Respiratory Failure

Type 1

Characterised by a low pO2 with a normal/low pCO2.

This is due to a VQ mismatch, which can be caused by:

• Low V/Q (poor ventilation, good perfusion) - Asthma, Emphysema, Pulmonary fibrosis, Pneumothorax, Mucus plug

• High V/Q (good ventilation, poor perfusion) - PE

Type 2

Characterised by a low pO2 with a high pCO2.

This is due to alveolar hypoventilation, so lungs fail to effectively oxygenate and blow off carbon dioxide. This can be caused by:

• Lung disease - COPD, Pneumonia, Asthma, Pulmonary fibrosis, OSA

• Reduced respiratory drive - Opiates, CNS tumour/trauma

• Neuromuscular disease - MG, GBS, MND

• Chest wall deformity - Rib fracture, Flail chest, Kyphoscoliosis

Presentation

The hypoxia may present with SOB, Cyanosis, Restlessness, Agitation, Confusion.

The hypercapnia may present with Headache, Altered level of consciousness, Warm extremities (due to peripheral vasodilation), Tremor/flap, Papilloedema.

Investigations

• ABG - determines the type of resp failure

  • Bicarb will be raised as metabolic compensation in chronic CO2 retainers

• Bloods - FBC, U&E, CRP

• CXR

• Spirometry

• ECG

• Cultures if febrile

Management

For Type 1 RF:

• Give O2

• Treat underlying cause

For Type 2 RF:

• Treat underlying cause

• Give O2 via Venturi mask

  • Venturi mask allows for controlled delivery of O2 as these patients may have a hypoxic respiratory drive, therefore, giving too O2 much may lead to respiratory depression

N.B. Naturally, we have a respiratory area driven by CO2 levels. In CO2 retainers, their bodies adapt so that their breathing is driven by O2 instead.

Patients should be monitored with SaO2 and Repeat ABGs