2.1

• Adequate Tissue Oxygenation

  Requires adequate arterial oxygen content, sufficient cardiac output, and peripheral tissue perfusion
• Factors that determine Tissue Oxygenation

  • FiO2
  • Alveolar ventilation
  • V/Q relationships
  • Diffusion across the alveolar capillary membrane
  • Arterial oxygen content
  • Cardiac output
  • Peripheral perfusion
• Parameters that can be adjusted on the ventilator to alter a patient's arterial oxygenation level

  FiO2 and PEEP
• FiO2


  The concentration of oxygen found in the inspired gas
• The FiO2 you should provide to a patient when initiating a ventilator is 100%
• Oxygen toxicity complications


  • Absorption of atelectasis
  • Cellular injury
  • Airway injury
  • Parenchymal injury
  • Accentuation of hypercapnia
  • Retinopathy of prematurity
• Premature infants begin to experience retinopathy of prematurity at PaO2 levels greater than 80 mmHg
• Appropriate clinical oxygenation goals for most ventilator patients

  FiO2 < 0.50, PaO2 60-80 mmHg, SaO2 90-95%
• Factors that may cause SpO2 not to reflect SaO2 levels

  • Abnormal hemoglobin: Carboxyhemoglobin, methemoglobin, sulfhemoglobin, high glycohemoglobin A1c in diabetes
• Required (Desired) FiO2 equation

  Required FiO2 = (Initial FiO2 / initial PaO2) * Desired PaO2
• PEEP

  Helps restore or maintain lung volume and prevents or treats atelectasis
• PEEP


  • Helps prevent end alveolar collapse and may reduce the incidence of VAP and VALI
• Dangers of PEEP

  • Pulmonary barotrauma or VALI
  • Use cautiously in pts with hypotension or hypovolemia
  • Use in pts with elevated ICP (do not give more than 10 PEEP)
  • PEEP may increase Pplat and care must be used to maintain Pplat less than 30 cmH2O
• The absolute contraindication of using PEEP is untreated tension pneumothorax
• Arterial Oxygen Content


  Total number of oxygen molecules that is in arterial blood that is bound to hemoglobin and the amount that is dissolved in plasma
• Symbol for Oxygen Content

  CaO2
• Factors that Arterial Oxygen Content is dependent on

  • Arterial Oxygen Tension (PaO2)
  • Arterial Oxygen Saturation (SaO2)
  • Hemoglobin level (Hb)
• Formula for Arterial Oxygen Content

  CaO2=1.34 x SaO2 x Hb + .003 x PaO2
• The normal CaO2 value when breathing room air is 16-20
• Tissue Oxygen Delivery


  Rate of oxygen transport to the peripheral tissues determined by the cardiac output and arterial oxygen content
• Symbol for Tissue Oxygen Delivery


  DO2
• Factors that Tissue Oxygen Delivery is dependent on

  • Cardiac output
  • Arterial oxygen content
• Formula for Tissue Oxygen Delivery

  DO2 = CaO2 x T
• Cardiac Output


  The volume of blood ejected from the heart's ventricles, equal to the stroke volume multiplied by the heart rate
• Symbol for Cardiac Output

  T
• Formula for Cardiac Output

  QT= SV x HR
• The normal cardiac output value when breathing room air is 4-8 L/min
• Normal hemoglobin levels


  • Women: 12 to 15
  • Men: 13.5 to 16.5
• Clinical goal for hemoglobin

  Greater than or equal to 8