d

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Pulmonary function
test
Dr Altaf Alkamish

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Spirometry
 It’s simple, non invasive test used for evaluation of pulmonary function
 ۞Spirometry findings are non-specific and not pathognomonic for a certain
 diagnosis.
 ۞Spirometry findings are used to suggest but not to diagnose restrictive
lung disease

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 • VT; Tidal volume (L)
 • IRV; Inspiratory reserve volume (L)
 • ERV; Expiratory reserve volume (L)
 • FRC; Functional residual capacity (L)
 • VC; Vital capacity (L)
 • TLC; Total lung capacity (L)
 • FEV1; Forced Expiratory Volume in 1 s.
 • FVC; Forced Vital Capacity.
 MMEF25–75; Maximum Mid–
Expiratory Flow between 25 & 75%
Expired FVC.
 MEF50; Maximum Expiratory Flow
after 50% of Expired FVC
 DLCO; Diffusion Capacity for Carbon
Monoxide
 ‘TLCO’ mmol/min/kPa
 KCO; Transfer coefficient for carbon
monoxide mmol/min/kPa/L
 kPa; Kilo Pascal conversion factor to
mmHg is multiplying by 7.5

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indication
 ۞Assessment of Respiratory Symptoms as Dyspnoea, Cough & Wheezing.
 ۞Monitor Lung Function & Disease Progression.
 ۞Medication Responsiveness and Efficacy
 ۞Occupational Health-Related Questions.
 ۞Pulmonary Rehabilitation

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Relative Contraindication
 ۞Recent Myocardial Infarction or Unstable Angina (within 1 week)
 ۞Recent Abdominal or Thoracic Surgery (within 3 week)
 ۞Recent Eye or Ear Drum Perforation Surgery
 ۞Active Haemoptysis
 ۞Acute pulmonary embolism
 ۞Severe trauma
 ۞Highly Contagious Respiratory Tract Infection as Active Pulmonary Tuberculosis or
COVID-19 Infection

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Pre test instruction

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Patient
 ۞Patient Name
 ۞Birth Date
 ۞Drug hx. including Inhalers & Last Time Taken?
 ۞Measure Weight & Height
 ۞Is the patient Naïve or Experienced?

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Hight

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Post Bronchodilator Test
Medication;
 ۞Salbutamol; 4 Puffs 100 µg pMDI or 2.5mg via Nebulizer & Repeat Test 15 - 20 min.
 ۞Ipratropium Bromide; 4 puffs 20 µg & Repeated Test 40 min. Result; consistent with
hyperreactive airways:
 ۞In Adult; FEV1 or FVC increased by 10% and 200mL &
 ۞In Children; FEV1 < 12% pred.

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 Spirometry Measurement
2-volume
 FVC
 FEV1
2 – Flow
 PEFR
 FEF25–75
 FEV1/FVC %

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FEV1/FVC %
 FEV1/FVC %
 ۞Volume of air exhales in one second as a percentage of total volume of air exhaled.
 ۞Determine degree of severity of obstructive lung diseases
 ۞Normal; < 70%
 ۞Mild obstruction; 60 – 75 %
 ۞Moderate obstruction; 50 – 59 %
 ۞Sever obstruction; > 49 %

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FVC
 ۞Maximum amount of air that can be exhaled forcefully after a maximum
inspiration.
 ۞Depends on the age, sex, height and ethnicity
 ۞Determine degree of severity of restrictive lung diseases
 ۞Normal; < 80 – 120 %
 ۞Mild Restriction; 70 – 79 %
 ۞Moderate Restriction; 50 – 69 %
 ۞Sever Restriction; > 50 %

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 Measurement of the total lung capacity considered to ascertain a restrictive pattern defect either intrathoracic or extra-thoracic causes.
 ۞Pulmonary/Diseases of the Lung
 • Local diseases (e.g. pulmonary fibrosis, tumours, pneumonia, atelectasis)
 • Generalised organ involvement (e.g. congestion, ILD rheumatic disorders)
 ۞Extra-pulmonary - Pleura Diseases
 • Pleura Effusion/ Empyema
 • Pneumothorax
 • Pleural thickening
 ۞Extra-pulmonary - Chest Wall and Neuro-mascular Diseases
 • Neural, neuromuscular junction or muscular disorders
 • Traum

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FEV1
 ۞Volume of air exhaled during the first second of forced expiratory maneuver
 ۞Decrease in both obstructive and restrictive diseases
 ۞Normal; < 75 %
 ۞Mild obstruction; 60 – 75 %
 ۞Moderate obstruction; 50 – 59 %
 ۞Sever obstruction; > 49 %

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FEF25–75
 Mean expiratory flow during the middle of FVC ‘MEFR’
 ۞More sensitive for small airway disease
 ۞Normal; < 60 %
 ۞Mild obstruction; 40 – 60 %
 ۞Moderate obstruction; 20 – 40 %
 ۞Sever obstruction; > 20 %

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Criteria for Acceptable repeatability
Three acceptable FVC manoeuvres are required.
2 best trails
•ERS/ATS;
۞FEV1 & FVC > 150 ml
۞FEV1 & FVC > 5 %
۞PEF > 10 %

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Not Acceptable Test

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FEV1 is not reliable during poor effort to
start, so that recorded data should not be
interpreted, instructed to
exhale as forcibly and as long as possible

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Neither the FVC nor the FEV1 is reliable during
incomplete inhalation prior to forced expiration,
so that recorded data should not be interpreted.
Not Acc

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Neither the FVC nor the FEV1 is reliable during cough,
so that recorded data should not be interpreted

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FVC underestimated, as may be the FEV1 during
premature stop of exhalation and data from such curves
should not be interpreted

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FVC underestimated due to missing closure of flow
volume loop and data from such curves should not
be interpreted

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Hesitating at the start of the maneuver, or may be the
mouthpiece leak at the start of the forced expiration,
for that data cannot be reliably interpreted

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Interpretation

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Step I; Flow Volume Loop

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Step IV; Examine for Small
Airway Disease
 The forced expiratory flow rate over the middle 50% of the FVC
 (FEF25–75) almost always changes in the same direction as the FEV1.
 • It’s sensitive for detecting small airway obstruction
 Normal; < 60 %
 Mild obstruction; 40 – 60 %
 Moderate obstruction; 20 – 40 %
 Sever obstruction; > 20 %

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Step V; Post Bronchodilator Test
Medication;
۞Salbutamol; 4 Puffs 100 µg pMDI or 2.5mg via Nebulizer &
Repeat Test 15 - 20 min.
۞Ipratropium Bromide; 4 puffs 20 µg & Repeated Test 40 min.
Result; consistent with hyperreactive airways:
۞In Adult; FEV1 or FVC increased by 10% and 200mL &
۞In Children; FEV1 < 12% pred.

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Step VI; DLCO

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Variable intrathoracic expiratory airway
obstruction

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Variable extra-thoracic
inspiratory airway obstruction

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Fixed large airway obstruction

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