Lung Function Tests Sema Umut

Lung Factors Affecting Function Mechanical properties Resistive elements

Mechanical Properties Compliance Describes the stiffness of the lungs Change in volume over the change in pressure Elastic recoil The tendency of the lung to return to it’s resting state

Resistive Properties Determined by airway caliber Affected by Lung volume Bronchial smooth muscles Airway collapsibility

A TEST SHOULD BE Acceptabile,easy Noninvasive Cost effective Informative Reproducible

Spirometry Acceptabile,easy Noninvasive Cost effective Inexpensive Informative Reproducible

Spirometry It is the most commonly used lung function screening study It should be the clinician's first option

When can spirometry help us? - Diagnosing disease - Monitoring disease - Prognosis Directing therapy Lung Age for prognostication

Indications for Spirometry Diagnostic To evaluate symptoms, signs, or abnormal laboratory tests Dyspnea Wheezing Cough Abnormal breath sounds Overinflation Expiratory slowing Cyanosis

Abnormal laboratory tests Hypoxemia Hypercapnia Polycythemia Abnormal chest radiographs

To screen individuals at risk of having pulmonary diseases Smokers Individuals in occupations with exposures to injurious substances

Indications for Spirometry To assess preoperative risk To assess health status before physical activity programs To evaluate therapy

Disability/Impairment Evaluations To assess individuals for legal reasons

FEV1/ht2 best index Prognosis Survival predictor of general population Copenhagen City Heart Study 13,900 subjects for 25 yrs Lange P. J Clin Epidemiol 1990; 43: 867-873. Cox proportional hazards FEV1/ht2 best index Framingham study No experts in lung function. Self appointed group of chums. Not affiliated to American Thoracic or European Resp Societies

Spirometry Requirements 1. Good equipment 2. Good technicians (efor dependent) 3. Good clinicians - correct indication - correct use / presentation of the data - correct decision making No experts in lung function. Self appointed group of chums. Not affiliated to American Thoracic or European Resp Societies

Pulmonary Function Testing relates Age : Smaller lung volumes as we age Gender : The lung volumes of males are larger than females Height Race

Perform manoeuvre Attach nose clip, place mouthpiece in mouth Inhale completely and rapidly Exhale maximally until no more air can be expelled Repeat for a minimum of 3 manoeuvres

Forced Vital Capacity FVC Total volume of air expired forcefully after a full inspiration Patients with restrictive lung disease have a decreased vital capacity

Slow Vital Capacity (SVC) This is the total volume of air expired slowly after a full inspiration If the SVC is greater than FVC,it indicates the presence of obstructive disease

FEV1 Forced Expiratory Volume in 1 Second Volume of air expired in the first second during maximal expiratory effort

FEV1/FVC Percentage of the forced vital capacity which is expired in the first second of maximal expiration to forced vital capacity In health the FEV1/FVC is usually around 80% Decrease in FEV1/FVC means obstruction

Tidal volume TV The volume of air moved during normal quiet breathing (about 0.5 L)

RESIDUEL VOLUME (RV) The volume of air remaining in the lungs after a forceful expiration (about 1.0 L).

FUNCTIONAL RESIDUEL CAPACITY(FRC) The amount of air remaining in the lungs after a normal quiet expiration

TOTAL LUNG CAPACITY (TLC) It is the volume of air in the lungs when the person has taken a full inspiration TLC = RV + VC

TLC,RV,FRC Can not be measured by spirometry Helium dilution Nitrogenmetry Body plethysmography

INTERPRETATION OF SPIROMETRY Compare the measured values of the patient with normal values derived from population studies The percent predicted normal is used to define normal and abnormal and to grade the severity of the abnormality

Categories of Disease Obstructive Restrictive Mixed

Spirogram measures two components - air flow and volume If flow is reduced, the defect is obstructive If volume is reduced the defect is restrictive

Interpretation FVC and FEV1 are normal – NORMAL FVC is low but FEV1/FVC is >80 RESTRICTIVE FEV1/FVC < 70% OBSTRUCTIVE

Spirometry Obstruction (FEVı /FVC) < %70

Obstructive Lung Diseases Asthma Chronic obstructive pulmonary disease

COPD -COPD is characterized by airflow limitation that is not fully reversible -The airflow limitation is usually progressive and associated with an abnormal inflammatory response of the lung to noxious particles or gases

indoor/outdoor pollution Diagnosis of COPD EXPOSURE TO RISK FACTORS SYMPTOMS cough tobacco sputum occupation shortness of breath indoor/outdoor pollution A diagnosis of COPD should be considered in any patient who has cough, sputum production, or dyspnea and/or a history of exposure to risk factors. The diagnosis is confirmed by spirometry. To help identify individuals earlier in the course of disease, spirometry should be performed for patients who have chronic cough and sputum production even if they do not have dyspnea. Spirometry is the best way to diagnose COPD and to monitor its progression and health care workers to care for COPD patients should have assess to spirometry. è è è SPIROMETRY

Asthma Asthma is a chronic inflammatory disease of the airways Inflammation causes the airways to narrow periodically This produces wheezing and breathlessness Obstruction to air flow is reversible

Bronchodilator Test Evaluates how responsive the patient is to a bronchodilator medication Spirometry is repeated about 15 minutes after giving a bronchodilator (400 mg salbutamol)

WHY TEST FOR REVERSIBILITY? To determine best function To follow rate of change in PFTs over time To exclude asthma To determine response to therapy

REVERSIBILITY Increase of 200 ml or 12-15% of the baseline FEV1 shows REVERSIBLE OBSTRUCTION 40 Both drugs combined 30 20 10 2 4 6 8

Restriction Restriction means a decrease in lung volumes

Extrinsic Restrictive Lung Disorders . Neuromuscular Disorders . Scoliosis, Kyphosis . Rib fractures . Pleural Effusion . Pregnancy . Gross Obesity . Tumors . Ascites

Intrinsic Restrictive Lung Disorders Pnuemonectomy Pneumonia Lung tumors Interstitial lung diseases Sarcoidosis Lung oedema

Flow – Volume Loop is a measure of how much air can be inspired and expired from the lungs It is a flow rate measurement

Restrictive Lung Disease Characterized by diminished lung volume Decreased TLC, FVC Normal FEV1/FVC ratio

Large Airway Obstruction can be detected by Flow – Volume Loop Characterized by a truncated inspiratory or expiratory loop

Extra-thoracic Upper Airway Obstruction

Peak Expiratory Flow Rate PEFR The maximum flow rate during the forced vital capacity maneuver Useful to monitor asthma

Measuring PEF PEF must be achieved as rapidly as possible and at a high lung volume as possible The subject must be encouraged to blow as vigorously as possible

PEF can be very useful in diagnosing occupational asthma When is PEF useful? PEF can be very useful in diagnosing occupational asthma

ARTERIAL BLOOD GASES INDICATION Oxygenation Ventilation Acid-Base Status There are 3 reasones why one should obtain a blood gas:

ARTERIAL BLOOD GASES Blood gases is a measurement of how much oxygen and carbon dioxide is in the blood Determines the acidity (pH) of the blood

ARTERIAL BLOOD GASES Blood is taken from an artery The blood may be collected from the radial artery, the femoral artery , or the brachial artery

ARTERIAL BLOOD GASES After the blood is taken, pressure is applied to the site for a few minutes to stop the bleeding The sample must be quickly sent to a laboratory

Blood Gas Report pH 7.4 PaCO2 (mm Hg) 40 PaO2 (mm Hg) 110 - 0.5(age) HCO3- (mmol/L) 24 B.E. (mmol/L) 0 O2 saturation >90% This is a typical printout from a blood gas report:

Causes of a low PaO2 V/Q mismatch Dead space ventilation Shunt Diffusion Impairment Alveolar Hypoventilation Altitude

Alveolar Hypoventilation Reduced Respiratory Drive Pump failure

ANALYSIS OF VENTILATON Hypercapnea > 45 mm Hg Hypoventilation Respiratory Acidosis Hypocapnea < 35 mm Hg Hyperventilation Respiratory Alkalosis

Respiratory alkalosis Low levels of carbon dioxide in the blood due to alveolar hypervetilation (breathing excessively)

Respiratory acidosis The kidneys and lungs maintain the body's acid/base (pH) balance Respiratory acidosis develops when carbon dioxide is elevated Primarily caused by alveoler hypoventilation ( decreased breathing)

Pitfalls Venous Sample _PaO2 = 40, PaCO2 = 45 Air-bubble in syringe Free flow into syringe Air-bubble in syringe Falsely elevated PaO2 Arterial blood sample should be transported on ice under anaerobic conditions

Spirometry is essential in respiratory evaluation as tension arterial measurement is essential in cardiovascular evaluation