Pressure safety range of barotrauma with lung recruitment manoeuvres: a randomised experimental study in a healthy animal model

Lung recruitment mechanics: coalescing tissue strains with organ expansion

BACKGROUND

Recruitment maneuvers are used to prevent atelectasis, or partial lung collapse, and to help prevent ventilator induced lung injury. Recruitment techniques remain a topic of debate due to the possibility for damage as they necessitate higher transpulmonary pressures, which are associated with inducing lung injury. We aim to evaluate and probe injury mechanisms and potential pressure inhomogeneities, expressed as heterogeneous lung recruitment and overdistension, by associating organ level compliances with continuous regional strains during the application of stepwise escalation contrasted with sustained inflation maneuvers.

METHODS

An established breathing mimicry electromechanical system integrated with high spatio-temporal digital image correlation techniques coupled the global pressure-volume response of the lung with local deformations. Compliances, pressures, strains, heterogeneities and the expansion evolution pertaining to the inflation phase of two recruitment methods were quantified and contrasted.

RESULTS

Significant differences between the organ- and tissue-level responses of the sustained inflation versus escalation maneuver were found. The escalation maneuver exhibited greater starting compliance, whereas the sustained inflation showed increased inflation compliance. The localized strain distribution for the sustained inflation yielded increased 75th percentile strain, 90th percentile strain, and range at maximum inflation compared to the escalation maneuver.

CONCLUSIONS

Local and global findings indicate the escalation maneuver exhibits more homogeneous lung recruitment compared to sustained inflation. We also observe a correspondence between the significant organ-level compliance differences between the two maneuvers and the disparities observed in the evolutionary progression of localized strain distributions throughout inflation.

Anesthesia for Bronchoscopy-An Update

The field of interventional pulmonology has grown immensely and is increasingly recognized as a subspecialty. The new procedures introduced in the last decade pose unique challenges, and anesthesiologists need to readapt to their specific demands. In this review, we extensively discuss the pathophysiology, technical aspects, preprocedural preparation, anesthetic management, and postprocedural challenges of many new procedures such as navigational bronchoscopy, endobronchial valve deployment, and bronchial thermoplasty. Majority of these procedures are performed under general anesthesia with an endotracheal tube. Total intravenous anesthesia with rocuronium as a muscle relaxant seems to be the standard US practice. The easy availability and proven safety and efficacy of sugammadex as a reversal agent of rocuronium has decreased the need for high-dose remifentanil as an agent to avoid muscle relaxants. Additional research is available with regard to the utility of nebulized lidocaine and is discussed. Finally, two newer drugs administered for conscious sedation (typically without the need of an anesthesiologist) are likely to gain popularity in the future. Remimazolam is a new short-acting benzodiazepine with a relatively faster offset of clinical effects. Dexmedetomidine, a selective adrenergic agonist, is increasingly employed in bronchoscopy as a sedative during bronchoscopic procedures.

Pulmonary recruitment maneuver reduces the intensity of post-laparoscopic shoulder pain: a systematic review and meta-analysis

BACKGROUND

Post-laparoscopic shoulder pain (PLSP) is a common complication following laparoscopic surgeries. This meta-analysis aimed to investigate whether pulmonary recruitment maneuver (PRM) was beneficial to alleviated shoulder pain after laparoscopic procedures.

METHODS

We reviewed existing literature in the electronic database from the date of inception to January 31, 2022. The relevant RCTs were independently selected by two authors, after which data extraction, assessment of the risk of bias, and comparison of results.

RESULTS

This meta-analysis included 14 studies involving 1504 patients, among which 607 patients were offered pulmonary recruitment maneuver (PRM) alone or in combination with intraperitoneal saline instillation (IPSI), while 573 patients were treated with passive abdominal compression. The administration of PRM significantly decreased the post-laparoscopic shoulder pain score at 12 h (MD (95%CI) - 1.12(-1.57, - 0.66), n = 801, P < 0.001, I2 = 88%); 24 h (MD (95%CI) - 1.45(-1.74, - 1.16), n = 1180, P < 0.001, I2 = 78%) and at 48 h (MD (95%CI) - 0.97(-1.57, - 0.36), n = 780, P < 0.001, I2 = 85%). We observed high heterogeneity in the study and analyzed the sensitivity but failed to identify the cause of the heterogeneity, which may have resulted from the different methodologies and clinical factors in the included studies.

CONCLUSION

This systematic review and meta-analysis indicate that PRM can reduce the intensity of PLSP. More studies may be needed to explore the usefulness of PRM in more laparoscopic operations besides gynecological surgeries and determine the optimal pressure of PRM or its appropriate combination with other measures. The results of this meta-analysis should be interpreted with caution owing to the high heterogeneity between the analyzed studies.

Safety and efficacy evaluation of the automatic stepwise recruitment maneuver in the neonatal population: An in vivo interventional study. Can anesthesiologists safely perform automatic lung recruitment maneuvers in neonates?

BACKGROUND

A new software has recently been incorporated in almost all new anesthesia machines to enable automatic lung recruitment maneuvers. To date, no studies have assessed the safety and efficacy of these automatic software programs in the neonatal population.

AIMS

We aimed to evaluate the safety and efficacy of the lung recruitment maneuver performed using the automatic stepwise recruitment maneuver software of the FLOW-i 4.3 Anesthesia System^® in a healthy and live neonatal model.

METHODS

Eight male newborn piglets were included in the study. The lung recruitment maneuver was performed in pressure-controlled ventilation with a constant driving pressure (15 cmH₂ O) in a stepwise increasing positive end-expiratory pressure (PEEP) model. The target peak inspiratory pressure (PIP) was 30 cmH₂ O and PEEP was 15 cmH₂ O. The maneuver lasted for 39 seconds. The hemodynamic variables were monitored using the PICCO^® system. The following respiratory parameters were monitored: oxygen saturation, fraction of inspired oxygen, partial pressure of oxygen and carbon dioxide in the arterial blood, end-tidal carbon dioxide pressure, PIP, plateau pressure, PEEP, static compliance (C_stat ), and dynamic compliance (C_dyn ). Safety was evaluated by assessing the accuracy of the software, need for not interrupting the maneuver, hemodynamic stability, and absence of adverse respiratory events with the lung recruitment maneuver. Efficacy was evaluated by improvement in C_stat and C_dyn after performing the lung recruitment maneuver.

RESULTS

All lung recruitment maneuvers were safely performed as scheduled without any interruptions. No pneumothorax or other side effects were observed. Hemodynamic stability was maintained during the lung recruitment maneuver. We observed an improvement of 33% in C_dyn and 24% in C_stat after the maneuver.

CONCLUSIONS

The automatic stepwise recruitment maneuver software of the FLOW-i 4.3 Anesthesia System^® is safe and efficacious in a healthy neonatal model. We did not observe any adverse respiratory or hemodynamic events during the implementation of the lung recruitment maneuver in the pressure-controlled ventilation mode using a stepwise increasing PEEP (30/15 cmH₂ O) approach.

Respiratory and Hemodynamic Effects of Prophylactic Alveolar Recruitment During Liver Transplant: A Randomized Controlled Trial

OBJECTIVES

Prolonged surgical retraction may cause atelectasis. We aimed to recruit collapsed alveoli, stepwise, monitored by lung dynamic compliance and observe effects on arterial oxygenation and systemic and graft hemodynamics. Secondarily, we observed alveolar recruitment effects on postoperative mechanical ventilation, international normalized ratio, and pulmonary complications.

MATERIALS AND METHODS

For 58 recipients (1 excluded), randomized with optimal positive end-expiratory pressure (n = 28) versus control (fixed positive end-expiratory pressure, 5 cm H₂O; n = 29), alveolar recruitment was initiated (pressure-controlled ventilation guided by lung dynamic compliance) to identify optimal conditions. Ventilation shifted to volume-control mode with 0.4 fraction of inspired oxygen, 6 mL/kg tidal volume, and 1:2 inspiratory-to-expiratory ratio. Alveolar recruitment was repeated postretraction and at intensive care unit admission. Primary endpoints were changes in lung dynamic compliance, arterial oxygenation, and hemodynamics (cardiac output, invasive arterial and central venous pressures, graft portal and hepatic vein flows). Secondary endpoints were mechanical ventilation period and postoperative international normalized ratio, aspartate/alanine aminotransferases, lactate, and pulmonary complications.

RESULTS

Alveolar recruitment increased positive end-expiratory pressure, lung dynamic compliance, and arterial oxygenation (P < .01) and central venous pressure (P = .004), without effects on corrected flow time (P = .7). Cardiac output and invasive arterial pressure were stable with (P = .11) and without alveolar recruitment (P = .1), as were portal (P = .27) and hepatic vein flow (P = .30). Alveolar recruitment reduced postoperative pulmonary complications (n = 0/28 vs 8/29; P = .001), without reduction in postoperative mechanical ventilation period (P = .08). International normalization ratio, aspartate/alanine aminotransferases, and lactate were not different from control (P > .05).

CONCLUSIONS

Stepwise alveolar recruitment identified the optimal positive end-expiratory pressure to improve lung mechanics and oxygenation with minimal hemodynamic changes, without liver graft congestion/dysfunction, and was associated with significant reduction in postoperative pulmonary complications.

Low-pressure pulmonary recruitment maneuver: equal to or worse than moderate-pressure pulmonary recruitment maneuver in preventing postlaparoscopic shoulder pain? A randomized controlled trial of 72 patients

Introduction

The pulmonary recruitment maneuver (PRM) has emerged as an effective way of reducing post-laparoscopic shoulder pain (PLSP). However, the optimal lower pressure level for a PRM to reduce PLSP has not yet been investigated.

Aim

To compare the efficacy of the low-pressure PRM with moderate-pressure PRM in preventing PLSP.

Material and methods

Seventy-two ASA I-II patients who were scheduled for gynecologic LS for non-malignant conditions were enrolled in this study. Group 1 included patients who received the PRM at a maximum pressure of 30-40 cm H₂O in a semi-Fowler position and group 2 included patients who received the PRM at a maximum pressure of 15 cm H₂O in a semi-Fowler position. The primary outcome of the study was the difference in PLSP between the two groups.

Results

There were no significant differences in PLSP and wound pain VAS scores between patients receiving the PRM at 30 cm H₂O and 15 cm H₂O during postoperative pain monitoring (p < 0.05). The groups were also similar with respect to ambulation time (p = 0.215), length of hospital stay (p = 0.556) and the height of the pneumoperitoneum measured on chest X-ray (p = 0.151).

Conclusions

The low-pressure PRM (15 cm H₂O pressure) provides similar efficacy as the moderate-pressure PRM (30-40 cm H₂O) in terms of PLSP, wound pain, height of pneumoperitoneum, time of ambulation and length of hospital stay. We suggest that lower maximal inspiratory pressure of 15 cm H₂O might be preferred to avoid the potential complications of the PRM with higher pressures.

Effect of recumbency and body condition score on open-lung positive end-expiratory pressure and respiratory system compliance following a stepwise lung recruitment manoeuvre in healthy dogs during general anaesthesia

The aim was to assess the effects of recumbency and body condition score (BCS) on open-lung positive end-expiratory pressure (OL-PEEP) and quasistatic respiratory system compliance (Crs) following stepwise lung recruitment manoeuvre (RM) in healthy dogs under general anaesthesia. Thirty-four dogs were anaesthetised and mechanically ventilated (tidal volume of 10 mL/kg) without PEEP for 1 min (baseline). A stepwise RM was then performed and the individual OL-PEEP was subsequently applied. The Crs was registered at baseline and every 10-min for 50 min after RM. Dogs were classified into either dorsal or lateral recumbency groups, and as normal (score 4-5/9) or high (≥6/9) BCS groups. The OL-PEEP was higher in lateral than in dorsal recumbency (P = .002), but differences were not observed between normal and high BCS (P = .865). The Crs was increased from baseline at all time points after RM in all groups. The Crs did not differ between dorsally and laterally recumbent dogs at any time point. However, the baseline Crs was significantly lower in dogs with a high BCS than in those with a normal BCS (P < .001); therefore, the absolute change from baseline was considered when comparing Crs after the RM and it was similar in both BCS groups. In conclusion, in anaesthetised healthy dogs the OL-PEEP following RM was lower when dogs were positioned in dorsal than in lateral recumbency. The Crs after RM remained unchanged regardless of the dogs' recumbency. A stepwise RM followed by OL-PEEP could compensate for the potential negative impact of moderately increased BCS on Crs.

Comparative effects of open-lung positive end-expiratory pressure (PEEP) and fixed PEEP on respiratory system compliance in the isoflurane anaesthetised healthy dog

This study was performed to assess the effects of open-lung positive end-expiratory pressure (OL-PEEP) following stepwise recruitment manoeuvre (RM) and those of a fixed PEEP of 5 cm H₂O without previous RM on respiratory system compliance (Crs) and selected cardiovascular variables in healthy dogs under general anaesthesia. Forty-five healthy client-owned dogs undergoing surgery were anaesthetised and mechanically ventilated (tidal volume, VT = 10-12 mL/kg; PEEP = 0 cm H₂O) for 1 min (baseline) and randomly allocated into zero positive end-expiratory pressure (ZEEP), PEEP (5 cm H₂O) and OL-PEEP treatment groups. In the OL-PEEP group, a stepwise RM was performed and the individual OL-PEEP was subsequently applied. The Crs, heart rate (HR) and non-invasive mean arterial pressure (NIMAP) were registered at baseline and then every 10 min during 60 min. In the ZEEP group, Crs decreased from baseline. In the PEEP group, Crs was not different from either baseline or ZEEP group values. In the OL-PEEP group, Crs was higher than both baseline and ZEEP group values at all time points as well as of those in the PEEP group during at least 20 min after RM. There were no differences for HR and NIMAP between groups. A clinically relevant hypotension following RM was observed in 40% of dogs. Therefore, an individually set OL-PEEP following stepwise RM improved Crs in anaesthetised healthy dogs, although transient but clinically relevant hypotension was observed during RM in some dogs. Fixed PEEP of 5 cm H₂O without previous RM did not improve Crs, although it prevented it from decreasing.

Effects of breathing exercises using home-based positive pressure in the expiratory phase in patients with COPD

BACKGROUND

Patients with chronic obstructive pulmonary disease (COPD) commonly have higher intrinsic positive end-expiratory pressure (PEEPi). A breathing exercise programme strategy employing an appropriate PEEP may improve their pulmonary functional capacity, exercise tolerance and health-related quality of life. Breathing with an expiratory resistive load, which is a method of modulating spontaneous breathing against PEEPi, has not been fully studied in patients with COPD. The objective of this study was to investigate the role of changing spontaneous breathing in home-based conditions and regulating spontaneous breathing with breathing exercises in patients with COPD.

METHODS

This was a prospective randomised trial including 64 patients with a diagnosis of stage III or IV COPD. Patients were randomised into two groups: standard treatment and standard treatment combined with breathing exercise rehabilitation. The effects of the treatments on the COPD assessment test (CAT) score, 6-minute walk test (6MWT) results and pulmonary function were compared at 0, 6, 12 and 18 months within and between the two groups.

RESULTS

All outcomes showed no significant differences between the two groups at the beginning of the study, while the 6MWT and CAT scores exhibited clinically and statistically significant improvements (p<0.001) by the end of the study. At month 18, the change in the predicted percentage of forced expiratory volume in 1 s (FEV₁%pred) differed between the two groups (p<0.05). In addition, there were statistically significant differences in the 6MWT results, CAT scores and FEV₁%pred values between the baseline and month 18 (p<0.0001) in the intervention group.

CONCLUSIONS

Improvements in 6MWT results, pulmonary function and CAT scores are associated with a successful response to breathing against PEEPi in patients with COPD.

TRIAL REGISTRATION

This trial was registered at research registry.com (identifier research registry 4816).

Effect of Low-pressure Pulmonary Recruitment Maneuver on Postlaparoscopic Shoulder Pain: Randomized Controlled Trial

STUDY OBJECTIVE

Postlaparoscopic shoulder pain (PLSP) is effectively reduced by a pulmonary recruitment maneuver (PRM). The goal of this study is to assess the efficacy of a PRM using maximal inspiratory pressure of 30 cm H₂O, which is lower than previously studied pressure for reducing PLSP.

DESIGN

Randomized controlled trial.

SETTING

University hospital.

PATIENTS

Eighty-four patients who were undergoing elective gynecologic laparoscopy.

INTERVENTIONS

Patients were randomly assigned to the control (n = 42) or the PRM (n = 42) group.

MEASUREMENTS AND MAIN RESULTS

The primary outcome was the intensity of the shoulder pain using the visual analog scale (VAS). The VAS score of shoulder pain (median [interquartile range]) was significantly lower in the PRM group than in the control group at 24 hours (0 [0-0] vs 1.5 [0-4.0], p <.001) and 48 hours (0 [0-0] vs 1.0 [0-2.0], p <.001) after surgery. Other variables, including surgical pain score and vital signs, were similar between the 2 groups.

CONCLUSION

The PRM with 30 cm H₂O can be a simple method to reduce PLSP. Therefore, it would be helpful to perform the PRM with 30 cm H₂O routinely.

Recruitment manoeuvres in anaesthesia: How many more excuses are there not to use them?

Pulmonary recruitment manoeuvres (RM) are intended to reopen collapsed lung areas. RMs are present in nature as a physiological mechanism to get a newborn to open their lungs for the first time at birth, and we also use them, in our usual anaesthesiological clinical practice, after induction or during general anaesthesia when a patient is desaturated. However, there is much confusion in clinical practice regarding their safety, the best way to perform them, when to do them, in which patients they are indicated, and in those where they are totally contraindicated. There are important differences between RM in the patient with adult respiratory distress syndrome, and in a healthy patient during general anaesthesia. Our intention is to review, from a clinical and practical point of view, the use of RM, specifically in anaesthesia.

Positive end expiratory pressure titration guided by plateau pressure in chronic obstructive pulmonary disease patients

BACKGROUND

PEEP decreases intrinsic PEEP (PEEPi) in COPD patients. However, the best PEEP for someone with COPD is unclear.

METHODS

Ten COPD patients who received invasive mechanical ventilation were enrolled. Before PEEP titration, subjects were sedated and received mandatory ventilation. PEEP increased from 0 to 15 cmH₂ O. At each PEEP, peak pressure (Ppeak), plateau pressure (Pplat), PEEPi, and other variables were recorded. Increment of Pplat (ΔPplat) and PEEPi were plotted against PEEP applied. The best PEEP was recorded at the cross of the two curves.

RESULTS

From PEEP = 0 cmH₂ O to best PEEP, Ppeak (37.4 ± 5.1 vs. 38.4 ± 4.9 cmH₂ O) and Pplat (18.7 ± 3.3 vs. 20.4 ± 3.2 cmH₂ O) increased slightly, resistance (28.1 ± 5.6 vs. 26.6 ± 5.0 cmH₂ O/l/s) decreased slightly, and PEEPi (7.9 ± 2.3 vs. 1.5 ± 0.4 cmH₂ O) decreased sharply. Compliance, heart rate, blood pressure, and SpO₂ did not change. However, from best PEEP to PEEP = 15 cmH₂ O, Ppeak (38.4 ± 4.9 vs. 44.9 ± 4.3 cmH₂ O) and Pplat (20.4 ± 3.2 vs. 27.6 ± 3.3 cmH₂ O) increased sharply, and systolic blood pressure (116 ± 13 vs. 99 ± 14 mmHg) and compliance (46.1 ± 18.1 vs. 37.7 ± 10.6 mL/cmH₂ O) decreased sharply. At the same time, PEEPi (1.5 ± 0.4 vs. 0.7 ± 0.8 cmH₂ O) decreased only slightly, and resistance, heart rate, and SpO₂ did not change.

CONCLUSIONS

It is feasible to use Pplat as a simple way of determining the best PEEP in COPD patients.

Exogenous surfactant and alveolar recruitment in the treatment of the acute respiratory distress syndrome

OBJECTIVE

To investigate the effect of alveolar recruitment combined with surfactant administration on children with acute respiratory distress syndrome (ARDS).

MATERIAL AND METHODS

A prospective, randomized, controlled and sequential study was carried out. Group A (16 children) was treated with both the alveolar recruitment manoeuvres (ARM) and the administration of the surfactant every 8 h for 3 days; group B (15) received the usual treatment only. The alveolar recruitment was carried out by increasing positive end-expiratory pressure 2 by 2 cm H₂ O to improve the transcutaneous oxygen saturation values up to 88% and 90%. Demographic data, gasometric and ventilator parameters, chest radiography and 28-day mortality were evaluated.

RESULTS

There were no significant differences in baseline characteristics between groups. An hour after treatment, significant differences (P < 0.001) were observed in transcutaneous oxygen saturation (SaO₂ ; Group A: 94.1%, Group B: 89.9%), PaO₂ /FiO₂ (212.7 and 126.4) and oxygenation index (OI; 11.4 and 18.5). After 8 h, the differences in SaO₂ (Group A: 94.6%, Group B: 90.3%), PaO₂ /FiO₂ (225.8 and 126.9) and OI (10.8 and 18.4) were also significant (P < 0.001). From the fifth dose of the surfactant, the static compliance (P = 0.0034) and radiological images (P = 0.002) were more greatly improved in group A than in group B. Survival was significantly higher in group A (81.3%) than in group B (26.7%) (P = 0.006).

CONCLUSIONS

The combined treatment of surfactant administration and ARM resulted in a better oxygenation and survival in children with ARDS than when only recruitment was used.

Cardiorespiratory effects of recruitment maneuvers and positive end expiratory pressure in an experimental context of acute lung injury and pulmonary hypertension

Background

Recruitment maneuvers (RM) and positive end expiratory pressure (PEEP) are the cornerstone of the open lung strategy during ventilation, particularly during acute lung injury (ALI). However, these interventions may impact the pulmonary circulation and induce hemodynamic and respiratory effects, which in turn may be critical in case of pulmonary hypertension (PHT). We aimed to establish how ALI and PHT influence the cardiorespiratory effects of RM and PEEP.

Methods

Rabbits control or with monocrotaline-induced PHT were used. Forced oscillatory airway and tissue mechanics, effective lung volume (ELV), systemic and right ventricular hemodynamics and blood gas were assessed before and after RM, during baseline and following surfactant depletion by whole lung lavage.

Results

RM was more efficient in improving respiratory elastance and ELV in the surfactant-depleted lungs when PHT was concomitantly present. Moreover, the adverse changes in respiratory mechanics and ELV following ALI were lessened in the animals suffering from PHT.

Conclusions

During ventilation with open lung strategy, the role of PHT in conferring protection from the adverse respiratory consequences of ALI was evidenced. This finding advocates the safety of RM and PEEP in improving elastance and advancing lung reopening in the simultaneous presence of PHT and ALI.

Effects of different flow patterns and end-inspiratory pause on oxygenation and ventilation in newborn piglets: an experimental study

BACKGROUND

Historically, the elective ventilatory flow pattern for neonates has been decelerating flow (DF). Decelerating flow waveform has been suggested to improve gas exchange in the neonate when compared with square flow (SF) waveform by improving the ventilation perfusion. However, the superiority of DF compared with SF has not yet been demonstrated during ventilation in small infants. The aim of this study was to compare SF vs. DF, with or without end-inspiratory pause (EIP), in terms of oxygenation and ventilation in an experimental model of newborn piglets.

METHODS

The lungs of 12 newborn Landrace/LargeWhite crossbred piglets were ventilated with SF, DF, SF-EIP and DF-EIP. Tidal volume (VT), inspiratory to expiratory ratio (I/E), respiratory rate (RR), and FiO2 were keep constant during the study. In order to assure an open lung during the study while preventing alveolar collapse, a positive end-expiratory pressure (PEEP) of 6 cmH2O was applied after a single recruitment maneuver. Gas exchange, lung mechanics and hemodynamics were measured.

RESULTS

The inspiratory flow waveform had no effect on arterial oxygenation pressure (PaO2) (276 vs. 278 mmHg, p = 0.77), alveolar dead space to alveolar tidal volume (VDalv/VTalv) (0.21 vs. 0.19 ml, p = 0.33), mean airway pressure (Pawm) (13.1 vs. 14.0 cmH2O, p = 0.69) and compliance (Crs) (3.5 vs. 3.5 ml cmH2O(-1), p = 0.73) when comparing SF and DF. A short EIP (10%) did not produce changes in the results.

CONCLUSION

The present study showed that there are no differences between SF, DF, SF-EIP and DF-EIP in oxygenation, ventilation, lung mechanics, or hemodynamics in this experimental model of newborn piglets with healthy lungs.

Lung recruitment manoeuvres do not cause haemodynamic instability or oxidative stress but improve oxygenation and lung mechanics in a newborn animal model: an observational study

BACKGROUND

Lung recruitment manoeuvres in neonates during anaesthesia are not performed routinely due to concerns about causing barotrauma, haemodynamic instability and oxidative stress.

OBJECTIVE

To assess the influence of recruitment manoeuvres and positive end-expiratory pressure (PEEP) on haemodynamics, oxidative stress, oxygenation and lung mechanics.

DESIGN

A prospective experimental study.

SETTING

Experimental Unit, La Paz University Hospital, Madrid, Spain.

ANIMALS

Eight newborn piglets (<48 h) with healthy lungs under general anaesthesia.

INTERVENTIONS

The recruitment manoeuvres in pressure-controlled ventilation (PCV) were performed along with a constant driving pressure of 15 cmH2O. After the recruitment manoeuvres, PEEP was reduced in a stepwise fashion to find the maximal dynamic compliance step (maxCDyn-PEEP). Blood oxidative stress biomarkers (lipid peroxidation products, protein carbonyls, total glutathione, oxidised glutathione, reduced glutathione and activity of glutathione peroxidase) were analysed.

MAIN OUTCOME MEASURES

Haemodynamic parameters, arterial partial pressure of oxygen (paO2), tidal volume (Vt), dynamic compliance (Cdyn) and oxidative stress biomarkers were measured.

RESULTS

The recruitment manoeuvres did not induce barotrauma. Haemodynamic instability was not detected either in the maximum pressure step (overdistension step 5) or during the entire process. No substantial differences were observed in blood oxidative stress parameters analysed as compared with their baseline values (with 0 PEEP) or the values obtained 180 min after the onset of the recruitment manoeuvres (optimal PEEP). Significant maximal values were achieved in step 14 with an increase in paO2 (32.43 ± 8.48 vs. 40.39 ± 15.66 kPa; P = 0.037), Vt (47.75 ± 13.59 vs. 73.87 ± 13.56 ml; P = 0.006) and Cdyn (2.50 ± 0.64 vs. 4.75 ± 0.88 ml cmH2O; P < 0.001). Maximal dynamic compliance step (maxCdyn-PEEP) was 2 cmH2O.

CONCLUSION

Recruitment manoeuvres in PCV with a constant driving pressure are a well tolerated open-lung strategy in a healthy-lung neonatal animal model under general anaesthesia. The recruitment manoeuvres improve oxygenation parameters and lung mechanics and do not cause barotrauma, haemodynamic instability or oxidative stress.