Chronic bronchitis laboratory findings

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


Chronic bronchitis has irreversible airflow limitation, especially during forced expiration. This is due to the destruction of lung tissue and increase in resistance to flow in the conducting airways. Thus, it doesn't show an improvement in FEV1 post bronchodilator administration, unlike asthma. This characteristic feature is used as an diagnostic criterion for COPD, i.e. a COPD is diagnosed by spirometry if FEV1/FVC < 70% for a matched control.[1] Arterial blood gas may show hypoxemia with or without hypercapnia depending on the disease severity. pH may be normal due to renal compensation. A pH less than 7.3 usually indicates severe respiratory compromise. A blood sample taken from an artery, i.e. Arterial Blood Gas (ABG), can be tested for blood gas levels which may show low oxygen (hypoxemia) and/or high carbon dioxide (respiratory acidosis if pH is also decreased). A blood sample taken from a vein may show a high blood count (reactive polycythemia), a reaction to long-term hypoxemia.

Laboratory Findings

Pulse Oximetry

Arterial Blood Gas (ABG)

  • ABG may show changes of hypoxemia and hypercapnia depending on the severity of disease.
  • Milder exacerbation may present only with hypoxemia without accompanied hypercapnia.
  • Hypercapnia is usually seen when FEV1 falls below 1 L/s or 30% of the predicted value.
  • A pH value below 7.3 usually indicates a severe exacerbation and respiratory compromise.


Blood Test

Serum Electrolytes

  • COPD patients have irreversible obstruction of airways that causes retention of carbon dioxide. This in turn causes them to develop chronic respiratory acidosis. To compensate for this, the body may develop metabolic alkalosis that leads to increased bicarbonate production. Bicarbonate levels act as useful indicator of disease progression.

Human B-type Natriuretic Peptide


  1. Brusasco V, Martinez F (2014). "Chronic obstructive pulmonary disease". Compr Physiol. 4 (1): 1–31. doi:10.1002/cphy.c110037. PMID 24692133.

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