JP2752557B2 - Simplification of analysis method for ventilatory index - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a simplified method for analyzing a ventilation index for evaluating a ventilation function of a lung using a flow rate curve.

[0002]

2. Description of the Related Art There has been no analysis method for quantitatively evaluating a maximum flow rate curve (abbreviated MEFV) of exhalation, which is called a flow volume curve. In particular, the area of the flow rate curve is proportional to the work of the lungs and inversely proportional to the resistance of the airways. Therefore, by quantifying this area, the ventilation function of the lungs can be quantitatively evaluated. In addition, by drawing a mechanical time constant obtained from a unit air volume from a maximum expiratory flow position (MEFV position) to a maximum expiratory position (RV position) and a flow rate difference, quantitative evaluation can be performed almost continuously. Yes, ventilatory analysis is possible.

[0003]

However, conventionally, there has been no analysis method for calculating the area of the flow rate curve with high accuracy, which makes it difficult to improve the accuracy of the evaluation of the lung function test. There is a problem that there is.

[0004] An object of the present invention is to provide a simplification of a ventilation dynamic analysis method capable of calculating the area of a flow rate curve and a mechanical time constant with high accuracy in order to solve the above-mentioned problems. is there.

[0005]

According to the present invention, a plurality of sample points are determined by sampling a flow rate curve at predetermined intervals, and then the area of each divided region located between the sample points is calculated. Then, by adding the areas of all the divided areas, calculating the area of the flow rate air volume curve, further calculating the mechanical time constant of all the divided areas (unit air volume ÷ flow rate difference), mechanical time constant This is a method for analyzing ventilatory work characterized by evaluating the unevenness of the ventilation.

Further, the present invention is characterized in that the air flow pressure required per unit work is calculated by dividing the flow rate by the area of the flow rate air volume curve.

[0007]

[0008]

According to the present invention, a flow rate curve is sampled at a predetermined volume interval and a plurality of sample points are determined. It is possible to apply mathematical calculations.
Furthermore, after calculating the area of each divided area located between each sample point, by adding the areas of all the divided areas, it is possible to calculate the area of the flow rate curve with high accuracy and in a short time. It becomes possible. In addition, RV from MEFV position
By calculating and drawing the mechanical time constant between each sample point up to the order, quantitative evaluation can be performed almost continuously, and ventilatory analysis can be performed. By paying attention to the unevenness of the mechanical time constant, for example, diagnosis of a pulmonary obstructive disease or pulmonary fibrosis can be facilitated.

Further, by dividing the flow rate by the area of the flow rate flow curve to calculate the airway pressure required per unit work, it is possible to obtain a parameter effective for evaluating the ventilation function of the lung. it can.

[0010]

[0011]

FIG. 1 is a graph showing one example of a flow rate air volume curve. When the subject calls out as quickly as possible with as much effort as possible, the flow rate of expiration F (liter / second) is plotted on the vertical axis, and the volume V (liter) is plotted on the horizontal axis. During this period, the flow rate F sharply rises and reaches a peak, and the maximum flow rate F at this time is defined as PEFR. The flow rate curve gradually decreases to RV at which the flow rate F becomes 0 after the flow rate P,
The curve between them is commonly called the descending leg.

As an example of an apparatus used to obtain such a flow rate curve, there is a flow rate measuring apparatus called a spirometer, and FIG. 4 is a block diagram showing an electrical configuration of the spirometer. Subject has tube 2 in mouth
When calling with the addition of 1, expiration is sent to the flow meter 22,
The flow rate of the exhaled air is measured over time, and the measured data is input to a processing circuit 23 such as a microcomputer.

The processing circuit 23 performs a numerical calculation process of the measured data, stores it in the memory 24, and displays a numerical value or a graph of the measured data on a screen 26 of a display device 25 such as a CRT (cathode ray tube). On the other hand, instead of the data sent from the flow meter 23, the processing circuit 23
It is also possible to take in the numerical data of the flow rate curve drawn in FIG.

Hereinafter, a method for analyzing ventilatory work according to the present invention will be described with reference to a flowchart showing the operation of the spirometer in FIG. First, step a1
From step a2, the processing circuit 2
3, the flow rate data sent from the flow meter is measured with the passage of time, and stored in the memory 24 in step a3 while associating the measured flow rate with the air volume. Next, in step a4, the area of the flow rate air volume curve is calculated.

FIG. 2 is a graph illustrating a method for analyzing ventilatory work according to one embodiment of the present invention. The flow rate air volume curve of FIG. 1 obtained as described above is converted to a predetermined air volume interval d.
For example, after sampling every 10 milliliters to determine a plurality of sample points Qi (where i is a natural number), each divided region Ri located between each sample point Qi is determined.
(Where i is a natural number) is calculated.

For example, the sampling points Qi and Q
The area of the divided region Ri between i and i + 1 is the sample point Qi
Is the lower side, the flow rate Fi + 1 at the sample point Qi + 1 is the upper side, and the predetermined air volume interval d is the height of the trapezoidal area. Next, the area of the flow rate airflow curve can be obtained by adding the areas of all the divided regions Ri. At this time, the area of the correction term is added by the trapezoidal processing equation shown in the following equation (1). Set the number of sample points to n
After all,

[0017]

(Equation 1)

Next, in step a5, a mechanical time constant of the flow rate curve is calculated.

FIG. 3 is a graph for explaining the calculation and drawing of the mechanical time constant. When calculating the mechanical time constant of each divided region Ri located between each sample point Qi, a unit air volume of 10 milliliters is calculated using the flow rate F0 of the sample point P (PEFR position) and the flow rate F1 of the first sample point Q1. Difference (F0-
F1) to calculate a mechanical time constant T1. In the same manner, the mechanical time constant Tn up to the RV position is calculated, and smoothing is performed by the moving average method for drawing. The scale of the mechanical time constant is expressed as a common logarithmic scale.

Next, in step a6, the ventilation function of the lungs of the subject is evaluated. The flow rate curve represents the relationship between the flow rate F and the flow rate V. By combining three parameters including the airway pressure P as another parameter, clinically important information is grasped. it can. The flow rate F is obtained by time-differentiating the air volume V.

The compliance C representing the hardness of the lung satisfies the relationship of the following equation (2).

C = V / P (2) The airway resistance R, which represents the ease of gas flow in the airway, satisfies the following equation (3).

R = P / F (3) Accordingly, when P is eliminated from the relationship of Expressions (2) and (3) and the slope of the flow rate air volume curve is obtained, the relationship of Expression (4) below is established. I do.

F / V = 1 / (C · R) (4) From this, the slope F / V of the flow rate curve reflects the compliance C and the airway resistance R, and this C × R
Is called a time constant (T). That is, the slope of the flow rate air volume curve becomes gentler as the time constant increases, and the slope becomes steeper as the time constant decreases. Thus, in general, in the case of pulmonary obstructive disease, the airway resistance R increases, so that the slope of the flow volume curve gradually decreases, while in the case of pulmonary fibrosis, the compliance C decreases. It can be understood that the slope of the flow rate curve becomes gradually steep.

Next, as for the area S of the flow rate curve, the relationship of the following equation (5) is obtained, where W is the work load of the lung.

S = F × V = W / R (5) This means that the area S of the flow rate curve is proportional to the work W of the lung and inversely proportional to the airway resistance R. When the workload W of the lung is constant, the area S decreases as the airway resistance R increases. It is also understood that when the work amount W of the lung is increased by training the respiratory muscle strength of the lung, the area S increases.

Next, when the flow rate F is divided by the area S, from the equations (3) and (5), F / S = F × R / W = F × P / (F × W) = P / W 6) Thus, the airway pressure P / W required per unit work can be calculated. By using this parameter, the smaller the value, the higher the airway resistance R (2) the greater the restriction of the lungs (3) It is possible to determine that the subject is obese, etc. Suggest quantification parameters.

[0028]

As described in detail above, according to the present invention, the area of the flow rate curve can be calculated with high accuracy and in a short time, so that the lung function of the subject can be accurately and quickly determined. Can be evaluated. Further, by calculating mechanical time constants (unit air volume / flow rate difference) of all divided areas and evaluating unevenness of the mechanical time constants, for example, diagnosis of lung obstructive disease, pulmonary fibrosis, etc. Becomes easier. Also,
By calculating the necessary airway pressure per unit work load of the lung, an effective parameter for evaluating the ventilation function of the lung can be obtained, and the lung function of the subject can be quickly evaluated.

[Brief description of the drawings]

FIG. 1 is a graph showing an example of a flow rate curve.

FIG. 2 is a graph illustrating a method for analyzing ventilatory work according to one embodiment of the present invention.

FIG. 3 is a graph illustrating calculation and drawing of a mechanical time constant according to an embodiment of the present invention.

FIG. 4 is a block diagram showing an electrical configuration of an example of a spirometer for obtaining a flow rate curve.

FIG. 5 is a flowchart showing the operation of the spirometer of FIG. 4;

[Explanation of symbols]

 21 tube 22 flow meter 23 processing circuit 24 memory 25 display device 26 screen 27 recording paper 28 reading device

Claims (2)

(57) [Claims] 1. A flow rate air volume curve is sampled at predetermined air volume intervals to determine a plurality of sample points, and then the area of each divided region located between each sample point is calculated, and the area of all the divided regions is calculated. To calculate the area of the flow rate air flow curve, further calculate the mechanical time constant of all divided regions (unit air flow ÷ flow rate difference), and evaluate the unevenness of the mechanical time constant. A method for analyzing ventilatory work characterized by the following. 2. The method for analyzing ventilatory work according to claim 1, wherein the airflow pressure required per unit work is calculated by dividing the flow rate by the area of the flow rate curve.