Continuous transtracheal oxygen delivery during cardiopulmonary resuscitation. An alternative method of ventilation in a canine model

Adequate oxygenation of apneic subjects can be maintained by constant flow transtracheal oxygen (TTO), but this method alone is associated with hypercapnia. The "bellows" effect of external chest compressions (ECC) might prevent this problem if the airway were kept open by TTO. In dogs, we investigated the utility of TTO delivered at 15 L/min by a percutaneously placed intratracheal catheter, plus ECC (TTO/ECC) as an alternative method of ventilation during CPR. TTO was applied to anesthetized, paralyzed dogs in normal sinus rhythm (NSR) at various rates of ECC and during ventricular fibrillation (VF) at an ECC rate of 80/min. During NSR and VF, hypercapnia did not develop and arterial oxygen saturations were maintained above 90 percent. During NSR, the PaCO2 decreased and the pH increased as the ECC rate increased. For many of the animals, coronary perfusion pressure remained above 20 mm Hg during VF, suggesting that these animals could be resuscitated to NSR. In another phase, after 15 min of VF using TTO/ECC, seven of nine animals were defibrillated. We conclude that ventilatory and hemodynamic support adequate to permit successful resuscitation to NSR is provided by the combination of TTO/ECC to apneic dogs during VF.     

Survival factors in a canine septic shock model

Physiological indicators of tissue perfusion in a canine septic shock model have been examined. An early death (ED) group and a combined late death and survivor group (LDS) were defined and the corresponding data compared. It was found that the LDS group had less reductions in mean systemic arterial pressure (P less than 0.05), transcutaneous oxygen pressure (P less than 0.05), and red blood cell deformability (P less than 0.001); a smaller increase in hematocrit (P less than 0.05); and a lower concentration of white blood cells (P less than 0.05), relative to the ED group, at 6 hr after an infusion of Escherichia coli organisms. These results suggest that dogs in the LDS group have better tissue perfusion than those in the early death ED group. Post-treatment of dogs with pentoxifylline did not improve survival time or enhance flow factors.     

High-frequency jet ventilation cooling in a canine hyperthermia model

A study was undertaken to evaluate high-frequency jet ventilation (HFJV) as an adjunct for the treatment of heatstroke. Eleven mongrel dogs were anesthetized, shaved, and externally heated until core temperature reached 43 C (109.4 F). Control animals (n = 6) were cooled passively in room air. Treatment animals (n = 5) were cooled with the addition of HFJV using a flow-interrupter, high-frequency jet ventilator with a rate of 200, a driving pressure of 40 psi, and an inspiratory to expiratory ratio of .5 to deliver room air. Temperatures were measured in brain, pulmonary artery, rectum, and subcutaneous tissue of the chest wall. Serial arterial blood gases, cardiac outputs, and mean arterial pressures were measured at baseline, maximal heating, and at .5, 1, 2, and 12 hours after heating. Animals were sacrificed 12 hours after heatstroke induction. Cooling rates for brain, pulmonary artery, and rectum achieved in the HFJV group were 1.7 times faster than those for the control group (P less than .05), although slower than previously reported cooling rates with gastric and peritoneal lavage. A higher PO2, a lower PCO2, and a more physiologic pH was maintained in the HFJV group than in the control group at 30 and 60 minutes after onset of cooling (P less than .05). Gross and histopathologic examination showed characteristic changes of heatstroke in both groups; no deleterious findings could be attributed to the use of HFJV itself. HFJV warrants clinical investigation as an adjunct for treatment of hyperthermia.     

Non-invasive ventilation improves hemorheology status in hypoxemic patients with acute myocardial infarction after PCI

Background Hypoxemia often occurs in the emergency room in the patients with acute myocardial infarction (AMI) after percutaneous coronary intervention (PCI), even in those with administration of conventional high-flow oxygen inhalation. The objective of the present study was to evaluate the effectiveness of non-invasive ventilation (NIV) in improving blood oxygen content and hemorheology in patients with AMI and hypoxemia. Methods This prospective study enrolled 50 consecutive eligible patients with AMI (aged 72.3 ± 9.5 years), who had undergone PCI and been administered high-flow oxygen but still had hypoxemia. Blood was taken before NIV and at 0.5, 1, and 2 h after NIV. Blood gases, hemorheological variables including erythrocyte deformability, erythrocyte aggregation, erythrocyte osmotic fragility, membrane fluidity, and oxidative stress level were measured. Results Blood PaO2 increased to normal by 1 h after NIV. Assessed hemorheological variables had all improved and plasma malondialdehyde concentration decreased significantly after 2 h of NIV. Conclusions Our data suggest that NIV can help to improve blood oxygen content, hemorheological status, and minimize plasma lipid peroxidation injury in hypoxemic patients with AMI who have undergone PCI.     

闭环通气模式在机械通气脱机阶段的观察及护理配合

脱机是从完全通气支持向自主呼吸转变的一个过程,过去常用的脱机模式需要密切监测患者的临床表现及血气分析变化,便于及时调节呼吸参数,无疑增加了医务人员的负担,同时也增加了患者的痛苦。新的闭环通气模式的应用对提高患者的脱机效率、减轻医务人员的工作负担均起到重要作用,然而此阶段的观察及护理配合对减轻患者的痛苦,缩短脱机进程显得尤为重要。笔者就闭环通气模式阶段的观察及护理配合谈谈自己的护理体会。     

Liquid ventilation in an infant with pulmonary alveolar proteinosis

Partial liquid ventilation (PLV) has been applied in various pulmonary diseases. We describe the use of partial liquid ventilation as a lavage method following normal saline (NS) lavage in an infant with pulmonary alveolar proteinosis (PAP) and severe hypoxemia. A 6 weeks old 3.4 kg former 36 weeks gestation boy on supplemental oxygen was transferred to our NICU with persistent tachypnea, dry cough, and increasing oxygen requirements. A lingular open lung biopsy revealed PAP. He developed progressive respiratory failure requiring ventilatory support, necessitating conventional NS lavage, followed by lung lavage with perflubron (LiquiVent; Alliance Pharmaceutical Corp. and Hoechst Marion Roussel) while on venovenous extracorporeal life support (ECLS). Lung lavage with NS and perflubron yielded minimal cloudy effluent. Gas exchange and pulmonary function deteriorated following NS lavage and attempts to discontinue ECLS were poorly tolerated. In contrast, tidal volume, P_aO₂, and pulmonary compliance increased after PLV, while the (A-a) DO₂ decreased to a point where ECLS was no longer required. Once perflubron was added repeatedly to the ventilator circuit to correct for evaporation over the 4 days of PLV. Cardiovascular status remained stable for several days; however, eventually he required reinitiation of ECLS and more mechanical ventilatory support with each trial off ECLS. He was maintained on high pressures and F_iO₂ without any possibility to wean him from mechanical ventilation. Life support was withdrawn 1 month after admission. The survival from PAP in infants remains dismal, even with total lung NS lavage. While both NS and perflubron lavage in this patient were not effective in removing the proteinaceous alveolar debris, PLV following NS lavage was associated with an improvement in gas exchange and lung compliance. Pediatr Pulmonol. 1998; 26:283–286. © 1998 Wiley-Liss, Inc.     

Treatment of shock in a canine model of pulmonary embolism

Despite the high mortality (greater than 30%) associated with hypotension complicating pulmonary embolism, previous studies have not systematically investigated how best to treat shock resulting from pulmonary embolism. In 24 dogs, we measured relevant hemodynamic parameters before and after shock was produced by intravenously injected autologous blood clots. When systemic blood pressure fell to 70 mmHg, dogs were randomly divided into groups and treated blindly for 1 h. All control dogs and all dogs treated with volume and isoproterenol died. In contrast, all dogs treated with noradrenaline were resuscitated and remained hemodynamically stable for 1 h. This effect of noradrenaline was significant (p less than 0.01, Fisher's exact test). Noradrenaline improved right ventricular performance by increasing blood pressure and improving right ventricular perfusion and/or by a direct increase in contractility. We conclude that in a canine model of pulmonary embolism and shock, noradrenaline may be the drug of choice for acute resuscitation.     

冠状动脉血栓形成动物模型的建立

目的 :建立一种合适的冠状动脉血栓形成动物模型。方法 :选择健康杂种犬 12只 ,用心导管技术将铜网圈置入犬冠状动脉内 ,使之在局部形成血栓。结果 :冠状动脉造影证实冠状动脉内有阻塞性血栓形成 ,病理切片显示犬冠状动脉内血栓与人类冠状动脉血栓结构相似。结论 :该法操作简单 ,重复性好 ,血栓形成耗时较短 ,平均仅 ( 16 .8± 10 .5 ) m in,闭塞血管可任意选择     

Percutaneous treatment of the superior vena cava syndrome via an excimer laser sheath in a patient with a single chamber atrial pacemaker

A 21-year-old woman presented with a pacemaker-associated superior vena cava (SVC) syndrome refractory to medical therapy. In the past, treatment of this condition has involved surgical exploration which is invasive. With the evolution of percutaneous techniques, treatment has included venoplasty and stenting over the pacemaker lead. There is limited experience with a more advanced percutaneous technique in which the lead is extracted by an excimer laser sheath. The extraction is immediately followed by venoplasty and stenting at the site of stenosis with subsequent implantation of a new permanent pacemaker at the previously occluded access site. The patient underwent this procedure which proved to be safe, minimally invasive, and an efficient method of treating SVC syndrome secondary to a single chamber atrial pacemaker.     

Percutaneous coronary intervention in a patient with single coronary artery

Coronary artery anomalies are found in 1–5% of all coronary angiograms. Single coronary artery is a rare congenital anomaly. The prevalence of the anomaly is 0.024–0.066% of the general population and percutaneous coronary intervention in this anomaly is performed infrequently. The highest incidence of this condition is reported from India. We report a case of a 55 year old patient of anterior wall ST elevation myocardial infarction with L1 group of single coronary artery who underwent successful angioplasty and stenting to left anterior descending artery. The unique features and inherent risks of percutaneous coronary intervention to single coronary artery are discussed.     

重症心源性肺水肿伴休克患者的机械通气治疗

目的研究重症心源性肺水肿伴休克患者机械通气(MV)治疗时通气压力的选择对预后的影响。方法将符合标准的22例患者分为两组对照组9例,常规给予较低通气压力和加强药物治疗;治疗组13例,适当增加通气压力。观察血压、临床症状和动脉血气的变化。结果调整MV后30分钟时,治疗组收缩压迅速由(95±12)mmHg升至(130±15)mmHg(P<0.001),呼吸频率(RR)由(38±11)次/min降至(27±6)次/min(P<0.005),心率(HR)由(126±15)次/min降至(105±12)次/min(P<0.001);对照组上述指标变化不明显。2小时后治疗组的升压药用量减少(70±15)%,对照组则增加(20±5)%;同时在吸氧浓度不变的情况下,治疗组的PaO2由(81±12)mmHg升至(140±15)mmHg(P<0.001),明显高于对照组PaO2的改善。24~48小时内治疗组11例患者(85%)停用升压药,对照组2例(22%)停用。最终治疗组100%的患者好转出院,对照组为45%(P<0.05)。结论与低压力通气相比,适当增加MV通气压力不仅可迅速改善重症心源性水肺肿伴休克患者的低氧血症,也可迅速升高血压,改善心功能,降低病死率。     

Bi-level positive airway pressure (BiPAP) ventilation in an infant with central hypoventilation syndrome

A 4-month-old baby girl, after a period of apparent good health, began to have aphonia, dyspnea, difficulties with swallowing, cyanosis, apnea, and hypopnea during sleep that resulted in admission to an intensive care unit for intubation and mechanical ventilation. At the age of 9 months she was admitted to our hospital with a possible diagnosis of central hypoventilation syndrome. A polysomnographic study showed apnea and hypopnea (apnea + hypopnea index = 47.1), hypercapnia (mean end-tidal P 89 ± 15.0 mmHg), and arterial desaturation (mean Sa 91 ± 1.7%; lowest Sa < 50%; 68% of total sleep time at Sa below 93%); the study also showed an absent ventilatory response to CO₂, absent cardiac responses to apnea during sleep, and right ventricular hypertrophy. Nocturnal nasal bi-level positive airway pressure (BiPAP), applied initially at 6 cmH₂O and gradually increased to 16 cmH₂O, caused the sleep-related abnormal respiratory events to disappear. End-tidal Pco₂ decreased to 39 mmHg, and Sao₂ increased to 94%. After 6 months of nocturnal BiPAP ventricular right hypertrophy reversed and arrested growth and hypotonia normalized. The child has tolerated and has remained on BiPAP support up to her current age of 3 years and continues to use this form of ventilatory assistance without difficulties. Pediatr. Pulmonol. 1997;24:66–69. © 1997 Wiley-Liss, Inc.     

Lung pathology after high frequency jet ventilation combined with low rate intermittent mandatory ventilation in a canine model of meconium aspiration

The microscopic appearance of lungs subjected to six hours of conventional ventilation (CV), standard high frequency jet ventilation (HFJV), and HFJV combined with low rate intermittent mandatory ventilation (CHFJV) was studied in 22 mongrel puppies. A lung injury model was created by insufflating 4 ml/kg of a 20% mixture of meconium into the trachea. The animals were initially ventilated at the same mean airway pressure (Paw). Subsequently, if PCO2 fell below 20 torr, peak and mean airway pressures were reduced. A scoring system was devised which assigned 0-3 points for each of eight lung injury parameters, and a total lung injury score (TLIS) was calculated. CHFJV resulted in significantly less bronchopneumonia and edema, when compared to CV. A consistent, though not significant, trend toward lesser injury scores in CHFJV animals was noted for several other parameters. Six of eight lungs exposed to CV had TLIS greater than 5 compared to only 1 of 9 ventilated by CHFJV. (P = 0.02). It is concluded that CHFJV may have a protective effect on the lung, perhaps because effective gas exchange is achieved with a lower pressure amplitude and at lower Paw.     

Manual translaryngeal jet ventilation and the risk of aspiration in a canine model

STUDY OBJECTIVES: Manual translaryngeal jet ventilation (TLJV) is a safe and effective method of maintaining normal ventilation in apneic subjects. Little data exist on the amount of airway protection afforded with this technique of airway management. We sought to evaluate the risk of aspiration during manual TLJV. SETTING: Data were collected in a laboratory animal model. DESIGN: A prospective, nonrandomized, controlled trial was performed. PARTICIPANTS: Seventeen adult apneic mongrel dogs were enrolled. INTERVENTIONS: Intratracheal Gastrograffin was instilled and radiographic changes assessed during ventilation using a 0 to 3 scale (none to severe). Thirty-six trials were performed, with equal numbers at both 30 degrees and 45 degrees head elevation. The three groups studied were animals without airway protection (control), animals with a cuffed endotracheal tube (tube), and animals with a percutaneous TLJV cannula and a 50-psi oxygen source ventilated at a rate of 20 breaths per minute (jet). MEASUREMENTS AND MAIN RESULTS: Significantly less radiographic evidence of aspiration was noted in the jet and tube groups at 30 degrees and 45 degrees compared with control animals (P = .002 each). At 45 degrees head elevation a trend toward increased aspiration scores in the jet group compared with the tube group (P = .065) was observed. CONCLUSION: In our model, manual TLJV at 20 breaths per minute and an I:E ratio of 1:2 provided protection from aspiration comparable to that observed with a cuffed endotracheal tube at 30 degrees head elevation. At 45 degrees elevation, this protection was diminished.     

HFOV联合PLV对蒸汽吸入性损伤兔呼吸、循环功能及肺组织学的影响

目的 寻找治疗蒸汽吸入性损伤的合理机械通气方式.方法 将32只制成重度蒸气吸入性损伤兔模型随机分为四组各8只,分别行常频机械通气(CMV),CMV+部分液体通气(PLV),高频振荡通气(HFOV)及HFOV+PLV,分别于治疗后0.5、1.5、2.5、3.5 h取动脉血行血气分析;通气治疗4 h后处死动物,右肺中叶取4个不同部位(依赖区和非依赖区)标本,行病理学检查.结果 各组PaO2在通气治疗0.5 h后均明显上升,通气治疗3.5 h内维持较高水平,HFOV组和HFOV+PLV组各时间点PaO2均分别高于CMV组和CMV+PLV组,CMV+PLV组1.5、2.5 h的PaO2高于CMV组,HFOV+PLV组3.5 h的PaO2高于HFOV组;各组不同时点PaCO2、心率、平均动脉压均无明显栽差异;肺组织病理学检查发现HFOV+PLV组损伤最轻,CMV组损伤最重.结论 HFOV联合PLV能提高蒸汽吸入性损伤兔的氧合水平,减轻肺损伤.     

Quantitative assessment of aortic regurgitation by colour flow Doppler in an open chest canine model

Colour flow Doppler maps the extent of the flow velocity disturbance of aortic regurgitation onto the two dimensional echocardiographic image of the left ventricular cavity. The spatial extent of this flow velocity disturbance expressed as a percentage of end diastolic left ventricular cavity area (CD%) was compared to regurgitant fraction (RF), measured volumetrically, in nine open chest dogs with varying degrees of surgically created aortic regurgitation (RF 0-85%). Right heart bypass controlled venous return to the left atrium and hence net left ventricular output, while total left ventricular output was measured with an aortic electromagnetic flow probe under various loading conditions, achieving mean diastolic transvalvular pressure gradients of 23-114 mm Hg, net left ventricular outputs of 750-3000 ml.min-1 and diastolic filling periods of 162-320 ms. A linear correlation between CD% and RF (r = 0.89) was demonstrated over this wide range of loading conditions. At a given transvalvular diastolic pressure gradient [68(SD9) mm Hg] CD% was linearly proportional to regurgitant aortic orifice area (r = 0.87). Thus CD% is proportional to the volumetric severity of aortic regurgitation under a wide range of haemodynamic conditions and varies appropriately with regurgitant aortic orifice area when diastolic transvalvular pressure gradient is held constant. The application of these principles to the non-invasive quantitation of valvular regurgitation by colour Doppler appears feasible.