RESUMEN
PURPOSE: In acute respiratory distress syndrome (ARDS), combined high frequency oscillation (HFO) and tracheal gas insufflation (TGI) improves oxygenation versus standard HFO, likely through TGI-induced lung recruitment. Experimental data suggest that steady flows such as TGI favor the filling of the lower (i.e., subcarinal) lung. We used whole-lung computerized tomography (CT) to determine whether HFO-TGI versus HFO improves the recruitment of the lower lung, and especially of its dependent region, where loss of aeration is maximized in ARDS. METHODS: We enrolled 15 patients who had ARDS for 96 h or less, and pulmonary infiltrates in at least three chest X-ray quadrants. Patients were subjected to whole-lung CT after lung-protective conventional mechanical ventilation (CMV) and after 45 min of HFO and 45 min of HFO-TGI. HFO/HFO-TGI were employed in random order. CT scans were obtained at a continuous positive airways pressure equal to the mean tracheal pressure (P (tr)) of CMV. During HFO/HFO-TGI, mean airway pressure was titrated to the CMV P (tr) level. Gas exchange and intra-arterial pressure/heart rate were determined for each ventilatory technique. RESULTS: Regarding total lung parenchyma, HFO-TGI versus HFO and CMV resulted in a lower percentage of nonaerated lung tissue (mean ± SD, 51.4 ± 5.1% vs. 60.0 ± 2.5%, and 62.1 ± 9.0%, respectively; P≤0.04); this was due to HFO-TGI-induced recruitment of nonaerated tissue in the dependent and nondependent lower lung. HFO-TGI increased normally aerated tissue versus CMV (P=0.04) and poorly aerated tissue versus HFO and CMV (P≤0.04), and improved oxygenation versus HFO and CMV (P≤0.04). CONCLUSIONS: HFO-TGI improves oxygenation versus HFO and CMV through the recruitment of previously nonaerated lower lung units.
Asunto(s)
Ventilación de Alta Frecuencia , Insuflación/métodos , Pulmón/diagnóstico por imagen , Síndrome de Dificultad Respiratoria/terapia , Tomografía Computarizada por Rayos X , Tráquea , Adulto , Anciano , Femenino , Hemodinámica , Humanos , Pulmón/fisiopatología , Masculino , Persona de Mediana Edad , Monitoreo Fisiológico/métodos , Consumo de Oxígeno , Intercambio Gaseoso PulmonarRESUMEN
INTRODUCTION: The purpose of this study was to evaluate the patency of coronary artery bypass grafts (CABGs) while assessing the capabilities and limitations of 16-slice multidetector computed tomography. METHODS: We studied retrospectively 19 patients (13 men, 6 women), over an 18-month period. All patients had undergone CABG surgery 3 months to 7 years earlier. Two patients were examined on an emergency basis for chest pain and their CABGs were evaluated simultaneously. The number of CABGs in each patient ranged from one to three. A total of 44 grafts were assessed. All scans were performed by a 16-row multislice scanner (Toshiba Aquilion). Maximum intensity projections, multiplanar reformations, and volume rendering techniques were performed on a Vitrea workstation. All 19 patients also underwent invasive catheter coronary angiography for confirmation of their status. RESULTS: Of the 44 grafts evaluated, 26 were classified as patent, 13 as not patent, and 5 as stenotic. In the bypass grafts with stenosis > or = 50% there was a difference in the mean level of enhancement before and after the stenosis (265.38 +/- 35.82 and 178.56 +/- 9.32, respectively). Seventeen arterial and 27 venous grafts were imaged. Of the 13 non-patent grafts, 8 were venous. In 3 cases of arterial grafts the distal anastomoses were not delineated. The assessment of venous grafts was easier because of their larger diameter and lack of surrounding clips. One case of a carotid-subclavian shunt with a distal anastomosis of the left internal mammary artery to the left anterior descending branch was reported. Sensitivity, specificity, positive and negative predictive values for stenosis were evaluated. CONCLUSIONS: Multidetector computed tomography is a fast and non-invasive modality for evaluating CABG patency that is gaining acceptance as an alternative method to invasive coronary angiography. Sensitivity and specificity are determined by the available and evolving technology.