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2011-01-31 11:41:51

chapter 42
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  1. Maximun expiratory flow
    • When a person expires with great force, the airflow rate reaches a maximum above which even greater force will not increase rate
    • this force is much greater when the lungs are filled
  2. Increasing thoracic pressure
    • during expiration the increase in thoracic pressure not only forces air out of the avioli but also causes a collapse of the bronchioles by exerting force to the outside of them
    • after you have reached the maxof expiration any additional force will start to collapse the bronchioles and lower your rate of airflow
  3. As lung volume becomes smaller
    the max flow rate decreases
  4. What hold bronchioles open during chest expansion
    • elastic pull by external structures
    • as the thoracic cage decreases in size the bronchioles are more easily collapsed by external forces
  5. lung volumes compared to disease state
    • restrictive has a lower total capacity and a lower residual volume
    • obstructive has a larger total volume and residual volume
    • both have a deminished max exp flow rate
  6. Examples of restrictive disease
    • tuberculosis
    • silicosis
    • kyphosis
    • scoliosis
    • fibrotic pleuritis
  7. FEV1/FVC
    • normal is around 80%
    • obstructive disease this value is much lower; the FEV1 is greatly diminished and FVC is also slightly diminished
    • restrictive disease this value is increased; the FVC is much lower
  8. Physiologic changes with emphysema
    • chronic infection; inhaled smoke or the particles irritates the bronchioles and bronchi. Nicotine in smoke paralyses the cilia, this inhibits the clearance of mucus. Extra mucus is also produced. Macrophage activity is inhibited
    • the infection, extra mucus, and inflammatory edema of the bronchioles cause obstruction of smaller airways
    • the obstruction traps air in and over stretches the avioli. This causes destruction of the alveolar wall
  9. Physiological abnormalities of obstructive diseases
    • the bronchiole obstruction increases airway resistance, to overcome this resistance must expire harder which further leads tho brochiole collapse
    • The marked destruction of alveolar wall greatly decreases diffusion capacity
    • abnormal ventilation perfusion ratio, both dead space and shunting, because the obstructions are not uniform throughout the lungs
    • Loss of the alveolar wall also decreases pulmonary capillaries causing pulmonary hypertension. Chronically this can overload the right heart and cause cor pulminal
  10. pneumonia
    • any inflammatory condition of the lung in which alveoli are filled with fluid of blood
    • common type is bacterial caused by pneumococci, this disease starts with infection of the alveoli. The pulmonary membrane becomes inflamed and highly porous so that fluid and cells leak out of the blood into the alveoli.
  11. ventilation perfusion ratio during emphysema
    it is decreased, while the alveoli that are affected become filled with fluid they lose there ability to exchange gases with the blood. This decreases the available pulmonary membrane area. The blood still flows through this part of the lung so it is a shunt, not oxygenation the blood
  12. two main causes of atelectasis
    • obstruction of the bronchi with mucus or tumor, trapped air is absorbed and alveoli collapse
    • lack of surfactant
  13. Airway obstruction
    • the trapped air will be absorbed into the capillaries
    • if the alveolar tissue is pliable it will collapse, if not the air will be absorbed creating negative pressure in the alveoli which will then pull fluid into the alveoli.
    • During massive collapse of the lung it almost always becomes filled with fluid
  14. Blood flow during massive lung collapse
    • the capillaries in the collapsed lung are blocked structurally by the foling lung tissue and physiologically by the hypoxia causing vaso constriction
    • This routes most of the blood flow to the non collapsed lung and the blood stays well aerated, only a mild de-saturation occurs
  15. other name for repritory distress syndrome
    • hyaline membrane disease
    • not enough surfactant is produced
    • causes lungs to collapse or become filled with fluid
  16. Asthma is characterized by
    • spastic contractions of the bronchiole smooth muscle
    • partially obstructs the bronchioles
  17. usual cause of asthma
    contractile hypersensitivity of the bronchioles in response to a foreign material
  18. Allergic asthma
    • person forms abnormal amounts of IgE antibodies
    • the antibodies attach to mast cells in the lung, when these antibodies come into contact with there antigen they cause mast cell release
    • mast cells release histamine, slow reacting substances of anaphylaxis (mixture of leukotienes), eosinophile chemotactant factor, and bradykinin.
    • these factors produce local edema in the walls of the bronchioles as well as secretion of mucus, and spasm of smooth muscle
  19. Clinical measurements of an asthmatic person
    • reduced maximum expiratory rate
    • reduced timed expiratory volume
    • increased residual volume
  20. physical characteristic of asthmatic person
    barral chested
  21. Tuberculosis causes
    • caused by tubercle bacilli
    • the infected tissue is invaded by macrophages the the infected region os walled of by fibrous tissue forming a tubercle
    • The walling off is protective, in 3% of infected individuals the walling off process fails allowing bacteria to spread causing destruction and large abscess cavities
  22. late stages of TB
    • many areas of fibrosis thought the lungs
    • reduced amount of functional lung tissue
    • These effects cause increases work of the respiratory muscles and reduced vital capacity, reduced membrane surface area diminishing diffusion capacity, abnormal ventilation perfusion ratio
  23. Classification of causes of hypoxia
    • inadequate oxygenation of the lungs due to extrinsic factors; low atmospheric oxygen, hypoventilation
    • pulmonary disease; hypovetilation from increased resistance or decreased pulmonary compliance, abnormal ventilation perfusion ratio, diminished membrane diffusion
    • venous to arterial shunts
    • inadequate oxygen transport to tissues by blood; anemia or abnormal hemoglobin, tissue edema, vessel disease
    • inadequate tissue capability of using oxygen; beriberi, toxicity
  24. cyanide poisoning
    • causes inability of the tissues to use oxygen
    • blocks action of cytochrome oxidase, last step in electron transport chain
  25. beriberi
    can not utilize oxygen due to a vitamin B deficiency
  26. effects of hypoxia on the body
    • depresses mental activity, can lead to coma
    • reduced work capacity of muscles
  27. Oxygen therapy
    • atmospheric hypoxia; can almost completely correct
    • hypoventilation hypoxia; can allow 5 times more oxygen in with each breath so is helpful, does not help with hypercapnea though
    • hypoxia caused by improper alveolar membrane diffusion; works by increasing the pO2 gradient. Patient with edema will pick up three times more oxygen with each breath
    • hypoxia caused by anemia; oxygen therapy has much less value since oxygen is readily available. Increased alveolar oxygen can increase the amount dissolved, this is very little but may help
    • inadequate use; no benefit to therapy
  28. cyanosis
    • caused by deoxygenated hemoglobin
    • appears when blood contains more then 5grams of deoxy hemoglobin per 100ml of blood
    • person with anemia never becomes cyanotic because there is not enough hemoglobin for 5% to become deoxygenated
    • person with polycythemia vera frequently becomes cyanotic because of the large excess of RBCs
  29. hypercapnia
    • excess carbon dioxide in the body
    • occurs with hypoxia only when the hypoxia is caused by hypoventilation or circulatory deficiency
    • does not usually occur with diminished diffusion through pulmonary membrane because it diffuses 20x more easily then oxygen, if CO2 did get high enough it would stimulate increased ventilation which would fix the co2 but not help the oxygen
    • At extremely high levels of co2 the respiratory center is actually depressed causing a vicous cycle of more co2 build up and more depression, this can lead to coma and death
  30. Dyspnea
    • mental anguish associated with inability to ventilate enough oxygen to satisfy demand
    • air hunger
  31. three factors that enter into the development of dyspnea
    • abnormality of respiratory gases; mainly hypercapnea
    • amount of work the respiratory muscles must do; sometimes the gases are normal but the forceful respiration to get them there cause dyspnea
    • state of mind; neurologic or emotional dyspnea