Surgery – Respiratory method or device – Means for supplying respiratory gas under positive pressure
Reexamination Certificate
2001-10-26
2004-04-13
Lo, Weilun (Department: 3761)
Surgery
Respiratory method or device
Means for supplying respiratory gas under positive pressure
C128S203120, C128S205110, C128S207120, C128S207170
Reexamination Certificate
active
06718980
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a therapy for clearing the blood of unwanted carbon monoxide and anaesthetic chemicals and for rapidly re-oxygenating that has had it's oxygen level depleted by environmental conditions i.e. carbon monoxide poisoning or smoke inhalation. The invention includes the means of delivering the therapy in a convenient manner whether given in-situ, in an ambulance or other emergency response vehicle, or at the hospital or other care facility, and whether administered by medical professionals or paramedical personnel. The device relates in general to pneumatic/mechanical control of respirator gas supply control devices and in particular to gas selection, automatic shut off of the carbon dioxide, purging, metering and mixing of the therapeutic gases.
BACKGROUND OF THE INVENTION
Carbon monoxide (CO) is a tasteless, colorless, odourless gas. Thus it is undetectable by potential victims. The blood prefers CO to oxygen by a ratio of 200:1. As a result, relatively small amounts of CO in the air can cause CO poisoning. CO attaches to blood forming carboxyhemoglobin, thus starving the brain and other organs and tissues for oxygen (O
2
). Carbon monoxide poisoning occurs when carboxyhemoglobin levels are high enough to impair cellular functions. Symptoms of carbon monoxide poisoning include drowsiness, nausea and possibly death. The CO poisoning rate is significant, with over 70,000 hospital visits and 10,000 deaths per year in the U.S.
The cellular oxygen starvation from CO poisoning can cause death, or long-term, non-reversible health problems (i.e. to the brain, heart or neurological system). If a CO poisoning victim does not die, the average body will clear carboxyhemoglobin at the following typical rates:
Spontaneous breathing−cleansing half-life =220 minutes; Breathing pure O
2
=40 minutes; Hyperbaric chamber=20 minutes.
While the best current therapy is placing the patient in a hyperbaric chamber, these chambers are usually unavailable (only about 700 exist world-wide) and are rarely used. Typically these chambers require a “warm-up” time of 2 hours, which largely negates their theoretical usefulness. That is, significant permanent damage may have already occurred before the treatment can be commenced.
The current therapy of choice is to administer pure O
2
. As suggested above, pure O
2
would require approximately 2 hours to clear 87.5% of the CO from the bloodstream (e.g. 40 minutes=50% of CO is eliminated; 80 minutes=25%; 120 minutes=12.5%). Breathing pure O
2
has an unfortunate side effect; it lowers the respiratory rate and reduces the exchange of gases in the lungs, thereby prolonging the tissue starvation period. Accordingly, there is a need for a device that would overcome these disadvantages.
Typical respirator gas supply control devices, particularly those used for mixing gases under pressure and feed a delivery line of a respirator, or medical device, are too large and bulky to be used in situ or in emergency vehicles. They also require the operation of a skilled, medical practitioner to properly administer. A complete system that can be used by emergency and paramedical should have a gas selection device, an automatic shut off of the carbon monoxide a purging system, metering of the gases and a mixing chamber to promote a homogeneous mixture of gases and sized for in-situ or vehicle as well as hospital emergency room use. It should be able to use a whole range of different gas storage systems for input and demand regulators and facemasks as output. It can not rely on electrical control of the gas flow and mixing as power demand for both in situ or emergency vehicle applications is already greater than is reasonable to expect. Also electrical power at fire and other emergency sites is problematical to provide and higher priority uses get first use of this power. Finally battery power is not acceptable as the system must operate every time demanded regardless of the interval between demand and maintenance of batteries is a low priority item for emergency care providers.
For example, U.S. Pat. 3,441,041 allows for either atmospheric or compressed air to be used for a breathing apparatus but the mixture device is not easily portable, and requires adjustment by a trained individual when dealing with a patient to determine if the by-pass should be opened or closed and to adjust the compressed air flow based on respiration demands and the state of the patient's health.
U.S. Pat. 4,535,797 discloses a device that uses flow to keep the by-pass open and the by-pass is required to open the gas flow valve for the first time. Should the CO
2
supply fail, the O
2
supply will shut and the patient's therapy is terminated.
U.S. Pat. 4,549,563 maintains a constant ratio between two gases, G
1
and G
2
, by keeping the pressure of both gases P
1
and P
2
constant and keeps P
1
constant at a set rate of flow through the use of a pressure limiter.
The device disclosed in U.S. Pat. 4,549,563 does not provide for automatic shut off of the CO
2
gas stream should the O
2
stream become clogged. This shortcoming would expose the patient to an asphixyant and would not revert to the previously accepted therapy. In U.S. Pat. 4,549,563 the practitioner operates the flush system described in case the patient requires pure O
2
instead of the gas mixer. Such facemasks are commercially available and are not shown in the drawings. Also the system in 4,549,563 has no means of purging, which would mean that the second patient would face an incorrect mixture or if the system selection was changed, for example from O
2
to CO
2
then the patient would have to inhale the incorrect mixture prior to receiving the correct therapeutic gases.
U.S. Pat. 4,313,436 mixes O
2
and other medical gases for patients. It requires electronic sensing to determine if the gas mixture is correct and if not then causes a pressure pulse to close the by-pass thereby allowing only pure O
2
to enter the facemask. The use of electronics that have a large demand for power, i.e. 4 sensors and an automatic controller, are not feasible for in-situ on in vehicle use where power demand is already quite high and the most frequent operational problem is dead batteries due to limited maintenance time. Also this device has up to 5 separate valves that need to be adjusted by the medical practitioner to ensure the patient is receiving the proper gas mixture depending on his state. This degree of adjustment is inimical to the use by paramedical and emergency personnel. The system in 4,313,436 lacks a means of purging and only has two selection options, no mixture or mixture. Since there is no intermediary stage the operator is not prompted to purge the system.
U.S. Pat. 4,827,965 uses a venturi nozzle to simultaneously meter and mix the two gases in proper proportions. This scheme means that pressure of the two gases varies over the flow demand regime and that the charge may be stratified. Finally the system in 4,827,965 does not have a means to shut off the CO
2
mixture thus potentially exposing the patient to an asphixyant. Nor does it allow selection of different options (i.e. O
2
only, off, mix or off). Nor does it offer a means of purging the system except by drawing off the first amount of improper mixture.
Under U.S. Pat. 5,727,545, one embodiment requires electronic sensing of two temperatures and a pressure to control the action of four flow regulators. In a second embodiment, it requires electronic sensing of two temperatures and a pressure to control the action of two flow regulators. The by-pass is driven electronically so that any failure of the electrical system would endanger the patient's life. Metering and mixing are all electronic and it has no purging means. The use of electronics that have a large demand for power are not feasible for in-situ on in vehicle use where power demand is already quite high and the most frequent operational problem is dead batteries due to limited maintenance time.
U.S. Pat. 4,5
Lo Weilun
Mendoza Michael G.
Norris McLaughlin & Marcus P.A.
Veritek NGV
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