An Analysis of Biomechanical and Physiological Changes During Abdominal Wall Reconstruction

Abdominal wall reconstruction (AWR) creates biomechanical and physiological changes, impacting the respiratory system. We assessed how dynamic lung compliance (LC) changed in response to intra-abdominal pressure (IAP) and closure forces. Secondarily, we investigated if patient, radiological, or biomechanical factors were identifying predictors of physiological changes.

We performed a prospective observational study in patients undergoing complex ventral hernia repair. LC was measured during 3 intra-operative stages after full muscle relaxation. Primary outcome was change in LC between completion of adhesiolysis and closure. Additionally, we measured force and distance required for midline closure.

Nineteen patients (median age 63) underwent AWR. Median hernia volume was 437 cm³ (IQR, 233-1,608). Mean LC change was -6.8 mL/cmH₂O (±6 SD). Mean IAP increase was 3 mmHg (±1.7 SD). LC reduced and IAP increased between adhesiolysis and skin closure, significantly (P < 0.001). Increased midline closure distance was positively associated with increased closure force (P = 0.03, 0.12N, 95% CI 0.21-4.0). There was no evidence that increased closure force reduced LC or raised final IAP. Preoperative FEV1 and BMI were associated with reduced final LC (P = 0.05, 6.23L 95% CI 0.05 to 12.4; P = 0.03, -0.74 kg/m2, 95% CI -1.4 to -0.07). There was no evidence of an association between radiological measurements and change of LC or IAP.

Reduced LC is positively associated with increased IAP. However, there is no evidence increased closure forces affect final LC or IAP. Pre-operative optimisation of BMI or pre-operative FEV1 may have more impact than hernia morphology on LC reduction.