Forced oscillation technique: a novel method to monitor sarcoidosis

Sarcoidosis is usually present in lungs and lymph nodes. The severity of
pulmonary sarcoidosis ranges from unexpectedly found radiographic
irregularities in patients showing no symptoms to a persistent, advancing
condition that is refractory to treatment. After diagnosis, longitudinal
surveillance is recommended. Surveillance should be most intensive during the
first 2 years after presentation to determine prognosis and the need for
therapy. Initial follow-up every 6 months is considered accurate, but more
frequent evaluations at every 3-6 months are recommended for patients with
pulmonary sarcoidosis scadding stages II-IV. In addition, all patients should
be monitored for at least 3 years after discontinuation of treatment.
Monitoring is performed with clinical evaluation, chest radiography and
pulmonary function tests. Decrease in forced vital capacity (FVC) assessed by
spirometry is the simplest and most accurate marker reflecting the stage of
pulmonary sarcoidosis. In addition, a reduced diffusing capacity for carbon
monoxide (DLCO) reflects the dilated alveolar-arterial gradient during
exercise. These methods are time-consuming, require experienced lung-function
technicians and patients that are able to follow-up their instructions for
forced breathing.

Forced oscillation technique (FOT) is a promising new method providing
information about lung mechanics during spontaneous breathing. Pulmonary
sarcoidosis is associated with reduced pulmonary compliance and airway
obstruction. Compared to conventional pulmonary function tests, the FOT has
some clear advantages: no age restrictions, spontaneous breathing of only 20
seconds, less cooperation required, less influence of instructions, more
sensitive in early stages of small airways disease and can detect changes in
the airways when spirometry is still normal. FOT may be particularly useful in
identifying restrictive, obstructive, or mixed lung function defects. FOT has
gained increasing interest since recent updates of technical standards and
improved devices. Studies of FOT in patients with sarcoidosis are scarce and
suggest an advantage of FOT compared to conventional pulmonary function tests.
However, no follow-up data are available that would support accurate monitoring
of the course of sarcoidosis. Therefore, we will investigate the use of FOT in
patients with pulmonary sarcoidosis during follow-up to determine its accuracy
for monitoring disease progression and therapy effects.

1. Determine the value of FOT for sarcoidosis evolution and response to therapy.
2. Evaluate patients* experience with FOT.

The research will be a prospective cohort study, conducted at the ILD Centre of
Excellence of the St. Antonius Hospital in Nieuwegein. The subject visits the
hospital as planned according to regular care. Interested patients with
sarcoidosis, who visit the hospital for at least one lung function test or an
HRCT-scan, will be screened and approached for participation in this study. In
addition to their regular tests, they will perform a FOT measurement. These
ameasurements are taken repeatedly during hospital visits for desease
progression monitoring. Patients participating in this study will be followed
until the end of this study, for up to 3 years.

The burden and risk of the research is considered negligible.