PaO2 increases with coughing in patients with chronic lung disease

We considered if the cyanosis frequently observed during a cough attack in patients with chronic lung disease was due to worsening hypoxemia. To investigate the effects of cough on PaO₂, we measured arterial blood gases before and after a voluntary coughing period of 45 sec, in 11 patients with Interstitial Lung Disease (ILD) and 14 patients with Chronic Obstructive Lung Disease (COPD). All patients significantly increased (p < 0.05) their PaO₂ (COPD: from 49 ± 2 to 60 ± 2 mmHg; ILD from 44 ± 2 to 51 ± 3 mmHg, mean ± SD) and decreased their PaCO₂. We conclude that stable patients with COPD and ILD increase their PaO₂ with coughing most likely due to hyperventilation. The cyanosis observed could be due to peripheral circulatory effects of coughing.