This four-group prospective study will enroll travelers who have independently booked economy or premium business/first-class flights to Bogota. Within each cabin stratum, participants will be randomized to moderate graduated compression stockings or no stockings. Bilateral popliteal vein ultrasound will be performed before flight, within 2 hours after arrival, and at 24 and 48 hours. The primary outcome is the interaction between cabin class and compression assignment for change in mean bilateral popliteal vein diameter.
Age 18 to 65 years.
Commercial itinerary to Bogota with at least 4 hours of total airborne time.
Prebooked premium business/first-class or economy-class cabin documented before randomization.
No medical requirement for or contraindication to graduated compression stockings.
Current deep venous thrombosis, therapeutic anticoagulation, or severe peripheral arterial disease.
Pregnancy.
Lower-extremity skin, neurologic, or anatomic condition preventing safe stocking use or ultrasound.
Cabin upgrade or downgrade after randomization that changes the prespecified stratum.
Parallel
Knee-High Graduated Compression Stockings
DevicePROPOSED pressure class: 20-30 mmHg at the ankle, properly fitted and worn from approximately 1 hour before boarding through the arrival ultrasound. Product and pressure class require confirmation. Linked arm/group(s): Economy Cabin Plus Compression, Premium Cabin Plus Compression.
Economy Cabin Exposure
Other interventionPrebooked and completed economy-cabin travel; seat characteristics and behavior are measured but not assigned. Linked arm/group(s): Economy Cabin Plus Compression, Economy Cabin Without Compression.
Premium Cabin Exposure
Other interventionPrebooked and completed business/first-class travel; seat characteristics and behavior are measured but not assigned. Linked arm/group(s): Premium Cabin Plus Compression, Premium Cabin Without Compression.
Standardized Bilateral Popliteal Vein Ultrasound
Diagnostic testTriplicate bilateral diameter and cross-sectional-area measurements before flight and at arrival, 24 hours, and 48 hours by an assessor masked to stocking allocation. Linked arm/group(s): Economy Cabin Plus Compression, Economy Cabin Without Compression, Premium Cabin Plus Compression, Premium Cabin Without Compression.
Cabin-Class-by-Compression Interaction in Change in Popliteal Vein Diameter
Interaction term between prebooked cabin stratum and randomized stocking assignment for the change in participant-level mean bilateral popliteal vein diameter from preflight baseline to arrival.
Randomized Compression Stocking Effect on Arrival-Related Diameter Change
Adjusted mean difference between stocking and no-stocking assignments overall and separately within each cabin stratum.
Adjusted Cabin-Class Association With Arrival-Related Diameter Change
Adjusted mean difference between premium and economy cabin groups overall and separately by stocking assignment. This contrast is observational because cabin class is not randomized.
Four-Group Popliteal Vein Diameter Trajectory
Estimated mean bilateral diameter and change from baseline in each of the four groups across postarrival time points.
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