Between Early View online publication and issue publication, the authors became aware of an additional relevant reference. [23] Becker et al. reported fl ame propagation velocities for pSi impregnated with NaClO 4 on the order of 3000 m/s. In their work, the pSi was prepared by galvanic etching, and the velocity measurements were performed in a desiccator box under nitrogen at a relative humidity below 2%.
Background
With large numbers of COVID-19 patients requiring mechanical ventilation and ventilators possibly being in short supply, in extremis two patients may have to share one ventilator. Careful matching of patient ventilation requirements is necessary. However, good matching is difficult to achieve as lung characteristics can have a wide range and may vary over time. Adding flow restriction to the flow path between ventilator and patient gives the opportunity to control the airway pressure and hence flow and volume individually for each patient. This study aimed to create and validate a simple model for calculating required flow restriction.
Methods and findings
We created a simple linear resistance-compliance model, termed the BathRC model, of the ventilator tubing system and lung allowing direct calculation of the relationships between pressures, volumes, and required flow restriction. Experimental measurements were made for parameter determination and validation using a clinical ventilator connected to two test lungs. For validation, differing amounts of restriction were introduced into the ventilator circuit. The BathRC model was able to predict tidal lung volumes with a mean error of 4% (min:1.2%, max:9.3%).
Conclusion
We present a simple model validated model that can be used to estimate required flow restriction for dual patient ventilation. The BathRC model is freely available; this tool is provided to demonstrate that flow restriction can be readily estimated.
Models and data are available at DOI 10.15125/BATH-00816.
Let G = (V, E) be a graph. A set S ⊆ V is a restrained dominating set if every vertex not in S is adjacent to a vertex in S and to a vertex in V − S. The restrained domination number of G, denoted by γ r (G), is the smallest cardinality of a restrained dominating set of G. We define the restrained bondage number b r (G) of a nonempty graph G to be the minimum cardinality among all sets of edges E ⊆ E for which γ r (G − E ) > γ r (G). Sharp bounds are obtained for b r (G), and exact values are determined for several classes of graphs. Also, we show that the decision problem for b r (G) is NP-complete even for bipartite graphs.
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