Ventilatory assistance using an external effort sensor

• US 7,100,609 B2
• Filed: 06/16/2004
• Issued: 09/05/2006
• Est. Priority Date: 09/15/1999
• Status: Active Grant

• Current Assignee: ResMed Pty Ltd. (ResMed Incorporated)
• Original Assignee: Resmed Limited (ResMed Incorporated)
• Inventors: Malouf, Gordon Joseph, Berthon-Jones, Michael
• Primary Examiner(s): Lewis, Aaron J.
• Application Number:
  US10/868,925
• Publication Number:
  US 20040221847A1
• Time in Patent Office: 811 Days
• Field of Search: 128/200.24, 128/204.18, 128/204.21, 128/204.23
• US Class Current: 128/204.23
• CPC Class Codes: A61M 16/0069 the speed thereof being controlled by respiratory parameters, e.g. by inhalation
• CPC Class Codes: A61M 16/026 specially adapted for predicting, e.g. for determining an information representative of a flow limitation during a ventilation cycle by using a root square technique or a regression analysis
• CPC Class Codes: A61M 2016/0024 with an on-off output signal, e.g. from a switch
• CPC Class Codes: A61M 2230/60 Muscle strain, i.e. measured on the user
• CPC Class Codes: A61M 2230/63 Motion, e.g. physical activity

Abstract

The ventilator of the invention uses a respiratory effort sensor that does not rely on respiratory airflow or pressure for synchronization, such as a device that measures movement of the suprasternal notch in response to respiratory efforts. This makes the ventilator relatively immune to leaks. Furthermore, the mask pressure may be modulated so as to servo-control the respiratory effort signal to be zero. Because effort is servo-controlled to be near zero, it is not necessary for the effort signal to be either linear or calibrated, but merely monotonic on effort. Similarly, it is possible to achieve near 100% assistance without having to know or estimate the resistance and compliance of the patient'"'"'s respiratory system, as in those systems that provide proportional assist ventilation.

Claims

1. A method for controlling a mechanical ventilator comprising the steps of:

providing a subject with breathable gas at controllable pressure;

deriving a signal that is a monotonic function of the subject'"'"'s respiratory effort and that exhibits no discontinuities, said signal being derived from other than respiratory airflow and the pressure of said breathable gas provided to said subject; and

adjusting said controllable pressure in accordance with said derived signal,

wherein the controllable pressure is adjusted by a servo-controller that operates to servo-control the derived signal to be zero.

2. A mechanical ventilator comprising:

a source of breathable gas at a controllable pressure;

a transducer for deriving a signal that is a monotonic function of a subject'"'"'s respiratory effort and that exhibits no discontinuities, said transducer deriving said signal from other than respiratory airflow and said controllable pressure; and

a controller that adjusts said controllable pressure in accordance with said derived signal,

wherein said controller adjusts the pressure by servo-controlling the derived signal to be zero.