Reply to the letter regarding the article ‘Bending oxygen saturation index and risk of worsening heart failure events in chronic heart failure’

We appreciate the interest and comments of Nahar et al. about our study.1 In this work, we found that bending oxygen saturation index (BOSI) but not bendopnea (defined as patient-reported shortness of breath within the 30 s of bending2) predicted the occurrence of worsening heart failure (HF) in a cohort of stable ambulatory patients with HF.1 Interestingly, a reduction of saturation index when bending >2% identified patients at higher risk of an episode of worsening HF in the whole cohort and without evidence of heterogeneity in the most representative subgroups of patients (age ≥75 vs. <75 years, male vs. female, left ventricular ejection fraction ≥50 vs. <50%, and body mass index ≥30 vs. <30 kg/m2).1 Unfortunately, the current study could not address the influence of chronic obstructive pulmonary disease and other comorbid conditions, in which bendopnea is also frequent, due to a lack of adequate statistical power to infer solid risk estimates. We agree that our findings require further confirmation and better pathophysiological and clinical characterization. For instance, the utility of BOSI for predicting future HF decompensations in patients with other conditions/comorbidities in which bendopnea/BOSI is also a frequent finding requires special attention and investigation. Moreover, as detailed in the limitations section, echocardiographic data were not obtained on the same day BOSI was assessed (median [interquartile range] time from echo to enrolment was 164 [55–259] days). Accordingly, time-frame differences in loading conditions between echocardiography and BOSI assessment preclude a formal evaluation of