We evaluated the hypercapnia response test as a weaning outcome predictor from mechanical ventilation in patients with chronic obstructive pulmonary disease (COPD). We studied 44 COPD intubated patients considered ready for a weaning trial. The hypercapnia test was based on the modified method of re-inhalation of expired air. Through the hypercapnic test we calculated the ratio of the change in minute volume (VE) to the change in PaCO2 (ΔVE/ΔPaCO2), the change in airway occlusion pressure at 0.1 second of inspiration (P0.1) to change in PaCO2 (ΔP0.1/ΔPaCO2), the ratio of the change in P0.1 to baseline PaCO2 (ΔP0.1/PaCO2) and the ratio of the change in VE to baseline PaCO2 (ΔVE/PaCO2). Nineteen patients were successfully weaned and 25 patients failed. No differences in baseline clinical characteristics were found between the two groups. Weaning failure COPD patients had lower ΔP0.1/ΔPaCO2 (0.19±0.11 and 0.34±0.20 cm H2O/mmHg respectively, P=0.006) and lower ΔVE/ΔPaCO2 (0.21±0.15 and 0.40±0.22 l/min/mmHg respectively, P=0.002) than successfully weaned patients. The area under the receiver operating characteristic curve to discriminate weaning outcome was for the baseline PaCO2 0.81 (95% confidence interval: 0.66 to 0.91), hypercapnic PaCO2 0.76 (0.61 to 0.88), hypercapnic drive response 0.74 (0.59 to 0.86), hypercapnic ventilatory response 0.76 (0.60 to 0.87), ΔP0.1/PaCO2 0.76 (0.60 to 0.87) and for the ΔVE/PaCO2 0.81 (0.67 to 0.91). COPD patients with weaning failure have a significantly more blunted response to the hypercapnia response test than weaning success patients. This test could be useful to predict weaning failure patients if the combined values of the hypercapnic drive and hypercapnic ventilatory response were below the threshold values.

Recibido:221 Neurocirugía 2007; 18: 221-226 Resumen Objetivos. Comparar el número de vasos identificados y las velocidades e índices de pulsatilidad de los mismos mediante doppler transcraneal (DTC) y dúplex transcraneal codificado en color (DTCC) en una población de enfermos con traumatismo craneoencefálico (TCE).Material y métodos. Se estudiaron 30 enfermos ingresados por TCE en una Unidad de Cuidados Intensivos (UCI) neurocríticos. Consecutivamente se realizaron estudios mediante DTC y DTCC. Se compararon la tasa de insonación de las arterias del polígono de Willis y los parámetros hemodinámicos obtenidos.Resultados. La edad media fue de 50 años. El 67% fueron varones. En el estudio mediante DTCC se insonó la arteria carótida interna en un 95% de los casos, la arteria cerebral media (ACM) en el 95% de las ocasiones, la arteria cerebral anterior (ACA) en un 91% y la arteria cerebral posterior (ACP) en un 92% de los estudios. Mediante DTC convencional se hallaron en un 29%, 93%, 67% y 35% respectivamente. La velocidad media mediante DTCC y DTC en la ACM fue de 79 cm/ seg vs 59 cm/seg respectivamente (p<0.0001), en la ACA de 61 cm/seg vs 42 cm/seg (p<0.0001) y en la ACP de 43 cm/seg y 33 cm/seg (p<0.0001).Conclusiones. El DTCC permite un estudio hemodinámico más completo en los enfermos con TCE ingresados en la UCI. Su impacto en el pronóstico del TCE deberá determinarse en próximos estudios.PALABRAS CLAVE: Dúplex transcraneal codificado en color. Doppler transcraneal. Traumatismo craneoencefálico. Hemodinámica cerebral. Cerebral hemodynamics in patients with traumatic brain injury evaluated by transcranial doppler and transcranial color coded sonography. A comparison study Summary Objective. To compare the number of vessels identified and mean velocity and pulsatility index values obtained by transcranial doppler (TCD) and transcranial color coded sonography (TCCS) in patients with traumatic brain injury (TBI).Methods. Thirty patients suffering from TBI admitted in our neurocritical Intensive Care Unit (ICU) were studied. We performed consecutive studies by TCD and TCCS. The number of Circle of Willis vessels insonated and the hemodynamic parameters were compared.Results. Mean age was 50 years. Twenty patients were male. By using TCCS, internal carotid artery was insonated in 95%, middle cerebral artery (MCA) in 95%, anterior cerebral artery (ACA) in 91% and posterior cerebral artery (PCA) in 92% of the studies. Using conventional TCD they were insonated in 29%, 93% 67% and 35% of the studies respectively. Mean velocity values measured by CCS and TCD in MCA were 79 cm/sec vs 59 cm/sec respectively (p<0.0001), in ACA were 61 cm/sec vs 42 cm/sec (p<0.0001) and in PCA were 43 cm/sec vs 33 cm/sec (p<0.0001).Conclusion. TCCS allows a high quality hemodynamic study of TBI patients admitted to the ICU. Further studies must define its impact on outcome of TBI patients.