Intraoperative positive end-expiratory pressure evaluation using the intratidal compliance-volume profile

The association between intraoperative low driving pressure ventilation and perioperative healthcare-associated costs: A retrospective multicenter cohort study

STUDY OBJECTIVE

A low dynamic driving pressure during mechanical ventilation for general anesthesia has been associated with a lower risk of postoperative respiratory complications (PRC), a key driver of healthcare costs. It is, however, unclear whether maintaining low driving pressure is clinically relevant to measure and contain costs. We hypothesized that a lower dynamic driving pressure is associated with lower costs.

DESIGN

Multicenter retrospective cohort study.

SETTING

Two academic healthcare networks in New York and Massachusetts, USA.

PATIENTS

46,715 adult surgical patients undergoing general anesthesia for non-ambulatory (inpatient and same-day admission) surgery between 2016 and 2021.

INTERVENTIONS

The primary exposure was the median intraoperative dynamic driving pressure.

MEASUREMENTS

The primary outcome was direct perioperative healthcare-associated costs, which were matched with data from the Healthcare Cost and Utilization Project-National Inpatient Sample (HCUP-NIS) to report absolute differences in total costs in United States Dollars (US$). We assessed effect modification by patients' baseline risk of PRC (score for prediction of postoperative respiratory complications [SPORC] ≥ 7) and effect mediation by rates of PRC (including post-extubation saturation < 90%, re-intubation or non-invasive ventilation within 7 days) and other major complications.

MAIN RESULTS

The median intraoperative dynamic driving pressure was 17.2cmH2O (IQR 14.0-21.3cmH2O). In adjusted analyses, every 5cmH2O reduction in dynamic driving pressure was associated with a decrease of -0.7% in direct perioperative healthcare-associated costs (95%CI -1.3 to -0.1%; p = 0.020). When a dynamic driving pressure below 15cmH2O was maintained, -US$340 lower total perioperative healthcare-associated costs were observed (95%CI -US$546 to -US$132; p = 0.001). This association was limited to patients at high baseline risk of PRC (n = 4059; -US$1755;97.5%CI -US$2495 to -US$986; p < 0.001), where lower risks of PRC and other major complications mediated 10.7% and 7.2% of this association (p < 0.001 and p = 0.015, respectively).

CONCLUSIONS

Intraoperative mechanical ventilation targeting low dynamic driving pressures could be a relevant measure to reduce perioperative healthcare-associated costs in high-risk patients.

Anesthetic considerations in robotic surgery: a comprehensive review

Recent advancements have led to a rise, in the demand for surgical methods with robot-assisted procedures becoming increasingly popular for addressing the limitations of traditional laparoscopy. However, incorporating surgery involves making changes in the way patients are positioned and logistical planning, which can challenge conventional approaches to providing anesthesia care. Despite these obstacles robotic technology shows potential for bringing about improvements in therapy. Anesthesiologists play a role in ensuring safety and delivering high quality anesthesia care during robotic surgery. Having an understanding of the elements of robotic surgical systems is essential for adjusting anesthesia practices effectively. Keeping up to date with the developments in surgery is key to achieving optimal outcomes for patients. Effective collaboration between teams and anesthesiologists is essential for managing the complexities of anesthesia during surgery. By promoting communication and cooperation across disciplines healthcare professionals can enhance safety and results. In summary while the introduction of surgery presents challenges in anesthesia care it also offers opportunities for innovation and advancement. Anesthesiologists need to embrace these advancements adapt their practices accordingly and engage in education and collaboration to ensure the safe and successful integration of robotic technology, into surgical procedures ultimately improving patient care.

Intratidal compliance of the lung and the total respiratory system

OBJECTIVE

The worldwide rising quantity of surgeries and corresponding need of mechanical ventilation implicates a rising number of patients suffering from post-operative pulmonary complications. To prevent this risks, individual mechanics of the lung should be considered when setting the parameters of mechanical ventilation. Intratidal compliance analysis based on transpulmonal pressure would provide an estimate for individual lung mechanics. The downside of such measure however, is its invasiveness. Accurate measurement requires recording of the esophageal pressure as surrogate for the actual pleural pressure. Measuring pressure at the airway opening is considerably easier, but the resulting mechanics of the respiratory system may not represent the actual lung mechanics in a straight forward fashion.

APPROACH

In order to evaluate if the mechanics of the lungs are represented by those resulting from analysis of the mechanics of the respiratory system we determined intratidal dynamic compliance-volume profiles of both in 23 lung-healthy mechanically ventilated patients undergoing elective surgery. We also compared the accuracy of the compliance profiles resulting from analysis of the total breath with those resulting from the analysis of inspiration data only.

MAIN RESULTS

When the whole breath was analyzed 54.3%, and with only inspiration data 69.6% of compliance profiles of the respiratory system matched those of the lung. With both approaches profiles of the lung and the respiratory system matched or deviated by only one neighboring step (75% whole breath, 91.3% only inspiration), and never contradicted each other.

SIGNIFICANCE

Compliance profiles calculated from volume and pressure data of the respiratory system are an adequate surrogate for the compliance profiles of the lungs of lung-healthy patients. Therefore, invasive assessment of esophageal pressure for achievement of intrapleural pressure is unnecessary. The compliance profiles based on inspiratory data only appear more sensitive for indicating intratidal derecruitment than those based on data of the whole breath.

The global inhomogeneity index assessed by electrical impedance tomography overestimates PEEP requirement in patients with ARDS: an observational study

Background

Electrical impedance tomography (EIT) visualises alveolar overdistension and alveolar collapse and enables optimisation of ventilator settings by using the best balance between alveolar overdistension and collapse (ODCL). Besides, the global inhomogeneity index (GI), measured by EIT, may also be of added value in determining PEEP. Optimal PEEP is often determined based on the best dynamic compliance without EIT at the bedside. This study aimed to assess the effect of a PEEP trial on ODCL, GI and dynamic compliance in patients with and without ARDS. Secondly, PEEP levels from “optimal PEEP” approaches by ODCL, GI and dynamic compliance are compared.

Methods

In 2015–2016, we included patients with ARDS using postoperative cardiothoracic surgery patients as a reference group. A PEEP trial was performed with four consecutive incremental followed by four decremental PEEP steps of 2 cmH₂O. Primary outcomes at each step were GI, ODCL and best dynamic compliance. In addition, the agreement between ODCL, GI, and dynamic compliance was determined for the individual patient.

Results

Twenty-eight ARDS and 17 postoperative cardiothoracic surgery patients were included. The mean optimal PEEP, according to best compliance, was 10.3 (±2.9) cmH₂O in ARDS compared to 9.8 (±2.5) cmH₂O in cardiothoracic surgery patients. Optimal PEEP according to ODCL was 10.9 (±2.5) in ARDS and 9.6 (±1.6) in cardiothoracic surgery patients. Optimal PEEP according to GI was 17.1 (±3.9) in ARDS compared to 14.2 (±3.4) in cardiothoracic surgery patients.

Conclusions

Currently, no golden standard to titrate PEEP is available. We showed that when using the GI, PEEP requirements are higher compared to ODCL and best dynamic compliance during a PEEP trial in patients with and without ARDS.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12871-022-01801-7.

Effects of individualized positive end-expiratory pressure combined with recruitment maneuver on intraoperative ventilation during abdominal surgery: a systematic review and network meta-analysis of randomized controlled trials

Low tidal volume ventilation strategy may lead to atelectasis without proper positive end-expiratory pressure (PEEP) and recruitment maneuver (RM) settings. RM followed by individualized PEEP was a new method to optimize the intraoperative pulmonary function. We conducted a systematic review and network meta-analysis of randomized clinical trials to compare the effects of individualized PEEP + RM on intraoperative pulmonary function and hemodynamic with other PEEP and RM settings. The primary outcomes were intraoperative oxygenation index and dynamic compliance, while the secondary outcomes were intraoperative heart rate and mean arterial pressure. In total, we identified 15 clinical trials containing 36 randomized groups with 3634 participants. Ventilation strategies were divided into eight groups by four PEEP (L: low, M: moderate, H: high, and I: individualized) and two RM (yes or no) settings. The main results showed that IPEEP + RM group was superior to all other groups regarding to both oxygenation index and dynamic compliance. LPEEP group was inferior to LPEEP + RM, MPEEP, MPEEP + RM, and IPEEP + RM in terms of oxygenation index and LPEEP + RM, MPEEP, MPEEP + RM, HPEEP + RM, IPEEP, and IPEEP + RM in terms of dynamic compliance. All comparisons were similar for secondary outcomes. Our analysis suggested that individualized PEEP and RM may be the optimal low tidal volume ventilation strategy at present, while low PEEP without RM is not suggested.

Determining optimal positive end-expiratory pressure and tidal volume in children by intratidal compliance: a prospective observational study

BACKGROUND

Limited data exist regarding optimal intraoperative ventilation strategies for the paediatric population. This study aimed to determine the optimal combination of PEEP and tidal volume (V_T) based on intratidal compliance profiles in healthy young children undergoing general anaesthesia.

METHODS

During anaesthesia, infants (1 month-1 yr), toddlers (1-3 yr), and children (3-6 yr) were assigned serially to four ventilator settings: PEEP 8 cm H₂O/V_T 8 ml kg^-1 (PEEP8/V_T8), PEEP 10 cm H₂O/V_T 5 ml kg^-1 (PEEP10/V_T5), PEEP 10 cm H₂O/V_T 8 ml kg^-1 (PEEP10/V_T8), and PEEP 12 cm H₂O/V_T 5 ml kg^-1 (PEEP12/V_T5). The primary outcome was intratidal compliance profile, classified at each ventilator setting as horizontal (indicative of optimal alveolar ventilatory conditions), increasing, decreasing, or combinations of increasing/decreasing/horizontal compliance. Secondary outcomes were peak inspiratory, plateau, and driving pressures.

RESULTS

Intratidal compliance was measured in 15 infants, 13 toddlers, and 15 children (15/43 [35%] females). A horizontal compliance profile was most frequently observed with PEEP10/V_T5 (60.5%), compared with PEEP10/V_T8, PEEP8/V_T8, and PEEP12/V_T5 (23.3-34.9%; P<0.001). Decreasing compliance profiles were most frequent when V_T increased to 8 ml kg^-1, PEEP increased to 12 cm H₂O, or both. Plateau airway pressures were lower at PEEP8/V_T8 (16.9 cm H₂O [2.2]) and PEEP10/V_T5 (16.7 cm H₂O [1.7]), compared with PEEP10/V_T8 (19.5 cm H₂O [2.1]) and PEEP12/V_T5 (19.0 cm H₂O [2.0]; P<0.001). Driving pressure was lowest with PEEP10/V_T5 (4.6 cm H₂O), compared with other combinations (7.0 cm H₂O [2.0]-9.5 cm H₂O [2.1]; P<0.001).

CONCLUSIONS

V_T 5 ml kg^-1 combined with 10 cm H₂O PEEP may reduce atelectasis and overdistension, and minimise driving pressure in the majority of mechanically ventilated children <6 yr. The effect of these PEEP and V_T settings on postoperative pulmonary complications in children undergoing surgery requires further study.

CLINICAL TRIAL REGISTRATION

NCT04633720.

Optimal positive end-expiratory pressure to prevent anaesthesia-induced atelectasis in infants: A prospective, randomised, double-blind trial

BACKGROUND

Paediatric patients have a particularly high incidence of anaesthesia-induced atelectasis. Applying positive end-expiratory pressure (PEEP) with an alveolar recruitment manoeuvre has been substantially studied and adopted in adults; however, few studies have been conducted in children.

OBJECTIVE

We compared the effects of three levels of PEEP (3, 6 and 9 cmH2O) on anaesthesia-induced atelectasis measured by ultrasound in infants between 6 and 12 months of age who were undergoing general anaesthesia.

DESIGN

A prospective, randomised, double-blind trial.

SETTING

Department of Anaesthesia, single centre, South Korea, from May 2019 to March 2020.

PATIENTS

Children who were 6 to 12 months of age, whose American Society of Anesthesiologists (ASA) physical status was 1 or 2, whose height and weight were within two standard deviations of those of their peers, and who were scheduled for elective urological or general surgery were included in the study.

MAIN OUTCOME MEASURES

The primary outcome was the lung ultrasound score at the end of the procedure. The secondary outcomes included dynamic compliance, peak inspiratory pressure, driving pressure, cardiac index, mean arterial pressure and heart rate before and after applying PEEP.

RESULTS

The mean lung ultrasound score at the end of operation was 12.8 at PEEP 6 cmH2O and 12.1 at PEEP 9 cmH2O. Both were significantly lower than 18.4 at PEEP 3 cmH2O (P = 0.0002 and 0.00003, respectively). However, there was no significant difference between the scores of PEEP 6 cmH2O and PEEP 9 cmH2O. The Δ cardiac index (the cardiac index after PEEP - the cardiac index at 3 cmH2O of PEEP) was comparable among the three groups.

CONCLUSION

To reduce anaesthesia-induced atelectasis measured by ultrasound in healthy infants undergoing low abdominal, genitourinary or superficial regional operations, 6 cmH2O of PEEP was more effective than 3 cmH2O. PEEP of 9 cmH2O was comparable with 6 cmH2O.

TRIAL REGISTRATION

ClinicalTrials.gov identifier NCT03969173.

Protective mechanical ventilation with optimal PEEP during RARP improves oxygenation and pulmonary indexes

BACKGROUND

This trial aimed to evaluate the effects of a protective ventilation strategy on oxygenation/pulmonary indexes in patients undergoing robot-assisted radical prostatectomy (RARP) in the steep Trendelenburg position.

METHODS

In phase 1, the most optimal positive end-expiratory pressure (PEEP) was determined in 25 patients at 11 cmH₂O. In phase 2, 64 patients were randomized to the traditional ventilation group with tidal volume (VT) of 9 ml/kg of predicted body weight (PBW) and the protective ventilation group with VT of 7 ml/kg of PBW with optimal PEEP and recruitment maneuvers (RMs). The primary endpoint was the intraoperative and postoperative PaO₂/FiO₂. The secondary endpoints were the PaCO₂, SpO₂, modified clinical pulmonary infection score (mCPIS), and the rate of complications in the postoperative period.

RESULTS

Compared with controls, PaO₂/FiO₂ in the protective group increased after the second RM (P=0.018), and the difference remained until postoperative day 3 (P=0.043). PaCO₂ showed transient accumulation in the protective group after the first RM (T2), but this phenomenon disappeared with time. SpO₂ in the protective group was significantly higher during the first three postoperative days. Lung compliance was significantly improved after the second RM in the protective group (P=0.025). The mCPIS was lower in the protective group on postoperative day 3 (0.59 (1.09) vs. 1.46 (1.27), P=0.010).

CONCLUSION

A protective ventilation strategy with lower VT combined with optimal PEEP and RMs could improve oxygenation and reduce mCPIS in patients undergoing RARP.

TRIAL REGISTRATION

ChiCTR ChiCTR1800015626 . Registered on 12 April 2018.

Using NSQIP Data to Reduce Institutional Postoperative Pneumonia Rates in Non-ICU Patients: A Plan-Do-Study-Act Approach

BACKGROUND

The American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) is a program designed to measure and improve surgical care quality. In 2015, the study institution formed a multidisciplinary team to address the poor adult postoperative pneumonia performance (worst decile).

STUDY DESIGN

The study institution is a 450+ bed tertiary care center that performs 12,000+ surgical procedures annually. From January 2016 to December 2019, the institution abstracted surgical cases and assigned postoperative pneumonia as a complication per the NSQIP operations manual. Using a plan-do-study-act approach, a multidisciplinary postoperative pneumonia prevention team implemented initiatives regarding incentive spirometry education, anesthetic optimization, early mobility, and oral care. The team measured the initiatives' success by analyzing semiannual reports (SAR) provided by the ACS NSQIP and regional adjusted percentile rankings provided by the Georgia Surgical Quality Collaborative (GSQC).

RESULTS

The 2015 SAR postoperative pneumonia rate was 4.20% (odds ratio [OR] 3.86, confidence interval [CI] 2.92-5.11). After project initiation, the postoperative pneumonia rates decreased for all NSQIP cases, from 2.51% (OR 2.67, CI 1.89-3.77) in 2016 to 2.08% (OR 2.61, CI 1.82-3.74) in 2017, to 0.85% (OR 1.10, CI 0.69-1.75) in 2018, and then increased slightly to 1.14% (OR 1.27, CI 0.84-1.92) in 2019. The institution's adjusted percentile regional rank of participating regional ACS NSQIP hospitals' postoperative pneumonia rate improved from 14/14 (July 2015-June 2016) to 6/14 (July 2018-June 2019).

CONCLUSIONS

The multidisciplinary postoperative pneumonia prevention team successfully decreased the postoperative pneumonia rate, therefore improving surgical patients' outcomes. Furthermore, this quality improvement project also saved valuable revenue for the hospital.

Dependency of respiratory system mechanics on positive end-expiratory pressure and recruitment maneuvers in lung healthy pediatric patients-A randomized crossover study

BACKGROUND

The lungs of pediatric patients are subjected to tidal derecruitment during mechanical ventilation and in contrast to adult patients this unfavorable condition cannot be resolved with small c increases. This raises the question if higher end-expiratory pressure increases or recruitment maneuvers may resolve tidal derecruitment in pediatric patients.

AIMS

We hypothesized that higher PEEP resolves tidal derecruitment in pediatric patients and that recruitment maneuvers between the pressure changes support the improvement of respiratory system mechanics.

METHODS

The effects of end-expiratory pressure changes from 3 to 7 cmH₂ O and vice versa without and with intermediate recruitment maneuvers on respiratory system mechanics and regional ventilation were investigated in 57 mechanically ventilated pediatric patients. The intratidal respiratory system compliance was determined from volume and pressure data before and after PEEP changes and categorized to indicate tidal derecruitment.

RESULTS

Tidal derecruitment occurred comparably frequently at PEEP 3 cmH₂ O without (13 out of 14 cases) and with recruitment maneuver (14 out of 14 cases) and at PEEP 7 cmH₂ O without (13 out of 14 cases) and with recruitment maneuver (13 out of 15 cases).

CONCLUSIONS

We conclude that contrary to our hypothesis, PEEP up to 7 cmH₂ O is not sufficient to resolve tidal derecruitment and that recruitment maneuvers may be dispensable in mechanically ventilated pediatric patients.

Effect of individualized PEEP titration guided by intratidal compliance profile analysis on regional ventilation assessed by electrical impedance tomography - a randomized controlled trial

Background

The application of positive end-expiratory pressure (PEEP) may reduce dynamic strain during mechanical ventilation. Although numerous approaches for PEEP titration have been proposed, there is no accepted strategy for titrating optimal PEEP. By analyzing intratidal compliance profiles, PEEP may be individually titrated for patients.

Methods

After obtaining informed consent, 60 consecutive patients undergoing general anesthesia were randomly allocated to mechanical ventilation with PEEP 5 cmH₂O (control group) or PEEP individually titrated, guided by an analysis of the intratidal compliance profile (intervention group). The primary endpoint was the frequency of each nonlinear intratidal compliance (C_RS) profile of the respiratory system (horizontal, increasing, decreasing, and mixed). The secondary endpoints measured were respiratory mechanics, hemodynamic variables, and regional ventilation, which was assessed via electrical impedance tomography.

Results

The frequencies of the C_RS profiles were comparable between the groups. Besides PEEP [control: 5.0 (0.0), intervention: 5.8 (1.1) cmH₂O, p < 0.001], the respiratory and hemodynamic variables were comparable between the two groups. The compliance profile analysis showed no significant differences between the two groups. The loss of ventral and dorsal regional ventilation was higher in the control [ventral: 41.0 (16.3)%; dorsal: 25.9 (13.8)%] than in the intervention group [ventral: 29.3 (17.6)%; dorsal: 16.4 (12.7)%; p (ventral) = 0.039, p (dorsal) = 0.028].

Conclusions

Unfavorable compliance profiles indicating tidal derecruitment were found less often than in earlier studies. Individualized PEEP titration resulted in slightly higher PEEP. A slight global increase in aeration associated with this was indicated by regional gain and loss analysis. Differences in dorsal to ventral ventilation distribution were not found.

Trial registration

This clinical trial was registered at the German Register for Clinical Trials (DRKS00008924) on August 10, 2015.

Flow-controlled ventilation (FCV) improves regional ventilation in obese patients - a randomized controlled crossover trial

Background

In obese patients, high closing capacity and low functional residual capacity increase the risk for expiratory alveolar collapse. Constant expiratory flow, as provided by the new flow-controlled ventilation (FCV) mode, was shown to improve lung recruitment. We hypothesized that lung aeration and respiratory mechanics improve in obese patients during FCV.

Methods

We compared FCV and volume-controlled (VCV) ventilation in 23 obese patients in a randomized crossover setting. Starting with baseline measurements, ventilation settings were kept identical except for the ventilation mode related differences (VCV: inspiration to expiration ratio 1:2 with passive expiration, FCV: inspiration to expiration ratio 1:1 with active, linearized expiration). Primary endpoint of the study was the change of end-expiratory lung volume compared to baseline ventilation. Secondary endpoints were the change of mean lung volume, respiratory mechanics and hemodynamic variables.

Results

The loss of end-expiratory lung volume and mean lung volume compared to baseline was lower during FCV compared to VCV (end-expiratory lung volume: FCV, − 126 ± 207 ml; VCV, − 316 ± 254 ml; p < 0.001, mean lung volume: FCV, − 108.2 ± 198.6 ml; VCV, − 315.8 ± 252.1 ml; p < 0.001) and at comparable plateau pressure (baseline, 19.6 ± 3.7; VCV, 20.2 ± 3.4; FCV, 20.2 ± 3.8 cmH₂O; p = 0.441), mean tracheal pressure was higher (baseline, 13.1 ± 1.1; VCV, 12.9 ± 1.2; FCV, 14.8 ± 2.2 cmH₂O; p < 0.001). All other respiratory and hemodynamic variables were comparable between the ventilation modes.

Conclusions

This study demonstrates that, compared to VCV, FCV improves regional ventilation distribution of the lung at comparable PEEP, tidal volume, P_Plat and ventilation frequency. The increase in end-expiratory lung volume during FCV was probably caused by the increased mean tracheal pressure which can be attributed to the linearized expiratory pressure decline.

Trial registration

German Clinical Trials Register: DRKS00014925. Registered 12 July 2018.

Positive End-expiratory Pressure Alone Minimizes Atelectasis Formation in Nonabdominal Surgery: A Randomized Controlled Trial

BACKGROUND

Various methods for protective ventilation are increasingly being recommended for patients undergoing general anesthesia. However, the importance of each individual component is still unclear. In particular, the perioperative use of positive end-expiratory pressure (PEEP) remains controversial. The authors tested the hypothesis that PEEP alone would be sufficient to limit atelectasis formation during nonabdominal surgery.

METHODS

This was a randomized controlled evaluator-blinded study. Twenty-four healthy patients undergoing general anesthesia were randomized to receive either mechanical ventilation with PEEP 7 or 9 cm H2O depending on body mass index (n = 12) or zero PEEP (n = 12). No recruitment maneuvers were used. The primary outcome was atelectasis area as studied by computed tomography in a transverse scan near the diaphragm, at the end of surgery, before emergence. Oxygenation was evaluated by measuring blood gases and calculating the ratio of arterial oxygen partial pressure to inspired oxygen fraction (PaO2/FIO2 ratio).

RESULTS

At the end of surgery, the median (range) atelectasis area, expressed as percentage of the total lung area, was 1.8 (0.3 to 9.9) in the PEEP group and 4.6 (1.0 to 10.2) in the zero PEEP group. The difference in medians was 2.8% (95% CI, 1.7 to 5.7%; P = 0.002). Oxygenation and carbon dioxide elimination were maintained in the PEEP group, but both deteriorated in the zero PEEP group.

CONCLUSIONS

During nonabdominal surgery, adequate PEEP is sufficient to minimize atelectasis in healthy lungs and thereby maintain oxygenation. Thus, routine recruitment maneuvers seem unnecessary, and the authors suggest that they should only be utilized when clearly indicated.

VISUAL ABSTRACT

An online visual overview is available for this article at http://links.lww.com/ALN/B728.

Increasing positive end-expiratory pressure (re-)improves intraoperative respiratory mechanics and lung ventilation after prone positioning

BACKGROUND

Turning a patient prone, changes the respiratory mechanics and potentially the level of positive end-expiratory pressure (PEEP) that is necessary to prevent alveolar collapse. In this prospective clinical study we examined the impact of PEEP on the intratidal respiratory mechanics and regional lung aeration in the prone position. We hypothesized that a higher PEEP is required to maintain compliance and regional ventilation in the prone position.

METHODS

After ethical approval, 45 patients with healthy lungs undergoing lumbar spine surgery were examined in the supine position at PEEP 6 cm H2O and in the prone position at PEEP (6, 9 and 12 cm H2O). Dynamic compliance (CRS) and intratidal compliance-volume curves were determined and regional ventilation was measured using electrical impedance tomography. The compliance-volume curves were classified to indicate intratidal derecruitment, overdistension, or neither.

RESULTS

CRS did not differ between postures and PEEP levels (P>0.28). At a PEEP of 6 cm H2O a compliance-volume profile indicating neither derecruitment nor overdistension was observed in 38 supine, but only in 20 prone positioned patients (P<0.001). The latter increased to 33 and 37 (both P<0.001) when increasing PEEP to 9 and 12 cm H2O, respectively. Increasing PEEP from 6 to 9 cm H2O in the prone position increased peripheral ventilation significantly.

CONCLUSIONS

Respiratory system mechanics change substantially between supine and prone posture, which is not demonstrated in routine measurements. The intratidal compliance analysis suggests that in most patients a PEEP above commonly used settings is necessary to avoid alveolar collapse in the prone position.

CLINICAL TRIAL REGISTRATION

DRKS 00005692.

Cardiogenic oscillations to detect intratidal derecruitment and overdistension in a porcine model of healthy and atelectatic lungs

BACKGROUND

Low positive end-expiratory pressure (PEEP) can result in alveolar derecruitment, and high PEEP or high tidal volume (V_T) in lung overdistension. We investigated cardiogenic oscillations (COS) in the airway pressure signal to investigate whether these oscillations can assess unfavourable intratidal events. COS induce short instantaneous compliance increases within the pressure-volume curve, and consequently in the compliance-volume curve. We hypothesised that increases in COS-induced compliance reflect non-linear intratidal respiratory system mechanics.

METHODS

In mechanically ventilated anaesthetised pigs with healthy (n=13) or atelectatic (n=12) lungs, pressure-volume relationships and the ECG were acquired at a PEEP of 0, 5, 10, and 15 cm H₂O. During inspiration, the peak compliance of successive COS (C_COS) was compared with intratidal respiratory system compliance (C_RS) within incremental volume steps up to the full V_T of 12 ml kg^-1. We analysed whether C_COS variation corresponded with systolic arterial pressure variation.

RESULTS

C_COS-volume curves showed characteristic intratidal patterns depending on the PEEP level and on atelectasis. Increasing C_RS- or C_COS-volume patterns were associated with intratidal derecruitment with low PEEP, and decreasing patterns above 6 ml kg^-1 and high PEEP showed overdistension. C_COS was not associated with systolic arterial pressure variations.

CONCLUSIONS

Heartbeat-induced oscillations within the course of the inspiratory pressure-volume curve reflect non-linear intratidal respiratory system mechanics. The analysis of these cardiogenic oscillations can be used to detect intratidal derecruitment and overdistension and, hence, to guide PEEP and V_T settings that are optimal for respiratory system mechanics.

Joint consensus on abdominal robotic surgery and anesthesia from a task force of the SIAARTI and SIC

Minimally invasive surgical procedures have revolutionized the world of surgery in the past decades. While laparoscopy, the first minimally invasive surgical technique to be developed, is widely used and has been addressed by several guidelines and recommendations, the implementation of robotic-assisted surgery is still hindered by the lack of consensus documents that support healthcare professionals in the management of this novel surgical procedure. Here we summarize the available evidence and provide expert opinion aimed at improving the implementation and resolution of issues derived from robotic abdominal surgery procedures. A joint task force of Italian surgeons, anesthesiologists and clinical epidemiologists reviewed the available evidence on robotic abdominal surgery. Recommendations were graded according to the strength of evidence. Statements and recommendations are provided for general issues regarding robotic abdominal surgery, operating theatre organization, preoperative patient assessment and preparation, intraoperative management, and postoperative procedures and discharge. The consensus document provides evidence-based recommendations and expert statements aimed at improving the implementation and management of robotic abdominal surgery.

Management of One-lung Ventilation: Impact of Tidal Volume on Complications after Thoracic Surgery

BACKGROUND

The use of lung-protective ventilation (LPV) strategies may minimize iatrogenic lung injury in surgical patients. However, the identification of an ideal LPV strategy, particularly during one-lung ventilation (OLV), remains elusive. This study examines the role of ventilator management during OLV and its impact on clinical outcomes.

METHODS

Data were retrospectively collected from the hospital electronic medical record and the Society of Thoracic Surgery database for subjects undergoing thoracic surgery with OLV between 2012 and 2014. Mean tidal volume (VT) during two-lung ventilation and OLV and ventilator driving pressure (ΔP) (plateau pressure - positive end-expiratory pressure [PEEP]) were analyzed for the 1,019 cases that met the inclusion criteria. Associations between ventilator parameters and clinical outcomes were examined by multivariate linear regression.

RESULTS

After the initiation of OLV, 73.3, 43.3, 18.8, and 7.2% of patients received VT greater than 5, 6, 7, and 8 ml/kg predicted body weight, respectively. One hundred and eighty-four primary and 288 secondary outcome events were recorded. In multivariate logistic regression modeling, VT was inversely related to the incidence of respiratory complications (odds ratio, 0.837; 95% CI, 0.729 to 0.958), while ΔP predicted the development of major morbidity when modeled with VT (odds ratio, 1.034; 95% CI, 1.001 to 1.068).

CONCLUSIONS

Low VT per se (i.e., in the absence of sufficient PEEP) has not been unambiguously demonstrated to be beneficial. The authors found that a large proportion of patients continue to receive high VT during OLV and that VT was inversely related to the incidence of respiratory complications and major postoperative morbidity. While low (physiologically appropriate) VT is an important component of an LPV strategy for surgical patients during OLV, current evidence suggests that, without adequate PEEP, low VT does not prevent postoperative respiratory complications. Thus, use of physiologic VT may represent a necessary, but not independently sufficient, component of LPV.

Intraoperative compliance profiles and regional lung ventilation improve with increasing positive end-expiratory pressure

BACKGROUND

Anaesthesia and mechanical ventilation can lead to impaired lung. Intraoperative positive end-expiratory pressure (PEEP) should prevent intratidal recruitment/derecruitment without causing overdistension. The intratidal compliance profile indicates both unwanted phenomena. We hypothesized that a higher than usual PEEP improves the intratidal compliance and the regional lung ventilation of patients with healthy lungs.

METHODS

After ethics approval, 30 adult patients scheduled for limb surgery were investigated at PEEP 5, 7 and 9 cm H2 O during mechanical ventilation. We calculated the dynamic compliance of the respiratory system (CRS ) and the intratidal volume-dependent CRS curve. The CRS curve indicated intratidal recruitment/derecruitment and/or overdistension. Regional ventilation was measured using electrical impedance tomography.

RESULTS

At PEEP 5, 7 and 9 cm H2 O, intratidal recruitment/derecruitment was observed in 92%, 84% and 46% (P < 0.05) of the patients respectively. Increasing PEEP was associated with recruitment in the dorsal regions of the lungs (P < 0.001). At PEEP 9 cm H2 O, lung overdistension was indicated in two patients. With PEEP levels up to 9 cm H2 O, no significant effects on haemodynamic variables were found.

CONCLUSION

We conclude that in most patients, the often applied PEEP of 5 cm H2 O is insufficient to prevent intratidal recruitment/derecruitment and that few patients show overdistension at high PEEP levels. To establish optimal pressure-volume relationships in the respiratory system, the analysis of the individual intratidal compliance profiles could be a means for individualized perioperative PEEP titration.

Intratidal recruitment/derecruitment persists at low and moderate positive end-expiratory pressure in paediatric patients

In paediatric patients positive end-expiratory pressure (PEEP) is traditionally set lower than in adults. We investigated whether moderately higher PEEP improves respiratory mechanics and regional ventilation. Therefore, 40 children were mechanically ventilated with PEEP 2 and 5cmH₂O. Volume-dependent compliance profiles were analysed as a measure of intratidal recruitment/derecruitment. Regional ventilation was assessed using electrical impedance tomography. Mean compliance was 17.9±9.9mLcmH₂O^-1 (PEEP 2cmH₂O), and 19.0±10.9mLcmH₂O^-1 (PEEP 5 cmH₂O, p<0.001). Strong intratidal recruitment/derecruitment occurred in 40% of children at PEEP 2 cmH₂O, and 36% at PEEP 5 cmH₂O. Children showing strong recruitment/derecruitment were 33 (PEEP 2 cmH₂0) and 20 (PEEP 5 cmH₂0) months younger than children showing moderate recruitment/derecruitment. A higher PEEP improved peripheral ventilation. In conclusion, mechanically ventilated paediatric patients undergo intratidal recruitment/derecruitment which occurs more prominently in younger than in older children. A PEEP of 5cmH₂O does not fully prevent intratidal recruitment/derecruitment but homogenizes regional ventilation in comparison to 2cmH₂O.

Pneumoperitoneum deteriorates intratidal respiratory system mechanics: an observational study in lung-healthy patients

BACKGROUND

Pneumoperitoneum during laparoscopic surgery leads to atelectasis and impairment of oxygenation. Positive end-expiratory pressure (PEEP) is supposed to counteract atelectasis. We hypothesized that the derecruiting effects of pneumoperitoneum would deteriorate the intratidal compliance profile in patients undergoing laparoscopic surgery.

METHODS

In 30 adult patients scheduled for surgery with pneumoperitoneum, respiratory variables were measured during mechanical ventilation. We calculated the dynamic compliance of the respiratory system (C _RS) and the intratidal volume-dependent C _RS curve using the gliding-SLICE method. The C _RS curve was then classified in terms of indicating intratidal recruitment/derecruitment (increasing profile) and overdistension (decreasing profile). During the surgical interventions, the PEEP level was maintained nearly constant at 7 cm H₂O. Data are expressed as mean [confidence interval].

RESULTS

Baseline C _RS was 60 [54-67] mL cm H₂O^-1. Application of pneumoperitoneum decreased C _RS to 40 [37-43] mL cm H₂O^-1 which partially recovered to 54 [50-59] mL cm H₂O^-1 (P < 0.001) after removal but remained below the value measured before pneumoperitoneum (P < 0.001). Baseline compliance profiles indicated intratidal recruitment/derecruitment in 48 % patients. After induction of pneumoperitoneum, intratidal recruitment/derecruitment was indicated in 93 % patients (P < 0.01), and after removal intratidal recruitment/derecruitment was indicated in 59 % patients. Compliance profiles showing overdistension were not observed.

CONCLUSIONS

Analyses of the intratidal compliance profiles reveal that pneumoperitoneum during laparoscopic surgery causes intratidal recruitment/derecruitment which partly persists after its removal. The analysis of the intratidal volume-dependent C _RS profiles could be used to guide intraoperative PEEP adjustments during elevated intraabdominal pressure.