Pulmonary Function Tests

Overview

Definition

• A group of tests providing objective data on an individual’s lung function, including:
  • Lung volumes
  • Rate of airflow
  • Gas exchange Gas exchange Human cells are primarily reliant on aerobic metabolism. The respiratory system is involved in pulmonary ventilation and external respiration, while the circulatory system is responsible for transport and internal respiration. Pulmonary ventilation (breathing) represents movement of air into and out of the lungs. External respiration, or gas exchange, is represented by the O2 and CO2 exchange between the lungs and the blood. Gas Exchange capacity
• Tests must be interpreted within the context of clinical history and physical examination.
• The results can suggest different categories of respiratory disease.

Examples

• Spirometry before and after a bronchodilator
• Lung volume
• Quantitation of diffusion Diffusion The tendency of a gas or solute to pass from a point of higher pressure or concentration to a point of lower pressure or concentration and to distribute itself throughout the available space. Diffusion, especially facilitated diffusion, is a major mechanism of biological transport. Peritoneal Dialysis and Hemodialysis capacity

Indications

• To look for evidence of specific pulmonary pathology in the presence of respiratory symptoms
• To assess the progression of known lung disease
• To monitor the efficacy of treatment
• To assess fitness preoperatively, especially in cases of procedures involving the lungs Lungs Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. Lungs: Anatomy and heart
• To monitor for side effects of medications (e.g., amiodarone Amiodarone An antianginal and class III antiarrhythmic drug. It increases the duration of ventricular and atrial muscle action by inhibiting potassium channels and voltage-gated sodium channels. There is a resulting decrease in heart rate and in vascular resistance. Pulmonary Fibrosis)
• To monitor for the development of lung disease in individuals with harmful exposures 
• To assess the degree of disability Disability Determination of the degree of a physical, mental, or emotional handicap. The diagnosis is applied to legal qualification for benefits and income under disability insurance and to eligibility for social security and workman’s compensation benefits. ABCDE Assessment

Contraindications Contraindications A condition or factor associated with a recipient that makes the use of a drug, procedure, or physical agent improper or inadvisable. Contraindications may be absolute (life threatening) or relative (higher risk of complications in which benefits may outweigh risks). Noninvasive Ventilation

• Recent myocardial infarction Myocardial infarction MI is ischemia and death of an area of myocardial tissue due to insufficient blood flow and oxygenation, usually from thrombus formation on a ruptured atherosclerotic plaque in the epicardial arteries. Clinical presentation is most commonly with chest pain, but women and patients with diabetes may have atypical symptoms. Myocardial Infarction
• Untreated pulmonary embolism Pulmonary Embolism Pulmonary embolism (PE) is a potentially fatal condition that occurs as a result of intraluminal obstruction of the main pulmonary artery or its branches. The causative factors include thrombi, air, amniotic fluid, and fat. In PE, gas exchange is impaired due to the decreased return of deoxygenated blood to the lungs. Pulmonary Embolism
• Ascending aortic aneurysm Ascending aortic aneurysm Thoracic Aortic Aneurysms (> 6 cm dilation)
• Pneumothorax Pneumothorax A pneumothorax is a life-threatening condition in which air collects in the pleural space, causing partial or full collapse of the lung. A pneumothorax can be traumatic or spontaneous. Patients present with a sudden onset of sharp chest pain, dyspnea, and diminished breath sounds on exam. Pneumothorax
• Recent thoracic surgery Thoracic Surgery Basic surgical intervention in the thoracic cavity has the primary goal of alleviating any malady that mechanically affects the function of the heart and lungs, which can be secondary to underlying pathologies or, most commonly, trauma. Interventions include tube thoracostomy, thoracentesis, and emergency thoracotomy. Thoracic Surgery
• Eye surgery (< 1 week)
• Hemoptysis Hemoptysis Hemoptysis is defined as the expectoration of blood originating in the lower respiratory tract. Hemoptysis is a consequence of another disease process and can be classified as either life threatening or non-life threatening. Hemoptysis can result in significant morbidity and mortality due to both drowning (reduced gas exchange as the lungs fill with blood) and hemorrhagic shock. Hemoptysis
• Angina

Lung Volumes

Lung volumes are measured by:

• Body plethysmography:
  • The most accurate technique
  • Based on Boyle’s law: P1 x V1 = P2 x V2 → the product of pressure (P) and volume (V) is constant for any gas regardless of the container holding the gas
  • The individual sits in a sealed box and pants against a closed valve.
  • Changes in pressure and volume in the box are measured and can be used to extrapolate volume and pressure inside the lungs Lungs Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. Lungs: Anatomy.
• Inert gas dilution:
  • The individual inhales an inert tracer gas not absorbed by the lungs Lungs Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. Lungs: Anatomy.
  • The exhaled gas is collected and the dilution is calculated, giving estimates of lung volume.
• Nitrogen Nitrogen An element with the atomic symbol n, atomic number 7, and atomic weight [14. 00643; 14. 00728]. Nitrogen exists as a diatomic gas and makes up about 78% of the earth’s atmosphere by volume. It is a constituent of proteins and nucleic acids and found in all living cells. Urea Cycle washout:
  • 80% of lung volume is nitrogen Nitrogen An element with the atomic symbol n, atomic number 7, and atomic weight [14. 00643; 14. 00728]. Nitrogen exists as a diatomic gas and makes up about 78% of the earth’s atmosphere by volume. It is a constituent of proteins and nucleic acids and found in all living cells. Urea Cycle. 
  • The individual inhales 100% oxygen through a 1-way tube, “washing out” the nitrogen Nitrogen An element with the atomic symbol n, atomic number 7, and atomic weight [14. 00643; 14. 00728]. Nitrogen exists as a diatomic gas and makes up about 78% of the earth’s atmosphere by volume. It is a constituent of proteins and nucleic acids and found in all living cells. Urea Cycle from the lungs Lungs Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. Lungs: Anatomy.
  • Washed-out nitrogen Nitrogen An element with the atomic symbol n, atomic number 7, and atomic weight [14. 00643; 14. 00728]. Nitrogen exists as a diatomic gas and makes up about 78% of the earth’s atmosphere by volume. It is a constituent of proteins and nucleic acids and found in all living cells. Urea Cycle volume is measured and estimates lung volume.
  • Measures functional residual capacity Functional residual capacity The volume of air remaining in the lungs at the end of a normal, quiet expiration. It is the sum of the residual volume and the expiratory reserve volume. Common abbreviation is frc. Ventilation: Mechanics of Breathing (FRC)

Lung volumes:

• Tidal volume Tidal volume The volume of air inspired or expired during each normal, quiet respiratory cycle. Common abbreviations are tv or V with subscript t. Ventilation: Mechanics of Breathing (TV):
  • Volume of air inhaled or exhaled during regular Regular Insulin respiration Respiration The act of breathing with the lungs, consisting of inhalation, or the taking into the lungs of the ambient air, and of exhalation, or the expelling of the modified air which contains more carbon dioxide than the air taken in. Nose Anatomy (External & Internal) at rest
  • Normal value: approximately 500 mL
• Inspiratory reserve volume Inspiratory reserve volume The extra volume of air that can be inspired with maximal effort after reaching the end of a normal, quiet inspiration. Common abbreviation is irv. Ventilation: Mechanics of Breathing (IRV): volume of air maximally inhaled above normal tidal inspiration Inspiration Ventilation: Mechanics of Breathing
• Expiratory reserve volume Expiratory reserve volume The extra volume of air that can be expired with maximum effort beyond the level reached at the end of a normal, quiet expiration. Common abbreviation is erv. Ventilation: Mechanics of Breathing (ERV): volume of air maximally exhaled after normal tidal expiration Expiration Ventilation: Mechanics of Breathing
• Residual volume Residual volume The volume of air remaining in the lungs at the end of a maximal expiration. Common abbreviation is rv. Ventilation: Mechanics of Breathing (RV): amount of air remaining in the lungs Lungs Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. Lungs: Anatomy after maximal exhalation

Lung capacities:

• Total lung capacity Total lung capacity The volume of air contained in the lungs at the end of a maximal inspiration. It is the equivalent to each of the following sums: vital capacity plus residual volume; inspiratory capacity plus functional residual capacity; tidal volume plus inspiratory reserve volume plus functional residual capacity; or tidal volume plus inspiratory reserve volume plus expiratory reserve volume plus residual volume. Ventilation: Mechanics of Breathing (TLC): 
  • Volume of air present in the lungs Lungs Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. Lungs: Anatomy after maximum deep inspiration Inspiration Ventilation: Mechanics of Breathing
  • The sum of all volumes: TLC = IRV + TV + ERV + RV
• Vital capacity Vital capacity The volume of air that is exhaled by a maximal expiration following a maximal inspiration. Ventilation: Mechanics of Breathing (VC):
  • Maximum volume of air exhaled after maximum deep inspiration Inspiration Ventilation: Mechanics of Breathing
  • VC = IRV + TV + ERV or VC = TLC – RV
• Inspiratory capacity Inspiratory capacity The maximum volume of air that can be inspired after reaching the end of a normal, quiet expiration. It is the sum of the tidal volume and the inspiratory reserve volume. Common abbreviation is ic. Ventilation: Mechanics of Breathing ( IC IC Inhaled Anesthetics):
  • Maximum volume of air inspired after normal tidal expiration Expiration Ventilation: Mechanics of Breathing
  • IC IC Inhaled Anesthetics = TV + IRV
• Expiratory capacity (EC):
  • Maximum volume of air expired after normal tidal inspiration Inspiration Ventilation: Mechanics of Breathing
  • EC = TV+ ERV
• FRC: volume of air remaining in the lungs Lungs Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. Lungs: Anatomy after normal tidal expiration Expiration Ventilation: Mechanics of Breathing

Spirometry

Spirometry records the volume of air moving in and out of an individual’s lungs Lungs Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. Lungs: Anatomy.

• The most frequently used measure of pulmonary function
• The individual is instructed to maximally inhale and forcibly exhale through a spirometer.
• Most commonly used measures include:
  • Forced vital capacity Vital capacity The volume of air that is exhaled by a maximal expiration following a maximal inspiration. Ventilation: Mechanics of Breathing (FVC): maximum volume of air forcefully exhaled after a maximal inspiration Inspiration Ventilation: Mechanics of Breathing
  • Forced expiratory volume in 1 second (FEV1): volume of air exhaled during the initial second of the FVC maneuver
  • The ratio of FEV1/FVC: 
    • Describes the proportion of expired air exhaled in the 1st second
    • Normal value > 70%
    • The ratio is decreased in obstructive lung disease because the airways collapse on expiration Expiration Ventilation: Mechanics of Breathing.
  • PEFR (peak expiratory flow rate Flow rate maximum flow the ventilator will deliver a set tidal volume in liters per minute Invasive Mechanical Ventilation):
    • Maximal speed of expiration Expiration Ventilation: Mechanics of Breathing
    • Occurs within the 1st 200 milliseconds from the onset of forceful expiration Expiration Ventilation: Mechanics of Breathing
    • Typically used to assess airway Airway ABCDE Assessment obstruction in individuals with asthma Asthma Asthma is a chronic inflammatory respiratory condition characterized by bronchial hyperresponsiveness and airflow obstruction. The disease is believed to result from the complex interaction of host and environmental factors that increase disease predisposition, with inflammation causing symptoms and structural changes. Patients typically present with wheezing, cough, and dyspnea. Asthma
• Flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure volume loop: the graphic representation of flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure as a function of volume:
  • The volume is represented on the x-axis and the flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure on the y-axis.
  • The expiratory limb is usually represented as positive deflection. 
  • In obstructive lung diseases:
    • The expiratory flows are decreased.
    • The end-inspiratory and end-expiratory volumes are increased due to air trapping.
  • In restrictive lung diseases:
    • The lungs are “stiffer,” causing decreased volumes.
    • The flows are maintained.

• Fixed airway Airway ABCDE Assessment obstruction: 
  • Constant limitation of flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure during inspiration Inspiration Ventilation: Mechanics of Breathing and expiration Expiration Ventilation: Mechanics of Breathing
  • The flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure curves “flatten” in both inspiration Inspiration Ventilation: Mechanics of Breathing and expiration Expiration Ventilation: Mechanics of Breathing.
  • Examples: tracheal tumor Tumor Inflammation or stricture Stricture Primary Sclerosing Cholangitis
• Variable Variable Variables represent information about something that can change. The design of the measurement scales, or of the methods for obtaining information, will determine the data gathered and the characteristics of that data. As a result, a variable can be qualitative or quantitative, and may be further classified into subgroups. Types of Variables extrathoracic obstruction:
  • Reduction in flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure is greater during inspiration Inspiration Ventilation: Mechanics of Breathing. 
  • The flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure curve is flat during inspiration Inspiration Ventilation: Mechanics of Breathing.
  • Positive pressure in the airway Airway ABCDE Assessment during expiration Expiration Ventilation: Mechanics of Breathing decreases obstruction. 
  • Examples: vocal cord palsy Palsy paralysis of an area of the body, thus incapable of voluntary movement Cranial Nerve Palsies, obstructive sleep apnea Sleep apnea Repeated cessation of breathing for > 10 seconds during sleep and results in sleep interruption, fatigue, and daytime sleepiness. Obstructive Sleep Apnea
• Variable Variable Variables represent information about something that can change. The design of the measurement scales, or of the methods for obtaining information, will determine the data gathered and the characteristics of that data. As a result, a variable can be qualitative or quantitative, and may be further classified into subgroups. Types of Variables intrathoracic obstruction:
  • Reduction inflow is greater during expiration Expiration Ventilation: Mechanics of Breathing. 
  • The flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure curve is flat during expiration Expiration Ventilation: Mechanics of Breathing.
  • Lower pleural pressure around the airway Airway ABCDE Assessment decreases obstruction during inspiration Inspiration Ventilation: Mechanics of Breathing. 
  • Examples: tracheomalacia Tracheomalacia A congenital or acquired condition of underdeveloped or degeneration of cartilage in the trachea. This results in a floppy tracheal wall making patency difficult to maintain. It is characterized by wheezing and difficult breathing. Laryngomalacia and Tracheomalacia, tumor Tumor Inflammation of bronchus

Diffusing Capacity of the Lung for Carbon Monoxide (DLCO)

• Used as a measure of gas exchange Gas exchange Human cells are primarily reliant on aerobic metabolism. The respiratory system is involved in pulmonary ventilation and external respiration, while the circulatory system is responsible for transport and internal respiration. Pulmonary ventilation (breathing) represents movement of air into and out of the lungs. External respiration, or gas exchange, is represented by the O2 and CO2 exchange between the lungs and the blood. Gas Exchange
• Measured by the “single breath” method:
  • The individual inspires a diluted mixture of carbon monoxide Carbon monoxide Carbon monoxide (CO). A poisonous colorless, odorless, tasteless gas. It combines with hemoglobin to form carboxyhemoglobin, which has no oxygen carrying capacity. The resultant oxygen deprivation causes headache, dizziness, decreased pulse and respiratory rates, unconsciousness, and death. Carbon Monoxide Poisoning (CO), holds their breath for 10 seconds, and then exhales into a sensor. 
  • The amount of exhaled CO is measured by infrared analysis.

• Demonstrates the ability of the lung to transport inhaled gas from the alveoli Alveoli Small polyhedral outpouchings along the walls of the alveolar sacs, alveolar ducts and terminal bronchioles through the walls of which gas exchange between alveolar air and pulmonary capillary blood takes place. Acute Respiratory Distress Syndrome (ARDS) to the blood
• Diffusion Diffusion The tendency of a gas or solute to pass from a point of higher pressure or concentration to a point of lower pressure or concentration and to distribute itself throughout the available space. Diffusion, especially facilitated diffusion, is a major mechanism of biological transport. Peritoneal Dialysis and Hemodialysis of gas across the alveolar membrane depends on:
  • The surface area of alveolar membrane
  • The diffusion Diffusion The tendency of a gas or solute to pass from a point of higher pressure or concentration to a point of lower pressure or concentration and to distribute itself throughout the available space. Diffusion, especially facilitated diffusion, is a major mechanism of biological transport. Peritoneal Dialysis and Hemodialysis constant of the specific gas
  • The pressure gradient Pressure gradient Vascular Resistance, Flow, and Mean Arterial Pressure of gas across the membrane
• CO is the ideal gas for the study:
  • Very high affinity for Hb Hb The oxygen-carrying proteins of erythrocytes. They are found in all vertebrates and some invertebrates. The number of globin subunits in the hemoglobin quaternary structure differs between species. Structures range from monomeric to a variety of multimeric arrangements. Gas Exchange
  • CO bound to Hb Hb The oxygen-carrying proteins of erythrocytes. They are found in all vertebrates and some invertebrates. The number of globin subunits in the hemoglobin quaternary structure differs between species. Structures range from monomeric to a variety of multimeric arrangements. Gas Exchange does not contribute to the partial pressure Partial pressure The pressure that would be exerted by one component of a mixture of gases if it were present alone in a container. Gas Exchange of CO in blood.
  • The pressure gradient Pressure gradient Vascular Resistance, Flow, and Mean Arterial Pressure of CO across the alveolar membrane is constant.  
• Factors decreasing DLCO:
  • Anemia Anemia Anemia is a condition in which individuals have low Hb levels, which can arise from various causes. Anemia is accompanied by a reduced number of RBCs and may manifest with fatigue, shortness of breath, pallor, and weakness. Subtypes are classified by the size of RBCs, chronicity, and etiology. Anemia: Overview and Types
  • Lung fibrosis Fibrosis Any pathological condition where fibrous connective tissue invades any organ, usually as a consequence of inflammation or other injury. Bronchiolitis Obliterans
  • Emphysema Emphysema Enlargement of air spaces distal to the terminal bronchioles where gas-exchange normally takes place. This is usually due to destruction of the alveolar wall. Pulmonary emphysema can be classified by the location and distribution of the lesions. Chronic Obstructive Pulmonary Disease (COPD)
• Factors increasing DLCO:
  • Asthma Asthma Asthma is a chronic inflammatory respiratory condition characterized by bronchial hyperresponsiveness and airflow obstruction. The disease is believed to result from the complex interaction of host and environmental factors that increase disease predisposition, with inflammation causing symptoms and structural changes. Patients typically present with wheezing, cough, and dyspnea. Asthma
  • Exercise
  • Pulmonary hemorrhage
  • Polycythemia Polycythemia An increase in the total red cell mass of the blood. Renal Cell Carcinoma

Clinical Relevance

The following conditions are diagnosed by pulmonary function tests:

• Obstructive lung disease: a category of respiratory disease characterized by airway Airway ABCDE Assessment obstruction and air trapping in the lungs Lungs Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. Lungs: Anatomy. Obstructive lung disease is marked by high lung volumes (i.e., increased FRC, RV, and TLC). The pulmonary function test shows a predominant decrease in FEV1, leading to a decreased FEV1/FVC ratio. Emphysema Emphysema Enlargement of air spaces distal to the terminal bronchioles where gas-exchange normally takes place. This is usually due to destruction of the alveolar wall. Pulmonary emphysema can be classified by the location and distribution of the lesions. Chronic Obstructive Pulmonary Disease (COPD), chronic bronchitis Chronic bronchitis A subcategory of chronic obstructive pulmonary disease. The disease is characterized by hypersecretion of mucus accompanied by a chronic (more than 3 months in 2 consecutive years) productive cough. Infectious agents are a major cause of chronic bronchitis. Rhinovirus, asthma Asthma Asthma is a chronic inflammatory respiratory condition characterized by bronchial hyperresponsiveness and airflow obstruction. The disease is believed to result from the complex interaction of host and environmental factors that increase disease predisposition, with inflammation causing symptoms and structural changes. Patients typically present with wheezing, cough, and dyspnea. Asthma, and bronchiectasis Bronchiectasis Bronchiectasis is a chronic disease of the airways that results from permanent bronchial distortion. This results from a continuous cycle of inflammation, bronchial damage and dilation, impaired clearance of secretions, and recurrent infections. Bronchiectasis are types of obstructive lung disease.
• Restrictive lung disease: a group of lung diseases characterized by increased stiffness of the lung tissue due to interstitial inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation and fibrosis Fibrosis Any pathological condition where fibrous connective tissue invades any organ, usually as a consequence of inflammation or other injury. Bronchiolitis Obliterans. The lung volumes are characteristically decreased (i.e., decreased FVC and TLC). The pulmonary function test shows an increase in the FEV1/FVC ratio because both FEV1 and FVC are symmetrically decreased. Idiopathic Idiopathic Dermatomyositis pulmonary fibrosis Fibrosis Any pathological condition where fibrous connective tissue invades any organ, usually as a consequence of inflammation or other injury. Bronchiolitis Obliterans, lung disease due to scleroderma Scleroderma Scleroderma (systemic sclerosis) is an autoimmune condition characterized by diffuse collagen deposition and fibrosis. The clinical presentation varies from limited skin involvement to diffuse involvement of internal organs. Scleroderma, systemic lupus erythematosus Systemic lupus erythematosus Systemic lupus erythematosus (SLE) is a chronic autoimmune, inflammatory condition that causes immune-complex deposition in organs, resulting in systemic manifestations. Women, particularly those of African American descent, are more commonly affected. Systemic Lupus Erythematosus, asbestosis Asbestosis A form of pneumoconiosis caused by inhalation of asbestos fibers which elicit potent inflammatory responses in the parenchyma of the lung. The disease is characterized by interstitial fibrosis of the lung, varying from scattered sites to extensive scarring of the alveolar interstitium. Pneumoconiosis, and other occupational lung diseases are examples of restrictive lung disease.