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Chest X Ray Interpretation

By Francis Nelson,2014-05-11 21:39
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Chest X Ray Interpretation

    Chest X Ray Interpretation

    Demonstrate a systematic approach to CxR interpretation:

    Assess this in some order:

    ; Preparation: turn off lights, view films in order

    ; Assure Quality: correct patient, etc.

    ; Soft Tissues: foreign bodies (metal), air, mastectomy

    ; Bones: fractures, lesions (missing bone)

    ; Mediastinal contour: width, assess for masses

    ; Heart: shape of silhouette, >2:1 width

    ; Pulmonary vessels: artery enlargement, pruning

    ; Hila: masses, lymphadenopathy

    ; Trachea: midline, masses

    ; Pleura: effusion, thickening, calcification

    ; Lung Parenchyma: abnormal shadows or lucencies

    ; Portable ICU films: first look at tubes and asses for PTX

    State the advantages/disadvantages of PA CxRs and AP CxRs:

    ; PA CxRs (patient upright with chest against film, xray beam travels from back to front

    ; Advantages: sharp image, diaphragm is lower so more of the lung is visible, easy and quick to obtain

    ; Disadvantages: patient must be able to sit upright and go to radiology ; LA CxRs (patient lying down, xray beam travels from front to back

    ; Advantages: very sick patients, infants, unable to go to radiology

    ; Disadvantages: less sharp, shows less lung, distorts structures

    Demonstrate the advantages of decubitus CxRs:

    ; Patient lies on the side

    ; Reveals free flowing pleural fluid, confirms air-fluid levels in the lung ; Always get images of both sides to show what moves and what is loculated

    Demonstrate knowledge of lobar anatomy and anatomic relationships:

    ; Recall that the lower lobes take up most of the space in the back and lie along the diaphragm ; The RML is along the right heart border

    ; The RUL is along the mediastinum

    ; The lingula lies along the left heart border

    ; The aortic knob is along the LUL

    ; The major fissures separate the LUL from the LLL and the RUL and RML from the RLL. Oblique, runs from T3 to

    costophrenic angle, only seen on LA.

    ; The minor fissure separates RUL and RML. Runs from anterior chest wall to major fissure, seen on both PA and lateral

    views.

    Apply concept of silhouette sign and knowledge of anatomic relationships to the interpretation of common CxR findings:

    ; Silouette sign: Two substances of the same density, when side by side, cannot be differentiated from each other. Seen

    when a border of the heart, aorta, or diaphragm is obliterated.

    ; Anatomic relationships:

    o Right heart boarder and RML

    o Ascending aorta and RUL

    o Left heart border and lingula

    o Left anterior diaphragm and heart

    o Aortic knob and LUL

    o Right posterior diaphragm and RLL

    o Left posterior diaphragm and LLL

    Report the significance of the air bronchogram sign and recognize this on CxR: ; Air bronchogram: visualization of air in the intrapulmonary bronchi, an abnormal finding on CxR, exludes a pleural or

    mediastinal lesion

    ; Seen in: pneumonia, pulmonary edema, pulmonary infarcts, certain chronic lung lesions ; Not seen in lung lesions where bronchi are: destroyed, filled with fluid, congenitally absent

    Recognize the presence of lobar collapse on CxR:

    ; Collapse = atelectasis, decrease in volume of a lung, lobe, or segment

    ; Obstruction collapse: most common, air present in alveoli distal to obstruction is absorbed, lung segment decreases in

    volume

    ; Compression collapse: external force squeezes air out of lung (PTX, pleural effusion)

    ; Contraction collapse: scarring causes decreased volume (TB, fibrosis)

    ; Direct signs: displacement of fissures, increased radiopacity, crowding of vascular markings or air bronchograms ; Indirect signs: hilar displacement, elevation of diaphragm, shift of mediastinum, narrowing the rib cage, compensatory

    emphysema

    ; RLL or LLL Collapse: posterior, medial, or downward collapse, major fissure displaced, major fissure medially displaced ; RML Collapse: minor fissure displaced downwards, silhouette sign along right heart border

    ; Lingular Collapse: silhouette sign along left heart border

    ; RUL Collapse: upward, medial, anterior collapse, minor fissure is displaced upward and anteriorly, hilar elevation ; LUL Collapse: upward, medially, and anteriorly collapse, major fissure displaced forward

    Identify pleural effusions on CxR and the significance of presence or absence of mediastinal shift: ; Meniscus sign

    ; Subpulmonic pleural effusion: effusion trapped between lung and diaphragm (resembles elevated diaphragm) ; Large effusions can cause the mediastinum to shift to opposite side

    ; Free flowing pleural effusion: use lateral decubitus views to identify

    ; Loculated pleural effusion: doesn’t shift with a change in position, absence of air bronchogram, convex border

    ; “pseudotumor” is fluid trapped in a fissure

    ; Kerley lines: 2-3 cm long pleural perpendicular to lateral chest, represent thickened interlobular septa and edematous

    lymphatics

    Distinguish the radiographic signs on CxR of extrapleural diseases:

    ; Extrapleural diseases: neoplasm, infection, hematoma

    ; Lesions: sharp border, tapering edges, convexity toward lung, possible rib destruction, absence of pleural involvement

    Arterial Blood Gas Interpretation

    Demonstrate the ability to identify the common acid-base disturbances based on ABG interpretation: ; Step 1: pH < 7.38 is acidic, pH > 7.42 is alkalemic

    ; Step 2: [H+] = PaCO2/HCO3-

    o PaCO2 > 40 mmHg: respiratory acidemia

    o PaCO2 < 40 mmHg: respiratory alkalemia

    o HCO3 < 24 mEq/L: metabolic acidemia

    o HCO3 > 24 mEq/L: metabolic alkalemia

    ; Step 3: AG = Na+ - (Cl- + HCO3-), normal is 7-13, measure only in metabolic acidemia

    o If HCO3- is replaced by another measured anion the anion gap increases, if present limits the differential (renal

    failure, ketoacidosis, drugs or poisons, lactic acidosis)

    ; Step 4: Delta/Delta ratio: if not equal to 1, indicates more than one metabolic disturbance

    o Change AG/change HCO3- > 1: additional alkalosis

    o Change AG/change HCO3- < 1: additional acidosis

    ; Step 5: PaCO2 = 1.5 X [HCO3-] + 8 +/- 2

    o Measure only in metabolic acidemia

    o Looks for appropriate respiratory compensation

    ; Step 6: measure only in simple respiratory acid-base disturbance

    o Acute: pH will change by 0.08 units for every 10 mmHg change in PaCO2

    o Chronic: pH will change by 0.03 units for every 10 mmHg change in PaCO2

    Recognize mix acid-base disorders:

    ; Anion gap metabolic acidemia, metabolic alkalemia: occurs when delta/delta ratio indicates additional alkalemic process

    (>1)

    ; Anion gap metabolic acidemia, non-anion gap acidosis: occurs when delta/delta ratio indicates additional acidosis (<1) ; Anion gap metabolic acidemia, respiratory acidosis: occurs when Winter’s formula indicates PaCO2 is higher than

    expected for compensation

    ; Anion gap metabolic acidemia, respiratory alkalosis: occurs when Winter’s formula indicates PaCO2 is lower than

    expected for compensation

    ; Can have an anion gap metabolic acidemia, a metabolic alkalosis, and a respiratory acidosis or alkalosis, so be careful!

Calculate A-a gradient in appropriate clinical situations:

    ; Dr. Klima says he will not test us on this.

Pulmonary Function Tests:

    Outline the value and role of PFTs in diagnosing pulmonary disease:

    ; PFTs provide an objective assessment of lung function and help to determine whether dyspnea is caused by lung disease

    or other causes. It can help determine how severe a disease is and what the prognosis is.

    ; Include: spirometry, lung volumes, diffusing capacity, arterial blood gases, challenge tests, exercise testing

    Differentiate between the flow volume loops seen in obstructive vs. restrictive lung disease:

    ; Obstructive: air cannot get out of the lungs because of airway collapse on expiration

    o See wider loop with lower expiratory peak

    ; Restrictive: characterized by decreased lung volumes

    o See thin, small loop

    Distinguish the features of spirometry in obstructive vs. restrictive disease:

    ; Obstructive: results in a normal FVC, reduced FEV1, and reduced FEV1/FVC

    o FEV1 <1L associated with disabling dyspnea

    o Reversible if bronchodilator improves test results

    ; Restrictive: results in a reduced FVC and FEV1, and normal FEV1/FVC ratio

    o Need additional tests to determine lung volume and diffusing capacity

    Discern the patterns of lung volume measurements in obstructive vs. restrictive lung disease:

    ; Obstructive: hyperinflation and gas trapping

    o Increased TLC (total lung capacity) and RV/TLC

    ; Restrictive: generalized reduction in lung volume

    o Decreased TLC, RV (residual volume), and FRC (forced respiratory capacity)

List the role for diffusing capacity testing and the conditions associated with a decreased diffusing capacity:

    ; CO used to measure through binding to hemoglobin by either a single breath test or rebreathing test

    ; Decreased diffusion: characterized by marked exertional dyspnea and exercise-induced decrease in oxygen

    ; Asthma: diffusion is normal

    ; Interstial lung disease and emphysema: diffusion is decreased

Asthma

    Define and recognize the characteristics of asthma:

    ; Airway obstruction that is reversible

    ; Airway inflammation

    ; Increased airway responsiveness to a variety of stimuli

Outline the diagnostic features of asthma:

    ; Symptom course is episodic

    ; Typical episode: treatment and outcome

    ; Social/environmental setting: where, when, precipitants

    ; Impact on patient/family, family hx, allergy hx

    ; Review of systems: including snore, GERD, sinus, edema, etc.)

Identify the key asthma symptoms:

    ; Cough (may be the only symptom), wheezing, chest tightness, dyspnea

Recognize patterns of asthma symptoms:

    ; Episodic, nocturnal, seasonal, prompted by specific triggers (allergens, viral infections, chemicals, environmental irritants,

    exercise, etc)

List the clues on physical exam:

    ; Character of breath sounds

    ; Check for non-wheezing of signs of asthma

    ; Note other allergic dieases

; Symptoms may be episodic, physical exam is often normal

    State the role of methacholine testing in the diagnosis of asthma: ; Inhalation of methacholine induces a decrease in FEV1 in hyperactive airways ; Use only in patients with normal PFTs

    ; Can diagnose asthma

    Know the classic ABG findings in patients with an acute asthma attack (usual and very severe): ; Usual:

    o PaO2: low

    o PaCO2: low

    o pH: up

    o Situation: acute respiratory alkalosis, hyperventilating

    ; Very Severe:

    o PaO2: low

    o PaCO2: high

    o pH: low

    o Situation: acute respiratory acidosis, fatigued

    Generate a thorough differential diagnosis of asthma:

    ; COPD, cardiac disease, vocal cord dysfunction, lung cancer, drug-induced cough, CF, tracheomalacia or bronchomalacia,

    foreign body aspiration, viral respiratory infection, TB, immotile cilia syndrome, psychogenic or habit cough, exertional

    intolerance from inactivity or obesity, interstitial lung disease, hyperventilation syndrome, recurrent pulmonary emboli

    Demonstrate knowledge of the four components of asthma management: ; Periodic assessment and monitoring

    ; Control of exacerbating factors

    ; Pharmacologic therapy

    ; Education and partnership

    Describe asthma treatment goals:

    ; Minimal or no chronic symptoms

    ; Minimal or no exacerbations

    ; No limitations on activities; no school/work missed

    ; Maintain (near) normal pulmonary function

    ; Minimal use of short-acting inhaled beta agonist

    ; Minimal or no adverse effects from medications

    ; Meet patient and family expectation regarding asthma care

    Exhibit an understanding of asthma pharmacology: both “quick relief agents” and “long-term controller agents”:

    ; Quick Relief Agents:

    o Bronchodilators: immediate relief, B-agonists, increase cAMP, inhaled produces less side effects (tachycardia,

    tremor, hypokalemia, headache, hyperglycemia, increased lactic acid

    o Anticholinergic agents: reduce bronchospasm, slower onset ; Long Term Controller Agents:

    o Corticosteroids: most potent, consistently effective, inhibit inflammation and modify underlying disease process,

    inhaled preferred, chronic use avoided

    o Leukotriene modifiers: inhibit mediators of bronchoconstriction and increase vascular permeability, oral, useful

    for isolated exercise-induced asthma

    Know the NAEPP guidelines for the management of mild intermittent (Step 1) and severe persistent (Step IV) asthma:

    ; Mild Intermittent:

    o < 2 days/week, < 2 nights/month

    o FEV1 > 80%, PF variability < 20%

    o No daily meds

    ; Severe Persistent:

    o Continual during the day, frequently at night

    o FEV1 <60%, PF variability >30%

    o High dose ICS + long acting B agonist, add leukotriene or theophylline

Chronic Obstructive Lung Disease:

    Know the working definition of COPD:

    ; COPD is a disease state characterized by airflow limitation which is not fully reversible; it is progressive in nature, and is

    associated with inflammatory responses in the lung to noxious particles and gases

Identify the diagnostic features of COPD:

    ; Screening spirometry showing: reduced FEV1, reduced FEV1/FVC ratio

    ; Air trapping (increased TLC, RV, FRC)

    ; Reduced diffusing capacity (emphysema)

    ; Response to bronchodilators is variable

Distinguish the classic presentations of COPD (“pink puffer” & “blue bloater”)

    ; Chronic bronchitis (blue bloater)

    o Small airway disease, mucous hypersecretion, inflammation

    o +/- cyanosis, edema

    ; Emphysema (pink puffer)

    o Loss of elastic tissue, parenchymal destruction, inflammation

    o Accessory muscles, hyperresonance, reduced diaphragmatic excursion

Recognize the classic physical findings in COPD:

    ; Distant, decreased sounds

    ; Prolonged expiratory phase, “pursed lip” breathing, tripod position

    ; Rhonchi, wheezes

    ; Subxyphoid PMI, distant heart sounds

    ; Panic disorder, anxiety, depression

Outline characteristic features of COPD on diagnostic testing specifically on CxR and PFTs:

    ; CxR: hyperinflation of lungs, barrel chest

    ; PFTs: reduced FEV1, reduced FEV1/FVC

    ; Reduced diffusing capacity

    ; ABGs: can be normal, can show hypoxemia, elevated hemoglobin, elevated carboxyhemoglobin

    ; CT can show destruction of lung parenchyma, signet ring appearance

    Differentiate between asthma and COPD based on clinical findings and diagnostic testing:

    ; PFTs: bronchodilator reversibility, normal diffusing capacity

    ; Atopic hx: dermatitis, rhinitis, family

    ; Eosinophilia +/-

    ; CT of chest: high resolution is sensitive for emphysema

Pneumonia:

    Recognize the typical symptoms, presentation, and physical findings associated with pneumonia:

    ; Symptoms: fever, cough with colored sputum, pleuritic chest pain, dyspnea, altered mentation, increased or decreased

    WBC

    ; Physical findings: signs of consolidation (dullness to percussion, bronchial breath sounds)

Identify the organisms associated with common forms of pneumonia:

    ; Pneumococcal pneumonia (most common)

    ; Gram negative pneumonia: pseudomonas, gram negative enterics, aspiration

    ; Atypical pneumonia: mycoplasma, legionella, chalmydia

    Recognize modifying factors that increase the risk of infection with specific pathogens:

    ; Pneumococcal: advanced age, smoking, dementia, chronic illness, HIV infection

    ; Pseudomonas: chronic, broad spectrum or previously prolonged antibiotic therapy, bronchiectasis, malnutrition,

    neutropenia, chronic steroid therapy

    ; Mycoplasma: school aged children, military recruits, college students

    ; Chlamydia: older age group

    ; DRSP: beta-lactam therapy, older than 65, hospitalization in last 3 months, exposure to daycare center, multiple co-

    morbities, immunosuppression

    ; General risks: COPD, alcoholism, neurologic diseases, CHF, renal failure, malignancy, HIV, diabetes

    Report the diagnostic testing useful in diagnosis pneumonia:

    ; Oximetry, CBC, BMP, two blood cultures

    ; Sputum gram stain and culture, ATS if unusual pathogen suspected

    ; CxR, urine legionella antigen

    List factors associated with high risk of complications and/or death:

    ; Age > 65

    ; Co-existing illnesses: COPD, DM, CHF

    ; Physical findings: tachypnea, SBP < 90, DBP <60

    ; Labs: pO2 <60, pCO2 > 50, abnormal renal function, anemia

    ; CxR: multilobar, cavitary, effusion, rapidly progressive

    State prevention strategies available to protect against pneumonia/complications

    ; Review vaccination hx, administer pneumococcal vaccine > 65 yo

    ; Encourage smoking cessation

Cystic Fibrosis (CF)

    Define cystic fibrosis:

    ; A chronic genetic disorder that primarily affects the lungs and the gastrointestinal tract.

Know the inheritance pattern:

    ; Autosomal recessive

State how CF is diagnosed:

    ; Two recognized CF genes OR Evidence of CFTR dysfunction, sweat chloride, nasal PD

    ; AND symptoms or family history or positive newborn screen

Recognize clinical clues to the diagnosis of CF:

    ; Acute or persistent respiratory symptoms

    ; Failure to thrive/malnutrition

    ; Steatorrhea/abnormal stools

    ; Meconium ileus/intestinal obstruction

    ; Family history

    ; Electrolyte imbalance

    ; Rectal prolapse

    ; Less common: nasal polyps, sinus disease, genotyping, prenatal diagnosis, liver problems

Identify the systemic complications of CF, specifically:

    Upper respiratory manifestations:

    ; Recurrent sinusitis, nasal polyps

    Other pulmonary complications:

    ; Hypertrophy and hyperplasia of tracheal mucous glands, goblet cells

    ; Chronic pulmonary disease

    ; Recurrent pneumonia, abnormal PFTs, abnormal CxR, sputum production Report common infectious organisms in pulmonary infections:

    ; Pseudomonas aeruginosa, staph aureus, H. influenza

    Abdominal complications:

    ; Involvement of intestinal mucous glands predisposes to intestinal obstruction

    ; Liver: biliary cirrhosis

    Endocrine complications:

    ; Blocked pancreatic duct: malabsorption, obstruction, bloating/discomfort, large greasy stools, prolapse

    ; CF-related DM

    Reproductive consequences:

    ; Men are usually sterile (blocked vas deferens, immotile sperm)

    ; Women are less fertile, nutrition is important

Pulmonary Embolism (PE):

Recognize the clinical presentation of PE:

    ; See the next few points

Know the non-specific signs and symptoms that can be associated with PE:

    ; Chest pain, dyspnea, apprehension, cough, hemoptysis, diaphoresis, syncope

    ; Tachypnea, rales, tachycardia, S4 gallop, fever, wheezes, right ventricular lift, pleural friction rub

    ; Non-specific STT changes, S1-Q3-T3 pattern, right bundle branch block

    ; 10-14% have normal A-a gradient

Identify risk factors for PE:

    ; Patients at risk for VTE are generally those with one or more of Virchow’s Triad

    o Hypercoagulabilitly, stasis, injury to vessel wall

Describe common CxR findings in PE:

    ; CxR: atelectasis/infiltrate, pleural effusion, pleural based opacity, elevated diaphragm, decreased pulmonary vascularity,

    prominent pulmonary artery, normal, Westermark’s sign

    Demonstrate an understanding of the approach to diagnostic testing for PE and the role of clinical (pre-test) probability:

    ; The combined use of the estimated clinical probability and the results of one or more noninvasive tests significantly

    increases the accuracy in confirming or ruling out PE, as compared with either assessment alone.

    ; Clinical probability is based on rules that classify patients into three groups (low, intermediate, and high) based on risk

    for a PE

State the role of diagnostic testing in establishing the diagnosis of PE, specifically:

    D-Dimer:

    ; Degradation products of cross-linked fibrin in blood

    ; High false positive rate; use limited to ruling out PE

    Ventilation-perfusion scanning:

    ; Imaging after inhalation of radioactive gas or DTPA particles

    ; Perfusion imaged after venous injection of radioactive albumin

    ; The risk for PE is dependent upon the V/Q scan result and pretest clinical probability

    Helical CT:

    ; 90% sensitivity and specificity for detecting emboli involving the main and lobar pulmonary arteries

    ; Much lower sensitivity and specificity for detecting emboli involving segmental or subsegmental pulmonary arteries

    ; Recent studies have shown that patients negative on CT and who as a result do not get treatment seem to do well Ultrasonography:

    ; Visualizes thrombus and vein compressibility

    ; Positive in only 50% patients

State the treatment approach to pulmonary embolism:

    ; Pts with a high probability of PE should receive heparin during diagnostic work-up

    ; Meds: heparin, warfarin, thrombolysis (reserved for patients who are hemodynamically unstable, high risk), IVC filter

    (only for patients absolutely contraindicated for anticoagulation), thrombectomy

List absolute and relative contraindications to anticoagulation:

    ; Hypotension, hypoxemia, hemodynamic instability

Respiratory Failure:

    Identify the features of acute respiratory failure (including ABG findings):

    ; Acute dyspnea

    ; ABG: pO2 <60 (on room air), pCO2 >50, pH is acidic

    Recall the clinical disorders associated with the development of the Acute respiratory distress syndrome (ARDS) and Acute Lung Injury (ALI):

    ; Pneumonia, aspiration of gastric contents, pulmonary contusion, fat emboli, near-drowning, inhalational injury,

    reperfusion pulmonary edema, sepsis, severe trauma, cardiopulmonary bypass, drug overdose, acute pancreatitis,

    transfusions of blood products

Know the definition of ARDS and ALI:

    ; ARDS: bilateral pulmonary infiltrates, absence of cardiogenic pulmonary edema, PaO2/FiO2 ratio of <200

    ; ALI: PaO2/FiO2 <300

Recognize that acute respiratory failure can result from problems in many sites:

    ; Brain, spinal cord, neuromuscular system, thorax and pleura, upper airway, cardiovascular, lower airway and alveoli

    Differentiate between the types of respiratory failure: oxygenation failure vs. ventilation failure:

    ; Oxygenation failure: low arterial oxygen (on room air PO2 <60, on 100% oxygen PO2 <300)

    ; Ventilatory failure: PCO2 >50, with neuromuscular weakness see low vital capacity or poor respiratory muscle strength

State the common causes of oxygenation failure vs. ventilation failure:

    ; Oxygenation failure: pneumonia, acute respiratory distress syndrome, interstitial lung disease, pulmonary edema

    ; Ventilatory failure: neuromuscular weakness, drug-induced respiratory failure

    ; Combined: COPD, status asthmaticus

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