Surgery – Diagnostic testing – Measuring or detecting nonradioactive constituent of body...
Reexamination Certificate
2000-12-12
2003-01-28
Douglas, Steven O. (Department: 3736)
Surgery
Diagnostic testing
Measuring or detecting nonradioactive constituent of body...
C600S322000
Reexamination Certificate
active
06512938
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
(Not Applicable)
STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT
(Not Applicable)
BACKGROUND OF THE INVENTION
The present invention relates generally to oxygen delivery systems and more particularly to a closed loop system and method for automatically delivering fractionally inspired oxygen (FiO
2
).
Very low birth weight infants often present with episodes of hypoxemia. These episodes are detected by arterial oxygen saturation monitoring by pulse oximetry (SpO
2
) and are usually assisted with a transient increase in the fraction of inspired oxygen (FiO
2
).
Given the rapid onset and frequency at which most of these episodes of hypoxemia occur, maintaining SpO
2
within a normal range by manual FiO
2
adjustment during each episode is a difficult and time-consuming task. Nurses and respiratory therapists respond to high/low SpO
2
alarms. Under routine clinical conditions, the response time is variable and the FiO
2
adjustment is not well defined. This exposes the infants to periods of hypoxemia and hyperoxemia which may increase the risk of neonatal chronic lung disease and retinopathy of prematurity.
Thus, a need exists for a system that can automatically adjust FiO
2
. Prior art systems exist which automatically adjusts FiO
2
. Such systems have had positive results. However, existing systems fail to respond to rapid SpO
2
changes and require manual intervention. Thus, a need exists for an automated system for adjusting FiO
2
which will respond to rapid SpO
2
changes. The system should not require manual intervention, but should allow for manual intervention, if desired. The system should also allow for gradually weaning the FiO
2
as soon as an episode begins to resolve.
BRIEF SUMMARY OF THE INVENTION
In accordance with the present invention, a system is provided for delivering fractionally inspired oxygen (FiO
2
) to a patient. The system includes a device, such as a pulse oximeter, for obtaining an arterial hemoglobin oxygen saturation signal (SpO
2
). An algorithm uses the SpO
2
to determine the appropriate FiO
2
to deliver to the patient. The algorithm adjusts the FiO
2
level of an air-oxygen mixer of an oxygen delivery device, such as a mechanical ventilator.
In accordance with other aspects of the invention, SpO
2
levels, including a target (normoxemia) range, are defined. SpO
2
values above the normoxemia range are considered to be hyperoxemic and values below the normoxemia range are considered to be hypoxemic.
In accordance with further aspects of the invention, a determination is made as to whether the SpO
2
signal is a valid signal. If the SpO
2
signal is not a valid signal, the FiO
2
to be delivered to the patient is determined based on a backup value. If the SpO
2
signal is a valid signal and closed loop mode is not enabled, the FiO
2
to be delivered to the patient is determined based on a backup value. If the signal is valid and closed loop mode is enabled, the FiO
2
to be delivered to the patient is determined based on the current SpO
2
and the trend. The trend is determined by calculating a slope using previous SpO
2
values. The determined FiO
2
is then delivered to the patient, for example, using a ventilator or an air-oxygen gas mixer.
In accordance with still further aspects of the invention, a user interface is provided. The user interface displays status information. The user interface also displays alerts. The user interface can also be used to view and modify user settings/parameters.
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1999 Abstract Form from 1999 ALA/ATS International Conference (2 pages) with hard copy of Power Point presentation (22 pages) presented at American Thoracic Society-American Lung Association meeting in Apr. of 1999 in San Diego California and at the Society of Pediatric Research—American Academy of Pediatric meeting in May of 1999 in San Francisco, California. Abstract and documents apply to both meetings.
Bancalari Eduardo H.
Claure Nelson R.
Douglas Steven O.
Huynh Khoa D.
Stetina Brunda Garred & Brucker
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