Oxygen Therapy


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Oxygen Therapy

  1. 1. Management of acute respiratory distress syndrome and oxygen therapy Dr. Purushottam Mittal Consultant Cardiologist
  2. 2. Acute Lung Injury and ARDS
  3. 3. The concept <ul><li>Osler:1927- Uncontrolled septicemia leading to pulmonary edema </li></ul><ul><li>Ashbaugh et al 1967- Non cardiogenic pulmonary edema in a number of diverse pathological conditions not directly involving lung </li></ul><ul><li>Pathogenesis remains unclear till today </li></ul><ul><li>Mortality: 30-60% at best centers </li></ul>
  4. 4. The definition <ul><li>Acute onset respiratory failure </li></ul><ul><li>Bilateral chest infiltrates on frontal X-Ray </li></ul><ul><li>Absence of elevated left heart filling pressures ( PCWP< 18 mmHg) </li></ul><ul><li>PaO2 / FIO2 < 300 - Aute Lung Injury < 200- Acute respiratory distress syndrome </li></ul>
  5. 5. Aetiology and mortality- Nontropical conditions Burns 75% Acute pulmonary infections 70% Severe sepsis 67% Aspiration pneumonia 61% Pancreatitis 56% Direct trauma 29% Poisoning 0% Extrathoracic injury 0%
  6. 6. Aetiology and mortality- Tropical conditions Rabies 100% Tetanus 74% Amoebiasis 40% Disseminated tuberculosis 38% Cerebral malaria 30% Organo phosphorus poisoning 10% Salmonella septicemia 0% Gram Negative septicemia - FP 0%
  7. 7. Oxygen uptake and utilization <ul><li>Changes occurring in pulmonary endothelium are reflection of a more generalized disorder affecting the entire microcirculation </li></ul><ul><li>Lung changes are earliest to manifest and aggravate the the damage to other organs </li></ul><ul><li>There is defect in peripheral tissue oxygen uptake and utilization </li></ul>
  8. 8. Cardiopulmonary Physiology <ul><li>Total lung capacity Decreases by 50% </li></ul><ul><li>There is early closure of small airways </li></ul><ul><li>Increase R-L Shunt , Increased V/Q mismatch </li></ul><ul><li>Pulmonary hypertension </li></ul><ul><li>Myocardial dysfunction due to circulating myocardial depressant factors </li></ul>
  9. 9. Clinical features <ul><li>Back ground of myocardial depressant factors </li></ul><ul><li>Worsening dyspnoea and restlessness </li></ul><ul><li>Worsening hypoxia despite supplemental oxygen </li></ul><ul><li>Scattered crackles and occasionally a wheeze </li></ul><ul><li>Early stages disproportionate tachypnea may be the only warning sign which should never be ignored </li></ul>
  10. 10. Complications <ul><li>Nosocomial pneumonia- Incidence-15% Factors-Increasing length Intra-abdominal sepsis Diagnosis-High index of suspicion Treatment-Empirical </li></ul><ul><li>Multiorgan dysfunction –GI-20-30% Renal: 30-40%, Cardiac-50-70%, Hep-50% </li></ul>
  11. 11. Diagnosis <ul><li>Chest X-Ray: Early- Interstitial pulmonary edema Late-full blown pulmonary edema Absence of cardiomegaly, Kerley lines and Vascular redistribution to upper lobes </li></ul><ul><li>Symmetrical lung involvement may not be present </li></ul>
  12. 12. X-Ray chest-ARDS
  13. 13. X-Ray chest-ARDS
  14. 14. Arterial blood gases <ul><li>Essential for the initial diagnosis and subsequent monitoring </li></ul><ul><li>Early stages- Hypoxia with hypocapnea </li></ul><ul><li>Late-hypoxia with hypercapnea </li></ul><ul><li>p H-Respiratory Alkalosis- Respiratory Acidosis-Metabolic Acidosis </li></ul><ul><li>Hypoxia refractory to supplemental oxygen therapy </li></ul>
  15. 15. Management <ul><li>Patient usually do not die of respiratory failure (only 16%) </li></ul><ul><li>Main cause of death is sepsis and MOF </li></ul><ul><li>Principles:Treat underlying condition Respiratory support Circulatory support Role of Corticosteroids Activated protein C </li></ul>
  16. 16. Respiratory support
  17. 17. Considerations in oxygen therapy <ul><li>Does the patient have a normally sensitive respiratory center and a normal control over respiration </li></ul>
  18. 18. Beneficial effects of oxygen therapy <ul><li>Improvement in cell function involving various organ systems </li></ul><ul><li>Decrease in the work of breathing </li></ul><ul><li>Decreased in the myocardial work </li></ul>
  19. 19. Hypoxemia-grading <ul><li>Mild- SpO2 < 97% ( PaO2-75mmHg) </li></ul><ul><li>Moderate- SpO2 < 90%( PaO2-60mmHg) </li></ul><ul><li>Severe- SpO2<75%( PaO2-60mmHg) A PaO2 of <20 mmHg for significant length of time produces brain death </li></ul>
  20. 20. Patients with normally sensitive respiratory center <ul><li>Can tolerate high concentration of oxygen at a flow rate of 6-8 liters per minute </li></ul><ul><li>No risk of CO2 retention </li></ul><ul><li>Conditions: Sever ILD Pneumonia Pulmonary edema Atelectesis Acute hypoventilation of any cause Acute severe asthma </li></ul>
  21. 21. Patients with abnormal control over respiratory center <ul><li>Respiratory center comparatively insensitive to increasing pCO2 and dependant hypoxic stimulus </li></ul><ul><li>High concentration of oxygen will improve O2 saturation but will will result in hypoventilation and dangerous rise in pCO2 </li></ul><ul><li>O2 therapy-Pink but obtunded, drowsy or even comatose patient </li></ul>
  22. 22. Conditions with abnormal respiratory drive <ul><li>Severe chronic obstructive pulmonary disease </li></ul><ul><li>Chronic hypoventilation syndromes </li></ul><ul><li>Some elderly patients with asthma </li></ul>
  23. 23. Oxygen therapy methods <ul><li>Routine oxygen therapy using low flow O2 delivery devices </li></ul><ul><li>Controlled O2 therapy </li></ul>
  24. 24. Routine O2 therapy <ul><li>Sufficient to relieve moderate hypoxia </li></ul><ul><li>Can achieve oxygen concentration (FIO2) of about 40% at a flow rate of 6-8 liters per minute </li></ul><ul><li>Patients usually do not tolerate high flow rates with these devices </li></ul>
  25. 25. Routine O2 therapy <ul><li>Nasal catheters and prongs </li></ul><ul><li>Face mask </li></ul><ul><li>Face mask with reservoir bags </li></ul><ul><li>Face mask with reservoir bags and directional valves </li></ul>
  26. 26. Nasal prongs
  27. 27. Nasal catheters and prongs <ul><li>O2 concentration is about 24% at flow rate of 1liter /minute </li></ul><ul><li>At 6-8 liter per minute O2 concentration is about 40% </li></ul><ul><li>Actual O2 delivered to lung also depends on tidal volume and minute ventilation </li></ul><ul><li>Precise regulation of therapy is not possible </li></ul>
  28. 28. Nasal catheters and prongs-use <ul><li>Nasal catheter-tip should be advanced to the fold of soft palate, too far advancement may cause abdominal distention </li></ul><ul><li>Catheter should be lubricated by xylocaine jelly </li></ul><ul><li>Catheter should be changed from one nostril to other every 4 hourly </li></ul>
  29. 29. Face Mask
  30. 30. Face Mask <ul><li>Mask forms a small O2 reservoir at nasal opening </li></ul><ul><li>the Inspired O2 concentration depends on the size of mask and flow rate of oxygen </li></ul><ul><li>Higher flow rates up to 10 liter / minute can be tolerated ( SpO2 – 55%) </li></ul>
  31. 31. Face mask with reservoir bags
  32. 32. Face mask with reservoir bags <ul><li>Reservoir bag increases the potential reservoir of oxygen and , allows a further increase in ventilation </li></ul><ul><li>Sufficiently high flow rates should be maintained (8-12 liter/minute) </li></ul><ul><li>Can increase the FIO2 to 50-80% </li></ul><ul><li>Directional valve: FIO2-90-95% </li></ul>
  33. 33. Controlled O2 therapy <ul><li>Necessary in all patients who show a hypercapnic response to unlimited or uncontrolled oxygen administration </li></ul><ul><li>In severely hypoxic patients even a small rise in PaO2 will produce a significant greater rise in the oxygen saturation of arterial blood </li></ul>
  34. 34. Controlled O2 therapy <ul><li>It is best to start with an inspired oxygen concentration of 24% and watch for rise in PCo2 </li></ul><ul><li>If increase in PCO2 is less than 10mmHg than increase FIO2 to 28-30% </li></ul><ul><li>Maximal permissible limit of rise in PCO2 is 20mmHg and p H < 7.25 </li></ul>
  35. 35. Mechanical Respiratory support-Indications <ul><li>Refractory hypoxemia unresponsive to supplemental oxygen </li></ul><ul><li>Excessive work of breathing: RR>35/ mt Minute ventilation> 12 liter/minute </li></ul><ul><li>Hemodynamic instability </li></ul><ul><li>Inability to protect airway </li></ul><ul><li>Anticipated rapid clinical deterioration </li></ul>
  36. 36. Non- invasive ventilator support <ul><li>Effective in a very small subset of minor Acute lung Injury </li></ul><ul><li>C-PAP: Levels: 10-12 Cm H2O Very high Flow rate:>70 liter/ minute </li></ul><ul><li>Bi- PAP: I-PAP-15cm H2O E-PAP-7-10cm H2O </li></ul><ul><li>Aim –SpO2_ >90% </li></ul>
  37. 37. Invasive ventilation <ul><li>fundamental concepts: Low tidal volume PEEP to prevent collapse of alveoli Avoidance of O2 toxicity Prevention of hemodynamic instability </li></ul>
  38. 38. Initial ventilator settings Parameter Setting Tidal Volume 7 ml/Kg Respiratory Rate 15-18 Minute Ventilation 8.5 liter /mt I/ E Ratio 1:2-1:3 PIP 30 cm H2O PEEP 10 cm H2O FIO2 100%
  39. 39. Newer concepts in ventilation <ul><li>Inverse ratio ventilation- I time is > E time I:E Ratio1:1or 1.5:1 Improved oxygenation Less barotraumas Reduction in sheer stresses </li></ul><ul><li>Use of prone position:Improved oxygenation </li></ul><ul><li>Permissive hypercapnea: low tidal volume PaCO2 up to 70-80 mm Hg well tolerated </li></ul><ul><li>Open lung concept: Effective in experienced hands </li></ul>
  40. 40. Circulatory support <ul><li>Hemoglobin-11gm/dl </li></ul><ul><li>Hematocrite-33-36% </li></ul><ul><li>IV Inotropes to BP >90 mmHg </li></ul><ul><li>PCWP not >12mmHg </li></ul><ul><li>Pulmonary artery catheter ? </li></ul>
  41. 41. Corticosteroids <ul><li>DO not prevent ARDS </li></ul><ul><li>Do not alter outcome when given early in natural history </li></ul><ul><li>IV methyl prednisolone 40 mg 6 hourly in the late stages of ARDS can improve recovery and survival (effective in fibroproloferative phase) Should be used only if there is no E/O infection especially pneumonia </li></ul>
  42. 42. Activated protein C <ul><li>May be effective in cases of infective etiology </li></ul><ul><li>Conflicting reports </li></ul><ul><li>Very costly </li></ul>
  43. 43. Summary-ARDS <ul><li>A condition with varied etiology and uncertain pathogenesis </li></ul><ul><li>May need prolonged ventilator support </li></ul><ul><li>High but improving mortality </li></ul>