Comparison of the effect of two recruitment manoeuvres to conventional ventilation on lung atelectasis in paediatric laparoscopic surgery- a prospective randomised controlled trial.

BACKGROUND: There is a high incidence of pulmonary atelectasis during paediatric laparoscopic surgeries. The authors hypothesised that utilising a recruitment manoeuvre or using continuous positive airway pressure may prevent atelectasis compared to conventional ventilation. OBJECTIVE: The primary objective was to compare the degree of lung atelectasis diagnosed by lung ultrasound (LUS) using three different ventilation techniques in children undergoing laparoscopic surgeries. DESIGN: Randomised, prospective three-arm trial. SETTING: Single institute, tertiary care, teaching hospital. PATIENTS: Children of ASA PS 1 and 2 up to the age of 10 years undergoing laparoscopic surgery with pneumoperitoneum lasting for more than 30 min. INTERVENTION: Random allocation to one of the three study groups: CG group: Inspiratory pressure adjusted to achieve a TV of 5-8 ml/kg, PEEP of 5 cm H2O, respiratory rate adjusted to maintain end-tidal carbon dioxide (ETCO2) between 30-40 mm Hg with manual ventilation and no PEEP at induction. RM group: A recruitment manoeuvre of providing a constant pressure of 30 cm H2O for ten seconds following intubation was applied. A PEEP of 10 cm H2O was maintained intraoperatively. CPAP group: Intraoperative maintenance with PEEP 10 cm H2O with CPAP of 10 cm H2O at induction using mechanical ventilation was done. OUTCOME MEASURES: Lung atelectasis score at closure assessed by LUS. RESULTS: Post induction, LUS was comparable in all three groups. At the time of closure, the LUS for the RM group (8.6 ± 4.9) and the CPAP group (8.8 ± 6.8) were significantly lower (p < 0.05) than the CG group (13.3 ± 3.8). In CG and CPAP groups, the score at closure was significantly higher than post-induction. The PaO2/FiO2 ratio was significantly higher (p < 0.05) for the RM group (437.1 ± 44.9) and CPAP group (421.6 ± 57.5) than the CG group (361.3 ± 59.4) at the time of pneumoperitoneum. CONCLUSION: Application of a recruitment manoeuvre post-intubation or CPAP during induction and maintenance with a high PEEP leads to less atelectasis than conventional ventilation during laparoscopic surgery in paediatric patients. TRIAL REGISTRY: CTRI/2019/08/02058.

Effect of different lung recruitment strategies and airway device on oscillatory mechanics in children under general anaesthesia.

BACKGROUND: Atelectasis has been reported in 68 to 100% of children undergoing general anaesthesia, a phenomenon that persists into the recovery period. Children receiving recruitment manoeuvres have less atelectasis and fewer episodes of oxygen desaturation during emergence. The optimal type of recruitment manoeuvre is unclear and may be influenced by the airway device chosen. OBJECTIVE: We aimed to investigate the different effects on lung mechanics as assessed by the forced oscillation technique (FOT) utilising different recruitment strategies: repeated inflations vs. one sustained inflation and different airway devices, a supraglottic airway device vs. a cuffed tracheal tube. DESIGN: Pragmatic enrolment with randomisation to the recruitment strategy. SETTING: We conducted this single-centre trial between February 2020 and March 2022. PARTICIPANTS: Seventy healthy patients (53 boys) aged between 2 and 16 years undergoing general anaesthesia were included. INTERVENTIONS: Forced oscillations (5 Hz) were superimposed on the ventilator waveform using a customised system connected to the anaesthesia machine. Pressure and flow were measured at the inlet of the airway device and used to compute respiratory system resistance and reactance. Measurements were taken before and after recruitment, and again at the end of surgery. MAIN OUTCOME MEASURES: The primary endpoint measured is the change in respiratory reactance. RESULTS: Statistical analysis (linear model with recruitment strategy and airway device as factors) did not show any significant difference in resistance and reactance between before and after recruitment. Baseline reactance was the strongest predictor for a change in reactance after recruitment: prerecruitment Xrs decreased by mean (standard error) of 0.25 (0.068) cmH 2 O s l -1 per  1 cmH 2 O -1  s l -1 increase in baseline Xrs ( P  < 0.001). After correcting for baseline reactance, the change in reactance after recruitment was significantly lower for sustained inflation compared with repeated inflation by mean (standard error) 0.25 (0.101) cmH 2 O ( P  = 0.0166). CONCLUSION: Although there was no significant difference between airway devices, this study demonstrated more effective recruitment via repeated inflations than sustained inflation in anaesthetised children. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry: ACTRN12619001434189.

One-lung ventilation with fixed and variable tidal volumes on oxygenation and pulmonary outcomes: A randomized trial.

OBJECTIVE: Test the hypothesis that one-lung ventilation with variable tidal volume improves intraoperative oxygenation and reduces postoperative pulmonary complications after lung resection. BACKGROUND: Constant tidal volume and respiratory rate ventilation can lead to atelectasis. Animal and human ARDS studies indicate that oxygenation improves with variable tidal volumes. Since one-lung ventilation shares characteristics with ARDS, we tested the hypothesis that one-lung ventilation with variable tidal volume improves intraoperative oxygenation and reduces postoperative pulmonary complications after lung resection. DESIGN: Randomized trial. SETTING: Operating rooms and a post-anesthesia care unit. PATIENTS: Adults having elective open or video-assisted thoracoscopic lung resection surgery with general anesthesia were randomly assigned to intraoperative ventilation with fixed (n = 70) or with variable (n = 70) tidal volumes. INTERVENTIONS: Patients assigned to fixed ventilation had a tidal volume of 6 ml/kgPBW, whereas those assigned to variable ventilation had tidal volumes ranging from 6 ml/kg PBW ± 33% which varied randomly at 5-min intervals. MEASUREMENTS: The primary outcome was intraoperative oxygenation; secondary outcomes were postoperative pulmonary complications, mortality within 90 days of surgery, heart rate, and SpO2/FiO2 ratio. RESULTS: Data from 128 patients were analyzed with 65 assigned to fixed-tidal volume ventilation and 63 to variable-tidal volume ventilation. The time-weighted average PaO2 during one-lung ventilation was 176 (86) mmHg in patients ventilated with fixed-tidal volume and 147 (72) mmHg in the patients ventilated with variable-tidal volume, a difference that was statistically significant (p < 0.01) but less than our pre-defined clinically meaningful threshold of 50 mmHg. At least one composite complication occurred in 11 (17%) of patients ventilated with variable-tidal volume and in 17 (26%) of patients assigned to fixed-tidal volume ventilation, with a relative risk of 0.67 (95% CI 0.34-1.31, p = 0.24). Atelectasis in the ventilated lung was less common with variable-tidal volumes (4.7%) than fixed-tidal volumes (20%) in the initial three postoperative days, with a relative risk of 0.24 (95% CI 0.01-0.8, p = 0.02), but there were no significant late postoperative differences. No other secondary outcomes were both statistically significant and clinically meaningful. CONCLUSION: One-lung ventilation with variable tidal volume does not meaningfully improve intraoperative oxygenation, and does not reduce postoperative pulmonary complications.

Single-Lung Ventilation in Infants for Surgical Repair of Coarctation of The Aorta Without Cardiopulmonary Bypass.

OBJECTIVE: To investigate the effect of improving the operative field and postoperative atelectasis of single-lung ventilation (SLV) in the surgical repair of coarctation of the aorta (CoA) in infants without the use of cardiopulmonary bypass (CPB). METHODS: This was a retrospective cohort study. The clinical data of 28 infants (aged 1 to 4 months, weighing between 4.2 and 6 kg) who underwent surgical repair of CoA without CPB from January 2019 to May 2022 were analyzed. Fourteen infants received SLV with a bronchial blocker (Group S), and the other 14 infants received routine endotracheal intubation and bilateral lung ventilation (Group R). RESULTS: In comparison to Group R, Group S exhibited improved exposure of the operative field, a lower postoperative atelectasis score (P<0.001), reduced prevalence of hypoxemia (P=0.01), and shorter durations of operation, mechanical ventilation, and ICU stay (P=0.01, P<0.001, P=0.03). There was no difference in preoperative information or perioperative respiratory and circulatory indicators before SLV, 10 minutes after SLV, and 10 minutes after the end of SLV between the two groups (P>0.05). Intraoperative bleeding, intraoperative positive end-expiratory pressure (PEEP), and systolic pressure gradient across the coarctation after operation were also not different between the two groups (P>0.05). CONCLUSION: This study demonstrates that employing SLV with a bronchial blocker is consistent with enhanced operative field, reduced operation duration, lower prevalence of intraoperative hypoxemia, and fewer postoperative complications during the surgical repair of CoA in infants without the use of CPB.

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.

Ultrasound-guided versus conventional lung recruitment manoeuvres in thoracic surgery: a randomised controlled study.

Lung recruitment manoeuvres (RMs) during mechanical ventilation may reduce atelectasis, however, the optimal recruitment strategy for patients undergoing thoracic surgery remains unknown. Our study was designed to investigate whether ultrasound-guided lung RMs is superior to conventional RMs in reducing perioperative atelectasis during thoracic surgery with one-lung ventilation. We conducted a randomised controlled clinical trial from August 2022 to September 2022. Sixty patients scheduled for video-assisted thoracoscopic surgery (VATS) under general anaesthesia were enrolled. Subjects were randomly divided into the ultrasound-guided RMs group (manual inflation guided by lung ultrasound) or conventional RMs group (manual inflation with 30 cmH2O pressure). Lung ultrasound were performed at three predefined time points (1 min after anaesthetic induction; after RMs at the end of surgery; before discharge from postanesthesia care unit [PACU]). The primary outcome was lung ultrasound score before discharge from the PACU after extubation. In the early postoperative period, lung aeration deteriorated in both groups even after lung RMs. However, ultrasound-guided lung RMs had significantly lower lung ultrasound scores when compared with conventional RMs in bilateral lungs (2.0 [0.8-4.0] vs. 8.0 [3.8-10.3], P < 0.01) at the end of surgery, which remained before patients discharged from the PACU. Accordingly, the lower incidence of atelectasis was found in ultrasound-guided RMs group than in conventional RMs group (7% vs. 53%; P < 0.01) at the end of surgery. Ultrasound-guided RMs is superior to conventional RMs in improving lung aeration and reducing the incidence of lung atelectasis at early postoperative period in patients undergoing VATS. The study protocol was approved by the Institutional Review Board of the Fudan University Shanghai Cancer Center (No. 220,825,810; date of approval: August 5, 2022) and registered on Chinese Clinical Trial Registry (registration number: ChiCTR2200062761).

Effects of small-dose S-ketamine on anesthesia-induced atelectasis in patients undergoing general anesthesia accessed by lung ultrasound: study protocol for a randomized, double-blinded controlled trial.

BACKGROUND: Atelectasis after anesthesia induction in most patients undergoing general anesthesia may lead to postoperative pulmonary complications (PPCs) and affect postoperative outcomes. However, there is still no existing effective method used for the prevention of perioperative atelectasis. S-ketamine may prevent atelectasis due to airway smooth muscle relaxation and anti-inflammatory effects. Lung ultrasound is a portable and reliable bedside imaging technology for diagnosing anesthesia-induced atelectasis. The primary objective of this study is to assess whether a small dose of S-ketamine can reduce the incidence of atelectasis after intubation, and further investigate the effects of preventing the early formation of perioperative atelectasis and PPCs. METHODS: This is a single-institution, prospective, randomized controlled, parallel grouping, and double-blind study. From October 2020 to March 2022, 100 patients (18-60 years old) scheduled for elective surgery will be recruited from Beijing Tiantan Hospital, Capital Medical University, and randomly assigned to the S-ketamine group (group 1) and the normal saline group (group 2) at a ratio of 1:1. The label-masked agents will be administered 5 min before induction, and all patients will undergo a standardized general anesthesia protocol. Related data will be collected at three time points: after radial artery puncture (T1), 15 min after tracheal intubation (T2), and before extubation (T3). The primary outcome will be the total lung ultrasound scores (LUS) at T2. Secondary outcomes will include LUS in six chest regions at T2, total LUS at T3, arterial blood gas analysis results (PaCO2, PaO2) and PaO2/FiO2 at T2 and T3, and plateau pressure (Pplat) and dynamic lung compliance (Cdyn) at T2 and T3. The incidence of postoperative complications associated with S-ketamine and PPCs at 2 h and 24 h after surgery will be recorded. DISCUSSION: This trial aims to explore whether a simple and feasible application of S-ketamine before the induction of general anesthesia can prevent atelectasis. The results of this study may provide new ideas and direct clinical evidence for the prevention and treatment of perioperative pulmonary complications during anesthesia. TRIAL REGISTRATION: ClinicalTrials.gov NCT04745286. Registered on February 9, 2021.

Lung ultrasound-guided best positive end-expiratory pressure in neonatal anesthesia: a proposed randomized, controlled study.

BACKGROUND: Atelectasis is a common complication in neonatal anesthesia. Lung ultrasound (LUS) can be used intraoperatively to evaluate and recognize atelectatic lung areas. Hypotheses for the study are: (1) The use of LUS to guide choice of best positive end-expiratory pressure (PEEP) can lead to reduction of FiO2 to achieve same saturations of oxygen (SpO2). (2) In a less de-recruited lung, there will be less postoperative pulmonary complications. (3) Static respiratory system compliance could be different. (4) Hemodynamic parameters and amount of fluids infused or need for vasopressors intraoperatively could be different. METHODS: We propose a randomized controlled trial that compares standard PEEP settings with LUS-guided PEEP choice in patients under 2 months of age undergoing general anesthesia. RESULTS: The primary aim is to determine whether LUS-guided PEEP choice in neonatal anesthesia, compared to standard PEEP choice, can lead to reduction of FiO2 applied to the ventilatory setting in order to maintain same SpO2s. Secondary aims are to determine whether patients treated with LUS-guided PEEP will develop less postoperative pulmonary complications, will have a significant difference in hemodynamic parameters and amount of fluids or vasopressors infused, and in static respiratory system compliance. CONCLUSIONS: We expect a significant reduction of FiO2 in LUS-guided ventilation. IMPACT: Lung atelectasis is extremely common in neonatal anesthesia, because of the physiology of the neonatal lung and chest wall and leads to hypoxemia, being a lung area with a perfusion/ventilation mismatch. Raising inspired fraction of oxygen can overcome temporarily hypoxemia but oxygen is a toxic compound for newborns. Lung ultrasound (LUS) can detect atelectasis at bedside and be used to optimize ventilator settings including choice of positive end-expiratory pressure (PEEP). This randomized controlled trial (RCT) aims at demonstrating that LUS-guided choice of best PEEP during neonatal anesthesia can lead to reduction of inspired fractions of oxygen to keep same peripheral saturations SpO2.

Dexmedetomidine improves pulmonary outcomes in thoracic surgery under one-lung ventilation: A meta-analysis.

INTRODUCTION: Dexmedetomidine improves intrapulmonary shunt in thoracic surgery and minimizes inflammatory response during one-lung ventilation (OLV). However, it is unclear whether such benefits translate into less postoperative pulmonary complications (PPCs). Our objective was to determine the impact of dexmedetomidine on the incidence of PPCs after thoracic surgery. METHODS: Major databases were used to identify randomized trials that compared dexmedetomidine versus placebo during thoracic surgery in terms of PPCs. Our primary outcome was atelectasis within 7 days after surgery. Other specific PPCs included hypoxemia, pneumonia, and acute respiratory distress syndrome (ARDS). Secondary outcome included intraoperative respiratory mechanics (respiratory compliance [Cdyn]) and postoperative lung function (forced expiratory volume [FEV1]). Random effects models were used to estimate odds ratios (OR). RESULTS: Twelve randomized trials, including 365 patients in the dexmedetomidine group and 359 in the placebo group, were analyzed in this meta-analysis. Patients in the dexmedetomidine group were less likely to develop postoperative atelectasis (2.3% vs 6.8%, OR 0.42, 95%CI 0.18-0.95, P = 0.04; low certainty) and hypoxemia (3.4% vs 11.7%, OR 0.26, 95%CI 0.10-0.68, P = 0.01; moderate certainty) compared to the placebo group. The incidence of postoperative pneumonia (3.2% vs 5.8%, OR 0.57, 95%CI 0.25-1.26, P = 0.17; moderate certainty) or ARDS (0.9% vs 3.5%, OR 0.39, 95%CI 0.07-2.08, P = 0.27; moderate certainty) was comparable between groups. Both intraoperative Cdyn and postoperative FEV1 were higher among patients that received dexmedetomidine with a mean difference of 4.42 mL/cmH2O (95%CI 3.13-5.72) and 0.27 L (95%CI 0.12-0.41), respectively. CONCLUSION: Dexmedetomidine administration during thoracic surgery may potentially reduce the risk of postoperative atelectasis and hypoxemia. However, current evidence is insufficient to demonstrate an effect on pneumonia or ARDS.

Effect of incremental PEEP titration on postoperative pulmonary complications in patients undergoing emergency laparotomy: a randomized controlled trial.

Postoperative pulmonary complications (PPC) has a significant negative impact and are associated with increased length of hospital stay and cost of care. Emergency surgery is a well-established risk factor for PPC. Previous studies reported that personalized positive end-expiratory pressure (PEEP) might reduce postoperative atelectasis and postoperative pulmonary complications. N = 168 adult patients undergoing major emergency laparotomy under general anesthesia were recruited in this study. A minimum driving pressure based incremental PEEP titration was compared to a fixed PEEP of 5 cmH2O. The primary outcome was PPC up to postoperative day 7. The mean (standard deviation) of the recruited patients was 41.7(16.1)y, and 48.8% (82 of 168 patients) were female. The risk of PPC at postoperative day 7 was similar in both the study groups [Relative risk (RR) (95% Confidence interval, CI) 0.81 (0.58, 1.13); p = 0.25]. In addition, the incidence of intraoperative hypotension [p = 0.75], oxygen-free days at day 28 [p = 0.27], duration of postoperative hospital stay [p = 0.50], length of postoperative intensive care unit stay [p = 0.28], and in-hospital mortality [p = 0.38] were similar in two groups. Incidence of PPC was not reduced with the use of an individualized PEEP strategy based on lowest driving pressure. However, the incidence of hypotension and bradycardia was also not increased with titrated PEEP.Trial Registration: www.ctri.nic.in ; CTRI/2020/12/029765.

Positive end-expiratory pressure during one-lung ventilation for preventing atelectasis after video-assisted thoracoscopic surgery: a triple-arm, randomized controlled trial.

BACKGROUND: There is little evidence regarding the benefits of lung-protective ventilation in patients undergoing one-lung ventilation for thoracic surgery. This study aimed to determine the optimal level of positive end-expiratory pressure (PEEP) during one-lung ventilation for minimizing postoperative atelectasis through lung ultrasonography. METHODS: A total of 142 adult patients scheduled for video-assisted thoracoscopic surgery at Seoul National University Hospital between May 2019 and February 2020 were enrolled in this study. Patients were randomly assigned to different groups: 1) PEEP 3 cmH2O group; 2) PEEP 6 cmH2O group; and 3) PEEP 9 cmH2O group during one-lung ventilation. The lung ultrasound score was used to evaluate lung aeration using ultrasonography 1 hour after surgery. RESULTS: The 1-hour post-surgery lung ultrasound scores were 8.1±2.5, 6.8±2.6, and 5.9±2.6 in the PEEP 3, 6, and 9 cmH2O groups, respectively (P<0.001). The PEEP 3 cmH2O group showed significantly higher lung ultrasound scores than the PEEP 6 (adjusted P=0.034) and 9 cmH2O groups (adjusted P<0.001). The PaO2/FiO2 ratio measured at 10 minutes after the end of one-lung ventilation was significantly lower in the PEEP 3 cmH2O group (392 [331 to 469]) than the PEEP 6 cmH2O (458 [384 to 530], adjusted P=0.018) or PEEP 9 cmH2O groups (454 [374 to 522], adjusted P=0.016). CONCLUSIONS: Although the optimal level of PEEP during one-lung ventilation was not determined, the application of higher PEEP can prevent aeration loss in the ventilated lung after video-assisted thoracoscopic surgery under one-lung ventilation.

Pulmonary expansion manoeuvres compared to usual care on ventilatory mechanics, oxygenation, length of mechanical ventilation and hospital stay, extubation, atelectasis, and mortality of patients in mechanical ventilation: A randomized clinical trial.

Pulmonary expansion manoeuvres are therapeutic techniques used to prevent and reverse atelectasis; however, no randomized controlled trials have provided evidence supporting the use of this intervention among individuals on mechanical ventilation. OBJECTIVE: To evaluate the effects of chest compression-decompression and chest block manoeuvres compared to usual care among patients on mechanical ventilation. METHODS: The current study was a randomized clinical trial of adult subjects on mechanical ventilation for 12 to 48 hours. The control group received usual care (passive or active mobilization, manoeuvres for airway clearance and tracheal aspiration). The intervention group received usual care plus two lung expansion manoeuvres, i.e., chest decompression and chest block, while remaining on mechanical ventilation. Assessments were performed before and after usual care, immediately after the intervention and 30 minutes after the intervention. The primary outcome was static compliance. The secondary outcomes were the incidence of atelectasis, dynamic compliance, airway resistance, driving pressure, oxygenation, duration of mechanical ventilation, extubation success, length of hospital and ICU stay, and mortality. RESULTS: Fifty-one participants (67±15 years old, 53% men, 26 in the control group and 25 in the intervention group) were evaluated. No differences in static compliance were observed between groups (intervention minus control) before and after expansion manoeuvres [3.64 ml/cmH2O (95% CI: -0.36-7.65, p = 0.074)]. Peripheral oxygen saturation differed between groups before and after expansion manoeuvres, with more favourable outcome observed in the control group [-1.04% (95% CI: -1.94 --0.14), p = 0.027]. No differences were found in other outcomes. CONCLUSION: Chest compression-decompression and chest block manoeuvres did not improve ventilatory mechanics, the incidence of atelectasis, oxygenation, the duration of mechanical ventilation, the length of stay in the ICU and hospital, or mortality in individuals on mechanical ventilation. The findings of this study can be valuable for guiding evidence-based clinical practice and developing a therapeutic approach that provides real benefits for this population.

Effect of high-frequency oscillation on reduction of atelectasis in perioperative patients: a prospective randomized controlled study.

BACKGROUND: Atelectasis affects approximately 90% of anaesthetized patients, with laparoscopic surgery and pneumoperitoneum reported to exacerbate this condition. High-frequency oscillation therapy applies continuous positive pressure pulses to oscillate the airway, creating a pressure difference in small airways obstructed by secretions. This process helps reduce peak airway pressure, open small airways, and decrease atelectasis incidence, while also facilitating respiratory tract clearance. This study examines the efficacy of high-frequency oscillation on reduction of atelectasis in laparoscopic cholecystectomy (LC) patients under general anaesthesia, evaluated using lung ultrasound. METHODS: Sixty-four patients undergoing laparoscopic cholecystectomy were randomly divided into a control group and a high-frequency oscillation (HFO) group. Both groups underwent total intravenous anaesthesia under invasive arterial monitoring. The HFO group received a 10-minute continuous high-frequency oscillation therapy during surgery, while the control group received no intervention. Lung ultrasound evaluations were performed three times: five minutes post-intubation (T1), at the end of the surgery (T2), and before leaving the Post-Anaesthesia Care Unit (PACU; T3). Blood gas analysis was performed twice: prior to induction with no oxygen supply and before PACU discharge (oxygen supply off). RESULTS: The HFO group displayed a significantly lower incidence of atelectasis at T3 (57.5% vs. 90.3%, OR 6.88, 95%CI (1.74 to 27.24)) compared to the control group. Moreover, the HFO group's PaO2 levels remained consistent with baseline levels before PACU discharge, unlike the control group. Although there was no significant difference in LUS scores between the groups at T1 (8.56 ± 0.15 vs. 8.19 ± 0.18, p = 0.1090), the HFO group had considerably lower scores at T2 (13.41 ± 0.17 vs.7.59 ± 0.17, p < 0.01) and T3 (13.72 ± 0.14 vs.7.25 ± 0.21, p < 0.01). CONCLUSION: Our study indicates that high-frequency oscillation effectively reduces atelectasis in patients undergoing laparoscopic cholecystectomy. Additionally, it can mitigate the decline in oxygen partial pressure associated with atelectasis.

Individualised positive end-expiratory pressure titrated intra-operatively by electrical impedance tomography optimises pulmonary mechanics and reduces postoperative atelectasis: A randomised controlled trial.

BACKGROUND: A protective intra-operative lung ventilation strategy has been widely recommended for laparoscopic surgery. However, there is no consensus regarding the optimal level of positive end-expiratory pressure (PEEP) and its effects during pneumoperitoneum. Electrical impedance tomography (EIT) has recently been introduced as a bedside tool to monitor lung ventilation in real-time. OBJECTIVE: We hypothesised that individually titrated EIT-PEEP adjusted to the surgical intervention would improve respiratory mechanics during and after surgery. DESIGN: Randomised controlled trial. SETTING: First Medical Centre of Chinese PLA General Hospital, Beijing. PATIENTS: Seventy-five patients undergoing robotic-assisted laparoscopic hepatobiliary and pancreatic surgery under general anaesthesia. INTERVENTIONS: Patients were randomly assigned 2 : 1 to individualised EIT-titrated PEEP (PEEPEIT; n = 50) or traditional PEEP 5 cmH2O (PEEP5 cmH2O; n = 25). The PEEPEIT group received individually titrated EIT-PEEP during pneumoperitoneum. The PEEP5 cmH2O group received PEEP of 5 cmH2O during pneumoperitoneum. MAIN OUTCOME MEASURES: The primary outcome was respiratory system compliance during laparoscopic surgery. Secondary outcomes were individualised PEEP levels, oxygenation, respiratory and haemodynamic status, and occurrence of postoperative pulmonary complications (PPCs) within 7 days. RESULTS: Compared with PEEP5 cmH2O, patients who received PEEPEIT had higher respiratory system compliance (mean values during surgery of 44.3 ±â€Š11.3 vs. 31.9 ±â€Š6.6, ml cmH2O-1; P < 0.001), lower driving pressure (11.5 ±â€Š2.1 vs. 14.0 ±â€Š2.4 cmH2O; P < 0.001), better oxygenation (mean PaO2/FiO2 427.5 ±â€Š28.6 vs. 366.8 ±â€Š36.4; P = 0.003), and less postoperative atelectasis (19.4 ±â€Š1.6 vs. 46.3 ±â€Š14.8 g of lung tissue mass; P = 0.003). Haemodynamic values did not differ significantly between the groups. No adverse effects were observed during surgery. CONCLUSION: Individualised PEEP by EIT may improve intra-operative pulmonary mechanics and oxygenation without impairing haemodynamic stability, and decrease postoperative atelectasis. TRIAL REGISTRATION: Chinese Clinical Trial Registry (www.chictr.org.cn) identifier: ChiCTR2100045166.

Evaluation of the Effect of Pressure-Controlled Ventilation-Volume Guaranteed Mode vs. Volume-Controlled Ventilation Mode on Atelectasis in Patients Undergoing Laparoscopic Surgery: A Randomized Controlled Clinical Trial.

Background and Objectives: Laparoscopic surgery, which results in less bleeding, less postoperative pain, and better cosmetic results, may affect the lung dynamics via the pneumoperitoneum. After laparoscopic surgery, atelectasis develops. The primary aim of the present study is to demonstrate the effects of two different ventilation modes on the development of atelectasis using lung ultrasound, and the secondary outcomes include the plateau pressure, peak inspiratory pressure, and compliance differences between the groups. Materials and Methods: In this study, 62 participants aged 18-75 years undergoing laparoscopic cholecystectomy were enrolled. The patients were randomly assigned into two groups: the volume-controlled ventilation (VCV) group (group V) or the pressure-controlled-volume guaranteed ventilation (PCV-VG) group (group PV). The lung ultrasound score (LUS) was obtained thrice: prior to induction (T1), upon the patient's initial arrival in the recovery room (T2), and just before departing the recovery unit (T3). The hemodynamic data and mechanical ventilation parameters were recorded at different times intraoperatively. Results: The LUS score was similar between the groups at all the times. The change in the LUS score of the right lower anterior chest was statistically higher in the VCV group than the PCV group. The peak inspiratory pressure (PIP) was found to be statistically higher in the V group than the PV group five minutes after induction (T5) (20.84 ± 4.32 p = 0.021). The plateau pressure was found to be higher in the V group than the PV group at all times (after induction (Tind) 17.29 ± 5.53 p = 0.004, (T5) 17.77 ± 4.89 p = 0.001, after pneumoperitoneum (TPP) 19.71 ± 4.28 p = 0.002). Compliance was found to be statistically higher in the PV group than the V group at all times ((Tind) 48.87 ± 15.37 p = 0.011, (T5) 47.94 ± 13.71 p = 0.043, (TPP) 35.65 ± 6.90 p = 0.004). Before and after the pneumoperitoneum, the compliance was determined to be lower in the V group than the PV group, respectively (40.68 ± 13.91 p = 0.043, 30.77 ± 5.73 p = 0.004). Conclusions: LUS score was similar between groups at all times. The PCV-VG mode was superior to the VCV mode in providing optimal ventilatory pressures and maintaining high dynamic compliance in patients undergoing laparoscopic abdominal surgery.

Effects of 30% vs. 60% inspired oxygen fraction during mechanical ventilation on postoperative atelectasis: a randomised controlled trial.

BACKGROUND: There is the ongoing debate over the effect of inspired oxygen fraction (FiO2) during mechanical ventilation on postoperative atelectasis. We aimed to compare the effects of low (30%) and moderate (60%) FiO2 on postoperative atelectasis. The hypothesis of the study was that 30% FiO2 during mechanical ventilation could reduce postoperative atelectasis volume compared with 60% FiO2. METHODS: We performed a randomized controlled trial with 120 patients. Subjects were randomly assigned to receive 30% or 60% FiO2 during mechanical ventilation in a 1:1 ratio. The primary outcome was the percentage of postoperative atelectasis volume in the total lung measured using chest CT within 30 min after extubation. The secondary outcomes included different aeration region volumes, incidence of clinically significant atelectasis, and oxygenation index. RESULTS: In total, 113 subjects completed the trial, including 55 and 58 subjects in the 30% and 60% FiO2 groups, respectively. The percentage of the postoperative atelectasis volume in the 30% FiO2 group did not differ from that in the 60% FiO2 group. Furthermore, there was no significant difference in the atelectasis volume between the two groups after the missing data were imputed by multiple imputation. Additionally, there were no significant differences in the volumes of the over-aeration, normal-aeration, and poor-aeration regions between the groups. No significant differences in the incidence of clinically significant atelectasis or oxygenation index at the end of surgery were observed between the groups. CONCLUSIONS: Compared with 60% FiO2, the use of 30% FiO2 during mechanical ventilation does not reduce the postoperative atelectasis volume. TRIAL REGISTRATION: Chinese Clinical Trial Registry ( http://www.chictr.org.cn ). Identifier: ChiCTR1900021635. Date: 2 March 2019. Principal invetigator: Weidong Gu.

Arterial partial pressure of oxygen as a marker of airway closure does not correlate with the efficacy of pre-oxygenation: A prospective cohort study.

BACKGROUND: The prerequisites for the early formation of anaesthesia-related atelectasis are pre-oxygenation with its resulting high alveolar oxygen content, and airway closure. Airway closure increases with age, so it seems counterintuitive that atelectasis formation during anaesthesia does not. One proposed explanation is that pre-oxygenation is impaired in the elderly by airway closure present in the waking state. The extent of airway closure cannot be assessed at the bedside, but arterial partial pressure of oxygen ( Pa O 2 ) as a surrogate variable of the resulting ventilation to perfusion mismatch can. OBJECTIVE: The primary aim was to test the hypothesis that a decreased efficacy of pre-oxygenation, measured as the fraction of end-tidal oxygen (F E' O 2 ) after 3 min of pre-oxygenation, correlates with decreased Pa O 2 on room air. We also re-investigated the influence on F E' O 2 by age. DESIGN: Prospective observational study. SETTING: Two regional hospitals, Västerås and Köping County Hospitals, Västmanland, Sweden, between 30 October 2018 and 17 September 2021. PARTICIPANTS: We included 120 adults aged 40 to 79 years presenting for elective noncardiac surgery. INTERVENTION: An arterial blood gas was sampled before commencing pre-oxygenation. RESULTS: No linear correlation was found between F E' O 2 at 3 min and Pa O 2 or age (Pearson's r  = -0.038, P  = 0.684; and Pearson's r  = -0.113, P  = 0.223, respectively). The mean ±â€ŠSD F E' O 2 at 3 min for the population studied was 0.87 ±â€Š0.05. CONCLUSION: The lack of correlation between F E' O 2 at 3 min and Pa O 2 or age during pre-oxygenation has implications for further studies concerning the interaction between airway closure and atelectasis. After 3 min of pre-oxygenation, F E' O 2 , even in the elderly, indicated a high enough alveolar oxygen concentration to promote atelectasis after induction, therefore, it is still unclear why atelectasis formation diminishes after middle age. TRIAL REGISTRATION: ClinicalTrials.gov NCT03395782.

The effectiveness of postoperative rehabilitation interventions that include breathing exercises to prevent pulmonary atelectasis in lung cancer resection patients: a systematic review and meta-analysis.

BACKGROUND: The main aim of this systematic review was to determine the effectiveness of postoperative rehabilitation interventions that include breathing exercises as a component to prevent atelectasis in lung cancer resection patients. METHODS: In this review, we systematically and comprehensively searched the Cochrane Library, PubMed, EMBASE, and Web of Science in English and CNKI and Wanfang in Chinese from 2012 to 2022. The review included any randomized controlled trials focusing on the effectiveness of postoperative rehabilitation interventions that include breathing exercises to prevent pulmonary atelectasis in lung cancer patients. Participants who underwent anatomic pulmonary resection and received postoperative rehabilitation interventions that included breathing exercises as a component were included in this review. The study quality and risks of bias were measured with the GRADE and Cochrane Collaboration tools, and statistical analysis was performed utilizing RevMan 5.3 software. RESULTS: The incidence of atelectasis was significantly lower in the postoperative rehabilitation intervention group (OR = 0.35; 95% CI, 0.18 to 0.67; I2 = 0%; P = 0.67) than in the control group. The patients who underwent the postoperative rehabilitation program that included breathing exercises (intervention group) had higher forced vital capacity (FVC) scores (MD = 0.24; 95% CI, 0.07 to 0.41; I2 = 73%; P = 0.02), forced expiratory volume in one second (FEV1) scores (MD = 0.31; 95% CI, 0.03 to 0.60; I2 = 98%; P < 0.01) and FEV1/FVC ratios (MD = 9.09; 95% CI, 1.50 to 16.67; I2 = 94%; P < 0.01). CONCLUSION: Postoperative rehabilitation interventions that included breathing exercises decreased the incidence rate of atelectasis and improved lung function by increasing the FVC, FEV1, and FEV1/FVC ratio.

Individualized Positive End-expiratory Pressure on Postoperative Atelectasis in Patients with Obesity: A Randomized Controlled Clinical Trial.

BACKGROUND: Individualized positive end-expiratory pressure (PEEP) guided by dynamic compliance improves oxygenation and reduces postoperative atelectasis in nonobese patients. The authors hypothesized that dynamic compliance-guided PEEP could also reduce postoperative atelectasis in patients undergoing bariatric surgery. METHODS: Patients scheduled to undergo laparoscopic bariatric surgery were eligible. Dynamic compliance-guided PEEP titration was conducted in all patients using a downward approach. A recruitment maneuver (PEEP from 10 to 25 cm H2O at 5-cm H2O step every 30 s, with 15-cm H2O driving pressure) was conducted both before and after the titration. Patients were then randomized (1:1) to undergo surgery under dynamic compliance-guided PEEP (PEEP with highest dynamic compliance plus 2 cm H2O) or PEEP of 8 cm H2O. The primary outcome was postoperative atelectasis, as assessed with computed tomography at 60 to 90 min after extubation, and expressed as percentage to total lung tissue volume. Secondary outcomes included Pao2/inspiratory oxygen fraction (Fio2) and postoperative pulmonary complications. RESULTS: Forty patients (mean ± SD; 28 ± 7 yr of age; 25 females; average body mass index, 41.0 ± 4.7 kg/m2) were enrolled. Median PEEP with highest dynamic compliance during titration was 15 cm H2O (interquartile range, 13 to 17; range, 8 to 19) in the entire sample of 40 patients. The primary outcome of postoperative atelectasis (available in 19 patients in each group) was 13.1 ± 5.3% and 9.5 ± 4.3% in the PEEP of 8 cm H2O and dynamic compliance-guided PEEP groups, respectively (intergroup difference, 3.7%; 95% CI, 0.5 to 6.8%; P = 0.025). Pao2/Fio2 at 1 h after pneumoperitoneum was higher in the dynamic compliance-guided PEEP group (397 vs. 337 mmHg; group difference, 60; 95% CI, 9 to 111; P = 0.017) but did not differ between the two groups 30 min after extubation (359 vs. 375 mmHg; group difference, -17; 95% CI, -53 to 21; P = 0.183). The incidence of postoperative pulmonary complications was 4 of 20 in both groups. CONCLUSIONS: Postoperative atelectasis was lower in patients undergoing laparoscopic bariatric surgery under dynamic compliance-guided PEEP versus PEEP of 8 cm H2O. Postoperative Pao2/Fio2 did not differ between the two groups.