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Pulmonary Function Tests
Ghassan Jamaleddine, M.D.American University of Beirut
Use of PFT’s
• Evaluating breathlessness
• Initial evaluation of patient with known respiratory disease
• Following the course of a respiratory disease
• Pre-operative assessment
• Disability evaluation
• Screening of subclinical disease
Disadvantages of PFT’s
• Patient’s cooperation and an informed technician are required
• Measures the lung and chest as a unit
• Evaluates disease at only one point in time
• Errors in programs of computer driven automated equipment
Routine PFT’s
• Spirometry with or without Flow Volume loop
• Static lung volumes
• Single Breath Diffusing Capacity
Spirometry
• Forced vital capacity• Forced Expiratory Volume in one second
(FEV1)• Percent Expired (FEV1/FVC or FEV1%)• Forced Mid-Expiratory Flow (FEF 25-75)
or Maximal Mid-Expiratory Flow (MMEF or MMF)
• Peak or Maximal Expiratory Flow Rate (PEF or MEFR)
Pattern of defects seen on PFT’s
• Obstructive Vent defect– FVC reduced or
Normal– FEV1 reduced– FEV1/FVC is reduced
• Example: Asthma, COPD
• Restrictive Vent defect– FVC reduced– FEV1 normal or
reduced– FEV1/FVC is
increased
• Example: pulmonary fibrosis, pleural effusion, neuromuscular
P1V1 = P2 (V1-Δ V)
Lung Volumes
• Functional Residual Capacity
• Expiratory Reserve Volume
• Residual Volume
• Inspiratory Capacity
• Total Lung Capacity
• Vital Capacity
FLOW VOLUME LOOP
Diffusion
• Transfer of a gas across a tissue sheet, governed by Fick’s law
• Rate of Transfer = A D x P/T
Diffusion Capacity (measurement)
A D x (P1- P2) T
AD/T = Diffusion constante
Rate of transfer (CO) = Vco = Dlco x (P1-P2)
Dlco = Vco/ PA –Pa = Vco/ PA
25 ml/min/mmHg
Diffusing Capacity
• Influenced by:– Changes in alveolar-capillary
membrane
– Pulmonary circulation
– Ventilation perfusion matching
– Hemoglobin concentration
Diffusion Capacity
• Very important in – Interstitial lung disease– Drug induced lung injury
• Reduced in Emphysema because of destruction of alveolar units
PFT Patterns in Disease
PFT results are best interpreted with knowledge of the patients history, physical exam and occasionally chest X-ray.
PFT Disease
Obstructive Restrictive
FVC N or
FEV1
FEV1/FVC N
MMEF or V50 N or
MVV N or
FRC N or
RV
TLC N or
Case 1
• 14 year old boy came to ER with increasing shortness of breath
• History of asthma since age of 2-3
• Maintained on ICS and Beta2 agonists
• Followed by Family physician, past year frequent attacks, several courses of antibiotics and systemic corticosteroids
Case 1 (cont’d)
• In ER started on iv steroids and inhaled Beta 2 agonists, no improvement, admitted
• No history of atopy, no nasal nor GI symptoms, no family history of asthma
• Exam: decrease breath sounds
• Admitted
Case 1 (cont’d)
• CXR, CBC, chemistry non revealing
• After 2 days of treatment with steroids and inhaled bronchodilators there was no improvement in symptoms
• Noticed faint voice and tachypnea on minimal exercise
• PFT obtained
Case PFT’s
• FVC 93%, FEV1 45%, FEV1/FVC 41%
• TLC 90%, RV 90%, DLCO 100%
• ?????
Case 1(cont’d)
• FOB: subglottic stenosis (? Congenital)
• Tracheostomy followed by reconstructive surgery
• Total recovery, no more asthma treatment
Case 2
• 32 year old man presented with 2 months history of increasing shortness of breath
• Married, non-smoker, bank employee, no history of asthma
• No other symptoms• Shortness of breath increasing before
presentation• Seen by multiple physicians, given a number of
antibiotics, bronchodilators, aminophylline
Case 2 (Cont’d)
• Exam: BP 120/80, RR 18, P100, BMI 29, afebrile, chest: clear… rest of exam was normal
• ER: ABG’s normal, CXR: normal, CT angio: normal, neuro consult (fellow): no neuro problem
• Patient reassured by the team
Case 2 (cont’d)
• Spirometry obtained:– FVC 50%– FEV1 55%– FEV1/FVC 80%– MVV 20%– ????
Case 2 (cont’d)
• Neurology attending reconsulted
• EMG: Myasthenia Gravis
• Diagnosis suspected from FVC and MVV– Neuromuscular illness
Case 3
• A 60 year old man with history of ex-smoking, history of seasonal colds, admitted for hernia operation
• Pulmonary consulted for pre-op clearance because of obesity
• The patient denied pulmonary complaints, but his wife disclosed that he has a chronic cough
Predicted Values
Measured Values
% Predicted
FVC 6.00 liters 4.00 liters 67 %
FEV1 5.00 liters 2.00 liters 40 %
FEV1/FVC 83 % 50 % 60 %
Case 3
Obstructed defect
Case 3
Pre-operative screening
• Patients with known pulmonary illness or symptoms
• Overweight patients
• Patients undergoing surgery in the chest or near the diaphragm
Case 4
• A 65 year old man non-smoker, lawyer, admitted for elective Lap Chole. Reports long history of mild cough, and dyspnea on exertion
• Physical exam: bibasilar dry crackles (velcrow), clubbing of the fingers
Case 4
Predicted Values Measured Values % Predicted
FVC 5.68 liters 4.43 liters 65 %
FEV1 4.90 liters 3.52 liters 60 %
FEV1/FVC 84 % 79 % 94 %
Restricted defect
Case 4
• TLC 60%
• RV 40%
• DLCO 40%
• HRCT
Case 4
Case 5
• 68 year old man with progressive dyspnea of one year duration, ex-smoker, no cough, no wheezing, no orthopnea…
• History of CAD, SVT post angioplasty on multiple medication
• EF% 55
• Meds: Plavix, beta one blocker, diuretics, cordarone, ARB,
Case 5
• FVC 50%
• FEV1 55%
• FEV1/FVC 85%
• TLC 70%
• DLCO 50%
Case 5
• PFT’s: Major drop in FVC and DLCO compared to the PFT done 2 years earlier
• HRCT of chest: Increased markings over the bases, with areas of increased enhancement…. Consistent with Amiodarone toxicity
Follow up patients
• Connective Tissue diseases (e.g. scleroderma)
• Patients on Therapy that might affect the pulmonary system
• Neuromuscular diseases
Follow up Patients with Lung Diseases
• Obstructive airway diseases
• Interstitial lung diseases– Sarcoidosis– IPF– ILD (CTD)
Conclusion
• PFT’s– Spirometry– Lung volumes– DLCO
Conclusion: Indications
• Evaluating breathlessness
• Initial evaluation of patient with known respiratory disease
• Following the course of a respiratory disease
• Pre-operative assessment
• Disability evaluation
• Screening of subclinical disease