Objective To investigate the predictive value of continuous dynamic monitoring of intrapulmonary shunt (Qs/Qt) in patients with acute respiratory distress syndrome (ARDS).Methods A prospective observational study was conducted.The adult patients with ARDS undergoing mechanical ventilation admitted to intensive care unit (ICU) of Tianjin Third Central Hospital from June 2014 to December 2015 were enrolled.Baseline characteristics,demographic data and relevant physiologic data were recorded.All patients were divided into survivors and non-survivors according to the outcome of patients within 28 days.Artery and mixed venous blood was collected immediately after admission for blood gas analysis,and daily Qs/Qt within 7 days was continuously monitored in ARDS patients.The receiver operating characteristic curve (ROC) was used to evaluate the prognosis accuracy of Qs/Qt.Results In 46 enrolled ARDS patients,20 died,and 26 survived.During the first 7 days of ARDS,the mean Qs/Qt in survivors showed an increasing tendency [(23 ± 6)％,(27 ± 6)％,(28 ± 9)％,respectively,at 1-3 days] and a downtrend tendency from 4 days [(27 ± 5)％,(25 ± 4)％,(19 ± 4)％,(16 ± 2)％,respectively,at 4-7 days].However,a rising tendency of Qs/Qt in non-survivors was found at 1-7 days [(28 ± 7)％,(30 ± 3)％,(33 ± 6)％,(33 ± 11)％,(34 ± 5)％,(33 ± 6)％,(35 ± 6)％,respectively],and Qs/Qt from the 5th day in non-survivors was significantly higher than that in survivors (all P ＜ 0.05).The fluctuation of oxygenation index (PaO2/FiO2) within 1 week in both groups was small,and PaO2/FiO2 (mmHg,1 mmHg =0.133 kPa) at 1-7 days in survivors was 167.37±43.98,180.55±39.90,174.27±35.47,188.64±39.74,252.54±49.22,239.35±25.63,248.93±45.64,respectively,and it was 168.65±35.54,182.31 ± 32.36,159.80 ± 34.39,176.97 ± 31.75,200.69 ± 45.33,185.98 ± 36.47,and 175.43 ± 30.98 in non-survivors respectively.PaO2/FiO2 was significantly lower in non-survivors than survivors from 5 days (all P ＜ 0.05).It was shown by ROC curve that area under ROC curve (AUC) for Qs/Qt evaluating the prognosis on the 5th day was 0.958,and 95％ confidence interval (95％CI) was 0.777-0.999 (P ＜ 0.000 1,Z =13.13).When the cut-off value of Qs/Qt was 28％,sensitivity and specificity were 83.3％ and 90.0％,respectively.AUC for PaO2/FiO2 evaluating the prognosis on the 5th day was 0.790,and 95％CI was 0.577-0.928 (P =0.002 1,Z =3.08).When the cut-off value of PaO2/FiO2 was 223 mmHg,sensitivity and specificity were 69.2％ and 81.8％,respectively.Conclusion Dynamic Qs/Qt surveillance can help physician to analyze the changes of the patient's condition,and it was better than PaO2/FiO2,and can be an important evaluation indicator of prognosis for ARDS patients.

BACKGROUND:The incidence of medial collateral ligament injuries in the knee joint is easy to lead to secondary meniscus and cartilage damage,and long-term chronic damage can lead to the occurrence of osteoarthritis.At present,there are few studies on the mechanics of meniscus and articular cartilage injury caused by medial collateral ligament rupture. OBJECTIVE:To investigate the effect of different degrees of medial collateral ligament injury on the biomechanics of meniscus and cartilage of knee joint. METHODS:The CT and MRI examinations of the knee joint of a healthy volunteer were performed to obtain the image data.The scanning data were imported into Mimics,Geomagic,and Solidworks software in turn.After registration and fusion,a 3D model of normal knee joint was established.On this basis,models of medial collateral ligament injury in different degrees of knee joint were simulated,which were divided into four groups,including:(1)medial collateral ligament was intact;(2)deep medial collateral ligament fracture;(3)superficial medial collateral ligament fracture;(4)complete rupture of medial collateral ligament.Finally,Ansys software was introduced to apply three modes of loads to the knee joint:(1)10 N·m valvaration torque was applied to the top of the femur.(2)A 4 N·m internal torque was applied to the top of the femur.(3)A 4 N·m external torque was applied to the top of the femur.The effects of four groups of models on knee biomechanics under different loads were analyzed. RESULTS AND CONCLUSION:(1)In the extension position of the knee joint,when a 10 N·m valgus torque was applied to the knee joint,the overall stress of the posterolateral meniscus increased with different degrees of medial collateral ligament injuries,while the stress of the articular cartilage did not change significantly.The peak stress of the posterolateral meniscus increased significantly with superficial medial collateral ligament rupture.(2)In the knee extension position,when a 4 N·m internal rotation torque was applied to the knee joint,the overall stress of the medial and lateral meniscus increased after different degrees of medial collateral ligament injury.When superficial medial collateral ligament rupture occurred,the peak stress of the meniscus shifted from the anterior horn of the medial meniscus to the anterior horn of the lateral meniscus.(3)In the knee extension position,applying a 4 N·m external rotation torque to the knee joint,the peak stress of the posterolateral meniscus increased more significantly than that of the medial meniscus,and the stress of the articular cartilage changed less.(4)These results show that the risk of meniscus injury secondary to superficial medial collateral ligament rupture is much higher than that of deep medial collateral ligament rupture when the knee is in extension,and the lateral meniscus is more vulnerable to injury than the medial meniscus.Both superficial medial collateral ligament and deep medial collateral ligament play an important role in the rotational stability of the knee joint.