A step test to assess exercise-related oxygen desaturation in interstitial lung disease

Abstract

A 6-min step test (6MST) may constitute a practical method for routinely assessing effort tolerance and exercise-related oxyhaemoglobin desaturation (ERD) in the primary care of patients with interstitial lung disease.In total, 31 patients (19 males) with idiopathic pulmonary fibrosis (n525) and chronic hypersensitivity pneumonia were submitted, on different days, to two 6MSTs. Physiological responses were compared with those found on maximal and submaximal cycle ergometer tests at the same oxygen uptake (V9O 2 ). Chronic breathlessness was also determined, as measured by the baseline dyspnoea index (BDI).Responses to 6MST were highly reproducible: 1.3¡2.0 steps?min -1 , ¡5 beats?min -1 (cardiac frequency), ¡50 mL?min -1 (V9O 2 ), ¡7 L?min -1 (minute ventilation) and ¡2% (arterial oxygen saturation measured by pulse oximetry (Sp,O 2 )). The number of steps climbed in 6 min was correlated to peak V9O 2 and the BDI. There were significant associations among the tests in relation to presence (change in Sp,O 2 between rest and exercise o4%) and severity (Sp,O 2 ,88%) of ERD. Four patients, however, presented ERD only in response to 6MST. Resting diffusing capacity of the lung for carbon monoxide and alveolar-arterial oxygen tension difference were the independent predictors of the number of steps climbed. A single-stage, self-paced 6-min step test provided reliable and reproducible estimates of exercise capacity and exercise-related oxyhaemoglobin desaturation in interstitial lung disease patients.

Reproducibility of step tests in patients with bronchiectasis

“…Interestingly, Swinburn et al 26 described a constant-load-type step test because its pace was maintained at 15 steps/min; however, this step test cannot be considered submaximal because it revealed a higher oxygen consumption at peak exercise. Our group found a similar result among patients with idiopathic pulmonary fibrosis, in which the 6-min step test with the patient-determined pace accounted for 90% of the VO 2 obtained in the maximal incremental test on a cycle ergometer 23 .…”

“…The reliability of the different step tests has been studied among patients with idiopathic pulmonary fibrosis 23 , COPD 16 , asthma 24 , or cystic fibrosis 25 . Although Swinburn et al 26 observed great variation between the four step tests conducted on patients with COPD, most studies have found the opposite (i.e., little variation between the step tests among patients with chronic lung disease 16,[23][24][25] ). In patients with COPD, the CST was highly reliable for tests conducted on the same day 16 , with an ICC of 0.99 (95% CIs=0.97 to 0.99) for NOSs.…”

Responsividade do teste do degrau de seis minutos a um programa de treinamento físico em pacientes com DPOC

“…Pulmonary function testing (MasterScope®; Jaeger, Hoechberg, Germany) was conducted by the attending pulmonologist before and after bronchodilator use in order to assess reversibility, which was based on changes in FEV 1 , with an increase of more than 12% and at least 0.2 L (6) ; in addition, an FEV 1 /FVC ratio < 70% and the FEV 1 value were used in order to classify patients as having moderate obstruction (50% ≤ FEV 1 < 80% of predicted) or severe obstruction (30% ≤ FEV 1 < 50% of predicted), as defined by the Global Initiative for Chronic Obstructive Lung Disease (GOLD). (7) All technical procedures, as well as the acceptability and reproducibility criteria, were in accordance with the recommendations of the American Thoracic Society.…”

“…Among these tests, the six-minute step test (6MST) has been used as an alternative for assessing such patients, having the advantages of requiring little physical space to be carried out (1) and only a single step for use as an ergometer. (2) However, Dal Corso et al (1) and Swinburn et al (3) reported that step climbing involves working against gravity and the use of muscle groups that are not frequently used during activities of daily living, which produces physiological responses that are different from those of the walk test, making the metabolic and ventilatory demands of step climbing more intense. In addition, it should be borne in mind that the leg muscles in patients with COPD are impaired in terms of strength and endurance because of a reduction in muscle mass and aerobic capacity, (4) compromising performance.…”

“…Testing was stopped if the patient felt unable to proceed or if there were signs or symptoms that made it impossible to continue. (12) The 6MST was performed on a 20-cm-high step, (1) which was 80 cm in length and 40 cm in width and was covered with anti-slip flooring. The test started from a standing position, and the patients were instructed to step up and down the step at their own pace for 6 min, to stop the test temporarily if necessary, and to alternate their legs without the support of their arms, which remained stationary at their sides; the patients performed the test at a freely chosen cadence.…”