The Influence of Ventilation Mode (Spontaneous Ventilation,IPPV and PEEP) on Cardiopulmonary Parameters in Sevoflurane Anaesthetized Dogs

The purpose of this study was to investigate the cardiopulmonary influences of sevoflurane in oxygen at two anaesthetic concentrations (1.5 and 2 MAC) during spontaneous and controlled ventilation in dogs. After premedication with fentanyl–droperidol (5 μg/kg and 0.25 mg/kg intramuscularly) and induction with propofol (6 mg/kg intravenously) six dogs were anaesthetized for 3 h. Three types of ventilation were compared: spontaneous ventilation (SpV), intermittent positive pressure ventilation (IPPV), and positive end expiratory pressure ventilation (PEEP, 5 cm H₂O). Heart rate, haemoglobin oxygen saturation, arterial blood pressures, right atrial and pulmonary arterial pressures, pulmonary capillary wedge pressure and cardiac output were measured. End tidal CO₂%, inspiratory oxygen fraction, respiration rate and tidal volume were recorded using a multi‐gas analyser and a respirometer. Acid–base and blood gas analyses were performed. Cardiac index, stroke volume, stroke index, systemic and pulmonary vascular resistance, left and right ventricular stroke work index were calculated. Increasing the MAC value during sevoflurane anaesthesia with spontaneous ventilation induced a marked cardiopulmonary depression; on the other hand, heart rate increased significantly, but the increases were not clinically relevant. The influences of artificial respiration on cardiopulmonary parameters during 1.5 MAC sevoflurane anaesthesia were minimal. In contrast, PEEP ventilation during 2 MAC concentration had more pronounced negative influences, especially on right cardiac parameters. In conclusion, at 1.5 MAC, a surgical anaesthesia level, sevoflurane can be used safely in healthy dogs during spontaneous and controlled ventilation (IPPV and PEEP of 5 cm H₂O).     

Cardiorespiratory Effects of Automatic Tube Compensation during Airway Pressure Release Ventilation in Patients with Acute Lung Injury

Background: Spontaneous breaths during airway pressure release ventilation (APRV) have to overcome the resistance of the artificial airway. Automatic tube compensation provides ventilatory assistance by increasing airway pressure during inspiration and lowering airway pressure during expiration, thereby compensating for resistance of the artificial airway. The authors studied if APRV with automatic tube compensation reduces the inspiratory effort without compromising cardiovascular function, end-expiratory lung volume, and gas exchange in patients with acute lung injury.

Methods: Fourteen patients with acute lung injury were breathing spontaneously during APRV with or without automatic tube compensation in random order. Airway pressure, esophageal and abdominal pressure, and gas flow were continuously measured, and tracheal pressure was estimated. Trans-diaphragmatic pressure time product was calculated. End-expiratory lung volume was determined by nitrogen washout. The validity of the tracheal pressure calculation was investigated in seven healthy ventilated pigs.

Results: Automatic tube compensation during APRV increased airway pressure amplitude from 7.7 +/- 1.9 to 11.3 +/- 3.1 cm H2O (mean +/- SD;P < 0.05) while decreasing trans-diaphragmatic pressure time product from 45 +/- 27 to 27 +/- 15 cm H2O [middle dot] s-1 [middle dot] min-1 (P < 0.05), whereas tracheal pressure am-plitude remained essentially unchanged (10.3 +/- 3.5 vs. 10.1 +/- 3.5 cm H2O). Minute ventilation increased from 10.4 +/- 1.6 to 11.4 +/- 1.5 l/min (P < 0.001), decreasing arterial carbon dioxide tension from 52 +/- 9 to 47 +/- 6 mmHg (P < 0.05) without affecting arterial blood oxygenation or cardiovascular function. End-expiratory lung volume increased from 2,806 +/- 991 to 3,009 +/- 994 ml (P < 0.05). Analysis of tracheal pressure-time curves indicated nonideal regulation of the dynamic pressure support during automatic tube compensation as provided by a standard ventilator.     

Continuous Positive Airway Pressure During Mechanical and Spontaneous Ventilation Effects on Central Haemodynamics and Oxygen Transport

The effect of continuous positive airway pressure during continuous mechanical (CMV + PEEP) and spontaneous (CPAP) ventilation on central haemodynamics and systemic oxygen transport was studied in 10 male patients who had undergone aortocoronary bypass graft operation 18 h earlier. With the change from CMV + PEEP 5 cmH2O to CPAP 5 cmH2O, cardiac index was found to increase from 2.58 +/- 0.44 (s.e. mean) to 2.88 +/- 0.19 l/min/m2 (P less than 0.005), and systemic oxygen transport improved from 8.5 +/- 0.6 to 9.5 +/- 1.0 ml/min/kg (P less than 0.05). Arterial oxygen tension and content did not change, but mixed venous blood oxygen tension increased from 3.5 +/- 0.2 to 4.2 +/- 0.2 kPa (P less than 0.005), reflecting the increase in cardiac output. Arteriovenous oxygen content difference decreased from 4.6 +/- 0.5 (CMV + PEEP) to 3.6 +/- 0.2 (CPAP) ml/100 ml (P less than 0.05), while total oxygen consumption remained unchanged. Mean systemic arterial pressure was found to increase from 10.8 +/- 0.4 to 11.6 +/- 0.4 kPa (P less than 0.05) and mean pulmonary arterial pressure changed from 2.2 +/- 0.1 to 2.4 +/- 0.1 kPa (P less than 0.05). Right atrial and pulmonary capillary wedge pressures did not change. Our observations suggest that, in terms of central haemodynamics and tissue oxygen supply, CPAP offers a noteworthy alternative weaning method and an alternative to CMV + PEEP in cases where therapy is prolonged and the patient is able to breathe spontaneously.     

间断肺通气对体外循环肺损伤的保护作用

目的研究间断肺通气对体外循环(CPB)肺损伤的保护作用,并探讨其机制。方法将24例风湿性心脏病患者采用随机数字表法分为两组,处理组(n=13)CPB期间每5min间断肺通气一次;对照组(n=11)CPB期间不通气。所有患者均在术前留取血液标本,术后2h行支气管肺泡灌洗,分别测定支气管肺泡灌洗液(BALF)中的中性粒细胞、总蛋白(TP)、肿瘤坏死因子-α(TNF-α)含量、血清总蛋白以及术前、CPB后1h、4h肺氧合指数(OI)。结果处理组BALF中的中性粒细胞、TP、TNF-α含量较对照组显著降低(P<0.01,P=0.02,0.02),CPB后OI较对照组显著降低(P<0.05);两组CPB后1h、4h其OI均较同组CPB前显著增高(P<0.05)。结论间断肺通气可通过减少白细胞与血管内皮的黏附,减轻肺部炎症反应、内皮细胞损伤等,对CPB所致的肺损伤有保护作用。     

Effects of Ventilation with Large Tidal Volumes or Positive End-Expiratory Pressure on Cardiorespiratory Function in Anesthetized Obese Patients

The cardiorespiratory effects of ventilation with large tidal volumes (LTV) or positive end-expiratory pressure (PEEP) were investigated in 10 extremely obese patients during anesthesia for a jejuno-ileal by-pass operation.
Elevation of the tidal volume by 35% and insertion of a dead space (LTV-group: five patients) or applying a PEEP of 1.0 kPa (PEEP-group: five patients) resulted in significant rises in arterial oxygen tensions (Pa_o2) of 87.4% and 72.4%, respectively. The alveolar-arterial oxygen tension differences (P(a-a)_o2) decreased by 29.2% in the LTV-group and 25.6% in the PEEP-group when compared to control values. No significant differences were found between the groups in Pa_o2 or P(A-a)o₂.
PEEP-ventilation caused a maximal increase in compliance of 42.6%, but there was an increase of only 20.8% in the LTV-group.
Stroke index (the impedance cardiography method) decreased by 19.7% in the PEEP-group, whereas no changes occurred in the LTV-group. The decrease in stroke index was probably due to a reduction in venous return, as reflected in the systolic time intervals. In the PEEP-group a prolongation of the pre-ejection period (PEP) was observed, causing an increase in the PEP/LVET-ratio of 41.2%. A 13.8% increase in PEP/LVET-ratio was found in the LTV-group.
In spite of the increased arterial oxygen contents, no improvements in arterial oxygen delivery were found in either of the groups.     

Anti‐nociceptive and Sedative Effects of Sufentanil Long Acting during and after Sevoflurane Anaesthesia in Dogs

The purpose of the present study was to determine the most effective time interval between the administration of sufentanil long acting (LA) and the induction of sevoflurane anaesthesia in dogs. The occurrence of sedation, analgesia and other marked side‐effects were evaluated in addition to the possible dosage‐reducing effect of sufentanil on sevoflurane in dogs. Forty clinically normal beagles aged 1–2 years and weighing between 8.4 and 13.6 kg were included. Two control groups were used: one group of dogs (A) received sufentanil LA (50 μg/kg i.m.) and a second group (B) the sufentanil vehicle followed by standard inhalation anaesthesia of 90 min. After premedication with sufentanil LA immediately before (C⁰), 15 min (D¹⁵) or 30 min (E³⁰) prior to induction with thiopental (i.v.) the dogs were anaesthetized for 90 min with sevoflurane in oxygen. Pain and sedation scores were evaluated every 10 min during sevoflurane anaesthesia and at 2 (T₁₂₀), 4 (T₂₄₀) and 24 h (T₁₄₄₀) after initiation of anaesthesia. The occurrence of adverse reactions such as hypothermia, lateral recumbency, ataxia, noise sensitivity, vomiting, defaecation, salivation, nystagmus and excitation was observed at the same time‐points. During the recovery period pain scores were lower and sedation scores higher in the sufentanil LA groups. In many dogs acceptable pain and sedation scores persisted during 24 h. Several dogs showed ataxia, lateral recumbency, arousal on auditory stimulation, defaecation, salivation and excitation at several time‐points after sufentanil LA administration. Sufentanil LA in addition to sevoflurane anaesthesia offered beneficial dosage‐reducing analgesic effects up to 69.8% for thiopental and 78.3% for sevoflurane; although several typical opioid side‐effects occurred. To achieve this advantageous dosage‐reducing effect 15 min should be respected between sufentanil LA administration and induction of sevoflurane anaesthesia.     

七氟醚对神经外科手术患者颅内压的影响

目的 :观察静吸复合麻醉下 0 5、1 0MAC七氟醚对颅内压的影响。方法 :选颅内顺应性正常的择期行垂体瘤或颅咽管瘤手术患者 16例 ,随机分为两组 :A组用咪唑安定 +芬太尼 + 0 5MAC七氟醚 ;B组咪唑安定 +芬太尼+ 1 0MAC七氟醚。于L3～ 4穿刺至蛛网膜下腔以监测腰部脑脊液压 (ISP)。麻醉诱导采用芬太尼 咪唑安定 阿曲库铵。气管内插管后静脉泵入咪唑安定 0 1mg·kg-1·h-1、阿曲库铵 0 5mg·kg-1·h-1。插管后稳定 3 0分钟开始吸入七氟醚。分别于麻醉诱导前、吸入七氟醚前、达预定呼气末七氟醚浓度即刻、5、10、15、2 0、3 0分钟时观察并记录各监测指标。结果 :吸入 0 5MAC七氟醚后颅内压逐渐上升 ,达预定浓度后 3 0分钟上升 11 2 % ;吸入 1 0MAC七氟醚后颅内压首先呈显著性下降 ,15分钟后逐渐回复至基础水平。结论 :0 5、1 0MAC七氟醚可安全用于神经外科颅内顺应性正常的患者。     

Comparison of Sevoflurane with Isoflurane for Rapid Mask Induction in Midazolam and Butorphanol‐sedated Dogs

Rapid mask induction can be a useful induction technique for veterinary patients, although it is often accompanied by exaggerated excitement responses in unpremedicated animals (Mutoh et al.: Jpn. J. Vet. Anesth. Surg. 26, 109–116; J. Vet. Med. Sci. 57, 1007–1013; J. Vet. Med. Sci. 57, 1121–1124; 1995). The aim of this study was to compare sevoflurane with isoflurane for rapid mask induction in six dogs sedated by a combination of midazolam (0.1 mg/kg) and butorphanol (0.2 mg/kg). Induction with sevoflurane (5 %, 2.4 minimum alveolar concentration [MAC]) in O₂ resulted in shorter time to loss of the palpebral reflex, negative tail clamp response, and successful intubation than with isoflurane (3 %, 2.4 MAC) in O₂. There were no changes in heart rate or mean arterial blood pressure during induction with sevoflurane, whereas an increase in heart rate was observed in dogs induced with isoflurane. A decrease in respiratory rate compared with the pre‐induction rate was observed during induction, and associated mild respiratory acidosis, characterized by an increase in arterial PCO₂, was measured at the end of the induction period in both induction groups. None of the animals had episodes of induction‐related complications. These results suggest that both sevoflurane and isoflurane produce a smooth onset of induction in midazolam and butorphanol‐sedated dogs. Sevoflurane is a more suitable for rapid mask induction than isoflurane since it provides faster induction associated with a lower blood/gas partition coefficient.     

开胸术中中心静脉压变化及其与胸内压的关系

目的探讨开胸手术患者开胸前、后中心静脉压(CVP)与胸内压(IP)的变化及其相互关系,为胸科手术患者术中输血、输液提供指导.方法选择20例择期开胸手术患者,于开胸及关胸前、后分别测定CVP和IP,并分析CVP与IP变化的相关性.结果开胸后,患者CVP平均上升(4.75±1.74)cmH2O(P＜0.01),关胸并恢复胸腔负压后CVP平均下降(4.65±1.48)cmH2O(P＜0.01);开胸后CVP上升值与IP变化呈正相关(r＝0.88,P＜0.01).结论剖胸后CVP应维持较高水平,否则表明患者血容量可能不足.     

Short-term Cardiorespiratory Effects of Proportional Assist and Pressure-support Ventilation in Patients with Acute Lung Injury/Acute Respiratory Distress Syndrome

Background: Recent data indicate that assisted modes of mechanical ventilation improve pulmonary gas exchange in patients with acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). Proportional assist ventilation (PAV) is a new mode of support that amplifies the ventilatory output of the patient effort and improves patient-ventilator synchrony. It is not known whether this mode may be used in patients with ALI/ARDS. The aim of this study was to compare the effects of PAV and pressure-support ventilation on breathing pattern, hemodynamics, and gas exchange in a homogenous group of patients with ALI/ARDS due to sepsis.

Methods: Twelve mechanically ventilated patients with ALI/ARDS (mean ratio of partial pressure of arterial oxygen to fractional concentration of oxygen 190 +/- 49 mmHg) were prospectively studied. Patients received pressure-support ventilation and PAV in random order for 30 min while maintaining mean airway pressure constant. With both modes, the level of applied positive end-expiratory pressure (7.1 +/- 2.1 cm H2O) was kept unchanged throughout. At the end of each study period, cardiorespiratory data were obtained, and dead space to tidal volume ratio was measured.

Results: With both modes, none of the patients exhibited clinical signs of distress. With PAV, breathing frequency and cardiac index were slightly but significantly higher than the corresponding values with pressure-support ventilation (24.5 +/- 6.9 vs. 21.4 +/- 6.9 breaths/min and 4.4 +/- 1.6 vs. 4.1 +/- 1.3 l [middle dot] min-1 [middle dot] m-2, respectively). None of the other parameters differ significantly between modes.     

The Impact of Pretransplant Mechanical Ventilation on Short‐ and Long‐Term Survival After Lung Transplantation

Lung transplantation in mechanically ventilated (MV) patients has been associated with decreased posttransplant survival. Under the Lung Allocation Score (LAS) system, patients at greatest risk of death on the waiting list, particularly those requiring MV, are prioritized for lung allocation. We evaluated whether pretransplant MV is associated with poorer posttransplant survival in the LAS era. Using a national registry, we analyzed all adults undergoing lung transplantation in the United States from 2005 to 2010. Propensity scoring identified nonventilated matched referents for 419 subjects requiring MV at the time of transplantation. Survival was evaluated using Kaplan–Meier methods. Risk of death was estimated by hazard ratios employing time‐dependent covariates. We found that pretransplant MV was associated with decreased overall survival after lung transplantation. In the first 6 months posttransplant, ventilated subjects had a twofold higher risk of death compared to nonventilated subjects. However, after 6 months posttransplant, survival did not differ by MV status. We also found that pretransplant MV was not associated with decreased survival in noncystic fibrosis obstructive lung diseases. These results suggest that under the LAS, pretransplant MV is associated with poorer short‐term survival posttransplant. Notably, the increased risk of death appears to be strongest the early posttransplant period and limited to certain pretransplant diagnoses.     

Effects of Spontaneous Breathing during Airway Pressure Release Ventilation on Intestinal Blood Flow in Experimental Lung Injury

Background: In critical illness, the gut is susceptible to hypoperfusion and hypoxia. Positive-pressure ventilation can affect systemic hemodynamics and regional blood flow distribution, with potentially deleterious effects on the intestinal circulation. The authors hypothesized that spontaneous breathing (SB) with airway pressure release ventilation (APRV) provides better systemic and intestinal blood flow than APRV without SB.

Methods: Twelve pigs with oleic acid-induced lung injury received APRV with and without SB. When SB was abolished, either the tidal volume or the ventilator rate was increased to maintain pH and arterial carbon dioxide tension constant as compared to APRV with SB. Systemic hemodynamics were determined by double indicator dilution. Blood flow to the intestinal mucosa-submucosa and muscularis-serosa was measured using colored microspheres.

Results: Systemic blood flow increased during APRV with SB. During APRV with SB, mucosal-submucosal blood flow (ml [middle dot] g-1 [middle dot] min-1) was 0.39 +/- 0.21 in the stomach, 0.76 +/- 0.35 in the duodenum, 0.71 +/- 0.35 in the jejunum, 0.71 +/- 0.59 in the ileum, and 0.63 +/- 0.21 in the colon. During APRV without SB and high tidal volumes, it decreased to 0.19 +/- 0.03 in the stomach, 0.42 +/- 0.21 in the duodenum, 0.37 +/- 0.10 in the jejunum, 0.3 +/- 0.14 in the ileum, and 0.41 +/- 0.14 in the colon (P < 0.001, respectively). During APRV without SB and low tidal volumes, the respective mucosal-submucosal blood flows decreased to 0.24 +/- 0.10 (P < 0.01), 0.54 +/- 0.21 (P < 0.05), 0.48 +/- 0.17 (P < 0.01), 0.43 +/- 0.21 (P < 0.01), and 0.50 +/- 0.17 (P < 0.001) as compared to APRV with SB. Muscularis-serosal perfusion decreased during full ventilatory support with high tidal volumes in comparison with APRV with SB.     

Effects of Mechanical Ventilation and Halothane on Pulmonary Serotonin Removal in Dogs

The type of anesthesia and anesthetic drug used may significantly change the capacity of the lungs to regulate blood concentrations of serotonin. This study was performed to examine the possible effect of mechanical ventilation and 1% halothane in ventilation air on pulmonary serotonin removal using C14-serotonin in eight dogs. Mechanical ventilation significantly increased serotonin removal when compared with spontaneous ventilation during anesthesia, the removal rates being 74.4% and 48.4%, respectively. The 1% halothane concentration in ventilation air did not significantly affect the pulmonary serotonin removal. It was concluded that mechanical ventilation protects the organism against harmful cardiovascular effects of serotonin during anesthesia.     

单肺正压通气控制支气管扩张大咯血的护理策略

目的 探讨单肺正压机械通气在支气管扩张大咯血救治中的作用及其护理策略.方法 对26例符合支气管扩张大咯血诊断标准且不具备手术适应证的病例,在双腔管气管插管后实行单肺正压机械通气.在常规和Swan-Ganz导管监测下,设置不同的正性压力支持(PPS)和呼气末正压(PEEP),增加气道压力,观测咯血量和心肺功能并采取相应的临床护理措施.结果 气道压力增加后咯血量明显减少,两者呈显著负相关(P＜0.01).PPS≤15 cmH2O和PEEP≤7 cmH2O时,心排血指数(CI)和射血分数(EF)随着气道压力升高而增加;而当PPS≥20 cmH2O和PEEP≥9 cmH2O时,上述指标随着气道压力的升高而下降.结论 机械通气增加气道压有明显的止血作用,但需在气道压力、止血和心肺功能三者间维持动态平衡.     

单肺正压通气控制支气管扩张大咯血的护理策略

目的：探讨单肺正压机械通气在支气管扩张大咯血救治中的作用及其护理策略。方法：对26例符合支气管扩张大咯血诊断标准且不具备手术适应证的病例，在5K腔管气管插管后实行单肺正压机械通气。在常规和Swan-Ganz导管监测下，设置不同的正性压力支持（PPS）和呼气末正压（PEEP），增加气道压力，观测咯血量和心肺功能并采取相应的临床护理措施。结果：气道压力增加后咯血量明显减少，两者呈显著负相关（P〈0．01）。PPS≤15cmH2O和PEEP≤7cmH2O时，心排血指数（CI）和射血分数（EF）随着气道压力升高而增加；而当PPS≥20cmH2O和PEEP≥9cmH2O时，上述指标随着气道压力的升高而下降。结论：机械通气增加气道压有明显的止血作用，但需在气道压力、止血和心肺功能三者间维持动态平衡。     

比较七氟醚、异氟醚和安氟醚对颅内压的影响

目的：为了观察七氟醚对颅内压的影响。方法：选择２４例颅内肿胶病人,测定七氟醚麻醉的时颅内压变化并与异氟醚和安氟醚进行比较。术前用药、麻醉诱导及维持的静脉用药相同。于Ｌ３－４穿刺蛛网膜睛腔测脑脊液压（代表颅内压,ＩＣＰ）。依吸入药不同随机分为七的氟醚（Ｓ）组,异氟醚（１）组和安氟醚（Ｅ）组,监测ＢＰ、ＭＡＰ、ＥＣＧ、ＳｐＯ２、ＰＥＴ、ＣＯ２和ＭＡＣ,调整ＶＴ和ＲＲａＣＯ２维持在４～４．６６ＫＰＡ。三     

Time-of-Day Effects on EMG Parameters During the Wingate Test in Boys

In boys, muscle power and strength fluctuate with time-of-day with morning nadirs and afternoon maximum values. However, the exact underlying mechanisms of this daily variation are not studied yet. Thus, the purpose of this study was to examine the time-of-day effects on electromyographic (EMG) parameters changes during a Wingate test in boys. Twenty-two boys performed a 30-s Wingate test (measurement of muscle power and fatigue) at 07:00 and 17:00-h on separate days. Surface EMG activity was recorded in the Vastus lateralis, rectus femoris and vastus medialis muscles throughout the test and analyzed over a 5-s span. The root-mean-square (RMS) and mean-power-frequency (MPF) were calculated. Neuromuscular efficiency (NME) was estimated from the ratio of power to RMS. Muscle power (8.22 ± 0.92 vs. 8.75 ± 0.99 W·kg^-1 for peak power and 6.96 ± 0. 72 vs. 7.31 ± 0.77 W·kg^-1 for mean power, p < 0.001) and fatigue (30.27 ± 7.98 vs. 34.5 ± 10. 15 %, p < 0.05) during the Wingate test increased significantly from morning to evening. Likewise, MPF (102.14 ± 18.15 vs. 92.38 ± 12.39 Hz during the first 5-s, p < 0.001) and NME (4.78 ± 1.7 vs. 3.88 ± 0.79 W·mV^-1 during the first 5-s, p < 0.001) were higher in the evening than the morning; but no significant time-of-day effect was noticed for RMS. Taken together, these results suggest that peripheral mechanisms are more likely the cause of the child’s diurnal variations of muscle power and fatigue during the Wingate test.

Key points

• In boys, performances during the Wingate test fluctuate with the time-of-day.
• MPF and NME are higher in the evening during the Wingate cycling test.
• RMS is unaffected by the time-of-day.
• The evening improvement in muscle power and fatigue is due to an enhancement of the muscle contractile properties.

Key words: Dkwdurnal variation, muscle power, muscle fatigue, electromyography, pre-pubertal     

The Influence of Airway Closure Technique for Right Pneumonectomy on Wall Tension During Positive Pressure Ventilation: An Experimental Study

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