LUNG ULTRASOUND (LUS SCORE) IN PREGNANT WOMEN WITH COVID-19: CORRELATION WITH CT SEVERITY SCORE, PHENOTYPE, AND ALTITUDE OF RESIDENCE

Introduction. Lung ultrasound (LUS) is regarded as a fetus-safe alternative to computed tomography (CT) for the diagnosis and monitoring of COVID-19 pneumonia in pregnant women. However, data on the diagnostic value of LUS score at high altitude, where the baseline pulmonary pattern may be altered by chronic hypobaric hypoxia, remain extremely limited.

Aim. To assess lung LUS score and CT severity score in pregnant women with COVID-19 according to disease severity, pathogenetic phenotype, and altitude of permanent residence (high altitude/low altitude).

Materials and methods. A prospective cohort study included 600 pregnant women with laboratory-con­firmed COVID-19 (252 at high altitude, >2500 m; 348 at low altitude, <500 m), stratified by disease severity (mild, n=350; moderate, n=164; severe, n=86) and by pathogenetic phenotype (inflammatory-cytokine, n=250; endothelial-coagulation, n=180; hypoxic-adaptive, n=170). Lung ultrasound was performed using a standardized 12-zone proto­col with calculation of LUS score (range 0-36 points; >8 points indicating clinically significant lung involvement, >15 points indicating high risk of ARDS). Chest CT was performed on strict indications with calculation of CT severity score (range 0-20 points). Oxygen saturation (SpO2) at rest and on exertion were additionally analyzed as functional cor­relates of lung involvement.

Results. Lung LUS score in pregnant women with COVID-19 averaged 10.54±0.273 points in mild disease, 10.36±0.38 points in moderate disease, and 11.01±0.539 points in severe disease, with no statistically significant inter­group differences (p(1/3)=0.448). CT severity score showed a similar pattern: 8.39±0.244, 8.12±0.354, and 8.64±0.518 points, respectively (p(1/3)=0.656). The proportion of ground-glass opacities on CT ranged from 40.33% to 42.81% without significant dynamics (p(1/3)=0.778). At the same time, functional oxygenation indices showed a pronounced and statistically significant dependence on altitude of residence: resting SpO2 at high altitude was 92.31±0.134% versus 96.03±0.094% at low altitude (p≤0.001), and exertional SpO2 was 89.35±0.169% versus 93.95±0.134% (p≤0.001). In patients with the hypoxic-adaptive phenotype at high altitude, resting SpO2 decreased from 93.18±0.132% in mild disease to 89.00±0.001% in severe disease (p=0.001 for all pairs), while the LUS score threshold of >8 points built into the criteria for this phenotype was reached at only moderate SpO2 decline, well before overt clinical respiratory failure developed.

Conclusion. Lung LUS score and CT severity score in pregnant women with COVID-19 do not show a direct, statistically significant association with disease severity, reflecting a discordance between the extent of structural lung damage and clinical severity, which is particularly pronounced at high altitude. Functional oxygenation indices (resting and exertional SpO2) proved to be a significantly more sensitive marker of the severity of hypoxic injury than an isolated lung ultrasound score. This supports the need for comprehensive interpretation of LUS score together with saturation indices, particularly when stratifying the hypoxic-adaptive phenotype of COVID-19 in pregnant women at high altitude, where occult hypoxemia may precede the formation of pronounced ultrasound changes.