Comparison of the 1-min Sit-to-Stand Test to the 6-minute Walk Test in the Respiratory Functional Assessment of Pulmonary Fibrosis

Overview

Fibrosing interstitial lung diseases or pulmonary fibrosis represent a heterogeneous group of progressive pulmonary pathologies, responsible for a significant morbi-mortality. They are defined by an infiltration of the pulmonary interstitium associating in a variable way an inflammatory component (deposit of inflammatory cells) and a fibrosing component (deposit of collagen). Idiopathic pulmonary fibrosis (IPF) is the most common and most severe pulmonary fibrosis. Other pulmonary fibroses are mainly represented by non-specific interstitial lung disease, pulmonary fibroses associated with connectivites, hypersensitivity pneumonitis, certain pneumoconiosis (occupational diseases) and sarcoidosis. The process of fibrosis is responsible for a loss of elasticity of the lung, leading to a decrease in lung volumes associated with an alteration of gas exchange. In these diseases, the clinician must be able to rely on reliable means to assess the severity of the disease based mainly on the measurement of lung volumes and gas exchange, at diagnosis and in the follow-up of the patient, in order to propose the most appropriate management. Lung volumes are assessed by respiratory function tests. Forced vital capacity is the reference volume value used. Impaired gas exchange is assessed at rest by measuring carbon monoxide diffusion capacity, arterial oxygen saturation and arterial blood gases. The functional capacity to exercise is also a very important evaluation criterion in terms of prognosis and in the follow-up of the patient. It is assessed by means of ergocycle tests which mainly determine the maximal oxygen consumption. These are relatively complex tests that require special equipment and are not routinely performed. Simpler field tests have been developed to assess functional capacity during exercise, the most widely used and validated being the 6-minute Walk Test (TM6). Other field tests to assess functional capacity to exercise have been developed, such as the 30-second, 1-minute, and 3-minute chair lift tests, stepper tests, and step and stair tests. Among them, the 1-minute chair lift test (TLC1) is the best evaluated. It consists of sitting down and getting up from a chair as many times as possible in 1 minute. The criteria measured are mainly the number of lifts and desaturation. Thus, the fundamental advantage of the TLC1 over the TM6 is the exemption from temporal and spatial constraints since it takes only a few minutes and can be performed in a medical office. While TLC1 seems to be the most suitable, there are still a few pitfalls in substituting TLC1 for TM6 during diffuse interstitial lung disease. First, there is only one study reporting the results of TLC1 in a healthy population. It provides a chart of results according to age. Unfortunately, only the number of lifts is reported without any data on heart rate, SaO2 or sensation of dyspnea. In respiratory pathologies, TLC1 has been studied mainly in patients with chronic obstructive pulmonary disease (COPD) and little in PID. Unlike TM6, TLC1 is reproducible and has no learning effect in this population. Interestingly, one study found that peak desaturation and peak oxygen consumption occurred during the recovery phase some seconds after the end of the test. Studies on TLC1 during SID do not allow us to conclude that this test can substitute for TM6. However, investigators may note certain limitations, in particular the small number of patients studied and the retrospective nature of the 2 largest of them. Above all, it seems that the use of TLC1 could be optimized by taking into account the recovery phase in the evaluation of desaturation. The hypothesis of our study is that the TLC1 taking into account the recovery phase can replace the TM6 in the management of fibrosing PID for prognostic evaluation, patient follow-up and indication of oxygen therapy. It is more accessible and its use by all practitioners in face-to-face or telemedicine would allow a better management of these patients. Finally, the investigators hypothesize that the TLC1 will result in lower costs in the management of these patients.