Pulmonary Function Testing (Spirometry)

Spirometry is a pulmonary function test. It is used to measure and record lung or respiratory volume and airflow velocities to assess lung function.Spirometry is performed for early detection of lung disease as well as for follow-up during therapy for lung disease. By means of spirometry, obstructive and restrictive lung diseases are distinguished:

  • Obstructive lung diseases – respiratory work is complicated by obstruction of airflow associated with the subjective feeling of dyspnea (shortness of breath), such as in bronchial asthma or chronic obstructive pulmonary disease (COPD).
  • Restrictive lung disease – The lungs and/or chest have decreased distensibility; these include:
    • Pulmonary diseases: exogenous allergic alveolitis (allergic inflammation of the alveoli (air sacs in the lungs) caused by inhalation of particulate matter), pulmonary fibrosis (chronic inflammation of the connective tissue of the lungs with abnormal proliferation of connective tissue between the alveoli), pneumoconioses (dust inhalation diseases), sarcoidosis (synonyms: Boeck’s disease; Schaumann-Besnier’s disease; systemic disease of connective tissue with granuloma formation of the skin, lungs and lymph nodes).
    • Neuromuscular diseases such as progressive muscular dystrophy.
    • Obesity per magna (BMI ≥ 40)
    • Thoracic deformities such as ankylosing spondylitis (chronic inflammatory disease of the spine that can lead to joint stiffness (ankylosis) of the affected joints) and kyphoscoliosis (hump formation (kyphosis) with simultaneous lateral curvature (scoliosis) of the spine)
    • Condition after partial lung resection (removal of a part of the lung).

Indications (areas of application)

  • Smokers
  • Dyspnea (shortness of breath)
  • Bronchial asthma
  • Bronchial carcinoma (lung cancer)
  • Chronic bronchitis (inflammation of the larger branched airways – the bronchi).
  • Chronic obstructive pulmonary disease (COPD)
  • Pulmonary emphysema (irreversible hyperinflation of the smallest air-filled structures (alveoli, alveoli) of the lungs).
  • Pulmonary fibrosis
  • Cystic fibrosis (synonym: cystic fibrosis)
  • Pleural effusion
  • Pneumoconiosis
  • Pneumonia (pneumonia)

The procedure

During spirometry, the changes in the different lung volumes are continuously recorded and graphically displayed. A distinction is made between a closed and an open system. In the closed system (bell spirometer), the patient is connected via a mouthpiece to a closed air space whose volume changes according to breathing.In the open system, which is usually preferred, the patient breathes through a breathing tube in which the respiratory velocity and flow rate of the respiratory air are measured. The data are then analyzed by computer. The most important measurements of spirometry include:

  • Flow parameter
    • One-second capacity (FEV1; Engl : Forced Expiratory Volume in 1 second; Forced one second volume = seconds of air).
    • Peak flow (PEF; engl. : peak expiratory flow; peak expiratory flow; maximum respiratory flow rate).
    • Mean respiratory flow rate when 75% (MEF 75, mean expiratory flow), 50% (MEF 50) and 25% (MEF 25) of the vital capacity is still in the lungs.
  • Volume parameters
    • Vital capacity (VC) and forced vital capacity (FVC); VC = IRV + AZV + ERV (= lung volume between maximal inspiration and maximal expiration):
      • Airway volume (AZV)
      • Inspiratory reserve volume (IRV), describes the lung volume that can still be additionally inhaled after normal inspiration
      • Expiratory reserve volume (ERV), describes the lung volume that can still be exhaled after normal expiration.
    • FEV 1% (quotient of FEV1 and FVC; Tiffeneau test, normal value: >70%).

PEF is measured at the beginning of expiration, followed by MEF 75, 50, and 25

.
Spirometric differentiation between obstructive and restrictive ventilation disorders

Measured variables obstructive v. restrictive V.
Vital capacity (VC) normal to ↓ < 80% of the set point
Forced vital capacity (FVC) Normal
Absolute FEV1 ↓ (< 80 %)
Tiffeneau value < 70 % normal

Interpretation of spirometric measurement data

Spirometric variable Asthma COPD ACOS
Normal FEV1/FVC,before or after BD. Compatible (compatible) with diagnosis Not compatible with the diagnosis Not compatible unless there is other evidence of airway obstruction
After BP FEV1/FVC < 0.7 Indicates airway obstruction that may improve spontaneously or after therapy Required for diagnosis (GOLD). Normally present
FEV1 ≥ 80% of the target value Compatible with diagnosis (good control of asthma or interval between symptoms) Compatible with GOLD classification of mild pulmonary function impairment (category A or B) if according to BP FEV1/FVC < 0.7 Compatible with diagnosis of mild ACOS
FEV1 <80% of set point Compatible with diagnosis.Risk factor for exacerbations (severe disease flare-ups) of asthma Indicator of severe airway obstruction and risk for future events (eg, mortality/mortality and COPD exacerbations) Indicator of severe airway obstruction and risk for future events (e.g., mortality and exacerbations)
After BP increase in FEV1 >12% and 200 ml from baseline (= reversible lung function impairment). Normal occasionally during course of asthma, but not present if asthma is well controlled or patient is on controller therapy Common and more likely when FEV1 is low, but ACOS should also be considered Common and more likely if FEV1 is low, but ACOS should also be considered
After BP increase in FEV1 > 12% and 400 ml from baseline (shows reversibility) High probability of asthma Rare in COPD.ACOS should be considered Compatible with the diagnosis of ACOS

Legend

  • Bronchial asthma
  • COPD (= chronic obstructive pulmonary disease)
  • ACOS (AsthmaCOPD Overlap Syndrome) is present when clearly typical signs of both diseases (asthma + COPD) are present, ie, for example, asthma is known since childhood.
  • BD (= bronchodilator/”asthma spray”).

The residual volume (RV), which is the amount of air that remains in the lungs after maximum exhalation and total lung capacity (TLC) are determined by bodyplethysmography (synonym: whole-body plethysmography). Spiroergometry, also known as ergospirometry, is a method that provides information about cardiac and pulmonary performance by measuring respiratory gases, at rest and under stress. This method continuously measures the respiratory volume and the proportion of CO2 (carbon dioxide) and O2 (oxygen) in the air breathed.Spirometry is a harmless and painless examination method that can be used to detect lung diseases at an early stage. Early diagnosis helps at-risk patients avoid complications later – keeping you healthy and vital.