Surgery – Respiratory method or device – Means for supplying respiratory gas under positive pressure
Reexamination Certificate
2001-01-18
2004-01-13
Lo, Weilun (Department: 3761)
Surgery
Respiratory method or device
Means for supplying respiratory gas under positive pressure
C128S204180
Reexamination Certificate
active
06675798
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to regulating the flow of a gas to a patient.
BACKGROUND OF THE INVENTION
Inhalation of oxygen, oxygen enriched air and a variety of other gases, vapors and liquid mists (aerosols) is a well-established treatment and well known in the art. Commonly, oxygen administration is carried out in hospital and other medical facility environments. This treatment has been extended to use in the home and other non-medical environments. Generally, at the outset, oxygen administration is carried out under professional medical supervision. In chronic or extended treatment cases, once the therapy has been established, continuous medical supervision is not required and patients use oxygen therapy outside the hospital environment, permitting them to lead active productive lives. Examples of such instances include patients suffering from chronic bronchitis, asthma, emphysema, occupational lung diseases and other lung associated conditions as well as cases involving breathing difficulty due to physical conditions, such as broken ribs and the like.
However, such long term oxygen therapy is generally carried out with a fixed prescribed flow rate, irrespective of a patient's changing needs during the course of a day. For example, a patient requires less oxygen while lying or asleep than when physically active. During the course of a day, a patient may have a change of circumstances, which would require a variation in oxygen flow rate.
A widely used primary portable supply of oxygen is a high-pressure metal cylinder. Where a patient has such a cylinder of oxygen, exhaustion of that cylinder represents a hazard especially to patients incapable of connecting another, spare cylinder. Recently, alternative oxygen generating devices have been developed. These are portable, light and may be positioned wherever the patient desires. Oxygen generators are electrically operated, draw air from the local environment and reduce the nitrogen content of the air to produce an oxygen rich mixture. There is, however, a significant potential hazard. In the event of a power failure and subsequent oxygen supply failure, it is necessary to have a back-up cylinder of oxygen, which must be manually connected to the patient's inhaler.
Within the scope of determining the blood oxygen level of a patient, generally, non-invasive blood oxygen measuring devices are preferred to invasive devices. An example of an invasive device is the so-called blood oxygen machine. However, a commonly utilized non-invasive device, called an oximeter, is used for measuring the level of oxygen in the bloodstream. This non-invasive instrument includes a fastening device, a Light Emitting Diode (LED) and a photo-diode. This device emits a signal, which is a function of the oxygen level of the bloodstream. In addition, it sends out a pulse rate signal. Alternative devices include electrochemical, paramagnetic or laser absorption detection and the quenching of luminescence from a metalloporphyrin supply. The desirable physical characteristics of such a sensor include that it be small, robust with respect to environmental perturbations, and have a fast response time.
There is a need in the art, insofar as no provision is generally made, to monitor the patient's blood oxygen level so as to give an indication of the flow rate of oxygen required to maintain a desired blood oxygen level in the patient. Furthermore, no provision is generally made to effect replacement of a failed or exhausted primary oxygen supply to the patient without having to resort to manually connecting an alternative supply.
SUMMARY OF THE INVENTION
Generally, a patient undergoing oxygen therapy is prescribed a flow rate of oxygen by a medical professional. However, in many chronically ill patients, outside of hospitals there is little or no supervision by medically qualified personnel.
The present invention largely eliminates the need for constant supervision and provides a method and apparatus for controlling an appropriate flow of oxygen, sympathetic to a patient's changing needs. The technique includes measuring the concentration of oxygen in a patient's bloodstream and comparing this measurement with a desired level of oxygen. Using this comparison, the flow of oxygen to the patient is constantly regulated to optimally maintain the blood oxygen level at the desired level. This is an ongoing process so that any change in the patient's situation and consequent change in blood oxygen level will be compensated for, by a controlled change in the oxygen flow rate.
The present invention aims to control a flow of oxygen to a patient, responsive to a metric of the oxygen level in the patient's bloodstream. The present invention makes operating an oxygen inhalation system largely independent of medical supervision and the patient less dependent on assistance. Moreover, the present invention provides a solution to the problem of failure of gas flow from the primary oxygen supply by automatically initiating a replacement flow from an auxiliary emergency supply.
According to a preferred embodiment of the present invention, there is provided a method for controlling a flow of gas from a gas supply to a patient, the method including the following steps:
One) providing a regulated flow of a predetermined gas from a gas supply to a patient so as to increase the concentration in the patient's bloodstream of a preselected dissolved substance;
Two) measuring the concentration of the preselected dissolved substance in the patient's bloodstream;
Three) producing an output signal indicative of the measured concentration; and
Four) comparing the measured concentration of the preselected dissolved substance with a desired concentration thereof, so as to determine sufficiency of the regulated flow of the predetermined gas to the patient, and adjusting the regulated flow in accordance therewith.
According to a first preferred embodiment of the present invention, there is, in response to a failure of the flow of the predetermined gas, the additional step of initiating a flow of a predetermined gas from an auxiliary gas supply, thereby to maintain a flow of gas to the patient. This step occurs in response to a failure of the step of providing a regulated flow of a predetermined gas from a gas supply to a patient.
According to a variation of the first embodiment of the present invention, the additional step of initiating a flow of gas includes the sub-step of detecting a failure of the regulated gas flow from the gas supply below a predetermined gas flow.
According to a second embodiment of the present invention, the step of comparing the measured concentration of the preselected dissolved substance with the desired concentration includes the additional step of assigning, prior to the step of measuring the concentration of the preselected dissolved substance in the patient's bloodstream, at least one of the following:
One) a maximum desired concentration of the preselected dissolved substance in the patient's bloodstream; and
Two) a minimum desired concentration of the preselected dissolved substance in the patient's bloodstream.
According to a third embodiment of the present invention, in the step of providing a regulated flow of a predetermined gas from a gas supply to a patient and the step of measuring a concentration of the preselected dissolved substance, the preselected dissolved substance is oxygen.
According to a fourth embodiment of the present invention, the step of measuring the concentration of the preselected dissolved substance in the patient's blood stream may be either invasive or non-invasive measuring.
According to a fifth embodiment of the present invention, in the step of providing a regulated flow of a predetermined gas, the predetermined gas contains oxygen.
Additionally, according to a sixth embodiment of the present invention, in the step of providing a regulated flow of a predetermined gas, the predetermined gas is substantially oxygen.
In accordance with
Tyomkin Evgeny
Tyomkin Tatyana
AutoMed - Automatic Dosage Systems, Ltd.
Lo Weilun
Mitchell Teena
Nixon & Vanderhye P.C.
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