A possible alternative exercise test for youths with cystic fibrosis: the steep ramp test.

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.

Ventilatory response to exercise in adolescents with cystic fibrosis and mild-to-moderate airway obstruction.

Data regarding the ventilatory response to exercise in adolescents with mild-to-moderate cystic fibrosis (CF) are equivocal. This study aimed to describe the ventilatory response during a progressive cardiopulmonary exercise test (CPET) up to maximal exertion, as well as to assess the adequacy of the ventilatory response for carbon dioxide (CO2) exhalation. Twenty-two adolescents with CF (12 boys and 10 girls; mean ± SD age: 14.3 ± 1.3 years; FEV1: 78.6 ± 17.3% of predicted) performed a maximal CPET. For each patient, data of a sex- and age matched healthy control was included (12 boys and 10 girls; mean ± SD age: 14.3 ± 1.4 years). At different relative exercise intensities of 25%, 50%, 75%, and 100% of peak oxygen uptake (VO2peak), breathing pattern, estimated ventilatory dead space ventilation (VD/VT ratio), minute ventilation (VE) to CO2 production relationship (VE/VCO2-slope), partial end-tidal CO2 tension (PETCO2), and the VE to the work rate (VE/WR) ratio were examined. VO2peak was significantly reduced in CF patients (P = 0.01). We found no differences in breathing pattern between both groups, except for a significantly higher VE at rest and a trend towards a lower VE at peak exercise in patients with CF. Significantly higher values were found for the estimated VD/VT ratio throughout the CPET in CF patients (P < 0.01). VE/VCO2-slope and PETCO2 values differed not between the two groups throughout the CPET. VE/WR ratio values were significantly higher in CF during the entire range of the CPET (P < 0.01). This study found an exaggerated ventilatory response (high VE/WR ratio values), which was adequate for CO2 exhalation (normal VE/VCO2-slope and PETCO2 values) during progressive exercise up to maximal exhaustion in CF patients with mild-to-moderate airway obstruction.

Chronic inflammation and infection associate with a lower exercise training response in cystic fibrosis adolescents.

Considerable heterogeneity among training-induced effects is observed in patients with cystic fibrosis (CF). We previously showed that longitudinal changes in exercise capacity in adolescents with CF were negatively associated with Pseudomonas aeruginosa (P. aeruginosa) colonization and total immunoglobulin G (IgG) levels, independent of age, pulmonary function and bodyweight. This is the first study investigating whether chronic inflammation and infection also associate with the exercise training response in adolescents with CF. Participants performed a home-based exercise training program for 12 weeks. Pulmonary function, anthropometrics, exercise capacity, markers of inflammation and P. aeruginosa colonization status were measured at baseline. Exercise training-induced changes in pulmonary function and exercise capacity were compared between patients with a low and high inflammation-infection status. Participants with CF with high total IgG levels and P. aeruginosa colonization improved significantly less from the exercise training program, with regard to maximal oxygen consumption. These observations support the hypothesis that chronic systemic inflammation and infection leads to devastating effects on skeletal muscles, hampering skeletal muscle tissue to improve from regular physical exercise. Data further suggest that patients with CF should preferentially be encouraged to engage in regular physical exercise when inflammation and infection status is low (e.g. at a young age).

Estimating peak oxygen uptake in adolescents with cystic fibrosis.

OBJECTIVES: To predict peak oxygen uptake (VO2 peak) from the peak work rate (W peak) obtained during a cycle ergometry test using the Godfrey protocol in adolescents with cystic fibrosis (CF), and assess the accuracy of the model for prognostication clustering. METHODS: Out of our database of anthropometric, spirometric and maximal exercise data from adolescents with CF (N=363; 140 girls and 223 boys; age 14.77 ± 1.73 years; mean expiratory volume in 1 s (FEV1%pred) 86.82 ± 17.77%), a regression equation was developed to predict VO2 peak (mL/min). Afterwards, this prediction model was validated with cardiopulmonary exercise data from another 60 adolescents with CF (28 girls, 32 boys; mean age 14.6 ± 1.67 years; mean FEV1%pred 85.43 ± 20.01%). RESULTS: We developed a regression model VO2 peak (mL/min)=216.3-138.7 × sex (0=male; 1=female)+11.5 × W peak; R(2)=0.91; SE of the estimate (SEE) 172.57. A statistically significant difference (107 mL/min; p<0.001) was found between predicted VO2 peak and measured VO2 peak in the validation group. However, this difference was not clinically relevant because the difference was within the SEE of the model. Furthermore, we found high positive predictive and negative predictive values for the model for prognostication clustering (PPV 50-87% vs NPV 82-94%). CONCLUSIONS: In the absence of direct VO2 peak assessment it is possible to estimate VO2 peak in adolescents with CF using only a cycle ergometer. Furthermore, the regression model showed to be able to discriminate patients in different prognosis clusters based on exercise capacity.

Supramaximal verification of peak oxygen uptake in adolescents with cystic fibrosis.

PURPOSE: To study whether peak oxygen uptake ((Equation is included in full-text article VO2 peak), attained in traditional cardiopulmonary exercise testing (CPET) in adolescents with cystic fibrosis (CF), could be verified by a supramaximal exercise test. METHODS: Sixteen adolescents with CF (forced expiratory volume in 1 second as % of predicted [range, 45%-117%]) volunteered and successively performed CPET and a supramaximal test (Steep Ramp Test [SRT] protocol). RESULTS: Cardiopulmonary exercise testing and the SRT resulted in comparable cardiorespiratory peak values. We found no significant difference in oxygen uptake ((Equation is included in full-text article VO2 peak/kg) between CPET and the SRT (38.9 ± 7.4 and 38.8 ± 8.5 mL min kg, respectively; P = .81). We found no systemic bias for CPET and SRT measurements of (Equation is included in full-text article VO2 peak/kg and no differences between CPET and SRT (Equation is included in full-text article VO2 peak values within and between the maximal and non-maximal effort groups (P > .4). CONCLUSION: The (Equation is included in full-text article VO2 peak measured in CPET seems to reflect the true (Equation is included in full-text article.)O2 peak in adolescents with CF.