Patient-ventilator synchronization using dual phase sensors

• US 7,055,522 B2
• Filed: 11/11/2004
• Issued: 06/06/2006
• Est. Priority Date: 09/15/1999
• Status: Expired due to Term

• Current Assignee: ResMed Pty Ltd. (ResMed Incorporated)
• Original Assignee: Resmed Limited (ResMed Incorporated)
• Inventors: Berthon-Jones, Michael
• Primary Examiner(s): Bennett, Henry
• Assistant Examiner(s): WIEKER, AMANDA FLYNN
• Application Number:
  US10/986,471
• Publication Number:
  US 20050081855A1
• Time in Patent Office: 572 Days
• Field of Search: 128/204.18, 128/204.21, 128/204.22, 128/204.23, 128/204.26, 600/529
• US Class Current: 128/204.21
• CPC Class Codes: A61M 16/00 Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes stimulating the respiratory movement by mechanical, pneumatic or electrical means, iron lungs combined with gas breathing means A61H31/00
• CPC Class Codes: A61M 16/0066 Blowers or centrifugal pumps
• CPC Class Codes: A61M 16/0069 the speed thereof being controlled by respiratory parameters, e.g. by inhalation
• CPC Class Codes: A61M 16/024 including calculation means, e.g. using a processor
• CPC Class Codes: A61M 2016/0021 with a proportional output signal, e.g. from a thermistor
• CPC Class Codes: A61M 2016/0036 in the breathing tube and used in both inspiratory and expiratory phase
• CPC Class Codes: A61M 2230/60 Muscle strain, i.e. measured on the user

Abstract

An improved ventilator which delivers ventilatory support that is synchronized with the phase of the patent'"'"'s respiratory efforts and guarantees a targeted minimum ventilation. Improved synchronization is achieved through an instantaneous respiratory phase determination process based upon measured respiratory airflow as well as measured respiratory effort using an effort sensor accessory, preferably a suprastemal notch sensor. The ventilator processes a respiratory airflow signal, a respiratory effort signal and their respective rates of change to determine a phase using standard fuzzy logic methods. A calculated pressure amplitude is adjusted based upon the calculated phase and a smooth pressure waveform template to deliver synchronized ventilation.

Claims

1. A method of providing synchronized ventilatory support to a patient comprising the steps of:

providing apparatus to deliver ventilatory support to a patient, the apparatus also measuring both respiratory airflow and respiratory effort;

determining at least one instantaneous phase of respiration of the patient at least in part from both measured respiratory airflow and respiratory effort,

calculating a desired pressure value using the determined phase and a desired ventilation pressure amplitude; and

delivering ventilation to said patient in accordance with said desired pressure value.

2. The method of claim 1 wherein said respiratory effort is sensed by a sensor selected from a group of effort sensors that are independent of a leak in airflow that may affect respiratory airflow measurement including:

(a) a suprasternal notch sensor;

(b) an esophageal pressure effort sensor; and

(c) an electromyograph.

3. The method of claim 2 wherein the phase determining step comprises evaluating fuzzy inference rules relating to a signal from said respiratory effort sensor.

4. The method of claim 3 wherein said phase determining step further comprises evaluating fuzzy inference rules relating to the rate of change of said signal from said respiratory effort sensor.

5. The method of claim 4 wherein said phase determining step further includes the sub-step of evaluating fuzzy logic inference rules relating to the measured respiratory airflow.

6. The method of claim 5 wherein said phase determining step further includes the sub-step of evaluating fuzzy logic inference rules relating to the rate of change of the measured respiratory airflow.