Ventilation heterogeneity is increased in patients with chronic heart failure

Abstract

In the healthy lung, ventilation is distributed heterogeneously due to factors such as anatomical asymmetry and gravity. This ventilation heterogeneity increases pathologically in conditions such as asthma, chronic obstructive lung disease, and cystic fibrosis. In chronic heart failure, lung biopsy demonstrates evidence of peripheral lung fibrosis and small airways narrowing and distortion. We hypothesized that this would lead to increased ventilation heterogeneity. Furthermore, we proposed that rostral fluid shifts when seated patients lie supine would further increase ventilation heterogeneity. We recruited 30 ambulatory chronic heart failure patients (57 ± 10 years, 83% male, left ventricular ejection fraction 31 ± 12%) as well as 10 healthy controls (51 ± 13 years, 90% male). Heart failure patients were clinically euvolemic. Subjects underwent measurement of ventilation heterogeneity using the multiple-breath nitrogen washout technique in the seated position, followed by repeat measurements after 5 and 45 min in the supine position. Ventilation heterogeneity was calculated using the lung clearance index (LCI), Sacin and Scond which represent overall, acinar, and small conducting airway function, respectively. Lung clearance index (9.6 ± 1.2 vs. 8.6 ± 1.4 lung turnovers, P = 0.034) and Scond (0.029 ± 0.014 vs. 0.006 ± 0.016/L, P = 0.007) were higher in the heart failure patients. There was no difference in Sacin (0.197 ± 0.171 vs. 0.125 ± 0.081/L, P = 0.214). Measures of ventilation heterogeneity did not change in the supine position. This study confirms the presence of peripheral airway pathology in patients with chronic heart failure. This leads to subtle but detectable functional abnormalities which do not change after 45 min in the supine position.

Maximal exercise does not increase ventilation heterogeneity in healthy trained adults

“…Similarly, Kee and colleagues (Kee et al. ) did not identify any differences in ventilation heterogeneity in association with the rostral fluid shifts of chronic heart failure patients in moving from seated to the supine position, which supports the notion that acute or transient pulmonary edema does not increase ventilation heterogeneity.…”

“…Although we have not investigated for the presence of exercise-induced pulmonary edema, our results suggest that if transient pulmonary edema is the mechanism for EIAH as has been suggested, then transient pulmonary edema does not increase ventilation heterogeneity in healthy trained subjects. Similarly, Kee and colleagues (Kee et al 2015) did not identify any differences in ventilation heterogeneity in association with the rostral fluid shifts of chronic heart failure patients in moving from seated to the supine position, which supports the notion that acute or transient pulmonary edema does not increase ventilation heterogeneity.…”

“…; Kee et al. ). The sensitivity of S cond and S acin suggest a potential role for using these measures of ventilation heterogeneity to assess asthma control (Bourdin et al.…”

“…Furthermore, regional ventilation heterogeneity indices can be calculated for the small conductive airways (S cond ) and the distal acinar regions (S acin ) of the lung (Robinson et al 2013). Studies have demonstrated increased S cond and/or S acin in asthma, chronic obstructive pulmonary disease, bronchiolitis obliterans following lung transplantation and chronic heart failure, with evidence that it may be a more sensitive marker for airway disease than spirometry (Verbanck et al 2004(Verbanck et al , 2006Thompson et al 2014;Kee et al 2015). The sensitivity of S cond and S acin suggest a potential role for using these measures of ventilation heterogeneity to assess asthma control (Bourdin et al 2006;Downie et al 2007).…”

Prediction of COPD and Related Events Improves by Combining Spirometry and the Single Breath Nitrogen Test

“…In some of these studies, a low FEV 1 was due to COPD (33). In chronic heart failure, increased ventilation heterogeneity has furthermore been shown (34). Conceivably, a steep N 2 -slope may be a predictor of cardiovascular disease.…”