea, exercise intolerance, skeletal muscle limitations, morbidity, and reduced physical activity levels associated with the disease. Various pharmacological and nonpharmacological interventions have been shown to reduce hyperinflation and delay the onset of ventilatory limitation in patients with COPD. The aim of this review is to address the more recent literature regarding the pathogenesis, assessment, and management of both static and dynamic lung hyperinflation in patients with COPD. We also address the influence of biological sex and obesity and new developments in our understanding of hyperinflation in patients with mild COPD and its evolution during progression of the disease.