Advanced lung ultrasound to differentiate pneumonia and atelectasis in ICU patient

The study will be a prospective, observational cohort study, conducted on the ICU of the Amsterdam UMC, Vrije Universiteit Amsterdam, a tertiary academic hospital in Amsterdam, the Netherlands. Patients will followed–up until discharge. The protocol was approved by the local ethics board as part of other ongoing studies and informed consent will be obtained by patients or their next of kin. STROBE-Guidelines (STrengthening the Reporting of OBservational studies in Epidemiology) will be followed.

Study population
The study population will consist of adult (>18 years) patients, admitted to the ICU, with any type of consolidation seen on chest X-ray (CXR). Patient with ARDS, trauma with pulmonary contusion and in contact isolation will be excluded. Sex, age, reason for ICU admission, SOFA score (Sequential Organ Failure Assessment) on the day of measurement, use of mechanical ventilation and inflammatory markers will be recorded on the same day of ultrasound assessment. Gram stain colouring and bacterial culture results will be recorded when made available in the electronic patient dossier.

Ultrasound Measurements:
All images will be made by an independent researcher, with a Philips CX50 ultrasound. All measurements will be performed following the BLUE-protocol, with additional measurements in the PLAPS point (see below). Image acquisition will take place directly after performance of the CXR, with a maximum duration of 24 hours between CXR and ultrasonographic examination. Evaluation of the images will take place directly after acquisition. Researchers making the images and measurements will blinded to the clinical status of the patient, and will only be allowed to view the chest X-ray.

Flow:
Pulmonary vascular flow will be assessed with color doppler. In order to maximize the sensitivity for low-velocity flow, the velocity scale will be set to 0.25m/sec. To avoid interference with adjacent structures, the window of assessment will be minimalized. Flow will be deemed present if homogeneously distributed tree-like, tortuous or fragmented vascular structures with blood flow in the lumen is seen through several respiratory cycles. In the case that flow is only seen in one part of the consolidation or only on one of the two PLAPS points, it is still denoted as being present.

Bronchogram:
Bronchograms will be assessed in B-mode with ultrasound settings to the preference of the researcher. They are defined as small punctiform or linear hyperechoic artefacts within the consolidated tissue. In case motion is visible in concordance with the patient’s respiratory cycle it will be deemed dynamic.

Advanced lung utltrasound, c.q. color doppler imaging and dynamic air bronchograms can aid in differentiating pneumonia from atelectasis

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