The types of pulmonary ventilation dysfunction are: obstructive ventilation dysfunction, restrictive ventilation dysfunction, and mixed ventilation dysfunction. Obstructive ventilatory dysfunction is characterized by a decrease in flow rate (FEV1.0/FVC%), whereas restrictive ventilatory dysfunction is characterized by a decrease in lung volume (e.g., VC), and mixed dysfunction is a combination of both. The main basis for determining the type of ventilatory dysfunction is the pulmonary function test, which needs to be combined with clinical data to make a correct conclusion.
The following steps can be used to analyze the results of pulmonary function tests: Xin Jianbao, Department of Respiratory Medicine, Wuhan Union Medical College Hospital
Step 1: FVC
If FVC is normal, restrictive ventilatory dysfunction can be basically ruled out. If it is reduced, it is necessary to identify whether it is obstructive or restrictive ventilatory dysfunction.
Step 2: FEV1
Normal: It can exclude the obvious restrictive and obstructive ventilation dysfunction.
Decreased: indicates the presence of ventilation dysfunction. Since both restrictive and obstructive ventilation dysfunction can show decreased FEV1, FEV1/FVC needs to be evaluated to determine if obstruction is present. If available, the TLC should be checked; an increase in TLC greater than 15% suggests obstruction; a normal or increased TLC may exclude restriction; a decrease in TLC suggests restriction, and for mixed ventilatory dysfunction, TLC may occasionally be normal.
Step 3: FEV1/FVC
Normal:Obstructive ventilatory dysfunction can usually be ruled out.
A normal or increased FEV1/FVC combined with a decreased FVC often suggests restrictive ventilation dysfunction. If in doubt, TLC or DLCO can be checked, and can be combined with a chest radiograph to check for a basis for reduced TLC.
Reduced FEV1/FVC is highly suggestive of obstructive ventilation dysfunction and is an important indicator of obstructive ventilation work disorder.
Step 4: Expiratory flow values
FEF25-75 is consistent with the change in FEV1, but is more sensitive.
Step 5: MVV
MVV is generally consistent with changes in FEV1, but is more sensitive. Clinically, MVV values can be calculated from FEV1. Under normal conditions, the expected MVV = FEV1 × 40, and the expected low limit of MVV can be used in clinical work as a basis for determining whether MVV is appropriate. the expected low limit of MVV = FEV1 × 30. if MVV < FEV1 × 30, it often indicates that the patient is not exerting, poor cooperation, fatigue, neuromuscular disorders, etc., and requires careful screening by the technician; if MVV is significantly > FEV1 × 30, it often indicates that the determination of FEV1 30, it often indicates that the patient has not exerted himself at the time of FEV1 determination or there is a serious obstructive ventilation dysfunction.
The main reasons for the uncoordinated lowering of MVV and FEV1 are atmospheric airway obstruction or neuromuscular disorders.
Step 6: DLco
A decrease in DLco is indicative of a restrictive lesion of the lung parenchyma. In case of simple decrease, pulmonary vascular pathology is mostly considered.
Increased, seen in asthma, obesity, alveolar hemorrhage, etc.
Step 7: Bronchial responsiveness measurement
omitted.
Case study – 1 Male, 59 years old. Height 151 cm. weight 46 kg.
Item
Expected value
Measured value
Measured/expected %
VC
2.91
1.29
44.4
FVC
2.82
1.27
45.1
FEV1
2.29
0.56
24.6
FEV1/FVC
44.19
FEV1/VC
76.59
43.58
56.9
MVV
94.1
19.41
20.6
Step 1: FVC
A decrease in FVC suggests the presence of pulmonary ventilation dysfunction, but then it is necessary to identify whether the cause is obstructive or restrictive.
Step 2: FEV1
A significant decrease in FEV1 combined with a significant decrease in FVC suggests the possibility of a restrictive cause, while FEV1/FVC needs to be evaluated to clarify the presence of an obstructive cause.
Step 3: FEV1/FVC
A significant decrease in FEV1/FVC is highly suggestive of obstructive ventilatory dysfunction.
Step 4: Expiratory flow values
Not provided.
Step 5: MVV
MVV expected = 0.56 x 30 = 16.8. MVV measured = 19.41, which, combined with the changes in each of the above indicators, is consistent with a change in MVV for severe obstructive ventilatory dysfunction, but of course requires the technician to combine the patient’s examination with the flow-volume graph to make a comprehensive judgment.
Conclusion: moderate restriction with severe obstructive ventilatory dysfunction.
Case study – 2 Male, 56 years old. Height 170 cm. weight 60 kg.
Item
Expected value
Measured value
Measured/expected %
FVC
4.00
3.48
87.2
FEV1
3.20
1.24
38.8
FEV1/FVC
35.6
MVV
119.21
48.29
40.5
RV/TLC
52.7
DLco
9.16
4.59
50.1
1) Normal FVC can exclude significant restrictive ventilatory dysfunction. Whether there is an obstructive cause, FEV1, FEV1/FVC need to be checked.
(2) A reduced FEV1 can clearly have an obstructive cause, and since the FVC is normal, its reduction may be due to obstructive ventilation dysfunction, which needs to be combined with FEV1/FVC to further affirm its judgment.
3) The decrease of FEV1/FVC can confirm the presence of obstructive ventilation dysfunction.
(4) MVV is expected to be 1.24×30=37.2. MVV measured=48.29, is it a serious obstructive cause or was FEV1 not measured with full power? It needs to be judged carefully by the technician, and a final decision needs to be made in conjunction with the FV graph.
5) Significantly higher RV/TLC indicates hyperinflation of the lungs, consistent with severe obstructive ventilatory dysfunction, and requires imaging to understand whether there are pathological changes such as emphysema.
6) Decreased DLco, indicating pulmonary diffusion impairment, coincides with RV/TLC and is consistent with severe obstructive ventilation dysfunction and pulmonary functional changes of emphysema.
7) Conclusion: severe obstructive ventilatory dysfunction with moderate diffusion impairment.