Surgery – Respiratory method or device – Means for supplying respiratory gas under positive pressure
Patent
1998-11-16
2000-11-07
Lewis, Aaron J.
Surgery
Respiratory method or device
Means for supplying respiratory gas under positive pressure
12820423, A61M 1600
Patent
active
061421480
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a measuring transducer for the measurement of gas flow, especially for the measurement of the pressure and/or flow of a patient's respiration, as defined in the preamble of claim 1. The invention further relates to a system for the measurement of the pressure and/or flow of a patient's respiration, as defined in the preamble of claim 20.
In hospitals, during intensive care and operations, respiration apparatus must be used to take care of the patients' respiration. Unhindered flow of gases into and out of the patient's lungs is naturally of vital importance. The condition of the gas channels can be monitored both by measuring the concentrations of the exhalation gases and by measuring the flow and pressure of the gases. Especially, monitoring of the carbon dioxide content of exhalation gas is widely used as a routine in operating theaters. However, flow and pressure measurements are essential additional functions both in respect of safety and because they make it possible to calculate quantities descriptive of the mechanical operation and respiratory metabolism of the lungs.
In principle, there are many applicable types of flow transducers. However, measurements in clinical conditions involve many problems. The flow is measured from the end of a so-called incubation tube inserted into the patient's windpipe. The transducer is therefore exposed to both humidity and mucous secretions coming from the windpipe. It is clear that such soiling is likely to affect the operation of especially the commonly used turbine and hot-wire transducers. Ultrasonic transducers are better able to tolerate soiling, but they are dependent on changes of the flow profile, temperature and gas composition, requiring sophisticated compensation. Differential pressure transducers are better suited for clinical use. The flow in the tube may be laminar or turbulent. In the case of laminar flow, the pressure difference across a flow restricting element placed in the tube is directly proportional to the flow. In the case of a turbulent flow, the pressure difference depends on the square of the flow. In addition, the pressure difference depends on the square of the cross-sectional area of the flow tube. The transducers currently used are generally made of plastic, and the concentration of water forms small drops on the interior walls of the flow transducer because water has a large contact angle to a plastic surface. The problem is that the condensed water together with possible secretions gathered in it reduce the cross-sectional area of the transducer, resulting in an increase in the measured pressure difference. If the measured pressure difference is too large, this also means that the calculated flow value is too high and therefore incorrect. A transducer with a small cross-sectional area is most sensitive in this respect. In short-time use of the measuring transducer, the resulting error is generally not too large, but if the transducer is used continuously e.g. for one or more hours in humid conditions, the error in the measurement results will be considerable. One way to eliminate this problem is to heat the transducer to a temperature sufficient to prevent condensation. However, this method requires a heating element and an electric connection, so it is difficult to use in practice and a transducer with a heating element is also expensive to fabricate. Moreover, a hot element may involve a danger to the patient.
The object of the present invention is to eliminate the problems described above.
A specific object of the invention is to present an improved transducer restricting the flow of respiratory gas which is not sensitive to condensed water and the patient's mucous secretions and which is capable of reliable operation even in dirty conditions. A further object of the invention is to present a system correspondingly improved for the measurement of the pressure and/or flow of a patient's respiration.
The measuring transducer of the invention is characterized by what is presented in claim 1. The syst
REFERENCES:
patent: 3960142 (1976-06-01), Elliot et al.
patent: 4197857 (1980-04-01), Osborn
patent: 4403514 (1983-09-01), Osborn
patent: 4932269 (1990-06-01), Cammarata, III et al.
patent: 5088332 (1992-02-01), Merilainen et al.
patent: 5111827 (1992-05-01), Rantala
patent: 5134890 (1992-08-01), Abrams
patent: 5676132 (1997-10-01), Tillotson et al.
patent: 5789660 (1998-08-01), Kofoed et al.
patent: 5858514 (1999-01-01), Bowers
patent: 5913249 (1999-06-01), Weckstrom
Japan Patent Abstract No. JP62132117, dated Jun. 15, 1987 and English translation
Kleemola Antti
Weckstrom Kurt
Instrumentarium Corp.
Lewis Aaron J.
Mitchell Teena
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