Effect of the Prolonged Inspiratory to Expiratory Ratio on Oxygenation and Respiratory Mechanics During Surgical Procedures

Pressure Control Ventilation Versus Volume Control Ventilation in Laparoscopic Surgery: A Narrative Review

This review compares the safety and effectiveness of volume control ventilation (VCV) and pressure control ventilation (PCV) during laparoscopic surgery. Nine studies were chosen for in-depth examination following the application of stringent inclusion and exclusion criteria to the 184 publications that the literature search turned up. PCV is well-known for its capacity to preserve lower peak airway pressures during laparoscopic procedures, lowering the risk of volutrauma and barotrauma and enhancing oxygenation under these conditions of elevated intra-abdominal pressures. On the other hand, VCV guarantees a constant tidal volume and offers accurate ventilation management, both of which are essential for preserving stable carbon dioxide levels. VCV, however, may result in higher peak airway pressures, raising the risk of lung damage brought on by a ventilator. Research indicates that PCV provides better respiratory mechanics management during laparoscopic surgery, but VCV consistent tidal volume delivery is useful in some clinical situations. When choosing between PCV and VCV, the anesthesia team's experience, the demands of each patient, and the surgical circumstances should all be taken into consideration. Real-time monitoring tools and sophisticated ventilatory technology are essential for maximizing ventilation techniques. Further improving patient outcomes can be achieved by incorporating multimodal anesthesia approaches, such as the use of muscle relaxants and customized intraoperative fluid management. Muscle relaxants optimize conditions for mechanical ventilation by ensuring adequate muscle relaxation, reducing the risk of ventilator-associated lung injury, and enabling more precise control of ventilation parameters. Tailored intraoperative fluid management helps maintain optimal lung mechanics by avoiding fluid overload, which can lead to pulmonary edema and compromised gas exchange, necessitating adjustments in ventilation strategy. While both ventilation modalities can be utilized efficiently, the research suggests that PCV may be more advantageous in controlling oxygenation and airway pressures. In the dynamic and demanding world of laparoscopic surgery, ongoing research and clinical innovation are crucial to improving these tactics and guaranteeing the best possible treatment. In order to obtain the best possible patient outcomes during laparoscopic surgeries, this review emphasizes the significance of customized breathing techniques.

Inverse ratio ventilation versus conventional ratio ventilation during one lung ventilation in neonatal open repair of esophageal atresia/tracheoesophageal fistula: A randomized clinical trial

BACKGROUND

Maintaining oxygenation during neonatal open repair of esophageal atresia/tracheoesophageal fistula is difficult. Inverse ratio ventilation can be used during one lung ventilation to improve the oxygenation and lung mechanics.

OBJECTIVE

The aim of this study was to describe the impact of two different ventilatory strategies (inverse ratio ventilation vs. conventional ratio ventilation) during one lung ventilation in neonatal open repair of esophageal atresia/tracheoesophageal fistula on the incidence of oxygen desaturation episodes.

METHODS

We enrolled 40 term neonates undergoing open right thoracotomy for esophageal atresia/tracheoesophageal fistula repair and randomly assigned into two groups based on inspiratory to expiratory ratio of mechanical ventilation parameters (2:1 in inverse ratio ventilation "IRV" and 1:2 in conventional ratio ventilation "CRV"). The incidence of desaturation episodes that required stopping the procedure and reinflation of the lung were recorded as the primary outcome while hemodynamic parameters, incidence of complications, and length of surgical procedure were recorded as the secondary outcomes.

RESULTS

There was a trend toward a reduction in the incidence of severe desaturations (requiring stopping of surgery) with the use of inverse ratio ventilation (15% in IRV vs. 35% in CRV, RR [95% CI] 0.429 [0.129-1.426]). Incidence of all desaturations (including those requiring only an increase in ventilatory support or inspired oxygen saturation) was also reduced (40% in IRV vs. 75% in CRV, RR [95% CI] 0.533 [0.295-0.965]). This in turn affected the length of surgical procedure being significantly shorter in inverse ratio ventilation group (mean difference -16.3, 95% CI -31.64 to -0.958). The intraoperative fraction of inspired oxygen required to maintain adequate oxygen saturation was significantly lower in the inverse ratio ventilation group than in the conventional ratio ventilation group (mean difference -0.22, 95% CI -0.33 to -0.098), with no significant difference in hemodynamic stability or complications apart from higher blood loss in inverse ratio group.

CONCLUSION

There may be a role for inverse ratio ventilation with appropriate positive end-expiratory pressure to reduce the incidence of hypoxemia during open repair of esophageal atresia/tracheoesophageal fistula in neonates, further studies are required to establish the safety and efficacy of this technique.

The effect of inverse ratio ventilation on cardiopulmonary function in obese laparoscopic surgery patients: A systematic review and meta-analysis

This study aimed to evaluate the effect of inverse ratio ventilation (IRV) strategy on cardiopulmonary function in obese patients under general anesthesia. Databases such as China National Knowledge Infrastructure (CNKI), Wangfang, WeiP, Web of Science, the Cochrane Library, and PubMed were systematically searched. All randomized controlled trials' literature on IRV during laparoscopic surgery in obese patients under general anesthesia was collected. After data were extracted and cross-checked, Rev Man 5.3 software was used for meta-analysis. Finally, five randomized controlled clinical trials (RCTs) were included in the meta-analysis, with a total of 312 patients. Compared with the conventional ventilation group, the inspiratory peak pressure was lower at pneumoperitoneum 30 min and pneumoperitoneum 60 min; the PaO2 and oxygenation index were higher at pneumoperitoneum 60 min, and mean airway pressure was higher at pneumoperitoneum 30 min and pneumoperitoneum 60 min; the dynamic lung compliance was superior at pneumoperitoneum 30 min and pneumoperitoneum 60 min. IRV applied to laparoscopic surgery in obese patients under general anesthesia not only reduces peak airway pressure and improves intraoperative oxygenation index and PaO2 but also enhances mean airway pressure and dynamic lung compliance, which has a specific lung protective effect. It can be used as an option for the mechanical ventilation model in obese patients in clinical practice.

Improving Certified Registered Nurse Anesthetists' Adherence to a Standardized Intraoperative Lung Protective Ventilation Protocol

PURPOSE

The use of lung protective ventilation (LPV) during general anesthesia is an effective strategy among certified registered nurse anesthetists (CRNAs) to reduce and prevent the incidence of postoperative pulmonary complications. The purpose of this project was to implement a LPV protocol, assess CRNA provider adherence, and investigate differences in ventilation parameters and postoperative oxygen requirements.

DESIGN

This quality improvement project was conducted using a pre- and postimplementation design.

METHODS

Sixty patients undergoing robotic laparoscopic abdominal surgery and 35 CRNAs at a community hospital participated. An evidence-based intraoperative LPV protocol was developed, CRNA education was provided, and the protocol was implemented. Pre- and postimplementation, CRNA knowledge, and confidence were assessed. Ventilation data were collected at 1-minute intervals intraoperatively and oxygen requirements were recorded in the postanesthesia care unit (PACU).

FINDINGS

Use of intraoperative LPV strategies increased 2.4%. Overall CRNA knowledge (P = .588), confidence (P = .031), and practice (P < .001) improved from pre- to postimplementation. Driving pressures decreased from pre- to postimplementation (P < .001). Supplemental oxygen use on admission to the PACU decreased from 93.3% to 70.0%.

CONCLUSIONS

Educational interventions and implementation of a standardized protocol can improve the use of intraoperative LPV strategies and patient outcomes.

Changes in dead space components during pressure-controlled inverse ratio ventilation: A secondary analysis of a randomized trial

Background

We previously reported that there were no differences between the lung-protective actions of pressure-controlled inverse ratio ventilation and volume control ventilation based on the changes in serum cytokine levels. Dead space represents a ventilation-perfusion mismatch, and can enable us to understand the heterogeneity and elapsed time changes in ventilation-perfusion mismatch.

Methods

This study was a secondary analysis of a randomized controlled trial of patients who underwent robot-assisted laparoscopic radical prostatectomy. The inspiratory to expiratory ratio was adjusted individually by observing the expiratory flow-time wave in the pressure-controlled inverse ratio ventilation group (n = 14) and was set to 1:2 in the volume-control ventilation group (n = 13). Using volumetric capnography, the physiological dead space was divided into three dead space components: airway, alveolar, and shunt dead space. The influence of pressure-controlled inverse ratio ventilation and time factor on the changes in each dead space component rate was analyzed using the Mann-Whitney U test and Wilcoxon’s signed rank test.

Results

The physiological dead space and shunt dead space rate were decreased in the pressure-controlled inverse ratio ventilation group compared with those in the volume control ventilation group (p < 0.001 and p = 0.003, respectively), and both dead space rates increased with time in both groups. The airway dead space rate increased with time, but the difference between the groups was not significant. There were no significant changes in the alveolar dead space rate.

Conclusions

Pressure-controlled inverse ratio ventilation reduced the physiological dead space rate, suggesting an improvement in the total ventilation/perfusion mismatch due to improved inflation of the alveoli affected by heterogeneous expansion disorder without hyperinflation of the normal alveoli. However, the shunt dead space rate increased with time, suggesting that atelectasis developed with time in both groups.

[Inverse ratio ventilation combined with PEEP in infants undergoing thoracoscopic surgery with one lung ventilation for lung cystadenomas: a randomized control trial of 63 cases]

OBJECTIVE

To investigate the effect of inverse ratio ventilation (IRV) combined with positive end-expiratory pressure (PEEP) in infants undergoing thoracoscopic surgery with single lung ventilation (OLV) for lung cystadenomas.

METHODS

A total of 66 infants undergoing thoracoscopic surgery with OLV for lung cystadenomas in our hospital from February, 2018 to February, 2019 were randomized into conventional ventilation groups (group N, n=33) and inverse ventilation group (group R, n=33). Hemodynamics and respiratory parameters of the infants were recorded and arterial blood gas analysis was performed at 15 min after two lung ventilation (TLV) (T₁), OLV30 min (T₂), OLV60 min (T₃), and 15 min after recovery of TLV (T₄). Bronchoalveolar lavage fluid was collected before and after surgery to detect the expression level of advanced glycation end product receptor (RAGE).

RESULTS

Sixty-three infants were finally included in this study. At T₂ and T₃, Cdyn, PaO₂ and OI in group R were significantly higher (P &lt; 0.05) and Ppeak, PaCO₂ and PA-aO₂ were significantly lower than those in group N (P &lt; 0.05). There was no significant difference in HR or MAP between the two groups at T₂ and T₃ (P &gt; 0.05). The level of RAGE significantly increased after the surgery in both groups (P &lt; 0.05), and was significantly lower in R group than in N group (P &lt; 0.05).

CONCLUSIONS

In infants undergoing thoracoscopic surgery with OLV for pulmonary cystadenoma, appropriate IRV combined with PEEP does not affect hemodynamic stability and can increases pulmonary compliance, reduce the peak pressure, and improve oxygenation to provide pulmonary protection.

Flow-controlled ventilation improves gas exchange in lung-healthy patients- a randomized interventional cross-over study

BACKGROUND

Flow-controlled ventilation (FCV) is a new ventilation mode that provides constant inspiratory and expiratory flow. FCV was shown to improve gas exchange and lung recruitment in porcine models of healthy and injured ventilated lungs. The primary aim of our study was to verify the influences of FCV on gas exchange, respiratory mechanics and haemodynamic variables in mechanically ventilated lung-healthy patients.

METHODS

After obtaining ethical approval and informed consent, we measured arterial blood gases, respiratory and haemodynamic variables during volume-controlled ventilation (VCV) and FCV in 20 consecutive patients before they underwent abdominal surgery. After baseline (BL) ventilation, patients were randomly assigned to either BL-VCV-FCV or BL-FCV-VCV. Thereby, BL ventilation settings were kept, except for the ventilation mode-related differences (FCV is supposed to be used with an I:E ratio of 1:1).

RESULTS

Compared to BL and VCV, PaO₂ was higher [PaO₂ : FCV: 38.2 (7.1), BL ventilation: 35.0 (5.8), VCV: 35.2 (7.0) kPa, P < .001] and PaCO₂ lower [PaCO₂ : FCV: 4.8 (0.5), BL ventilation: 5.1 (0.5), VCV: 5.1 (0.5) kPa, P < .001] during FCV. With comparable plateau pressure [BL: 14.9 (1.9), VCV: 15.3 (1.6), FCV: 15.2 (1.5) cm H₂ O), P = .185], tracheal mean pressure was higher during FCV [BL: 10.2 (1.1), VCV: 10.4 (0.7), FCV: 11.5 (1.0) cm H₂ O, P < .001]. Haemodynamic variables did not differ between ventilation phases.

CONCLUSION

Flow-controlled ventilation improves oxygenation and carbon dioxide elimination within a short time, compared to VCV with identical tidal volume, inspiratory plateau pressure and end-expiratory pressure.

Volume-Controlled Versus Dual-Controlled Ventilation during Robot-Assisted Laparoscopic Prostatectomy with Steep Trendelenburg Position: A Randomized-Controlled Trial

Dual-controlled ventilation (DCV) combines the advantages of volume-controlled ventilation (VCV) and pressure-controlled ventilation (PCV). Carbon dioxide (CO₂) pneumoperitoneum and steep Trendelenburg positioning for robot-assisted laparoscopic radical prostatectomy (RALRP) has negative effects on the respiratory system. We hypothesized that the use of autoflow as one type of DCV can reduce these effects during RALRP. Eighty patients undergoing RALRP were randomly assigned to receive VCV or DCV. Arterial oxygen tension (PaO₂) as the primary outcome, respiratory and hemodynamic data, and postoperative fever rates were compared at four time points: 10 min after anesthesia induction (T1), 30 and 60 min after the initiation of CO₂ pneumoperitoneum and Trendelenburg positioning (T2 and T3), and 10 min after supine positioning (T4). There were no significant differences in PaO₂ between the two groups. Mean peak airway pressure (Ppeak) was significantly lower in group DCV than in group VCV at T2 (mean difference, 5.0 cm H₂O; adjusted p < 0.001) and T3 (mean difference, 3.9 cm H₂O; adjusted p < 0.001). Postoperative fever occurring within the first 2 days after surgery was more common in group VCV (12%) than in group DCV (3%) (p = 0.022). Compared with VCV, DCV did not improve oxygenation during RALRP. However, DCV significantly decreased Ppeak without hemodynamic instability.

Pressure-Controlled Ventilation with Volume Guarantee Compared to Volume-Controlled Ventilation with Equal Ratio in Obese Patients Undergoing Laparoscopic Hysterectomy

Background:

Laparoscopic hysterectomy operations especially for obese patients necessitate Trendelenburg position and pneumoperitoneum with carbon dioxide, which could affect cardiac and pulmonary functions. The present study aimed to compare the impact of pressure-controlled ventilation with volume-guaranteed (PCV-VG) and volume-controlled ventilation (VCV) with equal ratio ventilation (ERV), i.e., I: E ratio of 1:1 on hemodynamics, respiratory mechanics, and oxygenation.

Patients and Methods:

Eighty females with body mass index (BMI) >30 kg/m² and with physical status American Society of Anesthesiologists Classes I and II undergoing laparoscopic hysterectomy were allocated randomly to either PCV-VG (Group P) or VCV with ERV (Group V). The ventilation parameters, hemodynamics, and arterial blood gases (ABGs) analysis were recorded at four times: (T₁): after the anesthetic induction while in supine position by 10 min, (T₂ and T₃): after the CO2 pneumoperitoneum and Trendelenburg positioning by 30 and 60 min, respectively, and (T₄): after desufflation and resuming the supine position.

Results:

The peak inspiratory pressure in Group P recorded significant lower values than in Group V while the dynamic compliance was greater significantly in Group P than in Group V. No significant differences were reported as regards the ABG analysis, oxygenation, and hemodynamic data between both groups.

Conclusion:

In obese females undergoing laparoscopic hysterectomy surgeries, PCV-VG was superior to VCV with ERV as it provided higher dynamic compliance and lower peak inspiratory pressure that could be preferable, especially in those patients in whom cardiopulmonary function could be more susceptible to impairment.

Effect of prolonged inspiratory time on gas exchange during robot-assisted laparoscopic urologic surgery

BACKGROUND

Gas exchange disturbance may develop during urologic robotic laparoscopic surgery with the patient in a steep Trendelenburg position. This study investigated whether prolonged inspiratory time could mitigate gas exchange disturbances including hypercapnia.

METHODS

In this randomized cross-over trial, 32 patients scheduled for robot-assisted urologic surgery were randomized to receive an inspiratory to expiratory time ratio (I:E) of 1:1 for the first hour of pneumoperitoneum followed by 1:2 for last period of surgery (group A, n = 17) or I:E of 1:2 followed by 1:1 (group B, n = 15). Arterial blood gas analysis, airway pressure and hemodynamic variables were assessed at four time points (T1: 10 min after induction of general anesthesia, T2: 1 h after the initiation of pneumoperitoneum, T3: 1 h after T2 and T4: at skin closure). The carry over effect of initial I:E was also evaluated over the next hour through arterial blood gas analysis.

RESULTS

There was a significant decrease in partial pressure of oxygen in arterial blood (PaO₂) for both groups at T2 and T3 compared to T1 but in group B the PaO₂ at T4 was not decreased from the baseline. Partial pressure of carbon dioxide in arterial blood (PaCO₂) increased with I:E of 1:2 but did not significantly increase with I:E of 1:1; however, there were no differences in PaO₂ and PaCO₂ between the groups.

CONCLUSION

Decreased oxygenation by pneumoperitoneum was improved and PaCO₂ did not increase after 1 h of I:E of 1:1; however, the effect of equal ratio ventilation longer than 1 h remains to be determined. There was no carryover effect of the two different I:E ratios.

Comparisons of Pressure-controlled Ventilation with Volume Guarantee and Volume-controlled 1:1 Equal Ratio Ventilation on Oxygenation and Respiratory Mechanics during Robot-assisted Laparoscopic Radical Prostatectomy: a Randomized-controlled Trial

Background: During robot-assisted laparoscopic radical prostatectomy (RALP), steep Trendelenburg position and carbon dioxide pneumoperitoneum are inevitable for surgical exposure, both of which can impair cardiopulmonary function. This study was aimed to compare the effects of pressure-controlled ventilation with volume guarantee (PCV with VG) and 1:1 equal ratio ventilation (ERV) on oxygenation, respiratory mechanics and hemodynamics during RALP. Methods: Eighty patients scheduled for RALP were randomly allocated to either the PCV with VG or ERV group. After anesthesia induction, volume-controlled ventilation (VCV) was applied with an inspiratory to expiratory (I/E) ratio of 1:2. Immediately after pneumoperitoneum and Trendelenburg positioning, VCV with I/E ratio of 1:1 (ERV group) or PCV with VG using Autoflow mode (PCV with VG group) was initiated. At the end of Trendelenburg position, VCV with I/E ratio of 1:2 was resumed. Analysis of arterial blood gases, respiratory mechanics, and hemodynamics were compared between groups at four times: 10 min after anesthesia induction (T1), 30 and 60 min after pneumoperitoneum and Trendelenburg positioning (T2 and T3), and 10 min after desufflation and resuming the supine position (T4). Results: There were no significant differences in arterial blood gas analyses including arterial oxygen tension (PaO₂) between groups throughout the study period. Mean airway pressure (Pmean) were significantly higher in the ERV group than in the PCV with VG group T2 (p<0.001) and T3 (p=0.002). Peak airway pressure and hemodynamic data were comparable in both groups. Conclusion: PCV with VG was an acceptable alternative to ERV during RALP producing similar PaO₂ values. The lower Pmean with PCV with VG suggests that it may be preferable in patients with reduced cardiovascular function.

What is the proper ventilation strategy during laparoscopic surgery?

The main stream of intraabdominal surgery has changed from laparotomy to laparoscopy, but anesthetic care for laparoscopic surgery is challenging for clinicians, because pneumoperitoneum might aggravate respiratory mechanics and arterial oxygenation. The authors reviewed the literature regarding ventilation strategies that reduce deleterious pulmonary physiologic changes during pneumoperitoneum for laparoscopic surgery under general anesthesia and make appropriate recommendations.