Biomedical subjects
Publications and source records attributed to Kim G Nielsen.
sRaw measurements are feasible in children from 2 years of age. sRaw allows clinical monitoring and research during this critical period of growth and development in early life. sRaw measurements promise to bridge the gap of lung function measurements between infancy and school age.
FOT may hold the promise of improving the diagnosis of airway obstruction, but may be even better in quantifying the magnitude of airway reversibility and hyper-reactivity, helping in the adjustment of therapy, and monitoring disease progression in young children.
Validated methods for lung function measurements in young children are lacking. Plethysmographic measurement of specific airway resistance (sRaw) provides such a method applicable from 2 years of age. sRaw gauges airway resistance from the measurements of the pressure changes driving the airflow during tidal breathing. These measurements require no active cooperation and are therefore feasible in children from 2 years of age. The within-observer and between-observer variability of sRaw in young children compare favorably with alternative methods. Reference values are available for sRaw and have allowed discrimination of young children with respiratory disease. Bronchial hyperresponsiveness can be determined with acceptable short-term and long-term repeatability and provides good discrimination between asthmatics and healthy young children. The effects of the major antiasthmatic therapies have also been documented by this technique, and sRaw has recently been used in longitudinal studies of young children with chronic pulmonary diseases. Future developments should provide improved algorithms for thermal correction of the respired volumes and adapt the equipment to the special needs of young children. This article reviews the method, and proposes a protocol and criteria for quality assurance for assessment of sRaw in preschool children from 2 years of age. sRaw measurements offers a method for clinical monitoring and research during this critical period of growth and development early in life.
BACKGROUND: Exercise-induced bronchoconstriction (EIB) is of particular importance in children with asthma. It is an important measure of asthma control and should be monitored by exercise testing. However, exercise testing puts a large demand on health-care resources and is therefore not widely used in routine monitoring of pediatric asthma control. The fractional concentration of exhaled nitric oxide (FeNO) also reflects uncontrolled asthma. We hypothesized that FeNO may be used for prescreening of asthmatic children to exclude those with good asthma control unlikely to have EIB, thereby reducing the need for exercise testing. OBJECTIVE: The aim of this study was to estimate the value of FeNO as a predictor of EIB in asthmatic children. METHODS: Stable outpatient asthmatic school children performed standard exercise challenge tests and measurement of FeNO. RESULTS: FeNO and response to a standardized submaximal exercise test on the treadmill were measured in 111 school children with asthma. EIB could be excluded with a probability of 90% in asthmatic children with FeNO levels < 20 parts per billion (ppb) without current inhaled corticosteroid treatment, and < 12 ppb in children with current inhaled corticosteroid treatment. CONCLUSION: Measurement of FeNO is a simple, and time- and resource-efficient tool that may be used to screen for EIB testing and therefore optimizes the resources for exercise testing in pediatric asthma monitoring.
UNLABELLED: Cold air challenge (CACh) has been shown to discriminate between children with asthma and healthy young children. Hyperventilation with dry room-temperature air is a simplified alternative. We compared responsiveness in young children with asthma between two standardized, single-step protocols: dry air challenge (DACh) performed as 6 minutes of eucapnic hyperventilation with dry room-temperature air and CACh as 4 minutes of hyperventilation. Response was measured as specific airway resistance by whole-body plethysmography and expressed as change from baseline in numbers of within-subject SDs (SDw). The challenge sequence was randomly assigned. A comparator challenge was performed 1 hour later if the first challenge gave a change of 3 SDw or more. Forty 2- to 5-year-old children with asthma were included. Responsiveness to cold versus dry air showed significant, but weak, correlation (r(2) = 0.34, p < 0.0001), but responsiveness to CACh exceeded DACh (7.6 vs. 5.4 SDw, p < 0.02). CACh seemed to induce reduction in response to the following DACh (p < 0.01), whereas no such reduction was seen after DACh. CONCLUSION: Responsiveness to CACh exceeded responsiveness to DACh, and CACh seemed to induce refractoriness in contrast to DACh, probably because of the additional stimulus from airway cooling. This finding suggests CACh as the preferred method of challenge.
In a 4-year prospective study, we evaluated specific airway resistance (sRaw) by whole-body plethysmography, respiratory resistance by the interrupter technique, and respiratory resistance and reactance at 5 Hz by the impulse oscillation technique combined with measurement of responsiveness to bronchodilators and cold air in 30 children (mean [range] age 5.7 [2 to 8] years) with cystic fibrosis (CF). Spirometry was done at school age. Mean sRaw was consistently abnormal: the mean z score (SD) was 2.52 (2.02) (p < 0.001) at the start and was unchanged 36 months later at 2.74 (2.02). Mean z score (SD) for FEV(1) at first satisfactory measurement, at a mean age (range) of 6.1 (4.9-7.5) years was -1.2 (1.2) and was further reduced to -1.85 (1.2) 4 years from inclusion at a mean age (range) of 9.9 (6.8-12) years. Neither respiratory resistance by the interrupter technique nor the impulse oscillation technique demonstrated consistent abnormal levels. Patients with CF as a group did not differ from healthy subjects in responsiveness to bronchodilators and cold air. sRaw may be a useful tool in CF during early childhood. Reduced lung function was documented from consistently abnormal levels of sRaw and FEV1 during the study. Bronchodilator responsiveness and response to cold air challenge were normal.