Surgery – Respiratory method or device – Means for supplying respiratory gas under positive pressure
Reexamination Certificate
1999-01-22
2001-10-30
Dawson, Glenn K. (Department: 3761)
Surgery
Respiratory method or device
Means for supplying respiratory gas under positive pressure
C128S201130, C128S205290
Reexamination Certificate
active
06308706
ABSTRACT:
The invention concerns a device and a process to monitor characteristic respiration values for a ventilation system
16
or
17
.
In ventilation systems for artificial respiration of patients, it is very important to maintain heat and moisture values that largely correspond to the natural environment. Respiratory gases are usually supplied from canisters or a central supply system in which the respiratory gases are almost completely dry. This would dry out the air passages of the ventilated patient if countermeasures are not taken.
To maintain physiologically suitable heat and moisture values, prior-art heat and moisture exchangers (termed HEM) serving as treatment devices are placed in the ventilation tubing system. These absorb heat and moisture from the expired air and add them to the inspired air. The treatment device can also serve or be designed as a filter that keeps potential impurities out of the ventilation system and prevents the patient's germs from contaminating the ventilation system upon exhalation. If the flow resistance increases too much from excess impurities, the patient is forced to alter his breathing. In addition, there is the danger that the patient will not be supplied with sufficient respiratory gases. This undesirably burdens the patient. The caregivers must hence regularly check the breathing resistance in such treatment devices to avoid incidents.
In the generic French patent No. 23 04 359, there is a prior-art device to monitor characteristic respiratory values of a ventilation system with a heat and moisture exchanger. The flow resistance of the heat and moisture exchanger is used to determine the volumetric flow by pressure sensors before and after the flow resistance. In this reference, the problem is also discussed that the flow resistance of the heat and moisture exchanger changes in relation to the absorbed moisture. This change falsifies the calculation of the volumetric flow across the differential pressure of the flow resistance. To solve this problem, a change in the flow resistance is avoided. A drain is located under the heat and moisture exchanger that can remove the condensed moisture. Although in certain circumstance the change from condensed moisture from respirated air is reduced, the described measure is not able to avoid changes in the flow resistance when the heat and moisture exchanger become plugged from viscous sputum.
The invention is based on the problem of automatically detecting the characteristic breathing values with a high degree of precision and reliability using a device and process to monitor characteristic respiratory values without impairing the functioning of the respiratory system.
Using a device according to the preamble of claim
16
and a process according to the preamble of claim
17
, this problem is solved by the features in the respective characteristics.
Developments and advantageous embodiments of the invention can be found in the subclaims.
Based on the relationship: of the flow resistance R equal to the differential pressure &Dgr;p over volumetric flow V, and the relationship: of the volumetric flow V equal to volume V over time, one of the quantities can be calculated when the others are known. To obtain the flow resistance of the treatment device, the differential pressure across the treatment device and the volumetric flow must be known. The differential pressure is determined by pressure sensors before and after the treatment device. To also determine the flow resistance, another flow resistance is used as a suitable reference. Since it is also located in the ventilation system, the same volumetric flow flows through it. The volumetric flow can hence be calcuated from the differential pressure over the flow resistance serving as a reference, and the value of the reference flow resistance itself.
Accordingly, the value of the flow resistance of the treatment device can be continuously monitored, changes can be immediately determined, and an alarm can be given when a threshold is exceeded. Any other characteristic breathing value and resulting warning can be determined from the measured values by corresponding mathematical calculations. Hence caregivers only need to monitor the monitoring unit and not the ventilation system; in particular, the treatment device does not need to be monitored continuously.
The pressure sensors can detect pressure in the ventilation system with reference to the environment, or they can detect differential pressure via flow resistance. Pressure sensors that detect the pressure in reference to the environment can also detect the air passage pressure in the ventilation system. However, measuring is less complicated with pressure sensors that only detect differential pressure.
The flow resistance suitable as a reference within the ventilation system can be designed as a section of the ventilation tube system, as a diaphragm, or as a filter. When a section of the ventilation tubing system is incorporated as a reference, no additional flow resistance is necessary. However, the value of this flow resistance can easily vary when the ventilation tubing system is displaced. The other option of using a diaphragm concentrates the reference flow resistance within a short path, but the flow is largely nonlinear, and this requires special compensation. A filter has proven to be the best reference flow resistance. A filter combines the advantage of a concentrated arrangement with the advantage of linear behavior at different flow speeds.
A particularly suitable reference filter is designed as fleece which is economical to manufacture and can be reproduced with a high degree of precision.
The fleece preferably extends over a cross-section that is substantially greater than the cross-section of the ventilation tubing. The flow rate is lower than that of the ventilation tubing which prevents swirling and nonlinear flow characteristics. In addition, there is a greater capture area for impurities so that the flow resistance remains largely constant.
In one advantageous embodiment, the filter is integrated into the housing of the treatment device. This measure limits the number of potentially faulty plug connections as well as the length and weight of the ventilation device, and there is less dead space in the ventilation system to reduce undesirable reinhalation of exhaled gases.
Connecting channels for the pressure sensors preferably terminate in areas of the treatment device and the flow resistance suitable as a reference in the ventilation system in which comparatively low flow speeds predominate. A change in the pressure and hence falsification of the measured values by the Venturi effect is avoided.
In one development, the connecting channels for the pressure sensors in the housing of the treatment device lead to a common connection arrangement. This protects the connecting channels that can be compactly connected to the pressure sensors from the connection arrangement.
Furthermore, the ventilation tubing system between the treatment device and ventilation device can be divided into a separate inhalation tube and exhalation tube that are joined directly before the treatment device.
A particularly advantageous ventilation tubing system has coaxial inhalation and exhalation tubes between the treatment device and ventilation device. This exploits the advantage of separate tubes without having two external tubes. In addition, this embodiment allows the exchange of heat.
In another development, a single or common plug connection is created for the connection of the junction of the inhalation tube and the exhalation tube to the treatment device, and the connection of the tubes joined with the pressure sensors to the connection arrangement in the treatment device. The tubes connected to the pressure sensors can run along the ventilation tubing system or integrated in it. This substantially reduces the time spent for setting up and taking apart the ventilation system. The common connection is also more reliable and sturdy than several separate connections at different locations. In addi
Cornelius-Lorenz Karl Siegfried
Lammers Léon
Zuchner Klaus
Collard & Roe, PC.
Dawson Glenn K.
LandOfFree
Device and process for monitoring the respiration parameters... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Device and process for monitoring the respiration parameters..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Device and process for monitoring the respiration parameters... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2602139