Importancia de la corrección de la KCO informada computarizada en pacientes con volumen alveolar disminuído / Importance to adjust computerized informed KCO in patients with low alveolar volume

La disminución del factor de transferencia de monóxido de carbono (TLCO) y del Volumen Alveolar (VA) no es uniforme. Los informes de los equipos computadorizados entregan un valor de KCO que no toma en cuenta este detalle.Objetivo: Realizar el cálculo de KCO a través de la corrección de Stam (J Apply Physiol 1994) y compararlas con las informadas por el software de un equipo de laboratorio pulmonar computadorizado reconocido (Collins).Material y Método: Fueron incluídos pacientes consecutivos derivados al Laboratorio Pulmonar de la Unidad para realizar una prueba de TLCO por enfermedad intersticial pulmonar entre Enero y Junio de 2008. Se realizaron las pruebas según recomendacionesATS/ERS por el método de respiración única y con el método de toma de muestra de Ogilvie. Se analizó la KCO según lo informa el software del equipo Collins Plus/SQL System (1995Warren Collins), y luego se lo recalculó corregida según el cálculo de Stam (J Apply Physiol 1994). Se incluyó en este análisis si tenían <80% del volumen alveolar predicho. Resultados: Fueron evaluados 15 pacientes (media edad: 57.5 ± 12.9 años, sexo femenino 66.7%) con enfermedad intersticial.La media de VA fue 3.5±0.8 L(64.3±11.6%). La media de KCO informada a través del software fue 4.2± 1.3ml/min/mmHg/L. La media de KCO corregida fue 3.7 ± 1.2ml/min/mmHg/L (Δ 11.8±3.8, rango: 6.8%-21.1%). Se observó una relación lineal y negativa entre el %VA y el delta de KCO corregida/informada (r2= -0.99). La elección de diferentes tablas de valores normales de VA altera hasta 12% el valor de la misma, pero la KCO corregida se altera en grado mínimo (3%). Conclusiones: Cuando el VA está disminuído, se debe realizar la corrección del informe computadorizado de la KCO, porque se observa una diferencia promedio del 12%, sobreestimando la real KCO del paciente. Otros factores, como la tabla de valores predictivos de VA, influencia muy poco la corrección de KCO.

The decrease of the Transfer Factor of the Lung for Carbon Monoxide (TLCO) and the Alveolar Volume (VA) is not uniform. Software of lung computed machine informs the carbon monoxide transfer coefficient TLCO/VA (KCO) by calculating the ratio without adjusting for that assumption. Objectives: To calculate KCO using a correction by the Stam´s equation (J Apply Physiol1994), to compare the corrected KCO with the result informed by the software of Collins lung laboratory equipment, and to evaluate the impact of using different predictive tables of VA in the estimates of KCO. Materials: Consecutive patients with intersticial lung disease who attended the LungLaboratory to perform the TLCO between January and June 2008 were included in the study. TLCO was performed according to ATS/ERS recommendations by the single-breathand Ogilvie methods. KCO was calculated by the software of Collins Plus/SQL System (1995 Warren Collins), and then recalculated by Stam´s equation. Only patients withless than 80% of VA predictive value were included. Results: 15 patients with interstitial lung disease were evaluated (age: 57.53 ± 12.93 years old, female: 66.66%). The mean VA was 3.55 ±0.83 L (64.33 ±11.56%) and the mean KCO informed by software was 4.17 ±1.31 ml/min/mmHg/L. The corrected KCO was 3.76 ±1.33 ml/min/mmHg/L(Δ 11.84 ±3.84, range: 6.82%-21.1%). It was observed a negative and lineal relation between %VA and Δ KCO corrected/informed (R2= -0.99). The election of different tables of VA normal values distorts up to12% the individualvalues, but the corrected KCO is little modified (3%). Conclusion: When the VA is reduced, the correction of the KCO must be performed, to avoid on average a 12% overestimate. Other factors such as the election of VA predictive tables have little influence on the KCO correction.

Importance of Carbon Monoxide Transfer Coefficient (KCO) Interpretation in Patients with Airflow Limitation / 결핵및호흡기질환

BACKGROUND: The single-breath carbon monoxide diffusion capacity (DLCO) and the per unit alveolar volume (KCO; DLCO/VA) gave discordant values when there was an abnormal alveolar volume (VA). However, the clinical significance of the discordant values in patients with airflow limitation has not been examined. This study investigated the DLCO and KCO changes after improving the airflow limitation. METHOD: The baseline DLCO and KCO with lung volume were measured in patients with an airflow obstruction. The effective alveolar volume was measured using the single-breath CH4 dilution method. The patients divided into two groups according to the baseline values: (1) increased KCO in comparison with the DLCO (high discordance) (2) decreased or not increased KCO in comparison with the DLCO (low discordance). The diffusion capacity and lung volume were measured after treatment. RESULTS: There was no significant difference in the baseline lung volumes including the FEV1 and FVC between the two groups. The FEV1 and FVC were significantly increased in the high discordance group compared with the low discordance group after treating the airflow limitation. The DLCO and alveolar volume were significant higher in the high discordance group compared with the low discordance group while the TLC was not. CONCLUSION: The discordance between the DLCO and KCO could be translated into an airflow reversibility in patients with an airflow limitation