Post-intubation hypoxia

Reviewed and revised 26 September 2015

Overview

Post-intubation hypoxia can be rapidly fatal without early intervention, which requires a structured approach to concurrently identifying and treating the underlying cause

Causes

The immediate life threats can be summarized as “DOPES”:

• Displacement of the endotracheal tube (ETT)
• Obstruction of the ETT
• Patient — especially pneumothorax; also: pulmonary embolism, pulmonary edema, collapse, bronchospasm
• Equipment — ventilator problems
• ‘Stacked breaths’ — a reminder about bronchospasm and ventilator settings.

Structured approach

1. Disconnect the ventilator and administer high-flow 100% oxygen (FiO2 1.0) using a bag-valve-mask.
   • Disconnection allows the release of trapped gas in the patient with severe bronchospasm — these patients usually have evidence of bronchospasm and/ or hypotension in addition to hypoxia.
   • Also, if the patient is easy to ventilate and re-oxygenate, then the problem probably lies with the ventilator or the circuit.
   • In a ventilated patient that has a problem always think: man versus machine.
2. Assess the patient using the MASH approach before attempting to diagnose the problem:
   • Movement of the chest during ventilation —
     is it absent or is movement only on one side? Is the chest hyper-expanded?
   • Arterial saturation (SaO2) and PaO2 —
     obtain an ABG sample
   • Skin colour of the patient (is he turning blue or pinking up?) —
     the SO2 monitor lags behind the true oxygen saturation of the patient.
   • Hemodynamic stability
3. If the patient is difficult to manually ventilate, determine if the problem lies with the endotracheal tube or with the patient.
4. If there is little chest movement, a patient problem is still possible, but a problem with the ETT needs to be be ruled out urgently:
   • check ETCO2 to ensure the ETT is not in the esophagus and is patent.
   • pass a suction catheter and/ or a bougie to ensure the ETT is not obstructed.
   • check the placement of the tube visually — preferably by bronchoscopy, or alternative by by laryngoscopy from the top end (although this is far from 100% reliable).
   • consider a CXR to check ETT position if hypoxemia is not critical, especially if endobronchial intubation is suspected
   • If in doubt, and the hypoxia has not been rapidly resolved, take the tube out… and replace it.
5. If there is reasonable chest movement, a patient problem is most likely. Perform a focused exam and urgently seek and treat the following life-threats:
   • pneumothorax (look for asymmetrical chest movement)
   • lung collapse (look for asymmetrical chest movement)
   • pulmonary edema
   • bronchospasm (chest wall movement may be minimal — look for hyper-expansion)
   • pulmonary embolus
6. If the bag is easy to compress during manual ventilation, but there is little or no chest movement suspect either:
   • a circuit leak (e.g. cuff leak, disconnection, or a hole in the circuit), OR
   • dislodgement of the endotracheal tube — you may be ventilating the oropharynx or the stomach
7. If the patient is easy to ventilate with the bag and the hypoxemia rapidly resolves
   • Find out what happened just before the desaturation:
     • had suctioning been performed? (in some settings the loss of PEEP during disconnection of the circuit may lead to derecruitment and atelectasis, result in desaturation)
     • had there been a disconnection of the ventilator/circuit?
   • Otherwise, there may be a problem with the ventilator settings or there was an equipment failure.
     • check ventilator settings
     • trouble-shoot equipment failure

Acute Respiratory distress syndrome (ARDS)

ARDS patients are typically ventilated with a protective lung ventilation strategy +/- an open lung approach. In cases of refractory hypoxaemia there are numerous strategies for improving oxygenation in ARDS. These topics are covered in other sections of the CCC:

• CCC — Protective lung ventilation
• CCC — Open lung approach to ventilation
• CCC — Improving oxygenation in ARDS

References and Links

LITFL

• Pulmonary Puzzle 012 — Man versus Machine
• CCC — Lung recruitment manoevres

FOAM and web resources

• ICU Web — Trouble-shooting mechanical ventilation; Asthma
• EMCrit — Podcast 16 – Coding Asthmatic, DOPES, & Finger Thoracostomy
• EMCrit — Origins of the DOPES mnemonic (2011)