Estimation of lung recruitment characteristics using the static pressure-volume curve of lungs / 生物医学工程学杂志

Mechanical ventilation is an importmant life-sustaining treatment for patients with acute respiratory distress syndrome. Its clinical outcomes depend on patients' characteristics of lung recruitment. Estimation of lung recruitment characteristics is valuable for the determination of ventilatory maneurvers and ventilator parameters. There is no easily-used, bedside method to assess lung recruitment characteristics. The present paper proposed a method to estimate lung recruitment characteristics from the static pressure-volume curve of lungs. The method was evaluated by comparing with published experimental data. Results of lung recruitment derived from the presented method were in high agreement with the published data, suggesting that the proposed method is capable to estimate lung recruitment characteristics. Since some advanced ventilators are capable to measure the static pressure-volume curve automatedly, the presented method is potential to be used at bedside, and it is helpful for clinicians to individualize ventilatory manuevers and the correpsonding ventilator parameters.

Experimental study on liver injury induced by intraperitoneal hypertension under mechanical ventilation / 中华危重病急救医学

Objective:To investigate the effects of mechanical ventilation on liver cytological and enzymatic indexes in abdominal compartment syndrome (ACS) by establishing a porcine model of abdominal hypertension.Methods:Six healthy adult pigs were selected. After general anesthesia, they were intubated and given ventilator assisted breathing. The breathing mode was volume controlled ventilation (VCV), tidal volume (VT) 10 mL/kg, respiratory rate (RR) 16 time/min, fraction of inspiration oxygen (FiO 2) 0.40, positive end expiratory pressure (PEEP) 5 cmH 2O (1 cmH 2O = 0.098 kPa). Intraperitoneal pressure was simulated by injecting normal saline into the pressurized water sac, and the pressure was measured once every 50 mL of normal saline. 5 mL of blood was collected from ear vein every 1 hour before and 4 hours after operation for liver enzyme examination. 4 hours after operation, the animals were sacrificed and the liver was collected to observe pathological changes under light microscope. Results:Six pigs were successfully modeled. The RR and heart rate (HR) of the animals remained stable. No one suffered from barotrauma or death during the experiment. There was a positive correlation between abdominal pressure and abdominal volume increase (r 2 = 0.839 6, P = 0.003 7). There were no significant differences in the levels of alanine aminotransferase (ALT), alkaline phosphatase (ALP) and cholinesterase (ChE) preoperative and 1, 2, 3, 4 hours after operation. As time went on, aspartate aminotransferase (AST) increased first and then decreased, and increased significantly at 1 hour after operation (U/L: 46.84±8.57 vs. 23.35±5.14, P < 0.05), and decreased significantly 2, 3, 4 hours after operation (U/L: 16.33±3.58, 14.54±3.35, 15.44±3.21 vs. 23.35±5.14, all P < 0.05). The level of γ-glutamyltranspeptidase (GGT) increased and then decreased, but there was significant difference only at 1 hour after operation, compared with baseline (U/L: 101.20±17.79 vs. 51.34±9.13, P < 0.05). Under the light microscope, there were dilation and congestion of interlobular vein, dilation of interlobular bile duct, hyperplasia of small bile duct, hyperplasia of connective tissue in portal area, infiltration of a large number of acute and chronic inflammatory cells, swelling of hepatocytes, light staining of cytoplasm, balloon like transformation of some cells, and punctate necrosis. Conclusion:Abdominal hypertension under mechanical ventilation can cause obvious enzyme changes and cytological damage of liver.

Application of dynamic pressure-volume curve in mechanical ventilation treatment of children with severe asthmatoid disease / 中国医师进修杂志

ObjectiveTo determine optimal positive end expiratory pressure (PEEP) in mechanical ventilation in children with severe asthmatoid disease based on the quasistatic pressure-volume (P-V) curve.MethodsA serf-control study was done on 23 children with severe asthmatoid disease in the pediatric intensive care unit( PICU ).Quasistatic lung P-V curve of these patients was analyzed and the lower inflection point (LIP) from P-V curve was determined.Three different PEEP (0 cm H2O,LIP,LIP+2 cm H2O,1 mm H2O =0.098 kPa) were given to the patients.The effects of PEEP at different levels on gas exchange,hemodynamic and airway pressure were observed.ResultsThe quasistatic LIP were (2.70 ±2.00)cm H2O.When PEEP was increased to the level of LIP + 2 cm H2O,PaO2 / FiO2 and lung compliance improved significantly (P ＜ 0.01 ) and dynamic lung compliance was the highest,peak inspiratory pressure was (22.30 ± 3.00) cm H2O and mean airway pressure was( 14.11 ± 1.01 ) cm H2O,without obvious adverse effects on mean arterial blood pressure and heart rate.There was no difference in PaCO2,when compared PEEP =0 cmH2O to PEEP =LIP + 2 cmH2O.ConclusionThe application of PEEP is safe.LIP + 2 cm H2O from quasistatic P-V curve could be set as the optimal PEEP under which mechanical ventilation has the best efficacy and do not aggravate CO2 retention and abnormality of hemodynamics in children with severe asthmatoid disease.

Biomechanical Evaluation of the Capsular Stiffness and Clinical Features in Adhesive Capsulitis of Shoulders

OBJECTIVE: To evaluate the capsular stiffness of the glenohumeral joint by measuring the slope of pressure-volume curves generated during intra-articular hydraulic distension (IHD) and analyze its correlation with clinical variables and outcomes in terms of limitation of range of motion (LOM) and severity of pain. METHOD: IHD with real-time intra-articular pressure monitoring was performed for 53 patients with adhesive capsulitis and the capsular stiffness was measured from pressure-volume curves by calculating the slope of elastic deformation region. LOM, measured by LOM score and sum of ROMs (range of motion), and degree of pain, measured by visual analog scale (VAS), were evaluated before and after IHD: three days (3D) and one month (1M) after IHD. RESULTS: In patients with stiffer capsules, LOM and pain were severe before IHD (Pearson's correlation coefficient (r)= 0.291, -0.348, 0.381 and p=0.065, 0.026, 0.014 for LOM score, sum of ROMs and VAS, respectively. By this order, henceforth). On 3D follow up, the correlation between the stiffness and LOM or pain was maintained (r=0.291, -0.348, 0.381 and p=0.065, 0.026, 0.014). The improvement of LOM score on 3D follow up was less as the capsules were stiffer (r=-0.368, p=0.023). On 1M follow up, LOM remained severer in stiffer capsules whereas pain did not (r=0.372, -0.402, 0.183 and p=0.039, 0.025, 0.342). CONCLUSION: The stiffness of the glenohumeral joint capsule, measured from the slope of pressure-volume curves during IHD, showed significant correlation with the severity of LOM and pain in patients with adhesive capsulitis of shoulder.

Selection of ideal tidal volume according to pressure-volume curve for instruction of mechanical ventilation nursing / 中国实用护理杂志

Objective To study the influence of the different tidal volume on hemodynamics,pulmonary ventilation and pulmonary mechanics during mechanical ventilation in patients with acute lung injury.Methods To adopt contrast method,making use of the VIIP +0.196 kPa of P-V curve to decide PEEP,then according to the VUIP of P-V curve,obtaining the three different data of humidity 100%Vt,85% Vt and 70 Vt.At the same time,monitoring the change of static compliance,the changing of hemodynamics and P-V curve.Results 85%Vt group was better than 100%Vt group and 70%Vt group in the heart rates,CVP,PaO_2,the peak airway pressure(PIP) and mean pressure(Pm),Cst,PaO_2/FiO_2.Conclusions When insuring the PEEP data in low inflection point pressure (Pinf) of breathing system P-V curve,and 85% humidity in upper inflection point pressure,which is in accordance with individual protecting breathing strategy.The curative effect is the best for improving static compliance and decreasing the harm of lung injury.The change of pressure-volume curve should be paid attention to in nursing.

Two Methods of Setting Positive End-expiratory Pressure in Acute Lung Injury: An Experimental Computed Tomography Volumetric Study

This study was conducted to observe effects of two methods of setting positive endexpiratory pressure (PEEP) based on the pressure-volume (PV) curve. After lung injury was induced by oleic acid in six mongrel adult dogs, the inflation PV curve was traced and the lower inflection point (LIP) was measured. The 'PEEP(INF)' was defined as LIP+2 cmH2O. After recruitment maneuver to move the lung physiology to the deflation limb of PV curve, decremental PEEP was applied. The lowest level of PEEP that did not result in a significant drop in PaO2 was defined as the 'PEEP(DEF)'. Arterial blood gases, lung mechanics, hemodynamics, and lung volumes (measured on computed tomography during end-expiratory pause) were measured at PEEP of 0 cmH2O, PEEP(INF) and PEEP(DEF) sequentially. The median PEEP(INF) was 13.4 cm H2O (interquartile range, 12.5-14.3) and median PEEP(DEF) was 12.0 cm H2O (10.0-16.5) (p=0.813). PEEP(DEF) was associated with significantly higher PaO2 and lung volumes, and significantly lower shunt fraction and cardiac index when compared to PEEP(INF) (p<0.05). Setting the PEEP based on the deflation limb of the PV curve was useful in improving oxygenation and lung volumes in a canine lung injury model.

Comparisons of Physical and Biological Activities between Newfactan(R), Surfacten(R) and Exosurf(R)

PURPOSE: Neonatal respiratory distress syndrome (RDS) is caused by the deficiency of pulmonary surfactants in the newborn. We aim to determine and compare the physical and biological activities of the three surfactants currently on the market, namely Newfactan(R), Surfacten(R) and Exosurf(R). METHODS: For physical activities, we performed the stable microbubble test (SMR) and Pulsating Bubble Surfactometer (PBS). The minimum and maximum surface tensions measured at 1 and 5 minutes allowed us to create the surface-tension diagrams, from which the compressibility at a surface tension of 10 mN/m was calculated for all three products. The biological activities were compared using the pressure-volume curves measured from premature rabbit fetuses. RESULTS: For all three products, the concentration of surfactant and the number of stable microbubbles exhibited a proportional increase in relationship. For both Newfactan(R) and Surfacten(R), the minimal surface tensions were lower than 10 mN/m at 1 and 5 minutes. Hysteresis was evident at 1 and 5 minutes for both Newfactan(R) and Surfacten(R), and their surface tensions were reduced below 10 mN/m at 20% surface compression. As for Exosurf(R), all the hysteresis measurements were below expectations, and the reduction in surface tension during compression was also minimal. The compressibilities at a surface tension of 10 mN/m and measured at 1 and 5 minutes for Newfactan(R) and Surfacten(R), were less than 0.020 cm/dyne at almost concentrations. The pulmonary surface areas of the fetal rabbits were, after aeration by a maximum of 30 cmH2O, adequately maintained after decompression to 5 cmH2O in the groups treated with Newfactan(R) and Surfacten(R). However, the lung volume was not maintained upon decompression to 5 cmH2O in the groups treated with Exosurf(R). CONCLUSIONS: Newfactan(R) and Surfacten(R) were effective agents in prevention of pulmonary collapse in premature lungs.

Effect of Hypothermia on the Prevention of Ventilator-Induced Lung Injury in Rats / 결핵

BACKGROUND: Because ventilator-induced lung injury is partly dependent on the intensity of vascular flow, we hypothesized that hypothermia may attenuate the degree of such an injury through a reduced cardiac output. METHODS: Twenty-seven male Sprague-Dawley rats were randomly assigned to normothermia (37±1℃)-injurious ventilation (NT-V) group (n=10), hypothermia (27±1℃)-injurious ventilation (HT-V) group (n=10), or nonventilated control group (n=7). The two termal groups were subjected to injurious mechanical ventilation for 20 min with peak airway pressure 30cm H2O at zero positive end-expiratory pressure, which was translated to tidal volume 54±6ml in the NT-v group and 53±4ml in the HT-V group(p>0.05). RESULTS: Pressure-volume(P-V) curve after the injurious ventilation was almost identical to the baseline P-V curve in the HT-V group, whereas it was shifted rightward in the NT-V group. On gross inspection, the lungs of the HT-V group appeared smaller in size, and showed less hemorrhage especially at the dependent regions, than the lungs of the NT-V group. [Wet lung weight(g)/body weigh (kg)] (1.6±0.1 vs 2.4±1.2 ; p=0.014) and [wet lung weight/dry lung weight] (5.0±0.1 vs 6.1±0.8 ; p=0.046) of the HT-V group were both lower than those of the NT-V group, while not different from those of the control group(1.4±0.4, 4.8±0.4, respectivyly). Protein concentration of the BAL fluid of the HT-V group was lower than that of the NT-V group(1,374±726 ug/ml vs 3,471±1,985 ug/ml;p=0.003). Lactic dehydrogenase level of the BAL fluid of the HT-V group was lower than that of the NT-V group(0.18±0.10 unit/ml vs 0.43±0.22 unit/ml;p=0.046). CONCLUSIONS: Hypothermia attenuated pulmonary hemorrhage, permeability pulmonary edema, and alveolar cellular injuries associated with injurious mechanical ventilation, and preserved normal P-V characteristics of the lung in rats.

Influences of high intracranial pressure on the compliance of respiratory system in dog / 解放军医学杂志

Objective To investigate the effect of acute high intracranial pressure on the static pressure-volume curve of dogs' total respiratory system in order to evaluate the relationship between brain injury and respiratory insufficiency.Methods Fourteen dogs were divided into two groups.Animals were anesthetized,paralyzed and mechanical ventilated.The intracranial hypertension in experimental group(n=8)was induced by injecting blood-clots into the right frontal lobe.The other six dogs served as control.The intracranial pressure was monitored by an optical fiber transmitter inserted into the left cerebral hemisphere.The pressure-volume curves of the respiratory system were measured before and after induction of high intracranial pressure by a self-made apparatus consisting of two sealed bottles and a U shaped glass tube.The curves were also measured correspondingly in control group.The static compliance was calculated by equation C=?V/?P.The volume of intracerebral hematoma was calculated.The histopathology of lung was studied under microscope.Results The intracerebral hematoma was located in the right frontal lobe with volume from 4.8-11.5ml(average 8.48ml).The intracranial pressure was elevated from 18.13?5.96mmHg to 46.88?16.42mmHg,which induced a shift of pressure-volume curve to the right in experimental group,while no obvious change was found in control group.Compared to pre-injection,the static compliance of total respiratory system decreased significantly(P