Boards and Beyond: Pulmonary A Companion Book to the Boards and Beyond Website Jason Ryan, MD, MPH i
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Table of Contents Pulmonary Anatomy 1 Treatment of COPD/Asthma 45 Pulmonary Physiology 4 Pneumonia 50 Hemoglobin 8 Pleural Disease 57 Pulmonary Circulation 13 Lung Cancer 60 Ventilation & Perfusion 18 Sleep Apnea 64 Carbon Dioxide 23 Cystic Fibrosis 66 Lung Physical Exam 28 Tuberculosis 70 Pulmonary Function Tests 31 Sarcoidosis 77 Obstructive Lung Disease 33 Pulmonary Embolism 79 Restrictive Lung Disease 41 Chest X-rays 82 iii
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Zones Pulmonary Anatomy Jason Ryan, MD, MPH Conducting Zone No gas exchange Large airways: nose, pharynx, trachea, bronchi Filters, warms, humidifies air Respiratory Zone Gas exchange Respiratory bronchioles, alveolar ducts, alveoli Mucous Secretions produced by respiratory tract Mostly glycoproteins and water Secreted by goblet cells in bronchial walls Protects against particulates, infection Beating cilia move mucous to epiglottis swallowed Alveoli Small sacs Gas exchange Surrounded by capillaries Alveolar Cells: Pneumocytes Type 1 Most common (97% of cells) Thin for gas exchange Type 2 Produce surfactant Can proliferate to other cells key for regeneration after injury Clara cells Surfactant Detoxification Surfactant Exhale alveoli shrink Could collapse atelectasis efficiency gas exchange Surfactant allows alveoli to avoid collapse 1
Surfactant Surfactant Distending Pressure = 2 * (surface tension) radius Secreted by type 2 pneumocytes Mix of lecithins Especially dipalmitoylphosphatidylcholine Fetal Lung Maturity Lungs are mature when enough surfactant present Occurs around 35 weeks Lecithin sphingomyelin ratio (L/S ratio) Both produced equally until ~35 weeks Ratio >2.0 in amniotic fluid suggests lungs mature Preterm delivery: betamethasone used to stimulate surfactant production in lungs Neonatal respiratory distress syndrome Hyaline membrane disease Atelectasis Severe hypoxemia/ pco2 (poor ventilation) Poorly responsive to O2 Lungs collapsed (alveoli) Intrapulmonary shunting Neonatal respiratory distress syndrome Risk factors: Prematurity Maternal diabetes: high insulin levels decrease surfactant production Cesarean delivery: lack of vaginal compression stress leads to reduced fetal cortisol and reduction in surfactant Neonatal respiratory distress syndrome Many complications Bronchopulmonary dysplasia Patent ductus arteriosus (hypoxia keeps shunt open) Retinopathy of prematurity When infant taken off oxygen Neovascularization in the retina Retinal detachment blindness 2
Aspiration Right lung is more common site of aspiration Right bronchus wider Less angle More vertical path to lung Aspiration Foreign Body If upright Right inferior lobe lower portion If supine (lying flat) Right inferior lobe superior portion Diaphragm Caval opening T8 IVC Esophageal hiatus T10 Esophagus, Vagus nerve Aortic hiatus T12 Aorta, thoracic duct, azygous vein Diaphragm Innervated by C3, C4, C5 (Phrenic nerve) pain Classic example is gallbladder disease Also lower lung masses Irritation can cause dyspnea and hiccups Cut nerve diaphragm elevation, dyspnea inspiration Can see on fluoroscopy ( sniff test ) Muscles of Quiet Respiration inspiration Exhalation is passive with normal ( quiet ) breathing Exercise Breathing Inspiration (neck) Scalenes raise ribs Sternocleidomastoids raise sternum Exhalation (abdomen) Rectus muscle Internal/external obliques Transverse abdominis Internal intercostals Use of accessory muscles in respiratory distress 3
Physiology Concepts Pulmonary Physiology 1. Lung volumes/capacities 2. Ventilation and dead space 3. Lung and chest wall pressures 4. Lung compliance 5. Air flow resistance Jason Ryan, MD, MPH Lung Volumes Tidal volume In/out air with each quiet breath Expiratory reserve volume Extra air pushed out with force beyond TV RV remains in lungs Inspiratory reserve volume Extra air can be drawn in with force beyond TV Lungs filled to capacity Residual volume Air that can t be blown out no matter how hard you try Lung Capacities Capacity = sum of two volumes Total lung capacity Sum of all volumes RV + ERV+ IRV + TV Inspiratory capacity Most air you can inspire TV + IRV Vital capacity Most you can exhale TV + IRV + ERV Lung Capacities Capacity = sum of two volumes RV ERV IRV TV Functional Residual Capacity Residual volume after quiet expiration RV + ERV Volume when system is relaxed Chest wall pulling out = lungs pulling in 4
Volume Ventilation Ventilation = volume x frequency (resp rate) 500cc per breath x 20 breaths per minute 10,000cc/min Alveolar ventilation = useful for gas exchange Dead space ventilation = wasted ventilation Nose, trachea, other areas with no gas exchange Dead Space Space filled with air but no gas exchange #1: Anatomic dead space Volume of conducting portions respiratory tract Nose, trachea #2: Physiologic dead space Anatomic PLUS volume of alveoli that don t exchange gas Insufficient perfusion Apex is largest contributor Physiologic dead space increases many diseases Ventilation Total ventilation (TV) = volume/min out each breath **Volume in slightly > volume out due to O2 uptake Sometimes called minute ventilation Alveolar ventilation Fresh air for gas exchange TV minus dead space Imagine 500cc out per minute 150cc fills dead space Only 350cc available for gas exchange Measuring Dead Space Bohr s method Physiologic dead space (V d) from: Tidal volume PeCO2 (exhaled air) PaCO2 (blood gas) V d = P a CO2 P e CO2 V t P a CO2 Lung and Chest Wall Lung Volumes and Pressures Lungs tend to collapse Pull inward/recoil Chest wall tends to expand Spring outward 0 20 40 Pressure 5
Volume Volume Chest Volumes and Pressures Chest Volumes and Pressures Chest Wall Lungs FRC System -40-20 0 20 40 Pressure -40-20 0 20 40 Pressure Functional residual capacity Pressures Lung in = chest out Volume where lungs rest after quiet exhalation Pressure inside system is zero No / pressure from push/pull of lungs or chest wall Pressure = atmospheric pressure Alveoli Chest Wall Pleural Space Alveoli and Pleural Pressures + Inhale Exhale Alveoli 0 - Intrapleural Lung Compliance For given pressure how much volume changes Compliant lung Small amount diaphragm effort Generates small pressure change across lungs Large volume change Easy to move air in/out Non-compliant lung Large amount diaphragm effort Big pressure change across lung Small volume change (lungs stiff) Hard to move air in/out C = Δ V Δ P 6
Resistance Volume Lung Compliance Lung Compliance Normal lung Non compliant lung Decreased Pneumonia Pulmonary edema Pulmonary fibrosis Increased Emphysema (floppy lungs) Aging C = Δ V Δ P 0 20 40 Resistance to Air Flow Upper airways about 50% resistance Nose, mouth, pharynx Lower airway resistance Highest in medium bronchi (turbulent flow) Lowest in terminal bronchioles - slows laminar flow Trachea Terminal bronchioles Medium Bronchi Air vessel size 7