Surgery – Diagnostic testing – Respiratory
Reexamination Certificate
1996-07-16
2001-11-27
Nasser, Robert L. (Department: 3736)
Surgery
Diagnostic testing
Respiratory
C600S529000
Reexamination Certificate
active
06322519
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for measuring the lung characteristics of a patient. It more particularly addresses a portable spirometer for measuring various parameters which are necessary to the diagnostic of doctors, such as the peak-flow, the maximum exhaled volume per second, etc.
The peak-flow is often measured for people who suffer from asthma, bronchitis, mucoviscidosis, or who have been lung transplanted. Indeed, especially for those suffering from asthma, this measure allows the anticipation of an asthma crisis and, during treatment, allows the dosage of medicine intake.
It is thus desirable that the patients can regularly analyze their peak-flow, chart their characteristics and communicate these to their doctor or directly use them in a way prescribed by their doctor.
2. Description of the State of the Art
A known spirometer is of mechanical type, in which the breath of a patient acts on a spring biased piston. These mechanical devices have the advantage of being small and cheap but their main drawback is that they are little reliable, inaccurate and inconstant.
To realize an electronic flowmeter, it is known to use a Venturi flow sensor. Such a sensor comprises a tube with a narrow part. When a patient blows into the tube, a pressure difference establishes on both sides of the narrow part which is substantially proportional to the flow in a certain measuring range depending on the dimensions and the shape of the narrow part. This difference is measured by a differential pressure sensor connected through conduits to regions situated on either side of the narrow part.
A specific problem in the use of a Venturi flow sensor in a spirometer is connected to the fact that the spirometer must be regularly cleaned and sterilized, eventually after each use. In particular, the development of germs coming from saliva or other expectoration of the patient should be avoided in the tube and in the conduits which arrive to the sensor. Moreover, the cleaning is not easy because of the small functional passage at the narrow part and because of unavoidable corners and angles which are difficult to reach and which accumulate dirt.
U.S. Pat. No. 5,137,026 describes a portable electronic spirometer using such a Venturi flow sensor. The tube is integral with the casing of the device. To avoid dirt from going into the conduits which arrive to the pressure sensor, particular filters are placed in these conduits where they open into the tube. These filters must be liquid-tight and permeable to air. To clean and sterilize the tube, the whole device must be plunged in an antiseptic solution. Therefore, the device must be perfectly water-tight, which increases its price substantially.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a portable electronic spirometer with no cleaning and sterilization problems.
Another object of the present invention is to provide such a spirometer which is small and easy to manipulate and put away.
These objects are achieved by removably arranging the tube such that it can be removed and put back easily.
The invention more specifically addresses a device for measuring exhaled flow comprising a measuring tube partially obstructed by a narrow part of the tube; and a differential pressure sensor coupled to the tube for measuring the pressures inside the tube on either side of the narrow part. The measuring tube is removable and comprises, at its outer surface, flexible annular seals protruding from the outer surface and located on either side of openings which are in turn located on either side of the narrow part. The measuring tube is insertable in a recess of the device, the recess having a diameter slightly greater than the external diameter of the measuring tube such that, in an abutment position of the measuring tube in the recess, the annular seals define with the recess and the external wall of the tube annular chambers communicating respectively with two passages of the recess, connected to the pressure sensor.
According to an embodiment of the invention, the recess is tapered and the external wall of the measuring tube is complementary to the recess by steps, a step transition being situated at the level of each annular seal.
According to an embodiment of the invention, the annular seals are rings placed in grooves of the measuring tube.
According to an embodiment of the invention, the recess comprises, at its end of smallest diameter, an internal shoulder for stopping and centering the end of smallest diameter of the measuring tube.
According to an embodiment of the invention, the device comprises an elongated casing whose longitudinal axis is parallel to the axis of the measuring tube.
According to an embodiment of the invention, the internal end of the measuring tube communicates with a horn for deviating the air flow in the tube towards a side.
According to an embodiment of the invention, the annular seals are flanges integral with the measuring tube.
REFERENCES:
patent: 3608546 (1971-09-01), Shinn
patent: 3922525 (1975-11-01), Kozak et al.
patent: 5137026 (1992-08-01), Waterson et al.
patent: 5361722 (1994-11-01), Murnick et al.
patent: 5547440 (1996-08-01), Rubens et al.
patent: 5564432 (1996-10-01), Thomson
patent: 0295575 (1988-12-01), None
McDermott & Will & Emery
Nasser Robert L.
Societe de Therformage et D'Injection des Plastiques-S.T.L.
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