Physiological Effects of High Flow in Adults

2021 ◽  
pp. 55-65
Author(s):  
Francesca Dalla Corte ◽  
Irene Ottaviani ◽  
Giacomo Montanari ◽  
Yu Mei Wang ◽  
Tommaso Mauri
Keyword(s):  
High Flow ◽  
Physiological Effects

scholarly journals How Much PEEP Does High Flow Deliver via Tracheostomy? A Literature Review and Benchtop Experiment

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Martin Thomas ◽  
Riddhi Joshi ◽  
Grant Cave
Keyword(s):  
Gas Exchange ◽  
Airway Pressure ◽  
Ventilatory Support ◽  
High Flow ◽  
Physiological Effects ◽  
Fluid Interface ◽  
High Flow Nasal Cannula ◽  
Inner Surface ◽  
Average Change ◽  
Significant Change

Background. High flow tracheostomy (HFT) is a commonly used weaning and humidification strategy for tracheostomised patients, but little is known as to how much PEEP or mechanical benefit it offers. Patient anatomy and device characteristics differentiate it from high flow nasal cannula and the physiological effects observed. Objectives. (1) To review the available literature on the effects of HFT on airway pressure and indices of gas exchange. (2) To quantify PEEP generated by a HFT  circuit. Methods. A randomised benchtop experiment was conducted, with a size 8 uncuffed Portex tracheostomy connected to an Optiflow™ with Airvo 2™ humidifier system. The tracheostomy tube was partially immersed in water to give rise to a column of water within the inner surface of the tube. An air fluid interface was generated with flows of 40 L/min, 50 L/min, and 60 L/min. The amount of potential PEEP (pPEEP) generated was determined by the distance the water column was pushed downward by the flow delivered. Findings. Overall 40 L/min, 50 L/min, and 60 L/min provided pPEEP of approximately 0.3 cmH2O, 0.5 cmH2O, and 0.9 cmH2O, respectively. There was a statistically significant change in pPEEP with change in flows from 40–60 L/min with an average change in pPEEP of 0.25–0.35 cmH2O per 10 L/min flow ( p value <0.01). Interpretation. HFT  can generate measurable and variable PEEP despite the open system used. The pPEEP generated with HFT is minimal despite statistically significant change with increasing flows. This pPEEP is unlikely to provide mechanical benefit in weaning patients off ventilatory support.

scholarly journals High-flow therapy: physiological effects and clinical applications

Breathe ◽  
2020 ◽  
Vol 16 (4) ◽  
pp. 200224
Author(s):  
Rebecca F. D'Cruz ◽  
Nicholas Hart ◽  
Georgios Kaltsakas
Keyword(s):  
Critical Care ◽  
Respiratory Failure ◽  
Care Setting ◽  
Clinical Applications ◽  
High Flow ◽  
Supporting Evidence ◽  
List Type ◽  
Physiological Effects ◽  
Palliative Care Setting ◽  
Respiratory Droplets

Humidified high-flow therapy (HFT) is a noninvasive respiratory therapy, typically delivered through a nasal cannula interface, which delivers a stable fraction of inspired oxygen (FIO2) at flow rates of up to 60 L·min−1. It is well-tolerated, simple to set up and ideally applied at 37°C to permit optimal humidification of inspired gas. Flow rate and FIO2 should be selected based on patients' inspiratory effort and severity of hypoxaemia. HFT yields beneficial physiological effects, including improved mucociliary clearance, enhanced dead space washout and optimisation of pulmonary mechanics. Robust evidence supports its application in the critical care setting (treatment of acute hypoxaemic respiratory failure and prevention of post-extubation respiratory failure) and emerging data supports HFT use during bronchoscopy, intubation and breaks from noninvasive ventilation or continuous positive airway pressure. There are limited data on HFT use in patients with hypercapnic respiratory failure, as an adjunct to pulmonary rehabilitation and in the palliative care setting, and further research is needed to validate the findings of small studies. The COVID-19 pandemic raises questions regarding HFT efficacy in COVID-19-related hypoxaemic respiratory failure and concerns regarding aerosolisation of respiratory droplets. Clinical trials are ongoing and healthcare professionals should implement strict precautions to mitigate the risk of nosocomial transmission.Educational aimsProvide a practical guide to HFT setup and delivery.Outline the physiological effects of HFT on the respiratory system.Describe clinical applications of HFT in adult respiratory and critical care medicine and evaluate the supporting evidence.Discuss application of HFT in COVID-19 and aerosolisation of respiratory droplets.

scholarly journals Physiological effects of high-flow oxygen in tracheostomized patients

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Daniele Natalini ◽  
Domenico L. Grieco ◽  
Maria Teresa Santantonio ◽  
Lucrezia Mincione ◽  
Flavia Toni ◽  
...  
Keyword(s):  
Respiratory Rate ◽  
Airway Pressure ◽  
Gas Flow ◽  
Oxygen Therapy ◽  
High Flow ◽  
Mean Difference ◽  
Physiological Effects ◽  
Arterial Blood ◽  
High Flow Oxygen ◽  
Tracheal Pressure

Abstract Background High-flow oxygen therapy via nasal cannula (HFOTNASAL) increases airway pressure, ameliorates oxygenation and reduces work of breathing. High-flow oxygen can be delivered through tracheostomy (HFOTTRACHEAL), but its physiological effects have not been systematically described. We conducted a cross-over study to elucidate the effects of increasing flow rates of HFOTTRACHEAL on gas exchange, respiratory rate and endotracheal pressure and to compare lower airway pressure produced by HFOTNASAL and HFOTTRACHEAL. Methods Twenty-six tracheostomized patients underwent standard oxygen therapy through a conventional heat and moisture exchanger, and then HFOTTRACHEAL through a heated humidifier, with gas flow set at 10, 30 and 50 L/min. Each step lasted 30 min; gas flow sequence during HFOTTRACHEAL was randomized. In five patients, measurements were repeated during HFOTTRACHEAL before tracheostomy decannulation and immediately after during HFOTNASAL. In each step, arterial blood gases, respiratory rate, and tracheal pressure were measured. Results During HFOTTRACHEAL, PaO2/FiO2 ratio and tracheal expiratory pressure slightly increased proportionally to gas flow. The mean [95% confidence interval] expiratory pressure raise induced by 10-L/min increase in flow was 0.2 [0.1–0.2] cmH2O (ρ = 0.77, p < 0.001). Compared to standard oxygen, HFOTTRACHEAL limited the negative inspiratory swing in tracheal pressure; at 50 L/min, but not with other settings, HFOTTRACHEAL increased mean tracheal expiratory pressure by (mean difference [95% CI]) 0.4 [0.3–0.6] cmH2O, peak tracheal expiratory pressure by 0.4 [0.2–0.6] cmH2O, improved PaO2/FiO2 ratio by 40 [8–71] mmHg, and reduced respiratory rate by 1.9 [0.3–3.6] breaths/min without PaCO2 changes. As compared to HFOTTRACHEAL, HFOTNASAL produced higher tracheal mean and peak expiratory pressure (at 50 L/min, mean difference [95% CI]: 3 [1–5] cmH2O and 4 [1–7] cmH2O, respectively). Conclusions As compared to standard oxygen, 50 L/min of HFOTTRACHEAL are needed to improve oxygenation, reduce respiratory rate and provide small degree of positive airway expiratory pressure, which, however, is significantly lower than the one produced by HFOTNASAL.

Physiological effects of titrated oxygen via nasal high-flow cannulae in COPD exacerbations: A randomized controlled cross-over trial

Respirology ◽  
2017 ◽  
Vol 22 (6) ◽  
pp. 1149-1155 ◽  
Author(s):  
Janine Pilcher ◽  
Leonie Eastlake ◽  
Michael Richards ◽  
Sharon Power ◽  
Terrianne Cripps ◽  
...  
Keyword(s):  
High Flow ◽  
Physiological Effects ◽  
Copd Exacerbations ◽  
Randomized Controlled

Anisotropic Membranes as Substrates for Sem

1976 ◽  
Vol 34 ◽  
pp. 444-445
Author(s):  
Thomas P. Turnbull ◽  
W. F. Bowers
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Flow ◽  
Polymer Chemistry ◽  
Surface Porosity ◽  
Transmission Electron ◽  
Pore Texture ◽  
Spongy Layer ◽  
Scanning Electron

Until recently the prime purposes of filters have been to produce clear filtrates or to collect particles from solution and then remove the filter medium and examine the particles by transmission electron microscopy. These filters have not had the best characteristics for scanning electron microscopy due to the size of the pores or the surface topography. Advances in polymer chemistry and membrane technology resulted in membranes whose characteristics make them versatile substrates for many scanning electron microscope applications. These polysulphone type membranes are anisotropic, consisting of a very thin (0.1 to 1.5 μm) dense skin of extremely fine, controlled pore texture upon a much thicker (50 to 250μm), spongy layer of the same polymer. Apparent pore diameters can be controlled in the range of 10 to 40 A. The high flow ultrafilters which we are describing have a surface porosity in the range of 15 to 25 angstrom units (0.0015-0.0025μm).

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