A comparison of financial and operational efficiency between smart and traditional insufflation for laparoscopic surgery: A granular analysis

Objective:Smart insufflation(SI)techniques relying on valve and membrane-free insufflation are increasing in usage.Although considerable literature exists demonstrating the benefits of SI on procedural ease and patient outcomes,there remains a paucity describing the financial impact of these devices.The purpose of this study was to determine the financial and efficiency impact of these devices on the operating room and inpatient wards of a hospital.Methods:A discrete event simulation model representing a typical mid-sized North American hospital comparing SI to traditional insufflation(TI)was generated.The National Surgical Quality Improvement database from 2015 to 2019 was used to populate the model with data supplemented from the literature.Outcomes included length of stay(LOS),duration of surgery(DOS),annual procedure volume,profit,return on investment(ROI),and gross profit margin(GPM).From the literature review,DOS savings were 10e32 minutes/case,while LOS savings were 0e3 days/case.Results:Implementation of an SI led to an increase in annual throughput of 42e346(4.4%e36.6%)cases for all procedures and 38 to 297(4.3%e33.3%)cases for complex procedures.LOS was found to be decreased by 175e614(18.3%e64.2%)days for all procedures and 231 to 614(35.6%e77.9%)cases for complex procedures with the implementation of an SI.Together,this resulted in an increase in net profit of$104,685 per annum.The ROI of SI over the TI device was>1000%,and the GPM for the TI was 90.0%,while the GPM for the SI was 71.7%.Conclusion:Despite the initial financial investment being greater,the implementation of SI offsets these expenses and yields significant financial benefits.Our study demonstrates the financial benefits of SI over TI and illustrates how granular operational and financial analyses of technologies are essential to aid in sound healthcare procurement decision making.

自动咽鼓管吹张器治疗儿童分泌性中耳炎

分泌性中耳炎（secretory otitis media,SOM）是以中耳负压或积液及听力下降为主要特征的中耳非化脓性炎性疾病,特别是儿童SOM对儿童的语言和智力发育造成严重影响。对于早期儿童SOM治疗临床上多采用药物治疗同时配合咽鼓管吹张法,但该方法患儿难以配合常导致治疗效果欠佳。

Safety and efficacy of carbon dioxide insufflation during gastric endoscopic submucosal dissection

AIM: To compare the safety and efficacy of carbon dioxide(CO2) and air insufflation during gastric endoscopic submucosal dissection(ESD).METHODS: This study involved 116 patients who underwent gastric ESD between January and December 2009.After eliminating 29 patients who fit the exclusion criteria,87 patients,without known pulmonary dysfunction,were randomized into the CO2 insufflation(n = 36) or air insufflation(n = 51) groups.Standard ESD was performed with a CO2 regulation unit(constant rate of 1.4 L/min) used for patients undergoing CO2 insufflation.Patients received diazepam for conscious sedation and pentazocine for analgesia.Transcutaneous CO2 tension(Ptc CO2) was recorded 15 min before,during,and after ESD with insufflation.Ptc CO2,the correlation between Ptc CO2 and procedure time,and ESD-related complications were compared between the two groups.Arterial blood gases were analyzed after ESD in the first 30 patients(12 with CO2 and 18 with air insufflation) to assess the correlation between arterial blood CO2 partial pressure(Pa CO2) and Ptc CO2.RESULTS: There were no differences in respiratoryfunctions,median sedative doses,or median procedure times between the groups.Similarly,there was no significant difference in post-ESD blood gas parameters,including Pa CO2,between the CO2 and air groups(44.6 mm Hg vs 45 mm Hg).Both groups demonstrated median p H values of 7.36,and none of the patients exhibited acidemia.No significant differences were observed between the CO2 and air groups with respect to baseline Ptc CO2(39 mm Hg vs 40 mm Hg),peak Ptc CO2 during ESD(52 mm Hg vs 51 mm Hg),or median Ptc CO2 after ESD(50 mm Hg vs 50 mm Hg).There was a strong correlation between Pa CO2 and Ptc CO2(r = 0.66; P < 0.001).The incidence of Mallory-Weiss tears was significantly lower with CO2 insufflation than with air insufflation(0% vs 15.6%,P = 0.013).CO2 insufflation did not cause any adverse events,such as CO2 narcosis or gas embolisms.CONCLUSION: CO2 insufflation during gastric ESD results in similar blood gas levels as air insufflation,and also reduces the incidence of Mallory-Weiss tears.

Inhibitory effects of carbon dioxide insufflation on pneumoperitoneum and bowel distension after percutaneous endoscopic gastrostomy

AIM:To evaluate the inhibitory effects of carbon dioxide (CO2) insufflation on pneumoperitoneum and bowel distension after percutaneous endoscopic gastrostomy (PEG).METHODS:A total of 73 consecutive patients who were undergoing PEG were enrolled in our study.After eliminating 13 patients who fitted our exclusion criteria,60 patients were randomly assigned to either CO2 (30 patients) or air insufflation (30 patients) groups.PEG was performed by pull-through technique after threepoint fixation of the gastric wall to the abdominal wall using a gastropexy device.Arterial blood gas analysis was performed immediately before and after the procedure.Abdominal X-ray was performed at 10 min and at 24 h after PEG to assess the extent of bowel distension.Abdominal computed tomography was performed at 24 h after the procedure to detect the presence of pneumoperitoneum.The outcomes of PEG for 7 d postprocedure were also investigated.RESULTS:Among 30 patients each for the air and the CO2 groups,PEG could not be conducted in 2 patients of the CO2 group,thus they were excluded.Analyses of the remaining 58 patients showed that the patients' backgrounds were not significantly different between the two groups.The elevation values of arterial partial pressure of CO2 in the air group and the CO2 group were 2.67 mmHg and 3.32 mmHg,respectively (P = 0.408).The evaluation of bowel distension on abdominal X ray revealed a significant decrease of small bowel distension in the CO2 group compared to the air group (P < 0.001) at 10 min and 24 h after PEG,whereas there was no significant difference in large bowel distension between the two groups.Pneumoperitoneum was observed only in the air group but not in the CO2 group (P = 0.003).There were no obvious differences in the laboratory data and clinical outcomes after PEG between the two groups.CONCLUSION:There was no adverse event associated with CO2 insufflation.CO2 insufflation is considered to be safer and more comfortable for PEG patients because of the lower incidence of pneumoperitoneum and less distension of the small bowel.

CO_2 insufflation for potentially diffi cult colonoscopies: Effi cacy when used by less experienced colonoscopists

AIM： To clarify the effectiveness of CO2 insufflation in potentially difficult colonoscopy cases, particularly in relation to the experience level of colonoscopists. METHODS： One hundred twenty potentially difficult cases were included in this study, which involved females with a low body mass index and patients with earlier abdominal and/or pelvic open surgery or previously diagnosed left-side colon diverticulosis. Patients receiving colonoscopy examinations without sedation using a pediatric variable-stiffness colonoscope were divided into two groups based on either CO2 or standard air insuffiation. Both insufflation procedures were also evaluated according to the experience level of the respective colonoscopists who were divided into an experienced colonoscopist （EC） group and a less experienced colonoscopist （LEC） group. Study measurements included a 100-mm visual analogue scale （VAS） for patient pain during and after colonoscopy examinations, in addition to insertion to the cecum and withdrawal times. RESULTS： Examination times did not differ, however, VAS scores in the CO2 group were significantly better than in the air group （P〈 0.001, two-way ANOVA） from immediately after the procedure and up to 2 h later. There were no significant differences between either insufflation method in the EC group （P = 0.29）, however, VAS scores for CO2 insufflation were significantly better than air insufflation in the LEC group （P = 0.023） immediately after colonoscopies and up to 4 h afterwards. CONCLUSION： CO2 insufflation reduced patient pain after colonoscopy in potentially difficult cases when performed by LECs.

Carbon dioxide insufflation in esophageal endoscopic submucosal dissection reduces mediastinal emphysema: A randomized, double-blind, controlled trial

AIM To assess the efficacy of CO2 insufflation for reduction of mediastinal emphysema(ME) immediately after endoscopic submucosal dissection(ESD).METHODS A total of 46 patients who were to undergo esophageal ESD were randomly assigned to receive either CO2 insufflation(CO2 group, n = 24) or air insufflation(Air group, n = 22). Computed tomography(CT) was carried out immediately after ESD and the next morning. Pain and abdominal distention were chronologically recorded using a 100-mm visual analogue scale(VAS). The volume of residual gas in the digestive tract was measured using CT imaging. RESULTS The incidence of ME immediately after ESD in the CO2 group was significantly lower than that in the Air group(17% vs 55%, P = 0.012). The incidence of ME the next morning was 8.3% vs 32% respectively(P= 0.066). There were no differences in pain scores or distention scores at any post-procedure time points. The volume of residual gas in the digestive tract immediately after ESD was significantly smaller in the CO2 group than that in the Air group(808 m L vs 1173 m L, P = 0.013).CONCLUSION CO2 insufflation during esophageal ESD significantly reduced postprocedural ME. CO2 insufflation also reduced the volume of residual gas in the digestive tract immediately after ESD, but not the VAS scores of pain and distention.

Carbon dioxide insufflation for endoscopic retrograde cholangiopancreatography:A meta-analysis and systematic review

AIM:To assess the safety and efficacy of carbon dioxide (CO2) insufflation during endoscopic retrograde cholangiopancreatography (ERCP). METHODS:The Cochrane Library, Medical Literature Analysis and Retrieval System Online, Excerpta Medica Database, Science Citation Index Expanded, Chinese Biomedical Literature Database, and references in relevant publications were searched up to December 2011 to identify randomized controlled trials (RCTs) comparing CO2 insufflation with air insufflation during ERCP. The trials were included in the review irrespec-tive of sample size, publication status, or language. Study selection and data extraction were performed by two independent authors. The meta-analysis was performed using Review Manager 5.1.6. A random-effects model was used to analyze various outcomes.Sensitivity and subgroup analyses were performed if necessary. R ESULTS:Seven double-blind RCTs involving a total of 818 patients were identified that compared CO2 insufflation (n = 404) with air insufflation (n = 401) during ERCP. There were a total of 13 post-random- ization dropouts in four RCTs. Six RCTs had a high risk of bias and one had a low risk of bias. None of the RCTs reported any severe gas-related adverse events in either group. A meta-analysis of 5 RCTs (n = 459) indicated that patients in the CO2 insufflation group had less post-ERCP abdominal pain and distension for at least 1 h compared with patients in the air insuf-flation group. There were no significant differences in mild cardiopulmonary complications [risk ratio (RR) = 0.43, 95% CI:0.07-2.66, P = 0.36], cardiopulmonary (e.g., blood CO2 level) changes [standardized mean difference (SMD) = -0.97, 95% CI: -2.58-0.63, P = 0.23], cost analysis (mean difference = 3.14, 95% CI:-14.57-20.85, P = 0.73), and total procedure time (SMD = -0.05, 95% CI:-0.26-0.17, P = 0.67) between the two groups. C ONCLUSION:CO2 insufflation during ERCP appears to be safe and reduces post-ERCP abdominal pain and discomfort.

Comparison between air and carbon dioxide insufflation in the endoscopic submucosal excavation of gastrointestinal stromal tumors

AIM:To evaluate the safety and efficacy of CO2 insufflation compared with air insufflation in the endoscopic submucosal excavation(ESE) of gastrointestinal stromal tumors.METHODS:Sixty patients were randomized to undergo endoscopic submucosal excavation,with the CO2 group(n = 30) and the air group(n = 30) undergoingCO2 insufflation and air insufflation in the ESE,respectively.The end-tidal CO2 level(pETCO2) was observed at 4 time points:at the beginning of ESE,at total removal of the tumors,at completed wound management,and 10 min after ESE.Additionally,the patients' experience of pain at 1,3,6 and 24 h after the examination was registered using a visual analog scale(VAS).RESULTS:Both the CO2 group and air group were similar in mean age,sex,body mass index(all P > 0.05).There were no significant differences in PetCO2 values before and after the procedure(P > 0.05).However,the pain scores after the ESE at different time points in the CO2 group decreased significantly compared with the air group(1 h:21.2 ± 3.4 vs 61.5 ± 1.7;3 h:8.5 ± 0.7 vs 42.9 ± 1.3;6 h:4.4 ± 1.6 vs 27.6 ± 1.2;24 h:2.3 ± 0.4 vs 21.4 ± 0.7,P < 0.05).Meanwhile,the percentage of VAS scores of 0 in the CO2 group after 1,3,6 and 24 h was significantly higher than that in the air group(60.7 ± 1.4 vs 18.9 ± 1.5,81.5 ± 2.3 vs 20.6 ± 1.2,89.2 ± 0.7 vs 36.8 ± 0.9,91.3 ± 0.8 vs 63.8 ± 1.3,respectively,P < 0.05).Moreover,the condition of the CO2 group was better than that of the air group with respect to anal exsufflation.CONCLUSION:Insufflation of CO2 in the ESE of gastrointestinal stromal tumors will not cause CO2 retention and it may significantly reduce the level of pain,thus it is safe and effective.

Continuous tracheal gas insufflation during protective mechanical ventilation in juvenile piglets with acute lung injury induced by endotoxin

Low tidal volume mechanical ventilation is difficult to correct hypoxemia, and prolonged inhalation of pure oxygen can lead to oxygen poisoning. We suggest that continuous tracheal gas insufflation （TGI） during protective mechanical ventilation could improve cardiopulmonary function in acute lung injury. Totally 12 healthy juvenile piglets were anesthetized and mechanically ventilated at PEEP of 2 cmH2O with a peak inspiratory pressure of 10 cmH2O. The piglets were challenged with lipopolysaccharide and randomly assigned into two groups （n=6 each group）： mechanical ventilation （MV） alone and TGI with continuous airway flow 2 I/min. FIO2 was set at 0.4 to avoid oxygen toxicity and continuously monitored with an oxygen analyzer. Tidal volume, ventilation efficacy index and mean airway resistant pressure were significantly improved in the TGI group （P〈0.01 or P〈0.05）. At 4 hours post ALl, pH decreased to below 7.20 in the MV group, and improved in the TGI group （P〈0.01）. Similarly, PaCO2 was stable and was significantly lower in the TGI group than in the MV group （P〈0.01）. PaO2 and PaO2/FIO2 increased also in the TGI group （P〈0.05）. There was no significant difference in heart rate, respiratory rate, mean artery pressure, central venous pressure, dynamic lung compliance and mean resistance of airway between the two groups. Lung histological examination showed reduced inflammation, reduced intra- alveolar and interstitial patchy hemorrhage, and homogenously expanded lungs in the TGI group. Continuous TGI during MV can significantly improve gas exchange and ventilation efficacy and may provide a better treatment for acute lung injury.

Is the type of insufflation a key issue in gastro-intestinal endoscopy?

Endoscopic procedures continue to play an emerging role in diagnosing and treating upper and lower gastrointestinal (GI) disorders. In particular, the introduction of colonoscopy in bowel cancer screening has underlined its promising role in decreasing the incidence of colorectal cancer and reducing tumour related mortality. To achieve these goals patients need to contemplate endoscopic examinations as painless and fearless procedures. The use of carbon dioxide (CO2) as an alternative insufflation gas in comparison to air has been considered as an essential key to improving patients’ acceptance in undergoing endoscopic procedures. CO2 is absorbed quickly through the bowel mucosa causing less luminal distension and potentially less abdominal pain. However, its exact role has not been defined completely. In particular, the beneficial use of CO2 in upper GI endoscopy and in sedated patients is still conflicting. In the present review, we aimed to assess the current evidence for using CO2 in endoscopy and to evaluate its potential role in the future.

Accuracy of carbon dioxide insufflation for endoscopic retrograde cholangiopancreatography using double-balloon endoscopy

BACKGROUND Retrograde cholangiopancreatography using double-balloon endoscopic retrograde cholangiography(DBERC)is a valuable technique to treat biliary stone and jejunobiliary anastomotic stenosis in patients with altered gastrointestinal anatomy.The accurate selection of the route at the anastomosis branch is one of the most important factors in reaching the target in a timely manner.AIM To determine the accuracy of carbon dioxide insufflation enterography(CDE)at the branch for selecting the correct route during DBERC.METHODS We enrolled 52 consecutive patients scheduled for DBERC at our institution from June 2015 to November 2017.Route selection via two methods(visual observation and CDE)was performed in each patient.We determined the correct rate of route selection using CDE.RESULTS Thirty-three patients had a jejunojejunal anastomosis and 19 patients had a gastrojejunal anastomosis.The therapeutic target region was reached in 50 patients.The mean procedure times from the teeth to the target(total insertion time),from the teeth to the branch,and from the branch to the target,and the mean total examination time were 15.2,5.0,8.2,and 60.3 min,respectively.The rate of correct route selection using visual observation and CDE were 36/52(69.2%)and 48/52(92.3%),respectively(P=0.002).The rate of correct route selection using CDE in patients with a jejunojejunal anastomosis was 29/33(87.8%),and the rate in patients with a gastrojejunal anastomosis was 19/19(100%).CONCLUSION CDE is helpful in selecting the route at the branch in the anastomosis for more timely access to the target in patients with altered gastrointestinal anatomy undergoing DBERC.

Oxygen insufflation via working channel in a fiberscope is a useful method: A case report and review of literature

BACKGROUND Fiberoptic bronchoscopic intubation is the gold standard for endotracheal intubation in difficult or compromised airway situations. However, oxygen insufflation through the working channel of a fiberscope is a controversial method because of the possibility of gastric distention and rupture during an awake fiberoptic bronchoscopic intubation, despite the advantages of preventing fogging of the fiberoptic bronchoscopic lens, blowing oral secretions away, and oxygenation of patients.CASE SUMMARY Here, we describe a case of cervical instability where we rapidly performed fiberoptic bronchoscopic intubation using oxygen insufflation through working channel of the broncoscopy to administer general anesthesia after two previous failures due to low visibility. A 50-year-old man with a non-specific medical history underwent emergency cervical spine surgery for posterior fusion of the C2 and C3 vertebrae. After two unsuccessful attempts at intubation using the fiberoptic broncoscopy, we performed it successfully using the oxygen insufflation via the working channel, instead of using suction to remove the secretion from the lens.CONCLUSION Oxygen insufflation via the working channel of thebroncoscopy is a useful method for assisting with difficult intubation cases.

Effect of surgical procedures on prostate tumor gene expression profiles

Current surgical treatment of prostate cancer is typically accomplished by either open radical prostatectomy （ORP） or robotic-assisted laparoscopic radical prostatectomy （RALRP）. Intra-operative procedural differences between the two surgical approaches may alter the molecular composition of resected surgical specimens, which are indispensable for molecular analysis and biomarker evaluation. The objective of this study is to investigate the effect of different surgical procedures on RNA quality and genome-wide expression signature. RNA integrity number （RIN） values were compared between total RNA samples extracted from consecutive LRP （n= 11） and ORP （n= 24） prostate specimens. Expression profiling was performed using the Agilent human whole-genome expression microarrays. Expression differences by surgicat type were analyzed by Volcano plot analysis and gene ontology analysis. Quantitative reverse transcription （RT）-PCR was used for expression validation in an independent set of LRP （n=8） and ORP （n=8） samples. The LRP procedure did not compromise RNA integrity. Differential gene expression by surgery types was limited to a small subset of genes, the number of which was smaller than that expected by chance. Unexpectedly, this small subset of differentially expressed genes was enriched for those encoding transcription factors, oxygen transporters and other previously reported surgery-induced stress-response genes, and demonstrated unidirectional reduction in LRP specimens in comparison to ORP specimens. The effect of the LRP procedure on RNA quality and genome-wide transcript levels is negligible, supporting the suitability of LRP surgical specimens for routine molecular analysis. Blunted in vivo stress response in LRP specimens, likely mediated by CO2 insufflation but not by longer ischemia time, is manifested in the reduced expression of stress-response genes in these specimens.

Severe gastric insufflation and consequent atelectasis caused by gas leakage using AIR-Q laryngeal mask airway:A case report

BACKGROUND The airways of patients undergoing awake craniotomy(AC)are considered“predicted difficult airways”,inclined to be managed with supraglottic airway devices(SADs)to lower the risk of coughing or gagging.However,the special requirements of AC in the head and neck position may deteriorate SADs’seal performance,which increases the risks of ventilation failure,severe gastric insufflation,regurgitation,and aspiration.CASE SUMMARY A 41-year-old man scheduled for AC with the asleep–awake–asleep approach was anesthetized and ventilated with a size 3.5 AIR-Q intubating laryngeal mask airway(LMA).Air leak was noticed with adequate ventilation after head rotation for allowing scalp blockage.Twenty-five minutes later,the LMA was replaced by an endotracheal tube because of a change in the surgical plan.After surgery,the patient consistently showed low tidal volume and was diagnosed with gastric insufflation and atelectasis using computed tomography.CONCLUSION This case highlights head rotation may cause gas leakage,severe gastric insufflation,and consequent atelectasis during ventilation with an AIR-Q intubating laryngeal airway.

Examination of Whey Degreasing by Modified Membrane Filtration

The largest amount of dairy by-products, especially the whey, comes from the manufacture of cheese. The whey proteins are used in several different industry technologies. The forage production is used for animal feeding in the forms of various flours mixed in feeds, and the food industry uses whey proteins as human nutrition, such as different dry soups, infant formulas and supplements. The fat components of whey may inhibit the efficient processing and might impair the use of whey in these technologies. Thus, the aim of the experiment was to investigate a cheap and economical separation of the lipid fraction of whey. This separation method was made by microfiltration, which is an inexpensive, effective and energy efficient method for this task. During the measurements, 0.2 μm and 0.45 μm microfiltration membranes were used in a laboratory tubular membrane filtration module, and the membrane separation method was combined and modified by using astatic mixer and/or air insufflation. The same pore size membranes were used in a vibrating membrane filtration equipment （VSEP）, too. The two different membrane filtration devices allowed the comparison of the effect of vibration and the effect of the static mixer and/or air insufflation. The flux values above 0.2 MPa transmembrane pressures strongly decreased on using the tubular membrane. Therefore, it can be determined that the use of the lower transmembrane pressures gave better flux combined with air insufflation and the use of static mixer. The flux values increased three times higher with using vibration during the microfiltration process than that without vibration. Comparing these methods, it can be concluded that the separation made on tubular membrane （0.2 μm） combined with statics mixer gave sufficient result according to the degreasing, retentions and flux values of the other components.

Effects of Laparoscopic Cholecystectomy on Intraocular Pressure

Purpose: To evaluate the effects of laparoscopic cholecystectomy in patients with gall stones under general anesthesia using carbon dioxide (CO2) insufflations on the intraocular pressure (IOP). Methods: The study was an observational case series, involved 24 non-glaucomatous patients with gall stones who underwent laparoscopic cholecystectomy surgery under general anesthesia using (CO2) insufflations in the period from January 2016 to April 2016 in Zagazig University Hospitals. IOP was measured preoperatively, intra-operatively and shortly postoperatively. Interpretation of the results was performed. Results: The study revealed that IOP was elevated significantly during laparoscopic cholecystectomy surgery (P < 0.001), as the mean preoperative IOP was (15.21 ± 1.61 mmHg) compared to intra-operative (24.55 ± 6.28 mmHg) and nearly returned to the normal level after 8 hours postoperatively (16.13 ± 2.44 mmHg). Conclusion: Laparoscopic cholecystectomy surgery elevated IOP significantly which is not favorable for glaucoma or ocular hypertension patients, especially for the old.

Measuring organ shift and deformation for port placement in robotassisted minimally invasive surgery

Objective:Port placement is a crucial pre-operative task in robot-assisted minimally invasive surgery.Due to the insufflation process,the abdominal shape is deformed while the internal organs are shifted in position.These changes need to be considered when determining the optimal port locations for the robotic manipulators.However,intra-operative medical image acquisition systems are not always available.In this study,we aim to estimate the shift extent of the abdominal organs in humans by measuring the changed volume and position of the abdominal organs before and after insufflation in three pigs.Methods:A 3D model of the abdomen and abdominal organs was reconstructed from 3D images of the pigs taken by an MRI scanner before and after insufflation.Position shift and shape changes of the abdominal organs after insufflation were determined.The corresponding shift in port location for the robotic manipulators was determined based on the abdominal model.Results:Organ movements as a result of insufflation ranged from 6.37±0.10 cm for the spleen,to 1.64±0.22 cm for the liver.Even a slight planar motion of the target organ(e.g.,1.33±0.06 cm,2.38±0.21 cm in X-Y plane for the left kidney)can shift the access port for the robot manipulator by about 1.6 cm on the abdominal surface.Conclusions:The target organs’motion due to insufflation is a critical factor in determining port locations in robot-assisted minimally invasive surgery.

Efficacy of continuous tracheal gas insufflation in spontaneously breathing canine with acute lung injury

Objective To investigate the effects of continuous tracheal gas insufflation (CTGI) combined with biphasic intermittent positive airway pressure (BIPAP) ventilation on dogs with spontaneous breathing. Methods Eight canine models with oleic acid induced lung injury and spontaneous breathing were ventilated in a random order by Evita 2 (Drager Inc., Germany) in modes of BIPAP (BIPAP group) and BIPAP with CTGI flow rate of 3, 6 and 9?L/min (T3, T6 and T9 groups), respectively. The setting parameters of BIPAP were fiction of inspired oxygen 60%, inspiratory to expiratory ratio 1∶1, respiratory rate 20 and positive end expiratory pressure 5?cm?H2O. Arterial and mixed venous blood gas, lung mechanics, systemic and pulmonary hemodynamics status were monitored at the same level of PaCO2 obtained by adjusting peak inspiratory pressure of BIPAP. Results Peak inspiratory pressure in the T6 group (14±4?cm?H2O) and in the T9 group (11±3?cm?H2O) were significantly lower than that of BIPAP (20±5?cm?H2O, P<0.01), but there was no significant difference among the T3, T6 and T9 groups or between the T3 and BIPAP groups. PaO2, mean artery blood pressure, mean pulmonary artery pressure, pulmonary artery wedge pressure, cardiac ouput, oxygen delivery and oxygen consumption all remained unchanged in four different conditions.Conclusions Using BIPAP combined with CTGI does not cause asynchrony between ventilator and spontaneous breathing, but significantly decreases airway pressure with no influence on hemodynamics and oxygenation. Therefore, BIPAP with CTGI may be a useful support technique, especially in cases where the airway pressure should be limited.

Effects of continuous tracheal gas insufflation during pressure limited ventilation on pulmonary surfactant in rabbits with acute lung injury

Background Pulmonary surfactant dysfunction may contribute to the development of ventilator induced lung injury （VILI）. Tracheal gas insuffiation （TGI） is a technique in which fresh gas is introduced into the trachea and augment ventilation by reducing the dead space of ventilatory system, reducing ventilatory pressures and tidal volume （VT） while maintaining constant partial arterial CO2 pressure （PaCO2）. We hypothesised that TGI limited peak inspiratory pressure （PIP） and VT and would minimize conventional mechanical ventilation （CMV） induced pulmonary surfactant dysfunction and thereby attenuate VILI in rabbits with acute lung injury （ALI）. Methods ALI was induced by intratracheal administration of lipopolysaccharide in anaesthetized, ventilated healthy adult rabbits randomly assigned to continuous TGI at 0.5 L/min （TGI group） or CMV group （n=8 for each group）, and subsequently ventilated with limited PIP and VT to maintain PaCO2 within 35 to 45 mmHg for 4 hours. Physiological dead space to VT ratio （VD/VT）, dynamic respiratory compliance （Cdyn） and partial arterial O2 pressure （PaO2） were monitored. After ventilation, lungs were analysed for total phospholipids （TPL）, total proteins （TP）, pulmonary surfactant small to large aggregates ratio （SA/LA） in bronchoalveolar lavage fluid （BALF） and for determination of alveolar volume density （Vv）, myeloperoxidase and interleukin （IL）-8. Results TGI resulted in significant （P〈0.05 or P〈0.01） decrease in PIP [（22.4±1.8） cmH20 vs （29.5±1.1） cmH2O], VT [（6.9±1.3） ml/kg vs （9.8±1.11） ml/kg], VD/VT [（32±5）% vs （46±2）%], TP [（109±22） mg/kg vs （187±25） mg/kg], SA/LA （2.5±0.4 vs 5.4±0.7）, myeloperoxidase [（6.2±0.5） U/g tissue vs （12.3±0.8） U/g tissue] and IL-8 [（987±106） ng/g tissue vs （24±3） mN/m] of BALF, and significant （P〈0.05） increase in Cdyn [（0.47±0.02） ml·cmH2O^-1·kg^-1 vs （0.31±0.02） ml·cmH2O^-1·kg^-1], PaO2 [（175±24） mmHg vs （135±26） mmHg], TPL/TP （52±8 vs 33±11） and Vv （0.65±0.05 vs 0.44±0.07） as compared with CMV. Conclusions In this animal model of ALI, TGI decreased ventilatory requirements （PIP, VT and VD/VT）, resulted in more favourable alveolar pulmonary surfactant composition and function and less severity of lung injury than CMV. TGI in combination with pressure limited ventilation may be a lung protective strategy for ALI.