Evaluation of diurnal variation in forced vital capacity in patients with fibrotic interstitial lung diseases using home spirometry

Fibrotic interstitial lung diseases (ILDs) are a group of lung diseases
affecting the interstitium of the lung. One of the most common ILDs is
idiopathic pulmonary fibrosis (IPF).IPF is a chronic progressive disease with
often a poor quality of life and a declining lung function. Recently two
anti-fibrotic drugs became available that slow down the decline of lung
function, measured with the forced vital capacity (FVC) as most important
outcome measure. Unfortunately, FVC measurements have an inherent variability
and disease course is often unpredictable. The standard practice of FVC
measurement once per three months is not enough to reliably assess changes in
disease course in the individual patient.

Furthermore, from a clinical trial perspective, more refined techniques are
needed to measure FVC. In IPF, new drugs are being investigated on top of
*standard care* with anti-fibrotic medication, likely resulting in smaller
margins of change and need for lengthy trials and large numbers of patients,
which are not only very expensive but also hardly feasible in a rare disease as
IPF.

We performed a pilot study using home spirometry in this patient group in the
Erasmus MC. Four patients performed home spirometry twice daily (morning and
afternoon) on their own initiative. Surprisingly, all patients had a higher FVC
in the morning compared to the afternoon. However, these are preliminary
results in a small group of patients, which should be evaluated in a larger
observational study to assess whether the diurnal variations we deteceted are
realistic and clinically relevant. If so, this will have consequences for
future clinical trials and daily practice. Further appointments for pulmonary
function should be planned on approximately the same time if there is indeed a
diurnal variation in FVC. Furthermore, more insights are needed to assess
differences in the change in pulmonary function between fibrotic interstitial
lung diseases.

The aim of this study is to evaluate the diurnal variation in pulmonary
function in patients with fibrotic interstitial lung diseases, including IPF.
Differences in morning and evening FVC will be assessed with twice daily home
spirometry. Furthermore, we aim to assess difference in change in FVC over a 12
week period between different fibrotic interstitial lung diseases.

This is a prospective, single-centre, non-randomized observational study in the
Erasmus Medical Center, Rotterdam.

There will be no risks associated with this study and the burden is small.
Patients will be asked to perform twice daily spirometry for the first six
weeks, once daily spirometry for the last six weeks, wear an activity tracker,
fill in weekly symptom scores, and complete the K-BILD questionnaire at
baseline, after six weeks and after 12 weeks. Participants may directly benefit
from this study, because they can have more insights in there disease course by
keeping track of their pulmonary function.