Altered breathing mechanics and ventilatory response during exercise in children born extremely preterm

Abstract

BackgroundExtreme preterm birth confers risk of long-term impairments in lung function and exercise capacity. There are limited data on the factors contributing to exercise limitation following extreme preterm birth. This study examined respiratory mechanics and ventilatory response during exercise in a large cohort of children born extremely preterm (EP).MethodsThis cohort study included children 8–12 years of age who were born EP (≤28 weeks gestation) between 1997 and 2004 and treated in a large regionalised neonatal intensive care unit in western Canada. EP children were divided into no/mild bronchopulmonary dysplasia (BPD) (ie, supplementary oxygen or ventilation ceased before 36 weeks gestational age; n=53) and moderate/severe BPD (ie, continued supplementary oxygen or ventilation at 36 weeks gestational age; n=50). Age-matched control children (n=65) were born at full term. All children attempted lung function and cardiopulmonary exercise testing measurements.ResultsCompared with control children, EP children had lower airway flows and diffusion capacity but preserved total lung capacity. Children with moderate/severe BPD had evidence of gas trapping relative to other groups. The mean difference in exercise capacity (as measured by oxygen uptake (VO2)% predicted) in children with moderate/severe BPD was −18±5% and −14±5.0% below children with no/mild BPD and control children, respectively. Children with moderate/severe BPD demonstrated a potentiated ventilatory response and greater prevalence of expiratory flow limitation during exercise compared with other groups. Resting lung function did not correlate with exercise capacity.ConclusionsExpiratory flow limitation and an exaggerated ventilatory response contribute to respiratory limitation to exercise in children born EP with moderate/severe BPD.

Increased prevalence of expiratory flow limitation during exercise in children with bronchopulmonary dysplasia

“…This study shows that preterm children with a neonatal classification of BPD have reduced minute ventilation due to a markedly decreased V T with an increased breathing frequency at peak exercise. These observations are consistent with a rapid and shallow breathing pattern and are in keeping with previous exercise studies in children born preterm [ 10 , 12 , 16 , 17 ]. We hypothesised that this rapid and shallow breathing pattern would be associated with an increased prevalence of EFL.…”

“…Our study confirms that EFL is highly prevalent in children with BPD [ 12 ]. Our observations of the prevalence of EFL in preterm children with (53%) and without (26%) BPD are similar to the prevalence reported by M ac L ean et al [ 12 ] (47% and 33% in children with and without BPD, respectively). Our study adds to the current literature in that we report this prevalence over a wider gestational age (up to 32 weeks gestational age compared with <29 weeks gestational age).…”

Increased prevalence of expiratory flow limitation during exercise in children with bronchopulmonary dysplasia

“…This study shows that preterm children with a neonatal classification of BPD have reduced minute ventilation due to a markedly decreased V T with an increased breathing frequency at peak exercise. These observations are consistent with a rapid and shallow breathing pattern and are in keeping with previous exercise studies in children born preterm [ 10 , 12 , 16 , 17 ]. We hypothesised that this rapid and shallow breathing pattern would be associated with an increased prevalence of EFL.…”

“…Our study confirms that EFL is highly prevalent in children with BPD [ 12 ]. Our observations of the prevalence of EFL in preterm children with (53%) and without (26%) BPD are similar to the prevalence reported by M ac L ean et al [ 12 ] (47% and 33% in children with and without BPD, respectively). Our study adds to the current literature in that we report this prevalence over a wider gestational age (up to 32 weeks gestational age compared with <29 weeks gestational age).…”

Exercise Capacity and Ventilatory Response in Children Who Were Born Preterm, With and Without Bronchopulmonary Dysplasia

“…Even though reports of aerobic capacity in the literature remain conflicting [28], several irregularities in the ventilatory and gas exchange responses to exercise have been consistently reported in ex-preterm subjects (with and without BPD) [29], similar to the ones reported in the present study. These findings include higher respiratory rates [30], lower tidal volumes [31], or both [32][33][34], and, similar to our study, an increased VE/VCO 2 relationship [31,35]. Several explanations have been proposed for these findings, such as reduced lung compliance [33], inspiratory muscle dysfunction [30], and increased alveolar dead space [35].…”

Effects of Pre-Term Birth on the Cardio-Respiratory Responses to Hypoxic Exercise in Children

“…Exercise capacity was similar between prematurely-born children and their full-term counterparts under normoxic conditions. This is in line with previous research conducted in children [8,9], although an impaired exercise capacity with prematurity in normoxia has often been observed in adults [5,22]. A key novelty of this study was the translation of these comparisons to normobaric hypoxic conditions.…”

Increased prevalence of expiratory flow limitation during exercise in children with bronchopulmonary dysplasia

“…This study shows that preterm children with a neonatal classification of BPD have reduced minute ventilation due to a markedly decreased V T with an increased breathing frequency at peak exercise. These observations are consistent with a rapid and shallow breathing pattern and are in keeping with previous exercise studies in children born preterm [ 10 , 12 , 16 , 17 ]. We hypothesised that this rapid and shallow breathing pattern would be associated with an increased prevalence of EFL.…”

“…Our study confirms that EFL is highly prevalent in children with BPD [ 12 ]. Our observations of the prevalence of EFL in preterm children with (53%) and without (26%) BPD are similar to the prevalence reported by M ac L ean et al [ 12 ] (47% and 33% in children with and without BPD, respectively). Our study adds to the current literature in that we report this prevalence over a wider gestational age (up to 32 weeks gestational age compared with <29 weeks gestational age).…”

Exercise Capacity and Ventilatory Response in Children Who Were Born Preterm, With and Without Bronchopulmonary Dysplasia

“…Even though reports of aerobic capacity in the literature remain conflicting [28], several irregularities in the ventilatory and gas exchange responses to exercise have been consistently reported in ex-preterm subjects (with and without BPD) [29], similar to the ones reported in the present study. These findings include higher respiratory rates [30], lower tidal volumes [31], or both [32][33][34], and, similar to our study, an increased VE/VCO 2 relationship [31,35]. Several explanations have been proposed for these findings, such as reduced lung compliance [33], inspiratory muscle dysfunction [30], and increased alveolar dead space [35].…”

Effects of Pre-Term Birth on the Cardio-Respiratory Responses to Hypoxic Exercise in Children

“…Exercise capacity was similar between prematurely-born children and their full-term counterparts under normoxic conditions. This is in line with previous research conducted in children [8,9], although an impaired exercise capacity with prematurity in normoxia has often been observed in adults [5,22]. A key novelty of this study was the translation of these comparisons to normobaric hypoxic conditions.…”

Increased prevalence of expiratory flow limitation during exercise in children with bronchopulmonary dysplasia

“…This study shows that preterm children with a neonatal classification of BPD have reduced minute ventilation due to a markedly decreased V T with an increased breathing frequency at peak exercise. These observations are consistent with a rapid and shallow breathing pattern and are in keeping with previous exercise studies in children born preterm [ 10 , 12 , 16 , 17 ]. We hypothesised that this rapid and shallow breathing pattern would be associated with an increased prevalence of EFL.…”

“…Our study confirms that EFL is highly prevalent in children with BPD [ 12 ]. Our observations of the prevalence of EFL in preterm children with (53%) and without (26%) BPD are similar to the prevalence reported by M ac L ean et al [ 12 ] (47% and 33% in children with and without BPD, respectively). Our study adds to the current literature in that we report this prevalence over a wider gestational age (up to 32 weeks gestational age compared with <29 weeks gestational age).…”

Exercise Capacity and Ventilatory Response in Children Who Were Born Preterm, With and Without Bronchopulmonary Dysplasia

“…Even though reports of aerobic capacity in the literature remain conflicting [28], several irregularities in the ventilatory and gas exchange responses to exercise have been consistently reported in ex-preterm subjects (with and without BPD) [29], similar to the ones reported in the present study. These findings include higher respiratory rates [30], lower tidal volumes [31], or both [32][33][34], and, similar to our study, an increased VE/VCO 2 relationship [31,35]. Several explanations have been proposed for these findings, such as reduced lung compliance [33], inspiratory muscle dysfunction [30], and increased alveolar dead space [35].…”

Effects of Pre-Term Birth on the Cardio-Respiratory Responses to Hypoxic Exercise in Children

“…Exercise capacity was similar between prematurely-born children and their full-term counterparts under normoxic conditions. This is in line with previous research conducted in children [8,9], although an impaired exercise capacity with prematurity in normoxia has often been observed in adults [5,22]. A key novelty of this study was the translation of these comparisons to normobaric hypoxic conditions.…”