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Purpose: This case series describes the effect of home intravenous (IV) antibiotic therapy on spirometry and exercise capacity in a group of children with cystic fibrosis (CF). Methods: Outcomes from 10 children with CF who were prescribed a 14-day course of home IV antibiotics for a respiratory exacerbation are reported. All children performed spirometry and a modified shuttle test (MST) before and after 14-days of home IV therapy. Results: After 14 days, FEV1 increased by mean (± SE) 12 ± 4 % (p < 0.05) but mean MST did not improve compared to baseline. All children improved or maintained spirometry values with treatment, however, only 5 improved MST distance. Conclusion: After 14 days of home IV antibiotic therapy, a significant improvement in spirometry, but not exercise capacity, was seen in this small series of children with CF. The lack of improvement in exercise capacity for all children following home IV antibiotic therapy suggests factors other than spirometry determine exercise capacity. Identifying and investigating the factors that influence exercise capacity during home IV antibiotic therapy requires further investigation.
Antibiotic therapy, usually administered intravenously, is a requisite treatment in cystic fibrosis (CF) care and aims to reduce the consequences of respiratory infection1 and limit bacterial colonization of sputum.2 The effects of home IV antibiotic therapy have been examined in people with CF, with the primary outcome measures routinely reported being lung function, weight gain, quality of life (QOL), and clinical score.3 Secondary outcome measures have included time to readmission, financial considerations, and compliance with complementary treatments such as nutrition and chest physiotherapy.3 Although exercise capacity is considered an important measure of functional status, prognosis and quality of life for people with CF,4–6 to the best of our knowledge, this is the first reported series describing exercise capacity outcome following home IV antibiotic therapy in children or adults with CF.
This report describes the effect of home administered IV antibiotic therapy on Modified Shuttle Test (MST) and spirometry in a group of children with CF.
Ten children (7 male), mean age 12.5 years (range 7.3-16.7 years), who attended the Children's Hospital at Westmead (CHW) CF clinic and were prescribed home IV antibiotics for a respiratory exacerbation were recruited. Respiratory exacerbations were characterized by signs and symptoms including decreased pulmonary function, increased cough, breathlessness, and change in sputum production (color and/or quantity). Children were deemed suitable for home IV antibiotic therapy based on an absence of fever or need for supplemental oxygen, and adequate social support for child and family to ensure maintenance of IV access and timely administration of drugs. All decisions regarding appropriateness for home IV therapy were at the discretion of the treating physician. None of the episodes of home IV antibiotic therapy were for routine scheduled courses of intravenous therapy. The study was approved by the CHW and University of Sydney ethics committees. Parents of the participating children provided informed consent.
All children for whom data are presented in this series had previously performed the MST as a measure of exercise capacity and were proficient in performing spirometry. Only results of those children who completed testing procedures (MST and spirometry) at the clinic within 48 hours of commencement and cessation of IV antibiotic therapy are presented in this report.
Antibiotic therapy most often consisted of two antibiotics that were prescribed based on the sensitivity patterns of bacteria obtained from sputum cultures. All children in the study sample isolated pseudomonas aeruginosa. Intravenous antibiotics were planned as a 14-day course, and airway clearance techniques were reviewed by a physiotherapist prior to commencement.
Spirometry was measured by an experienced scientific officer using a Vmax 22D spirometer coupled to an Autobox V62J Body Plethysmograph and Spectra software (Sensormedics Corp., Yorba Linda, CA) in accordance with American Thoracic Society guidelines,7,8 and the results were expressed as a percentage of predicted normal.9 All participants had been performing spirometry frequently since the age of 5 years and were technically proficient in terms of the required maneuvres.
The MST was administered by a physiotherapist familiar with the test as described by Bradley et al.10 Finger probe pulse oximetry (Datex, Ohmeda TuffSat, Madison, WI) for oxygen saturation and heart rate were taken prior to, at the completion of, and after 5 minutes recovery from performance of the MST. Participants were also asked to score their rating of perceived exertion (RPE) using The Children's Hospital RPE scale (0-5 scale)11 (Figure (Figure1).1). Heart rate measurements were compared to predicted maximal values as calculated by 220-age (in years).12
Results were analyzed for within group changes using paired two-tailed student's t-tests (SPSS version 11.5.1, SPSS Inc., Chicago, IL). A p < 0.05 was considered significant. Results are expressed as mean values and standard error (SE). The relationship between spirometry and exercise capacity measured by the MST, both at the start (Time 1) and end (Time 2) of the 14-day period, as well as the relationship between the baseline MST distance and the change in MST distance, were assessed by calculating the Pearson's correlation coefficient. To assess responsiveness of the MST and spirometry to therapy, the standardized response mean (SRM) was calculated. The SRM is the ratio of change in average scores over time to the standard deviation (SD) of change (SRM = Mean score Time 2 - Mean score Time 1/SD of the change)13 and is also known as the effect size.
Individual results of all 10 children for spirometry and MST distance are presented in Table Table1.1. Group data from Time 1 to Time 2 are presented in Table Table2.2. There were statistically significant improvements in all spirometry parameters at Time 2 compared to Time 1; however, the change in MST distance was not significant (Table (Table2).2). The MST distance at Time 1 correlated significantly with Time 1 measures of %predicted FEV1 (r = 0.79, p < 0.01), FVC (r = 0.82, p < 0.005) and FEF25-75 (r = 0.72, p < 0.05). Although the increase in MST distance from Time 1 to Time 2 was not significantly different, the percentage improvement in MST distance was correlated with the percentage change in FEV1 in litres (r = 0.65; p < 0.05).
Five of the children demonstrated improvement in MST distance over the 14-day period. In these children, all had an increase in FEV1 %predicted. Of the 5 children who had a decline in MST distance, one of these was by only 10m (or one shuttle) and as such could be considered an equivalent performance to their baseline effort. Interestingly, this child also showed no change in FEV1 %predicted over the course of the treatment period. Of the 4 remaining children who had a decline in MST distance, only one of these children achieved an improvement in their FEV1 %predicted, with the remaining 3 recording an FEV1 either unchanged or within 3%predicted of their baseline measure.
The SRM for FEV1 %predicted was 0.96 and for MST distance was 0.24. Guidelines for interpreting SRM14 indicate that values 0.80, 0.50, and 0.20 are considered highly, moderately, and slightly sensitive, respectively. Being standardized scores, the SRM for MST distance can be directly compared to the SRM for %predicted FEV1. The SRM values showed FEV1 %predicted to be highly responsive to home IV antibiotic therapy, while the SRM for MST distance showed only a small response to home IV antibiotic therapy.
As an indication of the children's effort during the MST, heart rate, and RPE scores increased significantly from rest to end exercise at both Time 1 and Time 2 (p < 0.001 for all comparisons) (Table (Table33).
This small case series showed improvement in spirometry but not exercise capacity in a group of children with CF undertaking home IV antibiotic therapy. This is the first time that the effect of home IV antibiotic therapy on spirometry and exercise capacity has been reported in children. In contrast, a number of studies evaluating hospital-based IV antibiotic therapy in CF patients with varying disease severity have shown improvements in exercise capacity as measured by cycle ergometry,16 2-minute walking distance,17 3-minute step test performance,18 and the MST.15
In the current case series, the percentage improvement in MST distance was correlated with the percentage improvement in FEV1. However, it was not possible to predict the precise magnitude of improvement of the MST by the increase in FEV1 for an individual child. This could indicate that exercise capacity and spirometry, while related, are not dependent upon one another.
With only half of the children presented in this study showing improvement in MST distance, we would speculate that factors such as fatigue or reluctance of parents to allow children to participate in their normal physical activity for fear of disrupting the route of IV access may contribute to the exercise capacity outcomes seen. When receiving home IV therapy, fatigue associated with a full day at school, in addition to the demands of therapy in the home, may have contributed to a lack of improvement in mean exercise capacity. An additional consideration may be parental fatigue when accounting for work, daily family activities, and the responsibility of providing IV therapy, thus limiting available time to encourage and instigate physical activity participation.
It is difficult to determine how active the children were during the home-based treatment. Eight of the 10 children reported participation in some physical activity, such as school sport or outside games during home IV therapy; however, the intensity and duration of these activities was not recorded. Another consideration in participating in physical activity whilst undertaking home IV therapy is time of year, and thus ambient weather conditions. Inclement weather would naturally limit activity participation, and this may have coincided with the treatment period for some of our subjects. In contrast, in the studies of hospital based IV antibiotic treatment where exercise capacity was shown to increase, supervised inpatient exercise training was provided,16,20, 21 which may have contributed to the improvement. Any in-hospital training would occur in a temperature controlled environment. In future studies, activity monitors may be useful in assessing the impact of home IV antibiotic therapy on physical activity, and direct supervision of exercise may be required in order to optimize improvements in exercise capacity and control for factors in the home environment that may have led to a decline in performance in 4 of 10 children in this study.
In summary, this case series of 10 children with CF showed a significant improvement in spirometry, but inconsistent changes in exercise capacity, in response to a 14-day course of home IV antibiotic therapy. This would suggest factors in addition to lung health influence exercise capacity. Further studies are needed, with greater numbers of participants, to investigate the effect of home IV antibiotic therapy on exercise capacity. A randomized trial comparing home-based to hospital-based IV therapy in terms of exercise response, in addition to respiratory function, ideally controlled for exercise training during the IV period, would provide the best information to determine whether hospital-based and home-based treatment of CF exacerbations produce equivalent improvements in respiratory function and exercise capacity. The information presented in this case series may be of interest to therapists when preparing patients to undertake home IV therapy.