Mechanisms of exercise limitation in patients with chronic hypersensitivity pneumonitis

Abstract

Small airway and interstitial pulmonary involvements are prominent in chronic hypersensitivity pneumonitis (cHP). However, their roles on exercise limitation and the relationship with functional lung tests have not been studied in detail.Our aim was to evaluate exercise performance and its determinants in cHP. We evaluated maximal cardiopulmonary exercise testing performance in 28 cHP patients (forced vital capacity 57±17% pred) and 18 healthy controls during cycling.Patients had reduced exercise performance with lower peak oxygen production (16.6 (12.3–19.98) mL·kg−1·min−1 versus 25.1 (16.9–32.0), p=0.003), diminished breathing reserve (% maximal voluntary ventilation) (12 (6.4–34.8)% versus 41 (32.7–50.8)%, p<0.001) and hyperventilation (minute ventilation/carbon dioxide production slope 37±5 versus 31±4, p<0.001). All patients presented oxygen desaturation and augmented Borg dyspnoea scores (8 (5–10) versus 4 (1–7), p=0.004). The prevalence of dynamic hyperinflation was found in only 18% of patients. When comparing cHP patients with normal and low peak oxygen production (<84% pred, lower limit of normal), the latter exhibited a higher minute ventilation/carbon dioxide production slope (39±5.0 versus 34±3.6, p=0.004), lower tidal volume (0.84 (0.78–0.90) L versus 1.15 (0.97–1.67) L, p=0.002), and poorer physical functioning score on the Short form-36 health survey. Receiver operating characteristic curve analysis showed that reduced lung volumes (forced vital capacity %, total lung capacity % and diffusing capacity of the lung for carbon dioxide %) were high predictors of poor exercise capacity.Reduced exercise capacity was prevalent in patients because of ventilatory limitation and not due to dynamic hyperinflation. Reduced lung volumes were reliable predictors of lower performance during exercise.

The impact of high-flow nasal cannula oxygen therapy on exercise capacity in fibrotic interstitial lung disease: a proof-of-concept randomized controlled crossover trial

“…Recent clinical studies have demonstrated the similarities in genetics, pathophysiology, and clinical course between IPF and non-IPF-FILD [34][35][36]. Additionally, previous reports showed a reduced exercise capacity in patients with non-IPF-FILD, similar to that in patients with IPF [37,38]. Considering these findings, we recruited patients with all forms of FILD.…”

Cardiopulmonary exercise testing in interstitial lung diseases and the value of ventilatory efficiency

“…Dynamic hyperinflation (DH), i.e. a decrease in inspiratory capacity during exercise, was documented in ILDs involving airways, such as LAM, PLCH and HP [72][73][74][75]. Since DH has been demonstrated in patients with pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension [76,77], it could theoretically be present in patients with ILD and associated PH, but this issue has not yet been investigated.…”

Evaluation of Dynamic Respiratory Mechanical Abnormalities During Conventional CPET

“…As a result, critical reduction in IRV manifests early during exercise, and V T is positioned close to the reduced TLC and upper extreme of the contracted pressure–volume curve ( Figure 2C ). In ILD patients with airway involvement, V T expansion may additionally be restricted due to EFL and an increase in EELV ( 44 , 45 ). Importantly, in these examples, the classically observed rapid shallow breathing pattern ( Figures 1C,D ) is a response to the reduced compliance of the respiratory system resulting from restriction of IC and IRV ( Figures 1A,B ).…”