Comparison of muscle oxygenation during Cardiopulmonary exercise and Six-minute walk tests in patients with primary immunodeficiency

<bold>Background:</bold> Primary immunodeficiencies (PID) are rare disorders of the immune system encompassing inborn errors of immunity leading to pulmonary complications frequently, which may affect exercise capacity. The impact of varying exercise intensities on muscle oxygenation is questioned. This study aims to compare muscle oxygenation during the 6-minute walk (6MWT) and cardiopulmonary exercise tests (CPET) in patients with PID. <bold>Methods:</bold> A cross-sectional study. Ten children with PID (9-13 y) were included. Pulmonary function (spirometer), and quadriceps femoris (QF) muscle strength using a handheld dynamometer were evaluated. Muscle oxygen saturation and total hemoglobin levels were measured (near infrared spectroscopy (NIRS) device) during CPET and 6MWT. <bold>Results:</bold> Muscle saturation at rest, minimal and maximal during exercise and recovery, were similar during the CPET and 6MWT (p>0.05). Meanwhile, THbmax and THbrecovery were higher during CPET with significant difference (p<0.05). 90% of patients had 6MWD, 60% had VO_2max and 50% had QF muscle strength less than 80% of expected. Also, 40% had obstructive pulmonary function abnormality. <bold>Conclusions:</bold> The majority of the patients had impaired functional and maximal exercise capacity. Nearly half of the patients had obstructive pulmonary function and QF muscle weakness. Muscle oxygen saturation responses were similar during submaximal and maximal tests, however THb levels exhibit elevated during CPET. These findings highlight the importance of a proactive approach to address multifaceted challenges faced by patients with PID. The effects of pulmonary rehabilitation in patients with PID needs to be investigated.