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Comparison of Continuous and Discrete Measurements of Dyspnea During Exercise in Patients With COPD and Normal Subjects:

Comparison of Continuous and Discrete Measurements of Dyspnea During Exercise in Patients With COPD and Normal Subjects: Cardiopulmonary exercise testing was conducted while the subject was seated on the electronically braked cycle ergometer (Ergo-Metrics 800S; SensorMedics; Yorba Linda, CA) and breathing ambient air through a mouthpiece. Expired gas was analyzed for Ve and Vo2 with every breath, using a metabolic measurement system (Medgraphics Cardiorespiratory Diagnostic Systems; St. Paul, MN). After a 1-min equilibration period, the subject pedaled at a speed of 50 revolutions per minute at zero resistance for 1 min. Then the resistance of the cycle ergometer was electronically increased in 15 W/min increments using a ramp protocol until the subject stopped because of symptom limitation.

The system used to rate breathlessness consisted of a computer, a monitor, and a mouse (Fig 1). The computer system presented numbers from 0 (top of the screen) to 10 (bottom of screen) listed on the left side of the screen, and descriptors of the severity of breathlessness were displayed on the right side of the screen. The nature and spacing of the numbers and descriptor categories were identical to the scale developed by Borg. The total length of the scale was 15.25 cm; the Geneva font size of the letters for the category descriptors was No. 12. The numbers and descriptors on the screen (positioned approximately 70 cm from the subjects’ eyes) were easy for all subjects to read when seated on the cycle ergometer. The mouse rested on a small horizontal platform attached to the handlebar of the cycle ergometer. At the onset of exercise, the black bar (continuous method) or crosshairs (discrete method) appeared at zero on the scale. other

For the discrete method, the subject provided a rating each minute during exercise on cue by an investigator by adjusting crosshairs (0.5 cm by 0.5 cm) to a position on the scale and then pressing the mouse button. The subjects read the following written instructions before performing the exercise test:
This is a scale for rating breathlessness. The No. 0 represents no breathlessness. The No. 10 represents the strongest or greatest breathlessness that you have ever experienced. Each minute during the exercise test you will be asked to select a number that represents your perceived level of breathlessness by positioning the crosshairs of the cursor on your selection and pressing the mouse button. Use the written descriptors to the right of the numbers to help guide your selection.
Fig1
Figure 1. Schematic diagram of a subject seated on the cycle ergometer. The computer mouse is positioned on a platform supported on the handlebars. The arrows adjacent to the platform indicate that the subject can move the mouse forward or backward to indicate an increase or decrease in breathlessness, respectively. The monitor displays the vertical bar (or crosshairs for the discrete method) that can be changed in length by adjusting the mouse in response to changes in the severity of breathlessness.