Spirometry test

Spirometry is currently the most commonly used lung ventilation function test, including time vital capacity and flow volume curves. At present, most spirometers are computerized, the time is automatically recorded by the computer, and the respiratory volume and flow rate can be measured simultaneously and instantaneously. The measurement method is detailed in the flow volume curve. Attention during the examination: check out the leak during the test (most commonly without lip closure, no upper nose clip or loose nose clip), glottis closure during exhalation, expiration of breath, double inhalation, cough and other factors The effect on lung function results. Basic Information Specialist classification: Respiratory examination classification: pulmonary function test Applicable gender: whether men and women apply fasting: not fasting Analysis results: Below normal: Normal value: no Above normal: negative: Negative results are generally normal. Positive: Positive results suggest that there may be lung lesions that affect breathing. Tips: Subjects with high airway sensitivity may induce airway spasm when repeatedly breathing repeatedly. Normal value The forced vital capacity was 3179±117 ml, and the female was 2314±48 ml. When the normal lung volume is greater than 80% of the lung capacity, during the forced exhalation process, the flow rate increases rapidly, and the curve rises to the highest point in vain, called the maximum expiratory flow rate (max), which is easily affected by the subjective efforts of the subject. Can be used as a basis for early diagnosis of small airway obstruction. Represents the maximum expiratory flow at 75%, 50%, and 25% of the vital capacity, respectively, and considers the commonly used judgment indicators, which are negative for the normal 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/V2522; △ MFE / △ V158.4 ± 9.6. Clinical significance Abnormal results: 1. Time lung capacity: Time lung capacity refers to the amount of breathing gas that changes with time during forced breathing. The most common clinical use is forcedexpiratory volume (FEV), which is the relationship between lung volume and time when forced exhalation. Commonly used detection indicators and definitions are as follows: 1. Forced vital capacity (FVC): refers to the maximum inspiratory (TLC position) exhaled to the full (RV position) exhaled volume with maximum effort and speed. Under normal circumstances, FVC is consistent with VC, FVC when airway is blocked; 2. Forced expiratory volume exhaled volume (FEV1): refers to the fastest expiratory volume within 1 second after maximal inhalation to TLC. FEV1 is both the volume measurement value and the flow rate measurement value, that is, the average expiratory flow rate measurement within 1 second, and its measurement stability and repeatability are better, which is the most important and most commonly used indicator of lung function damage. 3.1 second rate (FEV1/FVC or FEV1/VC) The ratio of FEV1 to FVC or VC. The difference in FEV1 is due to the decrease in expiratory flow or expiratory volume. It is the most common indicator for judging airway obstruction. 4. Maximum mid-expiratory flow (MMEF), also known as forced expiratory mid-flow (FEF 25 ~ 75%): refers to the average flow when forced to exhale 25% ~ 75% of vital capacity. The flow rate of the low lung volume is affected by the small airway diameter, and the flow rate decline reflects the obstruction of the small airway. FEV1, FEV1/FVC and airway resistance are normal, the MMEF value can be lower than normal, therefore, it can be used as a sensitive indicator for early detection of small airway diseases, and its sensitivity is higher than that of FEV1, but the variability is also larger. . 2. Flow-volume curve (FV curve) The time integral of the flow is the volume, and conversely, 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 is traced. Therefore, testing and display are very convenient. Currently, it is the most commonly used lung ventilation function check item. The flow-volume curve forms a closed loop in the respiratory phase, so it is also called the flow-volume loop (F-Vloop). 1.FV curve characteristics: The FV curve can provide flow characteristics under different lung volume positions, which is of great help to clinical diagnosis. The maximum expiratory flow-volume curve (MEFV) is characterized by an early increase in exhaled flow to the highest value (expiratory peak flow, or maximum expiratory flow, PEF), with the peak point at approximately 75% of the total lung volume. Between the total amount of lungs, the value is related to the degree of effort of the subject, that is, the high lung volume presents a forced dependence of expiratory flow. There is no significant relationship between expiratory flow and exertion during the late phase of the expiratory phase, ie, low lung volume, which is independent of the expiratory flow of the low lung volume. The flow volume curve decreases slowly and evenly as the lung volume decreases, and gradually slopes downward to the residual gas position. The PEF to RV bits are basically in a straight line relationship. 2. Isobaric point: The MEFV curve characteristics can be clarified by the isobar point theory. When exhaling vigorously, due to the effect of airflow resistance, during the process of exhaling gas in the lungs to the open end of the trachea, the internal pressure of the airway gradually decreases. When the airway pressure drops to a point equal to the intrathoracic pressure, it is called Press point. According to the isostatic point theory, the airway can be divided into two segments: the smaller airway from the isostatic point to the alveolar side is called the upstream segment; the larger airway from the isostatic point to the airway opening is the downstream segment. In the upstream segment airway pressure> chest pressure, the lumen will not be compressed; in the downstream segment airway pressure < chest pressure, so the airway is compressed, the lumen becomes smaller, but the isostatic point is in the process of forced exhalation It is not a fixed position, it reflects the dynamic physiological changes. From a dynamic point of view, the elastic retraction force of the alveoli is the driving force for generating flow in the airway of the alveolar isostatic point, and the airway resistance determines the alveolar retractive force. It can effectively act on the airway wall to maintain a smooth length (ie the length of the upstream segment). The greater the driving force, the smaller the airway resistance, the farther the isostatic point is from the alveolar. This is seen when the high lung volume is forced to exhale, the isobaric point is moved to the airway, and the downstream airway is supported by the tracheal cartilage ring. Not compressed, airway resistance is small. Therefore, the airflow has a force dependence in the high lung volume, and the driving force decreases as the expiratory lung volume decreases, and the isostatic point gradually moves toward the surrounding airway, at which time the downstream airway is squeezed under the action of the chest pressure, and the lumen The narrow, airway resistance increases, offsetting the effect of intrathoracic pressure on the alveoli to increase expiratory flow, manifested as flow self-limiting, that is, the non-force dependence of expiratory flow under low lung volume. When small airway lesions or obstructive ventilatory dysfunction occur, airway obstruction and stenosis increase, the isostatic point moves upstream, and the flow rate is limited in the higher lung volume, thus presenting a flow volume curve exhalation. A characteristic pattern of the descending support to the volume axis depression. At this time, the gas is trapped, resulting in an increase in RV and TLC. In the case of restrictive ventilatory dysfunction, the expiratory flow rate of the corresponding lung volume was not affected, and the change of the MEFV descending branch was the same as normal (still a linear straight drop), only showing a decrease in lung capacity. 3. Common indicators: Peak expiratory flow (PEF): The highest flow rate during forced exhalation. PEF is an important indicator of airway patency and respiratory muscle strength, and is highly linearly related to FEV1. PEF can also be measured by a micro-expiratory peak flow meter. The instantaneous flow rate (forcedexpiratoryflowafter25%oftheFVChasbeenexhaled, FEF25%, V75) FEF25% of forced exhalation of 25% of vital capacity (the remaining 55% of vital capacity) is a measure of the flow rate in the early stage of exhalation, and its value is significantly decreased when the airway is blocked. The instantaneous flow rate (FEF50%, V50) FEF50% of the forced exhalation of 50% of the vital capacity (the remaining 50% of the vital capacity) is a flow index reflecting the mid-expiratory phase, which is similar to the MMEF. The instantaneous flow rate (FEF75%, V25) of 75% of the vital capacity (the remaining 25% of the vital capacity) was exhaled: FEF 75% is the flow index reflecting the late exhalation, which is 1/2 of the MMEF. Its clinical significance is similar to FEF50% and MMEF. MMEF participates in the judgment of small airway dysfunction with FEF 50% and FEF 75%. If there are more than 2 of these 3 indicators (<65% normal predicted value), it reflects airway obstruction or small airway disease. The ratio of expiratory flow to inspiratory flow (FEF50%/FIF50%) FEF50%/FIF50% is an important indicator of upper airway obstruction, with a normal value <1. This ratio > 1 suggests that there may be a chest-type upper airway obstruction. Need to check the crowd: patients with severe disease in the lungs, need a lung health checkup. Positive results may be diseases: aspiration pneumonia, emphysema, tuberculosis, pulmonary candidiasis, acute lung abscess, tin pneumoconiosis, lung injury, pulmonary edema considerations Note when checking: 1. In the test, please pay attention to the elimination of air leaks (most commonly without lip closure, no upper nose clip or loose nose clip), glottic closure when exhaling, exhalation pause, double inhalation, cough and other factors caused by the lungs The impact of functional outcomes. 2. Extrapolation volume can be automatically calculated in most current pulmonary function meters, which is a good indicator to evaluate the early burst of exhalation force. In some simple spirometers, this indicator may not be displayed. 3. After exhaling at the beginning of forced exhalation, due to the non-force dependence of exhalation flow in the middle and late exhalation, the subject can be instructed to maintain only exhalation, but the body can be moderately relaxed without being too nervous. 4. It is best to observe the time volume curve and the flow volume curve simultaneously during the test to know in real time whether the subject's breathing meets the quality control requirements. 5. Some patients with severe airway obstruction may have an expiratory time of up to 20 seconds and still have no expiratory volume platform. At this time, the patient's condition must be closely observed to prevent it from syncing or falling. Can interrupt exhalation in due course. 6. If the degree of cooperation of some subjects with forced breathing is not good, it will affect the test results (especially peak flow and vital capacity), which should be specified in the results report for clinical reference only. 7. Repeatability testing is very helpful for the quality control of the subjects, but not all of the repetitive tests used meet the A-level criteria. Some subjects may only have C, D or F grades despite their best efforts. The lung function test cannot be abandoned, but it should be stated in the report to remind the clinician. 8. Multiple testers can print overlapping time volume curves and flow volume curves, which is helpful for the evaluation of repeatability. 9. Due to the intra-day variation of the individual, the afternoon measurement value can be higher than the morning, so if longitudinal comparison is needed (such as comparison before and after treatment), it is best to perform within ±2hr of the same time period. 10. If you use a breathing filter, you should know in detail whether the resistance of the filter is sufficient to affect the respiratory flow. 11. The selection of the normal reference value is the basis for evaluating whether the lung function is normal. Each laboratory should try to select the normal reference value that is suitable for it (such as the region, the test population, the detection method, etc.). This is very important for correct result analysis. The National Compendium of Normal Lung Function, edited by Professor Mu Kuijin and Professor Liu Shizhen, can be used as a reference. If the reference value recommended by the European Respiratory Society (ERS) for Asians is used, the correction value should be considered. Inappropriate population: Subjects with high airway sensitivity may induce airway spasm when repeatedly breathing repeatedly. Inspection process Test instrument preparation: 1. Select a pulmonary function instrument that meets certain technical requirements, such as the American Thoracic Society (ATS) standard; 2. It needs to be standardized/confirmed by the scaler (3.000L recommended) when starting up every day. The instrument should work normally (the error should be within ±3%); 3. BTPS calibration for room temperature, chamber pressure, humidity, etc. (Laboratory with large room temperature changes during the day needs timely correction). Test action specification: 1. Instructor: 1 Inquire about the subject's medical history, smoking history, recent medication, etc., and exclude contraindications for forced lung function testing (described later). 2 Explain the test procedure and precautions in detail to the subject. 3 The instructor gave a demonstration, including complete inhalation, explosive exhalation, and continued continuous exhalation. It can be combined with language and body movements to ensure that the subject fully understands the detection movement. 4 Continue to prompt and encourage the subject as the subject is tested. 2. Subjects: 1 The subject takes a sitting position and sits straight without backrest, feet on the ground, binocular head-up, avoiding head over leaning or bowing down; 2 practicing the above breathing action, mastering the action essentials; 3 mouth biting With the lip tightly wrapped around the mouthpiece to ensure no air leakage, upper nose clip; 4 completely breathe after breathing, then force, fast, complete exhalation, require explosive force to exhale, no hesitation, exhale in the middle and late The degree of exertion can be slightly reduced, but there is no interruption throughout the exhalation until the exhalation is complete, coughing or double inhalation is avoided. 5 Quickly inhale to complete after exhalation. The test results meet the acceptable quality control standards; 6 after a short break (depending on the patient's condition), repeat the above 3, 4, 5 measurements, at least 3 times, usually no more than 8 times. Quality control standards: 1. Extrapolation volume (Expvol): the volume between the perpendicular line of the lung volume total extension line and the intersection line of the slope line of the maximum expiratory flow rate and the intersection point B of the time volume curve, which is the force The volume of gas exhaled before exhalation time zero (the intersection of the vertical line at point A and the time axis) (Fig. 4, animation). The extrapolated volume should be <5% FVC or <0.15l, whichever is the maximum. 2. Exhalation time: ≥ 6 sec, or the expiratory time volume curve shows the platform of expiratory volume, duration ≥ 1 sec. 3. Flow volume curve shows: no hesitation at the beginning; PEF spikes appear quickly, without interruption in the whole exhalation process, no cough, smooth curve, one-shot; inhalation should also do its best, semi-circular arc, flow ring closure. 4. Repeatability: Generally, the best 2 FVC and FEV1 variations are <5% or <0.2L. According to the results of the repeatability test, it can be divided into five levels: Class A: the difference between the best secondary acceptable FEV1 is ≤ 0.1L; Class B: the difference between the best secondary acceptable FEV1 is ≤ 0.2L; Class C: the difference between the best secondary acceptable FEV1 > 0.2L; Class D: Only one FEV1 meets acceptable quality control standards; Class F: All lung function tests do not meet acceptable quality control standards. 5. Value standard: Take the maximum value of FVC and FEV1. The remaining parameters take the parameter values ​​on the best curve (the curve with the largest FVC+FEV1 value). Not suitable for the crowd The test is a non-invasive test with no specific contraindications. Adverse reactions and risks This test is a non-invasive test and does not cause serious complications or other hazards.