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Relationships between specific airway resistance and forced expiratory flows in asthmatic children.

Mahut B, Trinquart L, Bokov P, Le Bourgeois M, Waernessyckle S, Peiffer C, Delclaux C - PLoS ONE (2009)

Bottom Line: The earliest changes associated with airflow obstruction in asthmatic children are a proportionally greater reduction in FEF(50%) than in FEV(1) using spirometry, and an increase in specific airway resistance (sRaw) using body plethysmography.These results were further explained by a simple one-compartment lung model, which justified the shape of the observed relationships.Specific Raw is more strongly related to FEF(50%) than to FEV(1) and could be used in preschool children to predict subsequent mild airflow limitation.

View Article: PubMed Central - PubMed

Affiliation: Cabinet La Berma, Antony, France.

ABSTRACT

Background: The earliest changes associated with airflow obstruction in asthmatic children are a proportionally greater reduction in FEF(50%) than in FEV(1) using spirometry, and an increase in specific airway resistance (sRaw) using body plethysmography. Consequently, we hypothesized that sRaw could be better linked to FEF(50%) than to FEV(1). The first aim was to assess the relationships between forced expiratory flows and sRaw in a large group of asthmatic children in a transversal study. We then performed a longitudinal study in order to determine whether sRaw of preschool children could predict subsequent impairment of forced expiratory flows at school age.

Methodology: Pulmonary function tests (sRaw and forced expiratory flows) of 2193 asthmatic children were selected for a transversal analysis, while 365 children were retrospectively selected for longitudinal assessment from preschool to school age.

Principal findings: The transversal data showed that sRaw is differently related to FEF(50%) (-1/sRaw) and to FEV(1) (near linearly). These results were further explained by a simple one-compartment lung model, which justified the shape of the observed relationships. As hypothesized, sRaw correlated more strongly to FEF(50%) than to FEV(1) (r = -0.64 versus -0.39, respectively; p<0.001). In the longitudinal part of the study, sRaw at preschool age correlated with subsequent FEF(50%) (% predicted) (-0.31, 95% CI, -0.40 to -0.22), but weakly with subsequent FEV(1) (% predicted) (-0.09, 95% CI, -0.20 to 0).

Conclusion: Specific Raw is more strongly related to FEF(50%) than to FEV(1) and could be used in preschool children to predict subsequent mild airflow limitation.

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Related in: MedlinePlus

Relationships between sRaw or Raw and forced expiratory flows.Both measurements of sRaw0.5 and Raw0.5 have been obtained in a subgroup of 161 patients (La Berma Cohort). Left side: relationships between Raw (raw values) and forced expiratory flows (raw values: FEV1, upper panel, FEF50%, lower panel). Right side: relationships between sRaw (raw values) and forced expiratory flows (% predicted: FEV1, upper panel, FEF50%, lower panel). The figures show the similarity of the shape of the observed relationships that all were statistically significant (p<0.0001 for the four relationships; FEV1: linear regression; FEF50%: logarithmic regression).
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pone-0005270-g003: Relationships between sRaw or Raw and forced expiratory flows.Both measurements of sRaw0.5 and Raw0.5 have been obtained in a subgroup of 161 patients (La Berma Cohort). Left side: relationships between Raw (raw values) and forced expiratory flows (raw values: FEV1, upper panel, FEF50%, lower panel). Right side: relationships between sRaw (raw values) and forced expiratory flows (% predicted: FEV1, upper panel, FEF50%, lower panel). The figures show the similarity of the shape of the observed relationships that all were statistically significant (p<0.0001 for the four relationships; FEV1: linear regression; FEF50%: logarithmic regression).

Mentions: In order to better explain the fact that our model predicted the relationships between raw values of expiratory flows and airway resistance while we evaluated in patients the relationships between predicted values of expiratory flows and sRaw, we show the observed relationships in a subgroup of children between raw values of Raw and forced expiratory flows (FEV1, FEF50%) in figure 3 (left side). Airway resistance is inversely proportional to thoracic gas volume [5], while sRaw, corresponding to the product of Raw by thoracic gas volume, is independent of height. Predicted values of expiratory flow rates are related to the height of children and therefore on their lung volumes [15]. Consequently, we expressed the relationships between raw values of sRaw and expiratory flows expressed as percentage of their predicted values. Figure 3 shows that whatever the modality of expression of the relationships (Raw and flows expressed as raw values, or sRaw [raw value] versus flows [% predicted]) similar shapes were observed.


Relationships between specific airway resistance and forced expiratory flows in asthmatic children.

Mahut B, Trinquart L, Bokov P, Le Bourgeois M, Waernessyckle S, Peiffer C, Delclaux C - PLoS ONE (2009)

Relationships between sRaw or Raw and forced expiratory flows.Both measurements of sRaw0.5 and Raw0.5 have been obtained in a subgroup of 161 patients (La Berma Cohort). Left side: relationships between Raw (raw values) and forced expiratory flows (raw values: FEV1, upper panel, FEF50%, lower panel). Right side: relationships between sRaw (raw values) and forced expiratory flows (% predicted: FEV1, upper panel, FEF50%, lower panel). The figures show the similarity of the shape of the observed relationships that all were statistically significant (p<0.0001 for the four relationships; FEV1: linear regression; FEF50%: logarithmic regression).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2667212&req=5

pone-0005270-g003: Relationships between sRaw or Raw and forced expiratory flows.Both measurements of sRaw0.5 and Raw0.5 have been obtained in a subgroup of 161 patients (La Berma Cohort). Left side: relationships between Raw (raw values) and forced expiratory flows (raw values: FEV1, upper panel, FEF50%, lower panel). Right side: relationships between sRaw (raw values) and forced expiratory flows (% predicted: FEV1, upper panel, FEF50%, lower panel). The figures show the similarity of the shape of the observed relationships that all were statistically significant (p<0.0001 for the four relationships; FEV1: linear regression; FEF50%: logarithmic regression).
Mentions: In order to better explain the fact that our model predicted the relationships between raw values of expiratory flows and airway resistance while we evaluated in patients the relationships between predicted values of expiratory flows and sRaw, we show the observed relationships in a subgroup of children between raw values of Raw and forced expiratory flows (FEV1, FEF50%) in figure 3 (left side). Airway resistance is inversely proportional to thoracic gas volume [5], while sRaw, corresponding to the product of Raw by thoracic gas volume, is independent of height. Predicted values of expiratory flow rates are related to the height of children and therefore on their lung volumes [15]. Consequently, we expressed the relationships between raw values of sRaw and expiratory flows expressed as percentage of their predicted values. Figure 3 shows that whatever the modality of expression of the relationships (Raw and flows expressed as raw values, or sRaw [raw value] versus flows [% predicted]) similar shapes were observed.

Bottom Line: The earliest changes associated with airflow obstruction in asthmatic children are a proportionally greater reduction in FEF(50%) than in FEV(1) using spirometry, and an increase in specific airway resistance (sRaw) using body plethysmography.These results were further explained by a simple one-compartment lung model, which justified the shape of the observed relationships.Specific Raw is more strongly related to FEF(50%) than to FEV(1) and could be used in preschool children to predict subsequent mild airflow limitation.

View Article: PubMed Central - PubMed

Affiliation: Cabinet La Berma, Antony, France.

ABSTRACT

Background: The earliest changes associated with airflow obstruction in asthmatic children are a proportionally greater reduction in FEF(50%) than in FEV(1) using spirometry, and an increase in specific airway resistance (sRaw) using body plethysmography. Consequently, we hypothesized that sRaw could be better linked to FEF(50%) than to FEV(1). The first aim was to assess the relationships between forced expiratory flows and sRaw in a large group of asthmatic children in a transversal study. We then performed a longitudinal study in order to determine whether sRaw of preschool children could predict subsequent impairment of forced expiratory flows at school age.

Methodology: Pulmonary function tests (sRaw and forced expiratory flows) of 2193 asthmatic children were selected for a transversal analysis, while 365 children were retrospectively selected for longitudinal assessment from preschool to school age.

Principal findings: The transversal data showed that sRaw is differently related to FEF(50%) (-1/sRaw) and to FEV(1) (near linearly). These results were further explained by a simple one-compartment lung model, which justified the shape of the observed relationships. As hypothesized, sRaw correlated more strongly to FEF(50%) than to FEV(1) (r = -0.64 versus -0.39, respectively; p<0.001). In the longitudinal part of the study, sRaw at preschool age correlated with subsequent FEF(50%) (% predicted) (-0.31, 95% CI, -0.40 to -0.22), but weakly with subsequent FEV(1) (% predicted) (-0.09, 95% CI, -0.20 to 0).

Conclusion: Specific Raw is more strongly related to FEF(50%) than to FEV(1) and could be used in preschool children to predict subsequent mild airflow limitation.

Show MeSH
Related in: MedlinePlus