Electric impedance tomography and protective mechanical ventilation in elective robotic-assisted laparoscopy surgery with steep Trendelenburg position: a randomized controlled study

Setting positive end-expiratory pressure by using electrical impedance tomography

PURPOSE OF REVIEW

This review presents the principles and possibilities of setting positive end-expiratory pressure (PEEP) using electrical impedance tomography (EIT). It summarizes the major findings of recent studies where EIT was applied to monitor the effects of PEEP on regional lung function and to guide the selection of individualized PEEP setting.

RECENT FINDINGS

The most frequent approach of utilizing EIT for the assessment of PEEP effects and the PEEP setting during the time period from January 2022 till June 2023 was based on the analysis of pixel tidal impedance variation, typically acquired during stepwise incremental and/or decremental PEEP variation. The most common EIT parameters were the fraction of ventilation in various regions of interest, global inhomogeneity index, center of ventilation, silent spaces, and regional compliance of the respiratory system. The studies focused mainly on the spatial and less on the temporal distribution of ventilation. Contrast-enhanced EIT was applied in a few studies for the estimation of ventilation/perfusion matching.

SUMMARY

The availability of commercial EIT devices resulted in an increase in clinical studies using this bedside imaging technology in neonatal, pediatric and adult critically ill patients. The clinical interest in EIT became evident but the potential of this method in clinical decision-making still needs to be fully exploited.

Mechanical Ventilation, Past, Present, and Future

Mechanical ventilation (MV) has played a crucial role in the medical field, particularly in anesthesia and in critical care medicine (CCM) settings. MV has evolved significantly since its inception over 70 years ago and the future promises even more advanced technology. In the past, ventilation was provided manually, intermittently, and it was primarily used for resuscitation or as a last resort for patients with severe respiratory or cardiovascular failure. The earliest MV machines for prolonged ventilatory support and oxygenation were large and cumbersome. They required a significant amount of skills and expertise to operate. These early devices had limited capabilities, battery, power, safety features, alarms, and therefore these often caused harm to patients. Moreover, the physiology of MV was modified when mechanical ventilators moved from negative pressure to positive pressure mechanisms. Monitoring systems were also very limited and therefore the risks related to MV support were difficult to quantify, predict and timely detect for individual patients who were necessarily young with few comorbidities. Technology and devices designed to use tracheostomies versus endotracheal intubation evolved in the last century too and these are currently much more reliable. In the present, positive pressure MV is more sophisticated and widely used for extensive period of time. Modern ventilators use mostly positive pressure systems and are much smaller, more portable than their predecessors, and they are much easier to operate. They can also be programmed to provide different levels of support based on evolving physiological concepts allowing lung-protective ventilation. Monitoring systems are more sophisticated and knowledge related to the physiology of MV is improved. Patients are also more complex and elderly compared to the past. MV experts are informed about risks related to prolonged or aggressive ventilation modalities and settings. One of the most significant advances in MV has been protective lung ventilation, diaphragm protective ventilation including noninvasive ventilation (NIV). Health care professionals are familiar with the use of MV and in many countries, respiratory therapists have been trained for the exclusive purpose of providing safe and professional respiratory support to critically ill patients. Analgo-sedation drugs and techniques are improved, and more sedative drugs are available and this has an impact on recovery, weaning, and overall patients' outcome. Looking toward the future, MV is likely to continue to evolve and improve alongside monitoring techniques and sedatives. There is increasing precision in monitoring global "patient-ventilator" interactions: structure and analysis (asynchrony, desynchrony, etc). One area of development is the use of artificial intelligence (AI) in ventilator technology. AI can be used to monitor patients in real-time, and it can predict when a patient is likely to experience respiratory distress. This allows medical professionals to intervene before a crisis occurs, improving patient outcomes and reducing the need for emergency intervention. This specific area of development is intended as "personalized ventilation." It involves tailoring the ventilator settings to the individual patient, based on their physiology and the specific condition they are being treated for. This approach has the potential to improve patient outcomes by optimizing ventilation and reducing the risk of harm. In conclusion, MV has come a long way since its inception, and it continues to play a critical role in anesthesia and in CCM settings. Advances in technology have made MV safer, more effective, affordable, and more widely available. As technology continues to improve, more advanced and personalized MV will become available, leading to better patients' outcomes and quality of life for those in need.

Impact of ventilation strategies on pulmonary and cardiovascular complications in patients undergoing general anaesthesia for elective surgery: a systematic review and meta-analysis

BACKGROUND

Many RCTs have evaluated the influence of intraoperative tidal volume (tV), PEEP, and driving pressure on the occurrence of postoperative pulmonary complications, cardiovascular complications, and mortality in adult patients. Our meta-analysis aimed to investigate the association between tV, PEEP, and driving pressure and the above-mentioned outcomes.

METHODS

We conducted a systematic review and meta-analysis of RCTs from inception to May 19, 2022. The primary outcome was the incidence of postoperative pulmonary complications; the secondary outcomes were intraoperative cardiovascular complications and 30-day mortality. Primary and secondary outcomes were evaluated stratifying patients in the following groups: (1) low tV (LV, tV 6-8 ml kg-1 and PEEP ≥5 cm H2O) vs high tV (HV, tV >8 ml kg-1 and PEEP=0 cm H2O); (2) higher PEEP (HP, ≥6 cm H2O) vs lower PEEP (LP, <6 cm H2O); and (3) driving pressure-guided PEEP (DP) vs fixed PEEP (FP).

RESULTS

We included 16 RCTs with a total sample size of 4993. The incidence of postoperative pulmonary complications was lower in patients treated with LV than with HV (OR=0.402, CI 0.280-0.577, P<0.001) and lower in DP than in FP group (OR=0.358, CI 0.187-0.684, P=0.002). Postoperative pulmonary complications did not differ between HP and LP groups; the incidence of intraoperative cardiovascular complications was higher in HP group (OR=1.385, CI 1.027-1.867, P=0.002). The 30-day mortality was not influenced by the ventilation strategy.

CONCLUSIONS

Optimal intraoperative mechanical ventilation is unclear; however, our meta-analysis showed that low tidal volume and driving pressure-guided PEEP strategies were associated with a reduction in postoperative pulmonary complications.

Effect of noninvasive respiratory support after extubation on postoperative pulmonary complications in obese patients: A systematic review and network meta-analysis

STUDY OBJECTIVE

Obesity is associated with an increased risk of sleep-disordered breathing (SDB) and postoperative pulmonary complications (PPCs). Postoperative noninvasive respiratory support (NRS) has been recommended to obese patients despite the controversy about its benefit. The network meta-analysis (NMA) was used in this study to compare the effect of different methods of NRS on preventing PPCs in obese patients.

DESIGN

This study is a network meta-analysis.

SETTING

Post-anesthesia care unit and inpatient ward.

PATIENTS

20 randomized controlled trials involving 1184 obese patients were included in the final analysis.

INTERVENTIONS

One of the four NRS techniques, which include continuous positive airway pressure (CPAP), bi-level positive airway pressure (BiPAP), high-flow nasal cannula (HFNC), or conventional oxygen therapy (COT), was performed after general anesthesia.

MEASUREMENTS

The primary outcome was the incidence of PPCs, e.g., atelectasis, pneumonia, hypoxemia, and respiratory failure. The secondary outcomes included the incidence of oxygen treatment failure and anastomotic leakage, oxygenation index, and length of hospital stay (LOS). RevMan 5.3 and STATA 16.0 were used to analyze the results and any potential bias.

MAIN RESULTS

Compared with COT, BiPAP and HFNC were both effective in reducing the occurrence of postoperative atelectasis. There were no significant differences in the occurrence of other PPCs including pneumonia, hypoxemia and respiratory failure between the four NRS techniques. CPAP and HFNC were superior to other techniques in improving oxygenation and shortening LOS respectively. No differences were found in oxygen treatment failure and anastomotic leakage between the patients with different NRS. HFNC ranked the first in five of the eight outcomes (hypoxemia, respiratory failure, treatment failure, anastomotic leakage, LOS) in this review by the surface under the cumulative ranking curve (SUCRA).

CONCLUSION

Among the four postoperative NRS techniques, HFNC seems to be the optimal choice for obese patients which shows certain advantages in reducing the risk of PPCs and shortening LOS.

Optimal positive end-expiratory pressure titration of intraoperative mechanical ventilation in different operative positions of female patients under general anesthesia

Objective

This study aimed to compare the effectiveness and safety of different titrated methods used to determine individual positive end-expiratory pressure (PEEP) for intraoperative mechanical ventilation in female patients undergoing general anesthesia in different operative positions, and provide reference ranges of optimal PEEP values based on the titration.

Methods

A total of 123 female patients who underwent elective open abdominal surgery under general anesthesia were included in this study. After endotracheal intubation, patients' body position was adjusted to the supine position, Trendelenburg positions at 10° and 20° respectively. PEEP was titrated from 20 cmH2O to 4 cmH2O, decreasing by 2 cmH2O every 1 min. Electrical impedance tomography (EIT), hemodynamic and respiratory mechanics parameters were continuously monitored and recorded. Optimal PEEP values and reference ranges were respectively calculated based on optimal EIT parameters, mean arterial pressure (MAP), and lung dynamic compliance (Cdyn).

Results

EIT-guided optimal PEEP was found to have higher values than those of the MAP-guided and Cdyn-guided methods for all three body positions (P < 0.001), and it was observed to more significantly inhibit hemodynamics (P < 0.05). The variable coefficients of EIT-guided optimal PEEP values were smaller than those of the other two methods, and this technique could provide better ventilation uniformity for dorsal/ventral lung fields and better balance for pulmonary atelectasis/collapse. The 95% reference ranges of EIT-guided optimal PEEP values were 4.6-13.8 cmH2O, 7.0-15.0 cmH2O and 8.6-17.0 cmH2O for the supine position, Trendelenburg 10°, and Trendelenburg 20° positions, respectively.

Conclusion

EIT-guided optimal PEEP titration was found to be a superior method for lung protective ventilation in different operative positions under general anesthesia. The calculated reference ranges of PEEP values based on the EIT-guided method can be used as a reference for intraoperative mechanical ventilation.

Robot-Assisted versus Laparoscopic Gastrointestinal Surgery: A Systematic Review and Metanalysis of Intra- and Post-Operative Complications

BACKGROUND

The use of robotic surgery is attracting ever-growing interest for its potential advantages such as small incisions, fine movements, and magnification of the operating field. Only a few randomized controlled trials (RCTs) have explored the differences in perioperative outcomes between the two approaches.

METHODS

We screened the main online databases from inception to May 2023. We included studies in English enrolling adult patients undergoing elective gastrointestinal surgery. We used the following exclusion criteria: surgery with the involvement of thoracic esophagus, and patients affected by severe heart, pulmonary and end-stage renal disease. We compared intra- and post-operative complications, length of hospitalization, and costs between laparoscopic and robotic approaches.

RESULTS

A total of 18 RCTs were included. We found no differences in the rate of anastomotic leakage, cardiovascular complications, estimated blood loss, readmission, deep vein thrombosis, length of hospitalization, mortality, and post-operative pain between robotic and laparoscopic surgery; post-operative pneumonia was less frequent in the robotic approach. The conversion to open surgery was less frequent in the robotic approach, which was characterized by shorter time to first flatus but higher operative time and costs.

CONCLUSIONS

The robotic gastrointestinal surgery has some advantages compared to the laparoscopic technique such as lower conversion rate, faster recovery of bowel movement, but it has higher economic costs.

Evaluating the Clinical Application of Automatic Chromosome Harvesting for Prenatal Karyotype Analysis

Objective: The clinical value of an automatic chromosome harvester was evaluated, which included a comparison between the manual and automatic harvesting for the isolation of amniotic fluid cell chromosomes. Methods: Amniotic fluid samples from 96 high-risk gravida cases identified at 17-25 weeks treated at the Prenatal Diagnostic and Reproductive Center from June to July 2022 were collected. These samples underwent both manual and automatic chromosome collection, and their harvest time and number of amniotic cells were compared. These chromosomes were then used to produce karyotypic data for each sample using an automatic chromosomal karyotype analysis system, scan karyotype. Results: The average automatic harvesting time per sample, 3.92 min, was significantly lower than that of the manual harvesting, 7.89 min (p < 0.001). In addition, the average number of cells from the automatic harvesting (4.16 × 106 pieces) was significantly increased when compared with those of the manual group (2.10 × 106 pieces; p < 0.001). Further karyotyping revealed that both sets of chromosomes produced clear bands and good dispersion data, producing no significant differences in these evaluations (p > 0.05). However, the number of analyzable karyotypes obtained using the automatic harvester was significantly higher than those of the manual harvesting (p < 0.001). Conclusions: The automatic chromosome harvester can effectively save time, manual labor and consumables, harvest more analyzable karyotypes, and improve the efficiency of clinical diagnosis. The automatic chromosome harvester is highly stable and repeatable, which has the potential to help achieve large-scale standardized chromosome harvesting and is worthy of widespread clinical promotion.