Chest ultrasound diagnoses high-altitude pulmonary edema

A technique previously shown to diagnose cardiogenic pulmonary edema has now been used to successfully diagnose pulmonary edema brought on by high altitude. Pulmonary edema is the primary cause of death from altitude sickness, and ultrasound could be an effective, low-cost test suitable for field hospitals.

Dr. Peter J. Fagenholz from the surgery department at Massachusetts General Hospital and colleagues examined 11 consecutive patients at the Himalayan Rescue Association clinic in Pheriche, Nepal. This high-altitude aid station is located 4240 meters above sea level and is the primary health facility available to climbers on Mt. Everest.

All 11 patients were previously diagnosed with high-altitude pulmonary edema. Each patient was given up to three chest ultrasound exams, with the blinded reader looking for the characteristic comet-tail sign indicating extravascular lung water. Seven patients with no symptoms of altitude sickness or cardiogenic pulmonary edema were also examined with chest ultrasound as controls.

The patients previously diagnosed with high-altitude pulmonary edema had comet-tail scores with a mean of 31 ± 11, while the mean score in the control group was 0.86 ± 0.83. The patients with altitude sickness also had lower oxygen saturation levels, at 61 ± 9.2% versus 87 ± 2.8%.

For those patients who had follow-up ultrasound exams, researchers also found that comet-tail scores were higher and oxygen saturation was lower when the patients first arrived at the clinic. They had a mean comet-tail score of 35 ± 11 on admission and a mean comet-tail score of 12 ± 6.8 at discharge. The mean oxygen saturation levels were 60 ± 11% on admission and 84 ± 1.6% when the patients were discharged.

Regression analysis also showed comet-tail scores were predictive of oxygen saturation. For each point a comet-tail score went up, oxygen saturation went down by 0.67% (with a confidence interval of 95%).

The researchers concluded that chest ultrasound showing comet-tail sign can be an effective tool in diagnosis of high-altitude pulmonary edema, and can also monitor the severity of the condition. The potential availability of this test in remote clinical locations makes it a useful diagnostic and monitoring tool for patients presenting with altitude sickness.