Purpose: The steep ramp test (SRT) can be used to provide an indication of exercise capacity when gas exchange measurements are not possible. This study evaluated the clinical usefulness of the SRT in adolescents with cystic fibrosis (CF) and compared the physiological responses of the SRT with the standard cardiopulmonary exercise test (CPET).
Methods: Forty patients with CF (17 boys and 23 girls; mean ± SD age, 14.7 ± 1.7 years; forced expiratory volume in 1 s, 86% ± 18% of predicted) performed an SRT and a CPET with respiratory gas analysis in a randomized balanced design. Peak work rate (WRpeak), HRpeak, peak minute ventilation (V˙Epeak), and peak oxygen uptake (V˙O2peak) were the main outcome measures.
Results: Patients with CF attained values for absolute and relative WRpeak during the SRT of 82% ± 14% and 92% ± 14% of predicted. Nutritional status and degree of airway obstruction did not influence SRT performance. Significantly higher values were attained for WRpeak during the SRT compared with those during the CPET (252 ± 60 vs 174 ± 46 W; P < 0.001), whereas significantly lower values were achieved for HRpeak (168 ± 14 vs 182 ± 12 bpm; P < 0.001), V˙Epeak (59.2 ± 19.5 vs 72.0 ± 20.2 L·min−1; P = 0.006), and V˙O2peak (36.9 ± 7.5 vs 41.5 ± 7.6 mL·kg−1·min−1; P = 0.008). A strong correlation between WRpeak attained at the SRT and the V˙O2peak achieved during the CPET was found (r = 0.822, P < 0.001).
Conclusions: The SRT seems to be a quick, convenient, and low-cost exercise test that is well-tolerated in patients with CF with mild-to-moderate airway obstruction. It provides an indication of exercise capacity and can potentially be used when exercise testing using gas exchange measurements is not possible.
1Child Development and Exercise Center, Wilhelmina Children’s Hospital, University Medical Center Utrecht, Utrecht, the NETHERLANDS; 2Department of Epidemiology, School for Public Health and Primary Care, Maastricht University, Maastricht, the NETHERLANDS; 3De Kinderkliniek, Almere, the NETHERLANDS; and 4Department of Pediatric Respiratory Medicine, Wilhelmina Children’s Hospital, University Medical Center Utrecht, Utrecht, the NETHERLANDS
Address for correspondence: Tim Takken, M.Sc., Ph.D., Child Development and Exercise Center, Wilhelmina Children’s Hospital, University Medical Center Utrecht, KB.02.056.0, PO Box 85090, 3508 AB Utrecht, the Netherlands; E-mail: firstname.lastname@example.org.
Submitted for publication March 2014.
Accepted for publication June 2014.