Surgery – Respiratory method or device – Inhaled gas heated or humidified by exhaled gas
Reexamination Certificate
1998-05-21
2003-04-22
Lewis, Aaron J. (Department: 3761)
Surgery
Respiratory method or device
Inhaled gas heated or humidified by exhaled gas
C128S201250, C128S203120, C128S203260, C128S204130, C128S204170, C128S205120
Reexamination Certificate
active
06550476
ABSTRACT:
FIELD OF THE INVENTION
This invention utilized in the medical field, generally relates to an apparatus for the humidification of inspired gases and the administration of aerosolized medication in connection with mechanical ventilators, or anesthesia devices.
BACKGROUND OF THE INVENTION
Hygroscopic condensers humidifiers (HCH), heat and moisture exchangers (HME), or an artificial nose are well known in the art. These devices are routinely used for the humidification of inspired gases during mechanical ventilation.
These devices essentially work by conserving heat and moisture from the exhaled humidified gas during the exhalation phase from a patient, then recycling the heat and moisture to the subsequent inspiratory phase to humidify the dry gas from the ventilator. Recent studies have indicated, patients requiring mechanical ventilation with adequate hydration, without secretion problems, and no history of severe lung disease, can tolerate these devices for extended periods of time. Also the studies reveal, there are no increased risk of nosocomial infections with the use of these passive humidification devices, compared to heated humidification.
Due to the challenges to reduce costs in providing medical care, and as the studies have shown positive results, there is an increased acceptance and justification for the utilization of an HME.
A patient requiring mechanical ventilation with the usual method of an electronic humidification apparatus demand constant observation. For example the respiratory practitioner or nurse must assure that the reservoir of the humidifier is maintained with an adequate level of water, as well as the alarm system and heater are operating properly, and to assure a physiological proximal airway temperature.
Often the ventilator circuit must be drained from the condensation to prevent the potential drowning of a patient, and to maintain proper ventilator function. This requires often disconnecting the ventilator circuit temporarily from the patient. Another method may employ the connection of a container inline in the ventilator circuit, and a vacuum applied to remove the condensate collected in the container.
Heated wire circuits are frequently employed to reduce the amount of water condensation in the ventilator circuit. However, there is a greater cost associated with the combination of an electronic humidifier and heated wire circuit, compared to an electronic humidifier alone.
In most cases, a patient requiring mechanical ventilation will receive an aerosolized medication with a nebulizer, or metered dose inhaler (MDI). If a nebulizer is used to aerosolize a bronchodilator, the HME must be quickly removed from the ventilator circuit, and replaced with the nebulizer prefilled with a liquid medication, and “T” adaptor. After the nebulization is complete, the nebulizer and “T” adaptor are quickly disconnected, and then reattach the HME to the ventilator circuit.
If a sidestream nebulizer with “T” adaptor were connected in series in a position prior to the HME, obviously the aerosol would be filtered out, and the patient would not receive the aerosolized medication. Also, the added moisture from the aerosol would rapidly clog the HME. If the nebulizer and “T” adaptor were connected in series between the artificial airway and the HME, the patient would receive some medication, but likewise any excess aerosol would rapidly clog the HME.
The obstruction of the heat and moisture exchanging unit from the added excessive moisture will cause an increased resistance to the inspiratory gas flow, resulting in an increase work of breathing of the patient. This can have a dramatic effect on the debilitated patient, particularly during synchronous intermittent mandatory ventilation, pressure support, or spontaneous breathing with continuous positive airway pressure.
Preferably the exchange of components occurs synchronously during the brief period of time between the end of the exhalation phase, and just prior to the next inspiratory phase. The capability of the practitioner to exchange these components without interruption of ventilation, becomes increasingly more difficult with increased frequency of ventilation. If a patient is receiving continuous positive airway pressure, cessation of positive pressure occurs during the disconnection of the circuit, resulting in an intermittent drop in the intrathoracic pressure to the level of atmospheric pressure.
Obstruction of the HME device does not readily occur following a few actuations with an MDI. Therefore the HME is usually not removed prior to the use of an MDI alone. However, the HME should be removed with the combination of an MDI and spacer device, due to the added deadspace volume.
Another disadvantage of frequent disconnections of the ventilator circuit to attach a nebulizer, are the increase risk of nosocomial infections from the hospital environment, or secondary to improper hand washing technique. Moreover, the medical personnel has an increased risk of occupational hazards to the exposure of infectious airborne pathogens from a patient, such as tuberculosis, antibiotic resistant bacteria, and potential lethal viruses.
U.S. Pat. No. 5,505,568 issued to Altadonna sets forth a HUMIDITY MOISTURE EXCHANGER in which the HME having a first and second chamber, the second chamber with a pair of fluid ports. Inside the housing, is a filter or heat and moisture collecting material. To permit the uninhibited passage of aerosol from the nebulizer, the absorbent material is removed from the second chamber area, and temporarily stored within the first chamber area.
Although the device is designed to obviate the need for ventilator circuit disconnection, the device requires additional components and a nebulizer to administer an aerosol. It is unclear whether the described sealing engagement to minimize potential deadspace, could also provide an adequate seal to prevent aerosol clogging the filter, or heat and moisture collecting material when temporarily stored in the second chamber.
U.S. Pat. No. 5,546,930 issued to Wikefeldt sets forth a PATIENT CONNECTOR WITH HME, FILTER, AND NEBULIZER CONNECTION in which a Y-piece is to provide an inhalation and exhalation conduit, a patient conduit for connecting the nipple to the Y-piece, an HME disposed in the patient conduit, a nebulizer connector between the nipple and the HME, or an inhalation connector downstream to the HME for connecting the patient conduit to the nebulizer. In another embodiment a powder inhaler is also provided in connection to the nipple so that powder can be supplied to the patient.
Although Wikefeldt, has developed a method to permit the introduction of aerosols in conjunction with an HME without the interruption of mechanical ventilation, the apparatus reveals a substantial increase in the deadspace and requires several external connections of flexible tubing, and connected nebulizers. This has a disadvantage due to the increase number of connections resulting in an increased risk of potential leaks and ventilator circuit disconnection. An increase in the deadspace volume will increase the alveolar partial pressure of carbon dioxide, which could have a deleterious effect on a patient diagnosed of chronic obstructive airway disease. When an aerosolized medication is delivered by the nebulizer, a major portion of the aerosol exhaled by the patient is taken up by the HME.
While the foregoing devices are representative of the prior art, to provide an aerosolized medication in combination with an HME device, without the interruption of mechanical ventilation, which require adaptors, additional components, and nebulizers, these devices do not describe the instant invention claimed.
OBJECTS AND ADVANTAGES
Several objects and advantages of the present invention are:
(a) to provide a convenient method for the safe delivery of both humidification and aerosolization of medication with mechanical ventilators or anesthesia devices;
(b) to provide a method to maintain the continuity of a closed ventilator circuit when administering an aerosolized medication, and p
Knobbe Martens Olson & Bear LLP
Lewis Aaron J.
Weiss, Jr. Joseph F.
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