A patient with chronic obstructive pulmonary disease (COPD) may develop acute hypercapnia if supplemental oxygen is given.


Situation: A patient with COPD who is spontaneously breathing may have a rise in PaCO2 once supplemental oxygen therapy is started. Some patients may develop acute respiratory failure.


Significance: A pH < 7.26 (hydrogen ion >= 55 nmol/L) is associated with a worse outcome.


Mechanisms that have been proposed:

(1) worsening of ventilation-perfusion matching (die to inspired oxygen causing increased perfusion of poorly ventilated lung)

(2) suppression of the hypoxic drive


Additional risk factors for a poor outcome:

(1) hypotension

(2) renal failure with uremia


A patient with COPD who is started on supplemental oxygen should be monitored for clinical deterioration and worsening of blood gas parameters.


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