Respiratory failure diagnostic study of choice

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Hadeel Maksoud M.D.[2]

Overview

Respiratory failure is mainly diagnosed based on clinical presentation. There is no single diagnostic study of choice for the diagnosis of respiratory failure, but respiratory failure can be diagnosed based on history, examination and arterial blood gases.

Diagnostic Study of Choice

• Respiratory failure is mainly diagnosed based on clinical presentation.
• There is no single diagnostic study of choice for the diagnosis of respiratory failure, but respiratory failure can be diagnosed based on history, examination and arterial blood gases.

Sequence of Diagnostic Studies

The arterial blood gases should be performed when:

• The patient has been assessed for airway, breathing and circulation.
• A venous line has been established and oxygen is administered in cases of desaturation.

Diagnostic Criteria

Hypoxic respiratory failure

• Patients with a pre-existing chronic lung disease with an initial pulse oximetry (PaO2) on room air less than 80% or a decreasing pulse oximetry starting at 92%.
• A pulse oximetry less than 60mmHg is categorized as severe respiratory failure.
• Patients usually have a preexisting lung condition where pulse oximetry readings are already low, with baselines being as low as 50mmHg.
• A fall of pulse oximetry that is more than 10% indicates entrance into respiratory failure.

Hypercapnic respiratory failure

• Patients with a pre-existing chronic lung disease with an initial pulse oximetry on room air less than 80% or a decreasing pulse oximetry starting at 92% AND an acute increase in the PaCO2 more than 45mmHg.
• An elevation in PaCO2 is usually accompanied by an acidosis, demonstrated by a pH below 7.35.
• Patients usually have a preexisting lung condition and can tolerate an increase in PaCO2 up to 80mmHg with renal compensation.
• A fall in pH indicates entrance into respiratory failure.