Khairat Battah, MD The University of Jordan Faculty of medicine, pathology department.

The respiratory systemKhairat Battah, MD

The University of JordanFaculty of medicine, pathology department

Is loss of lung volume caused by inadequate expansion of airspaces.

It results in shunting of inadequately oxygenated blood from pulmonary arteries into veins, thus giving rise to a ventilation- perfusion imbalance and hypoxia.

I. Atelectasis (Collapse)

Due to total obstruction of a bronchus by mucus plug and it occurs postoperatively.

Other causes: foreign body aspiration, particularly in children, asthma, chronic bronchitis and tumors.

- The total obstruction prevents air from reaching distal airways and the air already present gradually becomes absorbed, and alveolar collapse follows.

1.Resorption atelectasis

Passive or relaxation atelectasis caused by:a. Pleural effusion, caused mostly by congestive heart

failure (CHF)b. Pneumothorax: air in the pleural cavityc. Elevated position of the diaphragm that occurs in

bedridden patients and in ascites (Basal atelectasis)

2. Compression atelectasis

Occurs in local or generalized fibrosis of the lung or pleura that prevents full expansion of the lung.

Atelectasis (except when caused by contraction) is potentially reversible and should be treated promptly to prevent hypoxemia and superimposed infection.

3. Contraction atelectasis

Clinical syndrome caused by diffuse alveolar capillary and epithelial damage (DAD).

Characterized by :a. Rapid onset of respiratory insufficiency, dyspnea.b. Cyanosis c. Severe arterial hypoxemia that becomes refractory to

oxygen therapy and may progress to multisystem organ failure.

Acute Respiratory Distress Syndrome (ARDS)

Causes of ARDS in adults:1. Direct lung injury: atypical pneumonia and ,

aspiration of gastric content2. Indirect lung injury: sepsis , shock, trauma

Respiratory distress syndrome of the newborn is caused by a primary deficiency of surfactant.

Causes:

The integrity of the alveolar-capillary membrane barrier is compromised by either endothelial or epithelial injury, or, more commonly, both. 

This leads increased vascular permeability and alveolar flooding, loss of diffusion capacity, and widespread surfactant abnormalities caused by damage to type II pneumocytes

 Neutrophils are thought to have an important role in the pathogenesis of ARDS

The balance between the destructive and protective factors is what determines the degree of tissue injury and clinical severity of ARDS.

PATHOGENESIS

Acute stage: - The lungs are dark red, firm, airless, and heavy - The most characteristic finding is the presence

of hyaline membranes, particularly lining the distended alveolar ducts.

  Chronic organization stage: • Proliferation of type II pneumocytes • Organization of the fibrin exudates, with resultant

intra-alveolar fibrosis• Marked thickening of the alveolar septa.

MORPHOLOGY

85% of patients develop ARDS within 72 hours of the initiating insult.

- The mortality rate has decreased from 100% to 60% in the last decade.

Clinical Features

Predictors of poor prognosis include :a. Advanced age.b. Underlying sepsisc. Development of multisystem failure If the patient survive the acute stage, diffuse interstitial

fibrosis may occur, with continued compromise of respiratory function

However, in most patients who survive the acute insult and are spared the chronic sequelae, normal respiratory function returns within 6 to 12 months.

Obstructive disease (airway disease), characterized by limitation of airflow usually resulting from an increase in resistance caused by partial or complete obstruction at any level.

Always show a decrease in expiratory flow rates.

Obstructive lung diseases

Emphysema Chronic bronchitis Bronchiectasis Asthma

Chronic obstructive lung diseases (COPD)

Abnormal permanent enlargement of the airspaces with destruction of their walls and no fibrosis.

a. Centriacinar (Centrilobular) Emphysema- Most common, Caused by cigarette smoking, upper

lobes b. Panacinar (Panlobular) Emphysema - Occurs in α1-antitrypsin deficiency, basal lobes.

1. Emphysema

c. Distal Acinar (Paraseptal) Emphysema - Is more striking adjacent to the pleura,- Adjacent to fibrosis, scarring or atelectasis. - Characterized by presence of multiple, enlarged air spaces

ranging from less than 0.5 mm to more than 2.0 cm, that may form large cysts called bullae.

Is the most common cause of spontaneous pneumothorax in young adults.

o Dyspnea that begins insidiously but is steadily progressiveo The classical presentation is that the patient is barrel-chested

and dyspneic, sitting forward in a hunched-over position, attempting to squeeze the air out of the lungs with each expiratory effort, with an obviously prolonged expiration.

Hyperventilation is prominent, so in early disease the gas exchange is adequate.

Overventilation helps them remain well oxygenated (pink puffers).

With time pulmonary hypertension develops.

Clinical Course

Compensatory emphysema (overinflation): - Compensatory dilation of alveoli in response to loss of lung

substance such as occurs in residual lung parenchyma after surgical removal of a diseased lung

- Is not a true emphysema

Related conditions:

Obstructive overinflation: - Expansion of the lung because air is trapped within it

and the common cause is subtotal obstruction by a tumor or foreign object.

- It can be a life-threatening emergency if it compress the remaining normal lung

Bullous emphysema : Any form of emphysema that produces large sub-

pleural bullae (spaces greater than 1 cm), and may rupture, leading to pneumothorax.

Mediastinal (interstitial) emphysema: Entry of air into the connective tissue of the lung,

mediastinum and subcutaneous tissue.

a. May be spontaneous with a sudden increase in intra-alveolar pressure as with vomiting or violent coughing resulting in a tear, with dissection of air into the interstitium .

b. In children with whooping cough. c. In persons who suffer a perforating injury (e.g., a

fractured rib).

- When the interstitial air enters the subcutaneous tissue, the patient may blow up like a balloon, with marked swelling of the head and neck.

- Mostly the air is resorbed spontaneously after the site of entry is sealed.

Defined by the presence of a persistent productive cough for at least 3 consecutive months in at least 2 consecutive years.

Is common among cigarette smokers In early stages of the disease, the productive cough

raises mucoid sputum, but airflow is not obstructed. Later chronic obstructive bronchitis develops. Although the single most important cause is cigarette

smoking, other air pollutants may contribute.

II. Chronic Bronchitis

The distinctive feature of chronic bronchitis is hypersecretion of mucus, a reflection of large airway disease.

The morphologic basis of airflow obstruction in chronic bronchitis is more peripheral and results from:

1. Small airway disease: (chronic bronchiolitis) is component of early and relatively mild airflow obstruction. (mucus plugging of the bronchiolar lumen, inflammation, and bronchiolar wall fibrosis)

2. Coexistent emphysema: The cause of significant airflow obstruction.

pathogenesis

- Prominent cough with production of sputum may persist indefinitely without ventilatory dysfunction.

- Some patients develop significant COPD (chronic obstructive pulmonary disease) with outflow obstruction and this is accompanied by hypercapnia, hypoxemia, and cyanosis ( term "blue bloaters").

- With progression, chronic bronchitis is complicated by pulmonary hypertension and cardiac failure.

- Recurrent infections and respiratory failure are constant features.

Clinical Features:

Recurrent episodes of wheezing, Dyspnea, chest tightness and cough, and its hallmarks are :

a. Intermittent and reversible airway obstruction (bronchospasm)

b. Chronic bronchial inflammation with eosinophils,c. Bronchial smooth muscle cell hypertrophy and

hyper-reactivity.d. Increased mucus secretion.

III. Asthma

1. Atopic Asthma : Is the most common type.a. Usually beginning in childhood.b. Positive family history of allergy.c. The asthmatic attacks are preceded by allergic rhinitis,

urticaria, or eczemad. The disease is triggered by environmental antigens, such as

dusts, pollene. Skin test with the antigen results in an immediate wheal-and-

flare reaction

Types of Asthma

2. Non-Atopic Asthma a. Negative skin test. b. A positive family history of asthma is less common.c. Exposure to viral infections and air pollutants is common

trigger. 3. Drug-Induced Asthma: Aspirin induced asthma and patients with aspirin sensitivity

present with recurrent rhinitis ,nasal polyps , urticaria, and bronchospasm.

- Dyspnea with wheezing; and the chief difficulty lies in expiration so the victim labors to get air into the lungs and then cannot get it out so progressive hyperinflation of the lungs takes place with air trapped distal to the bronchi which are constricted and filled with mucus and debris.

- In the usual case, attacks last from 1 to several hours and subside either spontaneously or with therapy.

- Intervals between attacks are free from respiratory difficulties.

Clinical Features

- Occasionally a severe paroxysm occurs that does not respond to therapy and persists for days or weeks (status asthmaticus).

- The associated hypercapnia, acidosis, and severe hypoxia may be fatal.

Bronchiectasis is the permanent dilation of bronchi and bronchioles caused by destruction of the muscle and elastic supporting tissue, resulting from or associated with chronic necrotizing infections.

Secondary to persisting infection or obstruction caused by a variety of conditions

IV. Bronchiectasis

characteristic symptom complex dominated by cough and expectoration of copious amounts of purulent sputum.

Bronchial obstruction. Common causes are tumors, foreign bodies, and occasionally impaction of mucus (localized)

Atopic asthma and chronic bronchitis. Congenital or hereditary conditions. In cystic fibrosis

(widespread), immunodeficiency states, Kartagener syndrome,

Necrotizing, or suppurative, pneumonia, particularly with virulent organisms such as Staphylococcus aureus or Klebsiella .

Causes:

Two processes are crucial and intertwined in the pathogenesis of bronchiectasis:

 Obstruction  Chronic persistent infection.

PATHOGENESIS

Severe, persistent cough with expectoration of mucopurulent sputum.

Sputum may contain flecks of blood. Symptoms often are episodic. Clubbing of the fingers may develop. In cases of severe, widespread bronchiectasis,

significant obstructive ventilatory defects develop, with hypoxemia, hypercapnia, pulmonary hypertension, and (rarely) cor pulmonale.

Clinical Features

- Pulmonary blood pressures are only about one eighth of systemic pressures.

- Pulmonary hypertension (when mean pulmonary pressures reach one fourth or more of systemic levels) is most often secondary to other lesions:

a. Chronic obstructive or interstitial lung disease. b. Recurrent pulmonary emboli

c. Congenital left-to-right shunts

Pulmonary Hypertension

Uncommonly, pulmonary hypertension is primary (all known causes of increased pulmonary pressure have been excluded), idiopathic pulmonary arterial hypertension.

- Primary pulmonary hypertension is seen in young adults females and is marked by fatigue, syncope (particularly on exercise), dyspnea on exertion and chest pain.

- Eventually severe respiratory insufficiency and cyanosis develop , and death usually results from right side heart failure

- Without lung transplantation the prognosis is grim.

Clinical Features

Can be broadly defined as any infection in the lung and the clinical presentation may be as an acute fulminant clinical disease or as a chronic disease with a more protracted course.

Pneumonia :

A. Community acquired acute pneumonia- Most are bacterial in origin and Strep. pneumoniae is

the most common - The onset usually is abrupt, with high fever, shaking

chills, pleuritic chest pain and a productive mucopurulent cough.

Pneumococcal infections occur with increased frequency in 1. Those with CHF, COPD, or diabetes;2. Those with either congenital or acquired

immunoglobulin defects. 3. Those with decreased or absent splenic function (e.g.,

sickle cell disease or after splenectomy).- Such infections are more likely because the spleen

contains the largest collection of phagocytes and is therefore the major organ responsible for removing pneumococci from the blood.

- With appropriate therapy, complete restitution of the lung is the rule but in occasional cases complications may occur:

1. abscess formation;2. Suppurative material may accumulate in the pleura

producing an empyema;3. Bacteremic dissemination may lead to meningitis,

arthritis, or endocarditis

Other Important Pathogens Haemophilus influenzae Moraxella catarrhalis Staphylococcus aureus Klebsiella pneumoniae Pseudomonas aeruginosa Legionella pneumophila

B. Community-Acquired Atypical Pneumonias - An acute febrile respiratory disease characterized by

patchy inflammatory changes in the lungs, largely confined to the alveolar septa and pulmonary interstitium

- The designation atypical denotes:a. The moderate amounts of sputum. b. Absence of physical findings of consolidation. c. Moderate elevation of white cell count.d. Lack of alveolar exudates.

Mycoplasma pneumoniae is the most common, which is particularly common among children and young adults.

Other etiologic agents are: Viruses, including influenza types A and B, the respiratory

syncytial viruses, human metapneumovirus, adenovirus, rhinoviruses, rubeola virus, and varicella virus.

Chlamydia pneumoniae Coxiella burnetii (the agent of Q fever)

The clinical course is extremely varied - May present as a severe upper respiratory tract infection

or it may manifest as a fulminant, life-threatening infection in immunocompromised patients.

- The initial presentation usually is an acute, nonspecific febrile illness characterized by fever, headache, and malaise and, later, cough with minimal sputum.

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