Hypoxemia

 

 

Differential Diagnosis

 

  • Low FiO2:

    • Oxygen failure or pipeline crossover of gases

  • Hypoventilation:

    • Low TV or RR

    • Ventilator dyssynchrony

    • Circuit leak

    • Obstructed ETT

  • V/Q mismatch or shunt:

    • Airway:

      • ​Bronchospasm

      • Mainstem intubation

      • Mucous plug

    • Alveolar:

      • ​Pulmonary edema

      • Aspiration

      • Atelectasis

    • Pleura:

      • ​Pneumothorax

      • Pleural effusion

  • Deadspace:

    • Pulmonary embolism 

    • Low cardiac output state

  • metabolic O2 demand:

    • Malignant hyperthermia, thyrotoxicosis, sepsis, hyperthermia, neuroleptic malignant syndrome

  • Diffusion abnormality:

    • Chronic lung disease

  • Artifacts:

    • Confirm by ABG

    • Poor waveform (probe malposition, cold extremity, light interference, cautery)

    • Dyes (methylene blue, indigo carmine, blue nail polish)

 

 

Management

 

  •  FiO2 to 100%, high flow

  • Check gas analyzer to rule out low FiO2 or high N2O

  • Check other vitals, cycle NIBP, check peak inspiratory pressure, feel for pulse

  • Check ETCO2 (?extubated/disconnected/low BP)

  • Hand ventilate (check compliance, rule out leaks & machine factors)

  • Listen for breath sounds 

  • Check position of ETT

  • Soft suction via ETT (to clear secretions & check for obstructions)

  • Consider code cart if severe

  • Depending on likely diagnosis, consider:

    • Large recruitment breaths, consider PEEP

    • Bronchodilators

    • Additional neuromuscular blockade

    • ↑ FRC (head up, desufflate abdomen)

    • Fiberoptic scope to rule out mainstem intubation or ETT obstruction

    • ABG, CXR

    • Consider terminating surgery for refractory hypoxemia

    • Plan for post-op care