MRC chronic Dyspnea Scale: Relationships with cardiopulmonary exercise testing and 6-minute walk test in idiopathic pulmonary fibrosis patients: a prospective study

Abstract

BackgroundExertional dyspnea is the most prominent and disabling feature in idiopathic pulmonary fibrosis (IPF). The Medical Research Chronic (MRC) chronic dyspnea score as well as physiological measurements obtained during cardiopulmonary exercise testing (CPET) and the 6-minute walk test (6MWT) are shown to provide information on the severity and survival of disease.MethodsWe prospectively recruited IPF patients and examined the relationship between the MRC score and either CPET or 6MWT parameters known to reflect physiologic derangements limiting exercise capacity in IPF patientsResultsTwenty-five patients with IPF were included in the study. Significant correlations were found between the MRC score and the distance (r = -.781, p < 0.001), the SPO2 at the initiation and the end (r = -.542, p = 0.005 and r = -.713, p < 0.001 respectively) and the desaturation index (r = .634, p = 0.001) for the 6MWT; the MRC score and VO2 peak/kg (r = -.731, p < 0.001), SPO2 at peak exercise (r = -. 682, p < 0.001), VE/VCO2 slope (r = .731, p < 0.001), VE/VCO2 at AT (r = .630, p = 0.002) and the Borg scale at peak exercise (r = .50, p = 0.01) for the CPET. In multiple logistic regression analysis, the only variable independently related to the MRC is the distance walked at the 6MWT.ConclusionIn this population of IPF patients a good correlation was found between the MRC chronic dyspnoea score and physiological parameters obtained during maximal and submaximal exercise testing known to reflect ventilatory impairment and exercise limitation as well as disease severity and survival. This finding is described for the first time in the literature in this group of patients as far as we know and could explain why a simple chronic dyspnea score provides reliable prognostic information on IPF.

Physiology of the lung in idiopathic pulmonary fibrosis

“…Indirect evidence suggests key roles of dead space ventilation in the genesis of dyspnoea, although the lack of a possibility to experimentally amend the VD/VT ratio precludes definitive demonstration. In a series of 25 IPF patients, the V′E/V′CO 2 slope, which is tightly correlated with VD/VT, was the physiological parameter most strongly correlated with patient-reported exertional dyspnoea [135]. In addition to alterations in pulmonary anatomy and physiology, anaemia may occasionally contribute to gas exchange abnormalities in patients with IPF.…”

Oxygen desaturation during a 6-minute walk test as a predictor of maximal exercise-induced gas exchange abnormalities in sarcoidosis

“…DLco was a poor predictor of ∆SpO 2 -6MWT (PPV 36% and NPV 88%) and of peak AaDO 2 (PPV 66% and NPV 78%). Importantly, normal DLco was a good predictor of the absence of severe desaturation during the 6MWT and at peak exercise during CPET (NPV 94% and 100%, [31] 97 [19] 83 [25] 90 [11] 66 [30] a,b,c 0.00001 FVC (% pred) 92 [24] 98 [26] 96 [21] 102 [19] 79 [32] a,b,c 0.001 TLC (% pred) 90 [19] 88 [14] 90 [21] 93 [29] 88 [24] 0.644 FEV 1 /FVC (%) 75 [15] 80 [8] 75 [15] 79 [12] 71 [24] a,b,c 0.011 DLco (% pred) 71 [25] 82 [18] 76 [23] 73 [17] 55 [23] a,b,c 0.00001…”

“…Measurement of ∆SpO 2 -6MWT as performed in the present study has recently been added to the international guidelines for walking tests (12). Although this test has not been investigated extensively, it is reproducible (13) and correlates with symptom intensity (14), results of pulmonary function testing (15), changes on computed tomography (CT) scans (16), and prognosis (17)(18)(19) in interstitial lung diseases. However, the correlation between ∆SpO 2 -6MWT and peak AaDO 2 and, in particular, the ability of ∆SpO 2 -6MWT to predict peak AaDO 2 , are unknown.…”

Sleep Oxygen Desaturation Predicts Survival in Idiopathic Pulmonary Fibrosis

“…4,5 The latter, is the most prominent and disabling symptom in IPF and is attributed to several factors including deranged lung mechanics, gas exchange abnormalities, pulmonary vascular disease, myocardial dysfunction, and peripheral muscle weakness. 6 Moreover, exertional dyspnea and oxygen desaturation during exercise are parameters that negatively infl uence the outcome in IPF. 6,7 bRIEF SUMMARY Current knowledge/Study Rationale: Sleep breathing disorders are frequent in idiopathic pulmonary fi brosis.…”

“…6 Moreover, exertional dyspnea and oxygen desaturation during exercise are parameters that negatively infl uence the outcome in IPF. 6,7 bRIEF SUMMARY Current knowledge/Study Rationale: Sleep breathing disorders are frequent in idiopathic pulmonary fi brosis. The aim of the study was to examine the relationship between SBDs and clinical and functional parameters of IPF, and to evaluate the impact of SBDs on survival in IPF.…”