Sedation Complication clinical trials

Effect of HFNO on Spontaneous Ventilation in Obese Patients During Analgo-sedation for Vitrectomy

Patients suffering from pathology of posterior eye chamber such as diabetic retinopathy, retinal detachment, traumatic eye injury, retained lens fragments, macular hole, pucker, dislocated intraocular lens after cataract surgery or vitreomacular traction are often subjected to pars plana vitrectomy (PPV). PPV is minimally invasive endo-microscopic operation usually performed in topical anesthesia combined with sub-Tenon or retrobulbar block done by surgeon, supplemented by intravenous analgo-sedation given by anesthesiologist. Continuous infusion and dose adjustment of intravenous anesthetics applied should procure moderate sedation and preservation of patients' spontaneous ventilation. However, despite carefully applied anesthetics and standard low-flow nasal oxygenation (LFNO) (5 L/min O2 via nasal catheter), inadequate spontaneous breathing can occur leading to low blood oxygen level (hypoxia). Obese patients are susceptible to hypoxia and hypercapnia (high CO2 blood level) during analgo-sedation. Respiratory instability of obese patients is often associated to their subsequent circulatory instability (heart rate and blood pressure disorders). On the other hand, high-flow nasal oxygenation (HFNO) is usually used during anesthesia induction when difficult maintenance of airway patency is expected, in intensive care units during weaning patients from mechanical respirator and in postanesthesia care units during awakening from anesthesia. It can deliver 20 to 70 L/min, up to 100% inspiratory fraction of O2 (FiO2) to patient. High oxygen/air flow produces 3-7 cmH2O of continuous pressure in patients' upper airways therefore providing better oxygenation. Oxygen/air mixture delivered by HFNO is humidified and heated, thus more comfortable to patient than dry and cold LFNO. Aim of this study is to compare effect of HFNO to LFNO during intravenously applied standardized analgo-sedation given for PPV in obese adult patients. Investigators hypothesize that obese patients, whose breathing pattern is preserved, receiving HFNO vs. LFNO during standardized analgo-sedation for PPV will be more respiratory and circulatory stable, preserving normal blood O2 and CO2 level, breathing pattern, heart rate and blood pressure.