BACKGROUND: The arterial pressure of oxygen (PaO2)/inspiratory fraction of oxygen (FiO2) is associated with in-hospital mortality in patients with Coronavirus Disease 2019 (COVID-19) pneumonia. ΔPaO2/FiO2 [the difference between PaO2/FiO2 after 24 h of invasive mechanical ventilation (IMV) and PaO2/FiO2 before IMV] is associated with in-hospital mortality. However, the value of PaO2 can be influenced by the end-expiratory pressure (PEEP). To the best of our knowledge, the relationship between the ratio of (ΔPaO2/FiO2)/PEEP and in-hospital mortality remains unclear. This study aimed to evaluate their association.
METHODS: The study was conducted in southern Peru from April 2020 to April 2021. A total of 200 patients with COVID-19 pneumonia requiring IMV were included in the present study. We analyzed the association between (ΔPaO2/FiO2)/PEEP and in-hospital mortality by Cox proportional hazards regression models.
RESULTS: The median (ΔPaO2/FiO2)/PEEP was 11.78 mmHg/cmH2O [interquartile range (IQR) 8.79-16.08 mmHg/cmH2O], with a range of 1 to 44.36 mmHg/cmH2O. Patients were divided equally into two groups [low group (< 11.80 mmHg/cmH2O), and high group (≥ 11.80 mmHg/cmH2O)] according to the (ΔPaO2/FiO2)/PEEP ratio. In-hospital mortality was lower in the high (ΔPaO2/FiO2)/PEEP group than in the low (ΔPaO2/FiO2)/PEEP group [18 (13%) vs. 38 (38%)]; hazard ratio (HR), 0.33 [95% confidence intervals (CI), 0.17-0.61, P < 0.001], adjusted HR, 0.32 (95% CI, 0.11-0.94, P = 0.038). The finding that the high (ΔPaO2/FiO2)/PEEP group exhibited a lower risk of in-hospital mortality compared to the low (ΔPaO2/FiO2)/PEEP group was consistent with the results from the sensitivity analysis. After adjusting for confounding variables, we found that each unit increase in (ΔPaO2/FiO2)/PEEP was associated with a 12% reduction in the risk of in-hospital mortality (HR, 0.88, 95%CI, 0.80-0.97, P = 0.013).
CONCLUSIONS: The (ΔPaO2/FiO2)/PEEP ratio was associated with in-hospital mortality in patients with COVID-19 pneumonia. (ΔPaO2/FiO2)/PEEP might be a marker of disease severity in COVID-19 patients.

BACKGROUND The concept of driving pressure (ΔP) has been established to optimize mechanical ventilation-induced lung injury. However, little is known about the specific effects of setting individualized positive end-expiratory pressure (PEEP) with driving pressure guidance on patient diaphragm function. MATERIAL AND METHODS Ninety patients were randomized into 3 groups, with PEEP set to 0 in group C; 5 cmH₂O in group F; and individualized PEEP in group I, based on esophageal manometry. Diaphragm ultrasound was performed in the supine position at 6 consecutive time points from T0-T5: diaphragm excursion, end-expiratory diaphragm thickness (Tdi-ee), and diaphragm thickening fraction (DTF) were measured. Primary indicators included diaphragm excursion, Tdi-ee, and DTF at T0-T5, and the correlation between postoperative DTF and ΔP. Secondary indicators included respiratory mechanics, hemodynamic changes at intraoperative d0-d4 time points, and postoperative clinical pulmonary infection scores. RESULTS (1) Diaphragm function parameters reached the lowest point at T1 in all groups (P<0.001). (2) Compared with group C, diaphragm excursion decreased, Tdi-ee increased, and DTF was lower in groups I and F at T1-T5, with significant differences (P<0.05), but the differences between groups I and F were not significant (P>0.05). (3) DTF was significantly and positively correlated with mean intraoperative ΔP in each group at T3, and the correlation was stronger at higher levels of ΔP. CONCLUSIONS Individualized PEEP, achieved by esophageal manometry, minimizes diaphragmatic injury caused by mechanical ventilation based on lung protection, but its protection of the diaphragm during laparoscopic surgery is not superior to that of conventional ventilation strategies.

OBJECTIVE: Patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD) combined with severe type II respiratory failure have a high probability of ventilation failure using conventional non-invasive positive pressure ventilation (NPPV). This study aims to investigate the clinical efficacy of high intensity NPPV (HI-NPPV) for the treatment of AECOPD combined with severe type II respiratory failure.
METHODS: The data of patients with AECOPD combined with severe type II respiratory failure (blood gas analysis pH≤7.25) treated with NPPV in the Second Affiliated Hospital of Chongqing Medical University from July 2013 to July 2023 were collected to conduct a retrospective case-control study. The patients were divided into 2 groups according to the inspired positive airway pressure (IPAP) used during the NPPV treatment: a NPPV group (IPAP<20 cmH2O, 1 cmH2O=0.098 kPa) and a HI-NPPV group (20 cmH2O≤IPAP< 30 cmH2O). Ninety-nine and 95 patients were included in the NPPV group and the HI-NPPV group, respectively. A total of 86 pairs of data were matched using propensity score matching (PSM) for data matching. The primary outcome indexes (mortality and tracheal intubation rate) and secondary outcome indexes [blood gas analysis pH, arterial partial pressure of oxygen (PaO2) and arterial partial pressure of carbon dioxide (PaCO2), adverse reaction rate, and length of hospitalization] were compared between the 2 groups.
RESULTS: The tracheal intubation rates of the NPPV group and the HI-NPPV group were 6.98% and 1.16%, respectively, and the difference between the 2 groups was statistically significant (χ2=4.32, P<0.05); the mortality of the NPPV group and the HI-NPPV group was 23.26% and 9.30%, respectively, and the difference between the 2 groups was statistically significant (χ2=11.64, P<0.01). The PaO2 at 24 h and 48 h after treatment of the HI-NPPV group was higher than that of the NPPV group, and the PaCO2 of the HI-NPPV group was lower than that of the NPPV group, and the differences were statistically significant (all P<0.05). The differences of pH at 24 h and 48 h after treatment between the 2 groups were not statistically significant (both P>0.05). The differences between the 2 groups in adverse reaction rate and hospitalization length were not statistically significant (both P>0.05).
CONCLUSIONS: HI-NPPV can reduce mortality and tracheal intubation rates by rapidly improving the ventilation of patients with AECOPD combined with severe type II respiratory failure. This study provides a new idea for the treatment of patients with AECOPD combined with severe type II respiratory failure.
目的: 慢性阻塞性肺疾病急性加重(acute exacerbation of chronic obstructive pulmonary disease，AECOPD)合并严重II型呼吸衰竭患者使用常规无创正压通气(non-invasive positive pressure ventilation，NPPV)通气失败的概率较高。本研究旨在探讨高压力NPPV(high intensity NPPV，HI-NPPV)治疗AECOPD合并严重II型呼吸衰竭的临床疗效。方法: 收集2013年7月至2023年7月因AECOPD伴严重II型呼吸衰竭(血气分析pH值≤7.25)在重庆医科大学附属第二医院进行NPPV治疗的患者资料，进行回顾性病例对照研究。根据NPPV治疗过程中采用的吸气相气道正压(inspired positive airway pressure，IPAP)将患者分为2组：NPPV组(IPAP<20 cmH2O，1 cmH2O=0.098 kPa)和HI-NPPV组(20 cmH2O≤IPAP<30 cmH2O)。NPPV组和HI-NPPV组分别纳入99和95例患者。通过倾向性得分匹配法(propensity score matching，PSM)进行数据配比，共匹配得到86对数据。比较2组的主要结局指标(病死率、气管插管率)及次要结局指标[血气分析的pH值、动脉血氧分压(arterial partial pressure of oxygen，PaO2)和动脉血二氧化碳分压(arterial partial pressure of carbon dioxide，PaCO2)，不良反应率，住院时长]。结果: NPPV组和HI-NPPV组的气管插管率分别为6.98%和1.16%，2组之间差异有统计学意义(χ2=4.32，P<0.05)；NPPV组和HI-NPPV组的病死率分别为23.26%和9.30%，2组之间差异有统计学意义(χ2=11.64，P<0.01)。HI-NPPV组治疗后24、48 h的PaO2均高于NPPV组，PaCO2均低于NPPV组，差异均有统计学意义(均P<0.05)；治疗后24、48 h，2组之间pH值的差异无统计学意义(均 P>0.05)。2组在不良反应率、住院时长方面的差异均无统计学意义(均P>0.05)。结论: HI-NPPV可通过迅速改善AECOPD合并严重II型呼吸衰竭患者的通气状态，从而降低病死率及插管率，本研究为AECOPD合并严重II型呼吸衰竭患者的治疗提供了新的思路。.

BACKGROUND: During one-lung ventilation (OLV), positive end-expiratory pressure (PEEP) can improve lung aeration but might overdistend lung units and increase intrapulmonary shunt. The authors hypothesized that higher PEEP shifts pulmonary perfusion from the ventilated to the nonventilated lung, resulting in a U-shaped relationship with intrapulmonary shunt during OLV.
METHODS: In nine anesthetized female pigs, a thoracotomy was performed and intravenous lipopolysaccharide infused to mimic the inflammatory response of thoracic surgery. Animals underwent OLV in supine position with PEEP of 0 cm H2O, 5 cm H2O, titrated to best respiratory system compliance, and 15 cm H2O (PEEP0, PEEP5, PEEPtitr, and PEEP15, respectively, 45 min each, Latin square sequence). Respiratory, hemodynamic, and gas exchange variables were measured. The distributions of perfusion and ventilation were determined by IV fluorescent microspheres and computed tomography, respectively.
RESULTS: Compared to two-lung ventilation, the driving pressure increased with OLV, irrespective of the PEEP level. During OLV, cardiac output was lower at PEEP15 (5.5 ± 1.5 l/min) than PEEP0 (7.6 ± 3 l/min) and PEEP5 (7.4 ± 2.9 l/min; P = 0.004), while the intrapulmonary shunt was highest at PEEP0 (PEEP0: 48.1% ± 14.4%; PEEP5: 42.4% ± 14.8%; PEEPtitr: 37.8% ± 11.0%; PEEP15: 39.0% ± 10.7%; P = 0.027). The relative perfusion of the ventilated lung did not differ among PEEP levels (PEEP0: 65.0% ± 10.6%; PEEP5: 68.7% ± 8.7%; PEEPtitr: 68.2% ± 10.5%; PEEP15: 58.4% ± 12.8%; P = 0.096), but the centers of relative perfusion and ventilation in the ventilated lung shifted from ventral to dorsal and from cranial to caudal zones with increasing PEEP.
CONCLUSIONS: In this experimental model of thoracic surgery, higher PEEP during OLV did not shift the perfusion from the ventilated to the nonventilated lung, thus not increasing intrapulmonary shunt.
UNASSIGNED:

OBJECTIVE: Assessing efficacy of electrical impedance tomography (EIT) in optimizing positive end-expiratory pressure (PEEP) for acute respiratory distress syndrome (ARDS) patients to enhance respiratory system mechanics and prevent ventilator-induced lung injury (VILI), compared to traditional methods.
METHODS: We carried out a systematic review and meta-analysis, spanning literature from January 2012 to May 2023, sourced from Scopus, PubMed, MEDLINE (Ovid), Cochrane, and LILACS, evaluated EIT-guided PEEP strategies in ARDS versus conventional methods. Thirteen studies (3 randomized, 10 non-randomized) involving 623 ARDS patients were analyzed using random-effects models for primary outcomes (respiratory mechanics and mechanical power) and secondary outcomes (PaO2/FiO2 ratio, mortality, stays in intensive care unit (ICU), ventilator-free days).
RESULTS: EIT-guided PEEP significantly improved lung compliance (n = 941 cases, mean difference (MD) = 4.33, 95% confidence interval (CI) [2.94, 5.71]), reduced mechanical power (n = 148, MD = - 1.99, 95% CI [- 3.51, - 0.47]), and lowered driving pressure (n = 903, MD = - 1.20, 95% CI [- 2.33, - 0.07]) compared to traditional methods. Sensitivity analysis showed consistent positive effect of EIT-guided PEEP on lung compliance in randomized clinical trials vs. non-randomized studies pooled (MD) = 2.43 (95% CI - 0.39 to 5.26), indicating a trend towards improvement. A reduction in mortality rate (259 patients, relative risk (RR) = 0.64, 95% CI [0.45, 0.91]) was associated with modest improvements in compliance and driving pressure in three studies.
CONCLUSIONS: EIT facilitates real-time, individualized PEEP adjustments, improving respiratory system mechanics. Integration of EIT as a guiding tool in mechanical ventilation holds potential benefits in preventing ventilator-induced lung injury. Larger-scale studies are essential to validate and optimize EIT\'s clinical utility in ARDS management.

OBJECTIVE: To explore if the pressure-controlled ventilation (PCV) and pressure-controlled ventilation-volume guaranteed (PCV-VG) modes are superior to volume-controlled ventilation (VCV) in optimizing intraoperative respiratory mechanics in infants and young children in the prone position.
METHODS: A single-center prospective randomized study.
METHODS: Children\'s Hospital, Zhejiang University School of Medicine.
METHODS: Pediatric patients aged 1 month to 3 years undergoing elective spinal cord detethering surgery.
METHODS: Patients were randomly allocated to the VCV group, PCV group and PCV-VG group. The target tidal volume (VT) was 8 mL/kg and the respiratory rate (RR) was adjusted to maintain a constant end tidal CO2.
METHODS: The primary outcome was intraoperative peak airway pressure (Ppeak). Secondary outcomes included other respiratory and ventilation variables, gas exchange values, serum lung injury biomarkers concentration, hemodynamic parameters and postoperative respiratory complications.
RESULTS: A total of 120 patients were included in the final analysis (40 in each group). The VCV group showed higher Ppeak at T2 (10 min after prone positioning) and T3 (30 min after prone positioning) than the PCV and PCV-VG groups (T2: P = 0.015 and P = 0.002, respectively; T3: P = 0.007 and P = 0.009, respectively). The prone-related decrease in dynamic compliance was prevented by PCV and PCV-VG ventilation modalities at T2 and T3 than by VCV (T2: P = 0.008 and P = 0.015, respectively; T3: P = 0.015 and P = 0.014, respectively). Additionally, there were no significant differences in other secondary outcomes among the three groups.
CONCLUSIONS: In infants and young children undergoing spinal cord detethering surgery in the prone position, PCV-VG may be a better ventilation mode due to its ability to mitigate the increase in Ppeak and decrease in Cdyn while maintaining consistent VT.

BACKGROUND: A significant reduction in regional cerebral oxygen saturation (rSO2) is commonly observed during one-lung ventilation (OLV), while positive end-expiratory pressure (PEEP) can improve oxygenation. We compared the effects of three different PEEP levels on rSO2, pulmonary oxygenation, and hemodynamics during OLV.
METHODS: Forty-three elderly patients who underwent thoracoscopic lobectomy were randomly assigned to one of six PEEP combinations which used a crossover design of 3 levels of PEEP-0 cmH2O, 5 cmH2O, and 10 cmH2O. The primary endpoint was rSO2 in patients receiving OLV 20 min after adjusting the PEEP. The secondary outcomes included hemodynamic and respiratory variables.
RESULTS: After exclusion, thirty-six patients (36.11% female; age range: 60-76 year) were assigned to six groups (n = 6 in each group). The rSO2 was highest at OLV(0) than at OLV(10) (difference, 2.889%; [95% CI, 0.573 to 5.204%]; p = 0.008). Arterial oxygen partial pressure (PaO2) was lowest at OLV(0) compared with OLV(5) (difference, -62.639 mmHg; [95% CI, -106.170 to -19.108 mmHg]; p = 0.005) or OLV(10) (difference, -73.389 mmHg; [95% CI, -117.852 to -28.925 mmHg]; p = 0.001), while peak airway pressure (Ppeak) was lower at OLV(0) (difference, -4.222 mmHg; [95% CI, -5.140 to -3.304 mmHg]; p < 0.001) and OLV(5) (difference, -3.139 mmHg; [95% CI, -4.110 to -2.167 mmHg]; p < 0.001) than at OLV(10).
CONCLUSIONS: PEEP with 10 cmH2O makes rSO2 decrease compared with 0 cmH2O. Applying PEEP with 5 cmH2O during OLV in elderly patients can improve oxygenation and maintain high rSO2 levels, without significantly increasing peak airway pressure compared to not using PEEP.
BACKGROUND: Chinese Clinical Trial Registry ChiCTR2200060112 on 19 May 2022.

OBJECTIVE: To investigate the clinical practicability of positive end-expiratory pressure (PEEP) titrated by lung stretch index (SI) in patients with acute respiratory distress syndrome (ARDS).
METHODS: A parallel randomized controlled trial was conducted. Patients with moderate to severe ARDS who required mechanical ventilation admitted to the department of critical care medicine of General Hospital of the Yangtze River Shipping from August 2022 to February 2023 were enrolled. They were randomly divide into SI guided PEEP titration group (SI group) and pressure-volume curve (P-V curve) inspiratory low inflection point (LIP) guided PEEP titration group (LIP group). All patients were ventilated in a supine position after admission, with the head of the bed raised by 30 degree angle. The primary disease was actively treated, prone position ventilation for 12 h/d, and lung protective ventilation strategies such as controlled lung expansion were used for lung recruitment. On this basis, mechanical ventilation parameters were titrated with SI in the SI group; the LIP group titrated mechanical ventilation parameters with P-V curve inspiratory LIP+2 cmH2O (1 cmH2O≈0.098 kPa). The oxygenation index (PaO2/FiO2), and respiratory mechanics indicators such as lung dynamic compliance (Cdyn), peak airway pressure (Pip) were monitored before recruitment maneuver and after 1, 3, and 5 days of treatment. The therapeutic effect of the two groups was compared.
RESULTS: There were 41 patients in the SI group and 40 patients in the LIP group. There was no significant difference in general information such as gender, age, and disease type between the two groups. The mechanical ventilation time and the length of intensive care unit (ICU) stay in the SI group were significantly shorter than those in the LIP group (days: 9.47±3.36 vs. 14.68±5.52, 22.27±4.68 vs. 27.57±9.52, both P < 0.05). Although the 28-day mortality of the SI group was lower than that of the LIP group, the difference was not statistically significant [19.5% (8/41) vs. 35.0% (14/40), P > 0.05]. On the fifth day, the PaO2/FiO2 was higher in SI group [mmHg (1 mmHg≈0.133 kPa): 225.57±47.85 vs. 198.32±31.59, P < 0.05], the Cdyn was higher in SI group (mL/cmH2O: 47.39±6.71 vs. 35.88±5.35, P < 0.01), the Pip was lower in SI group (mmHg: 35.85±5.77 vs. 43.87±6.68, P < 0.05). The Kaplan-Meier survival curve showed no statistically significant difference in the 28 days cumulative survival rate between the two groups (Log-Rank: χ 2 = 2.348, P = 0.125).
CONCLUSIONS: The application of SI titration with PEEP in the treatment of ARDS patients may improve their prognosis.

暂无摘要。

OBJECTIVE: To explore a simple method for measuring the dynamic intrinsic positive end-expiratory pressure (PEEPi) during invasive mechanical ventilation.
METHODS: A 60-year-old male patient was admitted to the critical care medicine department of Dongying People\'s Hospital in September 2020. He underwent invasive mechanical ventilation treatment for respiratory failure due to head and chest trauma, and incomplete expiratory flow occurred during the treatment. The expiratory flow-time curve of this patient was served as the research object. The expiratory flow-time curve of the patient was observed, the start time of exhalation was taken as T0, the time before the initiation of inspiratory action (inspiratory force) was taken as T1, and the time when expiratory flow was reduced to zero by inspiratory drive (inspiratory force continued) was taken as T2. Taking T1 as the starting point, the follow-up tracing line was drawn according to the evolution trending of the natural expiratory curve before the T1 point, until the expiratory flow reached to 0, which was called T3 point. According to the time phase, the intrapulmonary pressure at the time just from expiratory to inspiratory (T1 point) was called PEEPi1. When the expiratory flow was reduced to 0 (T2 point), the intrapulmonary pressure with the inhaling power being removed hypothetically was called PEEPi2. And it was equal to positive end-expiratory pressure (PEEP) set in the ventilator at T3 point. The area under the expiratory flow-time curve (expiratory volume) between T0 and T1 was called S1. And it was S2 between T0 and T2, S3 between T0 and T3. After sedation, in the volume controlled ventilation mode, approximately one-third of the tidal volume was selected, and the static compliance of patient\'s respiratory system called \"C\" was measured using the inspiratory pause method. PEEPi1 and PEEP2 were calculated according to the formula \"C = ΔV/ΔP\". Here, ΔV was the change in alveolar volume during a certain period of time, and ΔP represented the change in intrapulmonary pressure during the same time period. This estimation method had obtained a National Invention Patent of China (ZL 2020 1 0391736.1).
RESULTS: (1) PEEPi1: according to the formula \"C = ΔV/ΔP\", the expiratory volume span from T1 to T3 was \"S3-S1\", and the intrapulmonary pressure decreased span was \"PEEPi1-PEEP\". So, C = (S3-S1)/(PEEPi1-PEEP), PEEPi1 = PEEP+(S3-S1)/C. (2)PEEPi2: the expiratory volume span from T2 to T3 was \"S3-S2\", and the intrapulmonary pressure decreased span was \"PEEPi2-PEEP\". So, C = (S3-S2)/(PEEPi2-PEEP), PEEPi2 = PEEP+(S3-S2)/C.
CONCLUSIONS: For patients with incomplete expiratory during invasive mechanical ventilation, the expiratory flow-time curve extension method can theoretically be used to estimate the dynamic PEEPi in real time.