Page 128 - Livre électronique des RFTP 2025

P73. CAN TI/TTOT AND VT/TTOT PREDICT FUNCTIONAL

IMPAIRMENT IN ILD?

CHAIMA BRIKI¹⁻², KHOULOUD KCHAOU¹⁻², NOUR BEN MRAD¹, YOSSRA ABDELHEDI¹,
SOUMAYA KHALDI¹⁻², SALOUA BEN KHAMSA JAMELEDDINE¹⁻²

¹ DEPARTMENT OF PHYSIOLOGY AND FUNCTIONAL EXPLORATIONS, ABDERRAHMENE MAMI
HOSPITAL, ARIANA
² LABORATORY OF PHYSIOLOGY, NUTRITION, AND BIOMOLECULES (LR-17-ES-03), BIOTECHNOLOGY
CENTER OF SIDI THABET, UNIVERSITY OF MANOUBA, TUNIS

Introduction : In Interstitial Lung Diseases (ILD), restrictive ventilatory patterns and

altered respiratory mechanics often lead to reduced exercise tolerance. However,
simple resting ventilatory indices such as the inspiratory duty cycle (Ti/Ttot) and
ventilatory drive (VT/Ttot) are not routinely used to predict exercise limitation.

Aim : We aimed to assess the association between these resting ratios and six-
minute walk test (6MWT) performance in ILD patients.

Methods : We conducted a retrospective study including patients with ILD.
Pulmonary function was assessed at rest using whole-body plethysmography,
including measurements of FEV₁, FVC, Slow Vital Capacity (SVC) and Total Lung
Capacity (TLC). Resting ventilatory parameters, specifically Inspiratory time / Total
respiratory cycle time (Ti/Ttot) and Tidal volume / Total respiratory cycle time
(VT/Ttot) were obtained from respiratory cycle recordings. Functional capacity was
evaluated using the 6MWT. Impaired exercise tolerance was defined as a walking
distance < 82% of the predicted value and/or exercise-induced oxygen
desaturation ≥ 5%.

Results : A total of 68 ILD patients were included. Mean age and BMI were
respectively 53.8 ± 10.9 years and 30.7 ± 6.4 kg/m ². The most common diagnoses
were sarcoidosis (55.9%) and idiopathic pulmonary fibrosis (29.4%). Impaired 6MWT
performance was observed in 39.7% of patients, and 26.5% experienced exercise-
induced desaturation. Spirometry showed a mean FEV₁ of 75.8 ± 17.5%, FVC of 75.6
± 17.1%, and TLC of 83.4 ± 21.6%. The mean resting VT/Ttot was 0.31 ± 0.13, while
Ti/Ttot averaged 0.45 ± 0.05. Patients with impaired 6MWT performance exhibited
a trend toward lower VT/Ttot values compared to those with preserved
performance (0.28 vs 0.33; p =0.05). No significant differences were found for Ti/Ttot
(p = 0.39). No significant correlations were observed between ventilatory indices and
desaturation. The ROC curve for VT/Ttot showed modest discriminative capacity

(AUC = 0.622, 95% CI: 0.49–0.75; p = 0.089) with good specificity (82.9%) but limited
sensitivity (33.3%) in predicting impaired 6MWT performance.

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