Surgery – Truss – Pad
Patent
1995-01-26
1996-10-08
Cohen, Lee S.
Surgery
Truss
Pad
128724, 7320419, 7386103, A61B 5087
Patent
active
055621015
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to spirometers, and more particularly to portable spirometers incorporating microprocessor controlled data collection devices, including non-heated ceramic flow sensors and temperature sensors for establishing a temperature correction factor for data obtained from the flow sensor.
BACKGROUND ART
Workers exposed to irritating dusts and fumes have been known to exhibit changes in lung function throughout a work shift to which they are assigned. Standard spirometry data collected before and after the work shift may detect a change in lung function from the beginning to the end of a work shift. However, it is more important to track changes in lung function and capacity on a substantially real-time, periodic basis, whether throughout the work shift or over the course of an entire day (or days).
Similarly, asthmatics may experience randomly occurring attacks. While lung function is adversely affected during the attack, lung function may return to normal thereafter. For these individuals, spirometric data collected during an attack is a more accurate representation of the nature of the attack and is thus more desirable to obtain than data indicative of lung function only at the beginning and end of an attack.
Portable, or hand held, prior art spirometric devices are commercially available. Such devices are known in the art. The known devices operate as follows.
Volume spirometers provide the simplest approach to measurement of spirometric parameters. Volume spirometers are essentially large cylindrical chambers including displaceable pistons. A test subject forces air into the chamber by performing a forced vital capacity (FVC) maneuver. The piston displacement corresponds to the volume of air being expired. Although accurate, these devices are large and bulky.
To keep the size and weight of a spirometric device to a minimum, it is known to measure flow instead of volume. Thus, in a flow-spirometer a flow sensor outputs a flow signal indicative of detected air flow thereacross. The desired volume data is then determined by mathematical integration of the flow signal. An advantage of such an approach is that flow spirometers are inherently smaller than volume spirometers. However, although implementable by a smaller device, the flow-sensing method of obtaining spirometric data is known to be less accurate and more sensitive to errors than the volume based method.
The volume of gas exhaled into both volume and flow-based spirometric devices is initially at 37 degrees C. and rapidly cools to ambient temperature. This cooling to ATPS (Atmospheric Temperature Pressure Saturated) causes a contraction of the gas from the volume occupied at BTPS (Body Temperature Pressure Saturated) in the subject's lungs. The spirometric volume measurement must therefore be multiplied by a BTPS correction factor to obtain the volume value at body temperature.
Portable flow type spirometric systems fall into one of two categories: (1) peak flow meters and (2) pneumotach systems.
Peak flow meters are very simple mechanical devices consisting of a mouthpiece and an indicator gauge. When the subject performs a FVC maneuver, the force of the expired air moves an indicating marker along a calibrated dial allowing peak flow to be read. If such a device is used without the aid of an administering technician, it is the subject's responsibility to perform the maneuver with sufficient effort, read the graduated scale correctly, and record the value along with the time of day. Peak flow is the only information that can be obtained from this type of device.
Portable pneumotach systems comprise a flow sensing pneumotach which generates an electrical flow signal proportional to flow. The flow signal is sampled periodically by a microprocessor, which then evaluates and stores the data.
However, because of lack of resolution in the electronic analog-to-digital converter (ADC) device which converts the analog flow signal to digital form usable by the microprocessor, there result deficiencies in accuracy of the
REFERENCES:
patent: 5038773 (1991-08-01), Norlien et al.
patent: 5277196 (1994-01-01), Hankinson et al.
patent: 5347843 (1994-09-01), Orr et al.
Ebeling Thomas R.
Hankinson John L.
Viola Joseph O.
Cohen Lee S.
The United States of America as represented by the Secretary of
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