Desaturation - distance ratio: a new concept for a functional assessment of interstitial lung diseases

作者：Pimenta Suzana Pinheiro^*; da Rocha Renata Barbosa; Baldi Bruno Guedes; Kawassaki Alexandre de Melo; Kairalla Ronaldo Adib; Ribeiro Carvalho Carlos Roberto

来源：Clinics, 2010, 65(9): 841-846.

DOI：10.1590/S1807-59322010000900005

• The six-minute walk test
• Pulmonary function tests
• Interstitial lung diseases

INTRODUCTION: The functional evaluation has become increasingly important in the understanding and management of patients with interstitial lung diseases. The cardiopulmonary exercise test and the six-minute walk test (6MWT), through their isolated variables, have been used to do this evaluation, with some limitations.
OBJECTIVES: We proposed a new composite index (desaturation distance ratio using continuous peripheral oxygen saturation (SpO(2)) and the distance walked as a more reliable tool for doing a functional evaluation of these patients.
METHODS: 6MWT was performed by interstitial lung diseases patients and controls. Analyzed parameters were walked distance and desaturation area (DAO(2)), obtained by taking the difference between maximal SpO(2) possible (100%) and patient's SpO(2) every 2 seconds. desaturation distance ratio was calculated using the ratio between DAO(2) and distance walked.
RESULTS: Forty-nine interstitial lung diseases patients and 11 control subjects completed the protocol. The mean (SD) age was 60 (12) years and 65 (9) years, respectively (p:NS). Data obtained from 6MWT showed a significant statistical difference between interstitial lung diseases patients and controls: mean walked distance (430 and 602 meters, respectively); SpO(2) minimal maintained at least 10 seconds -SpO(2) min (85% and 94%, respectively), and median desaturation distance ratio (10 and 2.5, respectively). A correlation analysis, considering interstitial lung diseases patients, revealed the best correlation between desaturation distance ratio and DLco (r = -0.72; p<0.001), being the correlation between SpO(2) min and DLco of 0.61 (p<0.001) and among walked distance and DLco of 0.58 (p<0.05).
CONCLUSION: Desaturation distance ratio is a promising concept and a more reliable physiologic tool to assess pulmonary diseases characterized by involvement of the alveolar-capillary membrane, such as interstitial lung diseases.

• 出版日期2010-9