Comparison of muscle oxygenation, dyspnea, oxygen uptake and energy expenditure during upper and lower limb cardiopulmonary exercise test in patients with ILD

<bold>Background:</bold> Due to ventilation disorder and impaired pulmonary gas exchange, pulmonary function exhibits impaired exercise capacity and exertional hypoxemia in patients with interstitial lung diseases (ILD). In our clinical experience, patients with ILD respond better to upper extremity exercise testing and training than lower extremity. However, it has yet to be investigated. This study compares oxygen uptake (VO_2peak), muscle oxygenation (SmO₂), dyspnea, and energy expenditure during upper and lower extremity CPETs in patients with ILD. <bold>Methods:</bold> A cross-over study, 11 patients with ILD were included. PeakVO₂ (CPET), quadriceps femoris (QF), and deltoid muscle oxygenation (near-infrared spectroscopy), energy expenditure (metabolic holter), and dyspnea (Modified Borg Scale) were compared during upper and lower extremity CPETs. <bold>Results:</bold> Active energy expenditure (p<0.05), VO_2peak (p=0.01), and dyspnea (p=0.009) were statistically significantly higher, and SpO₂ was lower (p=0.047) at max. lower extremity CPET. The QF SmO₂ at max. during lower extremity CPET was significantly decreased compared with the upper extremity CPET (p<0.05). Deltoid SmO₂ and total energy expenditure were similar in groups (p˃0.05). <bold>Conclusion:</bold> Patients with ILD experience less desaturation and dyspnea during arm activities but expend more active energy during leg activities, with the total energy expenditure being similar in both. QF used more oxygen during leg exercises, while the deltoid used the same oxygen level during both exercises. Patients respond better to upper extremity exercises regarding oxygenation and dyspnea, which is better to be preferred.