USMLE Review: Respiratory System

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USMLE ReviewRespiratory System

• Kevin P Simpson, MD

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My Prep for Today

• USMLE Website
• NOT embryology, nose, sinuses, repair, defense
  mechanisms
• Minimal Therapeutics/Pharmacology
• First Aid for the USMLE Step 1
• Best Judgment of Topics

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Outline

• Physical Exam
• PFTs
• Obstruction
• Restriction
• Physiology
• Hypoxia
• Oxygen Content, Delivery
• Dead Space, CO2

• Lung Cancer
• Pneumonia
• TB
• Effusions
• Altitude
• Pulmonary Hypertension
• Sleep Apnea

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Pulmonary Exam
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Which PFT Defines Obstruction?

• A. Decreased TLC
• B. Decreased FEV1
• C. Decreased FVC
• D. Decreased FEV1/FVC

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Which PFT Defines Restriction?

• A. Decreased TLC
• B. Decreased FEV1
• C. Decreased FVC
• D. Decreased FEV1/FVC

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K Simpson 2005
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Normal
Positive Methacholine Challenge
Restriction
Obstruction
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PFTs A Practical Approach
?FEV1/FVC Obstruction
?TLC Restriction
?DLCO Pulmonary HTN
Asthma COPD Bronchiectasis
Interstitial Disease Chest Wall
Disease Neuromuscular Disease
Associated with COPD and/or ILD Isolated
Primary Pulmonary HTN
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A 46 year old male has PFTs with TLC 72 FRC
96 RV 132 Which of the following
diseases would best explain these lung volumes
(A) Obesity (B) Emphysema (C) Amyotrophic
Lateral Sclerosis (D) Pulmonary Embolism
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(No Transcript)
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A 55 year old shipyard worker with a 45 pack year
smoking history has these PFTs FVC 62 FEV1
46 FEV1/FVC .62 TLC 92 DLCO 44. These
PFT's are most compatible with (A) Asbestosis
(B) Mesothelioma (C) Lung Cancer (D)
Emphysema
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Obstruction
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Obstruction
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Restrictive Lung Disease

• Restriction ? TLC
• Three Categories
• Interstitial Lung Disease (? Lung ER)
• Chest Wall Disease (? Chest Wall ER)
• (KS, Obesity, Ascites)
• Neuromuscular Disease
• (? TLC, ? RV, normal FRC, )
• (ALS, MD, Myopathies)

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Interstitial Lung Diseases

• Sarcoid
• Hypersensitivity Pneumonitis
• Idiopathic Pulmonary Fibrosis
• Tuberculosis

• Fungal
• Aspiration / Asbestosis
• Connective Tissue Diseases / (Cancer)
• Eosinophilic Granuloma
• Drugs
• Amiodarone, Nitrofurantoin, Bleomycin

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Sarcoid

• Non-caseating granulomata
• Multi-system disorder
• Pulmonary Lymphadenopathy /- ILD
• Elevated ACE
• ? Significance
• Treatment Steroids

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Idiopathic Pulmonary Fibrosis

• Middle/Older Aged, MaleFemale
• Progressive Dyspnea/Cough
• 2.5-5 year survival
• ? Treatment with Steroids

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Asbestos

• Long Latency
• Asbestosis
• Identical to IPF
• Chronic Exposure
• Ferruginous Bodies
• Mesothelioma
• Brief Exposures
• Exudative Effusion.Lumpy Bumpy Pleural
  Thickening
• Progressive Dyspnea and Pain

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Hypoxia

• VQ Mismatch
• Asthma, COPD, IPF, Pulmonary Embolism
• Shunt
• Blood, Pus, Water, Atelectasis, Anatomic Shunt
• Hypoventilation
• Normal A-a Gradient
• Decreased Barometric Pressure
• Altitude
• Decreased FIO2
• NOT altitude
• Diffusion Impairment

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Multiple Inert Gas Technique
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Multiple Inert Gas Technique
No V Shunt
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Multiple Inert Gas Technique
No Q Dead Space
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VQ Mismatch

• Inadequate V relative to Q
• Oxygen removed from alveolus more quickly than
  delivered through bronchi
• Mild Hypoxemia
• PaO2 Increases with administration of
  supplemental O2
• Common
• Asthma, COPD, ILD, Pulmonary Embolism

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Shunt

• NO V
• Severe Hypoxia
• PaO2 does NOT increase with supplemental O2
• Diseases
• Blood, Pus, Water
• Pulmonary Hemorrhage
• Pneumonia
• Pulmonary Edema
• High Pressure CHF
• Low Pressure ARDS
• Atelectasis
• Anatomic Shunts
• Pulmonary AVM
• Intra-Cardiac

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CO2

• CO2 ? K VCO2 / MV(1-VD/VT)
• Hypercapnea
• Increased CO2 Production
• Fever, exercise
• Reduced Minute Ventilation (nl 5 lpm)
• Increased VD/VT
• Dead Space normally 1 cc/lb
• Increased
• Increased Zone I
• Pulmonary Embolism
• Pulmonary Hypertension

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Other Physiology

• Oxygen Content
• CaO2 H x 1.34 x SaO2 PaO2 x 0.003
• nl 20 mL O2/dL blood
• A-a Gradient
• (PB PH2O) FIO2 PaCO2/RQ PaO2
• nl
• RQ VCO2/VO2
• nl VCO2 200cc/min
• nl VO2 250cc/min
• nl RQ 0.8

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Lung Cancer

• Small Cell
• Large
• Central
• Non-Cavitary
• Always Metastatic
• Therefore, always chemo
• /- RT for local control
• SIADH (? Na)

• Non-Small Cell
• Squamous
• Large
• Central
• Cavitary
• PTHrp (? Ca)
• Adeno
• Small
• Peripheral
• VTE

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Lung Cancer - cont

• Other
• BAC
• pneumonia-like
• Never mets
• Other Facts
• Women earlier with less smoking exposure
• NO proven screening method
• Risk continues 10 years post-D/C cigs
• 1 cause of cancer death

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Lung Cancer - cont

• Superior Vena Cava Syndrome
• Increased with Small Cell
• Face, Upper Extremity Swelling
• Horners Syndrome
• Myosis, anhydrosis, ptosis
• Pancoast Tumor
• Mets
• Everywhere but ? brain, bone, liver

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Pneumonia

• Fever, Chills, Sputum, Chest Pain
• Crackles, Bronchial (increased) BSs, Egophony
• Classification
• Typical vs Atypical
• CAP vs Nosocomial

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Tuberculosis

• Primary
• atypical pneumonia
• INH x 9 months
• Post-Primary
• Immediate Dissemination
• 4 drugs x 2 months then 2 drugs 2 4 months
• Reactivation
• Apical Fibro-Cavitary
• 4 drugs x 2 months then 2 drugs 2 4 months

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Effusions

• Decreased Breath Sounds, Dull, Egophony
• Transudate vs Exudate
• Increased pleural LDH, Protein, Cholesterol
• Unique Findings
• Decreased pH
• ? Infected
• Decreased Glucose
• Infection, cancer, rheumatoid arthritis
• Increased ADA
• TB
• Increased Amylase
• Pancreatitis, Ruptured Esophagus

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Altitude

• ?PB. ?PAO2. ?PaO2
• .compensatory ? Minute Ventilation
• High Altitude Sickness
• Prevent with acetazolamide
• High Altitude Pulmonary Edema (HAPE)
• Give O2, Diurese
• High Altitude Cerebral Edema (HACE)
• Give O2, ? Steroids

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Pulmonary Hypertension

• Dyspnea, Chest Pain, Syncope
• NOT Hypoxia
• Unless PFO
• Increased VD/VT
• Results in increased minute ventilation
• Etiologies
• Primary, Venous Thrombo-Embolism, Sleep Apnea,
  ANY chronic lung disease, Eisenmengers Syndrome

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Sleep Apnea

• Apnea
• ? PaO2.?? PA pressures, arrhythmia, HTN
• Frequent Arousals, Poor Sleep..Fatigue
• Central vs Obstructive
• CPAP, Weight Loss, UPPP