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Atelectasis

Atelectasis. Causes : airway obstruction with mucus and solid object Lack of surfactant in fluids lining the alveoli Effects : Lung collapse lead to compression of veins increase blood flow resistance Additional vasoconstriction due to hypoxia in collapsed alveoli. Atelectasis.

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Atelectasis

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  1. Atelectasis Causes: • airway obstruction with mucus and solid object • Lack of surfactant in fluids lining the alveoli Effects: • Lung collapse lead to compression of veins • increase blood flow resistance • Additional vasoconstriction due to hypoxia in collapsed alveoli

  2. Atelectasis • Vasoconstriction lead to decrease blood flow through Atelectasislung: • 1)blood5/6 passes to aerated lung • 2)Blood 1/6 passes to unaeratedlung • V/Q ratio is moderately compromised • only mild oxygen desaturation in aortic blood despite total loss of ventilation in an entire lung

  3. Lack of surfactant as a cause of lung collapse • Special alveolar epithelial cells secrete surfactant leads to fluid that coat inside surface of alveoli lead to 2-10 times decrease surface tension in alveoli which prevents alveolar collapse • In case of RDS in newborn premature babies, alveoli lead to decrease surfactant result in increase surface tension lead to lung collapse patient may die due to suffocation with Atelectasis.

  4. Tuberclosis • A constrictive lung disease Etiology: tubercle bacilli lead to tissue reaction in lungs lead to Pathology: • Macrophage invasion • Walling off of lesion by fibrous tissue leading to tubercle formation • If untreated in 3% walling off fails • Massive destruction of lung tissue • Large abcess cavities • Late stages= increase fibrous tissue and decrease function of lung tissue.

  5. Physiologic abnormalities of tuberculosis: • Increase work of breathing by respiratory membrane • Decrease respiratory membrane surface area • Increase thickness of respiratory membrane • Decrease vital capacity • Decrease breathing capacity • Decrease pulmonary diffusion capacity • Abnormal ventilation perfusion ratio

  6. pneumonia • It is an infection of pulmonary parenchyma. • It may involve primarily the interstium or alveoli • Caused by viruses,fungi,and parasites.

  7. Pneumonia • Involvement of entire lobe is called LOBAR PNEUMONIA • Involvement of alveoli contiguous to bronchi is called BRONCHOPNEUMONIA

  8. pneumonia • Abnormalities of function (Pathology): • Consolidation of lung occurs i.e, alveoli are filled with blood cells and fluids • Pulmonary membrane becomes inflamed and porous so leaking occurs. • Decrease total surface area of respiratory membrane • Decrease V/Q ratio which results in hypoxemia and hypercapnia

  9. DYSPNEA = Air Hunger Dyspnea: shortness of breath (SOB), or air hunger, is the subjective symptom of breathlessness. 3 factors that cause the sensation of dyspnea: 1) Abnormality of respiratory gases in body fluids (mainly hypercapnia & partly hypoxia) 2) Increase work of breathingby respiratory muscles to breath forcefuly e.g. in asthma 3) State of Mind (neurogenic/emotional dyspnea) • More enhanced in people who are claustrophobic (fear of not being able to receive a sufficient quantity of air e.g., small or crowded places).

  10. HYPERCAPNIA: DEFINITION: • Excess CO2 in body fluids. • (Hypercapnia + Hypoxia): Only when hypoxia is caused by hypoventilation or circulatory deficiency.

  11. Causes of hypoxia + hypercapnia (simultaneously): • In hypoxia due to hypoventilation, CO2 transfer between alveoli & atmosphere is affected as much as is oxygen transfer. • In circulatory deficiency  decreased blood flow  decreased removal of CO2 from the tissues  tissue hypercapnia + hypoxia. • But transport capacity of blood for CO2 is more than 3 times that for O2, so resulting tissue hypercapnia in much less than tissue hypoxia.

  12. Severe hypercapnea • When alveolar PCO2 rises above about 60-75 mm Hg  air hunger / dyspnea becomes severe. • If PCO2 rises to 80-100 mm Hg  lethargy, +/- semicomatose • If PCO2 rises to 120 to 150 mm Hg  + / - anesthesia & death • At such high PCO2  Resp. Centre is depressed rather than stimulated  vicious circle

  13. ASPHYXIA: DEFINITION: Simultanoeus acute hypoxia & hypercapnia. CAUSES: • Acute airway obstruction • When a person is forced to re-breathe his own air in a confined space.

  14. Mechanism: • During asphyxia  hypoxia + hypercapnia strong stimulation of respiratory centre & violent inspiratory efforts  heart rate increases, BP increases, CATS increase from adrenal medulla (increase in nor-epinephrine > epinephrine)   unconsciousness, convulsions & decrease in respiratory rate  death.

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