应用无创通气作为急性呼吸衰竭患者撤机方法的研究

目的评价接受机械通气治疗的急性呼吸衰竭(ARF)患者应用无创通气(NIV)撤机的临床效果。方法58例ARF患者经气管插管机械通气治疗48h后病情好转,尚未完全满足撤机条件时随机分为两组,NIV组:拔管立即给予NIV作为撤机方法;有创压力支持通气(IPSV)组:继续经人工气道给予PSV实施撤机。观察比较两组患者动脉血气变化、并发症发生率、机械通气时间和住院时间、再插管率和病死率。结果NIV组有创通气时间显著短于IPSV组(P<0.05),两组总的通气支持时间相似。NIV组呼吸机相关性肺炎(VAP)的发生率显著低于IPSV组(P<0.05),住院时间显著短于IPSV组(P<0.05)。两组再插管率和病死率相似。结论NIV用于接受机械通气的ARF患者撤机可缩短有创通气时间和住院时间,降低VAP的发生率。     

无创通气在慢性阻塞性肺疾病并呼吸衰竭患者撤机中的应用

目的探讨无创通气(NIV)在慢性阻塞性肺疾病急性加重(AECOPD)并呼吸衰竭中作为撤机方式的应用价值。方法接受气管插管有创通气的38例AECOPD并呼吸衰竭患者在病情有所好转,但尚未完全达到拔管撤机标准时随机分为两组:NIV组:拔管后立即经面罩给予NIV进行过渡撤机;有创正压通气(IPPV)组:继续经气管导管给予压力支持通气(PSV)实施过渡撤机。观察两组患者的动脉血气变化、机械通气时间、住院时间、再插管率和病死率。结果拔管后应用NIV患者的pH,PaCO2和PaO2与应用IPPV患者无明显差异(P>0.05)。NIV组患者VAP的发生率明显低于IPPV组(P<0.05),NIV组的有创通气时间和住院时间明显短于IPPV组(P<0.05),病死率低于IPPV组(P<0.05)。结论应用NIV作为正在接受有创通气治疗的AECOPD并呼吸衰竭患者的撤机方式是可行的,NIV可降低VAP的发生率,缩短有创通气时间和住院时间,降低病死率。     

Noninvasive ventilation to prevent respiratory failure after extubation in high-risk patients

OBJECTIVE: Compared with standard medical therapy (SMT), noninvasive ventilation (NIV) does not reduce the need for reintubation in unselected patients who develop respiratory failure after extubation. The goal of this study was to assess whether early application of NIV, immediately after extubation, is effective in preventing postextubation respiratory failure in an at-risk population. DESIGN: Multiple-center, randomized controlled study. SETTING: Multiple hospitals. PATIENTS: Ninety-seven consecutive patients with similar baseline characteristics, requiring >48 hrs of mechanical ventilation and considered at risk of developing postextubation respiratory failure (i.e., patients who had hypercapnia, congestive heart failure, ineffective cough and excessive tracheobronchial secretions, more than one failure of a weaning trial, more than one comorbid condition, and upper airway obstruction). INTERVENTIONS: After a successful weaning trial, the patients were randomized to receive NIV for > or = 8 hrs a day in the first 48 hrs or SMT. Primary outcome was the need for reintubation according to standardized criteria. Secondary outcomes were intensive care unit and hospital mortality, as well as time spent in the intensive care unit and in hospital. MEASUREMENTS AND MAIN RESULTS: Compared with the SMT group, the NIV group had a lower rate of reintubation (four of 48 vs. 12 of 49; p = .027). The need for reintubation was associated with a higher risk of mortality (p < .01). The use of NIV resulted in a reduction of risk of intensive care unit mortality (-10%, p < .01), mediated by the reduction for the need of reintubation. CONCLUSIONS: NIV was more effective than SMT in preventing postextubation respiratory failure in a population considered at risk of developing this complication.     

Early prediction of successful weaning during pressure support ventilation in chronic obstructive pulmonary disease patients.

OBJECTIVE: The aim of this study was to examine variables for early prediction of successful weaning in chronic obstructive pulmonary disease (COPD) patients during pressure support ventilation weaning. DESIGN: Thirteen COPD patients were prospectively studied to compare the respiratory pattern (inspiratory time, expiratory time, total breath cycle duration, tidal volume, respiratory rate, minute ventilation), the respiratory drive (airway occlusion pressure at 0.1 sec, tidal volume/inspiratory time), and blood gases after 30 mins of pressure support weaning. SETTING: The study was performed in the 20-bed General Critical Care Unit of the Rome "La Sapienza" University Hospital. PATIENTS: We evaluated 13 consecutive COPD patients fulfilling the standard weaning criteria (including clinical status, blood gases, forced vital capacity, maximum inspiratory pressure, and spontaneous respiratory rate after a 30-min T-piece trial) in which we compared respiratory pattern, respiratory drive, and blood gases after 30 mins of pressure support weaning. MEASUREMENTS AND MAIN RESULTS: After 30 mins of pressure support ventilation weaning (pressure support level 20 cm H2O), we measured respiratory pattern (airway pressure and airflow tracing), airway occlusion pressure at 0.1 sec (occluding the inspiratory line during expiration with a rubber balloon), tidal volume/inspiratory time, maximal inspiratory pressure, and blood gases. According to the result of the weaning trial, the patients were divided into two groups (not weaned and weaned), and the statistical difference between the evaluated variables was analyzed in weaned and not weaned groups. We did not observe a significant difference in breathing pattern data and arterial blood gases between weaned and not weaned patients. By contrast, airway occlusion pressure at 0.1 sec and maximum inspiratory pressure measured after 30 mins of weaning trial appeared significantly (p less than .001) different in patients in whom the weaning trial succeeded or failed. Considering maximum inspiratory pressure, we could not separate weaned from not weaned patients, while all patients showing values of airway occlusion pressure at 0.1 sec less than 4.5 cm H2O were easily weaned. CONCLUSIONS: This study confirms that conventional weaning criteria are often inadequate in predicting successful weaning of COPD patients, while airway occlusion pressure at 0.1 sec during the first phase of pressure support ventilation weaning can represent a good weaning predictor.     

Weaning older patients from long-term mechanical ventilation: a pilot study.

BACKGROUND: As older persons in the intensive care unit increasingly require long-term mechanical ventilation, accurate indications of readiness for weaning from ventilatory support are needed to avoid premature extubation. OBJECTIVE: To describe temporal changes in pulmonary and systemic variables in older adults receiving long-term mechanical ventilation. METHODS: After 3 days of unsuccessful attempts at weaning from ventilatory support, 10 trauma and surgical patients more than 60 years old were monitored daily. Previously reported predictors of the duration of mechanical ventilation and weaning outcome were measured, including hemodynamic and gas exchange variables, oxygen cost of breathing, and the score on the Burns Weaning Assessment Program. RESULTS: The 6 patients who could be weaned from ventilatory support were younger (median age, 71.5 years) than the 4 patients who could not be weaned (median age, 80 years). Patients who could be weaned were ready for weaning by day 11 of their stay in the intensive care unit and required an additional 5.5 days of mechanical ventilation; those who could not be weaned were not ready for weaning until day 17. All patients initially had increases in oxygen consumption during weaning; those who were successfully weaned had decreases before extubation. Respiratory rate, maximal inspiratory pressure, the ratio of Pao2 to fraction of inspired oxygen, and mean arterial pressure were higher in patients who could be weaned, and oxygen cost of breathing and central venous pressure were lower CONCLUSION: Further study of weaning in older adults is warranted.     

The significance of hypoxemia with low inspired O2 fraction before extubation

Arterial and transcutaneous O2 (PtcO2) and CO2 (PtcCO2) tensions, arterial O2 saturations (SaO2) and P50 values were measured in 47 patients before extubation. In order to unmask ventilation to perfusion (VA/Q) inequality, all variables were obtained without CPAP and with FIO2 of 0.40 as well as with CPAP of 5 cm H2O and FIO2 of 0.40, 0.35, 0.30, 0.25, and 0.21. Eighty to 90% of the patients had PaO2/FIO2 lower than 300 torr and no significant difference in PaO2 or SaO2 was found between those who were successfully extubated (group S, n = 38) and those who required reintubation (group R, n = 9). On the other hand, the patients in group R had significantly lower P50 values, and their PtcO2 values decreased at a greater incline with the lowering of FIO2 than those in group S. Pulmonary dysfunction does not solely explain the need for reintubation in group R. It is obvious that arterial hypoxemia may become more dangerous when the patient has a low P50, anemia, or hypermetabolism. Because PtcO2 seems to uncover these factors, it is a valuable method for predicting the patient's condition before extubation.     

Weaning from mechanical ventilation in pediatric intensive care patients

Objective: The development of weaning predictors in mechanically ventilated children has not been sufficiently investigated. The purpose of this study was to evaluate the accuracy of some weaning indices in predicting weaning failure. Design: Prospective, interventional study. Setting: University-affiliated children's hospital with a 19-bed intensive care unit. Patients: 84 consecutive infants and children requiring mechanical ventilation for at least 48 h and judged ready to wean by their primary physicians. Interventions: Patients who met the criteria to start weaning underwent a trial of spontaneous breathing lasting up to 2 h. Bedside measurements of respiratory function were obtained immediately before discontinuation of mechanical ventilation and within the first 5 min of spontaneous breathing. The primary physicians were blinded to those measurements, and the decision to extubate a patient at the end of the spontaneous breathing trial or reinstitute mechanical ventilation was made by them. Failure to wean was defined as the requirement for mechanical ventilation at any time during the trial of spontaneous breathing (trial failure) or needing reintubation within 48 h of extubation (extubation failure). Measurements and main results: Seventy-five patients had neither signs of respiratory distress nor deterioration in gas exchange during the trial and were extubated. Twelve patients required reintubation within 48 h. In 9 patients, mechanical ventilation was reinstituted after a median duration of the spontaneous breathing trial of 35 min. The only independent predictor of trial failure was tidal volume indexed to body weight [odds ratio 2.60, 95 % confidence interval (CI) 1.40 to 24.9]. The only independent predictor of extubation failure was frequency-to-tidal volume ratio indexed to body weight (odds ratio 1.23, 95 % CI 1.11 to 1.36). The sensitivity, specificity, and positive and negative predictive values to predict weaning failure were calculated for each of the above variables. These values were 0.48, 0.86, 0.53, and 0.83, respectively, for a frequency-to-tidal volume ratio higher than 11 breaths/min per ml per kg and 0.43, 0.94, 0.69, and 0.83, respectively, for a tidal volume lower than 4 ml/kg. Conclusions: Three-quarters of ventilated children can be successfully weaned after a trial of spontaneous breathing lasting 2 h. Both tidal volume and frequency-to-tidal volume ratio indexed to body weight were poor predictors of weaning failure in the study population. Received: 20 February 1998 Accepted: 10 June 1998     

Weaning children from mechanical ventilation: a prospective randomized trial of protocol-directed versus physician-directed weaning.

OBJECTIVE: Compare outcomes between physician-directed and protocol-directed weaning from mechanical ventilation in pediatric patients. DESIGN: Prospective-randomized. SETTING: Pediatric and cardiac intensive care units in a 307-bed tertiary referral hospital for children. INTERVENTIONS: The control group (physician-directed) was weaned according to individual physician order for reduction in minute ventilation, positive end-expiratory pressure, and ordered oxygen saturation parameters for reduction in fraction of inspired oxygen (F(IO)(2)). The study group (protocol-directed) was weaned according to a predetermined algorithm developed for the purpose of this investigation. METHODS: The study enrolled 223 patients (116 physician-directed, 107 protocol-directed). All patients were monitored for hemodynamics, ventilator parameters, arterial blood gas values when available, oxygen saturation, weaning time, pre-weaning time, extubation time, and time on F(IO)(2) > or = 0.40. We also monitored the incidence of reintubation, subglottic stenosis, tracheitis, and pneumonia. The protocol-directed group had additional measurements of actual versus predicted minute volume, comparisons of respiratory rate (actual versus predicted for age), and presence of spontaneous breathing effort for 10 consecutive minutes. Data analysis was done according to intent to treat. RESULTS: There was no significant difference in 12-hour and 24-hour pediatric risk of mortality (PRISM III) scores between groups. The protocol-directed group overall had shorter total ventilation time, weaning time, pre-weaning time, time to extubation, and time on F(IO)(2) >0.40, although after stratification for respiratory diagnosis, only the difference in weaning time remained significant. There was no difference in the incidence of reintubation, new-onset tracheitis, subglottic stenosis, or pneumonia. CONCLUSIONS: Protocol-directed weaning resulted in a shorter weaning time than physician-directed weaning in these pediatric patients.     

成人心脏外科术后患者实施早期拔管策略效果观察与护理

目的探讨ICU护士主导实施的早期拔管策略在成人心脏外科术后机械通气患者中的应用效果及护理要点。方法回顾心脏术后经口气管插管入胸心外科ICU行机械通气治疗的156例患者的拔管情况,按照时间顺序分为传统组和干预组（早期拔管组）, 2组患者机械通气模式及参数、撤机方式、撤机后治疗护理等方法均相同,干预组是在传统组基础上以ICU护士主导实施综合早期拔管策略。观察撤机30 min 2组心率、呼吸、血压、PaO2/FiO2、PaCO2及拔管后无创正压通气（NPPV）例数、24 h再插管例数、拔管前机械通气时间及撤机时间等指标。结果撤机后30 min 2组患者心率、呼吸、血压、（53＊2PaCO2及拔管后NPPV例数、24 h再插管例数等指标无统计学差异（P＞0.05）, 干预组PaO2/FiO2则较传统组显著改善）（P＜0.05）, 且干预组拔管前机械通气时间、撤机时间显著短于传统组（P＜0.05）。结论ICU护士实施的早期拔管策略对心脏外科术后撤机患者是安全的,能提高早期拔管成功率,减少机械通气并发症。     

Outcome of reintubated patients after scheduled extubation

Purpose

The main objective of study was to evaluate the outcome of patients who require reintubation after elective extubation.

Materials and Methods

This is an observational, prospective cohort study including mechanically ventilated patients who passed successfully a spontaneous breathing trial. Patients were observed for 48 hours after extubation. During this time, reintubation or use of noninvasive positive pressure ventilation was considered as a failure. Reintubated patients were followed after the reintubation to register complications and outcome.

Results

A total of 1,152 extubated patients were included in the analysis. Three hundred thirty-six patients (29%) met the criteria for extubation failure. Extubation failure was independently associated with mortality (odds ratio, 3.29; 95% confidence interval, 2.19-4.93). One hundred eighty patients (16% of overall cohort) required reintubation within 48 hours after extubation. Median time from extubation to reintubation was 13 hours (interquartile range, 6-24 hours). Reintubation was independently associated with mortality (odds ratio, 5.18; 95% confidence interval, 3.38-7.94; P < .001). Higher mortality of reintubated patients was due to the development of complications after the reintubation.

Conclusions

In a large cohort of scheduled extubated patients, one third of patients developed extubation failure, of whom half needed reintubation. Reintubation was associated with increased mortality due to the development of new complications after reintubation.     

Noninvasive mechanical ventilation during the weaning process: facilitative,curative, or preventive?

To avoid the complications associated with endotracheal intubation, noninvasive positive-pressure ventilation (NPPV) has been proposed in the management of ventilator weaning in patients with acute respiratory failure (ARF) of various etiologies. Several studies have been performed to assess the benefit of NPPV in various weaning strategies, including permitting early extubation in patients who fail to meet standard extubation criteria (facilitation use), avoiding reintubation in patients who fail extubation (curative use), and preventing extubation failure in nonselected and selected patients (preventive use). NPPV has been successfully used in facilitating early extubation, particularly in patients with chronic obstructive pulmonary disease. In contrast, applying curative NPPV to treat postextubation ARF in nonselected populations may not be effective and could even be deleterious. Early use of NPPV was successful in preventing ARF after extubation, and decreased the need for reintubation in selected patients at risk of developing postextubation ARF. It is important that caregivers clearly differentiate among these application modalities of NPPV. The skills and expertise of both medical and nonmedical personnel are crucial predictive factors for the success of NPPV in the ventilator weaning process.     

Extubation after transsternal thymectomy for myasthenia gravis: a prospective analysis.

Recommendations concerning postoperative extubation after thymectomy for myasthenia gravis are presently based upon retrospective chart reviews. We present the results of a prospective investigation of time to extubation after thymectomy for 14 patients over a 12-month period based upon a protocol that included preoperative immunologic therapy, combined epidural and general anesthesia, postoperative epidural narcotic analgesia, and a standardized approach to discontinuation of ventilatory support. After a neurologist took measures to optimize preoperative neuromuscular function, all 14 patients received agents to produce lumbar epidural anesthesia and light general anesthesia. Muscle relaxants were avoided in all but one patient. Postoperative analgesia was initially maintained with epidural hydromorphone, then therapy was switched to patient-controlled intravenous morphine sulfate. Criteria for weaning from mechanical ventilation, first measured at the end of anesthesia, were partial pressure of oxygen (arterial) greater than or equal to 90 mm Hg (fraction of inspired oxygen = 0.40), partial pressure of carbon dioxide (arterial) less than or equal to 50 mm Hg, pH greater than or equal to 7.30, and respiratory rate less than or equal to 30 breaths/min. If these criteria were not met, ventilatory support was continued postoperatively with intermittent mandatory ventilation, and the patient was weaned gradually from this support. Criteria for extubation included meeting the criteria for weaning, vital capacity greater than or equal to 10 mL/kg, and inspiratory pressure better than -30 cm H2O. Criteria for reintubation included tachypnea (respiratory rate greater than 40 breaths/min), respiratory acidosis not due to narcotics, or vital capacity less than or equal to 8 mL/kg. The mean time to extubation was 9 hours (range, 0.75 to 25 hours). Mean preoperative vital capacity was 2.59 +/- 0.64 L (range, 1.90 to 4.20), which decreased approximately 50% to 1.19 +/- 0.39 L (range, 0.70 to 2.0) at the time of extubation. No patient required reintubation. Half of the patients required postoperative anticholinesterase therapy based upon serial neurologic examinations; there were no instances of cholinergic crisis. Thirteen patients returned to the ward on the first postoperative day, and one on the second day. Thirteen patients preferred epidural analgesia to patient-controlled analgesia. The time to extubation and average length of stay in an intensive care setting were markedly reduced compared to those reported in previous retrospective studies. We conclude that a multidisciplinary approach that optimizes neuromuscular function and decreases poststernotomy pulmonary insult will shorten the time to extubation and decrease the length of stay in the intensive care or recovery room after thymectomy.     

Work of breathing: reliable predictor of weaning and extubation

During the course of a critical illness, many patients become ventilator dependent. The standard assessment criteria are not always accurate in predicting potential for extubation. This investigation was designed to analyze whether the work of breathing (WOB) was a more reliable predictor of ventilator dependence. Twenty consecutive ventilator-dependent patients were prospectively studied. Nineteen required ventilator support for greater than 2 wk and all were considered ventilator dependent because of their inability to tolerate weaning trials. The oxygen consumption (VO2) and resting energy expenditure were measured using a metabolic gas monitor. Respiratory mechanics and arterial blood gas measurements were obtained, and the deadspace to tidal volume ratio (VD/VT) was calculated. The WOB was determined by the difference in VO2 between spontaneous and mechanical ventilation, and expressed as a percentage of VO2 during mechanical ventilation. Five of eight patients with a WOB less than 15% (mean 1.9) were extubated within 2 wk of study, while none of 12 patients with a WOB greater than or equal to 15% (mean 34) were able to be extubated in this period. The differences in the WOB between the two groups were statistically significant (p less than .01), while there was no significant difference in mechanics, PaCO2, VD/VT or measured resting energy expenditure. These data support the use of WOB determinations in evaluating extubation potential. Using a reference value for the WOB of 15%, this study had a sensitivity of 100% and a specificity of 80%. This proved to be of greater predictive value than traditional criteria.     

Predicting extubation failure after successful completion of a spontaneous breathing trial

OBJECTIVE: To derive a clinical prediction rule that uses bedside clinical variables to predict extubation failure (reintubation within 48 h) after a successful spontaneous breathing trial. METHODS: This prospective observational cohort study was performed at the Northwestern Memorial Hospital in Chicago, Illinois, which is a large tertiary-care university hospital. Among 673 consecutive patients who received mechanical ventilation during a 15-month period, 122 were ventilated for at least 2 days and did not undergo withdrawal of support or tracheostomy. These patients were followed after extubation to identify those who were reintubated within 48 h (extubation failure). We used logistic regression analysis to identify variables that predict reintubation, and we used bootstrap resampling to internally validate the predictors and adjust for overoptimism. RESULTS: Sixteen (13%) of the 122 patients required reintubation within 48 h. Three clinical variables predicted reintubation: moderate to copious endotracheal secretions (p = 0.001), Glasgow Coma Scale score < or =10 (p = 0.004), and hypercapnia (P(aCO(2)) > or = 44 mm Hg) during the spontaneous breathing trial (p = 0.001). Using logistic regression and bootstrap resampling to adjust for overfitting, we derived a clinical prediction rule that combined those 3 clinical variables (area under the receiver operating characteristic curve 0.87, 95% confidence interval 0.74-0.94). CONCLUSIONS: With our clinical prediction rule that incorporates an assessment of mental status, endotracheal secretions, and pre-extubation P(aCO(2)), clinicians can predict who will fail extubation despite a successful spontaneous breathing trial.     

Reintubation after planned extubation in surgical ICU patients: a case-control study

OBJECTIVES: Risk factors of reintubation were studied after planned extubation in a surgical ICU. METHODS: A retrospective case-control study was performed in patients ventilated more than 48 h. Case patients (CP; n=20) were those requiring reintubation within 72 h after planned extubation, and control patients ( n=20) were those successfully extubated. Controls were matched with CP for age, admission SAPS II, and duration of mechanical ventilation before extubation. RESULTS: CP had a significantly higher maximal respiratory rate during T tube trial and lower minimal SaO(2). More CP were treated with volume assist controlled (VAC) mode on the morning of extubation (60% vs. 25%). Multivariate analysis identified only VAC mode as an independent factor associated with reintubation. CP had longer ICU stay and a higher incidence of nosocomial pneumonia and tracheostomy. There was no difference in ICU mortality between CP and CTLP. CONCLUSIONS: The VAC mode of weaning of surgical ICU patients is associated with an increased incidence of reintubation and morbidity after planned extubation. This probably reflects the clinical condition of patients unable to tolerate pressure support.     

Extubation outcome following a spontaneous breathing trial with automatic tube compensation versus continuous positive airway pressure

OBJECTIVE: We hypothesized that the additional use of automatic tube compensation (ATC) during a spontaneous breathing trial with continuous positive airway pressure (CPAP), by minimizing respiratory work, would result in more patients undergoing successful extubation. DESIGN: Prospective, randomized, controlled study. SETTING: A ten-bed, general intensive care department at a tertiary-care hospital. PATIENTS: Adult patients (n=99) who had undergone mechanical ventilation for >24 hrs and met defined criteria for a weaning trial. INTERVENTIONS: Patients were randomized to undergo a 1-hr spontaneous breathing trial with either ATC with CPAP (ATC group, n=51) or CPAP alone (CPAP group, n=48). ATC was provided by commercially available mechanical ventilators. Patients tolerating the spontaneous breathing trial underwent immediate extubation. The primary outcome measure was successful extubation, defined as the ability to maintain spontaneous breathing for 48 hrs after discontinuation of mechanical ventilation and extubation. MEASUREMENTS AND MAIN RESULTS: There were no significant differences in demographic, respiratory, or hemodynamic characteristics between the two groups at the start of the spontaneous breathing trial. There was a trend for more patients in the ATC group to tolerate the breathing trial and undergo extubation (96% vs. 85%; p=.08). The rate of reintubation was 14% in the ATC group and 24% in the CPAP group (p=.28). Significantly more patients in the ATC group thus met the criteria for successful extubation (82% vs. 65%; p=0.04). CONCLUSION: This is the largest single-center study to date assessing the use of commercially available ATC and suggests that this might be a useful mode for performing a spontaneous breathing trial preceding extubation in a general intensive care population.     

Extubation failure: diagnostic value of occlusion pressure (P0.1) and P0.1-derived parameters

OBJECTIVE: To evaluate the ability of the new, built-in occlusion pressure (P0.1) measurement to predict extubation failure. DESIGN AND SETTING: Prospective observational multicentre study in the ICU of five general hospitals. PATIENTS: Hundred thirty patients on mechanical ventilation longer than 48 h when considered ready for weaning. MEASUREMENTS AND RESULTS: Patients underwent a 30-min spontaneous breathing trial with simultaneous monitoring of occlusion pressure (P0.1) and breathing pattern (f/Vt). Sixteen patients (12%) failed the weaning trial and full ventilatory support was resumed, while 114 tolerated the trial and were extubated. Twenty-one (18%) required reintubation within 48 h. The area under the ROC curve for diagnosing extubation failure was 0.53 for f/Vt, 0.59 for P0.1 and 0.61 for P0.1*f/Vt (p=NS). Accordingly, P0.1*f/Vt more than 100 detected extubation failure with a sensitivity of 0.89, specificity of 0.35, positive predictive value of 0.21 and negative predictive value of 0.94. CONCLUSION: During a first trial of spontaneous breathing on pressure support ventilation (PSV), bedside P0.1 and P0.1*f/Vt are of little help, if any, for predicting extubation failure.     

Differences in respiratory parameters during continuous positive airway pressure and pressure support ventilation in infants and children

The extubation criteria of pressure support ventilation (PSV) in infants and children were not yet established. We studied the differences in respiratory parameters during continuous positive airway pressure (CPAP) using a constant flow type ventilator and PSV using a demand valve type ventilator. Nineteen children (1.9+/-2.9 years old) who were ready to extubate were studied. All patients had recovered from their respiratory failure and had finished the weaning process of the ventilatory support. They were scheduled for extubation on the next day when their ventilatory mode had attained to a PSV of 3 cmH2O with a positive end-expiratory pressure (PEEP) of 3 cmH2O. On the extubation day, tidal volume (TV) and respiratory frequency (RR) were measured with a respiratory monitor at two modes (CPAP of 3 cmH2O and PSV), and the duty ratio (DR) and mean inspiratory flow (MF) were calculated. The sequence of the ventilatory mode was random. No case required reintubation. TV was 61.6+/-54.9 during CPAP and 67.7+/-61.4 ml during PSV, and RR was 38.5+/-10.6 and 37.1+/-8.8 beats/min., respectively. DR was 0.382+/-0.067 and 0.359+/-0.085, and MF was 96.6+/-78.3 and 101.0+/-69.0 ml/sec., respectively. The measured parameters and calculated values showed no significant difference between CPAP and PSV. It was found that the respiratory parameters were almost the same with CPAP and PSV immediately before the extubation, and the previous extubation criteria of CPAP can be used.     

Noninvasive ventilation immediately after extubation improves weaning outcome after acute respiratory failure: a randomized controlled trial

Introduction

Noninvasive ventilation (NIV), as a weaning-facilitating strategy in predominantly chronic obstructive pulmonary disease (COPD) mechanically ventilated patients, is associated with reduced ventilator-associated pneumonia, total duration of mechanical ventilation, length of intensive care unit (ICU) and hospital stay, and mortality. However, this benefit after planned extubation in patients with acute respiratory failure of various etiologies remains to be elucidated. The aim of this study was to determine the efficacy of NIV applied immediately after planned extubation in contrast to oxygen mask (OM) in patients with acute respiratory failure (ARF).

Methods

A randomized, prospective, controlled, unblinded clinical study in a single center of a 24-bed adult general ICU in a university hospital was carried out in a 12-month period. Included patients met extubation criteria with at least 72 hours of mechanical ventilation due to acute respiratory failure, after following the ICU weaning protocol. Patients were randomized immediately before elective extubation, being randomly allocated to one of the study groups: NIV or OM. We compared both groups regarding gas exchange 15 minutes, 2 hours, and 24 hours after extubation, reintubation rate after 48 hours, duration of mechanical ventilation, ICU length of stay, and hospital mortality.

Results

Forty patients were randomized to receive NIV (20 patients) or OM (20 patients) after the following extubation criteria were met: pressure support (PSV) of 7 cm H₂O, positive end-expiratory pressure (PEEP) of 5 cm H₂O, oxygen inspiratory fraction (FiO₂) ≤ 40%, arterial oxygen saturation (SaO₂) ≥ 90%, and ratio of respiratory rate and tidal volume in liters (f/TV) < 105. Comparing the 20 patients (NIV) with the 18 patients (OM) that finished the study 48 hours after extubation, the rate of reintubation in NIV group was 5% and 39% in OM group (P = 0.016). Relative risk for reintubation was 0.13 (CI = 0.017 to 0.946). Absolute risk reduction for reintubation showed a decrease of 33.9%, and analysis of the number needed to treat was three. No difference was found in the length of ICU stay (P = 0.681). Hospital mortality was zero in NIV group and 22.2% in OM group (P = 0.041).

Conclusions

In this study population, NIV prevented 48 hours reintubation if applied immediately after elective extubation in patients with more than 3 days of ARF when compared with the OM group.

Trial Registration number

ISRCTN: 41524441.     

Airway occlusion pressure at 0.1 s (P0.1) after extubation: an early indicator of postextubation hypercapnic respiratory insufficiency

Objective: To examine variables associated with postextubation respiratory distress in chronic obstructive pulmonary disease (COPD) patients. Design: Prospective, clinical investigation. Setting: Intensive care unit of a university hospital. Patients: Forty COPD patients, considered ready for extubation. Measurements and main results: We recorded, from the digital display of a standard ventilator, breathing frequency (f), tidal volume (VT) and f/VT for the respiratory pattern, airway occlusion pressure at 0.1 s (P0.1) for the respiratory drive and measured blood gases : i) before extubation, following 30 min of a 6 cm H₂O pressure support (PS) ventilation trial, ii) 1 h after extubation, at the 30th min of a face mask 4 cm H₂O PS ventilation trial. According to the weaning outcome, the patients were divided into two groups : respiratory distress, and non-respiratory distress within 72 h of the discontinuation of mechanical ventilation. The respiratory distress was defined as the combination of f more than 25 breaths/min, an increase in PaCO₂ of at least 20 % compared with the value measured after extubation, and pH lower than 7.35. We determined whether those patients who developed respiratory distress after extubation differed from those who did not. Respiratory pattern data and arterial blood gases recorded, either before or after extubation, and P0.1 recorded before extubation, were inadequate to differentiate the two groups. Only P0.1 recorded 1 h after the discontinuation of mechanical ventilation differentiated the patients who developed respiratory distress from those who did not (4.2 ± 0.9 vs 1.8 ± 0.8, p < 0.01). Conclusions: P0.1 recorded after extubation may be a good indicator of postextubation respiratory distress. Measuring P0.1 and/or the analysis of the evolution of this parameter could facilitate decisions during the period following extubation. Received: 23 March 1998 Accepted: 5 October 1998