US5485847A
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Pulse oximeter using a virtual trigger for heart rate synchronization
Assignee: Nellcor Puritan Bennett LLC
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Filing: 1993-10-08
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Granted: 1996-01-23
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Expires: 2013-10-08
Abstract
Abstract The present invention provides an improved method and apparatus for more accurately calculating and measuring vital information such as oxygen saturation and pulse rate when an ECG signal is not available. Instead of using an ECG R-wave as a trigger to overlay optical pulses, a virtual trigger is generated based on the heart rate and used to overlay optical pulse data. The optical information from a number of periods is added together, with the beginning of each period being determined by the issuance of the virtual trigger. In this way, the maximum and minimum of the optical signal should be lined up with each other in each period and added together to give a cumulative maximum and minimum. This enables precise identification of the maximum and minimum of the signal, and thus allows calculation of the oxygen saturation at that point.
Inventors
- 👤 Clark R. Baker, Jr.
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 13:59
CPC Classifications
A; A61; A61B; A61B5/00; A61B5/145; A61B5/1455; A61B5/14551; A61B5/72; A61B5/7203; A61B5/7207; A61B5/7235; A61B5/7239
Claims Analysis
Total Claims: 33
Claim 1
Independent Claim
72 words
An apparatus comprising: means for generating a first signal from a periodic physical activity; means for generating a second signal having a first frequency corresponding to said periodic physical activity; means for generating a virtual trigger having said first frequency, said virtual trigger being generated independent of any feature of said second signal other than said first frequency; and means for processing said first signal in periods defined by said virtual trigger.
Claim 2
Independent Claim
72 words
An apparatus comprising: means for generating a first signal from a periodic physical activity; means for generating a second signal having a first frequency corresponding to said periodic physical activity; means for generating a virtual trigger having said first frequency, said virtual trigger being generated independent of any feature of said second signal other than said first frequency; and means for processing said first signal in periods defined by said virtual trigger.
Claim 3
Dependent Claim
34 words
The apparatus of claim 1 wherein said means for generating a first signal is a pulse oximeter signal generator and said means for generating a second signal is a heart rate signal input circuit.
Claim 4
Dependent Claim
19 words
The apparatus of claim 2 wherein said heart rate signal input circuit is a heart rate frequency input circuit.
Claim 5
Dependent Claim
34 words
The apparatus of claim 2 wherein said heart rate signal is a repetitive signal, and further comprising means for converting said repetitive signal into a representation of said first frequency of said heart rate.
Claim 6
Dependent Claim
26 words
The apparatus of claim 2 further comprising means for obtaining said heart rate signal from a different site on a patient than said pulse oximeter signal.
Claim 7
Dependent Claim
26 words
The apparatus of claim 1 wherein said means for processing includes means for enhancing periodic information in said first signal from a plurality of said periods.
Claim 8
Dependent Claim
92 words
A pulse oximeter comprising: oximeter means for generating an oximeter signal corresponding to an absorption of light in a blood flow of a patient; means for receiving a heart rate signal having a first frequency corresponding to a heart rate of said patient; means for generating a virtual trigger having said first frequency, said virtual trigger being generated independent of any feature of a waveform corresponding to said heart rate of said patient other than said first frequency; and means for processing said oximeter signal in periods defined by said virtual trigger.
Claim 9
Dependent Claim
92 words
A pulse oximeter comprising: oximeter means for generating an oximeter signal corresponding to an absorption of light in a blood flow of a patient; means for receiving a heart rate signal having a first frequency corresponding to a heart rate of said patient; means for generating a virtual trigger having said first frequency, said virtual trigger being generated independent of any feature of a waveform corresponding to said heart rate of said patient other than said first frequency; and means for processing said oximeter signal in periods defined by said virtual trigger.
Claim 10
Dependent Claim
20 words
The oximeter of claim 7 wherein said means for processing includes means for enhancing periodic information in said oximeter signal.
Claim 11
Dependent Claim
22 words
The oximeter of claim 7 wherein said means for processing includes means for determining an oxygen saturation of hemoglobin in arterial blood.
Claim 12
Dependent Claim
19 words
The oximeter of claim 7 wherein said light comprises means for generating at least two multiplexed wavelengths of light.
Claim 13
Dependent Claim
26 words
The oximeter of claim 7 wherein said means for generating a virtual trigger includes a processing circuit for executing a software routine stored in a memory.
Claim 14
Dependent Claim
22 words
The oximeter of claim 7 further comprising: means for digitizing said oximeter signal; and a memory for storing the digitized oximeter signal.
Claim 15
Dependent Claim
26 words
The oximeter of claim 7 further comprising means for generating said heart rate signal by one of doppler ultrasound, blood pressure, impedance imaging or acoustic detection.
Claim 16
Independent Claim
67 words
A method comprising the steps of: generating a first signal from a periodic physical activity; receiving a second signal having a first frequency corresponding to said periodic physical activity; generating a virtual trigger having said first frequency, said virtual trigger being generated independent of any feature of said second signal other than said first frequency; and processing said first signal in periods defined by said virtual trigger.
Claim 17
Independent Claim
67 words
A method comprising the steps of: generating a first signal from a periodic physical activity; receiving a second signal having a first frequency corresponding to said periodic physical activity; generating a virtual trigger having said first frequency, said virtual trigger being generated independent of any feature of said second signal other than said first frequency; and processing said first signal in periods defined by said virtual trigger.
Claim 18
Dependent Claim
33 words
The method of claim 14 wherein said step of generating a first signal comprises generating a pulse oximeter signal and said step of receiving a second signal comprises receiving a heart rate signal.
Claim 19
Dependent Claim
26 words
The method of claim 15 wherein said step of receiving a heart rate signal comprises the step of receiving a representation of a heart rate frequency.
Claim 20
Dependent Claim
31 words
The method of claim 15 wherein said heart rate signal is a periodic signal, and further comprising the step of determining from said periodic signal the frequency of said heart rate.
Claim 21
Dependent Claim
27 words
The method of claim 15 further comprising the step of obtaining said heart rate signal from a different site on a patient than said pulse oximeter signal.
Claim 22
Dependent Claim
28 words
The method of claim 14 wherein said step of processing further comprises the step of enhancing periodic information in said first signal from a plurality of said periods.
Claim 23
Independent Claim
87 words
A method of operating a pulse oximeter comprising the steps of: generating an oximeter signal corresponding to an absorption of light in a blood flow of a patient; receiving a heart rate signal having a frequency corresponding to the heart rate of said patient; generating a virtual trigger having said frequency, said virtual trigger being generated independent of any feature of a waveform corresponding to said heart rate of said patient other than said frequency; and processing said oximeter signal in periods defined by said virtual trigger.
Claim 24
Independent Claim
87 words
A method of operating a pulse oximeter comprising the steps of: generating an oximeter signal corresponding to an absorption of light in a blood flow of a patient; receiving a heart rate signal having a frequency corresponding to the heart rate of said patient; generating a virtual trigger having said frequency, said virtual trigger being generated independent of any feature of a waveform corresponding to said heart rate of said patient other than said frequency; and processing said oximeter signal in periods defined by said virtual trigger.
Claim 25
Dependent Claim
22 words
The method of claim 20 wherein said step of processing further comprises the step of enhancing periodic information in said oximeter signal.
Claim 26
Dependent Claim
24 words
The method of claim 20 wherein said step of processing further comprises the step of determining an oxygen saturation of hemoglobin in arterial blood.
Claim 27
Dependent Claim
20 words
The method of claim 20 further comprising the steps of: generating light of at least two wavelengths; multiplexing said light.
Claim 28
Dependent Claim
26 words
The method of claim 20 wherein said step of generating a virtual trigger further comprises the step of executing a software routine stored in a memory.
Claim 29
Dependent Claim
23 words
The method of claim 20 further comprising the steps of: digitizing said oximeter signal; and storing the digitized oximeter signal in a memory.
Claim 30
Dependent Claim
27 words
The method of claim 20 further comprising the step of generating said heart rate signal by one of doppler ultrasound, blood pressure, impedance imaging or acoustic detection.
Claim 31
Dependent Claim
188 words
A pulse oximeter comprising: a photodetector for generating an oximeter signal corresponding to an absorption of light in a blood flow of a patient; a heart rate frequency generator providing a heart rate frequency; a sampling circuit producing digital samples of said oximeter signal for a plurality of periods; and a processing circuit for generating a virtual trigger having a frequency equal to said heart rate frequency, said virtual trigger being independent of any feature of a waveform corresponding to a heart rate other than a frequency of said heart rate, said virtual trigger defining said plurality of periods, said processing circuit including first means for averaging samples in said plurality of periods, second means for inhibiting generation of a virtual trigger based on heart rate frequencies greater than a first predetermined frequency and less than a second predetermined frequency, third means for inhibiting generation of said virtual trigger based on a heart rate frequency that varies at more than a predetermined rate, and fourth means for determining a maximum and a minimum value of said oximeter signal in said periods, including examining all samples in each period.
Claim 32
Dependent Claim
188 words
A pulse oximeter comprising: a photodetector for generating an oximeter signal corresponding to an absorption of light in a blood flow of a patient; a heart rate frequency generator providing a heart rate frequency; a sampling circuit producing digital samples of said oximeter signal for a plurality of periods; and a processing circuit for generating a virtual trigger having a frequency equal to said heart rate frequency, said virtual trigger being independent of any feature of a waveform corresponding to a heart rate other than a frequency of said heart rate, said virtual trigger defining said plurality of periods, said processing circuit including first means for averaging samples in said plurality of periods, second means for inhibiting generation of a virtual trigger based on heart rate frequencies greater than a first predetermined frequency and less than a second predetermined frequency, third means for inhibiting generation of said virtual trigger based on a heart rate frequency that varies at more than a predetermined rate, and fourth means for determining a maximum and a minimum value of said oximeter signal in said periods, including examining all samples in each period.
Claim 33
Dependent Claim
37 words
The pulse oximeter of claim 27 wherein said second means comprises means for inhibiting generation of said virtual trigger based on said heart rate frequency varying more often than every 5 periods of said heart rate frequency.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1999-01-22 | 1999-07-24 | 2000-01-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-01-22 | 2003-07-24 | 2004-01-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-01-22 | 2007-07-24 | 2008-01-23 | $7700.00 | Window Closed / Lapsed |