Understanding ventilator-induced lung injury: The role of mechanical power.

Mechanical ventilation stands as a life-saving intervention in the management of respiratory failure. However, it carries the risk of ventilator-induced lung injury. Despite the adoption of lung-protective ventilation strategies, including lower tidal volumes and pressure limitations, mortality rates remain high, leaving room for innovative approaches. The concept of mechanical power has emerged as a comprehensive metric encompassing key ventilator parameters associated with the genesis of ventilator-induced lung injury, including volume, pressure, flow, resistance, and respiratory rate. While numerous animal and human studies have linked mechanical power and ventilator-induced lung injury, its practical implementation at the bedside is hindered by calculation challenges, lack of equation consensus, and the absence of an optimal threshold. To overcome the constraints of measuring static respiratory parameters, dynamic mechanical power is proposed for all patients, regardless of their ventilation mode. However, establishing a causal relationship is crucial for its potential implementation, and requires further research. The objective of this review is to explore the role of mechanical power in ventilator-induced lung injury, its association with patient outcomes, and the challenges and potential benefits of implementing a ventilation strategy based on mechanical power.

The Impact of PEEP on Ventilation Distribution in ARDS.

BACKGROUND: The first aim of this study was to evaluate the capacity of electrical impedance tomography (EIT) to identify the effect of PEEP on regional ventilation distribution and the regional risk of collapse, overdistention, hypoventilation, and pendelluft in mechanically ventilated patients. The second aim was to evaluate the feasibility of EIT for estimating airway opening pressure (AOP). METHODS: The EIT signal was recorded both during baseline cyclic ventilation and slow insufflation for one breath for 9 subjects with moderate-to-severe ARDS. From these data, the AOP and volumes insufflated to lung regions with or without the risk of either collapse, overdistention, hypoventilation, or pendelluft were assessed at 3 PEEP levels (5, 10, and 15 cm H2O). PEEP levels were compared by Friedman analysis of variance and the AOP measured by EIT evaluated using an F-test and the Bland and Altman method. RESULTS: The volume for which there was no specific risk significantly decreased at the highest PEEP from 55 ± 31% tidal volume (VT) at PEEP 5 or 82 ± 18% VT at PEEP 10 to 10 ± 30% VT at PEEP 15 (P = .038 between PEEP 5 vs PEEP 15; P = .01 between PEEP 10 vs PEEP 15). The volume associated with overdistention significantly increased with increasing PEEP, whereas that associated with atelectrauma significantly decreased. Pendelluft significantly decreased with increasing PEEP: VT of 8.9 ± 18.6%, 3.6 ± 7.0%, and 3.2 ± 7.1% for PEEP 5, PEEP 10, and PEEP 15, respectively. The center of ventilation tended to increase in the dependent direction with higher PEEP. The AOPs assessed by EIT and from the pressure-volume curve were in good agreement (bias 0.48 cm H2O). CONCLUSIONS: Our results suggest that EIT could aid clinicians in making personalized and reasoned choices in setting the PEEP for subjects with ARDS.

Risk of Transient Tachypnea of the Newborn following Elective Cesarean Section Increases at a Gestational Age of 37 Weeks Compared to That at ≥ 38 Weeks Despite the Exclusion of Pre-Existing Risk Factors for Neonatal Respiratory Disorders.

Background: Elective cesarean sections (ECSs) for early-term pregnancies at 37 weeks of gestational age (GA) aim to reduce the risk of emergency cesarean sections due to the onset of labor or rupture of membranes. However, resultant increases in neonatal respiratory disorders, including transient tachypnea of the newborn (TTN) have been observed. However, few studies have elucidated the associated risk factors. Consequently, we aimed to determine whether differences existed in the clinical outcomes between neonates delivered via ECS at 37 weeks and those delivered at ≥ 38 weeks of GA. Methods: A retrospective analysis was conducted on 259 neonates born via ECS at Tottori University Hospital, between January 2013 and December 2019, with birthweights ≥ 2500 g and GAs > 37 weeks. The neonates were categorized into two cohorts: births at 37 and at ≥ 38 weeks of GA (37-week and 38-week cohorts). The principal clinical outcomes included the appearance, pulse, grimace, activity, and respiration (Apgar) scores, need for positive-pressure ventilation, incidence of TTN, and length of hospital stay. Results: No statistically significant differences were observed in the indications for ECS, sex, or birthweight between the two cohorts. The 37-week cohort exhibited a lower 1-min Apgar score than did the 38-week cohort, with no statistically significant differences between the two cohorts, at 5 min. Statistically significant differences were not observed in the need for positive-pressure ventilation during initial resuscitation or length of hospital stay for patients with TTN between the two cohorts. Notably, the 37-week cohort exhibited a significantly higher incidence of TTN than did the 38-week cohort. Conclusion: ECSs at 37 weeks of GA exhibited an increased risk of TTN than ECSs at ≥ 38 weeks of GA. Strategic neonatal care and adequate preparation can mitigate this risk without affecting the length of hospital stay.

Expiratory flow limitation during mechanical ventilation: real-time detection and physiological subtypes.

BACKGROUND: Tidal expiratory flow limitation (EFLT) complicates the delivery of mechanical ventilation but is only diagnosed by performing specific manoeuvres. Instantaneous analysis of expiratory resistance (Rex) can be an alternative way to detect EFLT without changing ventilatory settings. This study aimed to determine the agreement of EFLT detection by Rex analysis and the PEEP reduction manoeuvre using contingency table and agreement coefficient. The patterns of Rex were explored. METHODS: Medical patients ≥ 15-year-old receiving mechanical ventilation underwent a PEEP reduction manoeuvre from 5 cmH2O to zero for EFLT detection. Waveforms were recorded and analyzed off-line. The instantaneous Rex was calculated and was plotted against the volume axis, overlapped by the flow-volume loop for inspection. Lung mechanics, characteristics of the patients, and clinical outcomes were collected. The result of the Rex method was validated using a separate independent dataset. RESULTS: 339 patients initially enrolled and underwent a PEEP reduction. The prevalence of EFLT was 16.5%. EFLT patients had higher adjusted hospital mortality than non-EFLT cases. The Rex method showed 20% prevalence of EFLT and the result was 90.3% in agreement with PEEP reduction manoeuvre. In the validation dataset, the Rex method had resulted in 91.4% agreement. Three patterns of Rex were identified: no EFLT, early EFLT, associated with airway disease, and late EFLT, associated with non-airway diseases, including obesity. In early EFLT, external PEEP was less likely to eliminate EFLT. CONCLUSIONS: The Rex method shows an excellent agreement with the PEEP reduction manoeuvre and allows real-time detection of EFLT. Two subtypes of EFLT are identified by Rex analysis. TRIAL REGISTRATION: Clinical trial registered with www.thaiclinicaltrials.org (TCTR20190318003). The registration date was on 18 March 2019, and the first subject enrollment was performed on 26 March 2019.

Comparison of lung aeration loss in open abdominal oncologic surgeries after ventilation with electrical impedance tomography-guided PEEP versus conventional PEEP: a pilot feasibility study.

BACKGROUND: Existing literature lacks high-quality evidence regarding the ideal intraoperative positive end-expiratory pressure (PEEP) to minimize postoperative pulmonary complications (PPCs). We hypothesized that applying individualized PEEP derived from electrical impedance tomography would reduce the severity of postoperative lung aeration loss, deterioration in oxygenation, and PPC incidence. METHODS: A pilot feasibility study was conducted on 36 patients who underwent open abdominal oncologic surgery. The patients were randomized to receive individualized PEEP or conventional PEEP at 4 cmH2O. The primary outcome was the impact of individualized PEEP on changes in the modified lung ultrasound score (MLUS) derived from preoperative and postoperative lung ultrasonography. A higher MLUS indicated greater lung aeration loss. The secondary outcomes were the PaO2/FiO2 ratio and PPC incidence. RESULTS: A significant increase in the postoperative MLUS (12.0 ± 3.6 vs 7.9 ± 2.1, P < 0.001) and a significant difference between the postoperative and preoperative MLUS values (7.0 ± 3.3 vs 3.0 ± 1.6, P < 0.001) were found in the conventional PEEP group, indicating increased lung aeration loss. In the conventional PEEP group, the intraoperative PaO2/FiO2 ratios were significantly lower but not the postoperative ratios. The PPC incidence was not significantly different between the groups. Post-hoc analysis showed the increase in lung aeration loss and deterioration of intraoperative oxygenation correlated with the deviation from the individualized PEEP. CONCLUSIONS: Individualized PEEP appears to protect against lung aeration loss and intraoperative oxygenation deterioration. The advantage was greater in patients whose individualized PEEP deviated more from the conventional PEEP.

Positive end-expiratory pressure limits inspiratory effort through modulation of the effort-to-drive ratio: an experimental crossover study.

BACKGROUND: How assisted spontaneous breathing should be used during acute respiratory distress syndrome is questioned. Recent evidence suggests that high positive end-expiratory pressure (PEEP) may limit the risk of patient self-inflicted lung injury (P-SILI). The aim of this study was to assess the effects of PEEP on esophageal pressure swings, inspiratory drive, and the neuromuscular efficiency of ventilation. We hypothesized that high PEEP would reduce esophageal pressure swings, regardless of inspiratory drive changes, by modulating the effort-to-drive ratio (EDR). This was tested retrospectively in an experimental animal crossover study. Anesthetized pigs (n = 15) were subjected to mild to moderate lung injury and different PEEP levels were applied, changing PEEP from 0 to 15 cmH2O and back to 0 cmH2O in steps of 3 cmH2O. Airway pressure, esophageal pressure (Pes), and electric activity of the diaphragm (Edi) were collected. The EDR was calculated as the tidal change in Pes divided by the tidal change in Edi. Statistical differences were tested using the Wilcoxon signed-rank test. RESULTS: Inspiratory esophageal pressure swings decreased from - 4.2 ± 3.1 cmH2O to - 1.9 ± 1.5 cmH2O (p < 0.01), and the mean EDR fell from - 1.12 ± 1.05 cmH2O/µV to - 0.24 ± 0.20 (p < 0.01) as PEEP was increased from 0 to 15 cmH2O. The EDR was significantly correlated to the PEEP level (rs = 0.35, p < 0.01). CONCLUSIONS: Higher PEEP limits inspiratory effort by modulating the EDR of the respiratory system. These findings indicate that PEEP may be used in titration of the spontaneous impact on ventilation and in P-SILI risk reduction, potentially facilitating safe assisted spontaneous breathing. Similarly, ventilation may be shifted from highly spontaneous to predominantly controlled ventilation using PEEP. These findings need to be confirmed in clinical settings.

Effect of individualized positive end-expiratory pressure guided by driving pressure on lung protection after laparoscopic radical gastrectomy in elderly patients / 天津医药

Objective To explore the effect of individualized positive end expiratory pressure guided by driving pressure on lung protection after laparoscopic radical gastrectomy for elderly patients.Methods A total of 64 patients underwent elective laparoscopic radical gastrectomy for gastric cancer in the Second Affiliated Hospital of Anhui Medical University were selected.According to the random number table method,patients were divided into the driving the pressure guided individualized positive end-expiratory pressure(PEEP)group(experimental group)and the fixed PEEP group(control group),32 cases in each group.In the control group,PEEP = 5 cmH2O.In the experimental group,PEEP titration was performed according to the increasing method,and the PEEP corresponding to the lowest driving pressure was selected until extubation.Peak airway pressure(Ppeak),plateau airway pressure(Pplat)and PEEP were recorded at 5 min after intubation(T1),immediately after PEEP titration(T2),1 h after operation(T3),2 h after operation(T4),and 10 min after pneumoperitoneum release(T5).Driving pressure(ΔP)and lung dynamic compliance(Cdyn)were calculated.Arterial blood was collected at T1-5 for blood gas analysis,arterial partial pressure of oxygen(PaO2)was recorded,and oxygenation index(OI)was calculated.The occurrence of pulmonary complications(PPCs)within 7 days after operation was recorded.Modified clinical pulmonary infection score(mCPIS)was recorded on the second day after operation.The pulmonary function was evaluated before operation,1 day,3 days and 5 days after operation.Results Compared with T1,Ppeak,Pplat and ΔP were increased and Cdyn was decreased at T2-5,while OI was decreased at T4 in control group(P＜0.05).Compared with the control group,Ppeak,Pplat and Cdyn in the experimental group were increased at T2-5,ΔP was decreased,and OI was increased at T3-5(P＜0.05).Compared with the preoperative results,FVC at 1,3 and 5 days after surgery was decreased,and FEV1 and maximum expiratory flow(PEF)were decreased 1 and 3 days after surgery in the experimental groups(P＜0.05).Compared with the control group,FVC,FEV1 and PEF were higher 1 day after operation in the experimental group(P＜0.05).Compared with the preoperative results,mCPIS scores of the two groups were higher on the second day after surgery(P＜0.05).Compared with the control group,the mCPIS score was lower on day 2 after surgery in the experimental group(P＜0.05).The incidence of PPCs within 7 days after surgery was lower in the experimental group than that in the control group(15.6%vs.40.6%).Conclusion Individualized PEEP guided by drive pressure can improve lung compliance,reduce drive pressure,improve oxygenation function and early postoperative lung function,reduce the incidence of postoperative lung complications,and has a certain lung protection effect.

Technical operating points of polysomnography-assisted drug-induced sleep endoscopic positive airway pressure titration / 天津医药

Recognizing upper airway obstruction and stenosis is critical to determine the subsequent treatment options in patients with obstructive sleep apnea(OSA).Drug-induced sleep endoscopy(DISE)is a 3D visual evaluation technology for the anatomical structure of the upper respiratory tract of OSA patients during"sleeping"state after being anesthetized.The dynamic situation of upper respiratory tract obstruction and collapse can be observed safely and quickly through endoscopy,which provides important reference for formulating surgical methods and positive airway pressure(PAP)intervention treatments.With the assistance of polysomnography(PSG),DISE plays an important role in optimizing individualized treatment plans for OSA.The present article introduces the technical operating points of PSG-assisted drug-induced sleep endoscopic positive airway pressure titration.

Effect of individualized PEEP titration based on open-lung strategy on intraoperative thoracic fluid content in elderly patients undergoing transurethral ultrasound-guided laser-induced prostatectomy / 中华麻醉学杂志

Objective:To evaluate the effect of individualized positive end-expiratory pressure (PEEP) titration based on open-lung strategy on the intraoperative thoracic fluid content (TFC) in elderly patients undergoing transurethral ultrasound-guided laser-induced prostatectomy (TULIP).Methods:Eighty-six American Society of Anesthesiologists Physical Status classification Ⅱ or Ⅲ, patients, aged 65-80 yr, with body mass index of 18-28 kg/m 2, scheduled for elective TULIP, were divided into 2 groups ( n=43 each) by the random number table method: fixed PEEP group (group C) and individualized PEEP titration group (group P). PEEP was set at 4 cmH 2O after routine mechanical ventilation in group C. Patients underwent pulmonary recruitment maneuvers combined with individualized PEEP titration during surgery in group P. TFC was measured using a non-invasive cardiac output monitor at 5 min after tracheal intubation (T 0), 30 min after PEEP titration and ventilation (T 1), 5 min before surgery (T 2), and 5 min before leaving the recovery room (T 3). Cardiac output, oxygenation index and stroke volume index were recorded from T 0-T 2, arterial blood gas analysis was simultaneously performed to record peak airway pressure and dynamic lung compliance, and oxygenation index was calculated. The duration of postanesthesia care unit stay, pulmonary complications within 7 days after surgery, and length of hospital stay were also recorded. Results:Eighty-three patients were finally included, with 42 in group C and 41 in group P. Compared with group C, TFC was significantly decreased at T 1-T 3, cardiac index, cardiac output and stroke volume index were decreased at T 1, dynamic lung compliance, PaO 2 and oxygenation index were increased at T 1 and T 2, PaCO 2 was decreased, the incidence of postoperative pulmonary complications was reduced, and the duration of postanesthesia care unit stay and postoperative length of hospital stay were shortened in group P ( P<0.05). Conclusions:Individualized PEEP titration based on open-lung strategy can effectively decrease TFC and improve intraoperative oxygenation and prognosis in elderly patients undergoing TULIP.

Effect of lung recruitment maneuvers combined with individualized positive end-expiratory pressure on degree of postoperative atelectasis in elderly patients undergoing laparoscopic surgery / 中华麻醉学杂志

Objective:To evaluate the effect of lung recruitment maneuvers combined with individualized positive end-expiratory pressure(PEEP) on the degree of postoperative atelectasis in elderly patients undergoing laparoscopic surgery.Methods:One hundred and forty-three elderly patients, aged ≥65 yr, with body mass index of 18.5-30.0 kg/m 2, scheduled for elective laparoscopic surgery, were assigned to either individualized PEEP combined with recruitment maneuvers (group Ⅱ) or fixed PEEP (group Ⅰ) using a random number table method. PEEP was maintained at 6 cmH 2O starting from the beginning of procedure until the end of the procedure in group I. Individualized PEEP titration was performed after induction of anesthesia in group Ⅱ. The primary outcome measure was the 12-zone lung ultrasound score at 15 min after tracheal extubation. Other outcome measures were the occurrence of postoperative pulmonary complications within 7 days after surgery, Quality of Recovery-15 scale score on 3rd day after surgery, rate of unplanned admission to intensive care units, length of hospital stay, incidence of intraoperative hypoxemia, usage rate of intraoperative vasoactive drugs, and incidence of postoperative hypotension. Results:Compared with group Ⅰ, the lung ultrasound score, driving pressure and postoperative pulmonary complications were significantly decreased, the dynamic lung compliance was increased ( P<0.05 or 0.01), and no significant changes were found in the other parameters in group Ⅱ ( P>0.05). Conclusions:Individualized PEEP combined with recruitment maneuvers can reduce the degree of postoperative atelectasis in elderly patients undergoing laparoscopic surgery.

Comparison of the effects of open and closed aspiration on end-expiratory lung volume in acute respiratory distress syndrome.

BACKGROUND: Alveoli tend to collapse in patients with acute respiratory distress syndrome (ARDS). Endotracheal aspiration may increase alveolar collapse due to the loss of end-expiratory lung volume (EELV). We aimed to compare the loss of EELV after open and closed suction in patients with ARDS. METHODS: This randomized crossover study included 20 patients receiving invasive mechanical ventilation for ARDS. Open and closed suction were applied in a random order. Lung impedance was measured using electric impedance tomography. The change in end-expiratory lung impedance end of suction and at 1, 10, 20, and 30 min after suction, was used to represent the change in EELV. Arterial blood gas analyses and ventilatory parameters such as the plateau pressure (Pplat), driving pressure (Pdrive), and compliance of the respiratory system (CRS) were also recorded. RESULTS: Less volume loss was noted after closed suction than after open suction (mean ΔEELI: -2661 ± 1937 vs. -4415 ± 2363; mean difference: -1753; 95% CI [-2662, -844]; P = 0.001). EELI returned to baseline 10 min after closed suction but did not return to baseline even 30 min after open suction. After closed suction, the Pplat and Pdrive decreased while the CRS increased. Conversely, the Pplat and Pdrive increased while the CRS decreased after open suction. CONCLUSIONS: Endotracheal aspiration may result in alveolar collapse due to loss of EELV. Given that closed suction is associated with less volume loss at end-expiration without worsening ventilatory parameters, it should be chosen over open suction in patients with ARDS.

Prospective, randomized, controlled trial assessing the effects of a driving pressure-limiting strategy for patients with acute respiratory distress syndrome due to community-acquired pneumonia (STAMINA trial): protocol and statistical analysis plan / Estudo randomizado prospectivo e controlado de avaliação dos efeitos de uma estratégia de limitação da driving pressure em pacientes com síndrome do desconforto respiratório agudo devido à pneumonia adquirida na comunidade (estudo STAMINA): protocolo e plano de análise estatística

ABSTRACT Background: Driving pressure has been suggested to be the main driver of ventilator-induced lung injury and mortality in observational studies of acute respiratory distress syndrome. Whether a driving pressure-limiting strategy can improve clinical outcomes is unclear. Objective: To describe the protocol and statistical analysis plan that will be used to test whether a driving pressure-limiting strategy including positive end-expiratory pressure titration according to the best respiratory compliance and reduction in tidal volume is superior to a standard strategy involving the use of the ARDSNet low-positive end-expiratory pressure table in terms of increasing the number of ventilator-free days in patients with acute respiratory distress syndrome due to community-acquired pneumonia. Methods: The ventilator STrAtegy for coMmunIty acquired pNeumoniA (STAMINA) study is a randomized, multicenter, open-label trial that compares a driving pressure-limiting strategy to the ARDSnet low-positive end-expiratory pressure table in patients with moderate-to-severe acute respiratory distress syndrome due to community-acquired pneumonia admitted to intensive care units. We expect to recruit 500 patients from 20 Brazilian and 2 Colombian intensive care units. They will be randomized to a driving pressure-limiting strategy group or to a standard strategy using the ARDSNet low-positive end-expiratory pressure table. In the driving pressure-limiting strategy group, positive end-expiratory pressure will be titrated according to the best respiratory system compliance. Outcomes: The primary outcome is the number of ventilator-free days within 28 days. The secondary outcomes are in-hospital and intensive care unit mortality and the need for rescue therapies such as extracorporeal life support, recruitment maneuvers and inhaled nitric oxide. Conclusion: STAMINA is designed to provide evidence on whether a driving pressure-limiting strategy is superior to the ARDSNet low-positive end-expiratory pressure table strategy for increasing the number of ventilator-free days within 28 days in patients with moderate-to-severe acute respiratory distress syndrome. Here, we describe the rationale, design and status of the trial.

RESUMO Contexto: Em estudos observacionais sobre a síndrome do desconforto respiratório agudo, sugeriu-se que a driving pressure é o principal fator de lesão pulmonar induzida por ventilador e de mortalidade. Não está claro se uma estratégia de limitação da driving pressure pode melhorar os desfechos clínicos. Objetivo: Descrever o protocolo e o plano de análise estatística que serão usados para testar se uma estratégia de limitação da driving pressure envolvendo a titulação da pressão positiva expiratória final de acordo com a melhor complacência respiratória e a redução do volume corrente é superior a uma estratégia padrão envolvendo o uso da tabela de pressão positiva expiratória final baixa do protocolo ARDSNet, em termos de aumento do número de dias sem ventilador em pacientes com síndrome do desconforto respiratório agudo devido à pneumonia adquirida na comunidade. Métodos: O estudo STAMINA (ventilator STrAtegy for coMmunIty acquired pNeumoniA) é randomizado, multicêntrico e aberto e compara uma estratégia de limitação da driving pressure com a tabela de pressão positiva expiratória final baixa do protocolo ARDSnet em pacientes com síndrome do desconforto respiratório agudo moderada a grave devido à pneumonia adquirida na comunidade internados em unidades de terapia intensiva. Esperamos recrutar 500 pacientes de 20 unidades de terapia intensiva brasileiras e duas colombianas. Eles serão randomizados para um grupo da estratégia de limitação da driving pressure ou para um grupo de estratégia padrão usando a tabela de pressão positiva expiratória final baixa do protocolo ARDSnet. No grupo da estratégia de limitação da driving pressure, a pressão positiva expiratória final será titulada de acordo com a melhor complacência do sistema respiratório. Desfechos: O desfecho primário é o número de dias sem ventilador em 28 dias. Os desfechos secundários são a mortalidade hospitalar e na unidade de terapia intensiva e a necessidade de terapias de resgate, como suporte de vida extracorpóreo, manobras de recrutamento e óxido nítrico inalado. Conclusão: O STAMINA foi projetado para fornecer evidências sobre se uma estratégia de limitação da driving pressure é superior à estratégia da tabela de pressão positiva expiratória final baixa do protocolo ARDSnet para aumentar o número de dias sem ventilador em 28 dias em pacientes com síndrome do desconforto respiratório agudo moderada a grave. Aqui, descrevemos a justificativa, o desenho e o status do estudo.

Preintubation Machine-Delivered Pressure Support Ventilation With Positive End-Expiratory Pressure Versus Manual Bag-Mask Ventilation for Oxygenation in Overweight and Obese Patients: A Randomized, Pilot Study.

BACKGROUND: Noninvasive positive pressure ventilation (NIPPV) maintains mean airway pressures well, and its usability for preoxygenation is well described. Anesthesia machine-delivered NIPPV-based preoxygenation has recently been evaluated against the traditional manual bag-mask ventilation (BMV). The efficiency of such a technique over the traditional one is yet to be established well. The present study evaluated the feasibility of machine-delivered preoxygenation using pressure support ventilation (PSV) with positive end-expiratory pressure (PEEP) and compared the effectiveness with BMV. METHODS: Thirty overweight and obese adults belonging to the American Society of Anesthesiologist's physical status I-II were randomized to receive PSV+PEEP or BMV for preintubation preoxygenation targeted to a fraction of expired oxygen (FeO2) of 85% and 90% or for a maximum period of five minutes, whichever came first. Postintubation, the patient was observed for the time taken until 1% desaturation without ventilation. Arterial blood gases, respiratory variables, FeO2 achieved, and different times were collected and compared. RESULTS: The baseline characteristics and arterial blood gases were similar between the two groups. The PSV+PEEP group had consistent and favorable tidal volume and airway pressure delivery. The difference in time to reach a FeO2 of 85% between the two groups was not statistically different. Only two patients achieved a FeO2 of 90% in the PSV+PEEP group versus none in the BMV group. However, partial pressure of oxygen at 1% desaturation (217.42±109.47 versus 138.073±71.319 mmHg, p 0.0259) was higher in the PSV+PEEP group. Similarly, the time until 1% desaturation was significantly prolonged in the PSV+PEEP group (206.6±76.952 versus 140.466±54.245 seconds, p 0.0111). CONCLUSION: The present pilot study findings indicate that preintubation machine-delivered PSV+PEEP-based preoxygenation is feasible and might be more effective than traditional BMV in overweight and obese patients.

Pressure- vs. volume-controlled ventilation and their respective impact on dynamic parameters of fluid responsiveness: a cross-over animal study.

BACKGROUND AND GOAL OF STUDY: Pulse pressure variation (PPV) and stroke volume variation (SVV), which are based on the forces caused by controlled mechanical ventilation, are commonly used to predict fluid responsiveness. When PPV and SVV were introduced into clinical practice, volume-controlled ventilation (VCV) with tidal volumes (VT) ≥ 10 ml kg- 1 was most commonly used. Nowadays, lower VT and the use of pressure-controlled ventilation (PCV) has widely become the preferred type of ventilation. Due to their specific flow characteristics, VCV and PCV result in different airway pressures at comparable tidal volumes. We hypothesised that higher inspiratory pressures would result in higher PPVs and aimed to determine the impact of VCV and PCV on PPV and SVV. METHODS: In this self-controlled animal study, sixteen anaesthetised, paralysed, and mechanically ventilated (goal: VT 8 ml kg- 1) pigs were instrumented with catheters for continuous arterial blood pressure measurement and transpulmonary thermodilution. At four different intravascular fluid states (IVFS; baseline, hypovolaemia, resuscitation I and II), ventilatory and hemodynamic data including PPV and SVV were assessed during VCV and PCV. Statistical analysis was performed using U-test and RM ANOVA on ranks as well as descriptive LDA and GEE analysis. RESULTS: Complete data sets were available of eight pigs. VT and respiratory rates were similar in both forms. Heart rate, central venous, systolic, diastolic, and mean arterial pressures were not different between VCV and PCV at any IVFS. Peak inspiratory pressure was significantly higher in VCV, while plateau, airway and transpulmonary driving pressures were significantly higher in PCV. However, these higher pressures did not result in different PPVs nor SVVs at any IVFS. CONCLUSION: VCV and PCV at similar tidal volumes and respiratory rates produced PPVs and SVVs without clinically meaningful differences in this experimental setting. Further research is needed to transfer these results to humans.

Positive- vs. negative-pressure extubation technique: a scoping review.

Objectives: This review aimed to summarize the recent literature on positive-pressure extubation. Design: A scoping review was conducted under the framework of the Joanna Briggs Institute. Data sources: Web of Science, PubMed, Ovid, Cumulative Index to Nursing & Allied Health, EBSCO, Cochrane Library, Wan Fang Data, China National Knowledge Infrastructure, and China Biology Medicine databases were searched for studies on adults and children. Study selection: All articles describing the use of positive-pressure extubation were considered eligible for inclusion. The exclusion criteria were articles not available in English or Chinese, and those without full text available. Data extraction and synthesis: The database searches identified 8,381 articles, 15 of which could be included in this review, with an aggregated patient number of 1,544. Vital signs, including mean arterial pressure, heart rate, R-R interval, and SpO2 before and after extubation; blood gas analysis indexes, including pH, oxygen saturation, PaO2, and PaCO2 before and after extubation; and incidence of respiratory complications, including bronchospasm, laryngeal edema, aspiration atelectasis, hypoxemia, and hypercapnia, were reported in the included studies. Results: The majority of these studies reported that the positive-pressure extubation technique can maintain stable vital signs and blood gas analysis indices as well as prevent complications during the peri-extubation period. Conclusions: The positive-pressure extubation technique has a safety performance similar to that of the traditional negative-pressure extubation technique and may lead to better clinical outcomes, including stable vital signs, arterial blood gas analysis, and a lower incidence of respiratory complications.

Capnodynamic monitoring of lung volume and pulmonary blood flow during alveolar recruitment: a prospective observational study in postoperative cardiac patients.

Alveolar recruitment manoeuvres may mitigate ventilation and perfusion mismatch after cardiac surgery. Monitoring the efficacy of recruitment manoeuvres should provide concurrent information on pulmonary and cardiac changes. This study in postoperative cardiac patients applied capnodynamic monitoring of changes in end-expiratory lung volume and effective pulmonary blood flow. Alveolar recruitment was performed by incremental increases in positive end-expiratory pressure (PEEP) to a maximum of 15 cmH2O from a baseline of 5 cmH2O over 30 min. The change in systemic oxygen delivery index after the recruitment manoeuvre was used to identify responders (> 10% increase) with all other changes (≤ 10%) denoting non-responders. Mixed factor ANOVA using Bonferroni correction for multiple comparisons was used to denote significant changes (p < 0.05) reported as mean differences and 95% CI. Changes in end-expiratory lung volume and effective pulmonary blood flow were correlated using Pearson's regression. Twenty-seven (42%) of 64 patients were responders increasing oxygen delivery index by 172 (95% CI 61-2984) mL min-1 m-2 (p < 0.001). End-expiratory lung volume increased by 549 (95% CI 220-1116) mL (p = 0.042) in responders associated with an increase in effective pulmonary blood flow of 1140 (95% CI 435-2146) mL min-1 (p = 0.012) compared to non-responders. A positive correlation (r = 0.79, 95% CI 0.5-0.90, p < 0.001) between increased end-expiratory lung volume and effective pulmonary blood flow was only observed in responders. Changes in oxygen delivery index after lung recruitment were correlated to changes in end-expiratory lung volume (r = 0.39, 95% CI 0.16-0.59, p = 0.002) and effective pulmonary blood flow (r = 0.60, 95% CI 0.41-0.74, p < 0.001). Capnodynamic monitoring of end-expiratory lung volume and effective pulmonary blood flow early in postoperative cardiac patients identified a characteristic parallel increase in both lung volume and perfusion after the recruitment manoeuvre in patients with a significant increase in oxygen delivery.Trial registration This study was registered on ClinicalTrials.gov (NCT05082168, 18th of October 2021).

Early Prone versus Supine Positioning in Moderate to Severe Coronavirus Disease 2019 Patients with Acute Respiratory Distress Syndrome.

Objectives: This study sought to determine whether early prone positioning of patients with moderate to severe COVID-19-related acute respiratory distress syndrome (ARDS) lowers the mortality rate. Methods: We conducted a retrospective study using data from intensive care units of two tertiary centers in Oman. Adult patients with moderate to severe COVID-19-related ARDS with a PaO2/FiO2 ratio < 150 on FiO2 of 60% or more and a positive end-expiratory pressure of at least 8 cm H2O who were admitted between 1 May 2020 and 31 October 2020 were selected as participants. All patients were intubated and subjected to mechanical ventilation within 48 hours of admission and placed in either prone or supine position. Mortality was measured and compared between the patients from the two groups. Results: A total of 235 patients were included (120 in the prone group and 115 in the supine group). There were no significant differences in mortality (48.3% vs. 47.8%; p =0.938) and discharge rates (50.8% vs. 51.3%; p =0.942) between the prone and supine groups, respectively. Conclusions: Early prone positioning of patients with COVID-19-related ARDS does not result in a significant reduction in mortality.

Efficacy and safety of long-term use of a positive expiratory pressure device in chronic obstructive pulmonary disease patients, a randomized controlled trial.

BACKGROUND: Exercise intolerance is among the most common symptoms experienced by patients with chronic obstructive pulmonary disease (COPD), which is associated with lung dynamic hyperinflation (DH). There was evidence that positive expiratory pressure (PEP), which could be offered by less costly devices, could reduce DH. The purpose of this study was to evaluate the efficacy and safety of long-term domiciliary use of PEP device in subjects with COPD. METHODS: A randomized controlled trial was conducted and 25 Pre-COPD or mild-to-very severe subjects with COPD were randomized to intervention group (PEP device, PEP = 5 cmH2O, n = 13) and control group (Sham-PEP device, PEP = 0 cmH2O, n = 12). PEP device was a spring-loaded resistor face mask. Subjects were treated 4 h per day for a total of 2 months. Six-minute walk test (6MWT), pulmonary function, the Modified British Medical Research Council score, and partial pressure of end-tidal carbon dioxide were evaluated at baseline and after two months. RESULTS: The 6MWD (- 71.67 ± 8.70 m, P < 0.001), end-dyspnea (P = 0.002), and end-fatigue (P = 0.022) improved significantly in the intervention group when compared with the control group. All subjects in the intervention group reported that 4 h of daily use of the PEP device was well tolerated and accepted and there were no adverse events. CONCLUSION: Regular daily use of PEP device is safe and may improve exercise capacity in subjects with COPD or pre-COPD. PEP device could be used as an add-on to pulmonary rehabilitation programs due to its efficacy, safety, and low cost. TRIAL REGISTRATION: The study was prospectively registered on ClinicalTrials.gov (NCT04742114).

What should an intensivist know about pneumocephalus and tension pneumocephalus?

Collection of air in the cranial cavity is called pneumocephalus. Although simple pneumocephalus is a benign condition, accompanying increased intracranial pressure can produce a life-threatening condition comparable to tension pneumothorax, which is termed tension pneumocephalus. We report a case of tension pneumocephalus after drainage of a cerebrospinal fluid hygroma. The tension pneumocephalus was treated with decompression craniotomy, but the patient later died due to the complications related to critical care. Traumatic brain injury and neurosurgical intervention are the most common causes of pneumocephalus. Pneumocephalus and tension pneumocephalus are neurosurgical emergencies, and anesthetics and intensive care management like the use of nitrous oxide during anesthesia and positive pressure ventilation have important implications in their development and progress. Clinically, patients can present with various nonspecific neurological manifestations that are indistinguishable from a those of a primary neurological condition. If the diagnosis is questionable, patients should be investigated using computed tomography of the brain. Immediate neurosurgical consultation with decompression is the treatment of choice.

Clinical effects of bi-level positive airway pressure and heated humidified high flow nasal cannula ventilation as initial treatment for premature infants with respiratory distress syndrome / 中国新生儿科杂志

Objective:To compare the efficacy and safety of bi-level positive airway pressure (BiPAP) ventilation and heated humidified high flow nasal cannula (HHHFNC) ventilation as initial respiratory support for premature infants with respiratory distress syndrome (RDS).Methods:From January 2019 to June 2021, premature infants [gestational age (GA) 28~35 weeks)] with grade Ⅰ to Ⅲ RDS admitted to Suining County People's Hospital were prospectively enrolled. The infants were randomly assigned into BiPAP group and HHHFNC group. The clinical characteristics, ventilation efficacy and complications were analyzed.Results:A total of 33 infants were in BiPAP group and 32 in HHHFNC group. No significant differences existed between the two groups in the following items: the frequency of apnea within 24 h of ventilation, FiO 2 and PaCO 2 at 24 h, the use of pulmonary surfactant (PS), the incidence of non-invasive ventilation failure within 72 h, non-invasive ventilation duration and the age achieving total enteral nutrition. HHHFNC group had lower score in premature infants pain profile (PIPP) than BiPAP group at 24 h of non-invasive ventilation [4 (3, 6) vs. 8 (6, 11), P<0.001]. No significant differences existed in nasal injury, pneumothorax, intraventricular hemorrhage, necrotizing enterocolitis, bronchopulmonary dysplasia and mortality rate between the two groups ( P>0.05). Conclusions:As the initial treatment for premature infants with grade Ⅰ to Ⅲ RDS, BiPAP and HHHFNC has similar rates of non-invasive ventilation failure within 72 h,non-invasive ventilation duration and adverse events. HHHFNC may ease the pain of the infants.