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Pulmonary Diagnostic Tests FEV/vC >LLN Yes No VC: LLN VC > LLN No Yes No TLC > LLN TLC > LLN Yes No Yes Yes No Normal Restriction Obstruaion Mixed defea DLco > LLN DLco > LLN DTco > LLN Yes No Yes No Yes No Normal PV CW and NM ILD Asthma Emphysema disorders disorders Pneumonitis CB FIGURE l.Asimplifiedalgorithmsuchasthismaybeusedtoassesslungfunctioninclinical practice. ltpresentsclassicpatternsforvariouspulmonarydisorders.Asin any surh diagram, patients may or may not present with the classic patterns, depending on their illnesses, severity, and lung function before disease onset (for example, did J they start with a vital capacity [VC] close to the upper or lower limit of normal ILLN]?). Ihe decisions about how far to follow this diagram are clinical and will vary depending on the questions being asked and the clinical information available at the time of testing.The FEV,/VC ratio and VC should be considered first.Total lung capacity (ILC) is l necessary to conlirm or exclude the presence of a restrictive defect when VC is below the LLN. Ihe algorithm also includes DLCo measurement with the predicted value adjusted

FIGURE l.Asimplifiedalgorithmsuchasthismaybeusedtoassesslungfunctioninclinical practice. ltpresentsclassicpatternsforvariouspulmonarydisorders.Asin any surh diagram, patients may or may not present with the classic patterns, depending on their illnesses, severity, and lung function before disease onset (for example, did J they start with a vital capacity [VC] close to the upper or lower limit of normal ILLN]?). Ihe decisions about how far to follow this diagram are clinical and will vary depending on the questions being asked and the clinical information available at the time of testing.The FEV,/VC ratio and VC should be considered first.Total lung capacity (ILC) is l necessary to conlirm or exclude the presence of a restrictive defect when VC is below the LLN. Ihe algorithm also includes DLCo measurement with the predicted value adjusted upper airway obstruction. CB = chronic bronchitis; CW= chest wall; ILD = interstitial lung diseases; NM = neuromuscular; PV= pulmonary vascular. :

necessary to conlirm or exclude the presence of a restrictive defect when VC is below the LLN. Ihe algorithm also includes DLCo measurement with the predicted value adjusted upper airway obstruction. CB = chronic bronchitis; CW= chest wall; ILD = interstitial lung diseases; NM = neuromuscular; PV= pulmonary vascular. : the European Respiratory Society define a reduced FEVr/FVC The florn, volume loop is a graphic representation of max- ratio as being below the lower limit of normal, whereas the imally forced inspiratory and expiratory flow (on the Y axis) Global Initiative for Chronic Obstructive Lung Disease del'ines against volume (on the X axis). The shape of the spirometric it as below 0.70. An increase from baseline in FEV,, FVC, or flow volume loop is also useful in differentiating obstructive both of at least 12'7, and at least 200 mL indicates a positive from restrictive patterns (Figure 2). bronchodilator response (reversibility). TLC is normal or even t(Ev P0lxrs increased in pure obstructive disease. Elevation of TLC and residual volume (120'2, or greater ofpredicted) can be observed . The purpose of pulmonary function testing interpreta in obstruction and generally indicates hyperinflation and air tion is to classi8z abnormal results as either obstructive trapping, a common pattern in severe COPD and asthma. or restrictive and to assess the severity of impairment. If FEV, or FVC is reduced and the FEVr/FVC ratio is 0.70 . The FEVr/FVC ratio is the primary measurement that or greater, then the pattern may be interpreted as restrictive, defines obstructive disease, and total lung capacity is but measurement of TLC is needed to confirm this. If TLC is the primary measurement used to confirm restrictive less than 80% of predicted (or the lower limit of normal), a disease. restrictive pattern is present. Some patients present with coexisting obstructive and 6-Minute WalkTest restrictive pulmonary disorders, such as COPD and interstitial The 6 minute walk test provides a valid and reliable measure lung disease. In these cases, a low FEV,/FVC ratio (obstructive) ment of exercise capacity in patients with lung disease. and a low TLC (restrictive) are both present. Patients walk at their own pace along a course for 6 minutes, Dlco is reduced in conditions in which functioning and the total distance walked is recorded. Lower 6 minute alveolar capillary units are destroyed (COPD), infiltrated (inter- walk test distances correlate with increased mortality in sev- stitial lung diseases), or removed (1ung resection). and in which eral lung diseases, including COPD, interstitial lung disease. their function is compromised (pulmonary parenchymal and and pulmonary arterial hypertension. Serial 6 minute walk vascular disorders). Conditions that increase pulmonary capil testing may be used to assess response to therapy in patients lary blood volume, such as pulmonary alveolar hemorrhage, with chronic respiratory disorders, especially pulmonary arte left to-right shunt, or asthma, can cause an elevation in Dr.co. rial hypertension.

the European Respiratory Society define a reduced FEVr/FVC The florn, volume loop is a graphic representation of max- ratio as being below the lower limit of normal, whereas the imally forced inspiratory and expiratory flow (on the Y axis) Global Initiative for Chronic Obstructive Lung Disease del'ines against volume (on the X axis). The shape of the spirometric it as below 0.70. An increase from baseline in FEV,, FVC, or flow volume loop is also useful in differentiating obstructive both of at least 12'7, and at least 200 mL indicates a positive from restrictive patterns (Figure 2). bronchodilator response (reversibility). TLC is normal or even t(Ev P0lxrs increased in pure obstructive disease. Elevation of TLC and residual volume (120'2, or greater ofpredicted) can be observed . The purpose of pulmonary function testing interpreta in obstruction and generally indicates hyperinflation and air tion is to classi8z abnormal results as either obstructive trapping, a common pattern in severe COPD and asthma. or restrictive and to assess the severity of impairment. If FEV, or FVC is reduced and the FEVr/FVC ratio is 0.70 . The FEVr/FVC ratio is the primary measurement that or greater, then the pattern may be interpreted as restrictive, defines obstructive disease, and total lung capacity is but measurement of TLC is needed to confirm this. If TLC is the primary measurement used to confirm restrictive less than 80% of predicted (or the lower limit of normal), a disease. restrictive pattern is present. Some patients present with coexisting obstructive and 6-Minute WalkTest restrictive pulmonary disorders, such as COPD and interstitial The 6 minute walk test provides a valid and reliable measure lung disease. In these cases, a low FEV,/FVC ratio (obstructive) ment of exercise capacity in patients with lung disease. and a low TLC (restrictive) are both present. Patients walk at their own pace along a course for 6 minutes, Dlco is reduced in conditions in which functioning and the total distance walked is recorded. Lower 6 minute alveolar capillary units are destroyed (COPD), infiltrated (inter- walk test distances correlate with increased mortality in sev- stitial lung diseases), or removed (1ung resection). and in which eral lung diseases, including COPD, interstitial lung disease. their function is compromised (pulmonary parenchymal and and pulmonary arterial hypertension. Serial 6 minute walk vascular disorders). Conditions that increase pulmonary capil testing may be used to assess response to therapy in patients lary blood volume, such as pulmonary alveolar hemorrhage, with chronic respiratory disorders, especially pulmonary arte left to-right shunt, or asthma, can cause an elevation in Dr.co. rial hypertension. 2

Pulmonary Diagnostic Tests Expiratory Expiratory Prebronchodilator Flow Flow -- - - - - Postbronchodilator TLC RV Volume TLC RV Volume lnspiratory lnspiratory Flow Flow Normal COPD Expiratory Expiratory Prebronchodilator Flow Flow -- - - - - Postbronchodilator TLC RV Volume TLC RV Volume lnspiratory lnspiratory Asthma Flow Flow Restrictive Disease tIGURE 2. Pulmonaryfunctiontestflow-volumepatterns.RV=residual volume; TLC=total lungcapacity.

lnspiratory lnspiratory Asthma Flow Flow Restrictive Disease tIGURE 2. Pulmonaryfunctiontestflow-volumepatterns.RV=residual volume; TLC=total lungcapacity. Pulse Oximetry asthma have eosinophilic (type 2) airway inflammation, and Oximeters work by calculating the difference between FeNO levels may help predict glucocorticoid responsiveness in absorption ofinfrared light by oxygenated and deoxygenated these patients as well as monitor their response to and adher- blood. A normal hemoglobin saturation measured by pulse ence to anti-inflammatory therap): The American Thoracic oximetry is 95'7, to 100'2,, and values below 90'7, indicate Society guidelines suggest that FeNO levels above 50 ppb indi hypoxemia. Substances in the blood that absorb infrared light cate glucocorticoid sensitive airway inflammation. Patients may cause erroneous readings, including carboxyhemoglobin with levels below 25 ppb are less likely to have eosinophilic (present in carbon monoxide poisoning), methemoglobin inflammation and glucocorticoid responsiveness. Fractional (caused by nitrates), methylene blue, and some topical anes exhaled nitric oxide testing is recommended as an adjunct in thetics. More commonly, patient factors such as cool extremi asthma evaluation for those aged 5 years and older. Specific ties, poor circulation, nail polish, and motion artifact result recommendations for the use of nitric oxide testing include in erroneous readings. In these cases, alternative methods of when the diagnosis of asthma is uncertain after standard measuring oxygenation. such as arterial blood gas analysis. evaluation or when spirometry cannot be performed (condi are needed. tional recommendation) and in persistent allergic asthma and uncertainty in choosing, monitoring, or adjusting medications Fractional Exhaled Nitric Oxide (conditional recommendation). Measurement of the fraction of nitric oxide in an exhaled breath sample (FeNO) provides a noninvasive way to quanti[z eosinophilic airway inflammation and serves as a complemen lmaging and Bronchoscopy tary tool in the management of lung diseases asthma in Imaging particular. Elevated FeNO levels correlate modestly with blood Table 2 provides information on various imaging modalities and sputum eosinophilia. More than half of patients with and their indications.

Pulse Oximetry asthma have eosinophilic (type 2) airway inflammation, and Oximeters work by calculating the difference between FeNO levels may help predict glucocorticoid responsiveness in absorption ofinfrared light by oxygenated and deoxygenated these patients as well as monitor their response to and adher- blood. A normal hemoglobin saturation measured by pulse ence to anti-inflammatory therap): The American Thoracic oximetry is 95'7, to 100'2,, and values below 90'7, indicate Society guidelines suggest that FeNO levels above 50 ppb indi hypoxemia. Substances in the blood that absorb infrared light cate glucocorticoid sensitive airway inflammation. Patients may cause erroneous readings, including carboxyhemoglobin with levels below 25 ppb are less likely to have eosinophilic (present in carbon monoxide poisoning), methemoglobin inflammation and glucocorticoid responsiveness. Fractional (caused by nitrates), methylene blue, and some topical anes exhaled nitric oxide testing is recommended as an adjunct in thetics. More commonly, patient factors such as cool extremi asthma evaluation for those aged 5 years and older. Specific ties, poor circulation, nail polish, and motion artifact result recommendations for the use of nitric oxide testing include in erroneous readings. In these cases, alternative methods of when the diagnosis of asthma is uncertain after standard measuring oxygenation. such as arterial blood gas analysis. evaluation or when spirometry cannot be performed (condi are needed. tional recommendation) and in persistent allergic asthma and uncertainty in choosing, monitoring, or adjusting medications Fractional Exhaled Nitric Oxide (conditional recommendation). Measurement of the fraction of nitric oxide in an exhaled breath sample (FeNO) provides a noninvasive way to quanti[z eosinophilic airway inflammation and serves as a complemen lmaging and Bronchoscopy tary tool in the management of lung diseases asthma in Imaging particular. Elevated FeNO levels correlate modestly with blood Table 2 provides information on various imaging modalities and sputum eosinophilia. More than half of patients with and their indications. 3

Pulmonary Diagnostic Tests TABLE 2. Pulmonary lmaging Modalities and lndications Modality Indications Common Advantages Disadvantages Relative Conditions/Uses Radiation Level Chest radiography lnitial imaging for Acute respiratory Widely available Low resolution Low most pulmonary illness patients Portable Two-dimensional Pneumothorax imaging Suitable for critically Dyspnea ill patients Heart failure

TABLE 2. Pulmonary lmaging Modalities and lndications Modality Indications Common Advantages Disadvantages Relative Conditions/Uses Radiation Level Chest radiography lnitial imaging for Acute respiratory Widely available Low resolution Low most pulmonary illness patients Portable Two-dimensional Pneumothorax imaging Suitable for critically Dyspnea ill patients Heart failure Chest pain Chest CT Eva I u ate Malignancies High resolution Requires patient High abnormality seen on transportation and lnterstitial lung Provides detail of chest radiograph cooperation disease lung anatomy Examine Risks with use of parenchymal Suspected intravenous contrast pulmonary (kidney toxicity, architecture embolism anaphylaxis) Evaluate mediastinal Lung nodules structu res Lung cancer Visualize small screening lesions not seen on chest radiograph Hemoptysis Angiography of Complicated acute pulmonary vessels respiratory illness Blunt chest trauma Ultrasonography Evaluate acute Pleural effusion Portable Lower resolution None dyspnea Heart failure Real-time lmage acquisition is Characterize pleural assessment operator and Pneumothorax patient dependent space and Suitable for critically diaphragm Diaphragm function ill patients Thoracentesis Tube thoracostomy PET/CT Assess metabolic Malignancy staging Allows correlation of Requires patient High tissue activity anatomy with transportation and Biopsy localization physiologic activity cooperation

Chest pain Chest CT Eva I u ate Malignancies High resolution Requires patient High abnormality seen on transportation and lnterstitial lung Provides detail of chest radiograph cooperation disease lung anatomy Examine Risks with use of parenchymal Suspected intravenous contrast pulmonary (kidney toxicity, architecture embolism anaphylaxis) Evaluate mediastinal Lung nodules structu res Lung cancer Visualize small screening lesions not seen on chest radiograph Hemoptysis Angiography of Complicated acute pulmonary vessels respiratory illness Blunt chest trauma Ultrasonography Evaluate acute Pleural effusion Portable Lower resolution None dyspnea Heart failure Real-time lmage acquisition is Characterize pleural assessment operator and Pneumothorax patient dependent space and Suitable for critically diaphragm Diaphragm function ill patients Thoracentesis Tube thoracostomy PET/CT Assess metabolic Malignancy staging Allows correlation of Requires patient High tissue activity anatomy with transportation and Biopsy localization physiologic activity cooperation Chest Radiography the vasculature, and minimum intensity projection, which Conventional chest radiographs are indicated as the initial focuses on the airways. Additional variables in CT imaging imaging procedure for most patients with significant respira include slice thickness and interval. Contrast enhancement tory symptoms. Posteroanterior and lateral views should be may be used to augment the value of imaging on the basis of obtained. The advantages are the availability of testing and the underlying disease. the low dose of radiation exposure lor the patient. The limita The choice of examination depends on the clinical tions include the need to take a deep inspiration, breath context and information sought. Noncontrast CT is usually holding, image resolution, and the two dimensional images preferred because contrast makes assessing the lung paren produced. chyma more difficult. For most patients, routine (slice thickness of 2 or 2.5 mm) noncontrast CT provides the Computed Tomography needed information. For patients suspected of having CT of the thorax allows detailed, high resolution imaging of interstitial lung disease, a high-resolution (slice thickness the Iungs and options for both static and dynamic imaging of 1 mm) study should be ordered. Additional expiratory techniques. Helical scanners allow rapid scanning but may views can evaluate for air trapping and further inform the require patients to hold their breath at lull inspiration fbr diagnosis of small airways disease. However, because the 30 seconds or more. Reconstruction can include sagittal and slice interval (the distance between individual slices) with coronal images, which result in three dimensional representa high-resolution CT is larger than with conventional CT. this tion of the extent and distribution ol disease. More specialized technique "skips" interval sections ol the lung and should techniques reformat the data to highlight specific structures; not be used to evaluate lung nodules. Use of intravenous they include maximum intensify projection, which focuses on contrast dye helps delineate mediastinal structures and is

Chest Radiography the vasculature, and minimum intensity projection, which Conventional chest radiographs are indicated as the initial focuses on the airways. Additional variables in CT imaging imaging procedure for most patients with significant respira include slice thickness and interval. Contrast enhancement tory symptoms. Posteroanterior and lateral views should be may be used to augment the value of imaging on the basis of obtained. The advantages are the availability of testing and the underlying disease. the low dose of radiation exposure lor the patient. The limita The choice of examination depends on the clinical tions include the need to take a deep inspiration, breath context and information sought. Noncontrast CT is usually holding, image resolution, and the two dimensional images preferred because contrast makes assessing the lung paren produced. chyma more difficult. For most patients, routine (slice thickness of 2 or 2.5 mm) noncontrast CT provides the Computed Tomography needed information. For patients suspected of having CT of the thorax allows detailed, high resolution imaging of interstitial lung disease, a high-resolution (slice thickness the Iungs and options for both static and dynamic imaging of 1 mm) study should be ordered. Additional expiratory techniques. Helical scanners allow rapid scanning but may views can evaluate for air trapping and further inform the require patients to hold their breath at lull inspiration fbr diagnosis of small airways disease. However, because the 30 seconds or more. Reconstruction can include sagittal and slice interval (the distance between individual slices) with coronal images, which result in three dimensional representa high-resolution CT is larger than with conventional CT. this tion of the extent and distribution ol disease. More specialized technique "skips" interval sections ol the lung and should techniques reformat the data to highlight specific structures; not be used to evaluate lung nodules. Use of intravenous they include maximum intensify projection, which focuses on contrast dye helps delineate mediastinal structures and is 4

Airways Disease particularly useful in patients with suspected lymphade tumors have low rates of metabolic activity, such as carci nopathy or vascular pathology. CT angiography is used fbr noid, adenocarcinoma in situ, and rarely, metastatic kidney, detection of pulmonary embolism and uses a rapid, timed prostate, or testicular cancer. PET is not useful for the deter bolus of intravenous contrast. mination of malignant potential in lung nodules less than CT scanning exposes the patient to a much higher dose of B mm in size. radiation than traditional chest radiographs, and CT is cur rently the primary source of imaging radiation exposure for Bronchoscopy and Endobronchial patients. Low dose CT scanning is now the recommended Ultrasonography choice lor lung cancer screening in the United States (see Lung Bronchoscopy is a diagnostic (Table 3) and therapeutic Tumors). (Table 4) tool for patients with lung disorders. It is used for I(IY POIT{T the diagnosis of localized and difTuse pulmonary diseases . High resolution CT techniques are preferred for evalua and is important in the diagnostic evaluation of pulmonary infections, particularly in the immunocompromised host, tion of interstitial lung disease; conventional noncontrast as well as for various therapeutic uses. Endobronchial CT is used to evaluate lung nodules and most other Iung ultrasonography is the initial procedure of choice fbr disease; and CT angiography is used for detection of obtaining tissue from mediastinal and hilar lymph nodes in pulmonary embolism. the diagnosis and staging of patients with known or sus pected thoracic malignancy. Ultrasonography ofthe Lung and Diaphragm Point of care thoracic ultrasonography provides a noninva XEY POI IIT sive means of rapidly assessing the lungs, pleura, and dia- o Endobronchial ultrasonography is the initial procedure phragm. It is particularly helpful fbr critically ill patients {br of choice for obtaining tissue from mediastinal and hilar whom the use of other imaging techniques requiring trans lymph nodes in the staging of patients with known or port may pose undue risk or delay diagnosis. Thoracic ultra suspected thoracic malignancy. sonography detects the presence and volume of pleural efTusions more accurately than chest radiography; it can also identify characteristics that suggest an effusion and diflicutty or risks with draining the effusion. In addition, Airways Disease performing pleural drainage procedures such as thoracen tesis or tube thoracostomy with ultrasound guidance Asthma reduces risks for complications, including pneumothorax. Epidemiology and Natural History Thoracic ultrasonography assesses diaphragm function Asthma is an inflammatory disorder of the airways character more accurately than fluoroscopy. Ultrasonography of the ized by cough, wheezing, chest tightness, dyspnea, and variable lung parenchyma can identify conscllidation, whereas dem airflow obstruction. Asthma is a major health burden through onstration of movement ol the visceral pleura against the out the world; approximately 7.9"1, of the U.S. population has parietal pleura (lung sliding sign) excludes a pneumothorax been diagnosed with asthma, which accounts for 9.6 million at the area scanned. Obesity and significant edema or mus office visits per year. Prevalence is increased among patients culature can degrade image quality and limit ultrasound older than 65 years, women, Black persons, and persons living usefulness. whereas complex or high density pleural col below the poverty level. Mortality in asthma is significant, with lections (empyema, hemothorax) may be too echogenic 9.9 deaths per million Americans caused by asthma in 2Ol7; fbr accurate detection or identification of adjacent tissue significantly higher mortality is seen among patients who are structures. Black and patients who are older than 65 years. The onset ofasthma can occur at any age, and the natu Positron Emission Tomography ral history varies with the duration and severity of symp PB'l'uses the radionuclide 1B f'luoro 2 deoxyglucose, which toms, sex, and response to therapy. Children often have a accumulates within highly metabolically active cells such family history of atopy or exposure to sensitizing allergens as cancer cells and can be visualized as discrete areas of such as dust mites or cockroaches. Childhood asthma may uptake. Integrated PET/CT allows improved localization of improve or resolve during the teenage and adult years, par the metabolic activity. PET scans are widely used to evaluate ticularly in males. Adults with new onset asthma may have the likelihood of malignancy in lung nodules, to stage occupational exposures known to induce bronchial hyper known thoracic tumors, and to evaluate for metastatic dis reactivity. Those with severe symptoms generally have a ease from other nonthoracic malignancies. False positive more sustained course, lower pulmonary function, and PET scans can occur in other hypermetabolic conditions increased risk of developing persistent airway obstruction. in which cells accumulate I'luorodeoxyglucose, such as Diagnosis and treatment of asthma in older adults is often inf'ection or inflammation. False negatives can occur when challenged by symptom overlap with other conditions

particularly useful in patients with suspected lymphade tumors have low rates of metabolic activity, such as carci nopathy or vascular pathology. CT angiography is used fbr noid, adenocarcinoma in situ, and rarely, metastatic kidney, detection of pulmonary embolism and uses a rapid, timed prostate, or testicular cancer. PET is not useful for the deter bolus of intravenous contrast. mination of malignant potential in lung nodules less than CT scanning exposes the patient to a much higher dose of B mm in size. radiation than traditional chest radiographs, and CT is cur rently the primary source of imaging radiation exposure for Bronchoscopy and Endobronchial patients. Low dose CT scanning is now the recommended Ultrasonography choice lor lung cancer screening in the United States (see Lung Bronchoscopy is a diagnostic (Table 3) and therapeutic Tumors). (Table 4) tool for patients with lung disorders. It is used for I(IY POIT{T the diagnosis of localized and difTuse pulmonary diseases . High resolution CT techniques are preferred for evalua and is important in the diagnostic evaluation of pulmonary infections, particularly in the immunocompromised host, tion of interstitial lung disease; conventional noncontrast as well as for various therapeutic uses. Endobronchial CT is used to evaluate lung nodules and most other Iung ultrasonography is the initial procedure of choice fbr disease; and CT angiography is used for detection of obtaining tissue from mediastinal and hilar lymph nodes in pulmonary embolism. the diagnosis and staging of patients with known or sus pected thoracic malignancy. Ultrasonography ofthe Lung and Diaphragm Point of care thoracic ultrasonography provides a noninva XEY POI IIT sive means of rapidly assessing the lungs, pleura, and dia- o Endobronchial ultrasonography is the initial procedure phragm. It is particularly helpful fbr critically ill patients {br of choice for obtaining tissue from mediastinal and hilar whom the use of other imaging techniques requiring trans lymph nodes in the staging of patients with known or port may pose undue risk or delay diagnosis. Thoracic ultra suspected thoracic malignancy. sonography detects the presence and volume of pleural efTusions more accurately than chest radiography; it can also identify characteristics that suggest an effusion and diflicutty or risks with draining the effusion. In addition, Airways Disease performing pleural drainage procedures such as thoracen tesis or tube thoracostomy with ultrasound guidance Asthma reduces risks for complications, including pneumothorax. Epidemiology and Natural History Thoracic ultrasonography assesses diaphragm function Asthma is an inflammatory disorder of the airways character more accurately than fluoroscopy. Ultrasonography of the ized by cough, wheezing, chest tightness, dyspnea, and variable lung parenchyma can identify conscllidation, whereas dem airflow obstruction. Asthma is a major health burden through onstration of movement ol the visceral pleura against the out the world; approximately 7.9"1, of the U.S. population has parietal pleura (lung sliding sign) excludes a pneumothorax been diagnosed with asthma, which accounts for 9.6 million at the area scanned. Obesity and significant edema or mus office visits per year. Prevalence is increased among patients culature can degrade image quality and limit ultrasound older than 65 years, women, Black persons, and persons living usefulness. whereas complex or high density pleural col below the poverty level. Mortality in asthma is significant, with lections (empyema, hemothorax) may be too echogenic 9.9 deaths per million Americans caused by asthma in 2Ol7; fbr accurate detection or identification of adjacent tissue significantly higher mortality is seen among patients who are structures. Black and patients who are older than 65 years. The onset ofasthma can occur at any age, and the natu Positron Emission Tomography ral history varies with the duration and severity of symp PB'l'uses the radionuclide 1B f'luoro 2 deoxyglucose, which toms, sex, and response to therapy. Children often have a accumulates within highly metabolically active cells such family history of atopy or exposure to sensitizing allergens as cancer cells and can be visualized as discrete areas of such as dust mites or cockroaches. Childhood asthma may uptake. Integrated PET/CT allows improved localization of improve or resolve during the teenage and adult years, par the metabolic activity. PET scans are widely used to evaluate ticularly in males. Adults with new onset asthma may have the likelihood of malignancy in lung nodules, to stage occupational exposures known to induce bronchial hyper known thoracic tumors, and to evaluate for metastatic dis reactivity. Those with severe symptoms generally have a ease from other nonthoracic malignancies. False positive more sustained course, lower pulmonary function, and PET scans can occur in other hypermetabolic conditions increased risk of developing persistent airway obstruction. in which cells accumulate I'luorodeoxyglucose, such as Diagnosis and treatment of asthma in older adults is often inf'ection or inflammation. False negatives can occur when challenged by symptom overlap with other conditions 5