Influencing Factors of Air Bubble-Induced Pressure Difference in Drainage Tubes: An In Vitro Study

This study evaluated the effect of the presence of air bubbles in a drainage tube on its pressure difference and analyzed the relationship between air bubble volume, tube diameter, drainage fluid viscosity, and pressure difference. Accordingly, it provides a theoretical basis for optimizing drainage treatment and preventing obstruction in clinical practice.

A custom-designed experimental device was used to measure the pressure difference in medical-grade silicone drainage tubes. Tubes with various diameters (3 and 6 mm), air bubble volumes (0, 0.1, 0.2, and 0.3 mL), and drainage fluids (low and high viscosities) were used. The pressure difference between the two ends of each drainage tube was measured using a pressure sensor and calculated. A rotational viscometer was used to measure the viscosity of each drainage fluid. Differences in the pressure difference under different conditions of air bubbles, air bubble volumes, tube diameters, and drainage fluid viscosities were compared.

The presence of air bubbles in each drainage tube significantly increased the pressure difference, with the pressure difference being higher compared to that under the bubble-free condition (0.591 ± 0.069 vs. 0.830 ± 0.039 kPa, p < 0.01). In addition, the pressure difference progressively increased with increasing air bubble volume, with the maximum increase occurring at a bubble volume of 0.3 mL (0.951 ± 0.039 kPa). The pressure difference was negatively correlated with the tube diameter, with higher pressure difference observed at smaller diameters, and the differences between the values of the different diameter groups were statistically significant (p < 0.01). The pressure difference was positively correlated with the viscosity of the drainage fluid, with a higher pressure difference observed at a higher viscosity. The enhancing effect of air bubbles on the pressure difference was more pronounced in more viscous fluids (p < 0.0001).

This study showed that the presence of air bubbles in a drainage tube significantly increases the outflow pressure difference, and this effect is enhanced by increasing the bubble volume, decreasing the tube diameter, and increasing the drainage fluid viscosity. These findings reveal that the hydrodynamic factors associated with air bubbles can theoretically contribute to a poor outflow. Therefore, they provide a preliminary in vitro basis for exploring the rational selection of drainage tube diameter, early detection of air bubble-related obstructions, and development of targeted interventions in future clinical practice.