Cigarette Smoking and Secondary Polycythemia in Hypoxic Cor Pulmonale

Our plain-English summary of Cigarette Smoking and Secondary Polycythemia in Hypoxic Cor Pulmonale, by P.M.A. Calverley, R.J. Leggett, L. McElderry, et al (1982).

The study

• Authors: P.M.A. Calverley, R.J. Leggett, L. McElderry, D.C. Flenley
• Published: 1982
• Type of article: Journal article
• Our copy: from Johns-Manville's own medical library. The article is still under copyright, so we describe it here rather than post it.

In plain English

This article does not concern asbestos. It is a study from the University of Edinburgh, published in 1982, of 47 patients with hypoxic cor pulmonale caused by chronic bronchitis and emphysema. The authors compared red cell mass, a measure of polycythemia (too many red blood cells), with smoking status and blood carboxyhemoglobin, which reflects carbon monoxide from cigarette smoke. The 31 smokers had a mean red cell mass of 42.5 ml/kg. The 16 nonsmokers had a mean of 29.7 ml/kg, a significant difference (p less than 0.01), even though the two groups had similar lung function and blood oxygen levels. In 40 patients followed for 6 to 36 months, average carboxyhemoglobin correlated with red cell mass (r = 0.73). Fifteen patients then received oxygen for 15 hours a day for 12 months. Red cell mass did not change significantly in the 7 who kept smoking. In the 8 who stopped smoking it fell from 43.4 to 28.0 ml/kg (p less than 0.001). The authors concluded that cigarette smoking may determine the severity of secondary polycythemia in these patients and prevent its correction by long-term oxygen therapy.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Clinical study comparing smokers and nonsmokers at one point in time, plus a 12-month follow-up of 15 patients receiving long-term oxygen therapy
• Who was studied: 47 patients with hypoxic cor pulmonale secondary to chronic bronchitis and emphysema (27 men, 20 women; 31 smokers, 16 nonsmokers), studied at the University of Edinburgh, Scotland. 15 of them were restudied after 12 months of oxygen therapy. Study dates are not stated.
• Exposure: Cigarette smoking, measured through carbon monoxide bound to hemoglobin (carboxyhemoglobin). Patients counted as nonsmokers only if their carboxyhemoglobin was below 3% and they had not smoked for 2 years. No asbestos exposure was studied.
• Main results:
  • Smokers and nonsmokers did not differ significantly in age, severity of airway obstruction, or resting blood oxygen.
  • Mean red cell mass was 42.5 ml/kg in the 31 smokers and 29.7 ml/kg in the 16 nonsmokers (p less than 0.01).
  • Plasma volume was also significantly higher in smokers (mean 41.5 ml/kg) than in nonsmokers (mean 35.3 ml/kg), p less than 0.01.
  • In the 31 smokers, red cell mass correlated more strongly with an oxygen saturation measure that accounts for carbon monoxide (r = -0.58) than with the measure that ignores it (r = -0.36). Neither measure correlated significantly with red cell mass in the 16 nonsmokers.
  • In 40 patients, average outpatient carboxyhemoglobin correlated with red cell mass (r = 0.73, p less than 0.01).
  • After 12 months of oxygen therapy, red cell mass did not change significantly in the 7 patients who kept smoking.
  • In the 8 patients who stopped smoking, mean red cell mass fell from 43.4 ml/kg to 28.0 ml/kg over the year (p less than 0.001). Packed cell volume and mean pulmonary artery pressure fell significantly only in this group.
• The authors' conclusion: The authors concluded that cigarette smoking may determine the severity of secondary polycythemia in patients with hypoxic COPD, and may prevent its correction by long-term oxygen therapy.
• Limitations the authors state:
  • The authors suggested that low oxygen levels not measured at rest, such as during exercise or at night, could account for some of the remaining variation in red cell mass.
  • The higher red cell mass in men than in women may have been due to more of the men being smokers.

Topics

Medical terms in this study, explained in our Lexicon: Cor Pulmonale, Emphysema, Supplemental Oxygen.

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