Pulmonary Function Tests-1 university.pptx

Pulmonary functions

1. Pulmonary Function Tests These are tests used in assessing the functional status of the respiratory system both in the physiological and pathological conditions. They are based on the measurement of volume of air breathed in and out in quiet and forced breathing.

2. Types of lung function Tests Static lung function Tests Dynamic lung function Tests

3. Static Lung Function Tests These are based on the volume of air that flows into or out of the lungs. These tests don’t depend upon the rate at which air flows. These include static lung volumes and static lung capacities.

4. Dynamic lung function tests These are based on time i.e. the rate at which air flows into or out of the lungs. These tests include forced vital capacity, forced expiratory volume, maximum ventilation volume and peak expiratory flow. Dynamic function tests are useful in determining the severity of obstructive and restrictive lung diseases.

5. Lung Volumes Static lung volumes are the volumes of air breathed in by an individual. Each of these volumes represents the volume of air present in the lung under specified static condition(specific position of the thorax). These include-Tidal Volume -Inspiratory reserve volume -Expiratory reserve volume -Residual volume

6. Cont. Tidal Volume: This is the volume of air breathed in and out of the lungs in a single normal quiet respiration. Normal volume is 500ml Inspiratory reserve volume: This is an additional volume of air that can be inspired forcefully after the end of normal inspiration. Normal volume is 3.300ml Expiratory reserve volume: This is an additional volume of air that can be expired out forcefully, after normal expiration. Normal volume is 1000ml Residual volume: This is the volume of air remaining in the lungs even after forced expiration. It helps to aerate the blood in between breathing and during expiratory, also maintains the contour of the lungs. Normal volume is 1,200mls

7. Lung capacities Static lung capacities are in combination of two or more lung volumes and we have 4 types Inspiratory capacity Vital capacity Functional residual volume Total lung capacity

8. Cont. Inspiratory capacity-This is the maximum volume of air that is inspired after normal expiration. IC=TV+IRV 500+3,300=3800ml Vital capacity-This is the maximum volume of air that can be expelled out forcefully after a deep inspiration. This includes inspiratory reserve volume , tidal volume and expiratory reserve volume. VC=IRV+TV+ERV 3,300+500+1000=4800ml

9. Cont. Functional Residual volume-This is the volume of air remaining in the lungs after normal expiration. It includes expiratory reserve volume and residual volume. FRV=ERV+RV 1000+1200=2200ml. Total lung capacity-This is the volume of air present in the lungs after a deep inspiration. It includes all the volumes. TLC=IRV+TV+ERV+RV 3300+500+1000+1200=6000ml

10. Comparisons Static lung volumes vs. static lung capacities The difference is that static lung volumes are the four basic, individual volumes of air measured in the lungs (tidal volume, inspiratory reserve volume, expiratory reserve volume, and residual volume), while static lung capacities are the sum of two or more of these volumes, representing a combination of different lung volumes for example vital capacity, total lung capacity. The static lung volumes can be measured directly through spirometry while the capacities are through sum of two or more volumes. Static lung volumes vs. dynamic lung volumes Static lung volumes is the measurement of volume of air in the lungs at various stages of breathing without regard of time fore example tidal volume while dynamic lung volumes measure the flow and speed of air moving in and out of the lungs over time especially during forced breathing maneuvers for example forced vital capacity, forced expiratory volume in one second,FEV1/FVC ratio, peak expiratory flow rate.

11. Measurement of lung volumes and capacities Spirometry is the method used to measure lung volumes and capacities. Instruments used-spirometer(manual) -Modified spirometer called respirometer -Computerized spirometer

12. Spirometry This is the most common lung function test which measures airflow(dynamic lung volumes) and the key measurements include Forced vital capacity, forced expiratory volume in one second,FEV1/FVC ratio, peak expiratory flow rate . Most of the lung volumes and capacities are measured except residual volume, total lung volume and functional residual capacity and these are measured by other methods like body plesmography, helium or nitrogen washout and imaging. How does it work? A spirometer is the device used , It usually has a mouth piece connected to a small machine or computer that records your breathing. Procedure Patients sit upright and wear a nose clip to ensure all the air exits through the mouth Takes a deep breath in , filling the lungs as much as possible Then blow out as hard and fast as you can into the spirometer until the lungs are empty. The test usually takes 10-15 minutes and may be repeated about 3 times to ensure accuracy.

13. Measurements Taken Forced vital capacity, Forced expiratory volume in one second,FEV1/FVC ration, peak expiratory flow. Spirometry is primarily used to diagnose and monitor Asthma, COPD, Pulmonary fibrosis and other restrictive or obstructive lung diseases. Interpretation Basics Result What it may suggest Low FEV1 Obstructed airways like asthma, COPD Low FVC Restricted lung volume like fibrosis Low FEV1/FVC ratio Obstructive lung disease Normal/high FEV1/FVC ratio with high FVC-Restrictive lung disease

14. Measurement of functional residual capacity and residual volume Residual volume and the functional residual capacity cannot be measured by spirometer and can be determined by three methods; Helium dilution technique Nitrogen washout method plethymography

15. Helium Dilution Technique Procedure to measure functional residual capacity Respirometer is filled with air containing a known quantity of helium. Initially, the subject breathes normally. Then, after the end of expiration, subject breathes from the respirometer. Helium from the respirometer enters the lungs and starts mixing with air in the lungs. After a few minutes of breathing, concentration of helium in the respirometer becomes equal to the concentration of helium in the lungs of the subject. After equilibrium of helium between the respirometer and lungs, concentration of helium in the respirometer is determined.

16. Cont FRC=V(C1-C2)/C2 Where C1-Initial concentration of helium in the respirometer C2-Final concentration of helium in the respirometer V-Initial volume of air in the respirometer Procedure to measure residual volume To determine functional residual capacity, the subject starts breathing with respirometer after forced expiration. To measure residual volume, the subject should start breathing from the respirometer after forced expiration.

17. Nitrogen washout method Normally, concentration of nitrogen in air is 80%.So if total quantity of nitrogen in the lungs is measured, the volume of air present in the lungs can be calculated. Procedure to measure functional residual capacity Subject is asked to breath normally, at the end of normal expiration, the subject inspires pure oxygen through a valve and expires in to a Douglas bag. This procedure is repeated for 6-7 minutes, until the nitrogen in the lungs is displaced by oxygen. Nitrogen comes to the Douglas bag.Afterwards,following factors are measured to calculate the functional residual capacity.

18. FRC=C1*V/C2 Where v-volume of air collected C1-concentration of nitrogen in the collected air C2-normal concentration of nitrogen in the air Procedure to measure residual volume To measure the functional residual capacity, the subject starts inhaling pure oxygen after the end of normal expiration and to determine the residual volume, the subject starts breathing pure oxygen after forceful expiration.

19. Plethysmography This is a technique to study the variations in the size or volume of a part of the body such as limb. Plethysmograph is an instrument used for this purpose. It is used to measure the lung volumes including residual volume. Plethysmography is based on boyle’s law of gas-which states volume of a gas is inversely proportional to pressure of a gas at constant temperature . How it works The person sits inside an airtight chamber(body box),which looks like a telephone booth. The door seals to create a closed environment. The person breathes through a mouth piece connected to a flow sensor. Initially the box is sealed and the person is instructed to breathe normally first. At a certain point, the shutter in the mouth piece closes briefly and the person is asked to make gentle panting effects These actions compress and decompress the air in the lungs, slightly changing the pressure inside the box.

20. According to boyle’s law Boyle’s law P1V1=P2V2 At constant temperature, pressure*volume is constant. As the person pants, changes in chest volume cause pressure changes in the box. The machine uses these pressure changes to calculate the volume of air trapped in the lungs , especially residual volume and functional residual capacity. Once residual volume is known, other volumes can be calculated. TLC=RV+FVC FRC=RV+ERV Plethysmography is used Diagnose restrictive lung disease Identify air tapping in obstructive lung diseases Provide more detailed information when spirometry results are inconclusive Accurately measure lung volumes in patients who cannot fully cooperate with spirometry.

21. Vital capacity-This is the maximum volume of air that can be expelled out of the lungs forcefully after a maximal inspiration. Lung volumes included inspiratory reserve volume, tidal volume and expiratory reserve volume. Normal value=4800ml Variations of vital capacity Physiological variations Sex-In females vital capacity is less than in males Body built-Vital capacity is slightly more in heavily built persons

22. 3.Posture-Vital capacity is more in standing and less in lying position 4.Atheletes-VC is more in athletes 5.Occupation-VC is decreased in people with sedentary jobs. It is increased in people who play wind musical instruments like flute. Pathological variations VC is decreased in the following respiratory diseases; Asthma,emphysema,pulmonary congestion,pneumonia,pulmonary tuberclusis,pulmonary edema.

23. Forced vital capacity This is the volume of air that can be exhaled forcefully and rapidly after maximal or deep inspiration. Normally FVC is equal to VC. However in some pulmonary diseases, FVC is decreased. Forced expiratory volume or timed vital capacity This is the volume of air, which can be expired forcefully in a given unit of time after a deep inspiration.

24. FEV1-Volume of air expired forcefully in 1 second FEV2-Volume of air expired forcefully in 2 seconds FEV3-Volume of air expired forcefully in 3 seconds Normal values FEV in persons with normal respiratory functions; FEV1-83% of total vital capacity FEV2-94% of total vital capacity FEV3-97% of total vital capacity After 3 rd second-100% of total vital capacity

25. Significance of determining the FEV Vital capacity maybe almost normal in some of the respiratory diseases but FEV has great diagnostic value, 1as it is decreased significantly in some respiratory diseases. It is very much decreased in obstructive diseases like asthma and emphysema. Respiratory minute volume This is the volume of air breathed in and out of the lungs every minute . It is the product of tidal volume and respiratory rate. Normal value is 6l

26. Maximum breathing capacity or maximum ventilation volume MBC is the maximum volume of air, which can be breathed in and out of the lungs by forceful respiration.MBC is reduced in respiratory disease. Peak expiratory flow rate This is the maximum rate at which the air can be expired after a deep inspiration. In normal persons –it is 400l/minute It is measured using the wright peak flow meter.

27. Significance of determining PEFR Determination of PEFR is useful in assessing the respiratory diseases especially to differentiate the obstructive and restrictive diseases. Generally PEFR is reduced in both diseases but more reduced in obstructive diseases than the restrictive ones. Restrictive and obstructive respiratory diseases Diseases of the respiratory tract are classified into two types; -Restrictive respiratory diseases -Obstructive respiratory diseases

28. These two types of diseases are determined by lung function tests, particularly FEV. Restrictive respiratory disease This is the abnormal respiratory condition characterized by difficulty in inspiration. Expiration is not affected. Restrictive respiratory disease maybe because of abnormality of lungs, thoracic cavity or and nervous system. Examples-Polio myelitis, Myasthenia gravis, Flail chest, pleural effusion ,spinal cord disease.

29. Obstructive respiratory disease This is the abnormal respiratory condition characterized by difficulty in expiration. Examples Lower respiratory tract-Asthma, chronic bronchitis, emphysema, cystic fibrosis Upper respiratory tract- Laryngotracheobronchitis ,epiglottis,tumors,severe cough and cold with phlegm.

30. Lung function tests Spirometry –as discussed above Lung volume measurement This measures static lung volumes that spirometry cannot like residual volume and methods used are body plethysmography ,gas dilution(helium or nitrogen) also discussed above. Diffusion capacity test Arterial blood gas Pulse oximetry Exercise testing Bronchoprovocation testing Maximal inspiratory and expiratory pressures Peak flow measurement Fractional Exhaled nitric oxide test( FeNO )

31. Exercise Testing Measures respiratory and cardiovascular function during exercise Types: 6-minute walk test Cardiopulmonary exercise testing Used for; Unexplained breathlessness Assessing fitness for surgery Evaluation of interstitial lung disease or pulmonary hypertension

32. Diffusion Capacity Test(DLCO) This measures how well gases like oxygen move from the lungs into blood How it works You inhale a small amount of carbon monoxide and the amount exhaled is measured to see how much was absorbed. It is used to diagnose -Pulmonary fibrosis -Emphysema -Pulmonary hypertension -Interstitial lung disease

33. Arterial Blood Gas(ABG) Test This test is a crucial investigation that measures the levels of oxygen, carbon dioxide and pH balance in arterial blood. It gives a picture of how well your lungs are oxygenating blood and removing carbon dioxide and how well it is regulating ph. Blood is usually drawn from an artery, commonly the radial artery in the wrist. It is more painful than venous blood draws since arteries are deeper and more sensitive The sample must be analyzed quickly, often within minutes

34. Why is ABG Done It is done to evaluate: Oxygenation status( Hyoxemia ) Ventilation(how well CO2 is being removed) Acid –base balance(Acidosis/alkalosis) Effectiveness of oxygen therapy Lung disease like COPD,asthma,pneumonia Metabolic conditions eg diabetic ketoacidosis

35. How to interpret ABG PH <7.35-Acidosis >7.45-Alkalosis Check PaCO2 High PaCO2-Respiratory acidosis(hypoventilation) Low PaCO2-Respiratory alkalosis(hyperventilation) Check HCO3- High HCO3- -metabolic alkalosis Low HCO3- -metabolic acidosis Match disturbance If ph. is low and PaCO2 is high-Respiratory acidosis If ph. is high and HCO3- is high-Metabolic alkalosis

36. Fractional Exhaled Nitric Oxide( FeNO ) FeNO is a quick, on-invasive breath test that measures the amount of nitric oxide in your breath to detect and monitor airway inflammation, often associated with asthma. A high level of nitric oxide indicates inflammation, which can help confirm asthma diagnosis, identify if the asthma is likely to respond to certain treatments, and assess the effectiveness of treatment over time. How it works -You breath into a special device that measures the nitric oxide in breath, typically in parts per billion(ppb) -The test is quick and painless, and usually requires you to slowly exhale or sometimes inhale and exhale in a specific way while forming a tight seal around a mouth piece. -The results are used along with other clinical information, such as symptoms, physical exam, to help diagnose and manage conditions like asthma. -High FeNO level(generally over 25ppb in adults) can indicate inflammation in the airways and suggest eisonophilic asthma, which is more likely to respond to inhaled corticosteroids.

37. FeNO in preoperative care While not a standard part of routine preoperative assessment, FeNO can have important uses in select patients, particularly those with known asthma or airway hyper reactivity. Uses of FeNO in preoperative care Assessing asthma control before surgery Elevated FeNO suggests uncontrolled eisonophilic airway inflammation. It helps determine whether asthma is well-managed or if treatment needs adjustment before surgery. Well-controlled asthma lowers the risk of bronchospasms during anesthesia, postoperative respiratory complications. Predicting risk of perioperative respiratory complications High FeNO levels may indicate an increased risk of laryngospasm or bronchospasm under anesthesia, postoperative wheezing, hypoxia, or need for bronchodilators.

38. Differences between obstructive and restrictive lung diseases Feature Obstructive lung disease Restrictive lung disease Main problem Airflow limitation due to narrowed airways(difficulty exhaling) Reduced lung expansion(Difficulty inhaling fully) Mechanism Increased airway resistance Decreased lung or chest wall compliance Lung volumes Increased residual volume and total lung capacity Reduced total lung capacity, residual volume, forced vital capacity. FEV1 It is markedly reduced Reduced(mild to moderate) FEV1/FVC ratio Reduced or normal Reduced Diffusion capacity Normal or reduced esp in emphysema Reduced esp in interstitial lung disease Common symptoms Wheezing,prolonged expiration,dyspnea,cough Dyspnea,shallow breathing,dry cough Common examples Asthma,COPD,Cystic fibrosis Pulmonary fibrosis,sarcodiosis,obesity Response to bronchodilators Often improves esp in asthma No significant improvement

39. Differences between asthma and COPD Feature Asthma COPD Defination Chronic inflammatory disease of the airways causing reversible airflow obstruction Chronic, progressive disease causing irreversible or partially reversible airflow limitation Age of onset Usually childhood or young adulthood Usually over 40 years Cause Often triggered by allergens,exercise,cold air or infections Primarily caused by smoking and long term exposure to irritants Airflow limitation Reversible with bronchodilators or naturally Not fully reversible, progressive Symptoms Episodic wheezing, chest tightness, shortness of breath, esp at night or early morning, cough Chronic cough,sputum,progressive dyspnea,wheezing.Symptoms persist and worsen over time Lung function Improves significantly with bronchodilators Limited response to bronchodilators FEV1/FVC ratio Reduced during attacks,may normalize between episodes Persistently < 70% post bronchodilator Smoking May or maynot be present Almost always present Inflammation type Eisinophilic (allergic driven) Neutrophilic

40. Lung resistance This is the resistance to airflow within the airways mainly in the bronchi and bronchioles. In normal lungs it is low while high in asthma due to bronchoconstriction, inflammation and COPD due to airway narrowing, mucus loss, loss of elasticity but normal or slightly increased in restrictive lung diseases. Lung resistance is measured by body plethysmography It helps to differentiate between obstructive and restrictive lung diseases and also to monitor treatment response in asthma and COPD.

41. Factors affecting lung resistance Age-In children there is higher airway resistance due to smaller airway diameter and less developed alveoli while in older adults airway resistance may slightly increase with age due to loss of elastic recoil, decreased airway support. Altitude-In healthy people, airway resistance may slightly decrease due to thinner air while in asthmatics, high altitude may trigger bronchospasm due to cold dry air and low oxygen. Airway diameter-The narrower the diameter of the airway, the more resistance. Lung volume-Increase in lung volume during deep inhalation decreases lung resistance. Inflammation-Increase in inflammation increases resistance Airway smooth muscle contraction increases resistance. Turbulent airflow increases resistance

42. Factors associated with airway obstruction Airway obstruction occurs when airflow is limited or blocked, making it difficult to breath. This can be partial or complete, acute or chronic, and may affect large or small airways. Acute causes Foreign objects-These may be ingested or aspirated items like food, small toys or buttons. Infections-Viral infections like croup and epiglottitis or bacterial infections leading to abscesses. Trauma-Direct injury to the neck or airway from blunt force or penetrating wounds. Anaphylaxis-A severe allergic reaction that causes swelling of the airways. Swelling/edema-Inflammation from injury, allergic reactions or infections, which narrows the airway.

43. Chronic causes Chronic obstructive pulmonary disease-A group of lung diseases that include emphysema and chronic bronchitis, leading to airflow limitation. Asthma-This is characterized by inflammation, swelling and muscle spasms in the airways, often leading to excessive mucus. Obstructive sleep apnea-This is a condition where the airway collapses repeatedly during sleep. Tumors-Growths in or around the airway, such as cancers,lipomas or polyps. Anatomical issues-Structural problems like a deviated septum, nasal polyps or enlarged tonsils. Smoking-Can cause inflammation, airway remodeling and is significant risk factor for COPD

44. Physiological factors affecting the normal values of pulmonary function tests. Age-Lung function peaks in early adulthood between 20-25 years then declines gradually. Decrease in elastic recoil leads to decreased FEV,FVC and increased RV in older adults. Sex-Males have larger lungs therefore higher values of FVC,TLC,FEV1 while females have relatively smaller airways and lung volumes. Height-Taller individuals have larger thoracic cavities which leads to higher FVC,FEV1,TLC. Race-Blacks, Asians and Hispanic individuals often have lower lung volumes by about 10-15% compared to Caucasians of the same age and height. Obesity-Moderate obesity may reduce FRC and ERV, severe obesity decreases TLC,FVC and lung compliance. Altitude-Chronic high altitude exposure may increase DLCO due to increased capillary blood volume.

45. Cont. Pregnancy-It causes a decrease in several values due to mechanical effect of the enlarging uterus and hormonal changes, specifically FVC,FEV1,FEF and PEFR generally decrease. Posture-Sitting vs. standing affect lung volume slightly. Supine position reduces FRC and ERV especially in obese or pregnant patients. Physical activity-Athletes may have slightly increased lung volumes and better airflow. Environmental factors-Long term exposure to air pollution or smoking can affect normal values even in asymptomatic people.

46. Factors associated with oxygen release in tissues Metabolic factors Low oxygen partial pressure-Tissues actively use oxygen creating a low partial pressure that drives oxygen release from blood. Increased CO2 and PH-Metabolic activity produces carbon dioxide and acid and the resulting lower ph. in the tissues decreases hemoglobin’s affinity for oxygen, promoting its release. Increased temperature-Higher temperatures in actively working tissues favor the release of oxygen, promoting from hemoglobin. 2,3-Bisphosphoglycerate-Increased levels of this compound in red blood cells enhance oxygen unloading to its tissues. Other factors Oxygen-hemoglobin dissociation curve-The curve shifts to the right in response to the factors above, meaning that at any given oxygen partial pressure, more oxygen will be released.

47. Cont. Diffusion gradient-A steep concentration gradient between the oxygen in the capillary blood and the tissues themselves is essential for efficient oxygen transfer. Capillary and cellular factors-The size of the capillary, the diffusin distance from the capillary to the cell, and the rate at which cells use oxygen also influence oxygen extraction.