Method and apparatus for detecting apnea

• US 4,381,788 A
• Filed: 02/27/1981
• Issued: 05/03/1983
• Est. Priority Date: 02/27/1981
• Status: Expired due to Fees

• Current Assignee: Douglas, David W.
• Original Assignee: Douglas, David W.
• Inventors: Douglas, David W.
• Primary Examiner(s): Howell, Kyle L.
• Assistant Examiner(s): Hanley, John C.
• Application Number:
  US06/238,813
• Time in Patent Office: 795 Days
• Field of Search: 128/722, 128/718, 128/724, 128/780, 128/782, 361/283, 361/291, 361/313
• US Class Current: 600/535
• CPC Class Codes: A61B 5/113 occurring during breathing
• CPC Class Codes: A61B 5/6892 Mats

Abstract

An apnea monitor having a capacitance type transducer pad providing a signal indicative of respiration. The resilient dielectric material between the capacitor plates is formed in two layers with the upper layer having a lesser spring constant to make the pad more sensitive around the periphery of the body to respond to respiratory motion while rejecting cardiovascular motion. The transduced signal is monitored and its gain is automatically adjusted to compensate for long term instability by a gain-set circuit arrangement having a time delay to assure that changes in the signal are not caused by apnea. A control voltage generated by the circuit operates the alarm without excessive time delay and is also used to provide a gain-set voltage for adjustment of the signal gain.

Claims

1. A method of monitoring a patient for apnea, said method comprising the steps of:

placing the patient on a transducer pad which functions as a capacitor having a pair of spaced apart capacitor plates;

effecting a small degree of relative movement of the capacitor plates when motion of the body occurs in the area near the center of the body of the patient, thereby providing a small change in the capacitance of the pad in response to body movement corresponding to cardiovascular motion which is concentrated near the center of the body;

effecting a larger degree of relative movement of the capacitor plates when motion of the body occurs in the peripheral area of the body of the patient, thereby providing a larger change in the capacitance of the pad in response to body movement corresponding to respiratory motion which is concentrated near the peripheral area of the body; and

sensing the larger change in the capacitance of the pad while rejecting the small change in the capacitance, whereby body motion corresponding to respiratory motion is sensed and body motion corresponding to cardiovascular motion is rejected.