## 4 Discussion
It is also important to consider that fluid collection viscosities can vary greatly depending on the individual and their body type and pathology; since we did not explicitly measure the fluid viscosities or densities, we can only draw a comparison between the broad categories and cannot specifically control for the densities. An additional benefit of incentive spirometry (IS) is the abdominal postoperative prevention of respiratory complications and venous stasis. Upper abdominal surgeries are associated with a functional residual capacity (FRC) reduction of approximately 35%, while lower abdominal surgeries are associated with a 10-15% FRC reduction [19; 20]. Pain from the abdominal wound and impaired respiratory muscle function may persist in these patients for up to a week before gradually returning to baseline. The reduced activity of these muscles is more frequently observed in upper abdominal surgeries compared to lower (20-40% vs. 2-5%, respectively) [16; 21; 22]. The most common complications following upper abdominal surgery are pulmonary complications (such as atelectasis) [16; 20; 23; 24], with incidence ranging as high as 80% [16; 24; 25]. To treat or prevent these complications, pulmonary physical therapy is often prescribed [26; 27; 28; 29; 30]. Common pulmonary physical therapy methods used to treat or prevent these complications include incentive spirometry (IS), deep breathing exercises (DBEX), and intermittent positive pressure breathing (IPPB). IS improves lung aeration and expansion, leading to protection against respiratory complications. Furthermore, post-operative venous stasis can be alleviated by deep inspiration, which increases the venous blood return to the heart [31]. According to [PERSON] and [PERSON] and a study conducted by [PERSON] et al. [32], the movement of the diaphragm in conjunction with the contraction of abdominal and pelvic floor muscles causes an increase in intra-abdominal pressure during inspiration [32; 33; 34]. The prolonged inspiration of incentive spirometry leads to a subsequent increase in abdominal pressure. An elevation in abdominal pressure can assist with drainage catheter patency, which presumably assists in the full evacuation of fluid collections. It has been shown that intra-abdominal pressure increases after abdominal surgery [16; 35; 36] and also during inspiration [33; 34] and other physical movements such as ambulation [28; 37]. The physics and fluid mechanics of drainage catheters have been previously described as following Poiseuille's law [14]. Previous studies describe the effect that decreased length and increased catheter diameter can have on flow [14; 38]. As a result, it may be prudent to not only consider the use of incentive spirometry to increase the pressure differential, but also in conjunction with the use of a short tube. Our results align with these findings. There are several limitations to the present study. Most notably, the flow rate through the drainage catheters was not measured, neither during baseline nor during either of the incentive spirometry therapies. Secondly, this study only describes a patient population with a single drainage catheter; no data was gathered for patients with multiple catheters. Finally, the study is constrained by a small sample size due to resource limitations and enrollment criteria, potentially limiting the statistical power to detect significant differencesbetween regions. However, this study serves as an important initial step in raising pertinent questions regarding the role of incentive spirometry in managing intra-abdominal pressure. The findings provide a rationale for future larger-scale studies. Additionally, the data is derived from a single institution, as the study was originally designed as a feasibility investigation to evaluate the impact of incentive spirometry on intra-abdominal pressure within our institution. Limited resources, such as time and funding, hindered our ability to coordinate a multi-center study at this stage.