The Clinical Study On Spontaneous Breathing Trial With The United Mode Of PSV+CPAP

SBT(spontaneous breathing trial) is defined as that the ventilated patients have been accepeted the spontaneous breathing mode such as T tube or ventilatory support of low levels, then the doctor evaluate the ability to breathe independently and predict the likelihood of successful weaning through the dynamic observation of the the short time (30min-2h). At present, spontaneous breathing trials include T tube, low-level (3-5cmH2O) CPAP and low-level (5-7 cmH2O) PSV. There are no uniform standards which of three tirals is best and how long is appropriate. Chronic obstructive pulmonary disease (COPD) patients with weak base respiratory function are prone to occur respiratory musle fatigue and weaning difficulties more frequently than patients with acute respiratory failure, so COPD patients should take the appropriate mode and the longer time. For patients with acute respiratory failure who haven't had underlying lung diseases, muscle strength and endurance can be restored through a short break. Therefore, there are differences in the selection of mode and duration for two types of patients. Some studies found that 30minSBT or 2hSBT has no effect on the result of weaning for patients with acute respiratory failure but chronic respiratory failure patients should select 2hSBT which can help improve the success rate of weaning. After years of clinical practice, in order to equip more secure and more efficient weaning for critical patients with mechanical ventilation, we have developed the uinted mode of PSV (5-8cmH2O)+CPAP (3-5cmH2O). Now we found its advantage and it is suitable for a larger disease group. There has never been reported about the united mode of PSV+CPAP though literature search.Purpose:To investigate the safe and effective SBT which is suitable for different types of ventilated critical patients and to provide the clinical data of mode and duration of SBT on programmed weaning though researching the effect of the different mode and duration on the success rate of weaning and reintubation rate(without 48 hours).Methods:242 ventilated patients were inrolled in this study who choosed in ICU department of the second clinical hospital of Jilin University. All patients were divided two groups:acute respiratory failure group without COPD and chronic respiratory failure group with COPD. All patients were randomly selected one of modes(PSV, CPAP and PSV+CPAP) and one of duration(30min or 2h) when the cause of mechanical ventilation had been wiped out or improved and screening test on weaning had met the stamdard. The clinical indicators such as awareness, breathing and circulation were recorded every 15min in the course of the trials; blood indices were also tested in laboratory; arterial blood gas analysis was conducted before and after SBT; in end of the trial, whether extubation or not was assessed by the above results. The success rate of weaning and reintubation rate(within 48 hours) were recorded. Datas are analyzed by SPSS 15.0 software packet. The quantitative data presents as mean±standard (χ±s) deviation and multiple groups means were compared with single factor analysis of variance and differences of measurement data in group were compared with paired t test. The statistic dates were analyzed with Chi-square tests. p>0.05 defined as no statistically significant difference while p<0.05 defined as a statistically significant difference.Results:1. The success rate of weaning in chronic respiratory failure group with COPD was obviously lower than that in acute respiratory failure group without COPD, there were significant differences (p<0.05).2. Reintubation rate(within 48 hours) in chronic respiratory failure group with COPD was obviously higher than that in acute respiratory failure group without COPD, there were significant differences (p<0.05).3. There was no significant effect on the success rate of weaning between PSV+CPAP and the single mode of PSV or CPAP in the same time in chronic respiratory failure group with COPD.4. in chronic respiratory failure group with COPD, the success rate of weaning in 2hSBT group was obviously higher than that in 30minSBT group (p<0.05).5. In acute respiratory failure group without COPD, different duration of SBT has no significant effect on success rate of weaning (p>0.05).6. The different mode and duration of SBT has no significant effect on reintubation rate(within 48 hours) in two groups of patients (p>0.05).7. In 2h SBT duration of acute respiratory failure group without COPD, there was no significant effect on pH, PaO2and PaCO2 between 30min and 2h (p>0.05), while while P(A-a)O2 of 30 min was clearly lower than that of 2h(p<0.05).Discussion:SBT is the best way to judge the balance between respiratory muscle strength and workload. In recent years, domestic and foreign scholars have provided insights into a deeper understanding on spontaneous breathing trial. This study was undertaken to investigate the safe and effective SBT which is suitable for different types of critical patients with mechanical ventilation and to provide the clinical data of mode and duration of SBT on programmed weaning though researching the effect of the different mode and time on the success rate of weaning and reintubation rate(without 48 hours).Perren et al randomly selected ventilated patients with coma, COPD, heart failure, pneumonia and etc in ICU who were conducted with low level PSV as the SBT, then made the comparative research between the 30min group and the 2h group. The result showed that there was no significant effect on the success rate of weaning, reintubation rate(without 48 hours), average hospital stay and mortality in ICU between the two groups, but in that study Perren did not classify the different kinds of disease. In chronic respiratory failure group with COPD of this study, the success rate of weaning in 2hSBT group was obviously higher than that in 30minSBT group. This is mainly due to poor lung function and decreased muscle strength and endurance significantly of COPD patients. It is necessary to have a longer time SBT to assess the capaticy of spontaneous breathing. For long-term ventilator-dependent patients with decreased respiratory muscle strength particulary, even 2h is not enough to judge the capaticy of spontaneous breathing, so weaning is very difficult. This requires training respiratory muscle and gradually extending the duration of SBT to wean. The results indicated that there were no significant differences on success rate of weaning in acute respiratory failure subgroup without COPD. This is mainly because patients in this group haven't underlying lung diseases respiratory and muscle strength and endurance can be restored through a short break,30 min is enough to judge the capaticy of spontaneous breathing. Thus, different duration and mode of SBT has no significant effect on result of weaning in acute respiratory failure group without COPD.In this experiment, there was no significant effect on pH, PaO2 and PaCO2 between 30min subgroup and 2h subgroup, while P(A-a)O2 of 30min subgroup was clearly lower than that of 2h subgroup in 2h SBT duration of acute respiratory failure group without COPD. P(A-a)O2 is the integrative index to the capacity of the intake of oxygen which blood carries from the lungs and reflect the efficiency of external respiration, so it can judges the level of difficulty that oxygen enters the blood from the lung. Any reason which can cause the proportion of ventilation perfusion ratio, diffusing capacity disorder of alveolar and diversion increased can give rise to P(A-a)O2. Patients overcome not only resistance of airway and elastance but also the resistance of pipe and such the extra power to do work during SBT, so these factors increase respiratory muscle load and P(A-a)O2.SBT can be conducted using one of several approaches, including T tube, low-level(3-5cmH2O) CPAP and low-level(5-8cmH2O) PSV. Most studies suggest that three kinds of SBT were no statistical differences on success rate of weaning and extubation tate. Maic I et al found that in difficult weaning patients (APACHE II>20) PSV could improve the success rate of extubation and decrease weaning time, the total mechanical ventilation time and ICU hospital stays compared with T tube though randomized controlled study which inrolled 260 patients. Overall, CPAP and PSV could be better than T tube. To compensate for shortcomings of CPAP, PSV and such single model SBT, We have developed the uinted mode of PSV(5-8cmH2O)+CPAP(3-5cmH2O) in order to equip more secure and more efficient weaning for critical patients with mechanical ventilation in the many years of clinical practice. ICU patients who have respiratory failure with a number of reasons are usually in critical and complicated condition. The united mode of PSV+CPAP supplies the appropriate support on the premise of continuous positive airway pressure, thus it can overcome the shortcomings of the single mode and increase the success rate of weaning. The final results of this study suggest that different modes and durations of SBT had no significant difference on success rate of weaning for critical ventilated patients with or without COPD. The united mode of PSV+CPAP wasn't superior to PSV and CPAP, but it was as safe and effective as the single mode.The results indicated that reintubation rate(within 48 hours) in chronic respiratory failure group with COPD was obviously higher than that in acute respiratory failure group without COPD, but there was no statistical difference in reintubation rate(without 48 hours) among different groups of the same disease. This is because reintubation rate(without 48 hours) isn't responsile for the mode and the durtiong of SBT but the state of disease,.Weaning with SBT is safe and reliable. The united mode of PSV+CPAP can overcome the shortcomings of the single mode and may is suit for a larger disease group espically for the ctitical ventilated patients in ICU. Limited time and datas may have an impact on the results.To define the clinical value of PSV+CPAP, further study is needed to gather more statistics.Conclusion:1. Different durations of SBT are indicated for ctitical ventilat-ed patients with different diseases.2h of SBT is appropriate for the chronic respiratory failure patients with COPD and 30min of SBT is just for the acute respiratory failure patients without COPD; 2. The united mode of PSV+CPAP is as effective and safe as PSV and CPAP and such the single mode in the ventilated patients, even the united mode may be superior to the single mode; 3. Different modes and durations of SBT have no significant difference on reintubation rate(without 48 hours). Reintubation rate(without 48 hours) is largely relevant to the existing physical illness such as COPD and the disease development; 4. Whether or not the united mode of PSV+CPAP is more suitable for various critical patients of mechanical ventilation still require a large sample of the prospective randomized controlled study.