Upper third to lower third width ratio on chest x-ray may predict severity of obstruction in obstructive lung disease

The symptoms and functional limitations due to obstructive lung disease (OLD) are the direct results of airway and lung parenchymal destruction. In these conditions, airflow obstruction leads to increased work of breathing, and gas exchange abnormalities. Hyperinflation, which is inferred from a standard chest radiograph (CXR), may imply increased total lung capacity that can be seen in patients with OLD. Based on experimental observations in OLD patients, we proposed that upper third width in posterioranterior (PA) CXR could be used as a rapid screening method for suggestion of OLD.

In this cross-sectional study, 99 patients admitted to the Respiratory Ward of Razi Medical Center, a teaching referral hospital affiliated to Guilan University of Medical Sciences (GUMS), were entered in the study. The inclusion criteria were any FEV1 with FEV1/FVC <70% or FEV1/FVC>70% with MMEF 75/25 <65%. All cases with diagnostic possibilities other than OLD were excluded. The PA and lateral CXR were performed and 13 measurements - including previous well-known measurements and our proposed new ones- were made by an ordinary ruler on the films.

There was no significant correlation between the upper third width and superior/inferior (sup/inf) ratio with spirometric indices in patients. When considering only patients with FEV1/FVC <70%, middle third proportion width had a significant correlation with FEV1/FVC. In subgroup analysis when considering sup/inf ratio > 0.8, superior and inferior third widths were correlated with FEV1/FVC and when considering sup/inf ratio > 0.9, sup/inf ratio was significantly correlated with FEV1/FVC and FEV1.

The sup/inf ratio >0.9 in PA CXR, may be a predictor of obstructive pattern in OLD patients. For better correlation determination, larger and more extensive studies are needed.