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