Effects of unilateral superimposed high-frequency jet ventilation on porcine hemodynamics and gas exchange during one-lung flooding

BACKGROUND Superimposed high-frequency jet ventilation(SHFJV)is suitable for respiratory motion reduction and essential for effective lung tumor ablation.Fluid filling of the target lung wing one-lung flooding(OLF)is necessary for therapeutic ultrasound applications.However,whether unilateral SHFJV allows adequate hemodynamics and gas exchange is unclear.AIM To compared SHFJV with pressure-controlled ventilation(PCV)during OLF by assessing hemodynamics and gas exchange in different animal positions.METHODS SHFJV or PCV was used alternatingly to ventilate the non-flooded lungs of the 12 anesthetized pigs during OLF.The animal positions were changed from left lateral position to supine position(SP)to right lateral position(RLP)every 30 min.In each position,ventilation was maintained for 15 min in both modalities.Hemodynamic variables and arterial blood gas levels were repeatedly measured.RESULTS Unilateral SHFJV led to lower carbon dioxide removal than PCV without abnormally elevated carbon dioxide levels.SHFJV slightly decreased oxygenation in SP and RLP compared with PCV;the lowest values of PaO_(2) and PaO_(2)/FiO_(2) ratio were found in SP[13.0;interquartile range(IQR):12.6-5.6 and 32.5(IQR:31.5-38.9)kPa].Conversely,during SHFJV,the shunt fraction was higher in all animal positions(highest in the RLP:0.30).CONCLUSION In porcine model,unilateral SHFJV may provide adequate ventilation in different animal positions during OLF.Lower oxygenation and CO_(2) removal rates compared to PCV did not lead to hypoxia or hypercapnia.SHFJV can be safely used for lung tumor ablation to minimize ventilation-induced lung motion.

COMPARISON OF HIGH-FREQUENCY OSCILLATION VEN-TILATION WITH CONVENTIONAL MANDATORY VENTILATION IN ANIMAL ARDS MODEL

To compare effect of high-frequency oscillation ventilation （HFOV） and conventional mandatory ventilation （CMV） on lung injury development in rabbit with acute respiratory distress syndrome （ ARDS）. Methods Animals that underwent saline lung lavage to produce lung injury were randomized to one of the two treatment groups （ HFOV or CMV, n =6）. PaCO2 was maintained between 35 -45mmHg and arterial oxygen saturation （ SaO2 ） was maintain 〉 88% by adjusting corresponding ventilator parameters. Ventilation period was 6h. Lung fluids were aspirated before and at the end of ventilation for cell analysis. Then the animals were euthanized, lung tissue was removed for wet/dry weight measurement, light and electron microscopic examination. Besults The difference of artery blood gas analyses（pH, PaO2, PaCO2 ） between HFOV and CMV was insignificant. The difference between HFOV and CMV in cytological examination of lung fluids, wet/dry weight measurement was also insignificant. But compared with CMV, HFOV not only reduced the area of lung injury, but also reduced lung injury score in light and electron microscopic examination. Conclusion When same artery blood gas analysis was obtained, HFOV significantly reduced lung injury development in ARDS animal than CMV. As a lung protection strategy, HFOV can be used in the treatment of ARDS.

Carbon Dioxide Levels When Starting High Frequency Ventilation in Neonates

Objective: High-frequency ventilation (HFV) is an effective means to achieve gas exchange in neonates. Adequate carbon dioxide (pCO2) levels are best achieved immediately after starting HFV, avoiding either hypercapnia or hypocapnia. We aimed to determine the initial pCO2 levels after starting HFV, and the time taken to obtain the initial blood gas. Methods: We conducted an observational retrospective study on neonates that required their first episode of HFV. Data included the first blood gas result after starting HFV and when the gas was taken after starting HFV. Results: This study included 112 neonates with a median birth weight of 938 (IQR: 692 - 1549) grams and gestational age of 27.2 (24.6 - 30.7) weeks. The first pCO2 after starting HFV (mean (SD)) was 53.7 (22) mmHg. Of 112, 15 (13.4%) showed initial hypocapnia (pCO2 35 mmHg), and 17 (15.2%) showed hypercapnia (pCO2 > 65 mmHg)—a total of 28.6% unacceptable pCO2 levels. Of 112, the first blood gas was obtained within 30 minutes in 47 (42%) and within one hour in 85 (76%), with a significant delay of two or more hours in eight (7.1%). Conclusion: Many neonates had unacceptable pCO2 levels upon starting first-time HFV. There were significant delays in obtaining the initial gas.

Effects of high-frequency oscillatory ventilation and conventional mechanical ventilation on oxygen metabolism and tissue perfusion in sheep models of acute respiratory distress syndrome

Background High-frequency oscillatory ventilation （HFOV） allows for small tidal volumes at mean airway pressures （mPaw） above that of conventional mechanical ventilation （CMV）,but the effect of HFOV on hemodynamics,oxygen metabolism,and tissue perfusion in acute respiratory distress syndrome （ARDS） remains unclear.We investigated the effects of HFOV and CMV in sheep models with ARDS.Methods After inducing ARDS by repeated lavage,twelve adult sheep were randomly divided into a HFOV or CMV group.After stabilization,standard lung recruitments （40 cmH2O × 40 seconds） were performed.The optimal mPaw or positive end-expiratory pressure was obtained by lung recruitment and decremental positive end-expiratory pressure titration.The animals were then ventilated for 4 hours.The hemodynamics,tissue perfusion （superior mesenteric artery blood flow,pHi,and Pg-aCO2）,oxygen metabolism and respiratory mechanics were examined at baseline before saline lavage,in the ARDS model,after model stabilization,and during hourly mechanical ventilation for up to 4 hours.A two-way repeated measures analysis of variance was applied to evaluate differences between the groups.Results The titrated mPaw was higher and the tidal volumes lower in the HFOV group than the positive end-expiratory pressure in the CMV group.There was no significant difference in hemodynamic parameters between the HFOV and CMV groups.There was no difference in the mean alveolar pressure between the two groups.After lung recruitment,both groups showed an improvement in the oxygenation,oxygen delivery,and DO2.Lactate levels increased in both groups after inducing the ARDS model.Compared with the CMV group,the superior mesenteric artery blood flow and pHi were significantly higher in the HFOV group,but the Pg-aCO2 decreased in the HFOV group.Conclusion Compared with CMV,HFOV with optimal mPaw has no significant side effect on hemodynamics or oxygen metabolism,and increases gastric tissue blood perfusion.

High-frequency jet ventilation for right upper pulmonary lobe sleeve resection

Hypoxemia during one-lung ventilation （OLV） is normal. Different ways of improving SpO2 on OLV include intermittent inflation ot the collapsed lung with oxygen, lung recruitment, and application of continuous positive airway pressure （CPAP） to the nondependent lung. This case report described the use of CPAP to the right lung, which was converted to high-frequency jet ventilation （HFJV） of the middle and lower lobes during fight upper lobe sleeve resection.

高频通气延长管在气管异物取出术中的应用

气管及支气管异物多发生于10岁以下儿童,一些特殊类型气管异物（如：异物体积大、质地硬、不易钳夹等）手术失败率很高.自2001年以来,我们自行设计了高频通气延长管,并将其应用于气管及支气管异物取出术,取得了满意的效果,现报告如下.

对中心性气道狭窄引起的重度呼吸困难进行无创通气治疗初探

目的初步探讨高频喷射和双相气道正压通气（BiPAP）两种无创通气方法治疗中心性气道狭窄引起重度呼吸困难的疗效以及两种模式的适用范围。方法采用回顾性分析的方法，将2006年1月至2009年1月收治的中心性气道狭窄引起重度呼吸困难的患者，根据采用高频喷射或BiPAP无创通气方法分成H组和B组，对比两种通气模式缓解呼吸困难及纠正缺氧的有效率。结果H组7例，B组9例。对减轻呼吸困难的疗效评价，H组有效率为14．29％（1／7），仅接受高频喷射呼吸机治疗者4例，有效率为25．00％（1／4），接受高频喷射呼吸机治疗无效，随后应用BiPAP呼吸机治疗有效者2例，接受BiPAP呼吸机治疗好转并撤机，再发呼吸困难后采用高频喷射呼吸机治疗无效者1例。B组中仅接受BiPAP呼吸机治疗者6例，有效率为83．33％（5／6），结合上述与高频喷射呼吸机治疗序贯应用的病例，共9例，有效8例，无效1例，有效率为88．89％，两组比较差异有统计学意义（P=0．006）。在纠正低氧血症疗效方面，H组有效率为100．00％（7／7）；B组有效率为88．89％（8／9），两组比较差异无统计学意义（P=0．563）。结论高频喷射呼吸机对纠正缺氧有效，但对于缓解呼吸困难症状，使患者自觉症状减轻方面效果差，较适合在术前和术中临时进行生命支持；BiPAP呼吸机缓解患者呼吸困难症状的治疗效果可能优于高频喷射呼吸机，可试用于临时缓解症状、术前准备及恶性肿瘤的姑息治疗。