GLOBAL and SIMPLE SPIROMETRY: cost, normal values and interpretation

What is simple and global spirometry

There spirometry is a fundamental investigation technique in the field of pulmonology, used for numerous functions. Spirometry is one of the most important respiratory function tests and allows, in fact, to detect some parameters related to the respiratory function of the subject who performs it, which in turn can have a value diagnostic is prognostic, as well as of monitoring of the therapeutic efficacy and for the evaluation of the degree of disability.

Essentially, spirometry is a test that involves the rating of the ability to exhale a certain volume of air as a function of time, by performing maneuvers respiratory through a tube connected to the spirometer. The latter is a machine capable of detecting and calculating some parameters necessary for the characterization of any respiratory pathology of the subject.

In the simple spirometry exam, two values are evaluated: VEMS (or FEV1), i.e. the maximum expiratory volume in one second, and the CVF (or FVC), i.e. the forced vital capacity. These volumes are two parameters that are automatically calculated by the spirometer during the execution of one maneuver respiratory which provides a first inspiration maximal (inhale until no more air can be introduced) followed by one exhalation maximal (exhale all the air until you can no longer).

In spirometry global, in addition to the two values mentioned above, the determination of two further parameters is also envisaged: CPT (total lung capacity) e Dlco (alveolar-capillary diffusion of CO). The total lung capacity expresses the amount of total volume of air contained in the lungs after a maximal inspiration, that is maximum amount of air that can be contained in lungs; Dlco expresses the diffusion capacity of gases from the alveoli to the pulmonary capillary circulation, and therefore expresses the thickness of the alveolar-capillary membrane (with the same alveolar surface and pulmonary flow).

What is spirometry and indications

Through the interpretation of the aforementioned parameters it is possible to obtain important values from a diagnostic, prognostic and response point of view. treatment, which are fundamental in the implementation of a correct clinical practice towards lung diseases.

Roughly speaking, lung diseases are divided into two large classes: pathologies obstructive and pathologies restrictive. This subdivision takes place through the Tiffenau index, which is equal to the ratio between FEV1 and CVF (FEV1 / CVF): conventionally, when the ratio is less than 0.7 we speak of obstructive pathology, while if it is higher it falls into the class of restrictive pathologies. In reality there is also a third series, in which the Tiffenau value is greater than 0.7 but the pathology is obstructive; in this case it is necessary to add the reading of a flow - volume spirometric trace, which will be specific for this class.

Within the category of restrictive pathologies, two further types are identified: intrapulmonary diseases (eg pneumonia, atelectasis, pulmonary edema) e extra-pulmonary diseases (such as idiopathic pulmonary fibrosis, IPF). To distinguish them, the Dlco value is useful, which will be decreased in the second case and normal in the first.

Total lung capacity is a further index that differentiates obstructive from restrictive diseases: in obstructive ones it will be normal or increased (especially in the case of advanced disease), while in restrictive ones it will always be decreased.

Indications for conducting a spirometry

It is possible that the treating physician may indicate that a spirometry test should be performed on a patient with a wide variety of symptoms or a certain medical history. Spirometry can therefore be indicated in subjects with a long history of cigarette smoking and / or who carry out particular work activities at risk, or who have persistent dry cough, wheezing, dyspnoea, nocturnal awakening due to a sense of chest tightness.

The spirometric examination has a diagnostic value for important diseases such as asthma and the COPD; in addition to this, it is indicated in many other cases: in follow up of the patient with lung disease to check the response to treatment, in characterization the degree of disability that involves the disease, as a prognostic index in evolution of the pathology and also in the rating pre-operative in case of thoracic interventions (but not only).

Normal value consideration

It is actually incorrect consider gods reference values both as regards the Tiffenau index and the other parameters. The value of 0.7 can only be corrected for subjects with an age of around 50 years: in subjects Young people, a value of 0.75 would not be considered pathological, when in reality it is almost certainly already an indication of an obstructive pathology; conversely, an equal or even slightly lower value in a subject elderly it can be completely normal.

This is because with the age there's a normal drop in parameters of functionality respiratory; furthermore, these may also vary with the sex and the constitution physics. It is clear that a tall adult male can have a much higher total lung capacity than a child or a short woman; for this reason it is sometimes appropriate to speak of average lung capacity (average CPT, in adults about 5.9-6 liters).

For this, each value must be compared with specific ranges for the age, sex and physique of the individual patient

Spirometry: how it is done

Simple spirometry

The spirometry test is performed in the hospital setting of a pulmonology ward.

For the success of a spirometry test a certain is required cooperation by the patient, and therefore there are some rules of execution: the position must be correct (torso straight, chin raised), one must be applied clip nasal so as to breathe only with the mouth, with the lips narrow around the mouthpiece of the spirometer tube, not There must be movements torso or head during breathing maneuvers.

At the time of the test, the patient will have to do one inspiration maximal followed by a exhalation maximal, so that the spirometer can detect flows and calculate volumes; they're necessary at least three several maneuvers of this type with a difference of less than 150 ml between the different values measured. The maneuvers can be repeated until the maximum possible values are obtained, up to a limit of eight repetitions after which the performance of the subject inevitably drops.

How is spirometry performed?

Technique for performing the spirometric examination.

Global spirometry with plethysmography

As for the detection of total lung capacity, we use the plethysmograph: it is a real sealed cabin, inside which the patient can breathe only through a tube connected to the spirometer, which communicates with the outside.

Through the detection of pressure variations in the cabin plethysmographic while breathing, this method allows you to calculate the various lung volumes, including the volume residue (that quantity of air that remains in the lungs at the end of a maximal expiration, preventing its collapse) and therefore the total lung volume (which will be given by the sum of the residual volume and the forced vital capacity).

Global spirometry with Dlco

Determining the diffusion capacity of gases requires still different instrumentation. In this case, in fact, it is necessary to make the patient breathe a mixture of air containing, among other gases, also the carbon monoxide (CO) in extremely low concentration (0.3%); this gas is necessary as it has a great affinity for the hemoglobin (200 times higher than that of oxygen), therefore its diffusion is limited only by the thickness of the membrane (which is the subject of the test) and by the blood flow (which remains almost constant).

In this exam the patient will need to breathe a tidal volume (normal breathing, not forced) for a few minutes, keeping the volume of residual functional capacity constant (i.e. always exhaling in the same way). Subsequently, he will have to exhale completely (thus reaching the residual volume), and immediately afterwards inhale from the tube containing the gas mixture until the lungs are saturated; he will then have to hold his fate for about 10 seconds, and then exhale completely again.

The measurement of the CO concentrations before and after the test will allow to calculate the amount of carbon monoxide that is diffused in the blood, and therefore to determine the Dlco value.

Spirometry for the diagnosis of asthma

Spirometry, among the various possibilities, is used very often for the diagnosis of asthma: this is a pathology that affects about 6.5% of the Italian population, characterized by four key symptoms (dry cough, dyspnea, hissing is chest tightness) and exacerbations (often early in the morning).

The values obtained from a spirometry in an asthmatic subject they will be those of an obstructive pathology: decrease of the Tiffenau index and normal total lung capacity. In this particular case a reversibility test with administration of salbutamol (short-acting bronchodilator), which will lead to a decrease in symptoms and an improvement in spirometric values (if the subject is actually asthmatic).

If, on the other hand, the subject has normal spirometry, but the clinical suspicion for asthma is high (familiarity, typical symptoms, risk factors), it will be appropriate to perform a spirometry with methacholine, in which through the administration of this drug (starting from minimal doses, increasing up to causing mild symptoms) it will cause bronchoconstriction in the asthmatic subject; in this case, if the FEV1 will undergo a greater decrease than 20%, a diagnosis of asthma can be made.

Special case: respiratory failure

We speak of respiratory insufficiency when we are faced with an inability of the subject to ventilate properly, and which therefore has a partial pressure value of oxygen in the blood below 60 mmHg. This value can only be determined through a blood gas analysis, and cannot be investigated through spirometry.

Cost of spirometry

As for subjects suffering from chronic diseases, such as COPD and asthma, the execution of spirometry tests is free in hospitals, under medical prescription (exemption). As for the private regime, however, prices can vary from 15 euros upwards; under an agreement, prices depend on regional regulations on the payment of health tickets.

What is simple and global spirometry

There spirometry is a fundamental investigation technique in the field of pulmonology, used for numerous functions. Spirometry is one of the most important respiratory function tests and allows, in fact, to detect some parameters related to the respiratory function of the subject who performs it, which in turn can have a value diagnostic is prognostic, as well as of monitoring of the therapeutic efficacy and for the evaluation of the degree of disability.

Essentially, spirometry is a test that involves the rating of the ability to exhale a certain volume of air as a function of time, by performing maneuvers respiratory through a tube connected to the spirometer. The latter is a machine capable of detecting and calculating some parameters necessary for the characterization of any respiratory pathology of the subject.

In the simple spirometry exam, two values are evaluated: VEMS (or FEV1), i.e. the maximum expiratory volume in one second, and the CVF (or FVC), i.e. the forced vital capacity. These volumes are two parameters that are automatically calculated by the spirometer during the execution of one maneuver respiratory which provides a first inspiration maximal (inhale until no more air can be introduced) followed by one exhalation maximal (exhale all the air until you can no longer).

In spirometry global, in addition to the two values mentioned above, the determination of two further parameters is also envisaged: CPT (total lung capacity) e Dlco (alveolar-capillary diffusion of CO). Total lung capacity expresses the amount of total air volume contained in the lungs after a maximal inspiration, i.e. the maximum amount of air that can be contained in lungs; Dlco expresses the diffusion capacity of gases from the alveoli to the pulmonary capillary circulation, and therefore expresses the thickness of the alveolar-capillary membrane (with the same alveolar surface and pulmonary flow).

What is spirometry and indications

Through the interpretation of the aforementioned parameters it is possible to obtain important values from a diagnostic, prognostic and response point of view. treatment, which are fundamental in the implementation of a correct clinical practice towards lung diseases.

Roughly speaking, lung diseases are divided into two large classes: pathologies obstructive and pathologies restrictive. This subdivision takes place through the Tiffenau index, which is equal to the ratio between FEV1 and CVF (FEV1 / CVF): conventionally, when the ratio is less than 0.7 we speak of obstructive pathology, while if it is higher it falls into the class of restrictive pathologies. In reality there is also a third series, in which the Tiffenau value is greater than 0.7 but the pathology is obstructive; in this case it is necessary to add the reading of a flow - volume spirometric trace, which will be specific for this class.

Within the category of restrictive pathologies, two further types are identified: intrapulmonary diseases (eg pneumonia, atelectasis, pulmonary edema) e extra-pulmonary diseases (such as idiopathic pulmonary fibrosis, IPF). To distinguish them, the Dlco value is useful, which will be decreased in the second case and normal in the first.

Total lung capacity is a further index that differentiates obstructive from restrictive diseases: in obstructive ones it will be normal or increased (especially in the case of advanced disease), while in restrictive ones it will always be decreased.

Indications for conducting a spirometry

It is possible that the treating physician may indicate that a spirometry test should be performed on a patient with a wide variety of symptoms or a certain medical history. Spirometry can therefore be indicated in subjects with a long history of cigarette smoking and / or who carry out particular work activities at risk, or who have persistent dry cough, wheezing, dyspnoea, nocturnal awakening due to a sense of chest tightness.

The spirometric examination has a diagnostic value for important diseases such as asthma and the COPD; in addition to this, it is indicated in many other cases: in follow up of the patient with lung disease to check the response to treatment, in characterization the degree of disability that involves the disease, as a prognostic index in evolution of the pathology and also in the rating pre-operative in case of thoracic interventions (but not only).

Normal value consideration

It is actually incorrect consider gods reference values both as regards the Tiffenau index and the other parameters. The value of 0.7 can only be corrected for subjects with an age of around 50 years: in subjects Young people, a value of 0.75 would not be considered pathological, when in reality it is almost certainly already an indication of an obstructive pathology; conversely, an equal or even slightly lower value in a subject elderly it can be completely normal.

This is because with the age there's a normal drop in parameters of functionality respiratory; furthermore, these may also vary with the sex and the constitution physics. It is clear that a tall adult male can have a much higher total lung capacity than a child or a short woman; for this reason it is sometimes appropriate to speak of average lung capacity (average CPT, in adults about 5.9-6 liters).

For this, each value must be compared with specific ranges for the age, sex and physique of the individual patient

Spirometry: how it is done

Simple spirometry

The spirometry test is performed in the hospital setting of a pulmonology ward.

For the success of a spirometry test a certain is required cooperation by the patient, and therefore there are some rules of execution: the position must be correct (torso straight, chin raised), one must be applied clip nasal so as to breathe only with the mouth, with the lips narrow around the mouthpiece of the spirometer tube, not There must be movements torso or head during breathing maneuvers.

At the time of the test, the patient will have to do one inspiration maximal followed by a exhalation maximal, so that the spirometer can detect flows and calculate volumes; they're necessary at least three several maneuvers of this type with a difference of less than 150 ml between the different values measured. The maneuvers can be repeated until the maximum possible values are obtained, up to a limit of eight repetitions after which the performance of the subject inevitably drops.

Global spirometry with plethysmography

As for the detection of total lung capacity, we use the plethysmograph: it is a real sealed cabin, inside which the patient can breathe only through a tube connected to the spirometer, which communicates with the outside.

Through the detection of pressure variations in the cabin plethysmographic while breathing, this method allows you to calculate the various lung volumes, including the volume residue (that quantity of air that remains in the lungs at the end of a maximal expiration, preventing its collapse) and therefore the total lung volume (which will be given by the sum of the residual volume and the forced vital capacity).

Global spirometry with Dlco

Determining the diffusion capacity of gases requires still different instrumentation. In this case, in fact, it is necessary to make the patient breathe a mixture of air containing, among other gases, also the carbon monoxide (CO) in extremely low concentration (0.3%); this gas is necessary as it has a great affinity for the hemoglobin (200 times higher than that of oxygen), therefore its diffusion is limited only by the thickness of the membrane (which is the subject of the test) and by the blood flow (which remains almost constant).

In this exam the patient will need to breathe a tidal volume (normal breathing, not forced) for a few minutes, keeping the volume of residual functional capacity constant (i.e. always exhaling in the same way). Subsequently, he will have to exhale completely (thus reaching the residual volume), and immediately afterwards inhale from the tube containing the gas mixture until the lungs are saturated; he will then have to hold his fate for about 10 seconds, and then exhale completely again.

The measurement of the CO concentrations before and after the test will allow to calculate the amount of carbon monoxide that is diffused in the blood, and therefore to determine the Dlco value.

Spirometry for the diagnosis of asthma

Spirometry, among the various possibilities, is used very often for the diagnosis of asthma: this is a pathology that affects about 6.5% of the Italian population, characterized by four key symptoms (dry cough, dyspnea, hissing is chest tightness) and exacerbations (often early in the morning).

The values obtained from a spirometry in an asthmatic subject will be those of an obstructive pathology: decrease in the Tiffenau index and normal total lung capacity. In this particular case a reversibility test with administration of salbutamol (short-acting bronchodilator), which will lead to a decrease in symptoms and an improvement in spirometric values (if the subject is actually asthmatic).

If, on the other hand, the subject has normal spirometry, but the clinical suspicion for asthma is high (familiarity, typical symptoms, risk factors), it will be appropriate to perform a spirometry with methacholine, in which through the administration of this drug (starting from minimal doses, increasing up to causing mild symptoms) it will cause bronchoconstriction in the asthmatic subject; in this case, if the FEV1 will undergo a greater decrease than 20%, a diagnosis of asthma can be made.

Special case: respiratory failure

We speak of respiratory insufficiency when we are faced with an inability of the subject to ventilate properly, and which therefore has a partial pressure value of oxygen in the blood below 60 mmHg. This value can only be determined through a blood gas analysis, and cannot be investigated through spirometry.

Cost of spirometry

As for subjects suffering from chronic diseases, such as COPD and asthma, the execution of spirometry tests is free in hospitals, under medical prescription (exemption). As for the private regime, however, prices can vary from 15 euros upwards; under an agreement, prices depend on regional regulations on the payment of health tickets.

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