Lung Ultrasound in High Altitude Lung Edema
Condition: Pulmonary Edema
MeSH terms: Pulmonary Edema; Edema
Study type: Observational

Summary: 
      High altitude pulmonary edema is a life-threatening condition that remains a concern for
      climbers and clinicians alike. It is defined as a non-cardiac pulmonary edema occurring at
      altitudes exceeding 3000m in non-acclimatised individuals. Recently, studies conducted in
      remote areas have demonstrated that ultrasound lung comets (B lines) can be used as a measure
      of sub-acute pulmonary edema and high altitude pulmonary edema in climbers ascending to
      altitude. the investigators want to assess the occurrence of of comet tails (B lines) as a
      measure of pulmonary edema among patients after lung transplantation and healthy individuals
      during an expedition to Mount Kilimanjaro.
    

Detailed description: 
      High altitude pulmonary edema is a life-threatening condition that remains a concern for
      climbers and clinicians alike. It is defined as a non-cardiac pulmonary edema occurring at
      altitudes exceeding 3000m in non-acclimatised individuals. Within the last decade, studies
      have shown ultrasonography to be valuable in the accurate diagnosis of a variety of lung
      pathologies, including cardiogenic pulmonary edema, pleural effusion, pneumothorax, and lung
      consolidation. Recently, studies conducted in remote areas have demonstrated that ultrasound
      lung comets (B lines) can be used as a measure of sub-acute pulmonary edema and high altitude
      pulmonary edema in climbers ascending to altitude. These studies also demonstrated that small
      portable ultrasound devices are reliable at high altitude in a cold and hypobaric
      environment.

      So far all studies concerning the detection of comet tails as a measure of pulmonary edema
      have been done only in a healthy population. There is no study evaluating this topic in
      patients after lung transplantation.

      Study objectives (Hypothesis)

      The investigators want to assess the occurrence of of comet tails (B lines) as a measure of
      pulmonary edema among patients after lung transplantation and healthy individuals during an
      expedition to Mount Kilimanjaro.

      Study design

      Prospective observational single-center study.

      Study population

      10 patients > 2 years after lung transplantation and 10 healthy volunteers

      Methods

      The investigators will do the ultrasound examinations using the portable V-scan
      ultrasonography device (GE Healthcare) with a dual probe, including a phased array cardiac
      probe on one side and a linear probe on the other side.

      Examinations will be done at sea level (before and right after the expedition), on the 3rd
      day at Shira hut at 3840 m and on the 6th day at Barafu camp at 4600m (highest camp site
      before summiting). Examinations will be done at the camp sites in a tent to assure good
      examination conditions for the patients.

      Lung ultrasound will be performed with the patient in supine position. The phased-array
      transducer will be used for lung ultrasound, and will be used for the assessment of B-lines,
      which arise from the pleural line to the bottom of the screen and move with the sliding lung.
      The investigators will quantify the B- line burden in lung regions using the validated
      Eight-region method: Each hemithorax is divided into four quadrants, upper and lower anterior
      and upper and lower lateral divided longitudinally by the anterior axillary line and
      transversely by the 2nd intercostal space. If 3 or more B-lines (any size and spaced apart by
      any distance) are present in a particular region, that region is considered positive. Two or
      more positive regions per side define a "B-line pattern."

      Measurement of optic nerve sheath diameter will be performed with a linear transducer placed
      superior and lateral to the eye, above the upper eyelid. The patient will be positioned
      supine, with a 30 degree head elevation. After visualization of the entry of the optic nerve
      into the globe, we will freeze the image. Optic nerve sheath diameter will be measured 3mm
      behind the globe in a perpendicular axis to the nerve. Two measurements will be taken per
      eye, and the mean of the 4 values will represent the optic nerve sheath diameter. A nerve
      sheath diameter of more than 5.8mm is defined as equivalent with an intracranial pressure
      (ICP) of more than 20mmHg.
    

Intervention name(s): lung ultrasound
Intervention type(s): Diagnostic Test
Intervention description(s): lung ultrasound with positive "B-line pattern" in patients after lung transplantations and healthy volunteers at sea level and high altitude (4600 m) at Mountb Kilimanjaro
Observational model: Other
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        10 patients > 2 years after lung transplantation and 10 healthy volunteers during
        expedition to Mount Kilimanjaro