1.It is commonly caused by chronic alveolar hypoventilation or air way mucus plugging.

1.究其原因，可能为肺泡慢性通不道分物阻。

2.Chronic hypoventilation is a marker of disease severity in asthma and chronic obstructive pulmonary disease (COPD).

2.和COPD患者出现慢性低通是疾病严重标志之一。