Background: The comet-tail technique of chest ultrasonography has been described for the diagnosis of cardiogenic pulmonary edema. This is the first report describing its use for the diagnosis and monitoring of high-altitude pulmonary edema (HAPE), the leading cause of death from altitude illness.
Methods: Eleven consecutive patients presenting to the Himalayan Rescue Association clinic in Pheriche, Nepal (4,240 m) with a clinical diagnosis of HAPE underwent one to three chest ultrasound examinations using the comet-tail technique to determine the presence of extravascular lung water (EVLW). Seven patients with no evidence of HAPE or other altitude illness served as control subjects. All examinations were read by a blinded observer.
Results: HAPE patients had higher comet-tail score (CTS) [mean ± SD, 31 ± 11 vs 0.86 ± 0.83] and lower oxygen saturation (O2Sat) [61 ± 9.2% vs 87 ± 2.8%] than control subjects (p < 0.001 for both). Mean CTS was higher (35 ± 11 vs 12 ± 6.8, p < 0.001) and O2Sat was lower (60 ± 11% vs 84 ± 1.6%, p = 0.002) at hospital admission than at discharge for the HAPE patients with follow-up ultrasound examinations. Regression analysis showed CTS was predictive of O2Sat (p < 0.001), and for every 1-point increase in CTS O2Sat fell by 0.67% (95% confidence interval, 0.41 to 0.93%, p < 0.001).
Conclusions: The comet-tail technique effectively recognizes and monitors the degree of pulmonary edema in HAPE. Reduction in CTS parallels improved oxygenation and clinical status in HAPE. The feasibility of this technique in remote locations and rapid correlation with changes in EVLW make it a valuable research tool.