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Respiration upload4


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Respiration upload4

  1. 1. Overall Summary<br />
  2. 2. Respiratory Response to High Altitude<br />Plus, increased:<br />No. of RBCs, diffusing capacity of the lungs, vascularity of the peripheral tissues, ability of tissue cells to use O2 (despite low Po2)<br />
  3. 3. Respiratory Response to High Altitude<br />Hypoxemia causes hyperventilation<br /> Hyperventilation causes decrease in Pco2 & respiratory alkalosis (RA)<br />These 2 inhibit CNS respiratory centre (‘offsetting’ ++ drive of hypoxemia)<br />Body’s solution: <br />Renal HCO3- excretion increased – RA resolved (via increased excretion of CSF HCO3-)<br />Hyperventilation now will not be ‘offset’ because now, O2 is the drive* via PCR!<br />
  4. 4. Acute Mountain Sickness<br />Symptoms due to hypoxia and RA<br />Headache, fatigue, dizziness, nausea, palpitations, and insomnia<br />Pulmonary & cerebral edema are serious<br />Prevention: Acclimatization<br />Treatment: Acetazolamide <br />
  5. 5. Respiratory Response to Exercise<br />CNS influences respiratory response<br />Anticipatory increase in ventilation at exercise onset<br />Leads to an initial decrease in Pco2<br />Afterwards, the increased Pco2 ‘matches’ the ventilation rate<br />
  6. 6. Summary<br />
  7. 7. Periodic Breathing<br />Person breathes deeply (short interval) - then breathes slightly or not at all for an additional interval <br />Cycle repeating itself over and over <br />Cheyne-Stokes breathing<br />slowly waxing and waning respiration occurring about every 40 to 60 secs<br />
  8. 8. Hypoxemia<br />
  9. 9. Hypoxia & O2 therapy<br />Decreased O2 delivery to the tissues<br />Causes:<br />Inadequate oxygenation of blood in lungs (extrinsic reasons)<br />Oxygen deficiency in atmosphere<br />Hypoventilation (neuromuscular disorders)<br />Disease of the lung itself<br />Abnormal V/Q <br />Damaged respiratory membrane<br />Decreased compliance etc<br />Venous-to-arterial shunts (“right-to-left” cardiac shunts)<br />Inadequate O2 transport to tissues by blood<br />Anemia or abnormal hemoglobin<br />General circulatory deficiency<br />Localized circulatory deficiency (peripheral, cerebral, coronary vessels)<br />Tissue edema<br />Inadequate tissue capability of using O2<br />Cyanide poisoning<br />Vitamin-B deficiency (Beri-beri)<br />
  10. 10. Hypoxia<br />Hypoxic hypoxia <br />PO 2 of the arterial blood is reduced; <br />Anemic hypoxia <br />Arterial PO 2 is normal but amount of Hb reduced <br />Stagnant  or ischemic hypoxia <br />Blood flow to a tissue is so low that adequate O2 is not delivered (despite normal PO2 & Hb)<br />Histotoxic hypoxia<br />Tissue cells cannot make use of the O2 supplied<br />
  11. 11. Hypoxia <br />Signs<br />Cyanosis<br />Tachypnea (rate) & Hyperpnea (depth)<br />Tachycardia<br />
  12. 12. Respiratory Control Dysfunction<br />Cheyne-stokes breathing<br />Biot’s breathing<br />Ondine’s curse<br />Sleep-Apnea syndromes<br />Obstructed apnea<br />Non-obstructed (central) apnea<br />
  13. 13. CLINICAL CASES<br />
  14. 14. Nitrogen NarcosisRaptures of the Depth! <br />At sea-level pressure, nitrogen has no significant effect on bodily function <br />But at high pressures (deep sea diving) – varying degrees of narcosis<br />Mild narcosis appear is about 120 feet (jovial, no-cares)<br />At 150- 200 feet, diver becomes drowsy<br />At 200 – 250 feet, strength wanes considerably, & diver often becomes too clumsy to perform the work required<br />Beyond 250 feet, the diver usually becomes almost useless<br />
  15. 15. Oxygen Toxicity <br />When Po2 in blood rises above 100 mm Hg <br />Amount of O2 dissolved in blood increases markedly<br />Delivery of O2 to tissues increases<br />Symptoms:<br />Nausea, muscle twitchings, dizziness, disturbances of vision, irritability, & disorientation<br />Brain seizures – coma<br />Oxygen free radical accumulationcauses toxicity (superoxides hydrogen peroxide)*<br />
  16. 16. Oxygen Toxicity <br />Acute <br />Exposure to very high Po2 for prolonged periods of time<br />Symptoms develop as mentioned<br />Chronic <br />Exposure to moderately high Po2 doesn’t lead to tissue symptoms<br />But lung passageway congestion, sore throat, substernal distress, pulmonary edema, and atelectasisbegin to develop*<br />In infants with RDS O2 therapy leads to <br />Chronic condition characterized by lungs cycts & densities (bronchopulmonary dysplasia) + retinopathy of prematurity (retrolentalfibroplasia)<br />
  17. 17. Hyperbaric O2 therapy<br />Intense oxidizing properties of high-pressure oxygen (hyperbaric oxygen) can have valuable therapeutic effects<br />Especially use in infectious conditions caused by organisms that thrive in anaerobic conditions<br />Gas gangrene (clostridial organisms)<br />Also useful in decompression sickness, arterial gas embolism, CO poisoning, osteomyelitis, and MI<br />
  18. 18. CO2 toxicity<br />At very high Pco2 – CO2 depresses respiratory centres<br />
  19. 19. Decompression Sickness<br />Nitrogen dissolves in body fluids<br />Nitrogen is not metabolized in body<br />Hence to remove it – one needs to exhale it!<br />In high pressure scenarios:<br />Alveolar PN2 is high – so is tissue PN2<br />High P in blood gases AND outside body maintains the dissolved state of N2 in tissues<br />Sudden drop in P may cause bubbles to form – escape of N2 from tissues* (decompression)<br />
  20. 20. Decompression Sickness<br />Symptoms are mostly due to bubble embolism<br />Pain in joints (‘bends’)<br />CNS symptoms:<br />Dizziness (5% cases)<br />Paralysis* or collapse and unconsciousness in 3% cases<br />Respiratory symptoms (‘chokes’)<br />caused by massive numbers of microbubbles plugging lungs capillaries; <br />Leading to serious shortness of breath, severe pulmonary edema & may be death<br />Prevention<br />Divers to ascend slowly<br />Tank Decompression<br />
  21. 21. Asthma<br />Disease of airway inflammation and airflow obstruction <br />Characterized presence of intermittent symptoms: <br />wheezing, <br />chest tightness, <br />shortness of breath (dyspnea), and <br />cough together with demonstrable bronchial hyperresponsiveness<br />Pathophysiology <br />Airway resistance increases due to<br />airway inflammation, <br />smooth muscle hyperresponsiveness, and <br />airway narrowing, <br />small-caliber peripheral airways are the site of increased resistance <br />This is worsened by the superimposed mucus hypersecretion and by any additional bronchoconstrictor stimuli<br />
  22. 22. Asthma Contd..<br />Pathophysiology<br />Airway obstruction occurs diffusely but not homogeneously<br />As a result, variability in V/Q mismatch occurs <br />Areas of low & high V/Q ratios exist <br />Low V/Q ratio regions - contributes to hypoxemia<br />Pure shunt is unusual in asthma <br />Arterial CO2 tension is usually normal to low (due to increased ventilation seen with asthma exacerbations)<br />Hypercapnia - late and ominous sign! <br />
  23. 23. Asthma – Symptoms & Signs<br />Cough<br /> wheezing<br />Dyspnea & Chest tightness<br />Tachypnea and tachycardia <br />Pulsus paradoxus<br />Hypoxemia <br />Hypercapnia and respiratory acidosis (severe asthma)<br />Obstructive defects by pulmonary function testing:<br />Normal between attacks (mild asthma)<br />During attacks: Decreased FEV1, FEV1/FVC, peak expiratory flow rates<br />Bronchial hyperresponsiveness <br />20% decrease in FEV1 in response to a provoking factor OR<br />20% increase in the FEV1 in response to an inhaled bronchodilating <br />
  24. 24. COPD<br />Chronic bronchitis <br />Productive cough for 3 months of the year for 2 consecutive years <br />Productive cough<br />Wheezing<br />Inspiratory and expiratory coarse crackles <br />Tachycardia<br />Imaging: increased lung volumes with relatively depressed diaphragms consistent with hyperinflation <br />Pulmonary function tests: FEV1, FVC, and the FEV1/FVC – all reduced <br />Blood gases: hypoxemia is common (abnormal V/Q)<br />Polycythemia present<br />
  25. 25. COPD<br />Emphysema <br />Abnormal permanent enlargement of the airspaces distal to the terminal bronchioles, accompanied by destruction of their walls<br />Decreased breath sounds<br />Tachycardia<br />Imaging: hyperinflation<br />Pulmonary function tests: all reduced<br />Blood gases: may be normal (but exercise induces decreased Po2)<br />Polycythemia present<br />
  26. 26.
  27. 27. Clinical Scenarios<br />Restrictive Lung Disease (Interstitial Lung Disease)<br />A category of extrapulmonary, pleural, or parenchymal respiratory diseases that:<br />Restrict lung expansion <br />Decreased lung volume<br />Increased work of breathing<br />Inadequate ventilation and/or oxygenation<br />Pulmonary function test demonstrates a decrease in the forced vital capacity<br />
  28. 28. Non-Respiratory Functions of Lungs<br />Immune<br />Acid base balance<br />Blood reservoir<br />Conversion of precursor molecules<br />
  29. 29. Respiratory Function Tests<br />Max. voluntary ventilation<br />Respiratory responses to CO2<br />Forced vital capacity<br />Diffusion capacity<br />FRC & VC<br />Blood gases<br />