Dysbiosis in the oral cavity of patients undergoing invasive mechanical ventilation and receiving oral care, combined with antimicrobial photodynamic therapy.

INTERVENTION: This is a randomized controlled clinical trial in critically ill patients. Initially, a pilot study will be conducted with 6 patients (n=6) for standardization of sample collection. After calibration, samples will be collected from 30 patients for the control group and 30 patients for the experimental group (total n = 66). Sample size calculation was performed using G*Power software with a test power of 80%, significance level of 5%, effect size of 0.5, and considering a potential sample loss of 20%. Eligible patients for the study will be randomly divided into two groups. Randomization will be performed using computer software, with blocks of different sizes (2 and 4), by another professional who will remain blinded until the moment of photodynamic therapy. The control group will receive oral care according to the institution's standard operational protocol, which includes oral hygiene performed by the nursing team using a brush and/or swab and 0.12% chlorhexidine solution. The experimental group will receive the same oral care mentioned above, along with antimicrobial photodynamic therapy. Photodynamic therapy will be performed on patients in the experimental group on the 1st day after biofilm collection and every 48 hours, with the last session on day 7 of follow‐up. Methylene blue will be used as the photosensitizer at a concentration of 0.01%, with a pre‐irradiation time of 3 minutes and an irradiation time of 60 seconds per area. Two areas will be irradiated on the tongue, two on the bilateral buccal mucosa, and one on the palate, using a cluster with three LED points, each with a power of 36 mW, developed specifically for this study by the Institute of Physics of São Carlos, University of São Paulo. Biofilm samples will be collected from two different sites CONDITION: E02.760.190 Pneumonia Ventilator‐Associated; Dysbiosis; Cross Infection PRIMARY OUTCOME: We infer that patients who remain longer on mechanical ventilation, suffer dysbiosis of the oral microbiome, increasing the risks of infections. SECONDARY OUTCOME: The use of aPDT possibly modulates the dysbiotic state reducing the risk of oral and systemic complications related to the presence of microorganisms. INCLUSION CRITERIA: Critically ill patients admitted to the Intensive Care Unit; undergoing mechanical ventilation; intubated within 24 hours; and aged 18 years or older; both genders