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CHAPTER 13Respiratory System

Physiology of Lungs75%of quiet respiration comes from diaphragmatic action. At rest, 6-8 liters/min air taken

in. At maximum ventilation intake exceeds 125 liters/min. In one day we inhale 10,000 liters.Intrathorasic pressure approximately -2.5 mm Hg. During inspiration that drops to about -6

mm Hg.

The airway branches approximately 23 times from trachea to terminal alveolar sacs. There isno oxygen exchange in the first 16 branches even though the surface area in these first 16

branches is 2000 that of the trachea. There a re approximate ly 300 million alveolar sacs and hasa surface area of 750 square feet.

Only 70% of inspired air reaches the alveolar sacs. During expiration, about 85% of inhaledair is expelled in the first second but it takes two more seconds to expel another 12-15% duringmaximum effort.

Particles greater than 10 micrometer stay within the tidal flow of air. Particles 3-10 :m gettrapped by cilia on trachea and bronchus. Coughing and sneezing and cilia generally remove

these. Particles less than 3 :m reach terminal alveolar sacs. These are removed by macrophages.

ATELECTASIS (collapse or loss of lung volume). (slide 8)Resorption Atelectasis: Airway obstruction results in continued absorption of air from

the lungs with gradual collapse. (reversible)

Compression Atelectasis:Results from fluid, blood, or air in the thorax. Pneumothoraxand congestive heart failure among the most common causes. (reversible)

-pneumothorax usually from trauma introducing air

- resorption and compression are the most common

Microatelectasis: (non-obstructive atelectasis) Adult Respiratory Distress Syndrome(ARDS) and Neonatal Respiratory Distress Syndrome (NRDS). Commo nly results froma lack of surfactant in NRDS. Post surgery, lungs cannot reinflate. (inflammatoryproblems, structure of the lung problem- irreversible)

Contraction Atelectasis:Scar formation. A non-reversible process whereas the othersmay be (but not always).

OBSTRUCTIVE LUNG DISEASES(The four biggies are asthma, emphysema, chronicbronchitis and cystic f ibrosis.) see Table 13-2

Asthma: (reversible)-inflammatory problem- difficutly in breathing, expiring

Extrinsic - type I hypersensitivity response. Atopic asthma the most common form.

Atopic asthma gene rally has two phases, an acu te phase which occurs withi n minutes ofexposure. The second phase occurs hours later (sort of a relapse phase which lasts longerthan the acute phase). Status asthmaticus is a protracted condition. (IgE reactions w/smooth muscle component)(slide 14) mast cell degranulation on mucosal surface and submucosal

Bronchiole constriction and the thick mucus causes airway obstruction and the

wheezing associate d with asthma.

Intrinsic - non-immune mediated. Most often stress, exercise, or irritant induced.

Chronic Obstructive Pulmonary Diseases (COPD)

A group of pulmonary con ditions that cause s irreversible airway obst ruction (unlike asthma ).

Emphysema: Overinflation results in rupture of alveolar sacs. While there are three"flavors" of emphysema, they are not easy to distinguish among them. The mostsevere form is that which results from a deficiency of alpha-1 antitrypsin deficiency .

Smoking recruits PMNs which produces excess elastase. Clinical signs includedyspneaand hyperventilation . Death results from respiratory acidosis or right-sided heart failure.

Chronic Bronchitis:Smokers or persons living in smog-laden areas. Diagnosticcriteria are: 1) persistent productive cough and 2) lasting at least 3 consecutivemonths in 2 consecutive years. Results in fibrosis (scarring), inflammation and

bronchiole narrowing. Ex cess mucus produ ction a feature of CB as well. Generallyproduces cyanosis . Occasionally, CB and emphysema overlap.

Bronchiectasis: permanent dilation of bronchioles. Results from obstructions such astumors or foreign bodies, cystic fibrosis, immunodeficiencies, or chronic necrotizingpneumonias (resulting in scar formation).

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Ex.) Cystic Fibrosis: severe bronchiectasis from constant infection brought about bycopious mucous production. The most lethal AR disorder that affects whites.

RESTRICTIVE LUNG DISEASESResult in loss of compliance of lung tissues (become stiff).Interstitial disease.

Acute Restrictive Dise asesEx.):Adult Respirator y Distress Syndrome (ARDS)1) decreased arterial

oxygen pressure, 2) decreased compliance, and 3) pulmonary infiltrates without left-sided heart failure. See Table 13-1for list of causative factors. >+ 50% mortality.

Chronic Restrictive Diseases(an interstitial disease) Table 13-3lists some causes.Forced vital capacity (FVC) and forced expiratory volume (FEV) both reduced but notthe ratio between the two.

Ex.): Idiopathic (cryptogenic) Pulmonary Fibrosis: Interstitial infiltrate andedema. Macrophages secrete growth factors which causes fibroblastic

proliferation. Loss of type I pneumocytes and replacement by type IIpneumocytes. Death commonly results from cor pulmonale and heart failure.Prognosis unpredictable.

VASCULAR LUN G DISEASES

Embolism/Thromboembolism: From venous or right ventricle emboli. Results in~50,000 deaths a year in hospitals. The vast majority of pulmonary thrombi are silent(60-80%). 95% result from deep leg thrombi. (Hip fractures were a common cause; but,current therapy has reduced the incidence.) Usually more than 60% pulmonaryocclusion required to cause death (although several small infarcts may result in death).

PULMONARY INFECTIONS

Lobar Pneumonia:Consolidated and involves one (or two) lobes. Typically, the organisminvolved isStreptococcus pneumon iaeor "pneumococcus" (90%+) which also accountsfor most "community acquired" infections.

Bronchopneumonia:also known as "patchy" pneumonia. Less specific than lobarpneumonia.

Tuberculosis:Mycobacterium tu berculosiscauses 8-10 million new infection a year andabout 3 million deaths. About 25,000 new cases in USA a year. A type IV hypersensitivityreaction causes most damage associated with TB.

Primary TB: Ghon focus. The primary lesion and contiguous lymph node(s) createthis lesions.

Secondary TB:classically located at the apex of one or both lungs. Cavitation alsoconsistent. Miliary TB involves multiple sites and may become systemic. Pott disease (TBin vertebrae) and Addison disease (uncommon today).

LUNG TUMORS

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95% arebronchogenic carcinoma . 40-70 years, males (2X that of females). Smokers 5-10 times more like to die. 80% of lung cancers occur in heavy smokers. Exposure to asbestosincreases the risk by 55 times.

2 major groups:

a.non-small cell type-

b. small cell type-

Malignant Mesothelioma:a tumor arising from pleural surface. Almost alwaysassociated with asbestos.