Surgery – Respiratory method or device – Face mask covering a breathing passage
Reexamination Certificate
1999-12-21
2002-02-26
Weiss, John G. (Department: 3761)
Surgery
Respiratory method or device
Face mask covering a breathing passage
C128S206240
Reexamination Certificate
active
06349725
ABSTRACT:
BACKGROUND OF THE INVENTION
1. The Field of the Invention
The present invention relates generally to anesthetic gas delivery devices. More particularly, embodiments of the present invention relate to an improved anesthesia mask for effective and reliable administration of anesthetic gases to animals.
2. The Prior State of the Art
It is generally acknowledged that administration of anesthetic to animals prior to and during surgery provides a variety of benefits, both to the animal and to the surgeon. In particular, the typical anesthetic sequence produces three desired results or effects in the animal. These three effects generally include: first, narcosis (animal is rendered unconscious); second, analgesia (the animal is rendered insensitive to pain) and suppression of reflexes; and third, muscle relaxation. Clearly, narcosis and analgesia provide a significant benefit to the animal since, as a result of these anesthetic effects, the animal suffers no pain and is unaware of the surgery taking place. Narcosis is important to the surgeon as well, since it allows the surgeon to further prepare the animal for surgery without harm to either the animal or the surgeon. Further, suppression of reflexes and muscle relaxation of the animal is important to the surgeon since it is obviously undesirable to have the animal's muscles and limbs flexing and/or moving while the surgeon is attempting to perform a surgical procedure.
Generally, the first effect, narcosis, is produced via intravenous administration of anesthetic. The effects of analgesia and reflex suppression are required in order to prepare the animal for intubation (i.e., placement of an endotracheal tube in the animal) and are typically achieved by using a temporary means to briefly force anesthetic gas into the animal's lungs and thereby place the animal in a deep state of unconsciousness. Upon achievement of analgesia and reflex suppression, the animal is then intubated for the remainder of the procedure. The final anesthetic effect of muscle relaxation is then achieved, and thereafter sustained, by connecting the endotracheal tube to a breathing circuit supplying the pressurized gaseous anesthetic.
While this anesthetic sequence is widely used and accepted, there are aspects of the associated equipment that remain problematic. One significant problem area concerns conventional masks used to introduce an anesthetic gas into the animal's lungs to achieve analgesia and reflex suppression. Intubation and the related equipment present another source of problems.
Turning first to the anesthesia masks, significant problems exist with conventional masks which have yet to be satisfactorily resolved. The major, overarching problem is that there is no known anesthesia mask that is specifically designed for use with animals, particularly dogs and other animals with muzzles or similar facial anatomy. As a necessary consequence, veterinarians have been forced to resort to a variety of incomplete and unsatisfactory solutions. Typically, veterinarians have taken one of two different approaches.
Some veterinarians simply use an anesthesia mask designed for humans. Obviously, a mask that fits a human well is clearly unsuited for use with canine anatomy. Accordingly, it is difficult, if not impossible, to adequately seal a human anesthesia mask around the muzzle of a dog. Further, because of the significant differences between canine and human anatomy, it is virtually impossible to encompass both the nose and mouth of a dog with an anesthesia mask designed for use by humans. Improperly shaped and sized anesthesia masks permit anesthetic to escape and thus it is difficult, if not impossible, for the anesthetist to determine if the proper volume of anesthetic is being delivered to the animal at the proper rate. This is clearly problematic because an improperly or inadequately anesthetized animal may compromise the surgeon's ability to perform the procedure. Likewise, the animal could suffer injury and possibly death if it is not properly anesthetized.
In an attempt to overcome the problems attending inadequately shaped and fitted anesthesia masks, anesthetists typically hold the mask in place in order to ensure the adequate flow and effective delivery of anesthetic that are required to induce a deep sleep in the animal. Generally, anesthetists are able to use this method effectively for only about ten minutes. Thus, surgical procedures lasting longer than ten minutes typically require intubation of the animal. As discussed in greater detail below, intubation introduces an additional set of problems, not the least of which are the logistics and expense involved with intubation.
Other veterinarians have moved a step further and attempted, with limited success, to modify human anesthesia masks to accommodate canine anatomy. While these modified anesthesia masks arguably represent an improvement over unmodified ones, problems remain. First, both time and expense are incurred in modifying human anesthesia masks to fit animals. Further, the functionality achieved by such modifications is modest at best. The surgeon or assistant may still have to hold the mask in place in order that the desired anesthetic effect can be achieved. Finally, the modified anesthesia mask is typically only suited for use with animals of the same size and anatomy as the one for which the mask was originally modified. Thus, while the modified mask may be somewhat effective for the particular animal for which it was modified, it is typically of limited utility where other animals are concerned.
In addition to modifying human anesthesia masks for use with animals, veterinarians have been forced to employ a variety of other primitive and generally ineffective equipment. Some of the other types of equipment currently in use by veterinarians include modified plastic containers, and anesthesia chambers constructed from modified fish tanks.
Another problem with conventional masks is that the animal's mouth needs to be allowed to open so that the tongue can move to prevent the animal from choking. At least one other problem with known masks is that they are typically ill-suited to accommodate the instrumentation necessary to monitor the vital signs of the animal when the animal is in the deep sleep typical of the final step of the anesthetic sequence. This is problematic because vital sign feedback is critically important during the procedure. For example, one vital sign or parameter of particular interest is the oxygen content of the blood of the animal. Oxygen content monitoring, or oximetry, provides valuable feedback on the effectiveness of the anesthetic gas and provides early warnings of possible complications that may arise during the procedure. Finally, oxygen content monitoring provides direct measurement of the material condition of the respiratory system of the animal. One way of monitoring the vital signs of the animal is to attach a monitor to the tongue of the animal.
As suggested above, intubation is another problem area where anesthetizing animals is concerned. One of the difficulties with the use of endotracheal tubes concerns the resistance of the breathing circuit to which the animal is connected during surgery. It is generally acknowledged that friction between a flowing fluid (which broadly encompasses both liquids and gases) and the pipe or tube through which it moves, resists fluid flow and tends to decrease the velocity of the fluid as the fluid travels down the tube. It follows that the overall loss in velocity increases with the length of the tube. Further, it is well known that the volume of gas delivered through a tube of a given size is directly proportional to the velocity of the gas, so that a relatively lower velocity corresponds to a relatively lower gas delivery rate. In view of the foregoing discussion, it is clear that the addition of an endotracheal tube to the breathing circuit increases the resistance of the circuit and tends to diminish the rate at which anesthetic gas is delivered. Thus, an intubated animal has to wor
Perkins D. H.
Perkins Ray H.
Perkins Ryan C.
Genesis Medical Technologies, LLC
Mitchell Teena
Weiss John G.
Workman & Nydegger & Seeley
LandOfFree
Anesthesia mask for animals does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Anesthesia mask for animals, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Anesthesia mask for animals will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2960419