Physiological effects of two driving pressure-based methods to set positive end-expiratory pressure during one lung ventilation

Effect of individualized end-inspiratory pause guided by driving pressure on respiratory mechanics during prone spinal surgery: a randomized controlled trial

Purpose

The prone position is commonly used in spinal surgery, but it can lead to decreased lung compliance and increased airway pressure. This study aimed to evaluate the effect of individualized end-inspiratory pause guided by driving pressure on respiratory mechanics in patients undergoing prone spinal surgery.

Methods

A randomized controlled trial was conducted from August to October 2023. Patients scheduled for elective prone spinal surgery were randomly assigned to either a study group, receiving individualized end-inspiratory pause, or a control group, receiving a fixed end-inspiratory pause (10% of total inspiratory time). Mechanical ventilation parameters, including tidal volume, plateau pressure, driving pressure, and peak pressure, were recorded at different time points. Arterial blood gases were collected at baseline and at specified intervals.

Results

Data from 36 subjects (18 in each group) were included in the final analysis. The study group exhibited a significant increase in respiratory system compliance (P < 0.05) and improved intraoperative oxygenation (P < 0.05). In addition, the individualized end-inspiratory pause significantly decreased plateau pressure (P < 0.05) and driving pressure (P < 0.05) compared to the control group.

Conclusion

The individualized end-inspiratory pause guided by driving pressure effectively optimized pulmonary compliance and improved oxygenation during prone spinal surgery. These findings suggest that this ventilation strategy may enhance respiratory mechanics and reduce the risk of postoperative pulmonary complications.

Effect of driving pressure-guided individualised positive end-expiratory pressure on postoperative atelectasis in patients with morbid obesity: study protocol of a randomised controlled trial

INTRODUCTION

Atelectasis is a common postoperative complication in patients with obesity, contributing to respiratory insufficiency, pneumonia and poor clinical outcomes. Studies have shown that driving pressure (DP)-guided individualised positive end-expiratory pressure can improve respiratory mechanics and oxygenation, while also reducing the incidence of atelectasis and other postoperative pulmonary complications (PPCs). However, the effect of this ventilation strategy on patients with morbid obesity remains unclear. The trial presented here aims to use lung ultrasound to evaluate the effect of DP-guided individualised positive end-expiratory pressure (PEEP) on postoperative atelectasis in patients with obesity undergoing bariatric surgery.

METHODS AND ANALYSIS

This single-centre, randomised, controlled, single-blind study will enrol 52 participants with morbid obesity scheduled for laparoscopic bariatric surgery from 1 March 2024, to 30 April 2025. They will be randomly assigned in a 1:1 ratio to one of two groups: (1) the DP group, where participants will receive dynamic individualised PEEP guided by DP and (2) the fixed PEEP group, where participants will receive a PEEP of 8 cmH2O. The primary outcome is the lung ultrasound score 30 minutes after extubation. Secondary outcomes include the lung ultrasound score on postoperative day 1, the incidence and severity of PPCs within 3 days after surgery, the intraoperative partial pressure of arterial oxygen, DP, static lung compliance, mechanical power, the incidence of hypotension during titration and the dosage of vasoactive drugs.

ETHICS AND DISSEMINATION

This study has been approved by the Ethics Committee of The First Affiliated Hospital of Shandong First Medical University (YXLL-KY-2023(144)). The trial results will be published in peer-reviewed journals and at conferences.

TRIAL REGISTRATION NUMBER

https://clinicaltrials.gov/; NCT06181279.

Individualized PEEP titration by lung compliance during one-lung ventilation: a meta-analysis

BACKGROUND

Despite the physiological advantages of positive end-expiratory pressure (PEEP), its optimal utilization during one-lung ventilation (OLV) remains uncertain. We aimed to investigate whether individualized PEEP titration by lung compliance is associated with a reduced risk of postoperative pulmonary complications during OLV.

METHODS

We searched PubMed, Embase, and the Cochrane Central Register of Controlled Trials until April 1, 2024, to identify published randomized controlled trials that compared individualized PEEP titration by lung compliance with fixed PEEP during OLV. The primary outcome was a composite of postoperative pulmonary complications. Secondary outcomes included clinical outcomes (pneumonia, atelectasis, ARDS, cardiovascular complications, mortality), respiratory mechanics, gas exchanges, and hemodynamic variables. Subgroup analyses were conducted for the primary outcome according to the PEEP titration method (dynamic compliance vs. driving pressure/static compliance, stepwise decremental vs. incremental strategy).

RESULTS

Ten trials involving 3426 patients were included. Compared with fixed PEEP, individualized PEEP titration by lung compliance was associated with reduced risk of a composite of postoperative pulmonary complications (eight trials, 3351 patients, risk ratio [RR] 0.55, 95% CI 0.38-0.78). Subgroup analyses suggested the association was evident in the subgroup with titration by dynamic compliance rather than driving pressure/static compliance and in the subgroup with PEEP titration by stepwise decremental but not stepwise incremental strategy. Individualized PEEP titration by lung compliance was also associated with a reduced risk of pneumonia (RR 0.71, 95% CI 0.52-0.96) and atelectasis (RR 0.63, 95% CI 0.45-0.88), higher dynamic compliance, PaO2, PaO2/FiO2, and lower driving pressure. The individualized and fixed PEEP groups did not differ in ARDS, cardiovascular complications, mortality, peak pressure, plateau pressure, PaCO2, heart rate, and mean arterial pressure.

CONCLUSIONS

Compared with fixed PEEP, individualized PEEP titration by lung compliance is associated with a reduced risk of postoperative pulmonary complications during OLV, especially in PEEP titration by dynamic compliance or stepwise decremental strategy. It improves respiratory mechanics and oxygenation with no difference in hemodynamic variables. Trial registration number ClinicalTrials.gov (PROSPERO No. CRD42024529980).

Electrical impedance tomography-guided positive end-expiratory pressure titration for perioperative oxygenation and postoperative pulmonary complications: A systematic review and meta-analysis

BACKGROUND

The electrical impedance tomography (EIT)-guided individual positive end-expiratory pressure (PEEP) approach is a noninvasive, radiation-free, and straightforward strategy. However, its validity to prevent postoperative complications remains unclear. To determine whether the EIT-guided PEEP titration in surgery has a higher oxygenation index and lower postoperative complications incidence in patients, we performed a meta-analysis to assess the efficacy. The study design is a systematic review and meta-analysis.

METHODS

Four databases (Cochrane, PubMed, Web of Science, and Embase) were searched from 2000 to November 2022 for this study. Randomized controlled trials of patients selected for general anesthesia were included. The main indicators of the study were oxygenation and postoperative pulmonary complications. Study quality was assessed using the Cochrane Risk and Bias Tool.

RESULTS

A total of 7 articles with 425 subjects were included and were eligible for analysis. Meta-analysis showed that patients had a higher oxygenation index (PaO2/FiO2) after EIT-guided individual PEEP titration compared with other modalities of PEEP titration (6 trials, 351 subjects, standardized mean check = 1.06, 95% confidence interval = 0.59-1.53). For subgroup analysis, the results were still statistically significant both in adult/elder groups and normal/obese groups. No significant advantage was found for the incidence of postoperative pulmonary complications between individual PEEP titration under EIT and other titration strategies (5 trials, 341 subjects, standardized mean check = 0.77, 95% confidence interval = 0.34-1.71). The same results were found in the subgroup analysis.

CONCLUSION

EIT-guided individual PEEP setting significantly improved perioperative oxygenation index compared with other modalities of PEEP ventilation strategies for patients, but no significant differences were found in the incidence of the postoperative pulmonary complications.

Association between thoracic epidural anesthesia and driving pressure in adult patients undergoing elective major upper abdominal surgery: a randomized controlled trial

BACKGROUND

Thoracic epidural anesthesia (TEA) is associated with a knowledge gap regarding its mechanisms in lung protection and reduction of postoperative pulmonary complications (PPCs). Driving pressure (ΔP), an alternative indicator of alveolar strain, is closely linked to reduced PPCs with lower ΔP values. We aim to investigate whether TEA contributes to lung protection by lowering ΔP during mechanical ventilation.

METHODS

In this prospective, randomized, patient and evaluator-blinded parallel study, adult patients scheduled for elective major upper abdominal surgery were assigned to either the TEA group with combined thoracic epidural anesthesia and general anesthesia (TEA-GA) (n = 30) or the control group with only general anesthesia (GA) (n = 30).

MEASUREMENTS

The primary outcome was the minimum ΔP determined based on positive end-expiratory pressure (PEEP) after intubation. Secondary outcomes included the incidence of PPCs within seven days, the minimum ΔP at various time points, blood gas analysis, intensive care unit (ICU) admission rates, length of hospital stay, and 30-day mortality rate.

RESULTS

The TEA group had a significantly lower minimum ΔP titrated based on PEEP compared to the control group (11.23 ± 2.19 cmH2O vs. 12.67 ± 2.70 cmH2O; P = 0.028). Multivariate linear regression analysis showed that intraoperative TEA application (compared with its absence; unstandardized beta coefficient (B) = -1.289; P = 0.008) significantly correlated with ΔP. The incidence of PPCs did not differ significantly between the two groups (8 of 30 [26.7%] vs. 12 of 30 [40%]; P = 0.273), but the incidence of atelectasis in the TEA group was significantly lower than in the control group (5 of 30 [16.7%] vs. 12 of 30 [40.7%]; P = 0.012). Multivariate logistic regression analysis indicated that ΔP was the only variable significantly associated with PPCs (Adjusted Odds Ratio [OR] = 2.190; 95% Confidence Interval [CI]: 1.300 to 3.689; P = 0.003).

CONCLUSION

Compared to GA, TEA-GA can reduce intraoperative ΔP in patients undergoing major upper abdominal surgery, especially those undergoing laparoscopic surgery. However, compared to GA combined with ΔP-guided ventilation, TEA-GA combined with ΔP-guided ventilation does not reduce the risk of PPCs. There was no significant difference in the total use of various vasoactive drugs between the two groups.

TRIAL REGISTRATION

This study was registered in the Chinese Clinical Trial Registry (registration number ChiCTR2300068778 date of registration February 28, 2023).

Effects of starting one lung ventilation and applying individualized PEEP right after patients are placed in lateral decubitus position on intraoperative oxygenation for patients undergoing thoracoscopic pulmonary lobectomy: study protocol for a randomized controlled trial

BACKGROUND

For patients receiving one lung ventilation in thoracic surgery, numerous studies have proved the superiority of lung protective ventilation of low tidal volume combined with recruitment maneuvers (RM) and individualized PEEP. However, RM may lead to overinflation which aggravates lung injury and intrapulmonary shunt. According to CT results, atelectasis usually forms in gravity dependent lung regions, regardless of body position. So, during anesthesia induction in supine position, atelectasis usually forms in the dorsal parts of lungs, however, when patients are turned into lateral decubitus position, collapsed lung tissue in the dorsal parts would reexpand, while atelectasis would slowly reappear in the lower flank of the lung. We hypothesize that applying sufficient PEEP without RM before the formation of atelectasis in the lower flank of the lung may beas effective to prevent atelectasis and thus improve oxygenation as applying PEEP with RM.

METHODS

A total of 84 patients scheduled for elective pulmonary lobe resection necessitating one lung ventilation will be recruited and randomized totwo parallel groups. For all patients, one lung ventilation is initiated the right after patients are turned into lateral decubitus position. For patients in the study group, individualized PEEP titration is started the moment one lung ventilation is started, while patients in the control group will receive a recruitment maneuver followed by individualized PEEP titration after initiation of one lung ventilation. The primary endpoint will be oxygenation index measured at T4. Secondary endpoints will include intrapulmonary shunt, respiratory mechanics, PPCs, and hemodynamic indicators.

DISCUSSION

Numerous previous studies compared the effects of individualized PEEP applied alone with that applied in combination with RM on oxygenation index, PPCs, intrapulmonary shunt and respiratory mechanics after atelectasis was formed in patients receiving one lung ventilation during thoracoscopic surgery. In this study, we will apply individualized PEEP before the formation of atelectasis while not performing RM in patients allocated to the study group, and then we're going to observe its effects on the aspects mentioned above. The results of this trial will provide a ventilation strategy that may be conductive to improving intraoperative oxygenation and avoiding the detrimental effects of RM for patients receiving one lung ventilation.

TRIAL REGISTRATION

www.Chictr.org.cn ChiCTR2400080682. Registered on February 5, 2024.

Intraoperative effects of an alveolar recruitment manoeuvre in patients undergoing laparoscopic colon surgery

INTRODUCTION

Pulmonary atelectasis is common in patients undergoing laparoscopic abdominal surgery under general anaesthesia, which increases the risk of perioperative respiratory complications. Alveolar recruitment manoeuvres (ARM) are used to open up the lung parenchyma with atelectasis, although the duration of their benefit has not been clearly established. The aim of this study was to determine the effectiveness of an ARM in laparoscopic colon surgery, the duration of response over time, and its haemodynamic impact.

METHODS

Twenty-five patients undergoing laparoscopic colon surgery were included. After anaesthetic induction and initiation of surgery with pneumoperitoneum, an ARM was performed, and then optimal PEEP determined. Respiratory mechanics and gas exchange variables, and haemodynamic parameters, were analysed before the manoeuvre and periodically over the following 90 min.

RESULTS

Three patients were excluded for surgical reasons. The alveolar arterial oxygen gradient went from 94.3 (62.3-117.8) mmHg before to 60.7 (29.6-91.0) mmHg after the manoeuvre (P < .05). This difference was maintained during the 90 min of the study. Dynamic compliance of the respiratory system went from 31.3 ml/cmH2O (26.1-39.2) before the manoeuvre to 46.1 ml/cmH2O (37.5-53.5) after the manoeuvre (P < .05). This difference was maintained for 60 min. No significant changes were identified in any of the haemodynamic variables studied.

CONCLUSION

In patients undergoing laparoscopic colon surgery, performing an intraoperative ARM improves the mechanics of the respiratory system and oxygenation, without associated haemodynamic compromise. The benefit of these manoeuvres lasts for at least one hour.

Association between driving pressure and postoperative pulmonary complications in patients undergoing lung resection surgery: A randomised clinical trial

BACKGROUND

It is uncertain whether an association exists for decreases in driving pressure and the occurrence of postoperative pulmonary complications (PPCs) in patients undergoing selective lung resection surgery. Thus, we designed this study to determine whether the positive end-expiratory pressure (PEEP) titration to the lowest driving pressure compared with conventional low PEEP level during one-lung ventilation (OLV) in patients undergoing selective lung resection surgery decreases PPCs.

METHODS

This single-centre, randomised trial approved by the Ethical Committee of the Sun Yat-Sen University Cancer Center involved patients who signed written consent. Patients were randomised to the PEEP titration to the lowest driving pressure group (n = 104), or to the conventional low level of PEEP group (n = 103), consisting a PEEP level of 4 cm H₂O during OLV. All patients received volume-controlled ventilation with a tidal volume of 6 mL/kg of predicted body weight. The primary outcome was defined as positive if 4 or more of eight Melbourne Group Scale (MGS) variables developed within the first 3 days after surgery. The incidence of major PPCs occurring during postoperative 7 days was also recorded.

RESULTS

Among 222 patients who were randomised, 207 (93%) completed the trial (109 men [53%]; mean age, 56.9 years). The primary outcome occurred in 4 of 104 patients (4%) in the PEEP titration to the lowest driving pressure group compared with 13 of 103 patients (13%) in the conventional low level of PEEP group (risk ratio, 0.32 [95% CI, 0.10-0.90]; P = 0.021).

CONCLUSIONS

Among patients undergoing selective lung surgery, intraoperative OLV with PEEP titration to the lowest driving pressure compared with conventional low PEEP level (4 cm H₂O) significantly reduced PPCs within the first 3 postoperative days, however, did not significantly reduce PPCs within the first 7 postoperative days.

Individualized positive end-expiratory pressure guided by respiratory mechanics during anesthesia for the prevention of postoperative pulmonary complications: a systematic review and meta-analysis

The optimization of positive end-expiratory pressure (PEEP) according to respiratory mechanics [driving pressure or respiratory system compliance (Crs)] is a simple and straightforward strategy. However, its validity to prevent postoperative pulmonary complications (PPCs) remains unclear. Here, we performed a meta-analysis to assess such efficacy. We searched PubMed, Embase, and the Cochrane Library to identify randomized controlled trials (RCTs) that compared personalized PEEP based on respiratory mechanics and constant PEEP to prevent PPCs in adults. The primary outcome was PPCs. Fourteen studies with 1105 patients were included. Compared with those who received constant PEEP, patients who received optimized PEEP exhibited a significant reduction in the incidence of PPCs (RR = 0.54, 95% CI 0.42 to 0.69). The results of commonly happened PPCs (pulmonary infections, hypoxemia, and atelectasis but not pleural effusion) also supported individualized PEEP group. Moreover, the application of PEEP based on respiratory mechanics improved intraoperative respiratory mechanics (driving pressure and Crs) and oxygenation. The PEEP titration method based on respiratory mechanics seems to work positively for lung protection in surgical patients undergoing general anesthesia.

Do we have the 'power' to 'drive' down the incidence of pulmonary complications after thoracic surgery

The concept, mechanisms, and physical and physiological determinants of ventilator-induced lung injury, as well as the influence of lung-protective ventilation strategies, are novel paradigms of modern intensive care and perioperative medicine. Driving pressure and mechanical power have emerged as meaningful and modifiable targets with specific relevance to thoracic anaesthesia and one-lung ventilation. The relationship between these factors and postoperative pulmonary complications remains complex because of the methodological design and outcome selection. Larger observational studies are required to better understand the characteristics of driving pressure and power in current practice of thoracic anaesthesia in order to design future trials in high-risk thoracic populations at risk of acute lung injury.

Effect of positive end-expiratory pressure on pulmonary compliance and pulmonary complications in patients undergoing robot-assisted laparoscopic radical prostatectomy: a randomized control trial

Background

To observe the effects of different positive end-expiratory pressure (PEEP) ventilation strategies on pulmonary compliance and complications in patients undergoing robotic-assisted laparoscopic prostate surgery.

Methods

A total of 120 patients with the American Society of Anesthesiologists Physical Status Class I or II who underwent elective robotic-assisted laparoscopic prostatectomy were enrolled. We randomized the patients divided into divided into three groups of 40 patients each: PEEP0, PEEP5, or PEEP10. Master Anesthetist used volume control ventilation intraoperatively with an intraoperative deep muscle relaxation strategy. Respiratory mechanics indexes were recorded at six time-points: 10 mimuts after anaesthesia induction, immediately after pneumoperitoneum establishment, 30 min, 60 min, 90 min, and at the end of pneumoperitoneum. Arterial blood gas analysis and oxygenation index calculation were performed 10 mimuts after anaesthesia induction, 60 mimuts after pneumoperitoneum, and after tracheal extubation. Postoperative pulmonary complications were also recorded.

Results

After pneumoperitoneum, peak inspiratory pressure (Ppeak), plateau pressure (Pplat), mean pressure (Pmean), driving pressure (ΔP), and airway resistance (Raw) increased significantly, and pulmonary compliance (Crs) decreased, persisting during pneumoperitoneum in all groups. Between immediately after pneumoperitoneum establishment, 30 min, 60 min, and 90 min, pulmonary compliance in the 10cmH2OPEEP group was higher than in the 5cmH2OPEEP (P < 0.05) and 0cmH2OPEEP groups(P < 0.05). The driving pressure (ΔP) immediately after pneumoperitoneum establishment, at 30 min, 60 min, and 90 min in the 10cmH2OPEEP group was lower than in the 5cmH2OPEEP (P < 0.05) and 0cmH2OPEEP groups (P < 0.05). Sixty min after pneumoperitoneum and tracheal extubation, the PaCO2 did not differ significantly among the three groups (P > 0.05). The oxygenation index (PaO2/FiO2) was higher in the PEEP5 group than in the PEEP0 and PEEP10 groups 60 min after pneumoperitoneum and after tracheal extubation, with a statistically significant difference (P < 0.05). In postoperative pulmonary complications, the incidence of atelectasis was higher in the PEEP0 group than in the PEEP5 and PEEP10 groups, with a statistically significant difference (p < 0.05).

Conclusion

The use of PEEP at 5cmH2O during RARP increases lung compliance, improves intraoperative oxygenation index and reduces postoperative atelectasis.

Trial registration

This study was registered in the China Clinical Trials Registry on May 30, 2020 (Registration No. ChiCTR2000033380).

Individualised positive end-expiratory pressure in abdominal surgery: a systematic review and meta-analysis

BACKGROUND

Individualised PEEP may optimise pulmonary compliance, thereby potentially mitigating lung injury. This meta-analysis aimed to determine the impact of individualised PEEP vs fixed PEEP during abdominal surgery on postoperative pulmonary outcomes.

METHODS

Medical databases (PubMed, Embase, Web of Science, ScienceDirect, Google Scholar, and the China National Knowledge Infrastructure) were searched for RCTs comparing fixed vs individualised PEEP. The composite primary outcome of pulmonary complications comprised hypoxaemia, atelectasis, pneumonia, and acute respiratory distress syndrome. Secondary outcomes included oxygenation (P_aO₂/FiO₂) and systemic inflammatory markers (interleukin-6 [IL-6] and club cell protein-16 [CC16]). We calculated risk ratios (RRs) and mean differences (MDs) with 95% confidence interval (CI) using DerSimonian and Laird random effects models. Cochrane risk-of-bias tool was applied.

RESULTS

Ten RCTs (n=1117 patients) met the criteria for inclusion, with six reporting the primary endpoint. Individualised PEEP reduced the incidence of overall pulmonary complications (141/412 [34.2%]) compared with 183/415 (44.1%) receiving fixed PEEP (RR 0.69 [95% CI: 0.51-0.93]; P=0.016; I²=43%). Risk-of-bias analysis did not alter these findings. Individualised PEEP reduced postoperative hypoxaemia (74/392 [18.9%]) compared with 110/395 (27.8%) participants receiving fixed PEEP (RR 0.68 [0.52-0.88]; P=0.003; I²=0%) but not postoperative atelectasis (RR 0.93 [0.81-1.07]; P=0.297; I²=0%). Individualised PEEP resulted in higher P_aO₂/FiO₂ (MD 20.8 mm Hg [4.6-36.9]; P=0.012; I²=80%) and reduced systemic inflammation (lower plasma IL-6 [MD -6.8 pg ml^-1; -11.9 to -1.7]; P=0.009; I²=6%; and CC16 levels [MD -6.2 ng ml^-1; -8.8 to -3.5]; P<0.001; I²=0%) at the end of surgery.

CONCLUSIONS

Individualised PEEP may reduce pulmonary complications, improve oxygenation, and reduce systemic inflammation after abdominal surgery.

CLINICAL TRIAL REGISTRATION

CRD42021277973.

An Updated Review of Driving-Pressure Guided Ventilation Strategy and Its Clinical Application

Traditional lung-protective ventilation strategies (LPVS) are currently used to reduce the incidence of postoperative pulmonary complications (PPCs), including low tidal volume (VT), positive end-expiratory pressure (PEEP), low inspiratory plateau pressure (Pplat), permissive hypercapnia, and recruitment maneuver (RM). However, a meta-analysis showed that high driving pressure was closely associated with the incidence of PPCs, but not with PEEP or VT, which led to the driving pressure-guided ventilation strategy. Some studies have proved that the driving pressure-guided ventilation strategy is superior to the traditional LPVS in reducing the incidence of PPCs. The purpose of this review is to present the current research progress and application of driving pressure-guided ventilation strategy.

Predictors of respiratory failure after thoracic surgery: a retrospective cohort study with comparison between lobar and sub-lobar resection

Objective

Only approximately 15% of patients with lung cancer are suitable for surgery and clinical postoperative outcomes vary. The aim of this study was to investigate variables associated with post-surgery respiratory failure in this patient cohort.

Methods

Patients who underwent surgery for lung cancer were retrospectively studied for respiratory function. All patients had undergone lung resection by a mini-thoracotomy approach. The study population was divided into two subgroups for comparison: lobectomy group, who underwent lobar resection; and sub-lobar resection group.

Results

A total of 85 patients were included, with a prevalence of lung cancer stage IA and adenocarcinoma histotype. Lobectomy (versus sub-lobar resection), the presence of chronic obstructive pulmonary disease (COPD), and a COPD assessment test (CAT) score >10, were all associated with an increased risk of respiratory failure. The partial pressure of arterial oxygen decreased more in the lobectomy group than in the sub-lobar resection group following surgery, with a significant postoperative between-group difference in values. Postoperative CAT scores were also better in the sub-lobar resection group.

Conclusions

Post-surgical variations in functional parameters were greater in the group treated by lobectomy. COPD, high CAT score and surgery type were associated with postoperative development of respiratory failure.

Effect of Driving Pressure-Oriented Ventilation on Patients Undergoing One-Lung Ventilation During Thoracic Surgery: A Systematic Review and Meta-Analysis

Background

Hypoxemia and fluctuations in respiratory mechanics parameters are common during one-lung ventilation (OLV) in thoracic surgery. Additionally, the incidence of postoperative pulmonary complications (PPC_S) in thoracic surgery is higher than that in other surgeries. Previous studies have demonstrated that driving pressure-oriented ventilation can reduce both mortality in patients with acute respiratory distress syndrome (ARDS) and the incidence of PPC_S in patients undergoing general anesthesia. Our aim was to determine whether driving pressure-oriented ventilation improves intraoperative physiology and outcomes in patients undergoing thoracic surgery.

Methods

We searched MEDLINE via PubMed, Embase, Cochrane, Web of Science, and ClinicalTrials.gov and performed a meta-analysis to compare the effects of driving pressure-oriented ventilation with other ventilation strategies on patients undergoing OLV. The primary outcome was the PaO₂/FiO₂ ratio (P/F ratio) during OLV. The secondary outcomes were the incidence of PPC_S during follow-up, compliance of the respiratory system during OLV, and mean arterial pressure during OLV.

Results

This review included seven studies, with a total of 640 patients. The PaO₂/FiO₂ ratio was higher during OLV in the driving pressure-oriented ventilation group (mean difference [MD]: 44.96; 95% confidence interval [CI], 24.22–65.70.32; I²: 58%; P < 0.0001). The incidence of PPC_S was lower (OR: 0.58; 95% CI, 0.34–0.99; I²: 0%; P = 0.04) and the compliance of the respiratory system was higher (MD: 6.15; 95% CI, 3.97–8.32; I²: 57%; P < 0.00001) in the driving pressure-oriented group during OLV. We did not find a significant difference in the mean arterial pressure between the two groups.

Conclusion

Driving pressure-oriented ventilation during OLV in patients undergoing thoracic surgery was associated with better perioperative oxygenation, fewer PPC_S, and improved compliance of the respiratory system.

Systematic Review Registration

PROSPERO, identifier: CRD42021297063.

What is new in respiratory monitoring?

This paper provides a review of a selection of papers published in the Journal of Clinical Monitoring and Computing in 2020 and 2021 highlighting what is new within the field of respiratory monitoring. Selected papers cover work in pulse oximetry monitoring, acoustic monitoring, respiratory system mechanics, monitoring during surgery, electrical impedance tomography, respiratory rate monitoring, lung ultrasound and detection of patient-ventilator asynchrony.

Relationship between Driving Pressure and Mortality in Ventilated Patients with Heart Failure: A Cohort Study

Background

Heart failure (HF) is a leading cause of mortality and morbidity worldwide, with an increasing incidence. Invasive ventilation is considered to be essential for patients with HF. Previous studies have shown that driving pressure is associated with mortality in acute respiratory distress syndrome (ARDS). However, the relationship between driving pressure and mortality has not yet been examined in ventilated patients with HF. We assessed the association of driving pressure and mortality in patients with HF.

Methods

We conducted a retrospective cohort study of invasive ventilated adult patients with HF from the Medical Information Mart for Intensive Care-III database. We used multivariable logistic regression models, a generalized additive model, and a two-piecewise linear regression model to show the effect of the average driving pressure within 24 h of intensive care unit admission on in-hospital mortality.

Results

Six hundred and thirty-two invasive ventilated patients with HF were enrolled. Driving pressure was independently associated with in-hospital mortality (odds ratio [OR], 1.12; 95% confidence interval [CI], 1.06–1.18; P < 0.001) after adjusted potential confounders. A nonlinear relationship was found between driving pressure and in-hospital mortality, which had a threshold around 14.27 cmH₂O. The effect sizes and CIs below and above the threshold were 0.89 (0.75 to 1.05) and 1.17 (1.07 to 1.30), respectively.

Conclusions

There was a nonlinear relationship between driving pressure and mortality in patients with HF who were ventilated for more than 48 h, and this relationship was associated with increased in-hospital mortality when the driving pressure was more than 14.27 cmH₂O.

Effect of pressure-controlled ventilation-volume guaranteed mode combined with individualized positive end-expiratory pressure on respiratory mechanics, oxygenation and lung injury in patients undergoing laparoscopic surgery in Trendelenburg position

The study aimed to investigate the efficacy of PCV-VG combined with individual PEEP during laparoscopic surgery in the Trendelenburg position. 120 patients were randomly divided into four groups: VF group (VCV plus 5cmH₂O PEEP), PF group (PCV-VG plus 5cmH₂O PEEP), VI group (VCV plus individual PEEP), and PI group (PCV-VG plus individual PEEP). P_mean, P_peak, Cdyn, PaO₂/FiO₂, V_D/V_T, A-aDO₂ and Qs/Qt were recorded at T₁ (15 min after the induction of anesthesia), T₂ (60 min after pneumoperitoneum), and T₃ (5 min at the end of anesthesia). The CC16 and IL-6 were measured at T₁ and T₃. Our results showed that the P_mean was increased in VI and PI group, and the P_peak was lower in PI group at T₂. At T₂ and T₃, the Cdyn of PI group was higher than that in other groups, and PaO₂/FiO₂ was increased in PI group compared with VF and VI group. At T₂ and T₃, A-aDO₂ of PI and PF group was reduced than that in other groups. The Qs/Qt was decreased in PI group compared with VF and VI group at T₂ and T₃. At T₂, V_D/V_T in PI group was decreased than other groups. At T₃, the concentration of CC16 in PI group was lower compared with other groups, and IL-6 level of PI group was decreased than that in VF and VI group. In conclusion, the patients who underwent laparoscopic surgery, PCV-VG combined with individual PEEP produced favorable lung mechanics and oxygenation, and thus reducing inflammatory response and lung injury.

Clinical Trial registry: chictr.org. identifier: ChiCTR-2100044928

Hemodynamic, renal and hormonal effects of lung protective ventilation during robot-assisted radical prostatectomy, analysis of secondary outcomes from a randomized controlled trial

Background

Lung protective ventilation with low tidal volume (TV) and increased positive end-expiratory pressure (PEEP) can have unfavorable effects on the cardiovascular system. We aimed to investigate whether lung protective ventilation has adverse impact on hemodynamic, renal and hormonal variables.

Methods

In this randomized, single-blinded, placebo-controlled study, 24 patients scheduled for robot-assisted radical prostatectomy were included. Patients were equally randomized to receive either ventilation with a TV of 6 ml/IBW and PEEP of 10 cm H₂O (LTV-h.PEEP) or ventilation with a TV of 10 ml/IBW and PEEP of 4 cm H₂O (HTV-l.PEEP). Before, during and after surgery, hemodynamic variables were measured, and blood and urine samples were collected. Blood samples were analyzed for plasma concentrations of electrolytes and vasoactive hormones. Urine samples were analyzed for excretions of electrolytes and markers of nephrotoxicity.

Results

Comparable variables were found among the two groups, except for significantly higher postoperative levels of plasma brain natriuretic peptide (p = 0.033), albumin excretion (p = 0.012) and excretion of epithelial sodium channel (p = 0.045) in the LTV-h.PEEP ventilation group compared to the HTV-l.PEEP ventilation group. In the combined cohort, we found a significant decrease in creatinine clearance (112.0 [83.4;126.7] ml/min at baseline vs. 45.1 [25.4;84.3] ml/min during surgery) and a significant increase in plasma concentrations of renin, angiotensin II, and aldosterone.

Conclusion

Lung protective ventilation was associated with minor adverse hemodynamic and renal effects postoperatively. All patients showed a substantial but transient reduction in renal function accompanied by activation of the renin-angiotensin-aldosterone system.

Trial registration

ClinicalTrials, NCT02551341. Registered 13 September 2015.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12871-021-01401-x.

Management of Intraoperative Mechanical Ventilation to Prevent Postoperative Complications after General Anesthesia: A Narrative Review

Mechanical ventilation (MV) is still necessary in many surgical procedures; nonetheless, intraoperative MV is not free from harmful effects. Protective ventilation strategies, which include the combination of low tidal volume and adequate positive end expiratory pressure (PEEP) levels, are usually adopted to minimize the ventilation-induced lung injury and to avoid post-operative pulmonary complications (PPCs). Even so, volutrauma and atelectrauma may co-exist at different levels of tidal volume and PEEP, and therefore, the physiological response to the MV settings should be monitored in each patient. A personalized perioperative approach is gaining relevance in the field of intraoperative MV; in particular, many efforts have been made to individualize PEEP, giving more emphasis on physiological and functional status to the whole body. In this review, we summarized the latest findings about the optimization of PEEP and intraoperative MV in different surgical settings. Starting from a physiological point of view, we described how to approach the individualized MV and monitor the effects of MV on lung function.