[ca] Aquesta tesi inclou dos estudis que fan noves contribucions al coneixement sobre les causes, el pronòstic i el maneig de la insuficiència respiratòria aguda en el pacient amb trasplantament de pulmó. L'estudi 1 va ser el primer estudi prospectiu en mostrar una associació entre els nivells de procalcitonina (PCT) durant el període postoperatori (72h) i la funció de l'empelt a les 72h del trasplantament. Es va demostrar que un punt de tall de PCT<2 ng/ml dins de les primeres 24h té un alt valor per excloure la disfunció primària de l'empelt (DPE) grau 3 a les 72h i per predir la supervivència a la UCI. A més, tant la PCT com la IL-10 a les 48h es van associar amb una funció de l'empelt millor un any després de la cirurgia. L'estudi 2 ha estat l'estudi prospectiu multicèntric més gran fet fins ara, sobre trasplantats de pulmó que reingressen a la UCI més enllà del període postoperatori. La insuficiència respiratòria aguda va ser el principal condicionant de reingrés i es va associar amb una alta mortalitat. La pneumònia bacteriana es va identificar com la causa principal reingrés (i un factor de risc independent de mortalitat) a la UCI, essent P. aeruginosa el principal patogen, mentre l'aspergil·losi, P. jiroveci i els virus respiratoris (inclosa la grip) van ser causes poc prevalents. El rebuig de l'empelt va ser relativament infreqüent (només el 5% dels pacients van ingressar per rebuig agut de l'empelt), i la presència d'anticossos específics anti-HLA de el donant abans de l'admissió a la UCI no va influir en els resultats. En contrast, la DCE es va identificar com un predictor significatiu de mort; la supervivència es va correlacionar inversament amb la gravetat de l'obstrucció en el fenotip obstructiu, i el fenotip restrictiu s'ha de considerar com una indicació per a cures pal·liatives.

[en] This thesis includes two studies that make new contributions to the knowledge on the causes, prognosis and management of acute respiratory failure in the patient with lung transplantation (LT). Study 1 was designed to evaluated the association of procalcitonin (PCT), IL-6-8-10 plasma levels at 24h, 48h and 72h in adults after LT with ICU-mortality, oxygenation, diagnosis and severity of primary graft dysfunction (PGD), and one-year graft function after LT. One hundred LT patients were enrolled consecutively at ICU admission following LT in Vall d&#8217;Hebron University Hospital and followed until one year after the transplant. Higher PCT levels at 24h were associated with lower PaO2 / FIO2 ratio and Grade 3 PGD over the first 72h after LT (p <0.05). PCT at 24h was higher in the 9 patients who died (2.90 vs 1.47 ng/mL, p <0.05), with AUC = 0.74 for predicting ICU-mortality. All patients with PCT < 2 ng/ml at 24h following LT, survived in the ICU (p <0.05). PCT and IL-10 at 48h were correlated with FEV1 (rho = -0.35) and FVC (rho = -0.29) one year after LT. (p <0.05). This was the first prospective study showing an association between the PCT plasma levels in the post-operative period (72h) and graft function at 72h after LT. Results showed that a breakpoint of PCT < 2 ng/mL within 24h has a high predictive value to exclude grade 3 PGD at 72h and for ICU-survival. Moreover, both PCT and IL-10 within 48 hours were associated with significantly better graft function one year after surgery. Study 2 aimed to assess the main causes of intensive care readmissions (ICUr) in LT adults and to identify independent predictors of ICU-mortality (primary end-point). This Spanish 5-centre prospective cohort study enrolled all LT adults with ICUr after post-LT ICU discharge, between 2012 and 2016. Patients were followed until hospital discharge or death. One hundred and fifty-three LT recipients presented 174 ICUr a median of six months [IQR 2-25] post-LT. Chronic lung allograft dysfunction (CLAD) was reported in 39 (25.5%) recipients, 13 of whom (all exitus) had restrictive allograft syndrome (RAS). Acute respiratory failure (ARF) (110, 71.9%) was the main condition requiring ICUr. Graft rejection (six, 5% acute) caused only 12 (11%) admissions whereas pneumonia (56, 36.6%) was the main cause (50 admitted for ARF and 6 for shock), with P. aeruginosa (50% multidrug-resistant) being the predominant pathogen. Fifty-five (35.9%) and 69 (45.1%) recipients died in the ICU and the hospital respectively. Bronchiolitis obliterans syndrome (BOS) stage-2 (adjusted-OR: 7.2 (1-65.7)), BOS stage-3 (aOR: 13.7 (2.5-95.3)), RAS (aOR: >50) and pneumonia at ICUr (aOR: 2.5 (1-7.1)) were identified in multivariate analyses as independent predictors of ICU mortality. Only eight (5%) patients had positive donor-specific antibodies (DSA) prior to ICUr, and this variable did not affect the model. This was the largest prospective, multi-centre cohort study to date on LT recipients in the ICU beyond the post-operative period. ARF was the main condition requiring ICUr in LT recipients, and was associated with high mortality. Importantly, bacterial pneumonia was identified as the main cause of ICUr (and an independent risk factor for ICU-mortality), with P. aeruginosa being the main pathogen. Aspergillosis, P. jiroveci and respiratory virus pulmonary infections (including influenza) were unlikely causes of severe ARF. Graft rejection was relatively infrequent (only 5% of patients were admitted for acute allograft rejection), and presence of DSA before ICU admission did not influence outcomes. In contrast, CLAD was identified as a significant predictor of death; survival was inversely correlated with severity of obstruction in the BOS phenotype, and the RAS phenotype should be considered as an indication