Pulmonary Pathophysiology

Histology of the lungRespiratory epitheliumConnective tissue fibers, and cartilage: support and maintain open air wayAlveolar cells (type I and type II)

Capillary lumenType I pneumocyteType I pneumocyteType IIpneumocyteEndotheliumAlveolar space

Normal Lung

Function of the lungGas exchangeProtection against infection by alveolar macrophagesSurfactant secretion: allow expansion of alveoli with air

Lung function testsTidal volume (TV): it is the amount of gas inhaled or exhaled with each resting breath.Residual volume (RV): it is the amount of gas remaining in the lungs at the end of maximum exhalation.

Vital capacity (VC): it is the total amount of gas that can exhaled following maximum inhalation.Total lung capacity (TLC): it is the amount of gas in the lung at the end of maximum inhalation.TLC = RV+ VC

Reduction of Pulmonary FunctionInadequate blood flow to the lungs: hypoperfusionInadequate air flow to the alveoli: hypoventilation

Noso-comial infectionsFactors that reduce airflow also compromise particle clearance and predispose to infection.High rate of pneumonia in hospital patients due in large part to impaired ventilation and clearance.

Restricted lung movement and ventilation may arise due to:PositioningConstricting bandagesCentral nervous system depressionComa

Signs and Symptoms of Pulmonary Disease

1- Dyspnea: subjective sensation of uncomfortable breathing, feeling short of breathRanges from mild discomfort after exertion to extreme difficulty breathing at rest.Usually caused by diffuse and extensive rather than focal pulmonary disease.

Causes of Dyspnea :Airway obstruction Greater force needed to provide adequate ventilationWheezing sound due to air being forced through airways narrowed due to constriction or fluid accumulationDecreased compliance of lung tissue

Signs of dyspnea:Flaring nostrilsUse of accessory muscles in breathingRetraction (pulling back) of intercostal spaces

2- CoughAttempt to clear the lower respiratory passages by forceful expulsion of airMost common when fluid accumulates in lower airways

Causes of Cough:Inflammation of lung tissueIncreased secretion in response to mucosal irritationInhalation of irritantsIntrinsic source of mucosal disruption such as tumor invasion of bronchial wallExcessive blood hydrostatic pressure in pulmonary capillariesPulmonary edema excess fluid passes into airways

When cough can raise fluid into pharynx, the cough is described as a productive cough, and the fluid is sputum.Production of bloody sputum is called hemoptysisNot threatening, but can indicate a serious pulmonary diseaseTuberculosis, lung abscess, cancer, pulmonary infarction.

If sputum is purulent------- infection of lung or airway is indicated.Cough that does not produce sputum is called a dry, or nonproductive cough.Acute cough is one that resolves in 2-3 weeks from onset of illness or treatment of underlying condition.Acute cough caused by upper respiratory tract (URT) infections, allergic rhinitis, acute bronchitis, pneumonia, congestive heart failure, pulmonary embolus, or aspiration.

A chronic cough is one that persists for more than 3 weeks.In nonsmokers, almost always due to postnasal drainage syndrome, asthma, or gastroesophageal reflux diseaseIn smokers, chronic bronchitis is the most common cause, although lung cancer should be considered.

3- CyanosisWhen blood contains a large amount of unoxygenated hemoglobin, it has a dark red-blue color which gives skin a characteristic bluish appearance.Most cases arise as a result of peripheral vasoconstriction result is reduced blood flow, which allows hemoglobin to give up more of its oxygen to tissues- peripheral cyanosis.Best seen in nail bedsDue to cold environment, anxiety, etc.

Central cyanosis can be due to :Abnormalities of the respiratory membraneMismatch between air flow and blood flowExpressed as a ratio of change in ventilation (V) to perfusion (Q) : V/Q ratioPulmonary thromboembolus ---- reduced blood flowAirway obstruction ---- reduced ventilationIn persons with dark skin can be seen in the whites of the eyes and mucous membranes.

Lack of cyanosis does not mean oxygenation is normal!!In adults not evident until severe hypoxemia is presentClinically observable when reduced hemoglobin levels reach 5 g/ dl.Severe anemia and carbon monoxide poisoning give inadequate oxygenation of tissues without cyanosisIndividuals with polycythemia may have cyanosis when oxygenation is adequate.

4- PainOriginates in pleurae, airways or chest wallInflammation of the parietal pleura causes sharp or stabbing pain when pleura stretches during inspirationUsually localized to an area of the chest wall, where a pleural friction rub can be heardLaughing or coughing makes pain worseCommon with pulmonary infarction due to embolism

Inflammation of trachea or bronchi produce a central chest pain that is pronounced after coughingMust be differentiated from cardiac painHigh blood pressure in the pulmonary circulation can cause pain during exercise that often mistaken for cardiac pain (angina pectoris).

5- ClubbingThe selective bulbous enlargement of the end of a digit (finger or toe).Usually painlessCommonly associated with diseases that cause decreased oxygenationLung cancerCystic fibrosisLung abscessCongenital heart disease

Infectious Diseases of The Lungs

Introduction:Daily 10,000 liters of air - filtered..!Pneumonia: Inflammation of lung.Respiratory tract infections commonest in medical practice.Enormous morbidity & mortality.

Etiology:Decreased general resistanceVirulent infection - Lobar pneumoniaClearing mechanismDecreased Cough ReflexInjury of the cilia and mucosa Low alveolar defense Pulmonary edema or congestionObstructionsRetention of secretions

Types:ViralBacterialMycoplasmalFungal

Patterns of infections:Airway - Bronchitis, BronchiectasisParenchymaPneumonia BronchopneumoniaLobar pneumoniaLung abscessTuberculosis

PneumoniaPathology:AlveolarBronchopneumonia (Streptococcus pneumoniae, Haemophilus influenza, Staphylococcus aureus)Lobar (Streptococcus pneumoniae)Interstitial (Influenza virus, Mycoplasma pneumoniae)PathogenesisInhalation of air dropletsAspiration of infected secretions or objectsHematogenous spread

BronchopneumoniaSuppurative inflammation of lung tissue caused by Staph, Strep, Pneumo & H. influenzaPatchy consolidation not limited to lobes.Usually bilateralLower lobes common, but can occur anywhereComplications:AbscessEmpyemaDissemination

Broncho-pneumonia

Broncho-pneumonia

Broncho-pneumonia

Bronchopneumonia:

Bronchopneumonia

Lobar Pneumonia:Fibrinosuppurative consolidation whole lobeRare due to antibiotic treatment.~95% - Strep pneumoniaeThe course runs in four stages: Congestion.Red Hepatization.Gray Hepatizaiton.Resolution.

Lobar pneumoniaLobar pneumonia: whole lobe(s) involved

Fixed specimen, grey hepatization

Lobar Pneumonia:

Lobar Pneumonia Gray hep

Lung Abscess:Focal suppuration with necrosis of lung tissueOrganisms commonly cultured:StaphylococciStreptococciGram-negativeAnaerobesFrequent mixed infectionsMechanism:AspirationPost pneumonicSeptic embolismNeoplasmsProductive Cough, fever.ClubbingComplications: Systemic spread, septicemia.

Lung Abscess:

Abscess formation

Bronchopneumonia - Abscess formation

Lung Abscess:

Pulmonary tuberculosisCaused by Mycobacterium tuberculosis.Transmitted through inhalation of infected dropletsPrimarySingle granuloma within parenchyma and hilar lymph nodes (Ghon complex).Infection does not progress (most common).Progressive primary pneumoniaMiliary dissemination (blood stream).

Ghon complex

Pulmonary tuberculosisSecondaryInfection (mostly through reactivation) in a previously sensitized individual.PathologyCavitary fibrocaseous lesionsBronchopneumoniaMiliary TB

FibrocaseousGranuloma

Miliary TB

Opportunistic pneumoniasInfections that affect immunosuppressed patientsAssociated disorders:AIDSIatrogenic Cancer patientsTransplant recipients

Usual interstitial pneumonia / idiopathic pulmonary fibrosisProgressive fibrosing disorder of unknown causeAdults 30 to 50 years oldRespiratory and heart failure (cor pulmonale) ~ 5 y

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