Late Breaking Abstract - Effects of a supervised 12-week high intensity interval training (HIIT) programme on lung tissue mass and diffusing capacity in COPD: A case-control study

<bold>Aim:</bold> Patients with COPD have attenuated pulmonary diffusing capacity at rest and during exercise due to a progressive, seemingly irreversible loss of lung tissue. This study aimed to investigate if a 12-week HIIT program can increase lung tissue mass (LTM) and improve pulmonary diffusing capacity during exercise in COPD patients compared to matched healthy controls. <bold>Methods:</bold> Twelve COPD patients and twelve healthy matched controls, participated. At baseline and follow-up, all underwent a SPECT-CT scan with intravenous 99mTc-labelled macro-aggregated albumin to assess LTM and pulmonary perfusion distribution, both at rest and during exercise. Pulmonary diffusing capacity for nitric oxide (DL,NO) was measured during seated rest and exercise using the single breath method. Participants followed a 12-week supervised HIIT intervention with three weekly 40-minute 4x4 HIIT sessions on a bicycle ergometer. <bold>Results:</bold> Both groups had a significant increase in maximum oxygen consumption. LTM was lower in COPD than controls and unaffected by HIIT. DL,NO was higher in the control group, increased more during exercise than in COPD, but was not affected by HIIT in either group (Figure 1A). However, relative apical perfusion increased in the COPD group post-HIIT, not observed in controls (Figure 1B). <bold>Conclusion:</bold> The 12-week HIIT improved fitness in both COPD and control group but did not affect LTM or DL,NO at rest or during exercise, though apical perfusion was enhanced during exercise in the COPD group at follow-up.