Phd in ADVANCES IN INFECTIOUS DISEASES, MICROBIOLOGY, LEGAL
MEDICINE AND PUBLIC HEALTH SCIENCES

Thesis title: HOSPITAL ACQUIRED PNEUMONIA IN PATIENTS WITH SARS-COV2 ARDS DURING NON-INVASIVE VENTILATION: A RETROSPECTIVE STUDY

INTRODUCTION Non Invasive Ventilation (NIV) may reduce in specific populations the risk of reintubation, mortality, length of stay and occurrence of lung infection. Uncertain results are described in literature in treatment in SARS-CoV2 pneumoniae, moreover in Hospital Acquired Pneumoniae (HAP) treatment. The objective was to evaluate incidence and prevalence of microbiological species in subjects who developed pneumonia following more than 48 h of consecutive NIV, who required subintensive care. The primary objective was to identify the disparate outcomes, in terms of mortality and risk of occurrence of new nosocomial infections, in the two populations. The secondary objective was to determine which traits related to host, disease, and hospitalisation-intrinsic factors can modify or affect the outcomes. MATERIALS AND METHODS We recruited retrospectively 84 subjects in Subintensive Respiratory Unit with SARS-CoV2 infection. 65 remaining patients without SARS CoV2, who received NIV treatment, were recruited as control. All patients underwent detailed medical history and examination, blood tests and routinary microbiological specimens. RESULTS 48 patients had HAP sustained by multidrug resistant (MDR) germs, 82 % of our population. An unexpected finding was in 18 cases of Extreme Drug Resistant – XDR Acinetobacter baumannii pneumonia (31.0 %), 10 cases of Staphylococco aureus methicillin-resistant (MRSA) (17.2 %), 7 cases of Klebsiella pneumoniae carbapenemase-producing (KPC) (8.6 %), 5 cases of Pseudomonas aeruginosa multi-drug resistant, (5.2 % in total). There is also one case of pulmonary aspergillosis (1.7 %). An high rate of polymicrobial infections was seen, overall 12 cases (20.7 %). Patients with SARS-CoV2 infection and HAP had the highest mortality rate (RR=45.361; 95 % CI 0.000 – 91.122; p=0.057). A previous MDR colonization is associated to increased risk of new pulmonary infection (OR=5.250; 95 % CI -0.01 – 0,12; p=0.023). Patients coming from other hospitals or care facilities, or from an ICU in the previous 30 days, had an augmented risk of a new HAP (respectively OR=8.313; 95 % CI 0.18 – 0.44; p=0.005 and OR=7.146; 95 % CI 0.00-0.15; p=0.008). A state of hypercapnia was associated to recurrence of HAP (OR 4.410; 95 % CI 0.46 – 0.73; p=0.038). At the blood test, a neutrophil/lymphocyte (N/L) ratio more than 20 was found to be related to a new acquired respiratory disease (OR 8.448; 95 % CI 0.32-0.60; p=0.004). SARS-CoV2 infection itself was associated to an increased mortality, with an OR 3.264 (95 % CI 0.49 – 0.70; p=0.073). HAP was correlated to an augmented mortality, with OR 4.016 (95 % CI 0.13 – 0.42; p=0.047). Persistent levels of CO2 more than 45 mmHg at blood gas analysis were associated to death outcome (OR 5.647; 95 % CI 0.32 – 0.53; p=0.019). N/L more than 20 is positively correlated with death, with a OR of 4.236 (95 % CI 0.28 – 0.42; p=0.0042). A state of sepsis was found to be associated with the adverse outcome (OR 8.387; 95 % CI 0.24 – 0.44; p=0.004). The multivariate analysis confirmed a positive correlation with the death outcome in a model that included N/L ratio more than 20 (OR 2.862; 95 % CI 0.02 – 0.013; p=0.005) and radiological findings of ground glass opacities (OR 3.346; 95 % CI 0.108-0.420; p=0.001). CONCLUSIONS The use of NIV in patients with acute respiratory distress syndrome (ARDS) from SARS-CoV-2 is debated. While NIV may reduce intubation rates, approximately 40% of patients developed HAP, primarily from multidrug-resistant (MDR) pathogens. This study emphasizes that SARS-CoV-2 does not increase HAP incidence but raises overall mortality. Strict environmental measures are needed to be implemented to prevent MDR infections.