CLE and OCT in acute respiratory insufficiency

Acute respiratory distress syndrome is a severe complication of critical
illness. The diagnosis of ARDS is difficult, and it could be important to
differentiate ARDS from other causes of acute respiratory failure.
Histopathology would help treatment decisions but is not available, due to
morbidity and mortality risks. Innovative probe-based imaging techniques such
as *Confocal Laser Endomicroscopy* (CLE) and *Optical Coherence
Tomography* (OCT) are high-resolution optical techniques that, combined with
conventional bronchoscopy, have been found to provide minimal-invasive,
real-time, near-histology information about the alveolar compartment in
non-ventilated non-critically ill patients.

To identify the characteristics on pCLE and OCT images of the alveolar
compartment in mechanically ventilated critically ill patients with
non-resolving acute respiratory failure.

This is an investigator-initiated observational in-vivo study, with an
explorative character. We will enroll a maximum of 20 patients with
non-resolving acute respiratory failure mandating a bronchoscopy (the
researchers decide which patient is eligible, based on the heterogeneity of the
disease and the suspected etiology). One patient can be imaged several times,
on condition there is an indication for bronchoscopy.
Patients will receive additional optical pCLE and pOCT measurements of the
alveolar compartment with a total estimated time for research measurements of
5-10 minutes.

Patients in this study will not benefit from participation. There is little to
no burden related to study participation. During a standard diagnostic
bronchoscopy with broncho-alveolar lavage, optical pCLE and OCT measurements
with the use of a light beam will be performed by holding the probe in
perpendicular contact with the tissue, a procedure that will last approximately
5-10 minutes. Obviously, OCT and CLE measurements will only be obtained in the
absence of mechanical ventilation problems during bronchoscopy. Patients will
not notice this as they are sedated. Adverse events are not expected based on
our own OCT and CLE experience in interstitial lung disease (ILD) patients
(Clinicaltrial.gov identifier NCT02689102, AMC protocol nr NL54612.018.15),
which is in concordance with the literature, where bronchoscopy combined with
probe-based optical techniques in non-ventilated patients was reported to be
safe, easy to perform and little time-consuming, without adverse events. In
conclusion, in our opinion the burden and risks associated with the additional
probe based optical technique measurements are neglectable.