Normal expiratory flow rate and lung volumes in patients with combined emphysema and interstitial lung disease: a case series and literature review

Abstract

Pulmonary function tests in patients with idiopathic pulmonary fibrosis characteristically show a restrictive pattern including small lung volumes and increased expiratory flow rates resulting from a reduction in pulmonary compliance due to diffuse fibrosis. Conversely, an obstructive pattern with hyperinflation results in emphysema by loss of elastic recoil, expiratory collapse of the peripheral airways and air trapping. When the diseases coexist, pulmonary volumes are compensated, and a smaller than expected reduction or even normal lung volumes can be found. The present report describes 10 patients with progressive breathlessness, three of whom experienced severe limitation in their quality of life. All patients showed lung interstitial involvement and emphysema on computed tomography scan of the chest. The 10 patients showed normal spirometry and lung volumes with severe compromise of gas exchange. Normal lung volumes do not exclude diagnosis of idiopathic pulmonary fibrosis in patients with concomitant emphysema. The relatively preserved lung volumes may underestimate the severity of idiopathic pulmonary fibrosis and attenuate its effects on lung function parameters.

Figure 1)

Initial chest radiograph of the index case. Peripheral and basilar coarse interstitial markings. Preserved lung volumes suggest underlying emphysema. Also note the the prominent pulmonary artery. Subsequent right heart catheterization revealed a mean pulmonary artery pressure of 40 mmHg

Figure 2)

Pulmonary function results of the index case. Chg Change; DLCO Diffusing capacity for carbon monoxide; ERV Expiratory reserve volume; FEF25-75% Forced expiratory flow between 25% and 75% of forced vital capacity (FVC); FET Forced expiratory time; FEV1 Forced expiratory volume in 1 s; FIVC Forced inspiratory vital capacity; FRC N2 Functional residual capacity by nitrogen; IC Inspiratory capacity; IVC Inspiratory vital capacity; PEF Peak expiratory flow; PFT Pulmonary function test; PIF Peak inspiratory flow; Pred Predicted; Ref Reference; RV Residual volume; SOB Short of breath; TLC Total lung capacity; VA Alveolar volume; VC Vital capacity; Vt Tidal volume

Figure 3)

High-resolution chest computed tomography of the patient. Note the peripheral interstitial fibrosis and honeycombing, with superimposed centrilobular and paraseptal emphysema