A Clinical Study On The Recovery Time Of Heart Rate After Sputum Suction To Predict Weaning From Mechanical Ventilation

ObjectiveTo evaluate the significance of recovery time of heart rate after sputum suction as a weaning predictor in patients who were on mechanical ventilation.MethodsThe study was conducted from August2013to February2014in the intensive care unit and the intensive care unit of cardiothoracic surgery in General Hospital, Tianjin Medical University.138patients who were on mechanical ventilation were randomly selected. Record the general condition (sexuality, age, the cause of respiratory failure, the operation, mechanical ventilation mode and so on).After the primary disease was cured, the ventilator support condition was gradually reduced. When the oxygen concentration decreased to0.40and the respiratory rate to1bpm; A30minutes SBT was taken with T-piece after the criteria of weaning screening test was meted. Before conducting the SBT, we record the change of heart rate and the recovery time of heart rate (trecovery time) in the patients who were conducted sputum suction. The requirements of sputum suction were the time of1min, the depth of30cm and the pressure of150mmHg.In the same time, we measured the BNP and determined left ventricular ejection fraction (LVEF) by doppler echocardiography before SBT. Compared the general conditions in patients who were successful in weaning with the patients who failed in weaning. And observe the relation of trecovery time and LVEF. The value of trecovery time and BNP were evaluated by calculating the area under the receiver operator characteristic (ROC) curves in all patients. The area under the ROC curves (AUC) of trecovery time was compared with the BNP.Result1.118patients were successfully weaning from mechanical ventilation while20patients failed. There was no significant difference between the two groups in average of age,ratio of male and female,pH,PaO2,PaCO2,MBP,HRbasic, APACHE Ⅱ.(P>0.05).2. The trecovery time and BNP were negatively correlated with LVEF, r=-0.400, P<0.01and r=-0.561, P<0.01respectively.3. The two groups has no significant difference in the change of HR after sputum suction(P>0.05). trecovery time of fail group was longer than the successful group (P<0.01), trecovery time>267.5s, as a threshold of predicted unsuccessful weaning, Sensitivity is95%, Specificity is85.6%. The AUC of trecovery time was0.935±0.20,95%confidence interval (CI) was0.895-0.9754. BNP>150pg/ml, as a threshold of predicted unsuccessful weaning, Sensitivity is85%, Specificity is76.3%. The AUC of BNP was0.843±0.055,95%confidence interval (CI) was0.735-0.9505. There was no significant difference in comparing the AUC of trecovery time with the AUC of BNP(P>0.05).ConclusionsThe recovery time of heart rate after sputum suction was negatively correlated with LVEF, and may reflect the cardiac function; As a simple, easy to measure, cheap prediction index, it is likely to improve the success rate of weaning.