Effects of the beach chair position, positive end-expiratory pressure, and pneumoperitoneum on respiratory function in morbidly obese patients during anesthesia and paralysis

BACKGROUND: The authors studied the effects of the beach chair (BC) position, 10 cm H2O positive end-expiratory pressure (PEEP), and pneumoperitoneum on respiratory function in morbidly obese patients undergoing laparoscopic gastric banding. METHODS: The authors studied 20 patients (body mass index 42 +/- 5 kg/m2) during the supine and BC positions, before and after pneumoperitoneum was instituted (13.6 +/- 1.2 mmHg). PEEP was applied during each combination of position and pneumoperitoneum. The authors measured elastance (E,rs) of the respiratory system, end-expiratory lung volume (helium technique), and arterial oxygen tension. Pressure-volume curves were also taken (occlusion technique). Patients were paralyzed during total intravenous anesthesia. Tidal volume (10.5 +/- 1 ml/kg ideal body weight) and respiratory rate (11 +/- 1 breaths/min) were kept constant throughout. RESULTS: In the supine position, respiratory function was abnormal: E,rs was 21.71 +/- 5.26 cm H2O/l, and end-expiratory lung volume was 0.46 +/- 0.1 l. Both the BC position and PEEP improved E,rs (P < 0.01). End-expiratory lung volume almost doubled (0.83 +/- 0.3 and 0.85 +/- 0.3 l, BC and PEEP, respectively; P < 0.01 vs. supine zero end-expiratory pressure), with no evidence of lung recruitment (0.04 +/- 0.1 l in the supine and 0.07 +/- 0.2 in the BC position). PEEP was associated with higher airway pressures than the BC position (22.1 +/- 2.01 vs. 13.8 +/- 1.8 cm H2O; P < 0.01). Pneumoperitoneum further worsened E,rs (31.59 +/- 6.73; P < 0.01) and end-expiratory lung volume (0.35 +/- 0.1 l; P < 0.01). Changes of lung volume correlated with changes of oxygenation (linear regression, R2 = 0.524, P < 0.001) so that during pneumoperitoneum, only the combination of the BC position and PEEP improved oxygenation. CONCLUSIONS: The BC position and PEEP counteracted the major derangements of respiratory function produced by anesthesia and paralysis. During pneumoperitoneum, only the combination of the two maneuvers improved oxygenation.     

The impact of morbid obesity, pneumoperitoneum, and posture on respiratory system mechanics and oxygenation during laparoscopy

We studied the effect of morbid obesity, 20 mm Hg pneumoperitoneum, and body posture (30 degrees head down and 30 degrees head up) on respiratory system mechanics, oxygenation, and ventilation during laparoscopy. We hypothesized that insufflation of the abdomen with CO(2) during laparoscopy would produce more impairment of respiratory system mechanics and gas exchange in the morbidly obese than in patients of normal weight. The static respiratory system compliance and inspiratory resistance were computed by using a Servo Screen pulmonary monitor. A continuous blood gas monitor was used to monitor real-time PaCO(2) and PaO(2), and the ETCO(2) was recorded by mass spectrometry. Static compliance was 30% lower and inspiratory resistance 68% higher in morbidly obese supine anesthetized patients compared with normal-weight patients. Whereas body posture (head down and head up) did not induce additional large alterations in respiratory mechanics, pneumoperitoneum caused a significant decrease in static respiratory system compliance and an increase in inspiratory resistance. These changes in the mechanics of breathing were not associated with changes in the alveolar-to-arterial oxygen tension difference, which was larger in morbidly obese patients. Before pneumoperitoneum, morbidly obese patients had a larger ventilatory requirement than the normal-weight patients to maintain normocapnia (6.3 +/- 1.4 L/min versus 5.4 +/- 1.9 L/min, respectively; P = 0.02). During pneumoperitoneum, morbidly obese, supine, anesthetized patients had less efficient ventilation: a 100-mL increase of tidal volume reduced PaCO(2) on average by 5.3 mm Hg in normal-weight patients and by 3.6 mm Hg in morbidly obese patients (P = 0.02). In conclusion, respiratory mechanics during laparoscopy are affected by obesity and pneumoperitoneum but vary little with body position. The PaO(2) was adversely affected only by increased body weight. IMPLICATIONS: Morbid obesity significantly decreases respiratory system compliance and increases inspiratory resistance. Increased body weight, and not altered mechanics of breathing, was associated with worse PaO(2) during laparoscopy.     

免气腹腹腔镜胆囊切除术对呼吸循环及术后并发症的影响

目的 研究免气腹腹腔镜胆囊切除术(laparoscopic cholecystectomy,LC)对呼吸循环功能及术后并发症的影响.方法 60例择期LC患者,ASA Ⅰ或Ⅱ级,用随机数字表法分为A、B两组,每组30例,A组为免气腹组,B组为气腹组.全麻后,潮气量均为10 ml/kg,呼吸频率(RR)均为12次/分,吸呼...     

Effects of the Beach Chair Position, Positive End-expiratory Pressure, and Pneumoperitoneum on Respiratory Function in Morbidly Obese Patients during Anesthesia and Paralysis

Background: The authors studied the effects of the beach chair (BC) position, 10 cm H2O positive end-expiratory pressure (PEEP), and pneumoperitoneum on respiratory function in morbidly obese patients undergoing laparoscopic gastric banding.

Methods: The authors studied 20 patients (body mass index 42 +/- 5 kg/m2) during the supine and BC positions, before and after pneumoperitoneum was instituted (13.6 +/- 1.2 mmHg). PEEP was applied during each combination of position and pneumoperitoneum. The authors measured elastance (E,rs) of the respiratory system, end-expiratory lung volume (helium technique), and arterial oxygen tension. Pressure-volume curves were also taken (occlusion technique). Patients were paralyzed during total intravenous anesthesia. Tidal volume (10.5 +/- 1 ml/kg ideal body weight) and respiratory rate (11 +/- 1 breaths/min) were kept constant throughout.

Results: In the supine position, respiratory function was abnormal: E,rs was 21.71 +/- 5.26 cm H2O/l, and end-expiratory lung volume was 0.46 +/- 0.1 l. Both the BC position and PEEP improved E,rs (P < 0.01). End-expiratory lung volume almost doubled (0.83 +/- 0.3 and 0.85 +/- 0.3 l, BC and PEEP, respectively; P < 0.01 vs. supine zero end-expiratory pressure), with no evidence of lung recruitment (0.04 +/- 0.1 l in the supine and 0.07 +/- 0.2 in the BC position). PEEP was associated with higher airway pressures than the BC position (22.1 +/- 2.01 vs. 13.8 +/- 1.8 cm H2O; P < 0.01). Pneumoperitoneum further worsened E,rs (31.59 +/- 6.73; P < 0.01) and end-expiratory lung volume (0.35 +/- 0.1 l; P < 0.01). Changes of lung volume correlated with changes of oxygenation (linear regression, R2 = 0.524, P < 0.001) so that during pneumoperitoneum, only the combination of the BC position and PEEP improved oxygenation.     

Influence of pneumoperitoneum and patient positioning on respiratory system compliance

STUDY OBJECTIVE: To investigate the influence of pneumoperitoneum (PP) and posture on respiratory compliance and ventilation pressures. DESIGN: Prospective, single blind trial. PATIENTS: 10 female ASA physical status I and II patients scheduled for elective gynecologic laparoscopy. SETTING: University medical center. INTERVENTIONS: Anesthesia was performed as total IV anesthesia (TIVA) with propofol, alfentanil, and atracurium. After induction of anesthesia and orotracheal intubation, the lungs were ventilated to maintain partial pressure of CO(2) (P(ET)CO(2)) of 30 +/- 3 mmHg. Ventilation was kept constant. As gas mixture oxygen and air 1:1 was used without positive end-expiratory pressure (PEEP). MEASUREMENTS: Measurements were taken before and after creation of pneumoperitoneum with an intraabdominal pressure (IAP) of 10 mmHg, of 15 mmHg in 20 degrees head-down tilt, then in 20 degrees head-up tilt, and after deflation of PP. We determined peak inspiratory pressure (PIP), mean airway pressure (mPaw), P(ET)CO(2), expiratory minute volume (V(E)), heart rate (HR), and systolic (SBP), diastolic (DBP), and mean arterial pressure (MAP). Respiratory system compliance (C(eff rs)) was calculated as quotient of tidal volume (V(T)) and PIP. MAIN RESULTS: After creation of PP (IAP 10 mmHg), there was a significant increase of median PIP (3 cmH(2)O), mPaw (1 cm H(2)O) and arterial pressure (BP), (MAP by 7 mmHg), C(eff rs) decreased by 6 mL. cm H(2)O(-1). Increase of IAP to 15 mmHg led to a further increase of PIP (2 cm H(2)O) and mPaw (1 cm H(2)O), and a further decrease of C(eff rs) by 5 mL cm H(2)O(-1); BP decreased (MAP by 5.5 mmHg). Head-up or head down positions showed no significant hemodynamic or pulmonary changes. P(ET)CO(2)increased from 29.5 to 36 mmHg at an IAP of 15 mmHg, but then no further changes were noticed. Five minutes after deflation of pneumoperitoneum all values returned to baseline levels. CONCLUSIONS: Creation of PP at an IAP of 15 mmHg reduced respiratory system compliance, and increased peak inspiratory and mean airway pressures, which quickly returned to normal values after deflation. Head-down or head-up position did not further alter those parameters.     

Cardiopulmonary effects of the laparoscopic pneumoperitoneum in a porcine model of adult respiratory distress syndrome

BACKGROUND: Increasingly, laparoscopy is being used in critically ill patients in whom there is a question of intra-abdominal sepsis. We examine the cardiopulmonary effects of laparoscopy in a porcine model of adult respiratory distress syndrome (ARDS). METHODS: Domestic pigs (n = 12) underwent saline lung lavage and subsequent surgical abdominal exploration using either laparoscopy or conventional laparotomy. Hemodynamic and respiratory measurements were obtained. RESULTS: After pulmonary lavage, the two groups developed similarly diminished arterial pO2 (P <0.001), a worsened pulmonary shunt (P <0.001), and an increased alveolar-arterial oxygen gradient (P <0.001). The pulmonary compliance was significantly decreased in the animals undergoing laparoscopy (versus laparotomy, P <0.05). The mean pulmonary arterial pressure did not differ between the groups. The laparoscopic group had a higher pCO2 (not significant) and was more acidotic (P <0.05) than the laparotomy group. The laparoscopic animals had an increased heart rate (P <0.05), cardiac index (P <0.01), and oxygen delivery (P <0.005) as compared with the laparotomy group. CONCLUSIONS: During laparoscopy, animals with ARDS demonstrate further compromise in pulmonary physiologic parameters but overall cardio-respiratory function is preserved.     

小潮气量加低水平呼气末正压通气对腹腔镜手术患者呼吸力学及肺氧合功能的影响

目的探讨小潮气量加低水平呼气末正压（positive end-expiratory pressure,PEEP）机械通气对肺功能正常患者人工气腹期间呼吸力学及肺氧合功能的影响。方法 2009年8月~2010年4月,45例ASAⅠ~Ⅱ级,择期全麻下行腹腔镜手术患者,随机均分为3组,每组15例。麻醉诱导维持用药相同,气管插管后行机械通气,气腹前3组通气参数均设定为潮气量（VT）8 ml/kg,呼吸频率（RR）12次/min,吸呼比（I∶E）=1∶2。气腹后通气参数设定分别为：Ⅰ组VT=6 ml/kg,RR=18次/min,PEEP=5 cm H2O;Ⅱ组VT=10 ml/kg,RR=10次/min,PEEP=0;Ⅲ组（对照组）同气腹前。分别在气管插管后（T0）,手术开始（T1）,气腹5 min（T2）,气腹30 min（T3）,气腹60 min（T4）,拔气管导管前15 min（T5）,拔气管导管后20 min（T6）监测脉搏血氧饱和度（SpO2）、呼气末CO2分压（PETCO2）、气道峰压（Ppeak）、平均气道压（Pmean）,并计算肺动态顺应性（Cdyn）。分别在T0,T3,T4,T6时点抽取动脉血监测血气,并根据动脉血氧分压（PaO2）、动脉血CO2分压（PaCO2）、吸入氧浓度（FiO2）等计算氧合指数、呼吸指数、肺泡动脉血氧分压差（A-aDO2）。结果 3组各时点平均动脉压及心率、PaO2组间比较差异无显著性（P〉0.05）。与T0时相比,Ppeak气腹后升高（P〈0.05）,Ⅱ、Ⅲ组更明显;Pmean气腹后也升高（P〈0.05）,Ⅰ组最明显;Cdyn气腹后明显降低（P〈0.05）,Ⅱ组最明显;PETCO2明显升高（P〈0.05）,Ⅰ组更明显;气腹后pH值明显降低（P〈0.05）,Ⅰ组最明显;Ⅰ、Ⅲ组PaCO2气腹后明显升高（P〈0.05）,Ⅱ组无明显变化（P〉0.05）。与机械通气时（T0、T3、T4）相比,3组A-aDO2拔管后（T6）明显降低（P〈0.05）,Ⅰ组更明显;氧合指数拔管后（T6）明显降低（P〈0.05）,3组组间差异无显著性（P〉0.05）;呼吸指数拔管后明显降低,Ⅰ组最明显（P〈0.05）。结论小潮气量机械通气加低水平呼气末正压可以有效降低术中气道压,改善肺顺应性,增加肺通气效率,可以安全地应用于腹腔镜手术呼吸管理中。     

压力和容量通气模式对肥胖患者腹腔镜手术中呼吸功能的影响

目的 观察肥胖患者行妇科腹腔镜手术时,两种不同的机械通气模式对患者血流动力学、呼吸力学、动脉氧合的影响. 方法 选择40例行妇科腹腔镜手术的肥胖患者,按数字表法随机分为压力控制通气组(pressure-controlled ventilation,PCV)和容量控制通气组(volume-controlled yentilation,VCV),每组20例.两组患者均实施全凭静脉麻醉方案,分别采用不同的通气模式,维持呼气末二氧化碳分压(end-tial carbon dioxide partial pressure,PETCO2)在35 mm Hg～45 mm Hg(1 mm Hg=0.133kPa)之间.分别于麻醉前5 min(T0)、气腹开始前5 min(T1)、气腹后30min(T2)、气腹解除后5 min(T3)、拔除气管导管时(T4),采集动脉血行血气分析,监测和计算血流动力学指标、血气分析指标、呼吸力学指标. 结果 ①在T1、T2、T3 PCV组的PaO2、氧合指数(oxygenation index,OI)(分别为460±78、453±83、463±95)均高于VCV组(P<0.05);PCV组的肺泡动脉血氧分压差(A-aDO2)(分别为74±25、80±30、82±26)、呼吸指数(respiratory index,RI)(分别为0.32±0.08、0.33±0.10、0.34±0.13)明显低于VCV组(P<0.05).②与T0比较,两组在T2、T3、T4 PaCO2明显升高、pH值明显下降(P<0.05);与VCV组比较,PCV组在各时点差异无统计学意义.③与VCV组比较,PCV组在T2气道峰压Ppeak(27.8±1.6)较低(P<0.05). 结论 PCV在肥胖患者的妇科腹腔镜手术麻醉中改善通气与血流比例,促进气体交换.     

压力控制通气模式在合并轻度阻塞性通气功能障碍老年患者腹腔镜胆囊手术中的通气效果

目的评价压力控制通气(PCV)模式用于合并轻度阻塞性通气功能障碍的老年患者行腹腔镜胆囊切除术中的通气效果。方法选择择期拟行腹腔镜胆囊切除术患者40例,男23例,女17例,年龄65~75岁,ASAⅡ或Ⅲ级,合并轻度阻塞性通气功能障碍,BMI 18.5~23.9kg/m~2,采用随机数字表法,均分为两组:容量控制通气(VCV)组(V组)和PCV组(P组)。新鲜气流量均为2L/min,FiO_260%,VT_8~12ml/kg(P组调整吸气压),I∶E 1∶2,RR 12~16次/分。调整通气参数维持PET_CO2 35~45mm Hg。直至手术结束后气管导管拔除期间两组均分别维持以上通气模式及呼吸参数。于气管插管后5min(气腹前)(T_1)、气腹开始后30min(T_2)、气腹结束后10min(T_3)时记录气道峰压(Ppeak)、气道平台压(Pplat)、吸气阻力(Raw)和动态肺顺应性(Cdyn),采集桡动脉和混合静脉血行血气分析,计算氧合指数(PaO_2/FiO_2)、呼吸指数(RI)、死腔通气率(VD/VT_)和肺内分流率(Qs/Qt)。记录拔管时间、复苏室停留时间和拔管后2h内高碳酸血症、低氧血症等不良反应的发生情况。结果与V组比较,T_1~T_3时P组Ppeak、Pplat和Raw明显降低,Cdyn、PaO_2/FiO_2明显升高,RI、VD/VT_、Qs/Qt和拔管后低氧血症发生率明显降低(P0.05)。两组拔管时间、复苏室停留时间及高碳酸血症发生率差异无统计学意义。结论 PCV模式可安全用于合并轻度阻塞性通气功能障碍的老年腹腔镜胆囊切除术患者,其通气效果好,低氧血症发生率降低。     

Application of nasal bi-level positive airway pressure to respiratory support during combined epidural-propofol anesthesia

STUDY OBJECTIVE: To examine whether nasal bi-level positive airway pressure (BiPAP) can be used as an airway during combined epidural-propofol anesthesia. DESIGN: Prospective, consecutive case series study. SETTING: Operating room at a general hospital. PATIENTS: 213 ASA physical status I and II adult patients undergoing lower extremity or lower abdominal gynecology surgery. INTERVENTIONS: After epidural anesthesia, propofol was infused at 20 mg/kg/hr (P20) for 4 to 5 minutes followed by 5 mg/kg/hr (P5), and nasal continuous positive airway pressure (CPAP) 8 cm H(2)O and BiPAP 14/8 cm H(2)O was applied. In clinical situations, BiPAP with respiratory rate (RR) 10 breaths/min was applied. Furthermore, tidal volume (V(T)) during anesthesia, the effect of changing pressure support levels, and evaluation of pressure-controlled ventilation without spontaneous breathing were examined. MEASUREMENTS AND MAIN RESULTS: CPAP resulted in a high RR, marked increased PaCO(2), and slightly decreased PaO(2), whereas BiPAP showed no change or a slightly decreased RR, slightly increased PaCO(2), and no change in PaO(2) or a great increase in PaO(2) with oxygen delivery. In clinical applications, similar results were found and anesthetic conditions were sufficient. Tidal volume increased after induction and maintained increased values under BiPAP 14/8 cm H(2)O. Of V(T) at 2, 6, or 10 cm H(2)O of pressure support levels, the 6 cm H(2)O was appropriate. Vecuronium injection showed a slight decrease and then increase in V(T) and PaCO(2), but the values were within normal (safe) limits. Respiration after rapid and high-dose infusion of propofol showed a markedly decreased RR, but the V(T) was maintained, and PaCO(2) and PaO(2) were at safe values. Rapid induction with 2.0 mg/kg propofol followed by P5 showed satisfactory results, in all but the obese patients.CONCLUSIONS: BiPAP 14/8 cm H(2)0 with RR at 10 breaths/min during combined epidural-propofol anesthesia can be used to provide ventilatory support in lower extremity or lower abdominal gynecology surgery.     

经皮肾镜取石术中采用压力控制容量保证通气模式对肺功能的影响

目的探讨压力控制容量保证通气模式(PCV-VG)在经皮肾镜取石术中对患者肺功能的影响。方法择期行经皮肾镜取石术患者40例,根据不同通气模式随机分为两组,每组20例,分别采用容量控制通气模式(V组)和PCV-VG(P组)。记录气管插管即刻(T0)、插管后15 min(T1)、30min(T2)、60min(T3)、120min(T4)的肺功能指标。结果 T2~T4时P组肺泡-动脉氧分压差(PA-aO2)、呼吸指数(RI)、吸气峰压(Ppk)、平台压(Pmean)明显低于V组(P0.05或P0.01),氧合指数(OI)、静态肺顺应性(Cst)明显高于V组(P0.05或P0.01)。结论 PCV-VG能够安全应用在经皮肾镜取石术,PCV-VG优于容量控制模式,术中有更低的气道压,血流动力学更平稳,更有利于对患者肺功能的保护。     

Opioid-induced respiratory depression is associated with increased tidal volume variability

BACKGROUND AND OBJECTIVE: mu-agonistic opioids cause concentration-dependent hypoventilation and increased irregularity of breathing. The aim was to quantify opioid-induced irregularity of breathing and to investigate its time-course during and after an opioid infusion, and its ability to predict the severity of respiratory depression. METHODS: Twenty-three patients breathing spontaneously via a continuous positive airway pressure (CPAP) mask received an intravenous (i.v.) infusion of alfentanil (2.3 microg kg(-1) min(-1), 14 patients) or pirinitramide (piritramide) (17.9 microg kg(-1) min(-1), nine patients) until either a cumulative dose of 70 microg kg(-1) for alfentanil or 500 microg kg(-1) for pirinitramide had been achieved or the infusion had to be stopped for safety reasons. Tidal volumes (VT) and minute ventilation were measured with an anaesthesia workstation. For every 20 breaths, the quartile coefficient was calculated (Qeff20V(T)). RESULTS: Both the decrease of minute volume and the increase of Qeff20V(T) during and after opioid infusion were highly significant (P < 0.001, ANOVA). Patients in which the alfentanil infusion had to be terminated prematurely had lower minute volumes (P = 0.002, t-test) and higher Qeff20V(T) (P = 0.034, t-test) than those who received the complete dose. Changes in the regularity of breathing measured as Qeff20V(T) parallel those of minute ventilation during and after opioid infusion. CONCLUSIONS: Opioids cause a more complicated disturbance of the control of respiration than a mere resetting to higher PCO2. Furthermore, Qeff20V(T) appears to predict the severity of opioid-induced respiratory depression.     

The frequency and timing of respiratory depression in 1524 postoperative patients treated with systemic or neuraxial morphine

STUDY OBJECTIVE: To describe the frequency and timing of intravenous patient-controlled analgesia (IV-PCA) or neuraxial morphine-induced postoperative respiratory depression. DESIGN: Audit of data captured by routine quality assurance of the acute pain protocols that were implemented by nurses performing routine postoperative care. SETTING: The surgical wards of a university-affiliated, 700-bed, tertiary hospital. PATIENTS AND INTERVENTIONS: In real time, the data of all patients enrolled into our Acute Pain Service (APS) were entered and stored in the APS database. Thereafter, patients who had received IV morphine via a PCA device or neuraxial morphine between January 1999 and December 2002 were isolated. From this subset, all patients in whom a respiratory rate (RR) less than 10 breaths per minute was recorded were retrieved. MEASUREMENTS AND MAIN RESULTS: From a total of 4500 patients, IV or neuraxial morphine was administered to 1524 patients. Eighteen (1.2%) cases of an RR less than 10 breaths per minute were recorded (13 patients, 4 patients, and 1 patient in the IV-PCA, daily epidural morphine, and single-dose intrathecal morphine groups, respectively). A direct correlation between intraoperative fentanyl administration and postoperative respiratory depression was demonstrated between the IV-PCA (P = 0.03) and epidural groups (P = 0.05). The time from IV-PCA initiation or last neuraxial morphine administration until the diagnosis of respiratory depression ranged between 2 hours and 31.26 hours and 2 hours and 12.15 hours, respectively. Ten (55.6%) patients received naloxone. CONCLUSION: Morphine-induced respiratory depression may occur at any time during the APS admission. However, the optimal frequency of intermittent RR monitoring is unknown. Furthermore, because multiple variables (age, sex, prior opioid administration, site of operation) may affect morphine-induced respiratory depression, further investigation must be performed to determine the ideal monitoring protocol.     

压力调节容积控制通气模式对合并慢性阻塞性肺疾病腹腔镜结直肠手术患者肺保护效应

目的:探讨压力调节容积控制通气（pressure-regulated volume control, PRVC）模式下肺保护性通气（lung-protective ventilation, LPV）对合并慢性阻塞性肺疾病（chronic obstructive pulmonary disease, COPD）腹腔镜结直...     

The significance of the initial respiratory parameters in assessing the severity of ARDS in children]

In adults, the course and outcome of the acquired respiratory distress syndrome (ARDS) are closely related to the initial respiratory situation. Respiratory indices are frequently used for prognostic purposes and hence for the institution of new techniques such as extracorporeal lung support. The validity of these indices to predict the outcome in pediatric ARDS patients has not been examined as yet. We studied respiratory indices in 69 pediatric ARDS patients. METHODS. Out of 69 pediatric ARDS patients with various underlying diseases (Table 1), we chose 21 with a paO2/FiO2 ratio less than 150 mm Hg at some point to test the prognostic significance of a respiratory severity index (RSI), i.e., mean airway pressure x alveolar-arterial pO2 difference (A-aDo2)/paO2, a respiratory index (RI), i.e., A-aDO2-paO2/paO2, and other respiratory parameters (Table 2). Postsurgical patients, patients with incurable diseases, clearly non-respiratory deaths, and those treated with extracorporeal membrane oxygenation were excluded. We looked for statistical differences between survivors and nonsurvivors and correlations between ventilator days, intensive care unit (ICU) days, and hospital days and these indices. RESULTS. We did not find a significant difference between all respiratory indices tested at admission to the ICU and 24 h later between survivors and nonsurvivors (Table 3). Nonsurvivors initially had significantly higher blood pressures and lower heart rates. Both RSI and RI were significantly correlated to days on the ventilator, days in the ICU, and days in the hospital (Table 4). Initial multiorgan failure was significantly more common in nonsurvivors. CONCLUSIONS. Initial lung dysfunction as indicated by respiratory indices does not predict the outcome in pediatric ARDS. The underlying disease, hemodynamic situation, and age have to be considered in relation to the degree of lung dysfunction to determine new therapeutic strategies such as extracorporeal support.     

Pulmonary acute respiratory distress syndrome: positive end-expiratory pressure titration needs stress index

Background

The heterogeneity of lung injury in pulmonary acute respiratory distress syndrome (ARDS) may have contributed to the greater response of hyperinflated area with positive end-expiratory pressure (PEEP). PEEP titrated by stress index can reduce the risk of alveolar hyperinflation in patients with pulmonary ARDS. The authors sought to investigate the effects of PEEP titrated by stress index on lung recruitment and protection after recruitment maneuver (RM) in pulmonary ARDS patients.

Materials and methods

Thirty patients with pulmonary ARDS were enrolled. After RM, PEEP was randomly set according to stress index, oxygenation, static pulmonary compliance (Cst), or lower inflection point (LIP) + 2 cmH₂O strategies. Recruitment volume, gas exchange, respiratory mechanics, and hemodynamic parameters were collected.

Results

PEEP titrated by stress index (15.1 ± 1.8 cmH₂O) was similar to the levels titrated by oxygenation (14.5 ± 2.9 cmH₂O), higher than that titrated by Cst (11.3 ± 2.5 cmH₂O) and LIP (12.9 ± 1.6 cmH₂O) (P < 0.05). Compared with baseline, PaO₂/FiO₂ and recruitment volume were significantly improved after PEEP titration with the four strategies (P < 0.05). PaO₂/FiO₂ and recruitment volume were similar when using PEEP titrated by stress index and oxygenation but higher than that titrated by Cst and LIP. Compared with baseline, lung compliance increased significantly when PEEP determined by Cst, but there was no difference of Cst in these four strategies. There was no influence of PEEP titration with the four strategies on hemodynamic parameters.

Conclusions

PEEP titration by stress index might be more beneficial for pulmonary ARDS patients after RM.     

不同呼吸频率设置对腹腔镜前列腺癌根治术患者术后认知功能的影响

目的 探讨不同呼吸参数设置对腹腔镜前列腺癌根治术患者术后认知功能的影响. 方法 采用前瞻性、双盲、随机对照研究设计.择期行腹腔镜下前列腺癌根治术患者100例,年龄65 ～75岁,按随机数字表法分为5组(每组20例):A组、B组、C组、D组、E组;A组分钟通气量(minute volume,MV) 100 ml/kg,呼吸频率(respiratory rate,RR)8次/min;B组MV 100 ml/kg,RR 10次/min;C组MV 100 ml/kg,RR 12次/min;D组MV 100 ml/kg,RR 14次/min;E组MV 100 ml/kg,RR 16次/min.分别于麻醉气腹前(Ta)、放气即刻(Tb)测患者动脉血二氧化碳分压(arterial blood partial pressure of carbon dioxide,PaCO2),于术前1 d(T0)、术后1 h(T1)、术后6 h(T2)、术后24 h(T3)时测血清S100β蛋白含量,并于T0、T2、T3、术后48 h(T4)、术后72 h(T5)、术后7 d(T6)时应用简易智能精神状态检查量表(mini-mental state examination,MMSE)评估认知功能. 结果 D组患者Th时PaCO2为(42.8±3.2) mmHg(1 mmHg=0.133 kPa),明显低于其余4组(P＜0.05);D组T2、T3时血清S100β蛋白分别为(330±25)、(300±26) mg/L,明显低于其余4组(P＜0.05);D组T2、T3时MMSE评分分别为(26.90±0.60)、(27.80±0.62)分,明显高于其余4组(P＜0.05). 结论 术中呼吸参数设置为MV 100 ml/kg、RR 14次/min时较为合理,可减轻腹腔镜前列腺癌根治术患者术后早期认知功能障碍.     

Augmented spontaneous breathing and pulmonary gas exchange during pneumoperitoneum

BACKGROUND AND OBJECTIVE: Ventilation of the lungs with positive end-expiratory pressure during pneumoperitoneum has been shown to improve the arterial partial pressure of oxygen. The implications of spontaneous breathing on pulmonary gas exchange remain unknown in this setting. We therefore sought to examine the influence of pressure-support ventilation with spontaneous breathing on gas exchange during simulated laparoscopy. METHODS: Ten pigs were subjected to pneumoperitoneum at a pressure of 15 cmH2O. Animals received, in a random order, pressure-support and pressure-controlled ventilation for 60 min per mode. Inert gas and haemodynamic measurements were performed before changing to a subsequent mode. RESULTS: Pressure-support ventilation was more efficient than pressure-controlled ventilation regarding perfusion of normal V(A)/Q lung areas (78 +/- 4% vs. 72 +/- 5%) (P < 0.05), alveolar-arterial partial pressure of oxygen difference (9.73 +/- 1.3 vs. 11.2 +/- 1.2 kPa) and arterial partial pressure of oxygen (14.93 +/- 1.6 vs. 13.7 +/- 2.0 kPa) (P < 0.05). CONCLUSIONS: Pressure-support ventilation resulted in significantly better gas exchange than pressure-controlled ventilation in this model of simulated laparoscopy.     

An adult system versus a Bain system: comparative ability to deliver minute ventilation to an infant lung model with pressure-limited ventilation

We compared the efficacy of an adult circle system versus a Bain system to deliver minute ventilation (V(E)) to an infant test lung model using pressure-limited ventilation. To simulate a wide variety of potential infant clinical states, V(E) was measured with two compliances: at peak inspiratory pressures (PIP) of 20, 30, 40, and 50 cm H2O and at respiratory rates (RR) of 20, 30, 40, and 50 breaths/min. Each measurement was made three times, and their average was used for analysis. Data were analyzed using the multiple regression technique. In both normal and low-compliance lung models, V(E) was nearly identical between adult circle and Bain systems (P = 0.67 for normal compliance model, P = 0.89 for low-compliance model). V(E) positively correlated with RR (P < 0.001), PIP (P < 0.001), and lung compliance (P < 0.001). Very high PIP or RR were required to deliver V(E) to the low-compliance lung model. The adult circle system is equivalent to the Bain system in its ability to ventilate an infant test lung over a wide range of RR, PIP, and two compliances during pressure-limited ventilation. V(E) is dependent of PIP, RR, and lung compliance. With low-compliance lungs, both systems require a high PIP. We conclude that both anesthetic systems deliver ventilation over a wide range of respiratory variables during pressure-limited ventilation in infants. IMPLICATIONS: We obtained results from this infant test lung study that indicate that either an adult circle breathing system or the Bain system can reliably deliver ventilation over a wide range of respiratory variables during pressure-limited ventilation in infants.     

Effects of pneumoperitoneum and reverse Trendelenburg position on cardiopulmonary function in morbidly obese patients receiving laparoscopic gastric banding

We prospectively evaluated the effects of pneumoperitoneum and reverse Trendelenburg position on cardiopulmonary function in 20 ASA physical status II-III morbidly obese patients (body mass index > 35 kg m(-2)) undergoing laparoscopic gastric banding. After general anaesthesia was induced, patients' lungs were ventilated using intermittent positive pressure ventilation (at measurement times, the following parameters were used: tidal volume 12 mL kg(-1) ideal body weight, respiratory rate of 12 bpm, an inspiratory to expiratory time ratio of 1:2). Haemodynamic variables, blood gas parameters, and lung/chest compliance were recorded: in the supine position, after induction of general anaesthesia (T0, baseline) and induction of pneumoperitoneum (T1); after placing the patient in a 25 degree reverse Trendelenburg position (T2); during the surgical time (T3); before deflating the abdomen (T4); after pneumoperitoneum resolution (T5), and before the end of anaesthesia, with the patient supine (T6). The PaO2, PaO2/FiO2 ratio, and lung/chest compliance decreased during the study. After the pneumoperitoneum had been resolved, lung/chest compliance but not oxygenation parameters returned to baseline values. The arterial to end-tidal CO2 tension difference progressively increased from 0.38+/-0.3 kPa (2.85+/-2.25 mmHg) (T0) to 0.63+/-0.3 kPa (4.73+/-2.25 mmHg) (T6). In morbidly obese patients, undergoing laparoscopic gastric banding, a CO2 pneumoperitoneum markedly affected gas exchange and lung/chest compliance, while positioning the patient in a 25 degree reverse Trendelenburg position had no beneficial effects.