Oxygenation Failure and Oxygen Therapy–Nursing Management and Role

Oxygenation  mask

Respiratory Failure

• Occurs because of inadequate gas exchange

• Type I = oxygenation failure

  • Blood bypasses or is not fully oxygenated in the lungs causing hypoxemia
  • PaCO2 is normal or low because ventilation is unchanged or increased due to breathlessness
  • Causes: V/Q mismatch, right → left shunt, low inspired oxygen
  • Oxygenation is improved by re-expanding collapsed alveoli, oxygen therapy, and reduction of V/Q mismatch

 

• Type II = ventilatory failure

  • Hypoventilation reduces CO2 clearance causing hypercapnia with or without hypoxemia
  • Causes: respiratory muscle weakness, chest wall deformity (kyphoscoliosis), impaired respiratory drive, excessive WOB
  • Ventilation is improved and WOB decreased by decreasing airway resistance, ventilatory support, and increasing compliance

 

Tissue Hypoxia

• Tissue hypoxia occurs within 4 minutes of cardiorespiratory arrest because oxygen reserves are small

• Causes of tissue hypoxia

– Hypoxemia

– Failure of oxygen transport

  • Decreased CO/perfusion
  • Anemia
  • hemoglobinopathy

– Failure of tissue oxygen utilization

  • Sepsis
  • Poisoning (cyanide)

 

Nursing Management

Monitoring Oxygenation

• Arterial saturation

  • Saturation of Hb is determined by partial pressure of oxygen in the plasma (PO2)
  • Pulse oximetry and ABG analysis measure SpO2, SaO2, and PaO2
  • These can be normal with tissue hypoxia if it’s caused by failure of oxygen transport or utilization…in these cases, mixed venous sat is a better indicator of tissue oxygenation

• PaO2/FiO2 ratio is a good index of gas exchange that adjusts for FiO2 changes

• PA-aO2 determines efficiency of gas exchange

• Detection of single-organ ischemia is difficult

 

Acute Oxygen Therapy

• Indications for instituting oxygen:

  • Cardiorespiratory arrest
  • Hypoxemia
  • Hypotension
  • Low cardiac output
  • Metabolic acidosis
  • Respiratory distress

 

Oxygen Dosage

• Inadequate O2 therapy causes more deaths and disability than can be justified by the risks of oxygen

• The risk of hypoxia is usually greater than the risk of hypercapnia → don’t withhold oxygen for that reason!!

• Use whatever it takes to get the SaO2 to 90-93%…if the person has COPD, a venturi mask is a better option so the FiO2 can be controlled

 

Efficacy of Oxygen Therapy

• Hypoxemic patients

– Get the most benefit from O2 therapy

– A true shunt causes persistent hypoxemia despite increases in FiO2…improved oxygenation requires reduction of the shunt condition

– In alveolar hypoventilation, O2 therapy relieves the hypoxemia but not the hypercarbia

 

• Patient’s without hypoxemia

– In low CO states, high FiO2 only marginally improves oxygenation because Hb is fully saturated and O2 solubility is low

– These patients require restoration of blood flow

– In CO poisoning, high dose O2 is essential despite a normal PaO2 to reduce the CO half-life

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