Use of airway pressure-based indices to detect high and low inspiratory effort during pressure support ventilation: a diagnostic accuracy study.

BACKGROUND: Assessment of the patient's respiratory effort is essential during assisted ventilation. We aimed to evaluate the accuracy of airway pressure (Paw)-based indices to detect potential injurious inspiratory effort during pressure support (PS) ventilation. METHODS: In this prospective diagnostic accuracy study conducted in four ICUs in two academic hospitals, 28 adult acute respiratory failure patients undergoing PS ventilation were enrolled. A downward PS titration was conducted from 20 cmH2O to 2 cmH2O at a 2 cmH2O interval. By performing an end-expiratory airway occlusion maneuver, the negative Paw generated during the first 100 ms (P0.1) and the maximal negative swing of Paw (∆Pocc) were measured. After an end-inspiratory airway occlusion, Paw reached a plateau, and the magnitude of change in plateau from peak Paw was measured as pressure muscle index (PMI). Esophageal pressure was monitored and inspiratory muscle pressure (Pmus) and Pmus-time product per minute (PTPmus/min) were used as the reference standard for the patient's effort. High and low effort was defined as Pmus > 10 and < 5 cmH2O, or PTPmus/min > 200 and < 50 cmH2O s min-1, respectively. RESULTS: A total of 246 levels of PS were tested. The low inspiratory effort was diagnosed in 145 (59.0%) and 136 (55.3%) PS levels using respective Pmus and PTPmus/min criterion. The receiver operating characteristic area of the three Paw-based indices by the respective two criteria ranged from 0.87 to 0.95, and balanced sensitivity (0.83-0.96), specificity (0.74-0.88), and positive (0.80-0.91) and negative predictive values (0.78-0.94) were obtained. The high effort was diagnosed in 34 (13.8%) and 17 (6.9%) support levels using Pmus and PTPmus/min criterion, respectively. High receiver operating characteristic areas of the three Paw-based indices by the two criteria were found (0.93-0.95). A high sensitivity (0.80-1.00) and negative predictive value (0.97-1.00) were found with a low positive predictive value (0.23-0.64). CONCLUSIONS: By performing simple airway occlusion maneuvers, the Paw-based indices could be reliably used to detect low inspiratory efforts. Non-invasive and easily accessible characteristics support their potential bedside use for avoiding over-assistance. More evaluation of their performance is required in cohorts with high effort.

Validation of the flow index to detect low inspiratory effort during pressure support ventilation.

BACKGROUND: Bedside assessment of low levels of inspiratory effort, which are probably insufficient to prevent muscle atrophy, is challenging. The flow index, which is derived from the analysis of the inspiratory portion of the flow-time waveform, has been recently introduced as a non-invasive parameter to evaluate the inspiratory effort. The primary objective of the present study was to provide an external validation of the flow index to detect low inspiratory effort. METHODS: Datasets containing flow, airway pressure, and esophageal pressure (Pes)-time waveforms were obtained from a previously published study in 100 acute brain-injured patients undergoing pressure support ventilation. Waveforms data were analyzed offline. A low inspiratory effort was defined by one of the following criteria, work of breathing (WOB) less than 0.3 J/L, Pes-time product (PTPes) per minute less than 50 cmH2O•s/min, or inspiratory muscle pressure (Pmus) less than 5 cmH2O, adding "or occurrence of ineffective effort more than 10%" for all criteria. The flow index was calculated according to previously reported method. The association of flow index with Pes-derived parameters of effort was investigated. The diagnostic accuracy of the flow index to detect low effort was analyzed. RESULTS: Moderate correlations were found between flow index and WOB, Pmus, and PTPes per breath and per minute (Pearson's correlation coefficients ranged from 0.546 to 0.634, P < 0.001). The incidence of low inspiratory effort was 62%, 51%, and 55% using the definition of WOB, PTPes per minute, and Pmus, respectively. The area under the receiver operating characteristic curve for flow index to diagnose low effort was 0.88, 0.81, and 0.88, for the three respective definition. By using the cutoff value of flow index less than 2.1, the diagnostic performance for the three definitions showed sensitivity of 0.95-0.96, specificity of 0.57-0.71, positive predictive value of 0.70-0.84, and negative predictive value of 0.90-0.93. CONCLUSIONS: The flow index is associated with Pes-based inspiratory effort measurements. Flow index can be used as a valid instrument to screen low inspiratory effort with a high probability to exclude cases without the condition.

Effect of rs4719839 polymorphism on risk of ventilator-associated pneumonia, expression of microRNA-148 and autophagy-related 16-like 1 (ATG16L1).

MiR-148 is a negative regulator of autophagy 16-like 1 (ATG16L1), a gene implicated in the pathogenesis of ventilator-associated pneumonia (VAP). Therefore, the role of miR-148 polymorphism in the pathogenesis of VAP was studied here. The expression of miR-148, ATG16L1, Beclin-I, LC3-II, TNF-α and IL-6 in serum and peripheral blood mononuclear cells (PBMCs) of VAP patients was detected to study their relationship in the pathogenesis of VAP. Chronic obstructive pulmonary disease patients carrying the AA/AG genotypes of miR-148 rs4719839 single nucleotide polymorphism (SNP) were more prone to VAP due to the higher expression of miR-148, TNF-α and IL-6 along with suppressed expression of ATG16L1, Beclin-I and LC3-II in their serum and PBMCs. Transfection of miR-148 mimics to primary PBMCs genotyped as GG and AA decreased the expression of ATG16L1, Beclin-I and LC3-II. Finally, cells carrying the AA genotype of rs4719839 SNP were more sensitive to the role of LPS stimulation in suppressing ATG16L1, Beclin-I and LC3-II expression while activating TNF-α and IL-6 expression. Our work presented detailed evidence, suggesting that the rs4719839 polymorphism can affect the risk of VAP.

IL-17A-producing T cells exacerbate fine particulate matter-induced lung inflammation and fibrosis by inhibiting PI3K/Akt/mTOR-mediated autophagy.

Fine particulate matter (PM2.5) is the primary air pollutant that is able to induce airway injury. Compelling evidence has shown the involvement of IL-17A in lung injury, while its contribution to PM2.5-induced lung injury remains largely unknown. Here, we probed into the possible role of IL-17A in mouse models of PM2.5-induced lung injury. Mice were instilled with PM2.5 to construct a lung injury model. Flow cytometry was carried out to isolate γδT and Th17 cells. ELISA was adopted to detect the expression of inflammatory factors in the supernatant of lavage fluid. Primary bronchial epithelial cells (mBECs) were extracted, and the expression of TGF signalling pathway-, autophagy- and PI3K/Akt/mTOR signalling pathway-related proteins in mBECs was detected by immunofluorescence assay and Western blot analysis. The mitochondrial function was also evaluated. PM2.5 aggravated the inflammatory response through enhancing the secretion of IL-17A by γδT/Th17 cells. Meanwhile, PM2.5 activated the TGF signalling pathway and induced EMT progression in bronchial epithelial cells, thereby contributing to pulmonary fibrosis. Besides, PM2.5 suppressed autophagy of bronchial epithelial cells by up-regulating IL-17A, which in turn activated the PI3K/Akt/mTOR signalling pathway. Furthermore, IL-17A impaired the energy metabolism of airway epithelial cells in the PM2.5-induced models. This study suggested that PM2.5 could inhibit autophagy of bronchial epithelial cells and promote pulmonary inflammation and fibrosis by inducing the secretion of IL-17A in γδT and Th17 cells and regulating the PI3K/Akt/mTOR signalling pathway.

Predictive model for acute respiratory distress syndrome events in ICU patients in China using machine learning algorithms: a secondary analysis of a cohort study.

BACKGROUND: To develop a machine learning model for predicting acute respiratory distress syndrome (ARDS) events through commonly available parameters, including baseline characteristics and clinical and laboratory parameters. METHODS: A secondary analysis of a multi-centre prospective observational cohort study from five hospitals in Beijing, China, was conducted from January 1, 2011, to August 31, 2014. A total of 296 patients at risk for developing ARDS admitted to medical intensive care units (ICUs) were included. We applied a random forest approach to identify the best set of predictors out of 42 variables measured on day 1 of admission. RESULTS: All patients were randomly divided into training (80%) and testing (20%) sets. Additionally, these patients were followed daily and assessed according to the Berlin definition. The model obtained an average area under the receiver operating characteristic (ROC) curve (AUC) of 0.82 and yielded a predictive accuracy of 83%. For the first time, four new biomarkers were included in the model: decreased minimum haematocrit, glucose, and sodium and increased minimum white blood cell (WBC) count. CONCLUSIONS: This newly established machine learning-based model shows good predictive ability in Chinese patients with ARDS. External validation studies are necessary to confirm the generalisability of our approach across populations and treatment practices.

Integrated genomic analysis identifies clinically relevant subtypes of renal clear cell carcinoma.

BACKGROUND: Renal cell carcinoma (RCC) account for over 80% of renal malignancies. The most common type of RCC can be classified into three subtypes including clear cell, papillary and chromophobe. ccRCC (the Clear Cell Renal Cell Carcinoma) is the most frequent form and shows variations in genetics and behavior. To improve accuracy and personalized care and increase the cure rate of cancer, molecular typing for individuals is necessary. METHODS: We adopted the genome, transcriptome and methylation HMK450 data of ccRCC in The Cancer Genome Atlas Network in this research. Consensus Clustering algorithm was used to cluster the expression data and three subtypes were found. To further validate our results, we analyzed an independent data set and arrived at a consistent conclusion. Next, we characterized the subtype by unifying genomic and clinical dimensions of ccRCC molecular stratification. We also implemented GSEA between the malignant subtype and the other subtypes to explore latent pathway varieties and WGCNA to discover intratumoral gene interaction network. Moreover, the epigenetic state changes between subgroups on methylation data are discovered and Kaplan-Meier survival analysis was performed to delve the relation between specific genes and prognosis. RESULTS: We found a subtype of poor prognosis in clear cell renal cell carcinoma, which is abnormally upregulated in focal adhesions and cytoskeleton related pathways, and the expression of core genes in the pathways are negatively correlated with patient outcomes. CONCLUSIONS: Our work of classification schema could provide an applicable framework of molecular typing to ccRCC patients which has implications to influence treatment decisions, judge biological mechanisms involved in ccRCC tumor progression, and potential future drug discovery.

[Testicular malignant Leydig cell tumor: A case report].

OBJECTIVE: To investigate the clinicopathological features of testicular malignant Leydig cell tumor (TMLCT) and improve the non-invasive diagnosis of the disease. METHODS: We retrospectively analyzed the clinicopathological data on a case of TMLCT, detected the circulating tumor cells (CTC) in the peripheral venous blood, and reviewed the related literature. RESULTS: The patient, a 47-year-old male, underwent radical orchidoepididymectomy under general anesthesia. Postoperative pathology confirmed the lesion to be TMLCT, which was mainly composed of Leydig cells and suspected with vessel carcinoma embolus. Immunohistochemistry showed the tumor cells to be positive for α-inhibin, Ki67, CD30, vimentin, EMA, and PLAP, but negative for CK, CK7, S100, CD10, SMA, Des, AFP, hCG, CEA, CK19, CD117, Oct-4, LCA, CD20, Pax-5, CD3, and CD43. Two CTCs were detected in the peripheral venous blood. The patient received 3 courses of chemotherapy for retroperitoneal multiple lymph nodes metastasis post-operatively. Subsequent CT imaging manifested no obvious reduction of the retroperitoneal lymph nodes and consequently the patient again underwent retroperitoneal lymphadenectomy and cryoablation. At 8 months after treatment, CT examination revealed notably enlarged retroperitoneal lymph nodes with the right adrenal gland evidently invaded. CONCLUSION: TMLCT is an extremely rare sex-gonad stromal tumor with high malignancy and poor prognosis, and CTCs may be used for its early diagnosis and prognostic prediction.

[The impact of early hypoxemia on the prognosis of patients undergone general anesthesia patients in intensive care unit].

OBJECTIVE: To form the strategy of prevention of postoperative pulmonary complication, investigate the incidence of early hypoxemia after general anesthesia for surgery in intensive care unit (ICU), and assess its impact on the prognosis of patients. METHODS: Clinical data of patients who were directed transferred to ICU after general anesthesia for selective surgery during October 2011 to June 2012 were analyzed retrospectively. According to the oxygenation index (PaO2/FiO2) obtained in 1 hour after ICU admission, patients were divided into three groups, normal blood oxygen level (n=134, PaO2/FiO2>300 mm Hg, 1 mm Hg=0.133 kPa), mild hypoxia (n=88, PaO2/FiO2 200-300 mm Hg) and moderate to severe hypoxia (n=49, PaO2/FiO2≤200 mm Hg) groups. Duration of mechanical ventilation, ICU stay days, postoperative hospital stay days, and duration of oxygen therapy were compared among three groups. RESULTS: Two hundred and seventy-one patients were included. There were no statistical differences in gender, age, duration of operation, type of operation, and postoperative extubation. The incidence rate of hypoxemia (PaO2/FiO2≤300 mm Hg) was 50.6%. Duration of mechanical ventilation was significantly prolonged in moderate to severe hypoxia group as compared with normal blood oxygen group [20.3 (13.0, 46.1) hours vs. 12.5 (6.0, 17.5) hours, D=40.803, P=0.005], the ratio of duration of mechanical ventilation longer than 24 hours was significantly higher in moderate to severe hypoxia group compared with normal blood oxygen and mild hypoxia groups (44.4% vs. 8.8%, 16.1%, χ(2)1=21.394, P2=0.000; χ(2)2=9.368, P2=0.002). The ICU stay was significantly longer in moderate to severe hypoxia group than normal blood oxygen and mild hypoxia groups [44.5 (21.5, 121.5) hours vs. 22.0 (18.0, 46.5) hours, 21.8 (19.0, 66.9) hours, D1=54.302, P1=0.000; D2=44.171, P2=0.005]. Compared with normal blood oxygen group, postoperative hospital stay days and duration of oxygen therapy were significantly longer in moderate to severe hypoxia group [postoperative length of stay: 15.0 (12.0, 21.5) days vs. 9.0 (12.0, 16.0) days, D=40.851, P=0.005; duration of oxygen therapy: 170.0 (97.5, 307.5) hours vs. 89.0 (47.8, 192.0) hours, D=45.049, P=0.002]. CONCLUSIONS: The incidence of hypoxemia postoperative patients after general anesthesia is high when transferred to ICU. PaO2/FiO2≤200 mm Hg was closely related to prolonged duration of mechanical ventilation, ICU stay days, postoperative hospital stay days, and duration of oxygen therapy.

[The polarization characteristics distribution and correction method of the polarization coupling error in ocean remote sensing system].

With the development of the quantitative researches using ocean color remote sensing data sets, study on reducing the uncertainty of the response of the ocean color remote sensors to the polarization characteristics of the target has been attracting more and more attention recently. Taking MODIS as an example, the polarization distribution in the whole field of view was analyzed. For the atmosphere path radiance and the apparent radiance considering the coupling between ocean surface and atmosphere, the polarization distribution has a strong relation with the imaging geometry. Compared to the contribution of the polarization from the rough sea surface, the contribution from the atmosphere is dominated. Based on the polarization characteristics in the field of view, the influence of the polarization coupling error on the quality of the satellite data was studied with the assumption of different polarization sensitivities. It was found that errors due to polarization sensitivity in the field of view are lower than water leaving radiance only when the polarization sensitivity is less than 2%. And in this case it can meet the need of the retrieval of water leaving radiative products. The method of the compensation for the polarization coupling error due to the atmosphere is proposed, which proved to be effective to improve the utilization of satellite data and the accuracy of measured radiance by remote sensor.

Protective effect of magnolol on TBHP-induced injury in H460 cells partially via a p53 dependent mechanism.

The aim is to investigate the effect of Magnolol preserved H460 cells from an oxidative agent tert-butylhydroperoxide (TBHP)-induced cell death. Magnolol augmented cell survival ratio after TBHP challenged. The protective action of this drug was more efficacious than that of N-acetylcysteine (NAC) which is a putative antioxidant. DNA damage, detected by the comet assay, was diminished after treatment of Magnolol. The cells viability decreased after treatment with 0.15 mM TBHP for 24 h, accompanied by inducing apoptotic death of the cells. Cytotoxicity and apoptosis induced by TBHP were significantly inhibited or attenuated after pretreatment with 20 microM Magnolol. Magnolol contributes to the cells survival through downregulated the p53 phosphorylation and PTEN expression, and upregulated Akt phosphorylation. Taken together, Magnolol was effective against DNA single strand breaks (SSB) formation, cytotoxicity and lipid peroxidation induced by TBHP, and its effects on p53 phosphorylation, PTEN and Akt phosphorylation were due to its antioxidative function, and partially via a p53 dependent mechanism in this protective effects.

[Study of continuous hemodynamics monitoring techniques in patients with mechanical ventilation].

OBJECTIVE: To elucidate the relativity among three kinds of continuous hemodynamics monitoring techniques: thermodilution via Swan-Ganz catheter, pulse contour analysis method (PiCCO), partial CO(2) rebreathing method (non invasive cardiac output, NICO), in patients with mechanical ventilation. METHODS: In 13 patients with respiratory failure due to different causes, hemodynamics were continuously monitored with Swan-Ganz catheterization, PiCCO, NICO simultaneously. The therapeutic measures and the type of ventilator were similar. Data were collected at the same time points to compare the relativity among these three kinds of monitor. RESULTS: Linear relative analysis showed a good relativity in PiCCO/Swan-Ganz (r=0.883), NICO/Swan-Ganz (r=0.853) and PiCCO/NICO (r=0.857) in cardiac index (CI). CONCLUSION: PiCCO and NICO can be used as reliable measure to monitor ventilated patients bedside in intensive care unit (ICU), thus offering an assistance to optimize therapeutic strategy.

[Effect on hemodynamics during different modes of low assist ventilation].

OBJECTIVE: To observe the effect on mechanical ventilation with biphasic positive airway pressure (BIPAP), pressure support ventilation (PSV) and proportional pressure support (PPS) modes on hemodynamics in patients with either normal cardiac function or impaired cardiac function in order to optimize the time to wean mechanical ventilation in patients with severe cardiac dysfunction. METHODS: Non-invasive cardiac output (NICO) monitoring was instituted in patients 32 with respiratory failure due to different causes, when spontaneous respiration was restored, and they were separated into two groups depending on whether the cardiac index (CI) was normal (CI> or =2.0 L.min(-1).m(-2)) or not (CI<2.0 L.min(-1).m(-2)). The effects of BIPAP, PSV and PPS modes on changes in hemodynamics were compared between two groups. RESULTS: (1) In patients with normal cardiac function, CO, CI, stroke volume (SV), pulmonary capillary blood flow (PCBF) were significant higher in PSV and PPS modes than BIPAP mode, and they were highest with PPS mode, but no significant difference compared with PSV. Surround vascular resistance (SVR) was reduced significantly in PPS mode compared with BIPAP, but no significant difference was found compared with PSV. (2) In patients with cardiac dysfunction, CO, CI increased gradually when ventilated in BIPAP, PSV, PPS modes and significant difference was found among three groups. In PPS mode, CO and CI were highest. (3) The trends of peak airway pressure (Ppeak) and mean airway pressure (Pmean) were degressive in three groups. In both normal cardiac function group and cardiac dysfunction group, significant difference was found in PSV and PPS modes compared with BIPAP. Ppeak was lowest in PPS mode in cardiac dysfunction group, and there was significant difference compared with the other groups. (4) The ventilated time was significant reduced in PPS mode compared with PSV. (5) In normal cardiac function group, instinct positive end expiratory pressure (PEEPi) showed degressive trend among three different modes, and it was lowest in PPS mode, with significant difference compared with the other two groups. CONCLUSION: In PPS mode, the effect to hemodynamics in patients with severe cardiac dysfunction is minimal, so it is suitable as a weaning mode in this groups of patients.

[Clinical study of the setting of positive end expiratory pressure in patients with acute cardiogenic pulmonary edema during mechanical ventilation].

OBJECTIVE: To compare the effects on hemodynamics and lung mechanics when different positive end expiratory pressure (PEEP) levels were used in acute cardiac pulmonary edema. METHODS: Thirty-nine patients with respiratory failure and treated with mechanical ventilation were divided into two groups according to cardiac index (CI). The changes of hemodynamics [including cardiac output (CO), CI, pulmonary capillary blood flow (PCBF), central venous pressure (CVP), surround vascular resistance (SVR)], lung mechanical variables [intrinsic positive end expiratory pressure (PEEPi), peak inspiratory pressure (Ppeak), mean of airway pressure (Pmean), minute volume (MV), alveolar tidal volume (Vtalv)], percutaneous saturation of oxygen (SpO(2)) and blood pressure (BP) were determined with when selected different PEEP levels under the bi-level positive airway pressure (BIPAP) mode in normal cardiac function group (n=18, CI> or =2.0 L.min(-1).m(-2)) and poor cardiac function group (n=20, CI<2.0 L.min(-1)xm(-2)). RESULTS: In normal cardiac function group, PEEP has no effect on hemodynamics when varied from 0-13 cm H(2)O (1 cm H(2)O=0.098 kPa), and Ppeak and PEEPi increased with the elevation of PEEP. Resistance of airway (R) fell when PEEP was increased. However, in poor cardiac function group SVR, CO, CI showed curvilinear changes with an increase in PEEP, and CO, CI were high when PEEP changed from 0 to 7 cm H(2)O, but dropped markedly when PEEP was increased in 13 cm H(2)O, while the changes of SVR was the reverse of CO and CI. The effects on lung mechanics varied relatively smaller range when PEEP was set between 5-7 cm H(2)O, and the burden of breathing was slight. CONCLUSION: The mode of artificial ventilation should be adjusted according to the changes in hemodynamics and lung mechanics. PEEP should be individualized, and 5-7 cm H(2)O (normally below 10 cm H(2)O) is suitable.

[Establishment of a mathematical model of static pressure-volume curve in acute respiratory distress syndrome].

OBJECTIVE: To explore the use of second derivate in seeking the inflection points of pressure-volume (P-V) curves and compare it with the step-by-step regression method. METHODS: Under general anesthesia, tracheotomy was done in 6 adult sheep, warm physiological saline was used to lavage the respiratory, followed by alveolar lavaged via tract through bronchofiberscope to reproduce acute respiratory distress syndrome (ARDS). The low flow technique was used to trace the P-V curves before and after the saline lavage, and features of the curves were analyzed with the software of Findgraph. RESULTS: The above two methods fit the P-V data well with good accuracy both in inflation and deflation limbs in normal and ARDS animals. From the graph of second derivate, the characteristic points of the P-V curves could be exactly obtained, and the low inflection points obtained by this method were well correlated with lower inflection point (LIP) +2 cm H(2)O (1 cm H(2)O=0.098 kPa) obtained by step-by-step regression method. CONCLUSION: The graph of second derivate gained from P-V curves is useful to describe the inflection points, so that it can be helpful in instructing in setting the required parameters of the ventilator in the treatment of ARDS.

[Effects of different levels of positive end expiratory pressure on lung recruitment and hemodynamics after sustained inflation in acute respiratory distress syndrome in sheep].

OBJECTIVE: To study the effects of different levels of positive end expiratory pressure (PEEP) on recruitment and hemodynamics after sustained inflation in acute respiratory distress syndrome (ARDS) in sheep. METHODS: Twelve adult sheep were anaesthetized and ARDS was induced by lung lavage with warm normal saline. Pressure-volume (P-V) curves were traced using the low flow technique and the upper inflection point (UIP) was determined. Sustained inflation was exercised at the pressure of 5 cm H(2)O (1 cm H(2)O=0.098 kPa) below UIP, and the sheep were divided into groups according to different PEEP levels (PEEP5, PEEP10, PEEP15, PEEP20). Hemodynamics and lung mechanics values were recorded during the 2 hours of recruitment, and biopsy was performed at the end of the trial. RESULTS: There was no effect on hemodynamics and recruitment in 2 hours in PEEP5 and PEEP10 groups, but oxygenation was found to be decreased in PEEP5 group, and focal alveolar collapse was found in pathological examination. When the PEEP level reached 15 cm H(2)O, there was significant elevation in central venous pressure (CVP), and cardiac index (CI) fell remarkably, but oxygenation index and lung mechanics were improved and stable in 2 hours. CONCLUSION: Our study demonstrates that it can obviously improve oxygenation when PEEP is set at 10-20 cm H(2)O, oxygenation can be obviously improved, with little disturbance to hemodynamics in case cardiac function is normal.

[Experimental study of the safety of sustained inflation strategy in acute respiratory distress syndrome in sheep].

OBJECTIVE: To evaluate the effects of lung recruitment maneuver (RM) on hemodynamics and lung structure with sustained inflation (SI) in acute respiratory distress syndrome (ARDS) in sheep, to look for a safe range of pressure and time of SI. METHODS: Fourteen anaesthetized sheep were subjected to lung lavage through a broncho-fibroscope to reproduce ARDS, and quasi-static pressure-volume (P-V) curves were obtained with low flow technique. The upper inflection point (UIP) and the lower inflection point (LIP) were found, and then 5 cm H(2)O (1 cm H(2)O=0.098 kPa) below UIP, UIP, 10 cm H(2)O above UIP, 20 cm H(2)O above UIP as the peak pressure of SI were selected as the test pressure. They were randomized to four groups (U-5, U+0, U+10, U+20). The duration of SI was 60 seconds. Hemodynamics and oxygenation indexes were monitored and recorded during and after SI until the study was terminated 2 hours later, then CT and lung tissue biopsy were performed. RESULTS: Pneumothorax was found in U+20 groups, resulting in the death of sheep. Hemodynamics was affected significantly in other groups during SI. In U+10 groups, cardiac output (CO) and cardiac index (CI) were lowered at 15 seconds after RM began, and recovered slowly after RM; in U+0 group and U-5 group, the entire RM could be carried out to the end, and biopsy showed bullous emphysema in U+0 group. CONCLUSION: The impairment of the hemodynamics and damage to the lung structure should be prevented when RM is performed in ARDS patients, and the inflation pressure should be limited within the range of UIP or 5 cm H(2)O under UIP to avoid adverse effect on hemodynamics.

[Clinical comparative study of airway pressure release ventilation and continuous positive airway pressure ventilation].

OBJECTIVE: To evaluate the effects of airway pressure release ventilation (APRV) and continuous positive airway pressure (CPAP) on hemodynamics, lung mechanics and oxygen metabolism index. METHODS: Fifteen ARDS cases ventilated and monitored by the pulse contour method (PiCCO) were randomized into APRV group and CPAP group, then lung recruitment maneuver (RM) was executed every 4 hours. In APRV group, Phigh was 35 cm H(2)O (1 cm H(2)O=0.098 kPa) and Plow was set at lower inflection point (LIP) of the static pressure-volume (P-V) curve. In CPAP group, CPAP was also 35 cm H(2)O. The duration of RM in both groups was 40 seconds. Before and after RM the parameters of lung mechanics, oxygen metabolism index and hemodynamics were monitored and compared. RESULTS: (1) In APRV group cardiac index (CI) was decreased slightly during RM with shorter duration than CPAP group. (2) The parameters of lung mechanics and oxygenation were improved significantly in both groups, and they were better in APRV group than CPAP group. CONCLUSION: In APRV group sedation can be abstained during RM, and the hemodynamics were hardly disturbed. Improvement of lung mechanics and oxygenation is much better with APRV than CPAP mode.