Factors associated with B-lines after exposure to hypobaric hypoxia

Area of Science:

• Pulmonary Medicine
• Cardiovascular Physiology
• Diagnostic Imaging

Background:

• Increased extravascular lung water (EVLW) manifests as B-lines on chest ultrasonography.
• The dynamics of B-lines, their clinical relevance, and influencing factors during high-altitude exposure in lowlanders remain incompletely understood.

Purpose of the Study:

• To prospectively monitor lung ultrasound B-lines, clinical status, and N-terminal B-type natriuretic peptide (NT-proBNP) levels in individuals ascending to high altitude.

Main Methods:

• 19 participants underwent chest ultrasonography, blood sampling, and cardiovascular monitoring at baseline and up to 8 days at 3830m.
• Signs and symptoms of high altitude pulmonary edema (HAPE) were assessed, and generalized estimating equations analyzed factors associated with B-lines.
• Confounding factors like altitude variations and physical exertion were minimized.

Main Results:

• B-lines exhibited a parabolic pattern within 72 hours of altitude exposure (P = 0.006), with 55.6% showing >5 B-lines at 24 hours.
• B-lines correlated with symptom severity (P = 0.001) and were associated with time, sex, and SpO2 (P = 0.042), but not NT-proBNP (P = 0.546).
• A patient diagnosed with HAPE presented with 23 B-lines.

Conclusions:

• Altitude-induced B-lines reflect individual physiological responses to hypobaric hypoxia and clinically significant lung alterations.
• These findings support a non-cardiogenic origin for B-lines, even in cases of HAPE.
• B-lines serve as a clinically relevant indicator of lung changes during high-altitude exposure.