Pulmonary vascular response patterns during exercise in interstitial lung disease (ILD)

When overt pulmonary hypertension (PH) arises in ILD it contributes to exercise intolerance. Objectives : We sought to determine the functional significance of abnormal pulmonary arterial pressure (PAP) responses to exercise in ILD. Methods : 27 ILD patients without cardiac disease and 11 matched healthy controls underwent invasive cardiopulmonary exercise testing (iCPET). mPAP was indexed to cardiac output (Q T ) during exercise, with mPAP-Q T slope≥3 mmHg-min/L defined as an abnormal pulmonary vascular (PV) response. Results : All control subjects had mPAP-Q T slope<3, whereas 13 ILD patients had mPAP-Q T slope≥3 and 2 other subjects had resting PH with inability to complete iCPET; these 15 patients were labeled ILD-PH . Subjects without PH and with mPAP-Q T slope<3 were labeled ILD-nonPH (n=12). ILD-PH and ILD-nonPH did not differ in terms of age, gender, BMI, pulmonary function testing or degree of exercise desaturation. mPAP-Q T slope was 3.9±0.2 in ILD-PH, but there was no difference between slopes in ILD-nonPH and controls (1.9±0.2 vs. 1.5±0.1 respectively, p>0.05). ILD-PH had lower peak Q T than ILD-nonPH (9.3±0.6 vs. 12.5±0.8; p=0.006), but peak Q T was similar between ILD-nonPH and controls (p>0.05). Peak VO 2 was lower in ILD-PH than in ILD-nonPH (13.0±0.9 ml/kg/min vs. 17±1.1, p=0.012) and controls (19.8±1.7, p=0.003). ILD-PH had increased dead space ventilation (VD), with greater V D /V T and VE/VCO 2 . Conclusion: In ILD, a mPAP-Q>3 is associated with lower peak VO 2 and Q T , as well as increased VD. While non-invasive parameters were unable to predict those with abnormal PV response to exercise, iCPET-derived mPAP-Q T slope may aid in identifying physiologically significant early PV disease in ILD.