Computational Fluid Dynamics (CFD) Analysis of Subject-specific Bronchial Tree Models in Lung Cancer Patients

Lung resection is the only potentially curative treatment for lung cancer. The inevitable partial removal of functional lung tissue along with the tumoral mass requires a careful and structured pre-operative condition of patients. In particular, the postoperative residual functionality of the lung needs to be predicted. Clinically, this is assessed through algorithms based on pulmonary function tests (PFTs). However, these approaches neglect the local airway segment's functionality and provide a globally averaged evaluation. CFD was demonstrated to provide patient-specific, quantitative, and local information on flow dynamics and regional ventilation in the bronchial tree. This study aims to apply CFD to characterize the flow dynamics in 12 patients affected by lung cancer and evaluate the effects of the tumoral masses on flow parameters and lobar flow distribution. Patient-specific airway models were reconstructed from CT images, and the tumoral masses were manually segmented. Measurements of lungs and tumor volumes were collected. A peripherality index was defined to describe tumor distance from the parenchyma. CFD simulations were performed in Fluent^®, and the results were analyzed in terms of flow parameters and lobar volume flow rate (VFR). The predicted postoperative forced expiratory volume in 1s (ppoFEV1) was estimated and compared to the current clinical algorithm. The patients under analysis showed relatively small tumoral masses located close to the lung parenchyma. CFD results did not highlight lobar alterations of flow parameters, whereas the flow to the lung affected by the tumor was found to be significantly lower (p=0.026) than the contralateral lung. The estimation ppoFEV1 obtained through the results of the simulations showed a high correlation (ρ=0.993, p<0.001) with the clinical formula.Clinical Relevance- The proposed study establishes the efficacy and applicability of CFD for the pre-operative characterization of patients undergoing lobectomy surgery. This technique can provide additional information on local functionality and flow dynamics to support patients' operability.

Surveillance Transbronchial Biopsy Program to Evaluate Acute Rejection After Lung Transplantation: A Single Institution Experience

BACKGROUND

There is no unanimity in the literature regarding the value of transbronchial biopsies (TBBs) performed at a scheduled time after lung transplantation (surveillance TBBs [SBs]), compared to biopsies performed for suspected clinical acute rejection (clinically indicated TBBs [CIBs]). This study exposes an assessment of our experience over the last 4 years through a retrospective analysis of the data collected.

METHODS

In our center, SBs are performed at 3, 6, and 12 months after a transplant. Data from 110 patients who underwent a TBB were collected from January 2013 to November 2017. Clinical and functional data along with the histologic results and complications were collected.

RESULTS

Overall 251 procedures were performed: 223 for surveillance purposes and 28 for clinical indications. The SBs diagnostic rate was 84%. A grade 2 acute rejection (AR) was detected in 9 asymptomatic patients, all of whom were medically treated, with downgrading of AR documented in all cases. The rate of medical intervention in the SB group was 8%. The CIBs diagnostic rate was 96%. The rate of AR detected by CIBs was significantly higher than by SBs (36% versus 4%; P < .0001). Overall the major complication rate was 4%; no patients required transfusions and no mortality occurred in the patient cohort.

CONCLUSIONS

The surveillance protocol did not eliminate the necessity of CIBs, but in 8% of patients early rejection was histologically assessed. The correlation between histologic and clinical data allows a more careful approach to transplanted patients.

Lung Transplantation From Donors After Previous Cardiac Surgery: Ideal Graft in Marginal Donor?

Lung transplantation is a limited by donor pool shortage. Despite the efforts to extend the graft acceptability with recurrent donor criteria reformulations, previous cardiothoracic surgery is still considered a contraindication. A donor who underwent cardiac surgery could potentially provide an ideal lung but high intraoperative risks and intrinsic technical challenges are expected during the graft harvesting. The purpose of this study is to present our dedicated protocol and four clinical cases of successful lung procurements from donors who had a previous major cardiac surgery. One donor had ascending aortic root (AAR) substitution, another had mitral valve substitution, and two had coronary artery bypass surgery. The others' eligibility criteria for organ allocation, such as ABO compatibility, PaO₂/FiO₂ ratio, absence of aspiration, or sepsis were respected. In one of the cases with previous coronary bypass grafting, the donor had a veno-arterial extracorporeal membrane oxygenation support. Consequently, the grafts required an ex vivo lung perfusion evaluation. We report the technical details of procurement and postoperative courses of recipients. All procurements were uneventful, without lung damage or waste of abdominal organs related to catastrophic intraoperative events. All recipients had a successful clinical outcome. We believe that successful transplantation is achievable even in a complicated setting, such as cases involving donors with previous cardiac surgery frequently are. Facing lung donor shortage, we strongly support any effort to avoid the loss of possible acceptable lungs. In particular, previous major cardiac surgery does not strictly imply a poor quality of lungs as well as unsustainable graft procurement.

Lung Allocation Score: A Single-Center Simulation

BACKGROUND

The lung allocation score (LAS) was introduced in the United States in May 2005 with the main goal of reducing the waiting list mortality of patients with end-stage lung diseases, but also to enhance the lung transplant benefit and improve the management of urgent candidates. Several papers have reported that LAS resulted in a reduction of the waiting list mortality but no significant survival benefit was noted.

METHODS

We evaluate the usefulness of LAS as a predictor for lung transplantation outcome in 123 patients listed for lung transplantation in an Italian center. Primary endpoints were waiting list mortality and posttransplant mortality at 1 year; secondary endpoints included perioperative circulatory support, cardiopulmonary bypass, primary graft dysfunction, and long-term survival after transplantation.

RESULTS

We observed the absence of correlation between LAS and waiting list mortality. The LAS did not affect the long-term survival in our population.

CONCLUSIONS

High LAS was predictive of primary graft dysfunction of grade 3 in the first 72 hours after transplantation.