Influence of HFNO on Spontaneous Breathing Support in Patients of Different ASA Risk During Moderate Multimodal Analgo-sedation for Pars Plana Vitrectomy

Pars plana vitrectomy is minimally invasive endoscopic procedure which is usually performed in moderate analgo-sedation given by anesthesiologist combined with topical anesthesia and regional eye anesthesia (retrobulbar or SubTenon block) performed by a surgeon. Intravenously applied anesthetics can often lead to slower breathing rate or cessation of breathing which introduces risk of low blood oxygen level despite careful adjustment of anesthetics' dose and application of standard low-flow nasal oxygenation (LFNO). Respiratory instability is often accompanied by circulatory instability manifested by disturbances of heart rate and blood pressure. LFNO provides maximally 40% inspired fraction of oxygen and can cause discomfort of a patient due to coldness and dryness of inspired gas. On the other hand, high-flow nasal oxygenation (HFNO) can bring up to 100% of inspired oxygen fraction to patient, providing noninvasive pressure support of 3-7 cmH2O in patients' upper airway which ensures better oxygenation especially in higher anesthesia risk patients. Because of carrying warmed and humidified air/oxygen mixture via soft nasal cannula, HFNO is better tolerated by patients. In this trial investigators will compare effect of HFNO to LFNO during intravenously applied standardized analgo-sedation given for vitrectomy in normal weight patients of low and high anesthesia risk. Investigators hypothesize that normal weight patients of low and high anesthesia risk, whose breathing pattern is preserved, receiving HFNO vs. LFNO during standardized analgo-sedation for vitrectomy will be more respiratory stable using equal FiO2, preserving normal blood O2 and CO2 level, breathing pattern, heart rate and blood pressure.