两种机械通气撤机法在10 kg以下患儿心内直视术后的应用比较

目的比较SIMV模式撤机法与直接撤机法在10 kg以下患儿心内直视术后的撤机效果。方法对32例10 kg以下心内直视术后行机械通气的患儿进行回顾性分析,按照撤机方法的不同分为SIMV模式撤机组与直接撤机组。结果两组相比,撤机所需时间差异有显著性意义(P<0.05),SIMV模式撤机法所需的时间更短,并且呼吸机相关性肺炎(VAP)的发生率更低(P<0.05);两组再置管率差异无统计学意义;两种撤机方法撤机前后的心率、呼吸及血压的变化值比较差异均有显著性意义(P<0.05);两种方法撤机前后的PO2、PCO2及pH值的比较,差异均无统计学意义(P>0.05)。结论10 kg以下行心内直视术后的患儿应用SIMV法撤机能够缩短呼吸机辅助的时间和降低呼吸机相关性肺炎的发生率,效果优于直接撤机法。     

Pattern of spontaneous breathing: potential marker for weaning outcome

OBJECTIVE: To quantitatively assess the spontaneous breathing (SB) pattern, during minimal ventilatory support, of patients who pass or fail weaning trials from mechanical ventilation. DESIGN: A prospective, clinical trial. SETTING: Intensive care unit of a university teaching hospital. PATIENTS: Fifty-two tracheally intubated and hemodynamically stable patients who were judged clinically ready for extubation. METHODS: Using a computerized respiratory profile monitor, continuous respiratory parameters were obtained while patients were receiving four or less synchronized intermittent mandatory (SIMV) breaths and during CPAP trials. Coefficients of variation (CV) of spontaneous tidal volumes and flows during SIMV trials as well as the entropies and dimensions of the breathing patterns during CPAP trials were used to assess the dynamical breathing behaviors of the patients who passed or failed weaning trials. MEASUREMENTS AND RESULTS: Thirty-nine extubations were successful and 13 were not. The CV of the spontaneous tidal volumes (VT) and the spontaneous peak inspiratory flows (PF), the Kolmogorov entropy and the dimension of the SB patterns were compared in the two groups. The CV of VT (9.13 +/- 4.11 vs 26.07 +/- 6.94), the CV of PF (11.63 +/- 4.18 vs 29.88 +/- 12.07), the Kolmogorov entropy (0.09 +/- 0.03 bits/cycle vs 0.39 +/- 0.09 bits/cycle), and the dimension of the SB pattern (1.33 +/- 0.07 vs 3.93 +/- 0.47) were all significantly smaller (P < 0.05) in the successfully extubated group versus the group that failed extubation. CONCLUSION: The spontaneous breathing pattern during minimal mechanical ventilatory support is more chaotic in patients who failed extubation trials compared to patients who passed extubation trials. Thus, we speculate that characterizing the SB pattern during minimal ventilatory support might be a useful tool in differentiating between extubation success and failure.     

Weaning from mechanical ventilation: old and new strategies.

The strategies available for weaning patients from mechanical ventilation are many: T-piece mode, SIMV, PSV, and combinations of each. T-piece trials alternating with SIMV or AC provide periods of spontaneous breathing with rest on the ventilator. Decreasing SIMV rates gradually increases the patient's independence and spontaneous breathing; however, may result in an increased work of breathing with some systems. Alternatives such as flow-by and the addition of PSV may assist in the reduction of airway resistance. PSV weaning alone or in combination with SIMV or T-piece trials reduces work of breathing, promotes respiratory muscle training, and improves patient-ventilator interaction. Schuster states "the specific weaning technique employed is often less important than the care with which it is applied."     

Interactive Simulation System for Artificial Ventilation on the Internet: Virtual Ventilator

Objective. To develop an interactive simulation system “virtual ventilator” that demonstrates the dynamics of pressure and flow in the respiratory system under the combination of spontaneous breathing, ventilation modes, and ventilator options. The simulation system was designed to be used by unexperienced health care professionals as a self-training tool. Methods. The system consists of a simulation controller and three modules: respiratory, spontaneous breath, and ventilator. The respiratory module models the respiratory system by three resistances representing the main airway, the right and left lungs, and two compliances also representing the right and left lungs. The spontaneous breath module generates inspiratory negative pressure produced by a patient. The ventilator module generates driving force of pressure or flow according to the combination of the ventilation mode and options. These forces are given to the respiratory module through the simulation controller. Results. The simulation system was developed using HTML, VBScript (3000 lines, 100 kB) and ActiveX control (120 kB), and runs on Internet Explorer (5.5 or higher). The spontaneous breath is defined by a frequency, amplitude and inspiratory patterns in the spontaneous breath module. The user can construct a ventilation mode by setting a control variable, phase variables (trigger, limit, and cycle), and options. Available ventilation modes are: controlled mechanical ventilation (CMV), continuous positive airway pressure, synchronized intermittent mandatory ventilation (SIMV), pressure support ventilation (PSV), SIMV + PSV, pressure-controlled ventilation (PCV), pressure-regulated volume control (PRVC), proportional assisted ventilation, mandatory minute ventilation (MMV), bilevel positive airway pressure (BiPAP). The simulation system demonstrates in a graph and animation the airway pressure, flow, and volume of the respiratory system during mechanical ventilation both with and without spontaneous breathing. Conclusions. We developed a web application that demonstrated the respiratory mechanics and the basic theory of ventilation mode.     

Automatic tube compensation in patients after cardiac surgery: effects on oxygen consumption and breathing pattern

OBJECTIVE: To evaluate patients without prior pulmonary disease after cardiac surgery and to determine whether resistive unloading by automatic tube compensation, pressure support ventilation, and continuous positive airway pressure has different effects on oxygen consumption, breathing pattern, gas exchange, and hemodynamics. DESIGN: Prospective, randomized, controlled study. SETTING: Tertiary care, postoperative intensive care unit. PATIENTS: Twenty-one patients scheduled for open heart coronary artery bypass graft surgery. INTERVENTIONS: Each patient was ventilated with all three modes in random order. MEASUREMENTS AND MAIN RESULTS: Patients were ventilated in three modes, each applied for 30 mins according to computer-generated randomization: pressure support ventilation with 5 cm H2O, continuous positive airway pressure, and automatic tube compensation. Oxygen consumption was calculated by means of indirect calorimetry. The hypnotic state of the patients was monitored by Bispectral Index. For hemodynamic measurements, a fiberoptic pulmonary artery catheter was inserted. The main finding of our study was that oxygen consumption and breathing pattern (tidal volume and respiratory rate) did not differ significantly during automatic tube compensation and pressure support ventilation compared with continuous positive airway pressure (oxygen consumption, 170 +/- 29 vs. 170 +/- 26 vs. 174 +/- 29 mL.min.m, respectively; tidal volume, 466 +/- 132 vs. 484 +/- 125 vs. 470 +/- 119 mL, respectively; respiratory rate, 16 +/- 4 vs. 15 +/- 4 vs. 16 +/- 4 breaths/min, respectively). Automatic tube compensation and pressure support ventilation had no clinical effects on gas exchange and hemodynamic variables compared with continuous positive airway pressure. None of the variables differed significantly during the three ventilatory settings. CONCLUSION: In postoperative tracheally intubated patients with normal ventilatory demand, automatic tube compensation and pressure support ventilation with 5 cm H2O lead to identical oxygen consumption, breathing patterns, gas exchange, and hemodynamics. We, therefore, suggest that this group of patients does not need any additional positive pressure support from the ventilator to overcome the additional work of breathing imposed by the endotracheal tube during the weaning phase from mechanical ventilation.     

Using ASV mode for respiratory support withdrawal in patients after posterior fossa surgery

The study gives data on how to improve the way from mechanical to spontaneous breathing in patients with weakened respiratory drive after posterior fossa tumor removal. We compared the effectiveness of two methods of weaning from mechanical ventilation in these patients. The main group consisted of 6 patients weaned from ventilator with ASV mode. The control group was made up of 10 patients weaned from ventilator with SIMV or PS modes. The duration of weaning from ventilator using ASV mode was significantly shorter than with SIMV or PS modes. During ASV ventilation spontaneous breath rate gradually increased. In all patients the level of P0,1 index representing respiratory center activity was initially lower than normal. While spontaneous breath activity increased the level of P0,1 index also gradually normalized. Plmax index (respiratory effort index) measured once a day increased as well. Weakened respiratory drive is accompanied by P0,1 and Plmax indexes' decrease in patients after posterior fossa tumor removal. ASV mode in these patients allows quicker weaning from mechanical ventilation.     

Patient-ventilator interaction and sleep in mechanically ventilated patients: pressure support versus proportional assist ventilation

OBJECTIVES: To understand the role of patient-ventilator asynchrony in the etiology of sleep disruption and determine whether optimizing patient-ventilator interactions by using proportional assist ventilation improves sleep. DESIGN: Randomized crossover clinical trial. SETTING: A tertiary university medical-surgical intensive care unit. PATIENTS: Thirteen patients during weaning from mechanical ventilation. INTERVENTIONS: Patients were randomized to receive pressure support ventilation or proportional assist ventilation on the first night and then crossed over to the alternative mode for the second night. Polysomnography and measurement of light, noise, esophageal pressure, airway pressure, and flow were performed from 10 pm to 8 am. Ventilator settings (pressure level during pressure support ventilation and resistive and elastic proportionality factors during proportional assist ventilation) were set to obtain a 50% reduction of the inspiratory work (pressure time product per minute) performed during a spontaneous breathing trial. MEASUREMENTS AND MAIN RESULTS: Arousals per hour of sleep time during pressure support ventilation were 16 (range 2-74) and 9 (range 1-41) during proportional assist ventilation (p = .02). Overall sleep quality was significantly improved on proportional assist ventilation (p < .05) due to the combined effect of fewer arousals per hour, fewer awakenings per hour (3.5 [0-24] vs. 5.5 [1-24]), and greater rapid eye movement (9% [0-31] vs. 4% [0-23]), and slow wave (3% [0-16] vs. 1% [0-10]) sleep. Tidal volume and minute ventilation were lower on proportional assist ventilation, allowing for a greater increase in Paco2 during the night. Patient-ventilator asynchronies per hour were lower with proportional assist ventilation than with pressure support ventilation (24 +/- 15 vs. 53 +/- 59; p = .02) and correlated with the number of arousals per hour (R = .65, p = .0001). CONCLUSIONS: Patient ventilator discordance causes sleep disruption. Proportional assist ventilation seems more efficacious than pressure support ventilation in matching ventilatory requirements with ventilator assistance, therefore resulting in fewer patient-ventilator asynchronies and better quality of sleep.     

Use of a handheld computer by respiratory care practitioners to improve the efficiency of weaning patients from mechanical ventilation

OBJECTIVE: To evaluate the impact of a handheld computer containing a unit-specific weaning protocol on the efficiency of weaning patients from mechanical ventilation. DESIGN: A prospective before-after study design with consecutive control and intervention time periods. SETTING: A medical intensive care unit of an urban teaching hospital. PARTICIPANTS: All patients receiving mechanical ventilation in the medical intensive care unit were eligible for study enrollment. INTERVENTIONS: Weaning of mechanical ventilation during the control period was conducted by respiratory care practitioners using a previously published protocol (n = 176). During the intervention period, respiratory care practitioners weaned patients using a handheld computer version of the same protocol (n = 176). MEASUREMENTS AND RESULTS: The time for the first spontaneous breathing trial to occur was significantly shorter during the intervention period compared with the control period (49.9 +/- 63.2 hrs vs. 72.5 +/- 86.9 hrs, p=.018). The percentage of patients undergoing a spontaneous breathing trial when first meeting established criteria for a spontaneous breathing trial was significantly greater during the intervention period (89.8% vs. 63.6%, p<.001). Length of stay in the intensive care unit was also significantly shorter for patients during the intervention period (6.2 +/- 7.1 days vs. 7.7 +/- 8.0 days, p=.018). CONCLUSIONS: This experience suggests that respiratory care practitioners employing a weaning protocol programmed on a handheld computer can wean patients from mechanical ventilation more efficiently compared with the use of a paper-based weaning protocol.     

Pulse and Systolic Pressure Variation Assessment in Partially Assisted Ventilatory Support

OBJECTIVE: The use of pulse pressure variation (PPV) and systolic pressure variation (SPV) is possible during controlled ventilation (MV). Even in acute respiratory failure, controlled MV tends to be replaced by assisted ventilatory support. We tested if PPV and SPV during flow triggered synchronized intermittent mechanical ventilation (SIMV) could be as accurate as in controlled MV. METHODS: Prospective case-controlled study. Thirty patients who met criteria of weaning from controlled MV. Twenty minutes pressure support ventilation with 3 min(-1) flow triggered SIMV breathes (10 ml kg(-1)) T1, then three consecutive breaths in controlled MV (respiratory rate 12 min(-1),10 ml kg(-1)) T2. PPV and SPV were measured in T1 and T2. Correlation and Bland-Altman analysis were used to compare respective values of PPV and SPV in the two modes of ventilation. RESULTS: Significant correlations were found between dynamic indices in SIMV during pressure support ventilation and those in controlled MV mode. The mean differences between two measurements were: PPV 0.6+/-2.8% (limit of agreement: -5.0 and 6.2), SPV 0.5+/-2.3 mmHg (limit of agreement: -4.0 and 5.1). CONCLUSIONS: PPV and SPV measured during SIMV fitted with the findings in controlled MV. Dynamic indexes could be accurately monitored in patients breathing with assisted respiratory assistance adding an imposed large enough SIMV breath.     

加强监护室内有创序贯无创机械通气的临床撤机方法研究

目的：探讨无创压力支持通气在加强监护室（ICU）内的辅助撤机作用。方法：以2008年11月-2011年3月入住ICU接受气管插管机械通气的32例患者为研究对象,通气模式以同步间歇指令通气（SIMV）和压力支持通气（PSV）为基础,必要时联合呼气末正压（PEEP）;根据患者的血气分析值,合理调整吸入氧浓度分数（FiO2）、呼吸频率（RR）、吸气相压力（IPAP）、呼气相压力（EPAP）值,比较有创通气与无创通气状态下RR、心率（HR）、动脉血氧分压（PaO2）、动脉血二氧化碳分压（PaCO2）、pH、动脉血氧饱和度（SaO2）值。结果：有创通气与无创通气各项监测指标均无明显变化（P〉0．05）,经无创通气过渡数日后均可离开ICU。结论：无创正压机械通气作为一种有效的撤机治疗方法,建议临床推广应用。     

The comfort of breathing: a study with volunteers assessing the influence of various modes of assisted ventilation

OBJECTIVE: To assess the subjective feeling of comfort of healthy volunteers breathing on various modes of ventilation used in intensive care. DESIGN: A randomized, prospective, double-blinded, crossover trial using volunteers. SETTING: An intensive care unit (ICU) in a teaching hospital. INTERVENTIONS: We compared, by using healthy volunteers, the subjective feeling of comfort of three modes of ventilation used during the weaning phase of critical illness. We used healthy volunteers to avoid other distracting influences of intensive care that may confound the primary feeling of comfort. The modes we compared were synchronized intermittent mandatory ventilation, assisted spontaneous breathing, and biphasic positive airway pressure. The imposed ventilation was comparable with 50% of the volunteers' normal respiratory effort. The volunteers breathed via a mouthpiece through a ventilator circuit, and the modes of ventilation were introduced in a randomized manner. MEASUREMENTS AND MAIN RESULTS: We measured visual analog scores for comfort for the three modes of ventilation and collected a ranking order and open-ended comments. We demonstrated that at the level of support we imposed, assisted spontaneous breathing was the most comfortable mode of ventilation and that synchronized intermittent mandatory ventilation was the most uncomfortable. These results were strongly supported by both the ranking scale and comments of the volunteers. CONCLUSIONS: Assisted spontaneous breathing was the most comfortable mode of ventilation because the pattern was primarily determined by the volunteer. Synchronized intermittent mandatory ventilation was the most uncomfortable because the ventilatory pattern was imposed on the volunteers, leading to ventilator-volunteer dyssynchrony. We also conclude there is wide individual variation in the subjective feeling of comfort. Whereas the mode of ventilation in ICUs is based primarily on the physiologic needs of the patient, the feeling of comfort may be considered when choosing an appropriate mode of ventilation during the weaning phase of critical illness.     

Is there a preferred technique for weaning the difficult-to-wean patient? A systematic review of the literature

OBJECTIVE: To answer the following question: In difficult-to-wean patients, which of the three commonly used techniques of weaning (T-piece, synchronized intermittent mandatory ventilation, or pressure support ventilation) leads to the highest proportion of successfully weaned patients and the shortest weaning time? DATA SOURCES: Computerized literature searches in MEDLINE (1975-1996), Cinahl (1982-1996), and Healthplan (1985-1996), exploding all Mesh headings pertaining to Mechanical Ventilation and Weaning. Searches were restricted to the English language, adults, and humans. Personal files were hand searched, and references of selected articles were reviewed. STUDY SELECTION: a) Population: Patients requiring a gradual weaning process from the ventilator (either requiring prolonged initial ventilation of >72 hrs or a failed trial of spontaneous breathing after >24 hrs of ventilation); b) Interventions: At least two of the following three modes of weaning from mechanical ventilation must have been compared: T-piece, synchronized intermittent mandatory ventilation, or pressure support ventilation; c) Outcomes: At least one of the following: weaning time (time from initiation of weaning to extubation) or successful weaning rate (successfully off the ventilator for >48 hrs); and d) Study design: Controlled trial. DATA EXTRACTION: Two reviewers independently reviewed the articles and graded them according to their methodologic rigor. Data on the success of weaning and the time to wean were summarized for each study. DATA SYNTHESIS: The search strategy identified 667 potentially relevant studies; of these, 228 had weaning as their primary focus, and of these, 48 addressed modes of ventilation during weaning. Only 16 of these 48 studies had one of the specified outcomes, and only ten of these were controlled trials. Of the ten trials, only four fulfilled all our selection criteria. The results of the trials were conflicting, and there was heterogeneity among studies that precluded meaningful pooling of the results. CONCLUSIONS: There are few trials designed to determine the most effective mode of ventilation for weaning, and more work is required in this area. From the trials reviewed, we could not identify a superior weaning technique among the three most popular modes, T-piece, pressure support ventilation, or synchronized intermittent mandatory ventilation. However, it appears that synchronized intermittent mandatory ventilation may lead to a longer duration of the weaning process than either T-piece or pressure support ventilation. Finally, the manner in which the mode of weaning is applied may have a greater effect on the likelihood of weaning than the mode itself.     

Gradual versus abrupt weaning from respiratory support in acute respiratory failure and advanced chronic obstructive lung disease

Two methods of weaning from mechanical ventilation were compared in 18 instances of acute respiratory failure requiring mechanical ventilation for more than 30 days in patients with advanced chronic obstructive lung disease. All patients were ventilated using intermittent mandatory ventilation. Abrupt weaning (AW) consisted of abruptly discontinuing mechanical ventilation when the patients were considered ready for unassisted breathing. Gradual weaning (GW) involved a gradual reduction in the rate of intermittent mandatory ventilation before starting unassisted breathing. Gradual or abrupt weaning alone was used for weaning in five and four instances, respectively. Both methods were used in nine other instances. In the 14 instances when GW was tried, weaning was successful in three. In the 13 instances when AW was tried, weaning was successful in nine. The time in which mechanical ventilation was required was 64 +/- 31 (SD) days with GW and 42 +/- 12 (SD) days with AW. There was no difference in age, pulmonary function, or arterial blood gas results between the patients being weaned by the different methods. I conclude that GW offers no advantage over AW in weaning patients with advanced chronic obstructive lung disease requiring prolonged mechanical ventilation.     

Ventilator weaning by lung expansion and decannulation

This case series of ventilator-dependent patients with neuromuscular disease who had no ventilator-free breathing ability demonstrates that decannulation and switching to continuous noninvasive intermittent positive-pressure ventilation combined with regular lung expansion therapy can result in improvements in pulmonary function and at least partial ventilator weaning. These six patients were also managed using mechanical insufflation-exsufflation for regular lung expansion and cough assistance. Thus, some ventilator users with neuromuscular disease can benefit from tracheostomy tube decannulation and transition to noninvasive intermittent positive-pressure ventilation and assisted coughing for ventilator weaning to predominantly nocturnal-only use.     

Various modes of lung ventilation in children during transition to spontaneous breathing

The purpose of the study is to compare the effect of SIMV and BIPAP ventilation modes for the duration of mechanical ventilation, duration of the "weaning" from a respirator, the condition of gas metabolism and hemodynamics in children transferring to spontaneous breathing. In a retrospective cohort study included 30 children (16 boys and 14 girls) aged from 1 month to 18 years, which were on mechanical ventilation for more than 24 hours and required a gradual "weaning" from the unit. The children were treated in the department of general intensive care unit of Tushino City Pediatric Hospital from January 2008 to August 2010. To all the patients with duration of mechanical ventilation of more than 48 hours, as well as with an earlier unsuccessful test of the spontaneous breathing, gradual "weaning" from the unit was conducted. Depending on which mode was used the children were divided into two groups. In the first group SIMV+ PS mode was used for "weaning", while for the second group the BIPAP+ PS mode was used. Patients in both groups did not differ in age, sex, severity of illness at admission on the scale of PRISM, nosological forms and duration of mechanical ventilation before transfer to spontaneous respiration. Transition of patients to spontaneous respiration was accompanied by adaptive changes in the indices of respiratory system and hemodynamics, most pronounced after extubation. The reliable difference in the duration of weaning from the device was (3.21 + 2.0 days in SIMV group vs. 2.75 + 1.34 days in BIPAP group, p = 0.05). In the SIMV group the frequency of desynchronization episodes was greater (SIMV--an average of 3.75 + 1.4 episodes per day compared to 2.37 + 0.85 episodes in the BIPAP group, p = 0.003). The advantages of using BIPAP+ PS mode are the duration of weaning from the unit and the synchronization with the respirator. The statistically significant estimates of the parameters of pulmonary ventilation and hemodynamics require further study.     

The impact of spontaneous breathing during mechanical ventilation

PURPOSE OF REVIEW: In patients with acute respiratory distress syndrome, controlled mechanical ventilation is generally used in the initial phase to ensure adequate alveolar ventilation, arterial oxygenation, and to reduce work of breathing without causing further damage to the lungs. Although introduced as weaning techniques, partial ventilator support modes have become standard techniques for primary mechanical ventilator support. This review evaluates the physiological and clinical effects of persisting spontaneous breathing during ventilator support in patients with acute respiratory distress syndrome. RECENT FINDINGS: The improvements in pulmonary gas exchange, systemic blood flow and oxygen supply to the tissue which have been observed when spontaneous breathing has been maintained during mechanical ventilation are reflected in the clinical improvement in the patient's condition. Computer tomography observations demonstrated that spontaneous breathing improves gas exchange by redistribution of ventilation and end-expiratory gas to dependent, juxtadiaphragmatic lung regions and thereby promotes alveolar recruitment. Thus, spontaneous breathing during ventilator support counters the undesirable cyclic alveolar collapse in dependent lung regions. In addition, spontaneous breathing during ventilator support may prevent increase in sedation beyond a level of comfort to adapt the patient to mechanical ventilation which decreases duration of mechanical ventilator support, length of stay in the intensive care unit, and overall costs of care giving. SUMMARY: In view of the recently available data, it can be concluded that maintained spontaneous breathing during mechanical ventilation should not be suppressed even in patients with severe pulmonary functional disorders.     

Weaning from mechanical ventilation

Practice guidelines on weaning should be based on the results of several well-designed randomized studies performed over the last decade. One of those studies demonstrated that immediate extubation after successful trials of spontaneous breathing expedites weaning and reduces the duration of mechanical ventilation as compared with a more gradual discontinuation of ventilatory support. Two other studies showed that the ability to breathe spontaneously can be adequately tested by performing a trial with either T-tube or pressure support of 7 cmH₂O lasting either 30 or 120 min. In patients with unsuccessful weaning trials, a gradual withdrawal for mechanical ventilation can be attempted while factors responsible for the ventilatory dependence are corrected. Two randomized studies found that, in difficult-to-wean patients, synchronized intermittent mandatory ventilation (SIMV) is the most effective method of weaning.     

以改良格拉斯哥昏迷评分15分为切换点在有创-无创机械通气治疗慢性阻塞性肺疾病所致严重呼吸衰竭中的应用

目的 探讨以改良格拉斯哥昏迷评分(GCS)15分为切换点指导慢性阻塞性肺疾病(COPD)合并呼吸衰竭(呼衰)患者早期拔管改换无创机械通气的可行性,并评价其治疗效果.方法 选择接受气管插管和机械通气的COPD并呼衰患者,采用前瞻性对照研究方法,以2007年3月至2009年11月收治的20例患者为治疗组,采用同步间歇指令通气+压力支持通气(SIMV+PSV)方式行机械通气,待改良GCS评分达15分并稳定2 h的窗口期拔除气管导管,改用经鼻面罩PSV+呼气末正压(PEEP)通气,以后逐渐减小压力支持(PS)水平直至脱机;以2005年3月至2007年3月收治的19例患者为对照组,按常规机械通气及传统脱机方式脱机.动态观察两组患者机械通气前通气及氧合指标,接受有创机械通气时间、总机械通气时间、总住院时间、再插管及呼吸机相关性肺炎(VAP)发生例数.结果 两组机械通气前通气及氧合指标均无明显差异.治疗组较对照组有创通气时间(d:3.2±1.1比10.5±3.2)、总机械通气时间(d:4.8±2.5比10.5±3.2)、总住院时间(d:17±3比22±7)均明显缩短(均P＜0.01);VAP发生数减少(例:0比5,P＜0.01),再插管数稍增加,但无统计学意义(例:3比1,P＞0.05).结论 对COPD合并呼衰的机械通气患者,以改良GCS评分达15分稳定2 h窗口期为时机早期拔管改用经鼻面罩无创通气,可以显著改善患者的治疗效果.

Abstract：

Objective To estimate the feasibility and the efficacy of early extubation and the sequential non-invasive mechanical ventilation (MV) in severe respiratory failure of chronic obstructive pulmonary disease (COPD) with the improved Glasgow coma scale (GCS) score of 15 as the switching point. Methods By a prospective control study, 20 patients with COPD and respiratory failure who had undergone endotracheal intubation and MV from March 2007 to November 2009 were enrolled as treatment group.Invasive MV with synchronous intermittent mandatory ventilation and pressure support ventilation (SIMV+PSV) pattern were given to these patients. When the period of "improved GCS score of 15 standard" window period appeared and being kept for 2 hours, endotracheal tube was extubated, and nasal mask with PSV±positive end-expiratory pressure (PEEP) was used, followed by gradual decrease of the level of pressure support till weaning of MV. Nineteen patients who were treated with MV with ordinary way of weaning from March 2005 to March 2007 served as the control group. Prior to the MV, the ventilation and oxygenation index, the length of invasive MV, total MV time, total hospital stay, re-intubation and ventilator-associated pneumonia (VAP) occurred in the number of cases were observed and compared between two groups. Results There was no significant difference in the ventilation and oxygenation index prior to the MV. Compared with control group, in treatment group, the length of invasive ventilation (days: 3. 2±1.1 vs. 10. 5± 3. 2),the total duration of MV (days: 4. 8±2. 5 vs. 10. 5±3. 2), the length of hospital stay (days:17±3 vs. 22±7) were significantly shorter (all P＜0.01), and the incidence of VAP was significantly lower (cases: 0 vs.5, P＜ 0. 01), while the number of re-intubation was slightly higher but without statistical significance (cases:3 vs. 1, P＞0. 05). Conclusion The application of improved GCS score of 15 as the switching point with 2 hours as window period for early extubation and non-invasive nasal mask ventilation can significantly improve the therapeutic effect in patients with severe respiratory failure in COPD.     

Gastric intramucosal pH and intraluminal PCO2 during weaning from mechanical ventilation

OBJECTIVE: To study the value of gastric intramucosal pH and gastric intraluminal PCO2 measurements to predict weaning outcome from mechanical ventilation. DESIGN: Prospective clinical study. SETTING: Intensive care medicine department of a university hospital. PATIENTS: Nineteen adult critically ill patients who were mechanically ventilated because of acute respiratory failure and were considered ready to be weaned. INTERVENTIONS: The patients were weaned with: synchronized intermittent mandatory ventilation plus positive end-expiratory pressure (SIMV+PEEP) or continuous positive airway pressure with pressure support ventilation (CPAP+PSV). A gastric tonometer was placed in all the patients. Tonometric, respiratory, and hemodynamic variables were measured during the weaning process. MEASUREMENTS: Hemodynamic variables, respiratory mechanics, pulmonary gas exchange, respiratory muscle force, spontaneous pattern of breathing, and the central control of breathing were recorded. Simultaneously, the intramucosal pH and gastric intraluminal PCO2 were measured. MAIN RESULTS: Eleven patients were successfully extubated and eight failed. The patients who failed showed higher values of mouth occlusion pressure, respiratory rate, and effective inspiratory impedance (mouth occlusion pressure/mean inspiratory flow). The intramucosal pH was initially 7.19 +/- 0.22 and decreased to 7.10 +/- 0.16 during the weaning process in patients who failed (p < .05). At the same time, the intramucosal pH showed a nonsignificant change from 7.36 +/- 0.07 to 7.32 +/- 0.07 in the patients who were successfully extubated. The intramucosal pH was statistically different when both groups were compared during the initial and the final evaluations (p < .05). For the initial evaluation, the sensitivity and specificity to predict weaning failure when the intramucosal pH was < or =7.30 were 0.88 (95% confidence interval [CI], 0.66-1) and 0.82 (95% CI, 0.59-1), respectively. The gastric intraluminal PCO2 was higher in patients who failed (p < .05). When gastric intraluminal PCO2 was . or =40 torr during the initial evaluation, weaning failure occurred with a sensitivity of 1 (95% CI, 0.31-1) and a specificity of 0.55 (95% CI, 0.26-0.84). CONCLUSIONS: Weaning failure was associated with gastric intramucosal acidosis. The intramucosal pH and gastric intraluminal PCO2 may be helpful to predict weaning outcome. Further controlled clinical trials in a larger group of patients are needed.     

Laboratory and clinical evaluation of the MAX transport ventilator

Transport of critically ill, mechanically ventilated patients from intensive care units for diagnostic and therapeutic procedures has become common in the last decade. Maintenance of adequate oxygenation and ventilation during transport is mandatory. We evaluated the Hamilton MAX transport ventilator in the laboratory and in the clinical arena to determine its usefulness during in-hospital transport. METHODS: In the laboratory, we determined the MAX's ability to assure tidal volume (VT) delivery in the face of decreasing compliance of a test lung, and we tested the alarm system. Using a two-compartment lung model modified to simulate spontaneous breathing, we also evaluated the responsiveness of the demand valve. The clinical evaluation was accomplished by comparing arterial blood gases and ventilator settings in the intensive care unit to those during transport. RESULTS: As lung compliance was reduced from 0.1 to 0.02 L/cm H2O [1.0 to 0.20 L/kPa], delivered VT fell significantly at each set VT. The alarm systems performed according to manufacturer's specifications. The demand valve triggered appropriately without positive end-expiratory pressure (PEEP), but as PEEP was increased, triggering became more difficult. The demand valve is referenced to ambient pressure and cannot compensate for elevated end-expiratory pressures. During patient transport, arterial blood gases were comparable to those achieved in the ICU. Because an inspired oxygen concentration of 1.0 was used during transport, arterial oxygenation (PaO2) was significantly greater (123 +/- 75 vs 402 +/- 85 torr [16.4 +/- 10 vs 53.6 +/- 11 kPa]). A higher ventilator rate was required during transport to prevent tachypnea (7 +/- 3 vs 12 +/- 6 breaths/min), and peak inspiratory pressure (PIP) was higher during transport (40 +/- 8 vs 52 +/- 11 cm H2O [3.9 +/- 0.8 vs 5.1 +/- 1.1 kPa]). CONCLUSIONS: The MAX is a reliable transport ventilator, capable of maintaining adequate ventilation and oxygenation in a majority of mechanically ventilated patients. Care should be taken to assure adequate VT delivery at high PIP, and ventilator rate may require adjustment to prevent tachypnea associated with triggering the non-PEEP-compensated demand valve when PEEP greater than 8 cm H2O [0.8 kPa] is used.