Modifications to expiratory valves

Resistance of Heidbrink-type expiratory valves.

The minimum resistance of expiratory Heidbrink-type value has been assessed by determining the pressure decrease across the values at a flow rate of 30 litre min--1. The average resistance of 70 valves currently in clinical use was 318 Pa at that flow rate and about 44% had resistances greater than the limit of 294 Pa previously suggested. The resistances obtained in new valves were either simi...

Expiratory valves used for home devices: experimental and clinical comparison.

A bench study followed by a clinical trial were performed to evaluate the mechanical characteristics of five (commercially available) expiratory valves used for home ventilators, as well as the potential clinical impact of differences between these valves. In the in vitro study, expiratory valve resistance was evaluated under unvarying conditions, whereas dynamic behaviour was evaluated by calc...

Some Modifications to Calculate Regression Coefficients in Multiple Linear Regression

In a multiple linear regression model, there are instances where one has to update the regression parameters. In such models as new data become available, by adding one row to the design matrix, the least-squares estimates for the parameters must be updated to reflect the impact of the new data. We will modify two existing methods of calculating regression coefficients in multiple linear regres...

Peak expiratory flow. It's better to measure!

Simplified Theory Applied to Automatic Compressor Valves