Driving pressure in mechanical ventilation:A review

Driving pressure(ΔP)is a core therapeutic component of mechanical ventilation(MV).Varying levels ofΔP have been employed during MV depending on the type of underlying pathology and severity of injury.However,ΔP levels have also been shown to closely impact hard endpoints such as mortality.Considering this,conducting an in-depth review ofΔP as a unique,outcome-impacting therapeutic modality is extremely important.There is a need to understand the subtleties involved in making sureΔP levels are optimized to enhance outcomes and minimize harm.We performed this narrative review to further explore the various uses ofΔP,the different parameters that can affect its use,and how outcomes vary in different patient populations at different pressure levels.To better utilizeΔP in MV-requiring patients,additional large-scale clinical studies are needed.

Effects of acetylcysteine on micro-inflammation and pulmonary ventilation in chronic obstructive pulmonary disease exacerbation

BACKGROUND Acute exacerbation of chronic obstructive pulmonary disease(AECOPD)is a serious complication of chronic obstructive pulmonary disease,often characterized by increased morbidity and mortality.In traditional Chinese medicine,AECOPD is linked to phlegm-heat and blood-stasis,presenting symptoms like thick sputum,fever,and chest pain.It has been shown that acetylcysteine inhalation in conjunction with conventional therapy significantly reduced inflammatory markers and improved lung function parameters in patients with AECOPD,suggesting that acetylcysteine may be an important adjunctive therapy for patients with phlegm-heat-blood stasis type AECOPD.AIM To investigate the effect of acetylcysteine on microinflammation and lung ventilation in patients with phlegm-heat and blood-stasis-type AECOPD.METHODS One hundred patients with phlegm-heat and blood-stasis-type AECOPD were randomly assigned to two groups.The treatment group received acetylcysteine inhalation(10%solution,5 mL,twice daily)along with conventional therapy,whereas the control group received only conventional therapy.The treatment duration was 14 d.Inflammatory markers(C-reactive protein,interleukin-6,and tumor necrosis factor-alpha)in the serum and sputum as well as lung function parameters(forced expiratory volume in one second,forced vital capacity,and peak expiratory flow)were assessed pre-and post-treatment.Acetylcysteine inhalation led to significant reductions in inflammatory markers and improvements in lung function parameters compared to those in the control group(P<0.05).This suggests that acetylcysteine could serve as an effective adjunct therapy for patients with phlegm-heat and blood-stasis-type AECOPD.RESULTS Acetylcysteine inhalation significantly reduced inflammatory markers in the serum and sputum and improved lung ventilation function parameters in patients with phlegm-heat and blood-stasis type AECOPD compared with the control group.These differences were statistically significant(P<0.05).The study concluded that acetylcysteine inhalation had a positive effect on microinflammation and lung ventilation function in patients with this type of AECOPD,suggesting its potential as an adjuvant therapy for such cases.CONCLUSION Acetylcysteine inhalation demonstrated significant improvements in reducing inflammatory markers in the serum and sputum,as well as enhancing lung ventilation function parameters in patients with phlegm-heat and bloodstasis type AECOPD.These findings suggest that acetylcysteine could serve as a valuable adjuvant therapy for individuals with this specific type of AECOPD,offering benefits for managing microinflammation and optimizing lung function.

Lung Ventilation Functional Monitoring Based on Electrical Impedance Tomography

Medically, electrical impedance tomography （EIT） is a relatively inexpensive, safe, non-invasive and portable technique compared with computerized tomography （CT） and magnetic resonance imaging （MRI）. In this paper, EIT_TJU_ II system is developed including both the data collection system and image reconstruction algo- rithm. The testing approach of the system performance, including spatial resolution and sensitivity, is described through brine tank experiments. The images of the thorax physical model verify that the system can reconstruct the interior resistivity distribution. Finally, the lung ventilation functional monitoring in vivo is realized by EIT, and the visualized images indicate that the configuration and performance of EIT_TJU_ II system are feasible and EIT is a promising technique in clinical monitoring application.

Effect of Nalmefene on Delayed Neurocognitive Recovery in Elderly Patients Undergoing Video-assisted Thoracic Surgery with One Lung Ventilation

The intravenous use of nalmefene has been found to exert neuroprotective effect in patients with severe traumatic brain injury and acute cerebral infarction;nonetheless,it is unknown whether nalmefene alleviates delayed neurocognitive recovery.Our purpose of the current research was to clarify the impact of nalmefene on delayed neurocognitive recovery in aged patients experiencing video-assisted thoracic surgery(VATS)with intraoperative use of one lung ventilation(OLV).The present study involved 120 paticents undergoing selective VATS,randomized to accept low-dose nalmefene(N1 group,n=40),high-dose nalmefene(N2 group,1n=40)or equal volume of physiologic saline(control group,1=40).A battery of neuropsychological tests were used to estimate cognitive function I day before surgery(o)and 10 days after surgery or before discharge(t).Regional cerebral oxygen saturation(rSO2)was detected 5 min before induction(t),5 min after induction(1),15 and 60 min after onset of OLV(62 and 13),and 15 min after termination of OLV(4).The plasma values of interleukin(IL)-1β,IL-6,tumor necrosis factor(TNF)-a1 and adiponectin(ADP)were also detected prior to induction of anesthesia(T0),1 h,2 h and 6 h after surgery(TI,T2,T3).On 1,delayed neurocognitive recovery occurred in 5/40(12.5%)patients of NI group,in 5/40(12.5%)patients of N2 group and in 13/40(32.5%)patients of control group(P<0.05).There were no statistical differences in rSO2 among three groups at different time points.At Tl,T2 and T3,IL-1β,IL-6 and TNF-a values significantly increased and ADP value significantly decreased(P<0.05)in control group.In contrast,at TI,T2 and T3,IL-1β,IL-6 and TNF-a values decreased and ADP value decreased less in N1 and N2 groups(P<0.05).At TI,T2 and T3,IL-1β,IL-6 and TNF-a concentrations presented a trend of N2 group<N1 group<control group and ADP presented a trend of N2 group>Nl group>control group(P<0.05).The result of our present research supports the hypothesis that the perioperative intravenous treatment with nalmefene to VATS with OLV ameliorates postoperative cognitive function and decreases the incidence of delayed neurocognitive recovery,most likely by suppression of inflammatory responses.

Oxygenation,inflammatory response and lung injury during one lung ventilation in rabbits using inspired oxygen fraction of 0.6 vs.1.0

Maintaining adequate oxygenation during one-lung ventilation（OLV） requires high inspired oxygen fraction（FiO_2）.However,high FiO_2 also causes inflammatory response and lung injury.Therefore,it remains a great interest to clinicians and scientists to optimize the care of patients undergoing OLV.The aim of this study was to determine and compare oxygenation,inflammatory response and lung injury during OLV in rabbits using FiO_2 of 0.6 vs.1.0.After 30 minutes of two-lung ventilation（TLV） as baseline,30 rabbits were randomly assigned to three groups receiving mechanical ventilation for 3 hours：the sham group,receiving TLV with 0.6 FiO_2;the 1.0 FiO_2 group,receiving OLV with 1.0 FiO_2;the 0.6 FiO_2 group,receiving OLV with 0.6 FiO_2.Pulse oximetry was continuously monitored and arterial blood gas analysis was intermittently conducted.Histopathologic study of lung tissues was performed and inflammatory cytokines and the mRNA and protein of nuclear factor kappa B（NF-κB） p65 were determined.Three of the 10 rabbits in the 0.6 FiO_2 group suffered hypoxemia,defined by pulse oximetric saturation（SpO_2） less than 90%.Partial pressure of oxygen（PaO_2）,acute lung injury（ALI） score,myeloperoxidase（MPO）,tumor necrosis factor-a（TNF-α）,interleukin-6（IL-6）,mRNA and protein of NF-kB p65 were lower in the 0.6 FiO_2group than in the 1.0 FiO_2 group.In conclusion,during OLV,if FiO_2 of 0.6 can be tolerated,lung injury associated with high FiO_2 can be minimized.Further study is needed to validate this finding in human subjects.

Analysis and Comparison of the Effect of Preserving Spontaneous Breathing Without Intubation and Endotracheal Intubation with One Lung Ventilation in Single-hole Thoracoscopic Bulla Suture

Objective:To explore the situation of patients and the compare the effect between two methods,which are preserving spontaneous breathing without intubation and endotracheal intubation with one lung ventilation in the single-hole thoracoscopic bulla suture.Method:42 patients who received single-hole thoracoscopic pulmonary bullae suture in our hospital from January 2020 to December 2021 were selected as the study subjects,including 19 patients who underwent endotracheal intubation and one lung ventilation as the control group and 23 patients who underwent single-hole thoracoscopic pulmonary bullae suture without intubation as the study group.The relevant indexes,postoperative general conditions,complications and pneumothorax recurrence of the two groups were analyzed and observed.Results:In the control group,the scores of anesthesia time(points),resuscitation time(points),surgical visual field score(points),surgical time(points),and surgical bleeding volume(points)were 20.8±4.6,19.9±7.9,1.7±0.5,44.9±7.9,and 11.4±2.4 respectively.In the study group,the scores of anesthesia time(points),resuscitation time(points),surgical visual field score(points),surgical time(points),and scores of surgical bleeding(points)were 17.9±4.3,15.4±3.4,1.9±0.4,48.4±7.1,10.9±2.2,respectively.There was no statistical difference in surgical visual field score,surgical time and surgical bleeding whereas there was a statistical difference between anesthesia time and resuscitation time.In the control group after operation,VAS score at 6 hours after operation,SaO_(2)(%)after operation,PaCO_(2)(mmHg)after operation,drainage volume(ML)after operation,feeding time(H)after operation,retention time of thoracic tube after operation(H),WBC(109)on the first day after operation,hospitalization time(d),and total hospitalization cost(RMB 1000)were 2.1±0.7,98.2±1.4,42.4±4.9,139.1±23.1,6.9±1.6,37.1±5.4,7.9±2.1,6.6±1.3,and 2.6±0.3 respectively.As for the study group,the VAS score at 6 hours after operation,SaO_(2)(%)after operation,PaCO_(2)(mmHg)after operation,drainage volume(ML)after operation,feeding time(H)after operation,retention time of thoracic tube after operation(H),WBC(109)on the first day after operation,hospitalization time(d),and total hospitalization cost(RMB 1000)were 1.9±0.4,97.9±1.2,42.8±5.1,151.8±21.9,4.3±1.4,15.3±2.6,5.2±2.3,4.2±1.2,and 1.8±0.4 respectively.Among them,there were no significant differences in visual analog scale(VAS)score at 6 hours after operation,SaO_(2) after operation and PaCO_(2) after operation between the two groups,but there were significant differences in other factors.The complication rate of the control group was 36.84%,which was significantly higher than that of the study group(4.35%),with statistical difference.The recurrence rate of the control group was 21.05%,which was not significantly different from that of the study group(4.35%).Conclusion:The single-hole thoracoscopic bullae suture without intubation can reduce the anesthesia time and resuscitation time of patients,reduce the hospitalization cost of patients,reduce the treatment burden,shorten the first feeding time,and reduce the complication rate of patients.Therefore,it is worthy of clinical promotion.

Lung recruitment maneuver effects on respiratory mechanics and extravascular lung water index in patients with acute respiratory distress syndrome

BACKGROUND：Animal experiments showed that recruitment maneuver （RM） and protective ventilation strategy of the lung could improve oxygenation and reduce extravascular lung water. This study was to investigate the effects of RM on respiratory mechanics and extravascular lung water index （EVLWI） in patients with acute respiratory distress syndrome （ARDS）. METHODS：Thirty patients with ARDS were randomized into a RM group and a non-RM group. In the RM group, after basic mechanical ventilation stabilized for 30 minutes, RM was performed and repeated once every 12 hours for 3 days. In the non-RM group, lung protective strategy was conducted without RM. Oxygenation index （PaO2/FiO2）, peak inspiratory pressure （PIP）, Plateau pressure （Pplat）, static pulmonary compliance （Cst） and EVLWI of patients before treatment and at 12, 24, 48, 72 hours after the treatment were measured and compared between the groups. Hemodynamic changes were observed before and after RM. One-way ANOVA, Student＇s t test and Fisher＇s exact test were used to process the data. RESULTS：The levels of PaO2/FiO2 and Cst increased after treatment in the two groups, but they were higher in the RM group than in the non-RM group （P〈0.05）. The PIP and Pplat decreased after treatment in the two groups, but they were lower in the RM group than in the non-RM group （P〈0.05）. The EVLWI in the two groups showed downward trend after treatment （P〈0.05）, and the differences were signifcant at all time points （P〈0.01）; the EVLWI in the RM group was lower than that in the non-RM group at 12, 24, 48 and 72 hours （P〈0.05 or P〈0.01）. Compared with pre-RM, hemodynamics changes during RM were significantly different （P〈0.01）; compared with pre-RM, the changes were not significantly different at 120 seconds after the end of RM （P〉0.05）. CONCLUSIONS： RM could reduce EVLWI, increase oxygenation and lung compliance. The effect of RM on hemodynamics was transient.

A New Lung Mechanics Model and Its Evaluation with Clinical Data

Acute Respiratory Distress Syndrome (ARDS) is a major cause of morbidity and has a high rate of mortality. ARDS patients in the intensive care unit (ICU) require mechan-ical ventilation (MV) for breathing support, but inappropriate settings of MV can lead to ventilator induced lung injury (VILI). Those complications may be avoided by carefully optimizing ventilation parameters through model-based approaches. In this study we introduced a new model of lung mechanics (mNARX) which is a variation of the NARX model by Langdon et al. A multivariate process was undertaken to deter-mine the optimal parameters of the mNARX model and hence, the final structure of the model fit 25 patient data sets and successfully described all parts of the breathing cycle. The model was highly successful in predicting missing data and showed minimal error. Thus, this model can be used by the clinicians to find the optimal patient specific ventilator settings.

COMPARISON OF HIGH-FREQUENCY OSCILLATION VEN-TILATION WITH CONVENTIONAL MANDATORY VENTILATION IN ANIMAL ARDS MODEL

To compare effect of high-frequency oscillation ventilation （HFOV） and conventional mandatory ventilation （CMV） on lung injury development in rabbit with acute respiratory distress syndrome （ ARDS）. Methods Animals that underwent saline lung lavage to produce lung injury were randomized to one of the two treatment groups （ HFOV or CMV, n =6）. PaCO2 was maintained between 35 -45mmHg and arterial oxygen saturation （ SaO2 ） was maintain 〉 88% by adjusting corresponding ventilator parameters. Ventilation period was 6h. Lung fluids were aspirated before and at the end of ventilation for cell analysis. Then the animals were euthanized, lung tissue was removed for wet/dry weight measurement, light and electron microscopic examination. Besults The difference of artery blood gas analyses（pH, PaO2, PaCO2 ） between HFOV and CMV was insignificant. The difference between HFOV and CMV in cytological examination of lung fluids, wet/dry weight measurement was also insignificant. But compared with CMV, HFOV not only reduced the area of lung injury, but also reduced lung injury score in light and electron microscopic examination. Conclusion When same artery blood gas analysis was obtained, HFOV significantly reduced lung injury development in ARDS animal than CMV. As a lung protection strategy, HFOV can be used in the treatment of ARDS.

Experimental study of acute lung injury induced by different tidal volume ventilation in rats

Mechanical ventilation (MV) is a dual blade sward which if misused could lead to lung injury, called ventilator induced lung injury (VILI). Pathogenesis of VILI is very complex with various manifestations, which is the focus in MV field in recent years. 1 In our research, the rats were ventilated with different tidal volume, then the pathological changes of the lungs were observed under macroscopy, light and electronic microscope, and various laboratory tests in blood and bronchoalveolar lavage fluid (BALF) were also carried out in order to probe further the pathologic characteristics and the pathogenesis of VILI.

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.

特殊患者的肺保护性通气策略

机械通气可导致呼吸机相关性肺损伤(ventilator-associated lung injury, VALI),主要包括容积伤、气压伤、不张伤、生物伤和剪切伤。肺保护性通气策略(lung protective ventilation strategy, LPVS)是近几年来针对VALI而发展起来的机械通气新策略,其目的为尽可能的保护肺组织减少机械通气性损害。LPVS主要包括小潮气量、最佳的呼气末正压、肺复张等;LPVS的实施可以改善肺顺应性和肺泡处的气体交换,减少肺水肿和感染的发生,降低术后肺部并发症(postoperative pulmonary complications, PPCs)的发生率。本文拟讨论对于某些特殊患者应用肺保护性通气策略方面的进展。

The anesthesia analysis of the conversion video-assisted thoracic surgery to thoracotomy in pulmonary carcinoma

Objective： The aim of this study was to anesthesia analyse the factors of conversing video-assisted thoracic surgery to thoracectomy in pulmonary carcinoma. Methods： Double-lumen tube bronchial catheter intubation and interstitial positive pressure ventilation （IPPV） were used in all patients with video-assisted thoracic surgery after fast-speed venous induced anesthesia. IPPV, positive expiratory pressure （PEEP） and continuous positive airway pressure （CPAP） in collapse lobes of lung were used in one lung ventilation, and ventilation parameters were adjusted. Results： Two hundred and fifity- two patients double-lumen bronchial tube intubation used by fiberscope was located very well. The level of oxygen saturation of blood （Sp02）, end.tidal carbon dioxide pressure （PETCO2） could be maintained normal. 5 cases were forced to converse video-assisted thoracic surgery to thoracotomy because of 2 cases pulmonary adhesion, 2 cases severe pulmonary dysfunction and 1 case abnormal anatomy respectively. Conclusion： Long one lung ventilation such as pulmonary adhesion, severe pulmonary dysfunction and abnormal anatomy should be considered to be relative contraindication.

Veno-Venous Extra-Corporeal Membrane Oxygenation (ECMO) in a Child with Hemoptysis and Fontan Circulation

Background: Extracorporeal membrane oxygenation is a rescue life support technique used in life threatening conditions of refractory respiratory and/or cardiac distress. Indication for extracorporeal life support in children depends on age and varies from pulmonary to cardiac pathologies. In some cases, it may be used as a bridge to a therapeutic procedure. We described here the management of respiratory failure due to hemoptysis in a child with a Fontan circulation and veno-venous extracorporeal membrane oxygenation which served as a bridge to angio-embolization. Hemoptysis can be a life threatening condition which can lead to hypovolemic shock and impaired alveolar gas exchange. The latter can result in respiratory failure and consequent asphyxia. When hemoptysis occurs in a patient with a univentricular heart and a Fontan circulation, management of this clinical situation can be challenging due to the particular physiology of the latter. Total cavopulmonary connection is a palliative surgical repair which constitutes Fontan circulation as a definitive treatment in patients with a univentricular heart. Methods: Case report description of a 16 year-old boy with a univentricular heart and a Fontan circulation who presented hemoptysis managed with a veno-venous extracorporeal membrane oxygenation (ECMO) as a bridge to angio-embolization. Results: Hemoptysis due to diffuse intra-alveolar hemorrhage from collateral circulation was successfully treated in this young patient with pulmonary vascular embolization. This allowed to wean the patient from extra-corporeal membrane oxygenation. Conclusion: Veno-venous ECMO can be life-saving as a bridge to angio-embolization for severe hemoptysis in patients with Fontan circulation. The reported case allows to underline that our multidisciplinary approach in this complex pediatric patient surely participated to improve outcome.

Condition Metabolic Balance Disturbance in Patients with Cor Pulmonale： Prevalence, Diagnosis, Risk Factors

To study the risk factors for the development of cor pulmonale （CP） in patients with chronic pulmonary diseases in the Republic of Uzbekistan, the disbalance in parameters of stable metabolites oxides of the nitrogen （SMNO）, of blood oxygen saturation （SaO2）, of respiratory function and on lipid peroxidation of cell membrane were measured. The authors evaluated the effect of base therapy and ozone therapy （OT） in patients with CP. Basis therapy and OT resulted in good parameters of SMNo, SaO2 and metabolic activeness of cell, significant positiveness of hypoxemia and parameters of pulmonary ventilation ability and hemodynamics of pulmonary arteria.

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.