[Analysis of International Standard ISO 80601-2-90:2021 for High-flow Respiratory Therapy Equipment]

The international standard ISO 80601-2-90:2021 specifies basic safety and essential performance requirements, including risks associated with oxygen, flow accuracy, oxygen concentration accuracy, humidification output performance, and corresponding test methods for high-flow respiratory therapy equipment. This study focuses on the key points in ISO 80601-2-90:2021 and the key problems in the test evaluation. This study also briefly introduces the relationship between ISO 80601-2-90:2021 and other standards, and explains the countermeasures that stakeholders should take.

Microfluidic Passive Valve with Ultra-Low Threshold Pressure for High-Throughput Liquid Delivery

The microvalve for accurate flow control under low fluidic pressure is vital in cost-effective and miniaturized microfluidic devices. This paper proposes a novel microfluidic passive valve comprising of a liquid chamber, an elastic membrane, and an ellipsoidal control chamber, which actualizes a high flow rate control under an ultra-low threshold pressure. A prototype of the microvalve was fabricated by 3D printing and UV laser-cutting technologies and was tested under static and time-dependent pressure conditions. The prototype microvalve showed a nearly constant flow rate of 4.03 mL/min, with a variation of ~4.22% under the inlet liquid pressures varied from 6 kPa to 12 kPa. In addition, the microvalve could stabilize the flow rate of liquid under the time-varying sinusoidal pressures or the square wave pressures. To validate the functionality of the microvalve, the prototype microvalve was applied in a gas-driven flow system which employed an air blower or human mouth blowing as the low-cost gas source. The microvalve was demonstrated to successfully regulate the steady flow delivery in the system under the low driving pressures produced by the above gas sources. We believe that this new microfluidic passive valve will be suitable for controlling fluid flow in portable microfluidic devices or systems of wider applications.

Evaluation of the effect of two active warming and humidifying high-flow oxygen therapy systems in patients with tracheotomy

The present study evaluated the effect of two active warming and humidifying high-flow oxygen therapy systems in patients with tracheotomy, in order to provide a basis for selecting the method of humidification oxygen therapy for tracheotomy. A total of 78 patients with tracheotomy, who underwent surgery between July 2017 and December 2017, were randomly divided into an observation group (39 patients) and a control group (39 patients). Patients in the observation group were treated with artificial airway high-flow humidification oxygen therapy in a closed suction system. Patients in the control group were treated using a respiratory humidification therapy device. Changes of sputum viscosity, pulmonary infection, arterial oxygen partial pressure (PaO₂), arterial blood carbon dioxide partial pressure (PaCO₂) and arterial oxygen saturation (SaO₂) were observed at 0, 48 and 96 h, and 7 days following oxygen therapy. The sputum viscosity and lung infection in the observation group were lower than those in the control group at 48, 96 h and 7 days following oxygen therapy, and the PaO₂ and SaO₂ were higher in the observation group than in the control group, which was statistically significant (P<0.05). However, there was no statistically significant difference (P>0.05) in PaCO₂ between the two groups. In conclusion, the artificial airway high-flow humidification oxygen therapy closed suction system was considered more suitable for long-term oxygen therapy of tracheotomy patients than the respiratory humidification therapy device. It can improve airway humidification and oxygen levels at lower equipment and consumable costs. The effects of treatment aim to reduce lung infections, which have clinical implications to a certain extent.

Laboratory comparison of new high flow rate respirable size-selective sampler

A newly developed high flow rate respirable size-selective cyclone sampler (GK4.162-also known as the Respirable Air Sampling Cyclone Aluminum Large (RASCAL)) was calibrated to determine its optimum operating flow rate. The Health and Safety Laboratory in the United Kingdom and two laboratories from the National Institute for Occupational Safety and Health in the United States conducted experiments using two different methods: (1) polydisperse aerosol and time-of-flight direct reading instrument (Aerodynamic Particle Sizer (APS)) and (2) monodisperse aerosol and APS. The measured performance data for the cyclone was assessed against the international respirable convention using the bias map approach. Although the GK4.162 cyclone was tested using different aerosols and detection methods, the results from the three laboratories were generally similar. The recommended flow rate based on the agreement of results from the laboratories was 9.0 L/min.

Performance of High Flow Rate Personal Respirable Samplers When Challenged with Mineral Aerosols of Different Particle Size Distributions

It is thought that the performance of respirable samplers may vary when exposed to dust aerosols with different particle sizes and wind speeds. This study investigated the performance of the GK 4.16 (RASCAL), GK 2.69, PPI 8, and FSP 10, high flow rate personal samplers when exposed to aerosols of mineral dust in a wind tunnel at two different wind speeds (1 and 2 m s(-1)) and orientations (towards and side-on to the source of emission). The mass median aerodynamic diameter of four aerosolized test dusts ranged from 8 to 25 µm with geometric standard deviations from 1.6 to 2 µm. The performance of each sampler type was compared with that of the SIMPEDS (Higgins-Dewell design) sampler. There was slight evidence to suggest that the performance of the FSP 10 is affected by the direction of the inlet relative to the air flow, although this was not significant when most respirable dust concentrations were compared, possibly due to the variability of paired dust concentration results. The GK 2.69, RASCAL, and PPI 8 samplers had similar performances, although the results when side-on to the emission source were generally slightly lower than the SIMPEDS. Despite slight differences between respirable dust concentrations the respirable crystalline silica values were not significantly different from the SIMPEDS. The GK family of cyclones obtained most precise results and more closely matched the SIMPEDS. A comparison with dust concentration results from previous calm air chamber studies (where wind speeds were < 0.4 m s(-1)) found that the relative performance between samplers was similar to those observed in this work indicating consistent performance relative to the SIMPEDS in both calm and moving air.

4D UTE flow: a phase-contrast MRI technique for assessment and visualization of stenotic flows

PURPOSE

Inaccuracy of conventional four-dimensional (4D) flow MR imaging in the presence of random unsteady and turbulent blood flow distal to a narrowing has been an important challenge. Previous investigations have revealed that shorter echo times (TE) decrease the errors, leading to more accurate flow assessments.

METHODS

In this study, as part of a 4D flow acquisition, an Ultra-Short TE (UTE) method was adopted. UTE works based on a center-out radial k-space trajectory that inherently has a short TE. By employing free induction decay sampling starting from read-out gradient ramp-up, and by combining the refocusing lobe of the slice select gradient with the bipolar flow encoding gradient, TEs of ≈1 msec may be achieved.

RESULTS

Both steady and pulsatile flow regimes, and in each case a range of Reynolds numbers, were studied in an in-vitro model. Flow assessment at low and medium flow rates demonstrated a good agreement between 4D UTE and conventional 4D flow techniques. However, 4D UTE flow significantly outperformed conventional 4D flow, at high flow rates for both steady and pulsatile flow regimes. Feasibility of the method in one patient with Aortic Stenosis was also demonstrated.

CONCLUSION

For both steady and pulsatile high flow rates, the measured flow distal to the stenotic narrowing using conventional 4D flow revealed more than 20% error compared to the ground-truth flow. This error was reduced to less than 5% using the 4D UTE flow technique.