下胸段硬膜外阻滞在单肺通气期间对肺内分流的影响

目的探讨全麻下下胸段硬膜外阻滞对单肺通气期间肺内分流(Qs/Qt)的影响。方法术中需行单肺通气的30例择期开胸手术患者,ASAⅡ～Ⅲ,随机分为全麻组(GA组,n=15),全麻复合下胸段硬膜外组(GE组,n=15)。两组病人分别于麻醉前、双肺通气30min、单肺通气5、15、30min时采动脉血及混合静脉血,行血气分析,并计算出Qs/Qt等。结果两组患者在单肺通气后5、15、30min,Qs/Qt均增加(P<0.01),动脉氧分压(PaO2)较双肺通气时下降(P<0.01)。但在各时间点两组Qs/Qt以及PaO2无显著性差异。结论下胸段硬膜外阻滞对单肺通气期间肺内分流和动脉氧合无明显影响,可安全用于开胸单肺通气患者的麻醉。     

轻度肺通气功能障碍对单肺通气期间氧合和肺内分流的影响

目的:观察术前轻度肺通气功能障碍对单肺通气期间血液氧合及肺内分流的影响.方法:40例ASA Ⅰ～Ⅱ级择期需行单肺通气开胸手术的成年患者,根据术前肺功能测定结果,将患者分为肺通气功能正常组(Ⅰ组)及轻度肺通气功能障碍组(Ⅱ组),每组20例.分别于患者右侧卧双肺通气10min(T0),单肺通气10min(T1)、20min(T2)、30min(T3)、40 min(T4)抽取动、静脉血行血气分析并计算肺内分流率(Qs/Qt).结果:Ⅰ组患者单肺通气各时点动脉血氧分压(PaO2)较双肺通气时明显下降(P<0.05),Qs/Qt明显增加(P<0.05).Ⅱ组患者单肺通气各时点PaO2较双肺通气时明显升高(P<0.05),Qs/Qt则无明显改变,两组患者动脉血二氧化碳分压(PaCO2)、pH值、平均动脉压(MAP)、心率(HR)、脉搏血氧饱和度(SpO2)、呼气末二氧化碳分压(PETCO2)等在单肺通气期间无明显改变(P>0.05);与Ⅰ组比较,Ⅱ组患者各时点PaO2、Qs/Qt均有明显差异(P<0.05),而PaCO2、pH、MAP、HR、SpO2、PETCO2等则无明显差异(P>0.05).结论:术前轻度肺通气功能障碍患者较肺通气功能正常者单肺通气期间具有更好的血液氧合趋势,肺内分流则无明显增加,单肺通气期间低氧血症发生的危险性降低.     

自制简易CPAP装置在西宁地区(2261米)胸外科单肺通气中的应用

目的:探讨自制简易CPAP装置在西宁地区(2261米)胸外科单肺通气中的应用效果。方法:采用回顾性方法分析,选取本院2017年11月至2019年10月收治的20例择期行胸腔镜下肺叶切除术患者的临床资料,通过随机数字法分成两组CPAP组(10例,给予自制简易CPAP装置)与对照组(10例,未给予任何措施),均由两名固定医生进行麻醉操作和手术,于单肺通气10min、30min后进行指脉血氧饱和度的监测,并进行比较。结果:通气前,两组Hb、PaCO2、PaO2、Qs/Qt比较无显著差异(P>0.05);通气10min、30min后,两组Hb、PaCO2与通气前相比,无显著差异(P>0.05);而PaO2、Qs/Qt与通气前相比差异显著(P<0.05)。通气10min、30min后两组PaO2差异显著(P<0.05),而两组Qs/Qt比较无显著差异(P>0.05)。结论:西宁地区(2261米)胸外科单肺通气中给予自制简易CPAP装置,可增加动脉血氧分压,此装置较为可靠。     

两种气体持续气道正压在单肺通气中对肺内分流与氧合的影响

目的观察氧气与空气在不同持续气道正压(CPAP)水平下对单肺通气氧合与肺内分流的影响.方法随机将14例单肺通气下行开胸手术的病人平均分成组Ⅰ(氧气组)和组Ⅱ(空气组),常规诱导、插入双腔支气管导管后行单肺通气20min后,组Ⅰ利用氧气向无通气侧肺给予5 cmH2O的CPAP,15 min后再给予10 cmH2O的CPAP;而组Ⅱ利用空气向无通气侧肺给予5 cmH2O的CPAP,15 min后再给予10 cmH2O的CPAP.分别记录单肺通气前、单肺通气20min、5 cmH2O的CPAP15 min、10 cmH2O的CPAP15min、术毕恢复双肺通气15min所测得的动脉血pH、PaO2和PaCO2等数据,并计算Qs/Qt值.结果组Ⅰ:5 cmH2O CPAP 15 min比单肺通气20min:PaO2显著增高(P＜0.05)、Qs/Qt显著降低(P＜0.05).10 cmH2O CPAP 15 min比单肺通气20min:PaO2显著增高(P＜0.05)、Qs/Qt显著降低(P＜0.05).10 cmH2O CPAP 15 min比5 cmH2O CPAP 15 min:PaO2显著增高(P＜0.05)、Qs/Qt显著降低(P＜0.05).组Ⅱ:5 cmH2O CPAP 15 min比单肺通气20min:PaO2、Qs/Qt无显著差异(P＞0.05).10 cmH2O CPAP 15 min比单肺通气20min:PaO2显著降低(P＜0.05),Qs/Qt显著增加(P＜0.05).结论氧气提供CPAP可有效改善单肺通气造成的低氧状况,10 cmH2O CPAP比5 cmH2O CPAP对改善Qs/Qt、提高PaO2更有效.用空气提供CPAP不能使单肺通气产生的低氧状况得到改善.     

最佳呼气末正压对急性呼吸窘迫综合征猪模型肺内分流的影响

目的:探讨最佳呼气末正压(PEEP)对急性呼吸窘迫综合征(ARDS)猪模型肺内分流(Qs/Qt)的影响。方法:选择油酸静脉注射法复制猪ARDS模型(n=11),应用压力控制法进行肺复张,并根据最佳氧分压+二氧化碳分压法(PaO2+PaCO2)确定最佳PEEP。记录在基础状态、ARDS状态及最佳PEEP水平下,ARDS猪模型的Qs/Qt,气道平台压(Pplat)、静态顺应性(Cst)及动态顺应性(Cdyn)、动脉氧分压(PaO2)、混合静脉血氧分压(PvO2)、动脉血氧饱和度(SaO2)、混合静脉血氧饱和度(SvO2)等参数。并评估PaO2、PvO2、SaO2、SvO2对Qs/Qt的影响。结果:最佳PEEP可明显降低ARDS动物模型的Qs/Qt,P<0.05);Qs/Qt的影响因素大小依次为:SaO2(r2=0.953,P<0.05)、PaO2(r2分别为0.387,P<0.05)、SvO2(r2=0.273,P<0.05),而PvO2对Qs/Qt的影响(P>0.05)无统计学意义。结论:最佳PEEP可有效改善ARDS动物模型的肺内分流,动脉血氧饱和度是影响肺内分流的最主要因素。     

不同通气方式对单肺通气时血气值及肺分流量的影响

目的:探讨肺癌行肺叶切除术单肺通气时,不同通气方式对病人动脉血气值及肺内分流的影响。方法:择期肺癌行肺叶切除术病人40例,ASAⅠ～Ⅱ级,静脉快速诱导后插入双腔气管导管,行双肺机械通气(TLV),30min后改健肺单肺通气(OLV);潮气量(VT)6mL/kg,呼吸频率(f)16次/min,均吸入纯氧。同时术侧肺通气随机分为4组,每组10例。A组不给氧;B组持续氧流量给氧5L/min;C组用Bain环路行CPAP(压力0.5kPa,氧流量5L/min);D组用高频喷射通气(HFJV),驱动压力1kg/cm2,频率(f)100次/min,并在TLV30min,OLV30min后取动静脉血作血气分析并计算分流率(Qs/Qt)。结果:A、B两组OLV与TLV相比,PaO2和PVO2极显著或显著降低,A-aDO2和(Qs/Qt)极显著或显著升高,证明低氧血症与OLV时严重肺内分流有关。而C、D两组差异无显著性(P>0.05)。结论:Bain环路和高频喷射通气用于手术侧肺,能使患肺扩张并促进气体交换,有助于提高氧合,减少肺内分流,改善低氧血症。     

单肺通气时对血气值及肺分流量影响的临床研究

【目的】探讨肺癌行肺叶切除术单肺通气时,单肺通气(OLV)对患者动脉血气值及肺内分流的影响。【方法】择期肺癌行肺叶切除术患者40例,ASAI～Ⅱ级,静脉快速诱导后插入双腔气管导管,行双肺机械通气(TLV),30min后改健肺单肺通气。同时术侧肺通气随机分为4组,每组10例:A组,不给氧;B组,持续氧流量给氧5L/min;C组,用Bain环路行CPAP;D组,用高频喷射通气(HFJV),并在双肺通气和单肺通气各30min后取动静脉血作血气分析并计算分流率(Qs/Qt)。【结果】A、B两组OLV与TLV相比,PaO2和PVO2有极显著或显著性差异,AaDO2和(Qs/Qt)也有极显著或显著性差异,证明低氧血症与OLV时严重肺内分流有关。而C、D两组差异无显著性(P>0.05)。【结论】Bain环路和高频喷射通气用于手术侧肺,能使患肺扩张并进行气体交换,有助于提高氧合,减少肺内分流,改善低氧血症。     

选择性肺叶隔离对食管癌手术患者肺顺应性和氧合功能的影响

目的观察选择性肺叶隔离技术对左侧剖胸下段食管癌根治术患者肺顺应性及氧合功能的影响。方法 30例择期行下段食管癌根治术患者,随机均分为常规单肺通气对照组(OLV组)和选择性肺叶隔离组(SLB组)。OLV组术中按需行右肺通气,SLB组按需行右肺和左肺上叶通气。分别于侧卧位双肺通气后5 min(T1)、侧卧位右肺或右肺+左肺上叶通气后15 min(T2)、侧卧位右肺或右肺+左肺上叶通气后45 min(T3)、术毕恢复双肺通气后15 min(T4)四个时点记录患者血流动力学指标(CVP、HR、MAP)和呼吸力学指标[气道平台压(Pplat)、气道峰压(Ppeak)、肺顺应性(Cdyn)];采集T1^T4时患者颈内静脉和桡动脉血样,进行血气分析,并计算肺内分流率(Qs/Qt)。结果两组患者一般情况、术中血流动力学指标及术野清晰度等比较差异无统计学意义(P>0.05)。两组患者的Pplat、Ppeak在T2、T3时均显著高于T1时,SLB组明显低于OLV组(P<0.05);与T1时比较,两组T2T4时患者颈内静脉和桡动脉血样,进行血气分析,并计算肺内分流率(Qs/Qt)。结果两组患者一般情况、术中血流动力学指标及术野清晰度等比较差异无统计学意义(P>0.05)。两组患者的Pplat、Ppeak在T2、T3时均显著高于T1时,SLB组明显低于OLV组(P<0.05);与T1时比较,两组T2^T4时的Cdyn均降低(P<0.05),SLB组在T2、T3时的Cdyn明显高于OLV组(P<0.05);两组T2、T3时的PaO2均明显低于T1时(P<0.05),但SLB组T2、T3时的PaO2较OLV组高(P<0.05),两组患者在T2、T3时的Qs/Qt均明显升高,同时OLV组T4时仍略高于T1时,而SLB组T2T4时的Cdyn均降低(P<0.05),SLB组在T2、T3时的Cdyn明显高于OLV组(P<0.05);两组T2、T3时的PaO2均明显低于T1时(P<0.05),但SLB组T2、T3时的PaO2较OLV组高(P<0.05),两组患者在T2、T3时的Qs/Qt均明显升高,同时OLV组T4时仍略高于T1时,而SLB组T2^T4时的Qs/Qt均明显低于OLV组(P<0.05)。结论食管癌根治术患者术中行选择性肺叶隔离通气可显著降低Ppeak、Pplat,改善Cdyn,减少肺内分流,增加术中氧合,利于肺保护。     

开胸手术单肺通气期间非通气侧肺实施持续气道正压对肺内分流和氧合的影响

目的 观察单肺通气期闻非通气侧肺实施持续气道正压（CPAP）对肺内分流和氧合的影响。 方法 40例择期开胸单肺通气行肺叶切除患者,随机分对照组（A组）和CPAP组（B组）,每组20例。单肺通气时A组病人非通气侧支气管导管与大气相通,B组病人非通气侧肺给予5cmH2O的CPAP处理。分别于单肺通气前,单肺通气30min,单肺通气结束,恢复双肺通气30min抽动脉血测血气分析,根据公式计算肺内分流率。 结果 A组病人在单肺通气30min及单肺通气结束时PaO2明显降低,而与单肺通气前比较Qs／Qt则明显增高（P〈0.05）。B组病人PaO2及Qs／Qt虽有改变但各时点之间比较差异无显著性（P〉0．05）。单肺通气30min及单肺通气结束时,PaO2B组较A组高,而Qs／Qt低于A组（P〈0．05）。 结论 单肺通气期间非通气侧肺实施5cmH2O CPAP可明显提高氧分压,减少肺内分流。     

脂微球前列腺素E1对控制性降压患者动脉氧分压及肺内分流影响

目的观察脂微球前列腺素E1对硝普钠控制性降压患者手术期间动脉氧分压及肺内分流影响。方法择期行鼻内窥镜手术患者40例,分为脂微球前列腺素E1组(P组)和对照组(C组),每组20例。P组持续静脉泵注脂微球前列腺素E12 ng/(kg.min),C组以同样容积速率泵入生理盐水。分别于输注硝普钠前,降压30、60 min,停止硝普钠输注复压后20 min时分别取动脉血和右心房血做血气分析并记录监测数据。结果两组患者在不同采样点组间MAP、HR、pH值无显著性差异(P>0.05);与降压前比较,两组降压30、60 min时Qs/Qt升高,PaO2降低(P<0.05);组间比较降压30、60 min、复压后3点,P组PaO2高于C组(P<0.05),Qs/Qt仅在复压后P组高于C组(P<0.05);组内比较,C组复压后PaO2低于降压前(P<0.05)。结论脂微球前列腺素E1可以改善硝普钠控制性降压所引起动脉氧合变化,对降压期间肺内分流和血流动力学无明显影响,复压后可改善肺内分流。     

Unreliability of oxygen tension-based indices in reflecting intrapulmonary shunting in critically ill patients

Measurement of intrapulmonary shunting (Qsp/Qt), a widely used method for monitoring disturbances of pulmonary oxygen transfer in critically ill patients, involves calculation of arterial and mixed venous oxygen contents. In circumstances where mixed venous blood samples are not readily available, oxygen tension-based indices such as the alveolar to arterial oxygen tension differences (P[A-a]O2), arterial oxygen tension to alveolar oxygen tension ratio (PaO2/PAO2), PaO2 to FIO2 ratio (PaO2/FIO2) and respiratory index (RI) are widely utilized to reflect Qsp/Qt. Oxygen content-based indices such as the estimated shunt are not as widely utilized as the oxygen tension indices. In 75 critically ill patients in whom a pulmonary artery catheter was being utilized to augment clinical care, comparisons were made between Qsp/Qt and P(A-a)O2, PaO2/PAO2, PaO2/FIO2, RI, and estimated shunt to determine which index best reflected Qsp/Qt. Correlations between Qsp/Qt and estimated shunt were good (r = .94) and poor for the P(A-a)O2 (r = .62), PaO2/PAO2 (r = .72), PaO2/FIO2 (r = .71), and RI (r = .74). We conclude that there are no real substitutes for venous oxygen contents in critically ill patients. When pulmonary artery blood is not available for analysis, oxygen tension-based indices are unreliable reflectors of Qsp/Qt while the estimated shunt, an oxygen content-based index, provides a more reliable reflection of Qsp/Qt.     

吸入低浓度一氧化氮在猪急性肺栓塞中的作用

目的 探讨低浓度一氧化氮(NO)吸入在实验猪肺栓塞中的作用机制及治疗意义.方法 15只健康幼猪分成两组,分别建立肺栓塞模型.对照组8只,不做任何处理;NO组7只,模型建立后,持续吸入10×10-6的NO.每组于栓塞前30 min,栓寨后0 min,30 min,60min,120 min 5个时间点分别测定生理死腔(VDphy)、肺泡死腔(VDalv)、肺内分流(Qs/Qt)、平均肺动脉压(PAP)、血压(SBP)、心率(HR)、心输出量(CO)、动脉血pH值(pH)、动脉血二氧化碳分压(PaCO2)、动脉血氧分压(PaO2).结果 研究发现两组动物Vdphy[NO组栓寒前(64.1±18.0),栓塞后(109.1±30.0),(107.6±26.8),(97.1±24.1);对照组栓塞前(51.1±10.8),栓寨后(129.2±22.1),(116.9±32.5),(103.9±22.8)],VDalv[NO组栓塞前(8.8±4.3),栓寨后(64.3±26.9),(54.0±25.9),(45.7±22.4);对照组栓塞前(10.9±3.6),栓塞后(97.9±21.5),(80.7±25.3),(70.9±22.5)],Qs/Qt[NO组栓寨前(1.76±0.6),栓塞后(2.90±0.8),(3.1±0.6),(2.9±0.8);对照组栓塞前(1.05±1.5),栓塞后(3.4±0.7),(3.4±0.9),(3.5±0.8)],PAP[NO组栓塞前(16.6±3.4),栓塞后(31.7±3.1),(18.7±3.6),(18.0±3.4),(16.6±3.6);对照组栓塞前(15.8±2.6),栓塞后(35.4±3.3),(25.0±2.2),(25.0±3.5),(24.8±2.8)]栓塞后较栓塞前明显增大(P<0.01).PaO2栓塞后较栓塞前明显减小(P<0.05和P<0.01).HR、SBP、CO、pH、PaCO2栓塞前后差异无统计学意义(P>0.05).NO组PAP和VDalv较对照组明显减小(P<0.05和P<0.01),而PaCO2和PaO2较对照组明显增大(P<0.05).其余指标两组动物各时间点之间差异无统计学意义.结论 肺栓塞发生后,低浓度NO吸入可以降低肺动脉压,使肺泡死腔减小,氧分压增大,但不会发生血液动力学恶化.     

The effects of inversed ratio ventilation (IRV) on arterial oxygenation during mechanical ventilation in patients with acute respiratory failure.

We investigated the effects of inversed ratio ventilation by altering the inspiratory:expiratory (I:E) ratio and assessing the time course changes in the intrapulmonary shunting (Qs/Qt) in 14 patients with acute respiratory failure. Stepwise prolongation of the I:E ratio from 1:1.9 to 2:1 and then to 2.6 or 4:1 was applied when PEEP failed to raise the PaO2 above 80 mmHg while breathing oxygen. A significant decrease in Qs/Qt was observed following prolongation of the I:E ratio from 1:1.9 (Qs/Qt = 45 +/- 9%) to 2:1 (Qs/Qt = 29 +/- 9%) but not with further prolongation of the I:E ratio (Qs/Qt = 27 +/- 7%). Improvement of the pulmonary ventilation/perfusion imbalance became more marked with continued IRV and a significant increase in PaO2 was observed at 6 h after initiating prolongation of the inspiratory time (P less than 0.05). There were no significant changes in hemodynamics, PaCO2, or peak inspiratory pressure during IRV. This ventilatory pattern may be indicated when PEEP fails to improve PaO2, but prolongation of the inspiratory time above an I:E ratio of 2:1 did not produce a greater improvement in Qs/Qt and further increases in PaO2 did not occur after more than 10 h of IRV in our 14 patients.     

Effect of dopamine on intrapulmonary shunt fraction and oxygen transport in severe sepsis with circulatory and respiratory failure.

The hemodynamic response to a dopamine HCl infusion (10 microgram/kg per min) was measured in 25 adult patients with severe sepsis: there were 6 patients with circulatory hyperdynamic states, 9 patients with myocardial failure, and 10 with hypovolemia. Each patient also had acute respiratory failure. Changes of intrapulmonary shunt fraction (Qs/Qt), arterial and mixed venous oxygen tension (PaO2 and PvO2), oxygen transport, and oxygen consumption (VO2) were evaluated before and after dopamine infusion. Dopamine infusion produced clinical improvement and increased cardiac output. The hemodynamic response seemed to differ slightly according to the pattern of circulatory failure: chronotropic effect appeared to be predominant in hyperdynamic states, whereas inotropic effect appeared to be predominant in myocardial failure or hypovolemia. Moreover, in hypovolemic patients we noted a rise in pulmonary capillary wedge pressure suggesting an additional increase in venous return. During this treatment, we also noted a worsening of the Qs/Qt despite the increase in pulmonary blood flow; this worsening did not prevent significant improvements in VO2, but the improvement in PVO2 was offset by increased Qs/Qt and PaO2 remained unchanged.     

七氟醚复合异丙酚麻醉对单肺通气肺内分流和血气的影响

目的观察七氟醚复合异丙酚麻醉在胸外科手术行单肺通气期间对肺内分流和血气的影响。方法 30例ASAⅠ～Ⅱ级的患者,用芬太尼4～5μg/kg,咪唑安定0.05 mg/kg,异丙酚1.5～2 mg/kg,维库溴铵0.1 mg/kg作静脉快速诱导,插入双腔气管导管。用丙泊酚每千克体重6～8 mg/h泵注,吸入1.3～2.5 MAC的七氟醚,间断静脉滴注维库溴铵和芬太尼维持麻醉。分别在单肺通气前1 min(T1)、单肺通气15 min(T2)、30 min(T3)及单肺通气结束前1 min(T4)各时刻抽取动脉血和混合静脉血行血气分析,并根据血气分析结果计算肺内分流率(Qs/Qt)。结果 T2、T3、T4时刻,肺内分流率较T1时刻显著增加,动脉血氧分压较T1时刻显著下降,T4时刻的动脉血氧分压较T3时刻有所回升。结论单肺通气时七氟醚复合异丙酚静吸麻醉虽然对肺内分流有影响,但不影响其在临床中安全应用。     

去甲肾上腺素对山羊急性呼吸窘迫综合征吸入一氧化氮疗效的影响

目的 观察去甲肾上腺素(NE)对山羊感染性急性呼吸窘迫综合征(ARDS)吸入一氧化氮(NO)疗效的影响。方法 静脉注入小剂量内毒素诱导山羊感染性ARDS模型6只,在吸入体积分数为40×10-6的NO 30 min后,联合静脉泵入NE 0.5μg·kg-1·min-1治疗。通过肺动脉导管、动脉和混合静脉血气分析,测定基础、ARDS时、NO吸入治疗30 min和联合NE静脉泵入治疗30 min后血流动力学指标和肺气体交换参数。结果 NO吸入治疗能显著降低ARDS山羊的平均肺动脉压(MPAP),增加动脉氧分压(PaO2),减少肺泡动脉氧分压差[P(A-a)O2]和肺内分流率(Qs/Qt);联合NE静脉泵入不影响吸入NO后降低的MPAP,增加吸入NO后升高的PaO2,降低NO吸入后减少的P (A-a)O2和Qs/Qt,升高吸入NO后无改变的平均动脉压(P<0.05或P<0.01);吸入NO及联合应用NE治疗均不改变ARDS山羊的心排血量。结论静脉注入NE能增强吸入NO后改善感染性ARDS肺气体交换的疗效。     

Extrapulmonary factors influencing the ratio of arterial oxygen tension to inspired oxygen concentration in burn patients.

The ratio of arterial oxygen tension to inspired oxygen concentration (PaO2/FIO2) as an index of respiratory function was evaluated in 22 patients with body surface area burns of 15--80%. These results indicate that this ratio is limited in its applicability because extrapulmonary factors, such as cardiac output, oxygen consumption, and arterial oxygen content, can affect this index by alterations in the amount of venous desaturation. Useful estimates of intrapulmonary right to left shunt (Qs/Qt) from PaO2/FIO2 were obtained only when arteriovenous oxygen content differences (avDO2) were between 3--5 ml/dl. There were avDO2 values above and below 3--5 ml/dl in at least 35% of the observations. Under these circumstances, PaO2/FIO2 did not correctly reflect changes in Qs/Qt. Blood gases from central venous catheters did not mirror changes in true mixed venous blood and, thus, can lead to erroneous estimations of Qs/Qt. Rational therapy of reduced arterial oxygen saturation requires measurement of both extra- and intrapulmonary factors contributing to arterial desaturation. Measurement of PaO2/FIO2 alone will not estimate these factors.     

Arterial blood gas derived variables as estimates of intrapulmonary shunt in critically ill children

Oxygen transport data, prospectively collected from 52 critically ill children, were analyzed to determine whether any derived variable accurately estimated intrapulmonary shunt (Qsp/Qt). Arterial hemoglobin saturation was more closely correlated with Qsp/Qt than was PaO2, alveolar-arterial oxygen gradient, arterial mixed venous oxygen difference (C[a-v]O2), arterial/alveolar oxygen ratio, and the ratio of PaO2 to inspired oxygen (FIO2) (r = 0.8, p less than .0001). When C(a-v)O2 was normal, hemoglobin saturation became a very accurate (r = 0.96) assessment of Qsp/Qt. We conclude that various arterial blood gas derived variables do not accurately reflect Qsp/Qt in critically ill children. In these patients, a pulmonary artery catheter is needed to accurately assess intrapulmonary shunt.     

The AaDO2 and venous admixture at varying inspired oxygen concentrations in chronic obstructive pulmonary disease

The alveolar to arterial oxygen pressure difference (AaDO2) and pulmonary venous admixture (Qs/Qt) were measured in 32 patients with chronic obstructive pulmonary disease during right heart catheterization at inspired oxygen concentrations (FIO2) of 21, 24, 28, 35, and 40%. Patients without chronic hypercapnia (PaCO2 is less than 45 torr, group A) had Qs/Qt less than 25% while breathing room air; their AaDO2 rose at a rate of 3 torr for each percent increase in FIO2. In those with chronic hypercapnia (PaCO2 greater than 44 torr., (group B), THE Qs/Qt was always greater than 24% during air breathing and the AaDO2 rose at a rate of 5 torr for each percentage increase in FIO2. These changes should be considered in the interpretation of the AaDO2 in patients with COPD in whom the FIO2 is changed during the course of therapy. The Qs/Qt fell curvilinearly with increasing FIO2 but the rates of fall were quantitatively different in groups A and B. A physiological explanation for the changes in Qs/Qt and ADO2 which result from changes in FIO2 is presented.     

一氧化氮和尿激酶在猪急性肺栓塞中的作用

目的 探讨联合低浓度一氧化氮(NO)吸入和尿激酶在实验猪肺栓塞中的作用机制及治疗意义.方法 12只健康幼猪分成两组,分别建立肺栓塞模型.尿激酶组6只,模型建立后静脉给予2万U/(kg·h)共2 h;联合组6只,模型建立后静脉给予2万U/(kg·h)的同时持续2 h吸入10 ppmNO,两组均观察180min.每组于栓塞前30 min,栓塞后0 min,30 min,60 min,120 min,180 min共6个时间点分别测定生理死腔(Vophy)、肺泡死腔(Vdalv)、肺内分流(Qs/Qt)、平均肺动脉压(PAP)、血压(SBP)、心率(HR)、心输出量(CO)、动脉血pH值、动脉血二氧化碳分压(PaCO2)、动脉血氧分压(PaO2).数据分析采用单因数方差分析(SNK-q检验),以P<0.05为差异具有统计学意义.结果 与栓塞前比较,两组栓塞后VDphv,Vdalv,Qs/Qt,PAP明显增大(P<0.01),但PAP于栓塞后随着时间推移在逐渐减小.PaO2栓寨后较栓塞前明显减小(P<0.05和P<0.01).HR、SBP、CO、pH、PaCO2栓塞前后相比,差异无统计学意义(P>0.05).栓塞后联合组PAP较尿激酶组明显减小(P<0.05和P<0.01),其余指标两组动物各时间点之间差异无统计学意义.结论 肺栓塞发生后,尿激酶溶栓基础上联合低浓度NO吸入可以快速降低肺动脉压,但不会发生血液动力学和气体交换的恶化,NO反跳也不会出现.