Table 3.
Summary of pathophysiological changes
| Quantity | IPAH preserved DLCO | IPAH low DLCO (lung phenotype) | CPFE | Emphysema |
|---|---|---|---|---|
| Airspace enlargement | ||||
| LAA (CT) | 0 | 0 | + | ++ |
| S/V (129Xe MRI) | 0 | − | (−) | −− |
| Capillary rarefication | ||||
| RBC fraction η | 0 | − | − | 0 |
| RBC-TP | 0 | − | − | 0 |
| Capillary blood flow | ||||
| Capillary transit time τ | + | − | 0 | 0 |
| RBC oscillation amplitude | − | − | 0 | 0 |
| Alveolar membrane function | ||||
| Membrane permeability κ | − | − | − | − |
| RBC chemical shift (oxygenation) | 0 | −− | −− | − |
| Ventilation heterogeneity | ||||
| Ventilation defect percentage | + | + | + | ++ |
| FEV1 as % of predicted value | 0 | − | − | −− |
Reference values for parameters from CSSR measurements in a group of 12 healthy volunteers reported in [17] (7 male/5 female, age 49 years ± 14 years) are κ: 0.051 cm/s ± 0.023 cm/s, η: 0.247 ± 0.041, τ: 0.67 s ± 0.18 s. Similarly, for fixed-TR dynamic spectroscopy, reference values are average RBC-M: 1.04 ± 0.17, RBC oscillation amplitude: 3.5% ± 0.5%, RBC chemical shift 18.7 ppm ± 0.4 ppm
++ strongly increased, + increased, 0 equal, − reduced, −− strongly reduced, CPFE combined pulmonary fibrosis and emphysema, DLCO diffusion capacity of the lung for carbon monoxide, FEV1 forced expiratory volume in 1 s, GP gas phase, IPAH idiopathic pulmonary arterial hypertension, LAA low-attenuation area, M membrane tissues, RBC red blood cell, S/V surface/volume