Application of electrical impedance tomography for postoperative lung recruitment in patients undergoing off pump coronary artery bypass grafting surgery / 上海交通大学学报（医学版）

Objective·To find out the optimal positive end expiratory pressure (PEEP) by electrical impedance tomography (EIT) for better lung recruitment and ventilation distribution in patients undergoing off pump coronary artery bypass grafting surgery (OPCAB). Methods?·?105 patients underwent OPCAB from Jan. 2017 to Dec. 2017 were analysed. Patients were randomly divided into two groups, i.e. experiment group (54 cases) and control group (51 cases). Four regions of interest (ROI) were recorded by EIT. PEEP were 3?cmH2O in control group while PEEP were increased stepwise by 2?cmH2O from 0?cmH2O to 14?cmH2O in experiment group. The optimal PEEP for lung recruitment was applied in experiment group. Postoperative oxygenation index (PaO2/FiO2) and pulmonary complication were compared between two groups. Results?·?The overall mortality was 2 (1.90%). The incidence of postoperative pulmonary complication, pulmonary infection, atelectasis, pleural effusion were 18.10%, 2.86%, 18.10%, 18.10%, respectively. The optimal PEEP zone was 6-9?cmH2O. PaO2/FiO2was significantly increased with the optimal PEEP in experiment group (P=0.00). There were significant differences in postoperative pulmonary complication between two groups (P=0.02). Conclusion?·?EIT can directly monitor ventilation distribution and titrate suitable PEEP for better lung recruitment in patients undergoing OPCAB. It can significantly reduce postoperative pulmonary complication, improve oxygenation, and decrease ICU stay and ventilation duration.

Application of electrical impedance tomography for postoperative lung recruitment in patients undergoing off pump coronary artery bypass grafting surgery / 上海交通大学学报（医学版）

Objective • To find out the optimal positive end expiratory pressure (PEEP) by electrical impedance tomography (EIT) for better lung recruitment and ventilation distribution in patients undergoing off pump coronary artery bypass grafting surgery (OPCAB). Methods • 105 patients underwent OPCAB from Jan. 2017 to Dec. 2017 were analysed. Patients were randomly divided into two groups, i.e. experiment group (54 cases) and control group (51 cases). Four regions of interest (ROI) were recorded by EIT. PEEP were 3 cmH2O in control group while PEEP were increased stepwise by 2 cmH2O from 0 cmH2O to 14 cmH2O in experiment group. The optimal PEEP for lung recruitment was applied in experiment group. Postoperative oxygenation index (PaO2/FiO2) and pulmonary complication were compared between two groups. Results • The overall mortality was 2 (1.90%). The incidence of postoperative pulmonary complication, pulmonary infection, atelectasis, pleural effusion were 18.10%, 2.86%, 18.10%, 18.10%, respectively. The optimal PEEP zone was 6-9 cmH2O. PaO2/FiO2 was significantly increased with the optimal PEEP in experiment group (P=0.00). There were significant differences in postoperative pulmonary complication between two groups (P=0.02). Conclusion • EIT can directly monitor ventilation distribution and titrate suitable PEEP for better lung recruitment in patients undergoing OPCAB. It can significantly reduce postoperative pulmonary complication, improve oxygenation, and decrease ICU stay and ventilation duration.

Effects of PEEP on the thermoregulatory responses during TIVA in patients undergoing tympanoplasty / 대한마취과학회지

BACKGROUND: During general anesthesia, core temperature decreases, largely due to heat loss caused by peripheral vasodilation, resulting in heat redistribution to peripheral tissues. Multiple factors contribute to body temperature regulation during general anesthesia. It was reported that baroreceptor unloading by positive end-expiratory pressure (PEEP) attenuates anesthetically-induced hypothermia. So, we evaluated the effects of PEEP on thermoregulatory responses during total intravenous anesthesia (TIVA). METHODS: Forty healthy patients scheduled for tympanoplasty were allocated two groups, Group ZEEP (zero end-expiratory pressure, n = 20) and Group PEEP (PEEP application of 5 cmH2O, n = 20). Ambient temperature was maintained at 22-24degrees C, and anesthesia was induced and maintained with propofol-remifentanil. The core temperature and the temperature difference between forearm and fingertip skin were monitored before and after the induction of general anesthesia having a duration of 180 minutes. RESULTS: The core temperature gradient (Ti-Tf) was higher in patients with ZEEP than with PEEP. The core temperature was maintained at a higher level in patients with PEEP. Additionally, the vasoconstriction threshold was higher in patients with PEEP. CONCLUSIONS: It seems that PEEP attenuates anesthetically-induced hypothermia during TIVA.

Clinical application of invasive ventilation in treatment of acute pulmonary edema and prognosis analysis / 中华急诊医学杂志

Objective To observe the efficacy of invasive ventilation (Ⅳ) in treatment of acute pulmonary edema (APE), and to explore the factors associated with prognosis. Method From March 2005 to December 2007, 23 APE patients, who were hospitalized in the EICU of People' s Hospital of Peking University and the con-ventional treatment and noninvasive ventilation were not effective, were treated by Ⅳ (PEEP 5～18 cmH2O). Blood pressure, heart rate, respiratory rate, and arterial blood gas values were recorded accurately before and after ventilation and compared with each other. Regression analysis was used to analyze the factors associated with prog-nosis. Resets Three hours after Ⅳ, the blood pressure, heart rate, respiratory rate, arterial blood gas were sig-nificanfly improved (P <0.01). Among the 23 patients, 11 survived, and the other 12 patients died. Nine pa-tients died of MOF. Among 16 patients with cardiac function Ⅲ-Ⅳ, 10 died. Among 15 patients with acute my-ocardial infarction, 9 died. Among 11 patients with renal insufficiency, 9 died. The multivariate logistic regression analysis showed that the reduced left ventricular ejection fraction, the lower mean arterial pressure, and the in-creased creatinine were the independent predictor of prognosis. Conclusions Invasive ventilation is an effective method of treating patients with acute pulmonary edema. Proper ventilation may improve the cardiac function and clinical symptoms, but it's not the fundamental measure for increasing cure rate. 1he renal insufficiency and heart failure are the independent predictor of prognosis.

The Arterial Oxygenation Effects According to Different Ventilatory Modes during One Lung Ventilation / 대한마취과학회지

Among patients scheduled for elective surgery at the Kyung Hee University Hospital, 15 patients undergoing open thoracotomy were selected. Two different ventilatory modes were employed and compared to the one-lung ventilation(control). First, 10 cmH2O of continuous positive airway pressure was applied to the unventilated lung while patients were under one lung ventilation with 50% oxygen(CPAP 10 cmH2O). Second, 10 cmH2O of positive end expiratory pressure to the ventilated lung and 10 cmH2O of continuous positive airway pressure to the unventilated lung were applied while patients were under one lung ventilation with 50% oxygen(CPAP/PEEP). Arterial oxygen tension, alveolar-arterial oxygen difference (A-aDO2) and intrapulmonary shunt fraction of two different ventilatory modes were observed and compared to control group, and CPAP/PEEP group to CPAP 10 cmHO group. The RESULTs were as followed: 1) Mean PaO2 in CPAP 10 cmH2O and CPAP/PEEP were 138+/-42 mmHg and 177+/-44 mmHg, respectively, and were significantly increased as compared to 100+/-29 mmHg of control group(P<0.05). Comparing the PaO2 of CPAP 10 cmH2O and CPAP/PEEP, there was statistically significant increase in CPAP/PEEP(P<0.05). 2) A-aDO2 in CPAP 10 cmH2O and CPAP/PEEP were 175+/-43 mmHg and 131+42 mmHg, respectively, and were significantly decreased as compared to 213+/-32 mmHg of control group(P<0.05). Shunt percentages(Qsp/QT) were measured as 23.7+/-5.8% in control group, 18.3+/-6.0% in CPAP 10 cmH2O, 13.0+/-4.3% in CPAP/PEEP. Shunt percentages of CPAP 10 cmH2O and CPAP/PEEP were decreased significantly as compared to the control group(P<0.05). Comparing the A-a DO2 and the shunt percentages of CPAP 10 cmH2O and CPAP/PEEP, there was statistically significant decrease in CPAP/PEEP(P<0.05). Based on the above RESULTs, the application of appropriate continuous positive airway pressure to the unventilated lung and 10 cmH2O of positive end expiratory pressure to the ventilated lung during one lung ventilation is thought to be more effective than only continuous positive airway pressure to the unventilated lung in preventing hypoxemia.

Effect of Positive End-expiratory Pressure(PEEP) of Contra-lateral Lung on Redistribution of Pulmonary Blood Flow during One-lung Atelectasis / 대한마취과학회지

The normal response of the pulmonary vasculature to one-lung atelectasis is an increase in pulmonary vascular resistance (PVR). The mechanism of the increase in PVR is thought to be due almost entirely to hypoxic pulmonary vasoconstriction (HPV). Regional HPV results in blood flow diversion from hypoxic regions to normoxic regions. The expected pulmonary shunt is thereby reduced and the arterial oxygen tension increased. PEEP improves the arterial oxygen tension as a result of increasing functional residual capacity (FRC) and decreasing intrapulmonary shunt. The aims of the present studies were to observe blood flow diversion from atelectatic lung to normoxic lung and to prove a sustained redistribution of pulmonary blood flow from ventilated with PEEP to atelectatic regions. This study evaluated the interactions between HPV and PEEP. Eight mongrel dogs were anesthetized with pentobarbital. Left pulmonary blood flow was measured with eletromagnetic flow probes following left lateral thoracotomy. Pulmonary arterial pressures, PCWP, systemic arterial pressures were measured via indwelling catheter. Cardiac output was determined by thermodilution in triplicate. The right lung was ventilated continuosly with 100% O2, while left lung was ventilated with 100 O2 (control phase), and unventilated for 60 min. of atelectasis. PEEP of 5 and 10 cmH2O was ed to the right lung. During two-lung ventilation with 100 oxygen, cardiac output was 2890+/-880 ml/min. (mean SD) and left pulmonary blqod flow was 1100+/-220 ml/min. Left lung atelectasis resulted in a reduction of the percent left blood flow compared with cardiac output from 41+/-10% to 29+/-7% at 15 min and to 22+/-9% at 60 min (p<0.05). The ratio of left pulmonary blood flow to mean pulmonary artery pressure decreased from 51+/-25 ml/min/ mmHg in control to 19+/-7 ml/min/mmHg at 60 min (p<0.05). Left pulmonary vascular resistance increased gradually (p<0.01). Arterial oxgen tension was the lowest at 15 min (165+/-66 mmHg) and increased subsequently (p<0.01). Intrapulmonary shunt was 27+/-6% in, control phase and abruptly increased to 37+/-6% at 15 min after atelectasis and decreased to 34+/-10% at 60 min. When 10 cmH2O PEEP was applied to the right hung during left lung atelectasis, the percent ratio of left pulmonary blood flow to cardiac output was significantly increased from 22+/-9% at 60 min of left lung atelectasis to 34+/-8% (p<0.05). Left pulmonary vascular resistance significantly decreased as compared with 45 and 60,min of left lung atelectasis (p<0.05). Arterial oxygen tension incresed by PEEP of 5 and 10 cmH to 257+/-74 mmHg and 252+/-92 mmHg compared with 164+/-65 mmHg and 177+/-28 mmHg at 15 and 30 min. of left lung atelectasis (p<0.05). The present study demonstrated that the response to acute atelectasis is a regional increase in pulmonary vascular resistance and a sustained diversion of blood flow away from the atelectatic lung. In this study, the application of 10 cmH2O PEEP resulted in a redistribution of pulmonary blood flow from normoxic lung to atelectatic lung and didn't affect arterial oxygenation. We conclude that when employing the technique of one-lung anesthesia, PEEP to improve oxygenstion should be cautiously applied and a search for the maximum oxygenation and a minimum redistribution might be started, in an attempt to find the optimal PEEP.

A Study on the Best Positive End - expiratory Pressure of Dogs in Acute Respiratory Failure Induced by Oleic Acid / 대한마취과학회지

Controlled mechanical ventilation with positive end-expiratory pressure(PEEP) is a widely accepted method for the treatment of acute respiratory failure. But artificial ventilation with large tidal voume, high airway pressure and an inspired oxygen concentration of l00% are necessary for adequate arterial oxygenation in severe acute pulmonary parenchymal failure. It has been suspected that such therapy may cause irreversible pulmonary damage. The extracorporeal respiratory support has been called extracorporeal membrane oxygenation (ECMO), extracorporeal CO, removal(ECCO2R) or extracorporeal lung assist(ECLA). They are prolonged venoarterial(VA) or venovenous(VV) bypass for the refractory hypoxemia which provides the diseased lung with rest. The respiratory rate can be lowered down to about 4~8 rates/min during ECLA. PEEP is known to improve the ventilation perfusion distribution with alveolar recruitment. Low frequency positive pressure ventilation is accompanied by PEEP to keep alveoli open during ECLA. The level of PEEP must be determined adequately because high PEEP may decrease the cardiac output especially during VV ECLA. The experimental model for acute respiratory failure was induced by the intravenous injection of oleic acid 0.07ml/kg on six mongrel dogs(15.8+/-0.7kg). After values of arterial oxygen saturation(SaO2) and end-tidal CO2(E(T)CO2) were stabilized on the monitor, we measured control values of hemodynamic parameters. The stepwise increase of PEEP from 5 cmH2O to 15 cmH2O via 10 cmH2O was followed by the comparison of the respective hemodynamic values at each PEEP with control. Compared with control, PEEP of 5 cmH2O did not cause any changes and PEEP of 15 cmH, decreased cardiac output. At PEEP of 10 cmHO, the cardiac output and oxygen flux was maintained with normoxia. It was concluded that PEEP of 10 cmHO can be applied to clinical VV ECLA.