Ecuaciones de referencia para informe de espirometrías. ¿Será tiempo de adoptar las ecuaciones de la Global Initiative for Lung Function? / Reference equations for spirometry values. Should be time for adopting the Global Lung Function Initiative equations?

Las guías ATS/ERS recomiendan utilizar valores de referencia nacionales para la interpretación de la espirometría. En 2014 se publicaron valores de referencia en población general chilena adulta, que difieren de los de Knudson actualmente en uso. Sin embargo, la mayoría de los laboratorios de función pulmonar siguen utilizando estas últimas ecuaciones. En 2012 se publicaron las ecuaciones multi-étnicas de la Global Lung Function Initiative (GLI) a fin de estandarizar mundialmente la interpretación de los exámenes de función pulmonar Nuestro objetivo fue comparar la concordancia de los informes espirométricos utilizando las ecuaciones más usadas en Chile versus las GLI. Métodos: Se comparó la concordancia en interpretación del patrón espirométrico (normal, obstructivo y restrictivo) y el grado de alteración, entre GLI con Gutiérrez 2014, con Knudson, y con NHANES III según las recomendaciones de la Sociedad Chilena de Enfermedades Respiratorias, a través del coeficiente de concordancia Kappa (K). Se estudiaron 315 sujetos mayores de 40 años (55% mujeres, edad: 59,3 ± 9,2 años), fumadores o ex fumadores, sanos o con EPOC, sometidos a una espirometría con broncodilatador como parte de un reconocimiento respiratorio. Se graficaron las diferencias utilizando el método de Bland-Altman. Resultados: La concordancia para patrón entre GLI con Gutiérrez 2014, con Knudson y con NHANES III fue buena (K = 0,73; 0,71 y 0,77 respectivamente), al igual que para patrón y grado de alteración (K = 0,68; 0,67 y 0,76 respectivamente). Conclusiones: Encontramos una buena concordancia entre las ecuaciones más usadas en Chile y las de GLI, en una muestra que incluyó adultos, fumadores, ex fumadores sanos y enfermos.

ATS/ERS recommend the use of national reference values for the interpretation of spirometry. Reference values were published (2014) in general adult Chilean population, which are different from those of Knudson currently in use. However, most pulmonary function laboratories continue to use these latter equations. Multi-ethnic Global Lung Function Initiative (GLI) equations were published (2012) in order to standardize the interpretation of pulmonary function tests worldwide. Our objective was to evaluate the agreement in the spirometric reports between the most used equations in Chile with those from GLI. Methods: We compared the agreement in the interpretation of the spirometric pattern (normal, obstructive and restrictive) and the degree of alteration between GLI with Gutiérrez 2014, with Knudson and with NHANES III according to recommendations of the Chilean Society of Respiratory Diseases, through the Kappa concordance coefficient (K). The sample correspond to 315 adults over 40 years of age (55% women, 59.3 ± 9.2 years-old), smokers or ex-smokers, healthy or with COPD, who underwent spirometry with a bronchodilator as part of a respiratory check-up. Differences were plotted using the Bland-Altman method. Results: agreement for pattern between GLI with Gutiérrez 2014, with Knudson and with NHANES III was good (K = 0.73, 0.71 and 0.77 respectively) and also was good for the pattern and degree of alteration (K = 0.68, 0.67 and 0.76 respectively). Conclusions: We found a good agreement between the equations most used in Chile and those from the GLI, for a sample that includes subjects with and without lung disease, smokers and ex-smokers.

Estandarización de la prueba de capacidad de difusión de monóxido de carbono: Chilean Society of Respiratory Diseases guidelines / Standardization of the single-breath diffusing capacity

Since its introduction in clinical practice carbon monoxide diffusing capacity (DLCO), has been widely used in respiratory diseases, being the most common test utilized after spirometry in pulmonary function laboratories. It represents the entire diffusion process including transport through the alveolar-capillary barrier and hemoglobin binding. Its high affinity with hemoglobin and its near zero partial pressure in plasma determines that CO transfer depends specifically on diffusion. Common respiratory and cardiac diseases such as emphysema, interstitial lung diseases, lung damage by drugs, arterial pulmonary hypertension and cardiac failure, among others show a reduced DLCO. Recent theories considering red blood cells as the main factor involved in resistance to diffusion, suggest that DLCO may reflect the status of lung microcirculation. For example, in cardiac failure, DLCO does not improve in parallel with lung volume, even with cardiac stabilization or cardiac transplantation. Despite its wide utilization, DLCO measurement presents standardization and reproducibility difficulties. International guidelines and task forces recommend using representative values of the target population. After analyzing the available information a group of experts from the Pulmonary Function Commission of the Chilean Society of Respiratory Diseases has proposed guidelines for measurement techniques, quality control, equipment calibration and interpretation of results.

Desde la introducción en la práctica clínica de la prueba de difusión con monóxido de carbono (CO) a mediados del siglo pasado, su utilización ha sido ampliamente difundida en la evaluación de diversas enfermedades respiratorias, de hecho se le considera la prueba más utilizada luego de la espirometría. Desde el punto de vista conceptual aporta información global de todo el proceso de difusión, que incluye el paso a través de la barrera alvéolo capilar y su unión con la hemoglobina. Gracias a la elevada afinidad del CO por la hemoglobina y a la particularidad de que la presión parcial de CO en el plasma es prácticamente cero, la transferencia del CO depende sólo de su difusión. Patologías respiratorias y cardíacas habituales como el enfisema pulmonar, las enfermedades pulmonares intersticiales, el compromiso pulmonar por drogas neumotóxicas, la hipertensión arterial pulmonar y la insuficiencia cardíaca congestiva, entre otras, cursan con disminución de la capacidad de difusión de CO (DLCO). Un nuevo desafío plantean las hipótesis recientes que postulan que la resistencia a la difusión del monóxido de carbono depende principalmente del glóbulo rojo, por lo que ésta podría consistir en una representación de la microcirculación. Como ejemplo, en la insuficiencia cardíaca congestiva, el deterioro de la DLCO no mejora en conjunto con los volúmenes pulmonares, ni cuando estos pacientes se estabilizan o se trasplantan. Si bien se trata de una técnica de laboratorio ampliamente utilizada, aún presenta problemas de estandarización y reproducibilidad. En este documento de consenso, un grupo de estudio de la Comisión de Función Pulmonar de la Sociedad Chilena de Enfermedades Respiratorias, ha efectuado una revisión de este método, con las correspondientes proposiciones de técnicas de medición, control de calidad, calibración e interpretación.

Efeito da terminação precoce da expiração nos parâmetros espirométricos em crianças pré-escolares saudáveis / Early termination of exhalation: effect on spirometric parameters in healthy preschool children

OBJETIVO: Avaliar a aceitabilidade e a reprodutibilidade da espirometria em pré-escolares; estimar o tamanho do efeito da terminação precoce da expiração (TPE) nos valores de CVF, VEF1 e VEF0,5; e avaliar a validade do VEF0,5 em curvas com TPE. MÉTODOS: Espirometrias foram obtidas em 240 pré-escolares saudáveis, selecionados por amostragem simples. Três grupos foram formados com base na melhor curva de cada criança de acordo com o término da expiração: sem TPE (sTPE); com TPE e fluxo < 10 por cento do maior PFE (TPE<10); e com TPE e fluxo > 10 por cento do maior PFE (TPE>10). Foram comparadas a reprodutibilidade da CVF, VEF1 e VEF0,5 nos três grupos. Foi avaliado o efeito da TPE em CVF, VEF1 e VEF0,5. RESULTADOS: Das 240 crianças testadas, 112 (46.5 por cento) realizaram curvas aceitáveis para todos os parâmetros - 82 (34,0 por cento) no grupo sTPE e 30 (12,5 por cento) no grupo TPE<10. Em 64 (27,0 por cento) no grupo TPE>10, as curvas foram aceitáveis apenas para VEF0,5, aumentando para 73,0 por cento a proporção de crianças com VEF0,5 válido. Não houve diferenças significantes nas médias dos parâmetros avaliados entre os grupos sTPE e TPE<10. CONCLUSÕES: Manobras com TPE e fluxo < 10 por cento do maior PFE são válidas. Em indivíduos com fluxo > 10 por cento do maior PFE, essas manobras são válidas somente para VEF0,5.

OBJECTIVE: To evaluate the acceptability and reproducibility of spirometry in preschool children; to estimate the effect size of early termination of exhalation (ETE) on FVC, FEV1 and FEV0.5; and to evaluate the validity of FEV0.5 in curves with ETE. METHODS: Spirometric data were obtained from 240 healthy preschool children, who were selected by simple sampling. On the basis of the best curve from each child according to the end of exhalation, three groups were formed: no ETE (nETE); ETE and flow < 10 percent of the highest PEF (ETE<10); and ETE and flow > 10 percent of the highest PEF value (ETE>10). The reproducibility of FVC, FEV1 and FEV0.5 was compared among the three groups. The effect of ETE on FVC, FEV1, and FEV0.5 was assessed. RESULTS: Of the 240 children tested, 112 (46.5 percent)-82 (34.0 percent) of those in the nETE group and 30 (12.5 percent) of those in the ETE<10 group-had acceptable curves for all the parameters. In 64 (27.0 percent) of those in the ETE>10 group, the curves were acceptable only for FEV0.5, increasing the proportion of children with valid FEV0.5 to 73.0 percent. There were no significant differences between the nETE and ETE<10 groups in terms of the mean values of the parameters assessed. CONCLUSIONS: Maneuvers with ETE and flow < 10 percent of the highest PEF are valid. In individuals with a flow > 10 percent of the highest PEF value, these maneuvers are only valid for FEV0.5.

Forced oscillation technique in the detection of smoking-induced respiratory alterations: diagnostic accuracy and comparison with spirometry

INTRODUCTION: Detection of smoking effects is of utmost importance in the prevention of cigarette-induced chronic airway obstruction. The forced oscillation technique offers a simple and detailed approach to investigate the mechanical properties of the respiratory system. However, there have been no data concerning the use of the forced oscillation technique to evaluate respiratory mechanics in groups with different degrees of tobacco consumption. OBJECTIVES: (1) to evaluate the ability of the forced oscillation technique to detect smoking-induced respiratory alterations, with special emphasis on early alterations; and (2) to compare the diagnostic accuracy of the forced oscillation technique and spirometric parameters. METHODS: One hundred and seventy subjects were divided into five groups according to the number of pack-years smoked: four groups of smokers classified as <20, 20-39, 40-59, and >60 pack-years and a control group. The four groups of smokers were compared with the control group using receiver operating characteristic (ROC) curves. RESULTS: The early adverse effects of smoking in the group with <20 pack-years were adequately detected by forced oscillation technique parameters. In this group, the comparisons of the ROC curves showed significantly better diagnostic accuracy (p<0.01) for forced oscillation technique parameters. On the other hand, in groups of 20-39, 40-59, and >60 pack-years, the diagnostic performance of the forced oscillation technique was similar to that observed with spirometry. CONCLUSIONS: This study revealed that forced oscillation technique parameters were able to detect early smoking-induced respiratory involvement when pathologic changes are still potentially reversible. These findings support the use of the forced oscillation technique as a versatile clinical diagnostic tool in helping with chronic obstructive lung disease prevention, diagnosis, and treatment.

Influence of the ageing process on the resistive and reactive properties of the respiratory system

INTRODUCTION: In an increasingly old society, the study of the respiratory system changes and new techniques dedicated to older patients are of interest in physiologic studies as well as in the diagnosis of respiratory diseases. OBJECTIVES: (1) To investigate the impact of ageing on the resistive and reactive properties of the respiratory system, and (2) to compare the easiness of accomplishment of spirometry and forced oscillation for assessing lung function. METHODS: We conducted a cross-sectional study in which forced oscillation was used to investigate respiratory system resistive and reactive properties, while spirometry was used as a reference test to evaluate 80 normal subjects aged between 20 and 86 years. A questionnaire was used to evaluate the easiness of accomplishment of spirometry and forced oscillation. RESULTS: There was a significant increase in the respiratory system resonance frequency (p<0.003) and a reduction in the mean reactance (p<0.004) with increasing age. Respiratory system resistance and dynamic compliance were not related to the ageing process. The easiness of accomplishment of forced oscillation measurements was greater than that of spirometry. This result was particularly relevant in subjects over 70 years old (p<0.05). CONCLUSIONS: Respiratory system resistance and dynamic compliance are not modified with ageing. On the other hand, respiratory system homogeneity decreases during the ageing process. Forced oscillation is easy to perform and provides information complementary to spirometry. This technique may be a promising alternative and/or complement to other conventional exams used to evaluate older people who are unable to adequately perform spirometric tests.

Comparação de valores de PFE em uma amostra da população da cidade de São Carlos, São Paulo, com valores de referência / Comparison between PEF values obtained from a population sample in the city of São Carlos, Brazil, and reference values

OBJETIVO: Comparar os valores de referência para PFE sugeridos por outros autores em 1963, 1989 e 2001 (para populações nos EUA, na Inglaterra e em Cuba, respectivamente) com os valores de PFE coletados de uma amostra da população da cidade de São Carlos (SP), verificando se há concordância entre estes. MÉTODOS: Participaram do estudo 243 indivíduos (123 mulheres; 120 homens) na faixa etária entre 20 e 70 anos. A coleta de PFE foi realizada com o indivíduo em pé, utilizando um clipe nasal, através de medidor de PFE portátil. Os valores obtidos foram comparados com os previstos, utilizando-se o teste de Friedman e post hoc de Dunn (p < 0,05). RESULTADOS: Observou-se diferença significativa para todas as faixas etárias, em ambos os sexos, quanto aos valores previstos em 1989; o mesmo ocorreu para as faixas etárias 20-30, 31-40 anos, em ambos os sexos, e 61-70 anos para mulheres quanto aos valores de 2001, assim como para a faixa etária 20-30 anos para homens quanto aos valores previstos em 1963. CONCLUSÕES: Os valores previstos em 1963 são aceitáveis para uma população de indivíduos com as mesmas características da amostra estudada, exceto para os homens de 20-30 anos. Nosso estudo provou ter grande relevância devido ao tamanho da amostra estudada quando comparado ao do trabalho realizado em 1963. A maioria dos valores previstos em 1989 e 2001 superestimou os valores de PFE obtidos nesse estudo, indicando sua inadequação para a população estudada.

OBJECTIVE: To compare the reference values for PEF suggested by other authors in 1963, 1989 and 2001 (for populations in the USA, England and Cuba, respectively) with those obtained from a population sample in the city of São Carlos, Brazil, and to determine whether there is concordance among them. METHODS: A total of 243 volunteers (123 females and 120 males; 20-70 years of age) participated in the study. The PEF measurements were performed with the volunteer standing, using a nose clip, by means of a portable peak flow meter. These measurements were compared with the reference values using the Friedman test and Dunn's post-hoc test (p < 0.05). RESULTS: Significant differences were found in all age groups from both genders regarding the values predicted in 1989; the same occurred in the 20-30 and 31-40 age groups (both genders), as well as in the 61-70 age group (females only), regarding those predicted in 2001, as well as in the 20-30 age group (males only) regarding those predicted in 1963. CONCLUSIONS: The values predicted in 1963 are appropriate for a population of individuals with the same characteristics as the study sample, except for males in the 20-30 age group. Our study is relevant due to the fact that our sample was larger than that evaluated in the 1963 study. The majority of the values predicted in 1989 and 2001 overestimated the PFE values obtained in our study, proving to be inappropriate for the population studied.

Prueba de caminata de seis minutos / Guidelines for the six-minute walk test

The six-minute walk test has been shown as a very useful tool in the functional assessment of patients with chronic respiratory diseases enclosing patients with pulmonary hypertension. Methodological standardization of this test is fundamental for interpreting its results, as well as for using it in the short and long-term clinical follow up of our patients. The purpose of these guidelines is justly to spread out in our country the proper way to perform this useful test. In this context, indications, contraindications, limitations, security measures and detailed instructions about how to carry out, how to report and how to interpret the 6 minute walk test are described in these guidelines.

La prueba de caminata de 6 minutos ha demostrado ser una herramienta muy útil en la evaluación funcional de los pacientes con enfermedades respiratorias crónicas, incluyendo pacientes con hipertensión pulmonar. Para su correcta interpretación y uso clínico en el seguimiento de pacientes, es fundamental estandarizar la técnica. El propósito de este instructivo es justamente difundir a nivel nacional, la manera de efectuar esta técnica en forma correcta. En este contexto, este instructivo describe las indicaciones, contraindicaciones, limitaciones, medidas de seguridad y entrega detalles sobre la ejecución, informe e interpretación de la prueba de caminata de 6 minutos.

Determinación de valores de referencia para volumenes pulmonares en escolares y adolescentes / Determination of a reference value for lung volume in schoolchildren and adolescent

El uso de ecuaciones de referencia adecuadas para determinar y predecir valores normales es un aspecto importante para optimizar la utilidad clínica de las pruebas de función pulmonar. Debido a la diversidad de ecuaciones existentes, cada laboratorio de función pulmonar debe saber elegir las apropiadas para su población de estudio. Estas ecuaciones deberían ser consistentes y representativas, deberían derivar de estudios que utilicen procedimientos y equipos estandarizados y por supuesto, deberían estar validadas. Existen muchos factores determinantes de la función pulmonar en un niño o adolescente, como son: la estatura, sexo y edad; y recientemente se ha publicado evidencia que sugiere el rol de la influencia racial, ambiental y de los potenciales efectos de la pubertad. En esta revisión se brinda una revisión de estos factores y de su efecto en la determinación de volúmenes pulmonares en niños escolares y adolescente.

Determinação da eficiência do VEF6 como substituto da CVF na triagem diagnóstica da doença pulmonar obstrutiva crônica através da comparação entre as relações VEF1/CVF e VEF1/VEF6 / Determination of the efficacy of FEV6 as a surrogate for FVC in the diagnostic screening for chronic obstructive pulmonary disease through the comparison of FEV1/FVC and FEV1/FEV6 ratios

OBJETIVO: Determinar a eficácia do uso do volume expiratório forçado nos primeiros seis segundos (VEF6) como substituto da capacidade vital forçada (CVF) na triagem diagnóstica da doença pulmonar obstrutiva crônica (DPOC) através da comparação entre as medidas da relação VEF1/CVF e as medidas da relação VEF1/VEF6. MÉTODOS: No ano de 2003, durante o Dia Mundial da DPOC, realizamos uma campanha de triagem diagnóstica da DPOC. Os participantes da campanha respondiam ao questionário clínico do projeto Global Initiative for -Obstructive Lung Disease e aqueles que apresentavam pelo menos três respostas positivas submetiam-se a espirometria. RESULTADOS: Um total de 134 indivíduos respondeu positivamente a três questões e realizou espirometria. Destes, 59 foram excluídos: 45 por serem não fumantes e 14 pelo fato de seus exames não obedecerem aos critérios da American Thoracic Society para espirometria de qualidade. O número de resultados abaixo de 70 por cento foi similar para VEF1/CVF e para VEF1/VEF6. A sensibilidade de VEF1/VEF6 para o diagnóstico de obstrução de vias aéreas definida por VEF1/CVF abaixo de 70 por cento foi de 92 por cento e a especificidade foi de 99 por cento. O valor preditivo positivo foi de 100 por cento e o valor preditivo negativo foi de 98 por cento. O teste de correlação de Kendall mostrou r = 0,99 (p < 0,0001). O teste t para amostras pareadas mostrou correlação negativa: t = -5,93 (p < 0,0001). CONCLUSÃO: A relação VEF1/VEF6 se mostrou eficaz para uso na triagem diagnóstica da DPOC. Existe uma forte relação entre VEF1/CVF e VEF1/VEF6.

OBJECTIVE: To determine the efficacy of using forced expiratory volume in six seconds (FEV6) as a surrogate for forced vital capacity (FVC) in the diagnostic screening for chronic obstructive pulmonary disease (COPD) by comparing FEV1/FVC ratios with FEV1/FEV6 ratios. METHODS: In November of 2003, on World COPD Day, we conducted a campaign of diagnostic screening for COPD. The participants completed the clinical questionnaire of the Global Initiative for Obstructive Lung Disease, and those who responded affirmatively to at least three questions underwent spirometry. RESULTS: A total of 134 individuals responded to three questions affirmatively and underwent spirometry. Of those, 59 were excluded: 45 for being non-smokers and 14 due to the fact that their tests did not meet the American Thoracic Society criteria for satisfactory spirometry. The number of tests in which the FEV1/FEV6 ratio was below 70 percent was similar to that found for the FEV1/FVC ratio. The sensitivity of FEV1/FEV6 in diagnosing airway obstruction (defined as FEV1/FVC below 70 percent) was 92 percent, and its specificity was 99 percent. The positive predictive value was 100 percent, and the negative predictive value was 98 percent. The Kendall correlation test revealed r = 0.99 (p < 0.0001). The t-test for paired samples revealed a negative correlation: t = -5.93 (p < 0.0001). CONCLUSION: The FEV1/FEV6 proved efficient for use in the diagnostic screening for COPD. There is a strong correlation between FEV1/FVC and FEV1/FEV6.

Evaluación del rendimiento de la espirometría en preescolares sanos con estandarización adaptada a este grupo etario / Assessment of spirometry efficiency in healthy preschool children using a modified standardization suited for this group of age

Spirometry has been standardized to be carried out in children not younger than 6 years-old. However, several studies have shown that it is feasible to obtain acceptable and reproducible forced expiratory maneuvers in preschool children by adjusting the requirements to that group of age. Our aims were to evaluate the spirometry efficiency in preschool children using a modified standardization, and to propose new acceptability and reproducibility criteria for spirometry in this group of age. Eigthy healthy children (2.5 to 5.9 years old) were randomly selected through an informed consent followed by a survey and a physical examination. Each child was invited to do as many as possible forced expiratory curves in a Jaegger spirometer during a period not longer than 15 minutes. Curves with a clear peak expiratory flow (PEF), with a rapid rise and without a sudden ending of the expiratory flow from a point greater than 20 percent of PEF, were considered acceptable.The mean age of the 80 children was 4.7 years old and 31 of them were males Three children did not want to do the test. From the 77 that did the test, 72 (93.5 percent) were able to get at least two acceptable curves. These 72 children correspond to 85.7 percent of children younger than 4 years old, 90.3 percent of children from 4 to 5 y.o and 100 percent of children from 5 to 6 y.o. We concluded that spirometry is a feasible and efficient test in preschool children if the standardization requirements are suited to them. We propose to use a new set of acceptability and reproducibility criteria for spirometry in this group of age.

La espirometría se ha estandarizado para ser efectuada en niños de 6 ó más años de edad. Sin embargo, diversos estudios han demostrado que es factible obtener maniobras de expiración forzada aceptables y reproducibles en preescolares, si se ajustan los requerimientos de la estandarización a este grupo etáreo. Nuestros objetivos fueron evaluar el rendimiento de la espirometría en preescolares usando una estandarización modificada y proponer nuevos criterios de aceptabilidad y reproducibilidad para la espirometría en este grupo etáreo. Se seleccionaron aleatoriamente a través de un consentimiento informado y luego por una encuesta y examen físico 80 preescolares sanos de 2,5 a 5,9 años de edad. Cada niño fue invitado a realizar en un espirómetro Jaegger el máximo número de maniobras de espiración forzada que pudiera en un lapso no mayor de 15 min. Se consideraron aceptables las curvas con un trazado nítido del flujo espiratorio máximo (PEF), con elevación rápida y sin una terminación súbita del flujo espiratorio desde un nivel mayor al 20 por ciento del PEF. La edad promedio de los 80 niños fue 4,7 años y 31 eran de sexo masculino. Tres niños no quisieron efectuar la prueba. De los 77 que realizaron la prueba 72 (93,5 por ciento) lograron realizar al menos dos curvas aceptables. Estos 72 niños correspondieron al 85,7 por ciento de niños menores de 4 años de edad, al 90,3 por ciento de niños entre 4 y 5 años y al 100 por ciento de los niños entre 5 y 6 años de edad. Concluimos que si los requerimientos de estandarización son adaptados para la edad preescolar, la espirometría es una prueba factible y eficiente en preescolares. Proponemos usar un nuevo conjunto de criterios de aceptabilidad y reproducibilidad para la espirometría en este grupo etáreo.

Evaluating the suitability of prediction equations for lung function in Indian children: a practical approach.

OBJECTIVE: Although several prediction equations to evaluate peak expiratory flow rate (PEFR) of Indian children are available in literature, clinicians and researchers need to make a logical choice of which equation to use as reference. The aim was to demonstrate a practical approach to making such a logical choice by using prediction equations on our study population. METHODS: Eighteen linear regression equations generated on Indian children were chosen from available literature. PEFR measured on a Wright peak flow meter on 81 boys and 60 girls, aged between 8 and 13 years, was compared with the predicted values obtained from the equations. Data was systematically analyzed for the extent of over-estimation and under-estimation, correlation between the predicted and measured values and bias and limits of agreement using Bland-Altman plots. RESULTS: The correlation between observed and predicted values using the eighteen equations ranged between 0.616 and 0.797 (for all P < 0.001). The Bland-Altman plots indicated that for all but three equations in boys and three equations in girls, lower measured values of PEFR were associated with higher predicted values. A final choice of a reference prediction equation was based on a combination of factors which included a high correlation between actual and predicted PEFR values, the bias of the estimate, the limits of agreement and the extent to which equations over or under-estimated PEFR. CONCLUSION: A practical approach to evaluate the applicability of prediction equations on an independent data set has been demonstrated.

Evaluación de diferentes valores de referencia espirométricos para el diagnóstico de alteración restrictiva en población chilena / Assessment of different spirometric reference values for diagnosing restrictive impairment in chilean population

In 1988, the Chilean Respiratory Society decided to get national spirometric reference values (SRV), because those used at that time (Knudson et al) underestimated the values in our population. Since then, and using national SRV, it has been observed an increase of the positive false restrictive impairment diagnoses. Our aim was to analyse the probability of making a restrictive impairment diagnosis, according to different spirometric reference values, using the total lung capacity (TLC) measurement as a gold standard. Patients and Methods: We analysed the spirometries from male and female patients older than 59 y.o., in whom lung volumes by helium dilution, had been measured concurrently in our laboratory during 2004. Restrictive impairment was substantiated (confirmed) if TLC was lower than its theoretical value (European Community) minus 1,64À RSD (standard deviation of the residual). Spirometries from the same patients were analysed with different SRV and several statistical indicators of diagnostic tests were calculated. Results: 91 patients (mean age: 72 y.o. ranging from 60 to 89) were assessed. We confirmed a restrictive impairment in 35 of them (38 percent). Using national SRV, sensitivity (S) was 86 percent, specificity (E) 59 percent and the post-test probability (PPT) 57 percent. Using NHANES III SRV, S was 54 percent, E was 91 percent and PPT 79 percent Using Knudson SRV S was 49 percent, E 93 percent and PPT 81 percent, while by using Platino study SRV, S was of 49 percent, E was 77 percent and PPT 57 percent. Conclusion: Similarly to previous reports, we have found an important difference in the probability of diagnosing restriction in our population, according to the SRV used

A finales de los años 80 se planteó la necesidad de disponer de valores de referencia espirométricos (VRE) nacionales, ya que los utilizados en esa época (Knudson) subestimaban los valores en nuestra población. Posteriormente, al utilizar VRE nacionales, se ha observado un aumento de los diagnósticos de restricción falsos positivos. El objetivo de este trabajo fue analizar la probabilidad de hacer el diagnóstico de restricción a través de la espirometría, según diferentes valores de referencia utilizando como gold standard la medición de la capacidad pulmonar total (CPT). Material y Método: Se analizaron las espirometrías de pacientes mayores de 59 años, estudiados además con volúmenes pulmonares por técnica de dilución de helio durante el año 2004. Como criterio de restricción se utilizó el valor inferior a CPT teórica menos 1,64À RSD (desviación standard del residuo) con respecto a los valores teóricos de la comunidad europea. Se analizaron las espirometrías de los mismos pacientes con diferentes VRE y se calcularon diferentes indicadores estadísticos de pruebas diagnósticas. Resultados: Se evaluaron 91 casos con edad promedio de 72 años (rango 60 a 89) encontrando verdadera restricción en 35 de ellos (38 por ciento). Al utilizar VRE nacionales la sensibilidad (S) fue de 86 por ciento, la especificidad (E) de 59 por ciento y la probabilidad postest (PPT) de 57 por ciento. Con NHANES III la S fue de 54 por ciento, la E de 91 por ciento y la PPT de 79 por ciento.Con Knudson la S fue de 49 por ciento, la E de 93 por ciento y la PPT de 81 por ciento mientras que con Platino la S fue de 49 por ciento, la E de 77 por ciento y la PPT de 57 por ciento. Se concluye que existe una gran diferencia en la probabilidad de diagnosticar restricción según el VRE utilizado, de manera similar a lo publicado por otros autores.

Los riesgos a la salud en los laboratorios de función respiratoria y su prevención / Health risks in the respiratory funtion laboratories an theis prevention

Los riesgos de la realización de pruebas de función respiratoria son bajos para el paciente y para el personal, pero existen y se deben conocer para poderlos prevenir. Incluyen los riesgos comunes a otros laboratorios como: descargas eléctricas, incendios o condiciones climáticas inapropiadas para trabajar. También hay algunos riesgos particulares como son los derivados por el uso de cilindros de alta presión, la inhalación de aerosoles tóxicos o infecciosos y la transmisión de infecciones por vía sanguínea. Los riegos al paciente son pequeños y escasos cuando se siguen normas de seguridad aceptadas.

Prevención y tratamiento en asma de alto riesgo / Prevention and treatment in asthma of hight danger

Ha existido un menosprecio, respecto a la gravedad atribuible al Asma Bronquial y en determinados momentos se han divulgado más los efectos secundarios de la medicación que el peligro de las crisis severas. En el afán de reducir los efectos indeseables de cierta medicación, se usan dosis insuficientes o inadecuadas. La reacción tisular de tipo tardío, predispone a la hiperreactividad bronquial y las crisis severas. Los grupos de riesgo estan constituidos por: 1) los individuos que han superado una crisis de Mal Asmático; 2) asmáticos lábiles que experimentan grandes variaciones circadianas y padecen asma nocturno; 3) broncolábiles con ataques fulminantes e insuficiencia ventilatoria súbita extrema, muchas veces con pocos síntomas en período intercrisis; 4) los que han requerido asistencia de urgencia. La evaluación de una crisis debe tomar en cuenta parámetros objetivos. El seguimiento debe ser prolijo y cercano, las indicaciones terapéuticas precisas y detalladas, y la medicación mantenerse por períodos prolongados. Deben darse pautas claras de autoayuda y explicitarse la necesidad de requerir auxilio ante determinadas circunstancias. Se enumeran claros criterios, para seleccionar medicamentos y procedimientos terapéuticos, de acuerdo a la gravedad del asma y se advierte sobre trastornos de conducta en determinados individuos. Se insiste sobre la necesidad de: medidas de higiene ambiental para eliminar alergenos o irritantes, el control de la patología infecciosa agregada, el control de toda medicación que por cualquier causa reciba el enfermo y por último se resalta el valor de la inmunoterapia para disminuir los riesgos