Positive end expiratory pressure and critical oxygenation during transport in ventilated patients

Transportation of patients critically dependent on positive end expiratory pressure (PEEP) can be problematic, as a patient of ours with adult respiratory distress syndrome (ARDS) and bilateral broncho-pleural fistulae demonstrated. He required intermittent positive pressure ventilation (IPPV) (Siemens 900C) with 100% O₂ and PEEP of 2 kPa to maintain his arterial O₂ saturation (SaO₂)>90%. Severe hypoxemia (SaO₂<75%) occurred on change to a portable ventilator (Oxylog, Dräger) with a PEEP valve (Ambu 20) at its expiratory port, despite adjusting the valve to 2 kPa, continuing use of 100% O₂, and varying the ventilatory pattern. The problem appeared due to loss of PEEP because of gas leak from the lungs via his intercostal catheters. It was solved by introducing a continuous O₂ flow of 51/min into the circuit between the Oxylog non-rebreathing valve and endotracheal tube. We used a model lung to investigate the effect of a gas leak from the lungs or circuit on the performance of the Oxylog IPPV/PEEP system. Lung compliance and ventilatory pattern were adjusted so that tidal volume (V_T)=0.61, peak inspiratory Airway pressure (PIP)=5 kPa, PEEP=1.5 kPa, and respiratory rate=10/min. A small leak was introduced from the lung resulting in a decrease in PIP, V_T, and PEEP. Adjustment of ventilator minute volume to restore PIP to 5 kPa failed to restore PEEP, airway pressure continuing to fall throughout the expiratory pause. PEEP was restored by providing a compensatory flow of O₂ of 5l/min to the system between the Oxylog nonrebreathing valve and the lung. We conclude that significant loss of PEEP can occur in patients with gas leaks from the lung when ventilators, such as the Oxylog, are used that do not provide a compensatory flow of gas into the lung during expiration and the expiratory pause. If the patient is critically dependent on PEEP this loss will result in severe hypoxemia.     

The Aachen MiniHLM--a miniaturized heart-lung machine for neonates with an integrated rotary blood pump

The operation of congenital heart defects in neonates often requires the use of heart-lung machines (HLMs) to provide perfusion and oxygenation. This is prevalently followed by serious complications inter alia caused by hemodilution and extrinsic blood contact surfaces. Thus, one goal of developing a HLM for neonates is the reduction of priming volume and contact surface. The currently available systems offer reasonable priming volumes for oxygenators, reservoirs, etc. However, the necessary tubing system contains the highest volumes within the whole system. This is due to the use of roller pumps; hence, the resulting placement of the complete HLM is between 1 and 2 m away from the operating table due to connective tubing between the components. Therefore, we pursued a novel approach for a miniaturized HLM (MiniHLM) by integrating all major system components in one single device. In particular, the MiniHLM is a HLM with the rotary blood pump centrically integrated into the oxygenator and a heat exchanger integrated into the cardiotomy reservoir which is directly connected to the pump inlet. Thus, tubing is only necessary between the patient and MiniHLM. A total priming volume of 102 mL (including arterial filter and a/v line) could be achieved. To validate the overall concept and the specific design we conducted several in vitro and in vivo test series. All tests confirm the novel concept of the MiniHLM. Its low priming volume and blood contact surface may significantly reduce known complications related to cardiopulmonary bypass in neonates (e.g., inflammatory reaction and capillary leak syndrome).     

PaO2/（FiO2×Paw）对急性呼吸窘迫综合征患者肺内分流的评估价值

目的探讨新的氧合指数即结合了平均气道压（Paw）的[PaO2/（FiO2×Paw）]能否较传统氧合指数（PaO2/FiO2）更准确地反映急性呼吸窘迫综合征（ARDS）患者的肺内分流（Qsp/Qt）。方法符合ARDS诊断标准的患者12例,气管插管呼吸机支持,采用肺保护性通气策略（潮气量6 mL/kg,呼吸频率16次/min,FiO260%）,留置Swan-Ganz导管,采用低流速法测定准静态肺压力-容积曲线,确定低位转折点压力（Pinf）。调整PEEP水平,观察血流动力学、呼吸力学的变化,分别留取外周及肺动脉血行血气分析,计算Qsp/Qt和PaO2/FiO2。结果递增的呼气末正压（PEEP）不足以显著改变ARDS患者的肺顺应性（Cst）、PaO2/FiO2及PaO2/（FiO2×Paw）（P0.05）。递增的PEEP对Qsp/Qt改变不明显（P0.05）。检验Qsp/Qt与PaO2/（FiO2×Paw）及Qsp/Qt与PaO2/FiO2的相关系数,Δz=0.571,无显著性差异（P0.05）。影响ARDS患者的Qsp/Qt和PaO2/FiO2的参数不是Paw,而是Cst。结论 PaO2/（FiO2×Paw）与PaO2/FiO2相比,两者对ARDS患者肺内分流的评估价值相当。     

无创机械通气用于重症监护室急性肺损伤患者的临床观察

目的:观察急性肺损伤患者早期给予无创正压机械通气治疗的临床效果。方法:选择31例早期急性肺损伤患者,给予无创正压机械通气治疗,S/T通气模式,呼吸机参数设置为EPAP3-8cmH2O,IPAP不超过18 cmH2O,潮气量6～8ml/kg,连续动态监测生命体征,采取不同时间段的动脉血气,计算氧合指数并记录。结果:26例急性肺损伤患者临床症状明显改善,并逐渐试脱机成功;5例改行有创机械通气治疗。结论:无创正压机械通气治疗早期急性肺损伤患者临床效果肯定。     

Congenital diaphragmatic hernia: prognostic indices in the fetal endoluminal tracheal occlusion era

Introduction

Management of congenital diaphragmatic hernia (CDH) in the UK now includes the possibility of fetal endoluminal tracheal occlusion (FETO) for poor prognosis fetuses. The objective of this study was to investigate the value of variables previously thought prognostic in the FETO era.

Methods

A retrospective single-centre study was performed of all infants with CDH born between January 1994 and December 2007. Fetal endoluminal tracheal occlusion was available and had been used with parental consent for fetuses with lung-to-head ratio (LHR) of 1.0 or less and a liver-up position from 2002. Univariate analysis was used to predict survival (to leave hospital) using both prenatal (eg, polyhydramnios) and perinatal variables [eg, best oxygenation index on day 1, or BOI (d1)] and their dependence tested in a logistic regression model. Data were quoted as medians (range). P < .05 was regarded as significant.

Results

Eighty-six infants with CDH (1994-2002, n = 35 and 2002-2007, n = 51 “FETO era”) were studied. Successful FETO intervention was performed in 31 infants.Univariate analysis showed liver position, birth weight, LHR, and BOI (d1) were significant prognostic predictors (all P < .05); however, only BOI (d1) retained significance using logistic regression analysis (odds ratio, 21; 95% confidence interval, 6-74; P < .001). Best oxygenation index on day 1 was then used as a surrogate marker for outcome to test the relationship with LHR (available since 2002) and showed a significant inverse correlation (r_s = −0.5; P < .001). There was no difference in median BOI (d1) between the FETO group and all those treated expectantly (40 [34-1046] vs 59 (23-581); P = .3].

Conclusion

Best oxygenation index on day 1 is the best early postnatal predictor of survival. The more recently evaluated prenatal index, LHR, has an observable relationship with BOI (d1) when it is used as a surrogate marker of outcome.     

Video-Assisted Versus Conventional Tracheal Intubation in Morbidly Obese Patients

Background  We compared tracheal intubation characteristics and arterial oxygenation quality during airway management of morbidly obese patients whose trachea was intubated under video assistance with the LMA CTrach™ (SEBAC, Pantin, France) or the Airtraq™ laryngoscope (VYGON, écouen, France) with that of the conventional Macintosh laryngoscope. Methods  After standardized induction of anesthesia, 318 morbidly obese patients scheduled for elective morbid obesity surgery received tracheal intubation with the LMA CTrach™, the Airtraq™ laryngoscope, or the conventional Macintosh laryngoscope. Duration of apnea, time to tracheal intubation, and oxygenation quality during airway management were compared between the LMA CTrach™ and the laryngoscope groups. Results  Patients’ characteristics were similar in the three groups. The success rate for tracheal intubation was 100% with the LMA CTrach™ and the Airtraq™ laryngoscope. One patient of the Macintosh laryngoscope group received LMA CTrach™ intubation because of early arterial oxygen desaturation associated with unstable facemask ventilation. The duration of apnea was shorter with the LMA CTrach™ than that of the Airtraq™ laryngoscope and the Macintosh laryngoscope. The duration tracheal intubation was shorter with the Airtraq™ laryngoscope than with the Macintosh laryngoscopes and the LMA CTrach™. During airway management, arterial oxygenation was of better quality with the LMA CTrach™ and the Airtraq™ laryngoscope than that of the Macintosh laryngoscope. Conclusion  Because LMA CTrach™ promoted short apnea time and the Airtraq™ laryngoscope allowed early definitive airway, both video-assisted tracheal intubation devices prevented most serious arterial oxygenation desaturation evidenced during tracheal intubation of morbidly obese patients with the conventional Macintosh laryngoscope. Support was provided solely from department sources. LMA and PRODOL Companies promoted material support for the airways.     

Linking nucleus accumbens dopamine and blood oxygenation

RATIONALE: Animal research suggests that anticipation of reward can elicit dopamine release in the nucleus accumbens (NAcc). Human functional magnetic resonance imaging (FMRI) research further suggests that reward anticipation can increase local blood oxygen level dependent (BOLD) signal in the NAcc. However, the physiological relationship between dopamine release and BOLD signal increases in the NAcc has not yet been established. OBJECTIVES: This review considers pharmacological MRI (phMRI) evidence for a directional relationship between NAcc dopamine release and BOLD signal, as well as implications for human psychopathological symptoms. RESULTS: Accumulating phMRI evidence supports a simple model in which NAcc dopamine release activates postsynaptic D1 receptors, which changes postsynaptic membrane potential, eventually increasing local BOLD signal. This continuing influence can change on a second-to-second basis. CONCLUSIONS: Dopamine release in the NAcc appears to increase local BOLD signal via agonism of postsynaptic D1 receptors. Such a physiological mechanism implies that FMRI may be used to track symptoms related to NAcc dopaminergic dysregulation in psychiatric disorders including schizophrenia and attention deficit/hyperactivity disorder.     

Successful treatment of a patient with ARDS after pneumonectomy using high-frequency oscillatory ventilation

High frequency oscillatory ventilation (HFOV) was used in a patient who developed the acute respiratory distress syndrome 5 days following a right pneumonectomy for bronchogenic carcinoma. When conventional pressure-controlled ventilation failed to maintain adequate oxygenation, HFOV dramatically improved oxygenation within the first few hours of therapy. Pulmonary function and gas exchange recovered during a 10-day period of HFOV. No negative side effects were observed. Early use of HFOV may be a beneficial ventilation strategy for adults with acute pulmonary failure, even in the postoperative period after lung resection. Received: 3 February 1999/Final revision received: 2 June 1999/Accepted: 1 July 1999     

重型脑外伤患者脑脊液内皮素含量变化及高压氧治疗作用

本文报告３Ｏ例重型脑外伤病人脑脊液内皮素（ＥＴ）含量变化。１４例加用高压氧治疗，结果显示高压氧治疗能降低脑脊液ＥＴ含量、减轻脑水肿、降低颅内压、缩短病人昏迷时间和降低了死亡率。