Patho Exam 4.24

Disorders of ventilation and gas exchange

Hypoxemia. Define the term.

a reduction in arterial blood O2 levels

Normal PO2: 80-100 mmHg

Hypoxemia. O2 normal value

normal value 80-100

Hypoxemia<60mmHg

Causes of hypoxemia

Hypoventilation

Impaired diffusion of gases

Inadequate circulation of blood through pulmonary capillaries

Mismatching of ventilation and perfusion (shunting)

Manifestations of hypoxemia.

—Increased respiratory effort (↑respiratory and heart rates, use of accessory muscles, pursed-lip breathing, sweating, ↑WOB)

—Cyanosis

—Impaired sensory and neurologic functions (agitation)

—Activation of compensatory mechanisms in chronic hypoxemia: increased ventilation, pulmonary vasoconstriction, increase in red blood cell production (polycythemia)

Hypercapnia. Define.

an increase in arterial blood CO2 levels

Normal PCO2: 35-45 mmHg

Hypercapnia. Normal value?

35-45mmHg.

More than 45 is hypercapnia.

Hypercapnia. Causes of hypercapnia.

Hypoventilation

Mismatching of ventilation and perfusion (usually accompanied/preceded by a decrease in arterial PO2 levels)

Hypercapnia. Manifestations.

-Increased respiratory effort

-Respiratory acidosis

-Vasodilation of blood vessels (headache, conjunctival hyperemia, warm flushed skin)

Depression of central nervous system function

-Decreased nerve firing

-Carbon dioxide narcosis

-Disorientation, somnolence, coma

-Decreased muscle contraction

Disorders of lung inflation. Pleuritis Define and causes?

Define- Inflammation of the pleura

Causes: Viral infections or pneumonia

Disorders of lung function. Pleural Pain.

Results from somatic pain fibers that innervate the parietal pleura (visceral pleura does not contain pain receptors)

Characteristics:

-Usually unilateral and abrupt in onset

-Made worse by chest movements

-Rapid and shallow breathing

Disorders of lung function. Pleural effusion. Define, causes, manifestations.

An abnormal collection of fluid in the pleural cavity

Types:

Transudative effusion (clear fluid, hydrothorax)

Exudative effusion (often contains inflammatory cells)

Empyema (purulent)

Chylothorax (effusion of lymph in the thoracic cavity)

Hemothorax (blood)

Manifestations:

Decrease in lung expansion on the affected side

Diminished breath sounds, dullness or flatness to percussion

Dyspnea, hypoxemia, pleuritic pain

Pneumothorax. Define. Spontaneous vs traumatic.

The presence of air in the pleural space

Causes partial or complete collapse of the affected lung

Spontaneous: no injury; an air-filled bleb (blister) on the lung ruptures

Traumatic: air enters through chest injury

Why is tension pneumothorax more dangerous than open pneumothorax?

Tension is more dangerous because there is one-way valve in the chest cavity but open is a two-way complete opening. Tension allows air to enter but not escape so pressure build ups.

Atelectasis. Define, causes

An incomplete expansion of a lung or a portion of a lung.

Causes:

Primary atelectasis of the newborn (lung doesn’t inflate at birth)

Secondary atelectasis in infants

Respiratory distress syndrome (lack of surfactant)

Airway obstruction due to aspiration (amniotic fluid, blood)

Acquired atelectasis

Occurs mainly in adults

Commonly caused by airway obstruction and lung compression (mucus plug, pleural effusion, tumor mass, or pneumothorax)

Atelectasis Manifestations.

Decreased chest expansion and breath sounds on affected side

Intercostal retraction during inspiration

Signs of respiratory distress: tachypnea, tachycardia, dyspnea, cyanosis, signs of hypoxemia

Interstitial lung disease. Common underlying pathology.

inflammatory and fibrotic changes in the interstitium or the interalveolar septa of the lungs → stiff and noncompliant lung → difficult to expand

Interstitial lung disease. Causes.

Occupational and environmental inhalants (asbestos, silica)

Drug and therapeutic agents (bleomycin, radiation therapy)

Granulomatous disorders (sarcoidosis)

Immunologic disorders (rheumatoid arthritis, scleroderma)

Unknown (idiopathic pulmonary fibrosis)

Interstitial lung disease. Manifestations.

(restrictive rather than obstructive):

Reduced VC and TLC (↓ expansion), but normal expiratory flow rate (airways functional, unobstructed)

Small but frequent breaths, nonproductive cough

Clubbing of fingers and toes

Advanced: hypoxemia, cyanosis, hypercapnia and respiratory acidosis

Respiratory failure in association with pulmonary hypertension and cor pulmonale

Asthma. Prominent features and persistent changes.

Chronic recurring inflammation

Hyperreactive airways

Episodic, reversible bronchoconstriction

Persistent changes may occur:

—Mucus hypersecretion

—Injury to epithelial cells

—Smooth muscle hypertrophy

—Blood vessel proliferation

Asthma. Medications.

Bronchodilators. Selective B2 agonists. Relax smooth muscle in airways and dilate airways. Acute phase of asthma.

Glucocorticoids. Glucocorticoid receptor agonist. Inhibit mast cells, eosinophils, basophils, lymphocytes, macrophages, neutrophils. Late phase of asthma.

Most common cause of COPD.

smoking

80% of COPD deaths have smoking history

Emphysema. COPD.

Emphysema: enlargement of airspaces and destruction of lung tissue.

Pathology: loss of lung elasticity and abnormal enlargement of the airspaces distal to the terminal bronchioles, with destruction of the alveolar walls and capillary beds

Manifestations-

Hyperinflation of the lungs, increase in total lung capacity (TLC)

Barrel chest (air trapping)

Mnemonic: “Pink Puffer”

—Increase respiration to maintain oxygen levels

—Dyspnea, increased ventilatory effort

—Use of accessory muscles and pursed-lip breathing

—Lack of cyanosis

Chronic Bronchitis. Pathologic hallmarks and manifestations.

Pathology: airway obstruction of the major and small airways due to a marked increase in goblet cells and excess mucus production with plugging of the airway lumen, inflammatory infiltration, and fibrosis of the bronchiolar wall

Manifestations:

Chronic productive cough

Mnemonic: “Blue Bloaters”

Cannot increase respiration enough to maintain PO2

Cyanosis and polycythemia

Fluid retention associated with right heart failure (cor pulmonale)

Bronchiectasis. Pathology, causes, manifestations.

Pathology: permanent dilation of the bronchi and bronchioles caused by destruction of the muscle and elastic supporting tissue as the result of a continuous cycle of infection and inflammation

Causes:

-Not a primary disease, but secondary to other conditions

-Necrotizing bacterial pneumonia complicating measles,pertussis, influenza

-Uncommon now due to antibiotic treatments and immunizations

—Tuberculosis, cystic fibrosis

Manifestations:

-Recurrent bronchopulmonary infection

-Coughing, production of large amount of purulent/bloody sputum

-Marked dyspnea and cyanosis

-Clubbing of the fingers

-Weight loss and anemia

Cystic fibrosis. Inheritance/cause.

Autosomal recessive disorder

Defective gene: cystic fibrosis transmembrane regulator (CFTR)

Cystic fibrosis. Consequences of the defective gene. Simple screen for CF?

Causes excessive, thick mucus that obstructs lungs and pancreas

High concentration of NaCl in sweat. Sweat test is a simple screen for it.

Manifestations of CF.

Chronic bronchiolitis and bronchitis

Bronchiectasis

Chronic infection (Pseudomonas aeruginosa, Staphylococcus aureus, Heamophilus influenzae)

Pulmonary embolism. Define. Common cause. Manifestations.

Blockage of blood flow in the pulmonary artery

Causes: Thrombus (majority), air, fat, amniotic fluid

Manifestations:

-Rapid and shallow breathing

-Pleuritic pain, productive cough of blood-streaked sputum

-Tachycardia

-Pulmonary hypertension and right heart failure

-Massive pulmonary emboli often are fatal

Pulmonary Hypertension. Define. Causes of secondary PH.

Elevation of pressure within pulmonary circulation

Mean pulmonary artery pressure ≥ 25 mmHg at rest, measured during right heart catheterization

Cause of Primary PH (rare):

Abnormal proliferation and contraction of vascular smooth muscle, marked intimal fibrosis

Causes of Secondary PH (majority):

Chronic hypoxemia due to COPD, ILD, or sleep-disordered breathing

Decreased pulmonary venous drainage (left ventricular diastolic dysfunction, mitral and aortic valve disorders)

Thromboembolic disorders (obstruction)

Increased pulmonary blood flow (left-to-right shunts, atrial or ventricular septal defects, patent ductus arteriosus)

Cor Pulmonale. Define, causes, manifestations.

Right heart failure secondary to primary lung disease or pulmonary hypertension

Manifestations of the primary lung disease:

Hypoxemia, hypercapnia

Manifestations of right-sided heart failure:

Right ventricular hypertrophy, eventual failure of the right ventricle

Systemic venous congestion (back up of blood), peripheral edema

Shortness of breath, productive cough

Polycythemia (hypoxia → kidney releases EPO → more RBCs made)

Acute Respiratory Distress syndrome. Define, causes/triggers.

ARDS is a life-threatening reaction to injuries (trauma, burns, aspiration, massive blood transfusion, drug use) or acute infection (infectious pneumonia, sepsis)

ARDS is a severe lung syndrome (not a primary disease) characterized by:

Severe dyspnea of rapid onset

Hypoxemia

Bilateral pulmonary infiltrates

ARDS Pathology

Pathology: diffuse epithelial cell injury with increased permeability of the alveolar-capillary membrane

Exudate enters alveoli

—Blocks gas exchange

—Makes inhalation difficult

Neutrophils enter alveoli → further injury…

—Release inflammatory mediators

—Release proteolytic enzymes

Acute Respiratory Failure. Define. Types and causes.

A condition in which the respiratory system fails in one or both of its gas exchange functions — oxygenation of blood and elimination of carbon dioxide (PO2 < 60 mmHg, PCO2 > 45 mmHg, or both)

Types:

Hypercapnic/hypoxemic respiratory failure (failure of ventilation):

Depression of the respiratory center

Diseases of respiratory nerves or muscles

Thoracic cage disorders

Hypoxemic respiratory failure (failure of gas exchange):

Mismatching of ventilation and perfusion (advanced COPD)

Impaired diffusion (interstitial lung disease, ARDS, pulmonary edema, pneumonia)