Desempenho de uma escala analógica visual legendada na determinação do grau de dispneia durante teste de broncoespasmo induzido por exercício em crianças e adolescentes asmáticos / Performance of a word labeled visual analog scale in determining the degree of dyspnea during exercise-induced bronchoconstriction in children and adolescents with asthma

OBJETIVO: Existe uma relação indireta entre a obstrução das vias aéreas em asma e a intensidade de falta de ar (dispneia). Uma escala visual analógica legendada de dispneia com escore de 0-3 pontos tem sido amplamente utilizada na avaliação da broncoconstrição, embora a percepção de tal obstrução seja muito variável. O objetivo deste estudo foi determinar se crianças e adolescentes são capazes de perceber a broncoconstrição aguda induzida por exercício (BAIE), bem como medir o poder discriminatório de uma escala visual analógica legendada de dispneia em relação à intensidade de BAIE. MÉTODOS: Estudo transversal com 134 crianças e adolescentes asmáticos que foram submetidos a um teste de broncoespasmo induzido por seis minutos de exercício em um cicloergômetro. A intensidade da dispneia foi determinada utilizando-se uma escala visual analógica legendada de dispneia antes de cada determinação de VEF1. A escala tem um escore de 0-3 pontos, com desenhos em uma sequência lógica variando entre "sem sintomas" e "dispneia grave". As variáveis foram determinadas no momento basal, assim como em 5, 10 e 20 minutos após o término do teste de exercício. A acurácia da escala de dispneia em detectar o grau de BAIE foi determinada através de curvas ROC para a queda de VEF1 após o exercício, usando pontos de corte de 10 por cento, 20 por cento, 30 por cento e 40 por cento. RESULTADOS: Dos pacientes selecionados, 111 completaram o estudo, e 52 (46,8 por cento) apresentaram BAIE. A área sob a curva ROC progressivamente aumentou com o aumento do grau de broncoconstrição. CONCLUSÕES: Em crianças e adolescentes asmáticos, a acurácia desta escala de dispneia melhora com o aumento do percentual de queda em VEF1 após o exercício. Entretanto, o valor preditivo da escala é subótimo quando a porcentagem de queda em VEF1é menor.

OBJECTIVE: There is an indirect relationship between airway obstruction in asthma and the intensity of breathlessness (dyspnea). A word labeled visual analog dyspnea scale with a 0-3 score has been widely used for the assessment of the degree of bronchoconstriction, although the perception of such obstruction varies considerably. The objective of this study was to determine whether children and adolescents are able to perceive acute exercise-induced bronchoconstriction (EIB), as well as to measure the discriminatory power of a word labeled visual analog dyspnea scale in relation to the intensity of the EIB. METHODS: A cross-sectional study involving 134 children and adolescents with asthma and submitted to a six-minute steady-state exercise test on a cycle ergometer. The intensity of dyspnea was determined using a word labeled visual analog dyspnea scale prior to each determination of FEV1. The scale is scored from 0 to 3, with a logical sequence of pictures, ranging from "no symptoms" to "severe dyspnea". Variables were determined at baseline, as well as at 5, 10, and 20 min after the exercise test. The accuracy of the dyspnea scale in identifying the degree of EIB was determined by means of ROC curves for the post-exercise fall in FEV1, using cut-off points of 10 percent, 20 percent, 30 percent, and 40 percent. RESULTS: Of the patients selected, 111 finished the study, and 52 (46.8 percent) presented with EIB. The area under the ROC curve increased in direct proportion to increases in the degree of bronchoconstriction. CONCLUSIONS: Among children and adolescents with asthma, the accuracy of this dyspnea scale improves as the post-exercise percentage fall in FEV1 increases. However, the predictive value of the scale is suboptimal when the percentage fall in FEV1 is lower.

Sympathetic hyperactivity in patients of bronchial asthma.

The bronchoconstricting and bronchodilating divisions of the autonomic nervous system control airway caliber of lungs. Parasympathetic hyperactivity in asthmatics eventuates in broncho-constriction. Sympathetic activity increases to combat this but fails to control bronchoconstriction due to negligible innervations of the airway smooth muscles although it causes vasoconstriction of blood vessels. In this study the effects of autonomic function test for sympathetic division were seen on selected patients and controls. Our results indicate sympathetic hyperactivity or an increased alpha-adrenergic input in asthmatics.

Effect of low temperature on tracheal smooth muscle contractile and relaxing responses evoked by electrical field stimulation

OBJECTIVE: The aim of this work was to evaluate the effect of low temperature (LT) on the contractile and relaxing responses of rat tracheas (RTs) after electrical field stimulation (EFS). METHODS: Voltage-dependent (10-60 V, 40 Hz) and frequency-dependent (0.1-60 Hz, 40 V) response curves were constructed at 37 and 18 degrees C after the activation of tracheal intramural nerves with a Grass S88 stimulator. The EFS that produced half of the maximum contractile response (ES50) at 37 or 18 degrees C was determined and considered as the dependent variable. The relaxation of pre-contracted RTs (EFS; 5 Hz, 40 V) to sodium nitroprusside (SNP; 1 x 10(-7) - 1 x 10(-3) M) isoproterenol (ISP; 1 x 10(-9) - 1 x 10(-5) M) and to 20 mM potassium chloride (KCl) after low-K+ inhibition of the Na+/K+ pump at 18 and 37 degrees C were determined. RESULTS: We found that the tracheal responses elicited by EFS at 37 and 18 degrees C were completely blocked with 1 microM atropine. LT slightly increases the voltage-dependent ES50, from 33.7 +/- 4.0 to 37.8 +/- 4.8 V, n = 5 but decreases the frequency-dependent ES50 from 19.3 +/- 4.3 to 1.0 +/- 0.28 Hz, n = 5, p < 0.05. Relaxing responses to SNP, ISP and KCl at 37 degrees C correspond to 43.5 +/- 6, 36.7 +/- 12 and 12.1 +/- 1.5 respectively. No significant tracheal relaxations were elicited at 18 degrees C. Our results indicate that in RTs, LT enhances tracheal sensitivity to EFS and decreases it in response to bronchorelaxants. The LT-dependent enhanced contractile response is observed only after a low frequency stimulation range (0.1-20 Hz), that is very close to the frequency of vagal stimuli required for inducing bronchoconstriction in vivo. Furthermore, LT abolishes the sensitivity of RTs to exogenously added bronchorelaxants (NO and ISP). In addition, LT appears to decrease the Na(+)-K+ pump activity; this effect has been associated with increased tracheal hyperreactivity in vitro. ACH appears to be the main endogenous neurotransmitter involved on neurally mediated contractile responses at 37 and 18 degrees C. CONCLUSION: Low temperature enhances the contractile response of rat tracheas in response to endogenous ACH release. The effect of LT is limited to frequencies below 20 Hz, which are within the physiological range required for bronchoconstriction. Furthermore, LT severely impairs the sensitivity of RTs to relaxant stimuli, either of endogenous of exogenous origin.

Airway Reactivity to Bronchoconstrictor and Bronchodilator: Assessment Using Thin-Section and Volumetric Three-Dimensional CT

OBJECTIVE: To determine the extent to which thin-section and volumetric three-dimensional CT can depict airway reactivity to bronchostimulator, and to assess the effect of different airway sizes on the degree of reactivity. MATERIALS AND METHODS: In eight dogs, thin-section CT scans were obtained before and after the administration of methacholine and ventolin. Cross-sectional areas of bronchi at multiple levels, as shown by axial CT, proximal airway volume as revealed by three-dimensional imaging, and peak airway pressure were mea-sured. The significance of airway change induced by methacholine and ventolin, expressed by percentage changes in cross-sectional area, proximal airway volume, and peak airway pressure was statistically evaluated, as was correlation between the degree of airway reactivity and the area of airways. RESULTS: Cross-sectional areas of the bronchi decreased significantly after the administration of methacholine, and scans obtained after a delay of 5 minutes showed that normalization was insufficient. Ventolin induced a significant increase in cross-sectional areas and an increase in proximal airway volume, while the effect of methacholine on the latter was the opposite. Peak airway pres-sure increased after the administration of methacholine, and after a 5-minute delay its level was near that of the control state. Ventolin, however, induced no significant decrease. The degree of airway reactivity did not correlate with airway size. CONCLUSION: Thin-section and volumetric spiral CT with three-dimensional reconstruction can demonstrate airway reactivity to bronchostimulator. The degree of reactivity did not correlate with airway size.

Asma inducida por ejercicio en niños / Exercise induced asthma in children

En el presente reporte se aborda el tema de la respuesta broncoconstrictora que se produce en los niños asmáticos luego de realizar ejercicio físico de cierta intensidad y duración. Se analizan los elementos etiopatogénicos reconocidos, en donde persiste como hecho central el nivel de hiperventilación alcanzado durante el ejercicio. Hasta hace poco tiempo la discusión se focalizó en la pérdida de agua y el enfriamiento del árbol bronquial producido por la hiperventilación, y en los distintos mediadores secretados producto de estos cambios locales en la vía aérea respiratoria. Actualmente el interés en los cambios vasculares ocasionados por el ejercicio en la vía aérea de sujetos hiperreactivos ocupa un lugar preponderante en la discusión de los hechos patogénicos del evento obstructivo. El conocimiento etiopatogénico del asma inducida por ejercicio (AIE), permite definir estrategias farmacológicas y no farmacológicas que son discutidas en este trabajo. Se analizan también los aspectos propios del esfuerzo físico como tipo, duración, intensidad de la actividad física o deportiva y su relación con el AIE

The role of the collagenous and elastic system fibers in modulating bronchoconstriction

The distribution and conformational changes of the fibers of the collagenous and elastic systems in guinea pig airways after a contractile agonist challenge are described. We observed a distinct pattern of behavior within the mucosal fibers during bronchoconstriction. Part of the fibers of the two systems tend to follow the epithelial invaginations towards the airway lumen, while the remaining ones seem to be attached to the internal smooth muscle. These layers of fibers in the mucosa are interconnected to one another and to the adventitial network by slender fibers. We suggest that the configuration and behavior of these fibers during bronchoconstriction may contribute to airway reopening after the contractile stimulus has ceased. The possible role of this mechanism in the pathophysiology of human asthma is discussed.

Airway response to acid instillation in esophagus in bronchial asthma.

OBJECTIVE: An increased incidence of gastroesophageal reflux has been reported in patients with bronchial asthma. We studied the pulmonary effects of acid instillation in the esophagus. METHODS: Fifteen patients with bronchial asthma and 15 healthy adults in the age group 15-50 years were studied. The control subjects were first screened for bronchial hyperreactivity by a methacholine challenge test. Patients and controls were both subjected to modified Bernstein test. Spirometry was done at baseline and after each instillation of either acid or saline. Respiratory and reflux symptoms were noted after each infusion and antacid administration. RESULTS: Five patients and one control subject had history of reflux symptoms (p < 0.05) and six patients had nocturnal asthma. There was a significant fall in FEV1/FVC after acid infusion patients; this improved significantly after antacid administration. All six patients with nocturnal asthma had respiratory signs or symptoms and had more than 20% fall in FEV1 on acid instillation in the esophagus, while none in the control group developed the same. CONCLUSIONS: Gastroesophageal reflux occurs more frequently in patients with bronchial asthma and acid instillation in the esophagus triggers bronchoconstriction.

La actividad fásica de la musculatura bronquial / Phasic activity of the bronchial musculature

Se presentan pruebas de la existencia de actividad fásica de la musculatura bronquial en el hombre y en otros mamíferos. En el animal experimental se describe la broncocontricción fásica por estimulación vagal directa y la broncodilatación fásica por vía refleja. En condiciones normales las oscilaciones basales espontáneas aumentan con otros signos de actividad simpática. Se discute el posible papel fisiológico de este tipo de actividad.