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Monitoring and Management of Ventilatory Support

Monitoring and Management of Ventilatory Support. Educational Objectives. List the reasons for monitoring the patient receiving ventilatory support List and describe the methods of evaluating patient oxygenation List and describe the methods of evaluating patient ventilation

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Monitoring and Management of Ventilatory Support

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  1. Monitoring and Management of Ventilatory Support

  2. Educational Objectives • List the reasons for monitoring the patient receiving ventilatory support • List and describe the methods of evaluating patient oxygenation • List and describe the methods of evaluating patient ventilation • List and describe the ventilator parameters monitored • List the normal hemodynamic values • Describe the effects that mechanical ventilation may have upon the hemodynamic parameters

  3. Reasons for Monitoring the Patient • Establish baseline measurements • Allow trending to be observed in order to document progress or lack of progress • Determine efficacy of treatment in order to modify as needed • Determine limits of alarm parameters

  4. Evaluation of Oxygenation – is There a Problem? • Physical Findings • Heart rate • Respiratory rate • Work of breathing • Use of accessory muscles • Retractions

  5. Evaluation of Oxygenation – is There a Problem? • Physical Findings • Cyanosis • Peripheral • Central or circumoral (surrounding the mouth) • Level of consciousness/mental status • Confusion • Drowsiness • Anxiety

  6. Evaluation of Oxygenation – is There a Problem? • Laboratory Findings • Arterial blood gases • PaO2 • SaO2(measured or calculated?) • Hemoglobin (Hb)/Hematocrit (Hct) • Total oxygen content (CaO2) • Level of consciousness/mental status • Confusion • Drowsiness • Anxiety • Pulse oximetry • Lactic acid levels

  7. Determine Cause of Hypoxemia • CO-Oximetry Results • Oxyhemoglobin (HbO2) • Carboxyhemoglobin (HbCO) • Methemoglobin (MetHb) • Hemoglobin (Hb)/Hematocrit (Hct)

  8. Determine Cause of Hypoxemia • Laboratory Findings • Oxygen consumption (O2) • Normal value – 250 mL/min • Determined by Fick Equation Where is cardiac output, CaO2 and are arterial and mixed venous O2content • Increase in oxygen consumption necessitates increase in oxygen delivered

  9. Determine Cause of Hypoxemia • Alveolar-arterial Gradient [P(A-a)O2] • Normal value – 5 to 15 mm Hg while breathing room air; increases to 100 to 150 mm Hg while breathing 100% oxygen • Determined by subtracting arterial value from arterial blood gas result from alveolar value using alveolar air equation

  10. Determine Cause of Hypoxemia • Arterial to Alveolar Oxygen Ratio (PaO2/FIO2) • Normal Value – 400 to 500 mm Hg while breathing room air • Used to define acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) • PaO2/FIO2 < 300 mm Hg in ALI • PaO2/FIO2 < 200 mm Hg in ARDS

  11. Determine Cause of Hypoxemia • Radiologic Findings • Consolidation • Fluid • Free air

  12. Management Options – FIO2 • If FIO2 < 0.6, increase oxygen concentration; if no PEEP is employed, may add 5 cmH2O of PEEP first • If FIO2 > 0.6, consider reducing as soon as patient’s condition permits to avoid complications

  13. Management Options – FIO2 • Titration of Oxygen Level • If the patient’s oxygenation status is unknown or critical, always start ventilatory support with an FIO2of 1.0 • General goal – maintain PaO2between 60 and 80 mmHg or SpO2greater than 90% • Determination of desired PaO2 Desired PaO2= Desired FIO2 x Actual PaO2 FIO2 (Actual)

  14. Management Options – FIO2 • General guideline for reduction of FIO2 • Decrease in increments of 5 to 10% • Follow each reduction by drawing arterial blood gases or oximetry; allow at least fifteen minutes after the change for equilibration of blood

  15. Management Options – PEEP Positive End Expiratory Pressure (PEEP) Maintenance of baseline pressure above atmospheric level • Minimum PEEP • Least amount of PEEP necessary to achieve and maintain a PaO2 of at least 60 mmHg

  16. Management Options – PEEP • Optimal PEEP • The level of PEEP at which oxygen delivery is maximized while minimizing hemodynamic side effects • Generally only employed on patients requiring > 10 cm H2O

  17. Management Options – PEEP • Method for Determination of Optimal PEEP • Determine baseline values of blood pressure, mixed venous oxygen level, arteriovenous oxygen content difference, PaO2, static compliance, and cardiac output • Increase level of PEEP in increments of 2 cmH2O, measuring values at each increment • When a decline in oxygen delivery is observed, the optimal PEEP has been exceeded • Return PEEP level to previous increment

  18. Management Options – PEEP • General Guidelines for Reduction of PEEP • Decrease in increments of 2 cm H2O • Follow each reduction by drawing blood gases or oximetry; allow at least fifteen minutes after the change for equilibration of blood • Reduction of PEEP to zero prior to extubation may be neither necessary nor advantageous

  19. Management Options – Tidal Volume • Increasing Tidal Volume (VT) may be used for recruitment of alveoli if hypoventilation contributes to hypoxemia Normal Value – 6 to 12 mL/kg IBW

  20. Management Options – Inspiratory Time • Prolongation of inspiratory time to a point where inspiratory time exceeds expiratory time Normal I:E ratio – 1:1.5 to 1:2

  21. Management Options – Inspiratory Time • Principle of Use • Increase in inspiratory time (TI) causes increase in • Increase in aids in maintaining integrity of alveoli and recruiting atelectatic alveoli • Associated with improvement in • Associated with improvement of PaO2 in patients with ARDS

  22. Management Options – Bronchial Hygiene • Postural drainage • Percussion • Adequate humidification • Ambulation, sitting up, turning patient

  23. Management Options – Patient Positioning • Ambulation, sitting up helpful in improving oxygenation • Turning patient from side to side aids in bronchial hygiene

  24. Management Options – Patient Positioning • Prone Positioning • May result in dramatic improvement in oxygenation in patients with ARDS and ALI • Care must be taken to ensure tubes and lines are not displaced during turning • May improve and reduce shunting by removing pressure of the heart on the dorsal regions

  25. Evaluation of Ventilation – Physical Findings • Breathing Patterns • Apnea • Tachypnea • Bradypnea • Abnormal breathing patterns • Work of Breathing • Use of accessory muscles • Retractions

  26. Evaluation of Ventilation – Physical Findings • Heart Rhythms • Abnormal rhythms • Tachycardia • Bradycardia • Chest excursion • Altered Mental State • Anxiety • Confusion • Combativeness • Somnolence

  27. Evaluation of Ventilation – Diagnostic Findings • Arterial Blood Gases • Increased PaCO2 • Decreased pH • Decreased PaCO2 • Bedside Spirometry Results • Negative inspiratory force (NIF) – < -20 cmH2O • Spontaneous tidal volume – < 5 mL/kg IBW • Vital capacity – < 10 mL/kg IBW

  28. Evaluation of Ventilation – Determine Cause of Problem • Hypoventilation • Inadequate alveolar ventilation – A = (VT – VDS) (f) • Increase in physiologic dead space – VD/VT= (PaCO2 – PECO2)/PaCO2

  29. Evaluation of Ventilation – Determine Cause of Problem • Increase in Carbon Dioxide Production • Stress • Shivering • Pain • Asynchrony with ventilator • High carbohydrate diet

  30. Evaluation of Ventilation – Determine Cause of Problem Change in Lung and Chest Mechanics • Compliance – C = ∆V/∆P • ∆V = VT Corrected for Tubing Compliance • ∆P = Pplat – PEEP • Causes of decreased lung compliance • Atelectasis • Pulmonary edema • ALI/ARDS • Pneumothorax • Fibrosis

  31. Evaluation of Ventilation – Determine Cause of Problem • Causes of decreased thoracic compliance • Obesity • Pleural effusion • Ascites • Chest wall deformity • Pregnancy

  32. Evaluation of Ventilation – Determine Cause of Problem • Cause of increased lung compliance • COPD

  33. Evaluation of Ventilation – Determine Cause of Problem • Causes of increased thoracic compliance • Flail chest • Loss of chest wall integrity • Change in patient position

  34. Evaluation of Ventilation – Determine Cause of Problem • Change in Lung and Chest Mechanics • Airway Resistance – RAW = ∆P/∆ • ∆P = (Ppeak – Pplat) • ∆ = flow

  35. Evaluation of Ventilation – Determine Cause of Problem • Causes of increased resistance • Bronchospasm • Mucosal edema • Secretions • Excessively high rate of gas flow • Small endotracheal tube • Obstruction of endotracheal tube • Obstruction of the airway

  36. Evaluation of Ventilation – Determine Cause of Problem • Causes of decreased resistance • Bronchodilator administration • Decrease in flow of gas • Administration of bronchial hygiene

  37. Evaluation of Ventilation – Determine Cause of Problem • Loss of Muscle Strength/Neurological Input • Rapid Shallow Breathing Index (RSBI) • Indication of whether patients have the ability to breathe without ventilatory support

  38. Evaluation of Ventilation – Determine Cause of Problem • Loss of Muscle Strength/Neurological Input • Rapid Shallow Breathing Index (RSBI) • f/VT • If < 100 breaths/min/L, patient has ability to breathe without ventilator • If > 100 breaths/min/L, patient will likely not be able to sustain spontaneous breathing • Maximal inspiratory pressure • Maximum voluntary ventilation

  39. Evaluation of Ventilation – Management Options • Increase Alveolar Ventilation • Increase in Mechanical Tidal Volume • Normal Volume – 6 to 12 mL/kg IBW • Most direct way to change alveolar ventilation • Should normally not exceed 12 to 15 mL/kg IBW • Associated with increase in peak inspiratory pressure which has increased risk of trauma to lung

  40. Evaluation of Ventilation – Management Options • Increase in spontaneous ventilation • More advantageous to patient than increasing mechanical tidal volume • Augmentation by pressure support mode helps overcome resistance of ventilator circuit and artificial airway

  41. Evaluation of Ventilation – Management Options • Increase Alveolar Ventilation • Increase in Mechanical Rate • Normal Value – 12 to 18 Breaths per Minute • Should Normally not Exceed 20 Breaths per Minute • Prediction of Desired Rate New rate =

  42. Evaluation of Ventilation – Management Options • Decrease Carbon Dioxide Output (Production) • Medicate patient to relieve pain, stress, and prevent asynchrony, decreasing work of breathing • Maintain patient’s temperature within normal range • Provide appropriate nutrition

  43. Evaluation of Ventilation – Management Options • Treat Underlying Pulmonary Pathophysiology • Maintain airway in patent state • Prevent accumulation of secretions in airway • Use properly sized artificial airway • Prevent occlusion of airway by patient; use bite block

  44. Considerations in Management – Permissive Hypercapnea • Allowing PaCO2level to remain elevated above 45 mmHg • Purpose • Maintain plateau pressure at an acceptable level (< 30 cm H2O) by decreasing tidal volume to less than 6 mL/kg and increasing respiratory rate, thereby minimizing trauma and cardiovascular side effects

  45. Considerations in Management – Permissive Hypercapnea • Method • Decrease tidal volume and increase respiratory rate, while maintaining minute volume • If PaCO2increases and pH decreases, either permit normal metabolic compensation or administer medications to maintain level at 7.25 to 7.35 • Institute gradually to allow PaCO2 to increase gradually over hours or days

  46. Considerations in Management – Permissive Hypercapnea • Relative Contraindications or Cautions • Presence of cardiac ischemia • Presence of pulmonary hypertension • Compromised left ventricular function • Right heart failure • Head trauma • Intracranial disease • Metabolic acidosis

  47. Considerations in Management – Permissive Hypercapnea • Absolute Contraindication • Intracranial lesions

  48. Considerations in Management – Creation of Intrinsic PEEP • Intrinsic PEEP • Alveolar pressure above the applied PEEP at the end of exhalation

  49. Considerations in Management – Creation of Intrinsic PEEP • Contributing factors • Pressure support ventilation • Airway obstruction • Rapid respiratory rate • Insufficient flow rate • Relatively equal I:E ratio • High minute volume • History of air trapping

  50. Considerations in Management – Creation of Intrinsic PEEP • Problems associated with intrinsic PEEP • Increase in work of breathing – patient must overcome PEEP in order to trigger breaths • Underestimation of mean airway pressure • Increase in hemodynamic side effects • Increase in volutrauma

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