Importance of airflow obstruction after thoracoplasty

Thirty six patients previously treated for pulmonary tuberculosis by thoracoplasty were studied to determine the prevalence and effect of airflow obstruction. The mean (SD) FEV1 was 1.3 (0.65) 1 and the mean forced expiratory ratio (FER) 64% (12%). FEV1 was less than predicted in every patient whereas FER was less than predicted in 30, being below the lower 98th percentile in 15 (42%). In the 18 patients who complained of breathlessness the means of the standardised residuals (SR) for FEV1, peak expiratory flow (PEF), and FER were significantly lower and that for residual volume/total lung capacity (RV/TLC) significantly higher than those for the 18 patients who were not breathless (all p less than 0.0001). There was no difference in the smoking history of the two groups. Only three of the 23 patients in whom reversibility of airflow obstruction was assessed showed a greater than 25% increase in PEF. None showed an increase in FEV1 of greater than 15%. The 18 who were breathless had significantly lower values of arterial oxygen tension (PaO2) and higher values of arterial carbon dioxide tension (PaCO2) (p less than 0.0001). Thirteen of these patients were in chronic respiratory failure (PaO2 less than 8.0 kPa or PaCO2 greater than 5.9 kPa, or both) compared with only one of the 18 who were not breathless. The indices correlating best with PaO2 and PaCO2 were SR FEV1 and SR PEF respectively. SR FEV1 accounted for 34% of the variance in PaO2 and SR PEF for 29% of the variance in PaCO2. Airflow obstruction has been found to be common in patients with a thoracoplasty and to be associated with hypoxia and hypercapnia.