Comparison of thoracostomy tube size with pleural fluid dynamics in serous and hemorrhagic fluid models: an experimental study

BACKGROUND: Chest tube insertion is a standard medical procedure employed in the management of pleural effusion. Thoracostomy tubes are available in a range of sizes and for various purposes. The literature frequently recommends the use of smaller tubes to manage mild and/or serous effusion and states larger tubes should be used in cases of hemorrhagic and/or exudative effusion. However, many other studies have reported that the use of smaller or mid-sized tubes is sufficient and effective in the majority of effusion cases, regardless of fluid characteristics and volume. This study aimed to compare the fluid dynamics of different tube sizes in serous and hemorrhagic fluid models.METHODS: This is an experimental study constructed at a physical laboratory at our unit. There were two experimental groups: a serous and a hemorrhagic model. The serous fluid (water) model had an estimated viscosity of 0.89 cP, while the hemorrhagic model (water and glycerin) had an estimated viscosity of 3.9-4.7 cP. Fluid dynamics were measured using a flowmeter for different tube sizes (20 Fr, 24 Fr, 28 Fr and 32 Fr). The outcomes measured were: 1) flow debit (mL/s); and 2) comparative analyses between flow debit and tube size. Statistical analyses were performed using SPSS v.22.0.RESULTS: Flow speeds in the serous fluid model were faster than those in the hemorrhagic model. This was observed for all tube sizes and indicated by a shorter period required to empty the box. The fluid velocity in the serous group increased as tube size increased (18.7-40.56 mL/s). In the hemorrhagic group, the fastest debit was measured on the 28 Fr tube (85.82-989.75 seconds). In both groups, there was a significant correlation between flow speed and tube size (P<0.001); in general, the greater the diameter, the faster the fluid flow. However, a discrepancy was observed in the hemorrhagic model, in that the fastest measured flow was recorded for the 28 Fr tube (2.02±0.02 mL/s) and not the larger 32 Fr tube (1.47±0.07 mL/s). Flows recorded for the narrower tubes were much slower (20 Fr: 0.06±0,01; 24 Fr: 0.28±0.01 mL/s).CONCLUSIONS: This experiment demonstrated that the use of a 28 Fr tube is likely to be as efficacious as the use of a larger chest tube to manage pleural effusion, particularly in hemorrhagic cases. Effective, more convenient, and less painful drainage can be achieved with the use of a smaller tube size that allows faster drainage.