System and method for transient response and accuracy enhancement for sensors with known transfer characteristics

• US 6,553,991 B1
• Filed: 01/15/1999
• Issued: 04/29/2003
• Est. Priority Date: 03/14/1997
• Status: Expired due to Term

• Current Assignee: Nellcor Puritan Bennett Incorporated (Medtronic Plc)
• Original Assignee: Nellcor Puritan Bennett Incorporated (Medtronic Plc)
• Inventors: Isaza, Fernando J.
• Primary Examiner(s): Lewis, Aaron J.
• Application Number:
  US09/231,145
• Time in Patent Office: 1,565 Days
• Field of Search: 128/204.18, 128/204.21, 128/204.23, 128/205.23, 128/202.22, 600/537, 374/169
• US Class Current: 128/204.21
• CPC Class Codes: A61M 16/024 including calculation means, e.g. using a processor
• CPC Class Codes: A61M 2016/0039 in the inspiratory circuit
• CPC Class Codes: G01F 1/6965 comprising means to store calibration data for flow signal calculation or correction
• CPC Class Codes: G01F 25/10 of flowmeters

Abstract

A parameter of interest being measured by a sensor is estimated from output response data from the sensor and the known transfer function of the sensor, allowing fast and accurate sensor data from sensors having a dynamic characteristic otherwise precluding assessment of the sensor input. A parameter of breathing gas from a ventilator is determined based upon the known transfer function and a plurality of the sensor output signals at predetermined intervals of time, to provide an estimation of the parameter of interest.

Claims

1. In a patient ventilation system for determining a dynamically changing output parameter of interest, the patient ventilation system including a temperature sensor for determining the output parameter of interest, the temperature sensor exhibiting a dynamic characteristic having a time constant, resulting in a transient performance of the temperature sensor, said temperature sensor having a known transfer function and generating temperature sensor output signals indicative of the output parameter of interest, and a flow meter for determining flow in the patient ventilation system, the flow meter generating a flow output signal, the improvement in the system comprising:

a computing device connected to the temperature sensor for receiving a plurality of said temperature sensor output signals from the temperature sensor at predetermined intervals of time, for processing said plurality of output signals, and for determining an estimate of said output parameter of interest based upon said temperature sensor output signals and said known transfer function, and for determining flow in the patient ventilation system based upon the output parameter of interest and the flow output signal; and

means for outputting an indication of the estimate of said output parameter of interest and an indication of flow in the patient ventilation system.

2. In a method for determining a dynamically changing parameter of interest in a patient ventilator by providing the patient ventilator with a temperature sensor exhibiting a dynamic characteristic having a time constant, resulting in a transient performance of the temperature sensor, said temperature sensor having a known transfer function for determining the output parameter of interest, the patient ventilator including a flow meter for measuring flow in the patient ventilator, and generating a flow output signal, the improvement in the method comprising the steps of:

receiving temperature sensor output signals from said temperature sensor;

determining an estimation of said output parameter of interest based upon said known transfer function and a plurality of said temperature sensor output signals at predetermined intervals of time;

determining flow in the patient ventilator based upon said estimation of said output parameter of interest and said flow output signal; and

outputting an indication of the estimation of said output parameter of interest and an indication of flow in the patient ventilator.

3. A system for determining a dynamically changing output parameter of interest within a patient ventilation system, the system comprising:

a temperature sensor exhibiting a dynamic characteristic having a time constant, resulting in a transient performance of the temperature sensor, said temperature sensor generating temperature sensor output signals and having a known transfer function for determining the output parameter of interest;

a flow meter for measuring flow in the patient ventilation system, and generating a flow output signal;

computing means connected to said temperature sensor for receiving a plurality of said temperature sensor output signals at predetermined intervals of time, for processing said plurality of temperature sensor output signals, and for determining an estimate of said output parameter of interest based upon said temperature sensor output signals and said known transfer function, said computing means being connected to said flow meter for receiving said flow output signal, said computing means determining flow in the patient ventilation system based upon said estimate of said output parameter of interest and said flow output signal; and

means for outputting an indication of said estimate of said output parameter of interest and an indication of flow in the patient ventilation system.

4. A method for determining a dynamically changing output parameter of interest within a patient ventilation system, the method comprising the steps of:

providing the patient ventilation system with a flow meter for measuring flow in the patient ventilation system, and generating a flow output signal;

providing the patient ventilation system with a temperature sensor exhibiting a dynamic characteristic having a time constant, resulting in a transient performance of the temperature sensor, said temperature sensor having a known transfer function;

generating temperature sensor output signals from said temperature sensor;

determining an estimation of said output parameter of interest based upon said known transfer function and a plurality of said temperature sensor output signals at predetermined intervals of time;

determining flow in the patient ventilation system based upon said estimation of said output parameter of interest and said flow output signal; and

outputting an indication of said estimation of said output parameter of interest and an indication of flow in the patient ventilation system.

5. In a system for determining flow in a ventilation flow path of a patient ventilation system based upon a dynamically changing temperature output parameter of interest in a patient ventilation system, said patient ventilation system having a source of breathing gas and said ventilation flow path delivering said breathing gas, comprising:

a hot film anemometer for measuring flow of breathing gas in the ventilation flow path and generating a flow output signal;

a temperature sensor for generating temperature sensor output signals for determining the temperature output parameter of interest of said breathing gas in said ventilation flow path, said temperature sensor exhibiting a dynamic characteristic having a time constant, resulting in a transient performance of the temperature sensor, and said temperature sensor having a known transfer function;

computing means connected to said temperature sensor for receiving said temperature sensor output signals at predetermined intervals of time, for processing a plurality of said temperature sensor output signals, and for determining an estimate of said temperature output parameter of interest of said breathing gas in said ventilation flow path based upon said temperature sensor output signals and said known transfer function, said computing means being connected to said hot film anemometer for receiving said flow output signal, said computing means determining flow in the patient ventilation system based upon said estimate of said temperature output parameter of interest and said flow output signal; and

means for outputting an indication of flow in said ventilation flow path.

6. A method for determining flow of breathing gas in a ventilation flow path of a patient ventilation system based upon a dynamically changing temperature output parameter of interest of the breathing gas in the ventilation flow path in the patient ventilation system, the steps of the method comprising:

providing a ventilator having a source of breathing gas and a ventilation flow path for delivering said breathing gas;

providing the ventilator with a hot film anemometer for measuring flow of breathing gas in the ventilation flow path and generating a flow output signal;

providing a temperature sensor exhibiting a dynamic characteristic having a time constant, resulting in a transient performance of the temperature sensor, said temperature sensor generating temperature sensor output signals and having a known transfer function for determining the temperature output parameter of interest of the breathing gas in the ventilation flow path;

determining an estimation of said temperature output parameter of interest of said breathing gas in said ventilation flow path based upon said temperature sensor output signals and said known transfer function;

determining flow in the ventilation flow path based upon said estimation of said temperature output parameter of interest and said flow output signal; and

outputting an indication of flow in said ventilation flow path.