2.5

• Mechanical ventilation


  Provide vent support resulting in satisfactory alveolar ventilation which is assessed by PaCO2 measurement
• Normal PaCO2 range


  35 - 45 mmHg
• Normal pH range


  7.35 - 7.45
• COPD patients


  • Exception to the goal of normalizing PaCO2 in the range of 35 to 45 mmHg
  • Tend to have a PaCO2 range between 50 - 60 mmHg
• Intentional hyperventilation


  Low PaCo2 levels produce cerebral vasoconstriction which reduces ICP
• Target PaCO2 range for intentional hyperventilation

  26- 30 mmHg
• Permissive hypercapnia


  Purposely delivering less VT to reduce alveolar pressures and minimize alveolar distention
• Patient undergoing permissive hypercapnia

  PaCO2 rises, pH falls resulting in respiratory acidosis
• Permissive hypercapnia


  • Should be avoided in patients with increased ICP levels, head trauma, cerebral edema, brain lesions, seizure disorders
• Desired rate formula


  Desired F= (initial PaCO2 * Initial F) / Desired PaCO2
• Desired VT formula


  Desired Vt= (Initial PaCO2 * initial VT) / Desired PaCO2
• Desired Ve formula


  Desired Ve= (Initial PaCO2 * initial Ve) / desired PaCO2
• Decreasing PaCO2 values for a patient on AC mode

  Increase RR, VT or inspiratory pressure
• Increasing PaCO2 values for a patient on AC mode

  Decrease RR, VT, or inspiratory pressure
• Factors affecting alveolar ventilation and PaCO2 values on SIMV mode

  • Mandatory RR, VT, Ins pressure, and PS (SPONT VT/F)
• Decreasing PaCO2 values for a patient on SIMV mode

  Increase RR, VT, Ins Pressure and PS
• Increasing PaCO2 values for a patient on SIMV mode

  Decrease RR, and Pressure support and increase VT, Ins Press
• Increasing Pressure Support parameter

  Increases VT
• Decreasing Pressure Support parameter

  Decreases VT