7 respiratory high yield

RE01-1 To understand the following topics and how they may be tested on USMLE Step 1: – Basic pulmonary anatomy and histology – Respiratory physiology – Mechanisms of hypoxemia – Ob

RE01-1

To understand the following topics and how they may

be tested on USMLE Step 1:

– Basic pulmonary anatomy and histology

– Respiratory physiology

– Mechanisms of hypoxemia

– Obstructive lung disease

– Restrictive lung disease

RE01-2

Inferior vena cava (T8)

Esophagus (T10) Vagus nerve Aorta (T12) Thoracic duct Azygos vein`

Pain referred to the shoulders

due to cervical innervation of

RE01-2

– Diaphragm contracts to increase the size of thoracic

cavity

– Quiet inspiration mediated via the diaphragm and

external intercostals (possibly the scalenes)

RE01-2

– Diaphragmatic fatigue

– Abdominal contents move in with inspiration

– Sign of impending respiratory failure

3

•FA 2013: 546.1 • FA 2012: 560.3 • FA 2011: 504.1

• ME 3e: 278 • ME4e: 278

• Comprises the anatomic dead space

RE01-3

– Trachea can be compressed by:

• Goiter

– Carina can be displaced by:

Kaplan Anatomy 2011 : Figure III-2-8

2

•FA 2013: 544.1 • FA 2012: 558.1 • FA 2011: 502.1

• ME 3e: 274 • ME4e: 274

RE01-3

– U-shaped cartilage in trachea to accommodate esophagus posteriorly

– Circular cartilage in all sized bronchi

– No cartilage in any bronchioles

Kaplan Anatomy 2011 : Figure III-2-8

3

•FA 2013: 544.1 • FA 2012: 558.1 • FA 2011: 502.1

• ME 3e: 274 • ME4e: 274

RE01-3

Kaplan Anatomy 2011 : Figure III-2-8

1

•FA 2013: 545.1 • FA 2012: 560.1 • FA 2011: 503.2

• ME 3e: 276 • ME4e: 276

P o s t e r i o r

Left lung

Bronchus

Pulmonary artery

Gray's Anatomy of the Human Body 20th Edition

The Pulmonary Arteries

2

•FA 2013: 545.1 • FA 2012: 560.1 • FA 2011: 503.2

• ME 3e: 276 • ME4e: 276

RE01-4

• Aspiration of Foreign Objects

– Aspiration in upright people will go to the posterior basal

segment of the right lower lobe

– In supine position goes to the superior segment of the lower

lobe of right lung

– When lying on the right it tends to go to the right upper lobe – When lying on the left the object tends to go to the lingula

3

•FA 2013: 545.1 • FA 2012: 560.1 • FA 2011: 503.2

• ME 3e: 276 • ME4e: 276

RE01-4

Left main bronchus

Left upper lobe bronchus

Lingular bronchus

Left lower lobe bronchus

Madhero88, Commons.wikimedia.org, Used With Permission

RE01-4

• Bronchopulmonary Segments

– 10 segments in right lung

– 8-10 segments in the left lung

– Each segment contains:

• Pulmonary artery (deoxygenated blood)

• Bronchial artery (oxygenated blood)

• Veins

• Lymphatics

In the center Along the sides

5

•FA 2013: n/a • FA 2012: n/a • FA 2011: 503.1

• ME 3e: 276 • ME4e: 276

RE01-5

§ Pseudostratified ciliated columnar

epithelium

§ lines the respiratory tract from the

trachea down to the terminal

§ Aid in the detoxification of airborne toxins

§ Serve as a stem cell for both ciliated cells and themselves

RE02-1

– Surfactant (Lecithin)

Radius

syndrome

2

•FA 2013: n/a • FA 2012: 561.1 • FA 2011: 504.2

• ME 3e: 279 • ME4e: 279

RE02-1

bronchoconstriction

• Converts angiotensin I to angiotensin II

• Inhibition of the enzyme causes build-up of bradykinin, which can lead to dry cough

– Leukotrienes cause bronchoconstriction in asthmatic and allergic reactions, and act to sustain inflammatory reactions

FA 2012: 561.1 • FA 2011: 504.2 • FA 2010: 502

– Physiologic dead space (In the non-disease state):

– Physiologic dead space (disease state):

– Functional (alveolar) dead space refers to alveoli which receive

ventilation but are poorly perfused

– Physiological dead space:

2

•FA 2013: 546.3 • FA 2012: 562.1 • FA 2011: 505.1

• ME 3e: 277 • ME4e: 277

RE02-5 1

– Low pressure circuit

– Low ventilation in an area of the lungs causes vasoconstriction in that

portion of the lung (hypoxic vasoconstriction) – Diffusion of a gas across a membrane depends upon:

Fick law of diffusion: Vgas = (A/T) x D x (P1-P2)

— Vgas = Rate of gas diffusion

— A = Surface area for exchange

— T = Thickness of the membranes between alveolar gas and capillary blood

— (P1-P2) = Gas partial pressure difference across the alveolar membrane

— D = Diffusion constant (the main factor is gas solubility)

•FA 2013: 549.1 • FA 2012: 564.1 • FA 2011: 507.1

• ME 3e: 285 • ME4e: 285

RE02-6 1

•FA 2013: 549.1 • FA 2012: 564.1 • FA 2011: 507.1

• ME 3e: 283 • ME4e: 283

RE02-7 1

• Pulmonary Vascular Resistance

•FA 2013: 549.3 • FA 2012: 564.3 • FA 2011: 508.1

• ME 3e: 231 • ME4e: 231

• Tissues not receiving enough oxygen

• Amount of oxygen tissues receive is dependent upon cardiac output and oxygen concentration of the blood

•FA 2013: 550.1 • FA 2012: 565.1 • FA 2011: 508.2

• ME 3e: 284 • ME4e: 284

= Venous PCO2 (use arterial PCO2 from ABG)

= End tidal PCO2 (obtained from intubated patients)

• A-a gradient > 15 mm Hg indicates defective oxygenation of

blood in the lungs

Alveolar Gas Equation

3

-Or-

•FA 2013: 550.2 • FA 2012: 565.2 • FA 2011: 508.3

• ME 3e: 282 • ME4e: 282

RE03-2

• Hemoglobin

RE03-2

– 2 alpha chains and 2 gamma chains

– Very high affinity for oxygen and low affinity for 2,3 DPG

2

•FA 2013: 547.2 • FA 2012: 562.3 • FA 2011: 505.3

• ME 3e: 284 • ME4e: 284

RE03-2

– Citrate in stored blood binds with 2,3-DPG

– Low 2,3-DPG makes unloading of oxygen from Hb

difficult

– Can be clinically relevant in a patient requiring blood transfusion to improve tissue oxygenation

– Inosine helps to replenish 2,3-DPG to decrease the

affinity of Hb for oxygen

3

•FA 2013: 547.2 • FA 2012: 562.3 • FA 2011: 505.3

• ME 3e: 288 • ME4e: 288

RE03-2

• Methemoglobin

– Fe +2 à Fe +3

– Fe +3 cannot bind oxygen

– Drugs induced by:

– Congenital methemoglobinemia

– Treated with methylene blue

– Methemoglobinemia can be induced using nitrites to treat CN - poisoning

– Thiosulfate is used to bind cyanide

4

•FA 2013: 547.3 • FA 2012: 563.1 • FA 2011: 506.1

• ME 3e: 40 • ME4e: 40

RE03-2

• CO replaces O2 bound to the hemoglobin

• Arterial oxygen content

is reduced but PO2 stays normal

Kaplan Physiology 2011 : Figure VII-3-5

Carboxyhemoglobin

5

•FA 2013: 547.3 • FA 2012: 563.1 • FA 2011: 506.1

• ME 3e: 284 • ME4e: 284

RE03-2

Fetal Hb

(Exercise or Stress (Resting)

Kaplan Physiology 2011 : Figure VII-3-3

Hb-O 2 Dissociation Curve

• P50 increases in a right shift

• P50 decreases in a left shift

•FA 2013: 548.1 • FA 2012: 563.2 • FA 2011: 506.2

• ME 3e: 284 • ME4e: 284

RE04-1

Lecture 4:

Respiratory System

RE04-1

RESP4_2- 2

•FA 2013: 552.2 • FA 2012: 567.1 • FA 2011: 509.3

• ME 3e: 288 • ME4e: 288

RESP4_3-

– Increased ventilation to compensate for increased O 2 demand and CO 2 production

– Increased pulmonary blood flow

– Improvement in V A /Q ratio at the apex

– Increased venous PCO 2

– Increased lactic acid production à ↓pH

– PaCO2 begins to fall around the lactate threshold and continues to decline as one approaches max VO2

1

•FA 2013: 552.3 • FA 2012: 567.2 • FA 2011: 509.4

• ME 3e: 283 • ME4e: 283

RESP4_4-

• Examination of Lungs

1

•FA 2013: 557.1 • FA 2012: 571.1 • FA 2011: 512.3

• ME 3e: 297 • ME4e: 297

RESP4_4-

– Tension pneumothorax

RESP5_1-

• Obstructive Lung Diseases (COPD & asthma)

– Disease process that results in an obstruction to airflow – Inspiratory or expiratory

– Obstruction to exhalation more common

• Restrictive Lung Disease (pulmonary fibrosis)

– Thickening of the interstitium of the lungs

– Increased fibroelastic tissue

– Decrease in all lung volumes

2

•FA 2013: 556.2 • FA 2012: 570.2 • FA 2011: 512.1

• ME 3e: 281 • ME4e: 281

RESP5_3-

– Blue Bloaters (cyanosis)

RESP5_4-

– Pink Puffers (no cyanosis and lip pursing)

– Elastase (protease) destroys the interstitium of lungs – Airways collapse during exhalation

– Barrel chest

– Good ventilation and poor perfusion

– Destruction of alveolar walls à destruction of capillary bed

– High compliance of the lungs

1

•FA 2013: 554.1 • FA 2012: 568.2 • FA 2011: 510.3

• ME 3e: 281 • ME4e: 281

RESP5_4-

• Interstitial spaces surrounding the

alveoli are broken down

Emphysema

Commons.wikimedia.org, Used With Permission

2

•FA 2013: 554.1 • FA 2012: 568.2 • FA 2011: 510.3

• ME 3e: 293 • ME4e: 293

• Form spontaneously in young, tall, healthy males

• Rupture in pleural space can lead to spontaneous pneumothorax

– Panacinar

3

•FA 2013: 554.1 • FA 2012: 568.2 • FA 2011: 510.3

• ME 3e: 293 • ME4e: 293

RESP5_5-

• Bronchiectasis

– Chronic necrotizing infection of bronchi

RESP5_6-

• Asthma

– Disease of large airways (bronchi)

– Pathology

– Triggers: allergens, viral infections, exercise

• Smooth muscle hypertrophy

• Reversible bronchoconstriction

• Obstruction to expiration – 2 phases:

• Acute bronchoconstrction

• Inflammation of airways – Methacholine challenge test (causes bronchoconstriction)

– Physical signs: wheezing, decreased inhalation/exhalation ratios, pulsus

– Curschmann's spirals: shedding of respiratory epithelium

1

•FA 2013: 554.1 • FA 2012: 568.2 • FA 2011: 510.3

• ME 3e: 294 • ME4e: 294

RESP5_7- 1

• Antihistamines

• Reduced second messengers such as IP 3

• Decreased itching, flushing and runny nose symptoms

• Diphenhydramine, dimenhydrinate, and chlorpheniramine

• Anti-cholinergic side effects

– Change in mental status, dryness, flushing, spasm of accommodation and increased body temperature

– Tachycardia, decreased gastric motility and urinary bladder contraction

• Can be used as a sleeping aid

• Loratadine, fexofenadine and cetirizine

• Decreased entry into the CNS

– 1 st generation antihistamine drugs contraindicated in BPH

•FA 2013: 562.1 • FA 2012: 575.1 • FA 2011: 514.4

• ME 3e: 190 • ME4e: 190

RESP5_8- 1

•FA 2013: 563.1 • FA 2012: 576.1 • FA 2011: 515.1

• ME 3e: 294 • ME4e: 294

RESP5_8- 2

•FA 2013: 563.1 • FA 2012: 576.1 • FA 2011: 515.1

• ME 3e: 294 • ME4e: 294

• Loosens mucus plugs

• Antidote for acetaminophen toxicity

1

•FA 2013: 563.2 • FA 2012: 577.1 • FA 2011: 516.1

• ME 3e: 73 • ME4e: 73

RESP6_-

Restrictive lung disease

– Interstitial lung disease

– Pneumoconioses

– Neonatal respiratory distress syndrome and ARDS

Respiratory: Lecture 6

RESP6_1-1

RESP6_- 2

•FA 2013: 556.2 • FA 2012: 570.2 • FA 2011: 512.1

• ME 3e: 281 • ME4e: 281

RESP6_2-

• Sarcoidosis

Bilateral hilar lymphadenopathy

Source: Amit Kumar Sanghi

1

•FA 2013: 555.1 • FA 2012: 569.1 • FA 2011: 511.1

• ME 3e: 293 • ME4e: 293

RESP6_3-

– Infiltration of interstitium with fibroblasts, which

deposit collagen

1

•FA 2013: 555.1 • FA 2012: 569.1 • FA 2011: 511.1

• ME 3e: 293 • ME4e: 293

RESP6_4-

• Goodpasture syndrome

– Anti-GBM antibodies

– Glomerulonephritis

– Interstitial lung disease

– Diffuse alveolar hemorrhage

RESP6_5-

– Histiocytosis X (Langerhan cell histiocytosis)

– Malignant proliferation of langerhan cells (dendritic cells

RESP6_7-

– Hypersensitivity reaction to environmental agents

– Examples:

– Treatment

1

•FA 2013: 555.1 • FA 2012: 569.1 • FA 2011: 511.1

• ME 3e: 295 • ME4e: 295

RESP6_8-

• Coal miner’s pneumoconiosis

– Accumulation of carbon in the lung tissue

– Interstitial inflammation

– Pulmonary hypertension → cor pulmonale

– Disease predominant in the upper lobes

• Silicosis

– Glass blowing, sand blasting and mining

– Upper lobe involvement

– Egg shell calcification of hilar lymph nodes

– Increased risk of tuberculosis

– Macrophages involved in the pathogenesis of fibrosis

1

•FA 2013: 555.2 • FA 2012: 569.2 • FA 2011: 511.2

• ME 3e: 295 • ME4e: 295

– Lower lobe involvement

– Calcified pleural plaques (Ivory white plaques)

– Asbestos bodies (golden brown bodies resembling dumbbells)

Source: Paul J Cunningham

Multiple calcified pleural plaques

2

•FA 2013: 555.2 • FA 2012: 569.2 • FA 2011: 511.2

• ME 3e: 295 • ME4e: 295

RESP6_9-

Pulmonary Edema

Non-Cardiogenic Cardiogenic

Insult to alveoli and cells lining them

Increased left atrial and

ventricular pressures

Neonatal Respiratory Distress Syndrome (Surfactant Deficiency)

Adult Respiratory Distress Syndrome (Acute Lung Injury)

1

•FA 2013: 555.3 • FA 2012: 569.3 • FA 2011: 511.3

• ME 3e: 295 • ME4e: 295

3

•FA 2013: 555.3 • FA 2012: 569.3 • FA 2011: 511.3

• ME 3e: 295 • ME4e: 295

RESP6_9-

• NRDS: Risk Factors

– Prematurity

– Diabetes in the mother

– Delivery through a caesarian section

4

•FA 2013: 555.3 • FA 2012: 569.3 • FA 2011: 511.3

• ME 3e: 295 • ME4e: 295

RESP6_9-

– Diffuse alveolar damage

– Damage to type 2 pneumocytes

– Release of inflammatory cytokines

– Fluid is released into the interstitial spaces of the lungs – Restrictive patterns (increased work of breathing)

– Hyaline membrane is formed by protein rich fluids

– Diffusion impairment

6

•FA 2013: 556.1 • FA 2012: 570.1 • FA 2011: 511.4

• ME 3e: 295 • ME4e: 295

RESP6_9-

Samir, commons.wikimedia.org, Used with Permission

ARDS

7

•FA 2013: 556.1 • FA 2012: 570.1 • FA 2011: 511.4

• ME 3e: 295 • ME4e: 295

RESP7_1- 2

– Tends to involve a single lobe of the lung

– Most commonly caused by Streptococcus pneumoniae

– Intra-alveolar production of pus causes consolidation in the lobe

Stages: congestion (first 24 hours), red hepatization,

grey hepatization, resolution

•FA 2013: 560.1 • FA 2012: 573.1 • FA 2011: 514.1

• ME 3e: 291 • ME4e: 291

RESP7_1-

• Bronchopneumonia

– Inflammatory exudates start in the small airways

(bronchioles) and extend into the alveoli

RESP7_1-

• Haemophilus influenzae

• Contains a polysaccharide capsule of polyribitol phosphate (PRP)

RESP7_1-

erythromycin)

(CYSTEINE)

7

•FA 2013: 135.1 • FA 2012: 162.3 • FA 2011: 150.5

• ME 3e: 292 • ME4e: 292

RESP7_1-

– Hospital-acquired pneumonia (ventilator-associated) – Pneumonia in cystic fibrosis patients

– Infections in burn patients

– Sepsis – ecthyma gangrenosum (black skin lesions)

– UTI

– External otitis (swimmer’s ear)

– Malignant otitis externa in diabetics

– Exotoxin A – Elongation factor–2 inhibitor

RESP7_1- 10

• Chlamydia

– Cannot make its own ATP (obligate intracellular organism)

– No muramic acid in cell walls (gram negative)

– Stained with giemsa stain