4.1-Mechanical-Ventilation-Part-I.ppt
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This document discusses ventilatory care of critically ill patients and weaning from mechanical ventilation. It covers the goals, indications, criteria for initiating mechanical ventilation and the various effects it can have on organ systems like the cardiovascular, respiratory, renal and central nervous systems. Modes of mechanical ventilation and ventilatory care bundles are also mentioned. The focus is on optimizing a patient's ventilation while on a ventilator and the process of gradually weaning them off when possible.
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4.1-Mechanical-Ventilation-Part-I.ppt
- 1. Dr Priyanka Ventilatory Care of Critically ill Patient and Weaning from Mechanical Ventilation University College of Medical Sciences & GTB Hospital, Delhi
- 2. Contents Introduction Goals of mechanical ventilation Indications of mechanical ventilation Criteria for initiating mechanical ventilation Effects of mechanical ventilation Modes of mechanical ventilation Ventilatory care bundles Weaning from mechanical
- 3. Mechanical ventilation Cornerstone of intensive care medicine “Ventilate” is derived from the Latin word “Ventus” meaning “Wind” Ventilation is the movement of air
- 4. Mechanical ventilation Use of a machine to take over active breathing for a patient Used for patients who are unable to sustain the level of ventilation necessary to maintain the gas exchange functions - oxygenation and carbon dioxide elimination
- 5. Goals of mechanical ventilation Increase efficiency of breathing Increase oxygenation Improve ventilation/perfusion relationship Decrease work of breathing
- 6. Indications of Mechanical Ventilation A. Established acute respiratory failure B. Incipient respiratory failure C. Low output states
- 7. Indications …. A) Established Acute Respiratory Failure Primary ventilatory failure Poisonings which depress the CNS CNS and neuromuscular disorders ( poliomyelitis, infective polyneuritis, myasthenia) Snake bites Severe tetanus
- 8. Indications… Acute pulmonary disorders e.g. fulminant pneumonia, acute lung injury (ARDS) Fulminant pulmonary oedema Major or massive pulmonary embolism Major or massive atelectasis Patients with COPD in acute crisis, unresponsive to conventional
- 9. Indications… B) Incipient Respiratory Failure Obese patients who have undergone upper abdominal surgery, or poor risk surgical patients Respiratory muscle fatigue in critical illnesses Patients with excessive ventilatory demands
- 10. Indications… C) Low output states Shock of any etiology D) Purposeful hyperventilation To decrease intracranial tension in patients with head injury To reduce cerebral edema after CPR or massive CVA
- 11. Criteria for initiating ventilatory support in adults On the basis of pulmonary function On the basis of blood gas analysis
- 12. Criteria…. A) On the basis of pulmonary function Respiratory rate > 35/ min VC<10 -15mL/kg MV> 10-12L /min Maximum Inspiratory Force < -20 cm H2O Vd/Vt ratio > 0.6
- 13. Criteria for initiating ventilatory support in adults On the basis of blood gas analysis PaO2 < 50 mmHg on room air PaO2 < 60 mmHg on O2 support ( fiO2 > 0.5) PaCO2 > 50 mmHg pH < 7.25 PaO2/fiO2< 250 P(A-a) O2>350 mmHg on fiO2 of 1
- 14. Criteria for initiating ventilatory support in adults On the basis of clinical parameters Visible excessive work of breathing in critically ill or debilitated patients Clinical evidence of respiratory muscle fatigue Poor chest excursions Tachypnea Respiratory muscle paradox
- 15. Effects of Mechanical Ventilation Cardiovascular Respiratory Renal Hepatic Gastrointestinal Central nervous system
- 16. Spontaneous breathing Contraction of the diaphragm and respiratory muscles Air flows into lungs Lowers the pleural, alveolar and airway pressures below atmospheric pressure
- 18. Positive pessure ventilation Gas flows into the lungs under a positive pressure gradient generated by the ventilator Increases the pleural, alveolar and airway pressures above atmospheric pressure Tidal volume delivered to lungs is directly related to the positive pressure when a pressure limited ventilator is used . In volume limited ventilators, the level of positive pressure is dependent on the mechanical tidal volume and on lung compliance and airway resistance
- 19. Effects of Mechanical Ventilation Cardiovascular Respiratory Renal Hepatic Abdominal Gastrointestinal Central nervous system
- 20. Cardiovascular system Decreased Preload Positive alveolar pressure ↑ lung volume compression of the heart by the inflated lungs the intramural pressure of the heart cavities rises (e.g., ↑ RAP ) venous return decreases preload is reduced stroke volume decreases cardiac output and blood pressure may drop Fall in cardiac output is generally
- 21. Cardiovascular Effects of PPV Spontaneous ventilation PPV
- 22. Cardiovascular system Reduced Afterload Positive intrathoracic pressure compression of heart facilitates ventricular emptying during systole Increases stroke
- 23. Blood pressure changes during mechanical ventilation
- 24. Cardiovascular system Degree of circulatory tolerance is dependent on • inspiratory inflation pressures • time duration of lung inflation • integrity of vascular reflexes • circulatory blood volume
- 25. Effects of PPV on hemodynamic measurements Increase in intrathoracic pressure Decrease in pulmonary blood volume and increase in systemic blood volume Decrease in venous return (CVP) Decrease in right ventricular stroke volume Decrease in pulmonary
- 26. Respiratory system Excessive airway pressure and tidal volume Ventilator induced lung injury Alteration in V/Q ratio
- 27. Ventilator associated lung injury
- 28. Neurologic Changes during Mechanical Ventilation Decrease cerebral blood flow Increase CSF pressure Decrease CSF absorption Increase CSF volume
- 29. systems
- 33. Cardiovascular considerations Positive pressure ventilation Increase in intrathoracic pressure Compression of pulmonary vessels Reduction in stroke volume
- 34. Cardiovascular considerations Reduction of cardiac output and pulmonary blood volume High V/Q mismatch Hypoxemia Decrease in o2 content Decrease in o2 delivery
- 35. Dead space Anatomic Dead space - conducting airways Estimated to be about 1ml per pound of ideal body weight Alveolar Dead space - normal lung volume that has become unable to take part in gas exchange because of reduction in pulmonary blood flow Pulmonary embolism Physiologic Dead space Sum of anatomic and alveolar dead space volumes
- 36. Effects of PEEP on hemodynamic measurements Increase in pulmonary artery pressures(PAP) Increase in central venous pressure (CVP) Decrease in aortic pressure Decrease in cardiac output
- 38. Neurologic Changes during mechannical ventilation Respiratory alkalosis decreased cerebral blood flow (<24hrs) reduced intracranial tension Respiratory alkalosis leftward shift of HbO2 (>24hrs) dissociation curve affinity for hemoglobin O2 release to tissues cerebral tissue hypoxia neurologic dysfunction hypophophatemia
- 39. Treatment in ICU --a frightening experience !!! Changing surgical dressings Catheterisation Insertion of a chest drain Turning the patient Continuous background of noise and activity Disturbed normal diurinal sleep rhythm and sleep deprivation