What Is Incentive Spirometry?

Forced vital capacity is 3179 ± 117ml, and female is 2314 ± 48ml. When the normal person's lung capacity is greater than 80% of the vital capacity, the flow rate increases rapidly during the forced expiratory process, and the curve rises to the highest point in vain, which is called the maximum expiratory flow rate (max. ), Easily affected by the subjective efforts of the subject, can be used as a basis for early diagnosis of small airway obstruction. Representing the maximum expiratory flow at the expiratory 75%, 50%, and 25% vital capacity, which are commonly used as indicators. Vmax: (5.46 ± 0.22) L / s V75: (5.3 ± 0.18) L / s V50: (4.1 ± 0.15) L / s V25: (2.25 ± 0.16) L / s V50 / V25: 2: 2 MFE / V: 158.4 ± 9.6

Spirometry test

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Spirometry is currently the most commonly used pulmonary ventilation test, including time vital capacity and flow volume curves. At present, most spirometers are computerized, and the time is automatically recorded by the computer. The breathing volume and flow can be measured simultaneously and instantaneously. For the measurement method, see the flow volume curve measurement.

Name

Spirometry test

category

Lung function

Forced vital capacity is 3179 ± 117ml, and female is 2314 ± 48ml. When the normal person's lung capacity is greater than 80% of the vital capacity, the flow rate increases rapidly during the forced expiratory process, and the curve rises to the highest point in vain, which is called the maximum expiratory flow rate (max. ), Easily affected by the subjective efforts of the subject, can be used as a basis for early diagnosis of small airway obstruction. Representing the maximum expiratory flow at the expiratory 75%, 50%, and 25% vital capacity, which are commonly used as indicators. Vmax: (5.46 ± 0.22) L / s V75: (5.3 ± 0.18) L / s V50: (4.1 ± 0.15) L / s V25: (2.25 ± 0.16) L / s V50 / V25: 2: 2 MFE / V: 158.4 ± 9.6

Abnormal results: (1) Time vital capacity Time vital capacity refers to the breathing volume that changes with time during forced breathing. The most commonly used clinically is forced expiratory volume (FEV), which means that the lung volume varies with Time-varying relationship. Commonly used detection indicators and definitions are as follows: Forced vital capacity (FVC): refers to the maximum expiratory volume (TLC position) with the greatest effort, the fastest speed to exhale to the full (RV position) exhaled volume. Under normal circumstances, FVC is consistent with VC. FVC when airway is obstructed Forced expiratory volume in one second (FEV1): refers to the fastest expiratory volume within 1 second after the maximum inhalation to the TLC position. FEV1 is both a volume measurement and a flow measurement, that is, the average expiratory flow measurement within 1 second, and its measurement stability and repeatability are better, which is the most important and commonly used indicator of impaired lung function. 1 second rate (FEV1 / FVC or FEV1 / VC): The ratio of FEV1 to FVC or VC. It is used to distinguish whether the decrease in FEV1 is due to a decrease in expiratory flow or expiratory volume. It is the most commonly used indicator to judge airway obstruction. Maximal mid-expiratory flow (MMEF), also known as forced mid-expiratory flow (FEF25-75%): refers to the average flow when forced expiratory 25% -75% vital capacity. The flow at low lung volume is affected by the small airway diameter, and the decrease in flow reflects the obstruction of the small airway. Those with normal FEV1, FEV1 / FVC, and airway resistance may have lower MMEF values than normal. Therefore, it can be used as a sensitive indicator for early detection of small airway diseases. Its sensitivity is higher than FEV1, but its variability is also greater. . (2) Flow-volume curve (FV curve) The time integral of the flow is the volume, otherwise the time differential of the volume is the flow. Due to the development of modern computer technology, the function of volume and flow can be calculated instantaneously, and the relationship between flow and volume can be described. Therefore, testing and display are extremely convenient. Currently, it is the most commonly used pulmonary ventilation function test item. The flow-volume curve forms a closed loop in the breathing phase, so it is also called the flow-volume loop (FV loop). F-V curve characteristics FV curve can provide flow characteristics at different lung volume levels, which is of great help for clinical diagnosis. The characteristic of maximum expiratory flow-volume curve (MEFV) is that the early expiratory flow rapidly increases to the highest value (peak expiratory flow, or maximum expiratory flow, PEF), and the peak point is about 75% of the total lung volume. Between lung total levels, its value is related to the degree of effort of the subject, that is, a forced dependence of expiratory flow at high lung volume. There is no significant relationship between expiratory flow and exertion during the middle and late phases of expiratory phase, that is, at low lung volume. This is that the expiratory flow of low lung volume is force-independent. The flow volume curve decreases slowly and uniformly as the lung volume decreases, and gradually slopes downward to the residual air level. PEF to RV position is basically in a straight line relationship. MEFV curve characteristics can be clarified by the isobaric point theory. When exhaling forcefully, due to the effect of airflow resistance, the air in the lungs exhales along the surrounding airways to the open end of the trachea, and the airway pressure gradually decreases. When the airway pressure drops to a point equal to the intrathoracic pressure, it is called equal Pressure point. According to the isobaric point theory, the airway can be divided into two sections: the smaller airway from the isobaric point to the alveolar side is called the upstream section; the larger airway from the isobaric point to the airway opening is the downstream section. In the upstream airway pressure> intrathoracic pressure, the lumen will not be compressed; in the downstream airway pressure <intrathoracic pressure, the airway is compressed and the lumen becomes smaller, but the isostatic point is in the process of forced exhalation It is not a fixed position, it reflects dynamic physiological changes. From a dynamic point of view, the alveolar elastic retraction force is the driving force for generating flow in the airway of the alveolar isobaric point, and the airway resistance determines the alveolar retraction force. It can effectively act on the length of the airway wall to keep it open (that is, the length of the upstream section). The greater the driving force and the smaller the airway resistance, the farther the isobaric point is from the alveoli. This is seen when the high lung volume is forced to exhale. The isobaric point moves to the airway. The downstream airway is supported by the tracheal cartilage ring. Uncompressed, low airway resistance. Therefore, air flow is strongly dependent at high lung volume. As the expiratory lung volume decreases, the driving force decreases and the isobaric point gradually moves toward the surrounding airway. At this time, the downstream airway is squeezed by the intrathoracic pressure and the lumen Narrowness and increased airway resistance offset the force of intrathoracic pressure on alveoli to increase expiratory flow, which is manifested as self-limiting flow, that is, the non-force dependence of expiratory flow at low lung volume. When a small airway lesion or obstructive ventilation dysfunction occurs, the airway obstruction and stenosis worsen, the isobaric point moves upstream, and there is also a significant flow limitation at the higher lung volume, so the flow volume curve is exhaled The characteristic pattern of the phase-decreasing branch recessed toward the volume axis. At this time, RV and TLC increased due to gas trapping. In the case of restrictive ventilation dysfunction, the expiratory flow of the corresponding lung volume was not affected, and the changes in the descending branch of MEFV were no different from normal (still a straight and uniform decline), only showing a decrease in lung volume. Commonly used indicators 1. Peak expiratory flow (PEF): the highest flow when forced to exhale. PEF is an important indicator of airway patency and respiratory muscle strength, and is highly linearly related to FEV1. PEF can also be measured with a miniature peak expiratory flow meter. 2. Forced expiratory flow after 25% of the vital capacity (75% of the vital capacity) instantaneous flow (forced expiratory flow after 25% of the FVC has been exhaled, FEF25%, V75): FEF25% is a reflection of the early expiratory flow indicators, the airway Its value drops significantly when blocked. 3. The instantaneous flow (FEF50%, V50) of 50% vital capacity (the remaining 50% vital capacity) of forced exhalation: FEF50% is a flow index reflecting mid-expiration, which is similar to MMEF. 4. The instantaneous flow (FEF75%, V25) of 75% of the vital capacity (the remaining 25% of the vital capacity) is forced to exhale: FEF75% is a flow index reflecting the late expiration, which is 1/2 of the MMEF. Its clinical significance is similar to FEF50% and MMEF. MMEF and FEF50% and FEF75% participate in the judgment of small airway dysfunction. If more than two of these three indicators decrease (<65% of normal expected value), it reflects airway obstruction or small airway disease. 5. Ratio of expiratory flow to inspiratory flow at half vital capacity (FEF50% / FIF50%): FEF50% / FIF50% is an important indicator of upper airway obstruction, and the normal value is <1. A ratio of> 1 indicates that there may be a chest-shaped upper airway obstruction. People to be checked: (1) Patients with severe lung diseases who need lung health examinations.

Attention during inspection: (1), pay attention to exclude leaks during the test (the most common is no tight lips, no upper nose clip or loose nose clip), glottal closure during exhalation, exhalation, double inhalation, cough And other factors leading to the impact on lung function results. (2) The extrapolated volume can be automatically calculated in most of the current pulmonary function instruments, and it is a better indicator for evaluating the force of the early burst of expiration. In some simple lung function meters, this indicator may not be displayed. (3) After the initial forced exhalation, since the expiratory flow in the middle and late phases of expiration is not dependent on the force, the subject can be instructed to keep the exhalation action only, but the body can be moderately relaxed without being overly nervous. (4) It is best to observe the time-volume curve and the flow-volume curve at the same time during the test to know in real time whether the subject's breathing meets the quality control requirements. (5) For some patients with severe airway obstruction, the expiratory time can be as long as 20 seconds and the expiratory volume plateau does not appear. At this time, the patient must be closely observed to prevent syncope or fall. Breathing can be interrupted at appropriate times. (6) If the cooperation of some subjects' breathing is not good, it will affect the test results (especially the peak flow capacity and vital capacity), which should be specified in the result report for clinical reference only. (7) Repeatability test is very helpful for the subject's quality control, but not all of the repeatability tests used meet Grade A standards. Some subjects may only have Grade C, Grade D or even F despite their best efforts. Grade, can not give up the pulmonary function test, but it must be explained in the report to remind the clinician's attention. (8) Repeaters can make time-volume curve and flow-volume curve overlay printing, which is very helpful for the repeatability evaluation. (9) Due to the intra-day variation of individuals, the measured value in the afternoon can be higher than the morning. Therefore, if longitudinal comparison (such as comparison before and after treatment for a period of time) is required, it is best to perform within the same period ± 2hr. (10). If using a breathing filter, you should know in detail whether the resistance of the filter is sufficient to affect the breathing flow. (11) The selection of normal reference values is the basis for evaluating whether the lung function is normal, and each laboratory should try to choose the normal reference value that is suitable for it (such as area, test population, detection method, etc.). This is important for correct results analysis. The National Compilation of Normal Lung Function, edited by Mu Kuijin and Professor Liu Shiwan, can be used for reference. If a reference value recommended by the European Respiratory Society (ERS) for Asians is used, an additional correction value should be considered. Not suitable for people: Subjects with high airway sensitivity may induce airway spasm when repeatedly breathing hard

(1) Preparation of testing instruments Select lung function instruments that can meet certain technical requirements, such as the American Thoracic Society (ATS) standards; When the machine is turned on every day, it needs to be calibrated / confirmed by a calibration device (recommended 3.000L) The instrument works normally (the error should be within ± 3%); BTPS correction for room temperature, room pressure, humidity, etc. (Labs with large room temperature changes during the day need to be corrected in a timely manner). (2) Standards for testing actions Instructor: Ask the subject's medical history, smoking history, recent medication status, etc., and exclude the contraindications to forced pulmonary function testing (described later). Explain the test procedures and precautions to the subjects in detail. The instructor makes demonstration demonstrations, including complete inhalation, explosive exhalation, and continuous expiration, which can cooperate with language and body movements, and strive to make the subject fully understand the detection movements. Continually prompt and encourage the subject during the test. Subject: The subject takes a seated position and sits straight without backrest, his feet are on the ground, his eyes are flat, and he avoids leaning his head or leaning down; Practice the above breathing movements and master the essentials of movement; Wrap the mouthpiece tightly with the lips to ensure no leaks and upper nose clips; Inhale completely after calm breathing, and then exhale vigorously, quickly, and completely, requiring explosive exhalation, without hesitation at the beginning, and exerting force in the middle and late periods of expiration The degree can be slightly reduced, but there is no interruption in the entire expiration process, until the expiration is complete, avoiding coughing or double inhalation. Inhale quickly and completely after expiration. The test results meet acceptable quality control standards; After a short rest (depending on the patient's situation), repeat the above measurements , , and , and complete the measurement at least 3 times, generally no more than 8 times. (3) Quality control standard Extra vol (Exp vol): the intersection point A between the extension line of the total lung length and the slope line of the maximum expiratory flow on the time volume curve and the intersection point B of the time volume curve The volume of time is the volume of gas exhaled before the zero point of the forced exhalation time (the intersection of the vertical line at point A and the time axis) (Figure 4, animation). The extrapolated volume should be <5% FVC or <0.15 l, whichever is greater. Exhalation time: 6 sec, or the expiratory phase time volume curve shows that the expiratory volume appears as a plateau and the duration is 1 sec. The flow volume curve shows: no hesitation at the beginning; PEF spikes appear quickly, there is no interruption in the entire exhalation process, no cough, smooth curve, and one go; the inspiratory phase should also do its best, a semi-circular arc, and the flow loop is closed . Repeatability: Generally, the best 2 times FVC and FEV1 variation are <5% or <0.2 L. According to the repeatability test results, it can be divided into five levels to judge: Level A: The difference between the best secondary acceptable FEV1 0.1LB level: The difference between the best secondary acceptable FEV1 0.2LC: the most The difference between the best two acceptable FEV1> 0.2LD level: only one time FEV1 meets acceptable quality control standards F level: all lung function tests do not meet acceptable quality control standards Value criteria: FVC and FEV1 The maximum value. The remaining parameters can take the parameter values on the best curve (the curve with the largest FVC + FEV1 value).

Chronic obstructive pulmonary disease, acute respiratory distress syndrome

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