Performance of Fluid Infusion Systems in the Changing Atmospheric Pressures Encountered in Aviation
INTRODUCTION: With the increasing use of aeromedical transport for critically ill patients, it is essential to understand the impact of pressure changes on drug infusion delivery systems. As airplanes ascend and descend, gases/bubbles are released from solutions when ambient pressure decreases and dissolves when pressure increases. This may affect mechanical fluid delivery systems and cause clinically significant changes, especially within a critical care setting. We aimed to evaluate the impact of pressure changes on volumetric pumps and syringe drivers. METHODS: An in vitro study of six volumetric pumps and eight syringe drivers was conducted in a hypobaric chamber to mimic pressure changes during flights. Infusion devices were set to deliver water at 0.2 ml ⋅ h−1 and infused volumes were measured. There were 15 open-ended syringes also studied. RESULTS: During ascent, syringe drivers and volumetric pumps over-delivered 173 µL and 38 µL of fluid. During descent, syringe drivers under-delivered by 166 µL, whereas volumetric pumps under-delivered by 9 µL. Syringe drivers experienced statistically significant changes in fluid delivery during both ascent and descent. In volumetric pumps, only the descent phase infusion differed significantly from other phases. The volume of fluid expansion is dependent on volume and the mechanical properties of the fluid. DISCUSSION: Decreasing ambient pressure causes bubble formation, which displaces fluid, and increasing ambient pressure causes bubble reabsorption in mechanical infusion devices. Hence, atmospheric pressure changes during air travel may alter fluid delivery from medical fluid delivery systems and affect critically ill patients who require both aeromedical evacuation and accurate infusion of drugs. Fan KS, Paterson M, Shojaee-Moradie F, Manoli A, Edwards V, Lee V, Hutchison E, Gifford RM, Parsons IT, Koehler G, Mathieu C, Mader JK, King BR, Russell-Jones D; EASA Consortium. Performance of fluid infusion systems in the changing atmospheric pressures encountered in aviation. Aerosp Med Hum Perform. 2025; 96(1):4–11.
Experimental setup. A) Design of infusion lines and syringe/capillary tubes for measurements; B) Open-ended syringes mounted against cardboard prior to installation in hypobaric chamber; C) Syringe driver experimental setup, with B. Braun syringe drivers connected to vertically anchored, open-ended syringes via infusion extension sets.
Syringe driver fluid delivery during simulated flight in relation to the measured infusion rate of 200 µL · h−1 at ground level. This aggregates observations from a total of 9 Alaris and 15 Braun syringe drivers.
Volumetric pump fluid delivery during simulated flight in relation to the measured infusion rate of 200 µL · h−1 at ground level. This aggregates observations from a total of 5 Alaris and 12 Braun volumetric pumps.
Comparison of mean volume change by syringe volume and fluid type based on the aggregated results of 116 syringe-tests.
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