Abstract
Background: Oxygen transport and utilisation by limb muscles are important determinants of exercise capacity. Near infrared spectroscopy (NIRS) offers a real-time non-invasive measuring of local tissue oxygen saturation (StO2): the ratio of oxygenated to total Hb, which reflects the balance between muscle oxygen supply and utilisation. However, the value of NIRS in PAH is not well established.
Aims and objectives: To evaluate limb muscle StO2 at rest and during exercise in patients with PAH in comparison to mixed venous oxygen (SvO2).
Methods: A prospective cross-sectional study of 18 patients being investigated for PAH was performed. Two single point measurements of quadriceps StO2 (QStO2)were obtained by NIRO-200NX (Hamamatsu Photonics KK, Japan) at rest and during supine cycling (at 50% of VO2peak) during right heart catheterization. These were compared with concurrently obtained measurements of SvO2from the pulmonary artery port of the Swan-Ganz catheter.
Results: 18 patients were studied at rest of whom 13 had PAH and 10 were exercised. Combining all the resting and exercise data points (n=28), QStO2 correlated with SvO2 (r=.56, p=0.002). This correlation persisted when looking at rest (r=.56 , p=0.02) and exercise data (r=.80 , p=0.006) separately. There was no correlation between change in QStO2 and change in SvO2 from rest to exercise (r=.49, p=0.14).
Conclusions: Quadriceps StO2 correlates well with SvO2 at rest and during exercise. NIRS may provide a non-invasive way of assessment of peripheral tissue oxygen availability in PAH.
- Copyright ©ERS 2015
