System and method of obtaining measuring characteristic correction factors for respiratory flow measuring device using static pressure difference

• US 20030171887A1
• Filed: 12/23/2002
• Published: 09/11/2003
• Est. Priority Date: 01/09/2002
• Status: Active Grant

• Current Assignee: Chungbuk National University Industry Academic Cooperation Foundation (Chungbuk National University)
• Original Assignee: Hyun Sik Kim, Kyoung A. Kim, Un Jong Cha
• Inventors: Kim, Kyoung A., Kim, Hyun Sik, Cha, Un Jong
• Granted Patent: US 6,778,927 B2
• Time in Patent Office: Days
• US Class Current: 702/100
• CPC Class Codes: A61B 2560/0228 using calibration standards
• CPC Class Codes: A61B 5/087 Measuring breath flow
• CPC Class Codes: G01F 1/50 Correcting or compensating means
• CPC Class Codes: G01F 25/11 using a seal ball or piston in a test loop

Abstract

The present invention relates to a system (1) for obtaining measuring characteristic correction factors for a respiratory flow measuring device (50) using a differential pressure difference. The system (1) has a 3L syringe (10), a detecting unit (20), an A/D converter (30) and a computer (40). The 3L syringe (10) is connected to a respiratory tube of the respiratory flow measuring device (50) through a duct line. The detecting unit (20) detects volume variation within the syringe (10) and outputs the detected result as a voltage signal. The A/D converter (30) converts a volume variation signal, detected as the voltage signal by the detecting unit (20), and a differential pressure variation signal, detected as a voltage signal by a differential pressure sensor (54) through a signal extracting circuit (56) into digital signals. The computer (40) calculates measuring characteristic correction factors using the digital signals.

Claims

1. A system for obtaining measuring characteristic correction factors for a respiratory flow measuring device using a static pressure difference, comprising:

a syringe connected to a respiratory tube of the respiratory flow measuring device through a duct line;

a detecting unit for detecting volume variation within the syringe and outputting the detected result as a voltage signal;

an analog/digital (A/D) converter for converting analog signals including a volume variation signal detected as the voltage signal by the detecting unit and a differential pressure variation signal detected as a voltage signal by a differential pressure sensor connected to the respiratory flow sensor of the respiratory flow measuring device through a signal extraction circuit into digital signals; and

a computer for obtaining measuring characteristic correction factors using the digital signals outputted from the A/D converter.

2. The measuring characteristic correction factors obtaining system according to claim 1, wherein said detecting unit comprises:

a sensing bar connected to an end portion of a piston handle of the syringe for reciprocating in parallel with a piston of the syringe; and

a linear resistor for converting position variation of the piston into a voltage signal by coming into contact with the sensing bar,

wherein a voltage is applied to the linear resistor.

3. A method of obtaining measuring characteristic correction factors required for respiratory flow measurement using a measuring characteristic correction factor obtaining system, the system having a syringe connected to a respiratory tube of a respiratory flow measuring device through a duct line, a detecting unit for detecting volume variation within the syringe and outputting the detected result as a voltage signal, an analog/digital (A/D) converter connected to the detecting unit and a computer for collecting information converted by the A/D converter to obtain measuring characteristic correction factors for a respiratory flow measuring device, comprising the steps of:

converting analog signals including a volume variation signal outputted from the detecting unit and a differential pressure variation signal detected by a differential pressure sensor of the respiratory flow measuring device as a voltage signal into digital signals; and

calculating characteristic coefficients R₀ and R₁ of a first equation by applying an instantaneous flow value F(t) obtained by differentiating the converted volume variation signal V(t) and the converted differential pressure variation signal Δ

P(t) to a second equation,

$\begin{array}{cc}\begin{array}{c}\mathrm{\Delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>P=<br><br>R<br><br>\left(F\right)·<br><br>F\\ =<br><br>\left(R_0+R_1<br><br>F\right)·<br><br>F\\ =<br><br>R_0<br><br>F+R_1<br><br>F^2\end{array}& \left[\mathrm{first}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{equation}\right]\end{array}$y_k=R₀+R₁·

x_k 

 

[second equation],

where yk=∫

Δ

P_k(t)dt/3, xk=∫

F_k²(t)dt/3, and k is a stroke number.

4. The measuring characteristic correction factor obtaining method according to claim 3, further comprising the steps of drawing up a histogram according to strokes using differential pressure variation signal information accumulated in a manual reciprocation experiment of the syringe to calculate a volume measurement value after calculating the measuring characteristic coefficients R₀ and R₁, obtaining the ratio S_k of an actual volume value to the volume measurement value, and calculating a correction coefficient gi for correcting the volume measurement value according to respiratory flow values by applying the ratio S_k to the following equation.