液体复苏在高呼吸末正压通气导致的肺泡微循环障碍中的作用

目的明确高呼气末正压（PEEP）条件下肺泡微循环的变化情况以及液体复苏在高PEEP情况下对肺泡微循环的影响。 方法选用北京当地的15条健康成年杂种狗进行实验，分别观察基线（PEEP 5 cmH₂O，1 cmH₂O=0.098 kPa）、高PEEP（平均动脉压下降≥20 mmHg，1 mmHg=0.133 kPa）及液体复苏后的呼吸、系统循环及肺泡微循环情况，肺泡微循环利用旁流暗视野成像（SDF）技术进行观察、留取视频结果，线下利用AVA3.2软件进行分析，不同条件下的实验数据之间的差异利用Wilcoxon秩和检验进行分析。 结果高PEEP可导致中心静脉压（CVP）升高（P=0.001）及心输出量（CO）下降（P=0.002），肺泡微循环表现为总微血管数量（TVDa，P=0.036）、灌注血管数量（PVDa，P=0.002）、灌注血管比例（PPVa，P=0.003）、血流状态（MFIa，P=0.002）显著下降，肺泡周围毛细血管密度下降不明显（TVDs，P=0.319）；液体复苏恢复整体循环后，微循环参数均无显著改善。 结论过高的PEEP水平可导致肺泡微循环的显著恶化，通过液体复苏不能改善由此产生的微循环障碍。     

Fluctuating PEEP (F–PEEP) versus conventional PEEP in dogs with asymmetrical lung injury

Fluctuating PEEP (F-PEEP) is a newly developed PEEP in which end-expiratory pressure (EEP) is periodically changed within a certain range. In a dog model with unilateral lung injury induced by the introduction of hydrochloric acid, F-PEEP in which the EEP was periodically changed from 0.5 to 1.5 kPa at periods of 6 min, and conventional PEEP (C-PEEP) with an optimized EEP of 1.0 kPa, were each applied for 30 min. F-PEEP produced a significantly greater improvement of PaO2 and intrapulmonary shunt (QS/QT) than C-PEEP, and at the low EEP phase, the greatest improvement accompanied by an increased dynamic compliance and a large cardiac output was obtained. These results suggest that F-PEEP provides a useful mode of artificial ventilation for the treatment of unilateral lung injury.     

Effects of PEEP on extra vascular lung water and central blood volume in the dog

Twenty-four mongrel dogs were anaesthetized and ventilated mechanically in the supine position. Extravascular lung water (EVLW) and central blood volume (CBV) were measured with a double indicator (dye/cold) dilution technique. Both indicators were detected intravascularly in the aortic root with a fibreoptic thermistor catheter. Seven dogs ventilated with a positive end-expiratory pressure (PEEP) of 1.0 kPa (10 cmH2O) for a short period of time (less than 20 min) displayed no significant change in EVLW as measured with the indicator dilution technique (= EVLWi), while reductions were seen in both CBV (15%, P less than 0.01) and cardiac output (CO-thermodilution technique) (10%, P less than 0.05). Another seven dogs ventilated with a PEEP of 1.0 kPa for 8 h showed a gradual increase in EVLWi. After 8 h, a mean increase of 34% (P less than 0.01) was recorded, and the increase was also verified by post-mortem gravimetric determination of EVLW (= EVLWg), displaying an increase of 61% (P less than 0.01). In five dogs ventilated with zero end-expiratory pressure (ZEEP) for 8 h, no changes in EVLWi, CO, and CBV were observed, and EVLWg was mean 4.39 g/kg body weight (BW). Five additional dogs were sacrificed after 15 min of anaesthesia without catheterization and EVLWg was found to be 4.24 g/kg BW. It is concluded that EVLWi does not change measurably during ZEEP or short periods of PEEP. However, long periods (8 h) of PEEP result in elevated EVLWi values. Gravimetry supports these conclusions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Suppression of spontaneous breathing during high-frequency jet ventilation

Conditions which suppress spontaneous breathing activity during high-frequency jet ventilation (HFJV) were analysed in Yorkshire piglets under pentobarbital anesthesia. The highest P_aCO₂ at which the animals did not breathe against the ventilator (apnea point) was established during different patterns of ventilation, either by changing the minute volume or by adding CO₂ to the inspiratory gas. Arterial oxygen tension was maintained throughout the study above 80 mm Hg. An elevation of ventilatory rate increased the apnea point, suggesting a progressive suppression of spontaneous breathing. This suppression did not depend on the amount of lung stretch during insufflation, because at higher rates lower tidal volumes were used. Suppression also appeared to be independent of insufflatory flow, i.e. the velocity of lung stretch. At higher frequencies end-expiratory airway pressure (P_EE) increased and there appeared to be a positive relationship between the apnea point and P_EE. In a separate series this positive relationship between the apnea point and P_EE was confirmed. A hysteresis effect in this relationship, however, suggests that other than jet frequency, lung volume rather than positive end-expiratory pressure (PEEP) is a major determinant of suppression of spontaneous breathing activity during HFJV.     

利用压力-容积曲线选择呼气末正压治疗急性呼吸窘迫综合征

目的探讨利用压力-容积曲线选择呼气末正压(PEEP)对急性呼吸窘迫综合征(ARDS)患者肺力学、血流动力学及动脉血气参数的影响,并选择最佳PEEP范围.方法选择16例确诊为ARDS患者,根据压力-容积曲线,设下拐点压力为PLIP,设上拐点压力为PUIP.分别选择PEEP为0、PLIP/2、PLIP、(PLIP+PUIP)/2和PUIP,测量肺力学、血流动力学及动脉血气参数的变化.结果当PEEP为PLIP/2时,动脉血氧分压与吸入氧浓度比(PaO2/FiO2)及Cst虽然较未加用PEEP时有改善(P<0.05及P<0.01),但尚未达到正常水平;当PEEP为PLIP时,PaO2/FiO2及Cst较PLIP/2时有显著提高(P<0.01),接近正常范围;当PEEP为PUIP时,PaO2/FiO2较(PLIP+PUIP)/2时显著增高(P<0.01),但Cst较PLIP时反而有所降低(P<0.01),MAP下降(P<0.01),CVP升高(P<0.01),同时Pip增高(P<0.01).结论ARDS患者行呼吸机治疗时,在PLIP～PUIP之间可有效纠正低氧血症,而对血流动力学影响较小,可获得满意疗效.     

多发伤致急性呼吸窘迫综合征(ARDS)16例临床报告

为评价呼吸机及其他综合治疗在多发伤致急性呼吸窘迫综合征（ＡＲＤＳ）的价值,应用呼吸机和其他综合治疗多发伤致ＡＲＤＳ患者,并进行回顾性分析。呼吸机治疗可明显提高动脉氧分压,结合其他综合治疗可降低ＡＲＤＳ患者的死亡率。提示早期应用呼吸机和其他综合治疗,可提高ＡＲＤＳ的治愈率。     

Is proximal airway pressure a good reflection of peripheral airspace pressure in infants and children models under HFJV?

This expriimental study was carried out to determine if an alveolar positive end-expiratory pressure (PEEP) could occur during high frequency jet ventilation (HFJV) in infants, and if tracheal pressure is a good estimation of alveolar pressure.We used physical models simulating a 1.5 kg premature (P), a 3 kg newborn (N) and a 6 kg child (C) with normal compliance and normal resistance. Moreover, in the N model, we used two different resistances and lung compliance heterogeneity was studied in the P model. Pressure was measured simultaneously in the tube simulating trachea (Paw) and in the bottle simulating the lung (Palv). HFJV was performed either via an endotracheal tube (ETT) or via a long catheter as in laryngoscopy. The ratio of injection time upon cycle duration (Ti/Ttot) was 20% or 30%, jet frequency was altered from 150 to 300 min^–1 and the driving pressure was set as in clinical practice (0.5 and 0.6 bar).PEEP occurred mainly in N (1.1 to 3.2 cm H2O) and C models (0 to 3.5 cm H2O). It was inversely related to expiratory time (Te). The end-expiratory pressure drop between Palv and Paw (EEP) was higher in N and increased from 0.5 to 2 cm H2O with the shortening of Te and with airway resistances, i.e. the presence of ETT. In the heterogeneous model, PEEP and EEP were greater in the higher compliance alveolus.This study shows that the end-expiratory Palv is underestimated by end-expiratory Paw. This is particularly important in the presence of an heterogeneity of distribution in lung compliance. In this case the airway PEEP overestimates the PEEP in the lower compliance alveolus and underestimates the PEEP in the higher compliance alveolus.     

Positive end-expiratory pressure prevents atelectasis during general anaesthesia even in the presence of a high inspired oxygen concentration

BACKGROUND: General anaesthesia impairs the gas exchange in the lungs, and moderate desaturation (SaO2 86-90%) occurred in 50% of anaesthetised patients in a blinded pulse oximetry study. A high FiO2 might reduce the risk of hypoxaemia, but can also promote atelectasis. We hypothesised that a moderate positive end-expiratory pressure (PEEP) level of 10 cmH2O can prevent atelectasis during ventilation with an FiO2 = 1.0. METHODS: Atelectasis was evaluated by computed tomography (CT) in 13 ASA I-II patients undergoing elective surgery. CT scans were obtained before and 15 min after induction of anaesthesia. Then, recruitment of collapsed lung tissue was performed as a "vital capacity manoeuvre" (VCM, inspiration with Paw = 40 cmH2O for 15 s), and a CT scan was obtained at the end of the VCM. Thereafter, PEEP = 0 cmH2O was applied in group 1, and PEEP = 10 cmH2O in group 2. Additional CT scans were obtained after the VCM. Oxygenation was measured before and after the VCM. RESULTS: Atelectasis (> 1 cm2) was present in 12 of the 13 patients after induction of anaesthesia. At 5 and 10 min after the VCM, atelectasis was significantly smaller in group 2 than group 1 (P < 0.005). A significant inverse correlation was found between PaO2 and atelectasis. CONCLUSIONS: PEEP = 10 cmH2O reduced atelectasis formation after a VCM, when FiO2 = 1.0 was used. Thus, a VCM followed by PEEP = 10 cmH2O should be considered when patients are ventilated with a high FiO2 and gas exchange is impaired.     

小潮气量和呼吸暂停联合低呼气末正压通气在输尿管软镜手术中的应用*

目的探讨小潮气量和呼吸暂停联合低呼气末正压通气(PEEP)在输尿管软镜手术中的临床应用价值。方法选择2016年1月-2017年1月该院收治的肾结石行输尿管软镜钬激光碎石术患者80例,随机分为两组,各40例,对照组为小潮气量(6 ml/kg)联合呼吸暂停通气组,观察组为小潮气量(6 ml/kg)、呼吸暂停联合低PEEP(5 cm H2O)组,比较初次呼吸暂停前与恢复正常呼吸后1 min内,患者心率(HR)、血压变化、血气分析结果中动脉血二氧化碳分压(PaCO_2)、动脉血氧分压(PaO_2)变化及呼吸力学指标如:气道峰压(Ppeak)、平均气道压(Pmean)变化,并统计不同时间点(麻醉前、手术开始前、拔除气管导管时、拔除气管后30 min及术后24 h)肺泡-动脉氧分压差(A-aDO_2)、呼吸指数(RI)及肺动态顺应性20(CLdyn20)变化趋势。结果恢复呼吸后,观察组HR及平均动脉压(MAP)、Ppeak及Pmean与呼吸暂停前比较差异无统计学意义(P0.05),HR慢于恢复呼吸后对照组(P0.05),MAP低于恢复呼吸后对照组(P0.05),观察组Ppeak及Pmean均低于恢复呼吸后对照组(P0.05);观察组PaCO_2低于恢复呼吸后对照组(P0.05),PaO_2高于恢复呼吸后对照组(P0.05),拔除气管导管时、拔除气管后30 min及术后24 h,观察组A-aDO_2均明显低于对照组(P0.05),CLdyn20优于对照组(P0.05),RI大于对照组(P0.05)。结论针对输尿管软镜手术,术中行小潮气量(6 ml/kg)、呼吸暂停联合5 cm H2O低PEEP处理,在确保手术顺利进行前提下,可更好地维持患者生命体征平稳、血气分析结果正常,改善机体氧供需平衡,保护患者肺功能,促进患者术后恢复。     

保护性通气策略在老年髋关节手术全身麻醉期间的应用

目的探讨保护性通气策略应用于老年髋关节手术全身麻醉期间的临床有效性。方法选择择期老年全身麻醉下髋关节手术患者40例,随机分为:常规机械通气组(C组,20例):潮气量(Vt)=9 m L/kg理想体重(IBW),初始呼吸频率(f)=12次/min,吸气呼气时间比(I∶E)=1∶2;保护性肺通气组(P组,20例):Vt=7 m L/kg IBW,初始呼吸频率(f)=12次/min,I∶E=1∶2,呼气末正压设为6 cm H2O,每30分钟手法肺复张1次。术中吸入氧气浓度40%,调整呼吸频率维持PETCO235~45 mm Hg。分别于麻醉诱导前(T1)、气管插管后5 min(T2)、机械通气1.5 h(T3)、拔除气管导管后1 h(T4)、术后3 d(T5)观察记录HR、MAP、气道峰压(Ppeak)、气道平台压(Pmean),计算肺动态顺应性(Cdyn);血气分析仪测定Pa O2、Pa CO2和Hb;观察术后肺部并发症。结果C组术后拔除气管导管后1 h和术后3 d,Pa O2和氧合指数(Pa O2/Fi O2)均较术前降低(P<0.05),P组Pa O2和氧合指数在拔除气管导管后1 h较术前降低(P<0.05),但术后3 d无明显差异,且在机械通气1.5 h、拔除气管导管后1 h和术后3 d均较C组显著增高(P<0.05)。P组在机械通气期间Ppeak和Pmean均高于C组(P<0.05)。两组在机械通气1.5 h后Cdyn降低(P<0.05),但P组高于C组(P<0.05)。P组术后肺部并发症发生率明显低于C组(P<0.05)。结论肺保护策略能够有效提高老年髋关节手术患者肺顺应性,改善氧合,减少肺部并发症,利于呼吸功能恢复。