High Flow Nasal Cannula

High-flow nasal cannula is a type of non-invasive respiratory support that helps patients breathe more comfortably. Because the flow is high, it can deliver more oxygen to the lungs and make breathing easier by reducing the effort needed to breathe. However, the best strategy to determine the best oxygen flow rate remains uncertain. Reducing flow rates prematurely can increase work of breathing and prolong ICU stay, while unnecessary prolongation can increase costs. Currently, evidence to guide titration is limited. Heart rate variability is the natural variation in the time between each heartbeat. Heart rate variability reflects the level of autonomic nervous system activity in response to stress. The autonomic nervous system is the part of the nervous system that automatically controls how heart rate speeds up and slows down. When heart rate variability is higher, it indicates that the system is able to adjust to changes in the body, including stress. However, when heart rate variability is low, it indicates that the system is constrained and in a state of stress. The VARIATION study is designed to characterize how heart rate variability goal of this observational study is to learn whether heart rate variability can serve as a marker of the appropriateness of high flow nasal cannula flow support during flow titration in patients with respiratory failure. The main question it aims to answer is: Does heart rate variability change before other conventional respiratory signs when there are changes in respiratory function due to inadequate flow rate? Participants already on high flow nasal cannula as part of their regular medical care will: 1. Undergo a stepwise decrease in high flow nasal cannula flow rate. 2. Be recorded continuously with electrocardiogram and electrical impedance tomography.

During sedated gastroscopy, the insertion of the fiberscope and gastric distension required to perform the examination may induce respiratory depression, airway obstruction, and decreased chest wall compliance. Patients with obesity, especially visceral fat, have poor lung and chest wall compliance, lower lung capacity and functional residual capacity, and an unbalanced ventilation-to-perfusion ratio. Thus, obese patients are at a high risk of hypoxemia. Increasing evidence supports the use of High-flow nasal cannula (HFNC) oxygenation in obese patients during sedated gastrointestinal endoscopy. Obesity, especially visceral obesity, is an established risk factor associated with all-cause mortality. Body roundness index (BRI) is a newer anthropometric measure associated with identification of high-risk individuals. Owing to the limited evidence, we designed this unblinded randomized controlled trial to assess whether HFNC, compared to standard mask oxygenation, improves oxygenation at the end of the procedure (primary endpoint) in patients with visceral obesity.

Compared with adults, children have higher metabolic needs, and the airway is more likely to collapse. Before tracheal intubation after anesthesia induction, the patient 's spontaneous breathing completely disappears. At this critical stage, the residual oxygen of the lung is consumed, resulting in hypoxemia and atelectasis. Therefore, it is necessary to explore the best oxygenation strategy during intubation. In addition, ultrasound has become a common equipment in the operating room. It has the advantages of portability, repeatability, and no radiation, and can provide strong support for the diagnosis of gastric distension.

Patients at high risk of post-operative pulmonary complications (PPC) will be screened out from gynecological tumor patients undergoing surgical treatment, and randomly assigned into the HFNC group and control group, which uses conventional nasal cannula oxygen therapy. The primary outcome is the incidence of PPC, including postoperative hypoxemia, atelectasis, pneumonia, etc. Secondary outcomes are the improvement of postoperative oxygenation, antibiotic use, length of hospital stay, adverse events related to oxygen therapy, etc.

Patients with full stomachs face a high risk of regurgitation and aspiration under general anesthesia. To minimize the time between the loss of airway protective reflexes and successful tracheal intubation, rapid sequence induction intubation is commonly used. However, these patients are particularly vulnerable to hypoxemia during anesthesia induction, especially in emergency cases. Pre-oxygenation before induction is crucial for ensuring patient safety during apnea. High-flow nasal oxygen (HFNO) therapy, which consists of an air/oxygen blender, an active humidifier, and a single heated circuit, has recently gained widespread use in intensive care units (ICUs) for managing hypoxemic respiratory failure. HFNC can deliver a constant fraction of inspired oxygen (FiO₂) from 0.21 to 1.0 at high flow rates (up to 60 L/min or higher). Its advantages include generating continuous positive airway pressure, reducing anatomical dead space, improving ventilation-perfusion matching, enhancing mucociliary clearance, and decreasing the work of breathing. Given these benefits, HFNO has the potential to improve pre-oxygenation before and during anesthesia induction in emergency surgery patients with full stomachs.