An Analysis of Biomechanical and Physiological Changes During Abdominal Wall Reconstruction.

Abstract

<h4>Introduction</h4>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.<h4>Materials and methods</h4>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.<h4>Results</h4>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 (<i>P</i> < 0.001). Increased midline closure distance was positively associated with increased closure force (<i>P</i> = 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 (<i>P</i> = 0.05, 6.23L 95% CI 0.05 to 12.4; <i>P</i> = 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.<h4>Discussion</h4>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.