Quantifying leg muscle deoxygenation during incremental cycling in hypoxemic patients with fibrotic interstitial lung disease. (8th January 2023)

• Record Type: Journal Article
• Authors: Marillier, Mathieu; Bernard, Anne‐Catherine; Verges, Samuel; Moran‐Mendoza, Onofre; Neder, J. Alberto
• Is Part Of: Clinical physiology and functional imaging. Volume 43:Number 3(2023)
• Page Start: 192
• Page End: 200
• Publication Date: 2023-01-08
• Subjects: exercise test -- hypoxia -- interstitial -- lung diseases -- muscle fatigue -- near‐infrared spectroscopy -- oxygen -- pulmonary fibrosis; Physiology, Pathological -- Periodicals; Diagnostic imaging -- Periodicals; 612
• DOI: 10.1111/cpf.12809
• Languages: English
• ISSNs: 1475-0961

Abstract

Abstract: Background: Hypoxaemia and cardiocirculatory abnormalities may impair muscle oxygen (O2 ) delivery relative to O2 requirements thereby increasing the rate of O2 extraction during incremental exercise in fibrotic interstitial lung disease ( f ‐ILD). Using changes in deoxyhaemoglobin concentration ([HHb]) by near‐infrared spectroscopy (NIRS) as a proxy of O2 extraction, we investigated whether a simplified (double‐linear) approach, previously tested in heart failure, would provide useful estimates of muscle deoxygenation in f ‐ILD. Methods: A total of 25 patients (23 men, 72 ± 8 years; 20 with idiopathic pulmonary fibrosis, lung diffusing capacity for carbon monoxide = 44 ± 11% predicted) and 12 age‐ and sex‐matched healthy controls performed incremental cycling to symptom limitation. Changes in vastus lateralis [HHb] assessed by NIRS were analysed in relation to work rate (WR) and O2 uptake throughout the exercise. Results: Patients showed lower exercise capacity than controls (e.g., peak WR = 67 ± 18% vs. 105 ± 20% predicted, respectively; p < 0.001). The [HHb] response profile was typically S‐shaped, presenting three distinct phases. Exacerbated muscle deoxygenation in patients versus controls was evidenced by: (i) a steeper mid‐exercise [HHb]‐WR slope (0.30 ± 0.22 vs. 0.11 ± 0.08 μmol/W; p = 0.008) (Phase 2), and (ii) a larger late‐exercise increase in [HHb] ( p = 0.002) (Phase 3). Steeper [HHb]‐WR slope was associated with lower peak WR ( r = –0.70) and greater leg discomfort ( r = 0.77; p < 0.001) in f ‐ILD. Conclusion: This practical approach to interpreting [HHb] during incremental exercise might prove useful to determine the severity of muscle deoxygenation and the potential effects of interventions thereof in hypoxemic patients with f ‐ILD.