Patent ID: 7106955
Filing Date: 2006-09-12
Classification: A61M,G05D

Abstract:
1. A breathing assistance apparatus adapted to deliver humidified gas at a desired level of humidity or at a desired temperature within a conduit to a patient using open loop control comprising: a humidifier capable of humidifying said gas up to a level of humidity prior to delivery to said patient, the humidifier having an electrical input power, said level of humidity depending on said input power to said humidifier, a conduit configured to convey said humidified gas from said humidifier to a patient, a conduit heater associated with said conduit wherein gas flowing through said conduit is heated either directly or indirectly by said conduit heater, the conduit heater having an electrical input power, the level of heating depending on said input power to said conduit heater, a conduit heater power monitor providing an output indicative of the input power to said conduit heater, and a controller or processor configured or programmed to carry out the following instructions: (a) monitor said input power supplied to said conduit heater and to determine a parameter which in combination with said input power is indicative of the flow rate of gas through said conduit; (b) determine based on said parameter the required electrical power input to said humidifier to deliver gas to said patient at a level of humidity or at a temperature substantially similar to said desired level of humidity or said desired temperature; (c) supply as said input power to said humidifier a level of power substantially similar to said determined power input to said humidifier; (d) continuously monitor said parameter, and when a change in said parameter is greater than a first threshold, reverts to said instruction (a).