Tidal Volume during Assisted Ventilation after Double-Lung Transplantation

Risk factors and prognosis of airway complications in lung transplant recipients: A systematic review and meta-analysis

BACKGROUND

Airway complications (AC) are one of leading causes of morbidity and mortality after lung transplant (LTx), but their predictors and outcomes remain controversial. This study aimed to identify potential risk factors and prognosis of AC.

METHODS

A systematic review was performed by searching PubMed, Embase, and Cochrane Library. All observational studies reporting outcome and potential factors of AC after LTx were included. The incidence, mortality, and estimated effect of each factor for AC were pooled by using the fixed-effects model or random-effects model.

RESULTS

Thirty-eight eligible studies with 52,116 patients undergoing LTx were included for meta-analysis. The pooled incidence of AC was 12.4% (95% confidence interval [CI] 9.5-15.8) and the mean time of occurrence was 95.6 days. AC-related mortality rates at 30-days, 90-days, 6 months, 1 year, and 5 years were 6.7%, 17.9%, 18.2%, 23.6%, and 66.0%, respectively. Airway dehiscence was the most severe type with a high mortality at 30 days (60.9%, 95% CI 20.6-95.2). We found that AC was associated with a higher risk of mortality in LTx recipients (hazard ratio [HR] 1.71, 95% CI 1.04-2.81). Eleven significant predictors for AC were also identified, including male donor, male recipient, diagnosis of COPD, hospitalization, early rejection, postoperative infection, extracorporeal membrane oxygenation, mechanical ventilation, telescopic anastomosis, and bilateral and right-sided LTx.

CONCLUSION

AC was significantly associated with higher mortality after LTx, especially for dehiscence. Targeted prophylaxis for modifiable factors and enhanced early bronchoscopy surveillance after LTx may improve the disease burden of AC.

Mechanical ventilation post-bilateral lung transplantation: A scoping review

BACKGROUND

Evidence from lung protective ventilation (LPV) in the acute respiratory distress syndrome has commonly been applied to guide periprocedural ventilation in lung transplantation. However, this approach may not adequately consider the distinctive features of respiratory failure and allograft physiology in the lung transplant recipient. This scoping review was conducted to systematically map the research describing ventilation and relevant physiological parameters post-bilateral lung transplantation with the aim to identify any associations with patient outcomes and gaps in the current knowledge base.

METHODS

To identify relevant publications, comprehensive literature searches of electronic bibliographic databases were conducted with the guidance of an experienced librarian in MEDLINE, EMBASE, SCOPUS and the Cochrane Library. The search strategies were peer-reviewed using the PRESS (Peer Review of Electronic Search Strategies) checklist. The reference lists of all relevant review articles were surveyed. Publications were included in the review if they described relevant ventilation parameters in the immediate post-operative period, published between 2000 and 2022 and involved human subjects undergoing bilateral lung transplantation. Publications were excluded if they included animal models, only single-lung transplant recipients or only patients managed with extracorporeal membrane oxygenation.

RESULTS

A total of 1212 articles were screened, 27 were subject to full-text review and 11 were included in the analysis. The quality of the included studies was assessed to be poor with no prospective multi-centre randomised controlled trials. The frequency of reported retrospective LPV parameters was as follows: tidal volume (82%), tidal volume indexed to both donor and recipient body weight (27%) and plateau pressure (18%). Data suggest that undersized grafts are at risk of unrecognised higher tidal volume ventilation indexed to donor body weight. The most reported patient-centred outcome was graft dysfunction severity in the first 72 h.

CONCLUSION

This review has identified a significant knowledge gap that indicates uncertainty regarding the safest ventilation practice in lung transplant recipients. The risk may be greatest in patients with established high-grade primary graft dysfunction and undersized allografts, and these factors may define a sub-group that warrants further investigation.

Pulmonary volume-feedback and ventilatory pattern after bilateral lung transplantation using neurally adjusted ventilatory assist ventilation

BACKGROUND

Bilateral lung transplantation results in pulmonary vagal denervation, which potentially alters respiratory drive, volume-feedback, and ventilatory pattern. We hypothesised that Neurally Adjusted Ventilatory Assist (NAVA) ventilation, which is driven by diaphragm electrical activity (EAdi), would reveal whether vagally mediated pulmonary-volume feedback is preserved in the early phases after bilateral lung transplantation.

METHODS

We prospectively studied bilateral lung transplant recipients within 48 h of surgery. Subjects were ventilated with NAVA and randomised to receive 3 ventilatory modes (baseline NAVA, 50%, and 150% of baseline NAVA values) and 2 PEEP levels (6 and 12 cm H₂O). We recorded airway pressure, flow, and EAdi.

RESULTS

We studied 30 subjects (37% female; age: 37 (27-56) yr), of whom 19 (63%) had stable EAdi. The baseline NAVA level was 0.6 (0.2-1.0) cm H₂O μV^-1. Tripling NAVA level increased the ventilatory peak pressure over PEEP by 6.3 (1.8), 7.6 (2.4), and 8.7 (3.2) cm H₂O, at 50%, 100%, and 150% of baseline NAVA level, respectively (P<0.001). EAdi peak decreased by 10.1 (9.0), 9.5 (9.4) and 8.8 μV (8.7) (P<0.001), accompanied by small increases in tidal volume, 8.3 (3.0), 8.7 (3.6), and 8.9 (3.3) ml kg^-1 donor's predicted body weight at 50%, 100%, and 150% of baseline NAVA levels, respectively (P<0.001). Doubling PEEP did not affect tidal volume.

CONCLUSIONS

NAVA ventilation was feasible in the majority of patients during the early postoperative period after bilateral lung transplantation. Despite surgical vagotomy distal to the bronchial anastomoses, bilateral lung transplant recipients maintained an unmodified respiratory pattern in response to variations in ventilatory assistance and PEEP.

CLINICAL TRIAL REGISTRATION

NCT03367221.