Medical monitor with failure protection

• US 5,792,068 A
• Filed: 11/24/1993
• Issued: 08/11/1998
• Est. Priority Date: 06/23/1992
• Status: Expired due to Fees

• Current Assignee: Nellcor Puritan Bennett LLC (Medtronic Plc)
• Original Assignee: EdenTec Corporation (Medtronic Plc)
• Inventors: Bowman, Bruce R., Stasz, Peter
• Primary Examiner(s): PEFFLEY, MICHAEL F
• Application Number:
  US08/157,737
• Time in Patent Office: 1,721 Days
• Field of Search: 128/716-723, 128/901, 607/42, 606/32-34
• US Class Current: 600/536
• CPC Class Codes: A61B 2560/0276 Determining malfunction
• CPC Class Codes: A61B 5/0535 Impedance plethysmography for measuring blood flow A61B5/0295
• CPC Class Codes: A61B 5/0809 by impedance pneumography
• CPC Class Codes: A61B 5/113 occurring during breathing

Abstract

An apparatus for and method of monitoring respiration of a patient using impedance changes of the body to indicate respiration events. The impedance changes are measured by applying a carrier signal across the thorax of the patient. The carrier is periodically interrupted to produce a quiet period. A first level detector assumes the presence of EMI if the signal present during the quiet period exceeds a predetermined threshold. A second level detector senses the presence of substantial high frequency EMI. At initial power up, a third level detector checks for presence of signal before the carrier drive is applied. A fourth test circuit checks for the hang up of the differential amplification circuit.

Claims

1. An apparatus comprises:

a. monitoring means for monitoring respiration of a patient, said monitoring means comprising;

i. generating means for generating a carrier signal;

ii. applying means coupled to said generating means for applying said carrier signal across the thorax of said patient;

iii. measuring means coupled to said applying means for measuring changes in said carrier signal as applied across said thorax of said patient;

b. sensing means responsively coupled to said monitoring means for sensing the presence of non-physiologically induced electromagnetic interference which may render said monitoring means inaccurate, said sensing means comprising;

i. interrupting means for interrupting said applying means during a quiet period; and

ii. determining means for determining the presence of a substantial non-physiologically induced electromagnetic interference during said quiet period.

2. An apparatus according to claim 1 wherein said interrupting means is coupled to said monitoring means to interrupt said monitoring means during said quiet period.

3. An apparatus according to claim 2 further comprising an alarm for notifying an operator whenever said determining means determines said presence of said substantial non-physiologically induced electromagnetic interference during said quiet period.

4. An apparatus according to claim 2 wherein said interrupting means comprises a down counter coupled to said generating means for counting cycles of said carrier signal.

5. An apparatus according to claim 4 wherein said determining means further comprises a level detector.

6. An apparatus according to claims 1, 2, 3, 4 or 5 wherein said monitoring means further comprises means for determining the presence of a predetermined minimum amplitude of high frequency non-physiologically induced electromagnetic interference.

7. An apparatus according to claim 6 wherein said monitoring means further comprises means for determining the presence of a component failure.