Synchronized intermittent mandatory ventilation with volume guarantee and pressure support in neonates: Detailed analysis of ventilator parameters

OBJECTIVE

To analyse the relationship between peak inflating pressure, expired tidal volume, respiratory rate, and inspiratory time of volume-guaranteed ventilator inflations and pressure-supported spontaneous breaths during synchronized intermittent positive pressure mode with volume guarantee and pressure support (SIMV-VG-PS) in neonates.

METHODS

Ventilator parameters were downloaded every second from 16 babies ventilated with SIMV-VG-PS mode using Dräger Babylog VN500 ventilators over 137 days. Transcutaneous carbon dioxide (tcCO₂ ) data were also collected. Data were computationally analysed using Python. The average of each ventilator parameter was determined during each minute separately for ventilator inflations and for spontaneous breaths. These values were compared and their effect on tcCO₂ levels was also analysed.

RESULTS

The relationship between the peak inflating pressure of the volume guaranteed inflations (PIP_VG ) and pressure-supported spontaneous breaths (PIP_PS ) was highly variable. The PIP_PS /PIP_VG ratio differed significantly from the value (0.66) targeted by clinicians (group median: 0.80, range: 0.50-1.00). PIP_PS frequently exceeded PIP_VG . When PIP_PS /PIP_VG was >0.66, the expired tidal volume and the rate of the pressure-supported spontaneous breaths were also significantly (p < 0.0001) higher, but there was no difference in tcCO₂ levels. The flow-cycled spontaneous breaths had significantly shorter inspiratory times than ventilator inflations.

CONCLUSIONS

During SIMV-VG-PS it is difficult to ensure a pressure support level proportionate to the inflating pressure of ventilator inflations and to achieve the stability of tidal volumes.

Impact of High-Frequency Oscillatory Ventilation Combined With Volume Guarantee on Lung Inflammatory Response in Infants With Acute Respiratory Distress Syndrome After Congenital Heart Surgery: A Randomized Controlled Trial

OBJECTIVES

Congenital heart disease (CHD) after cardiopulmonary bypass can cause systemic inflammation, and its degree is closely related to the incidence of acute respiratory distress syndrome (ARDS). The purpose of this study was to determine the effectiveness of high-frequency oscillatory ventilation (HFOV) combined with volume guarantee (VG) in reducing systemic inflammation in infants with ARDS after cardiopulmonary bypass for congenital heart surgery.

DESIGN

A randomized controlled trial.

SETTING

Single-center study in a tertiary teaching hospital.

PARTICIPANTS

A total of 58 infants with ARDS after congenital heart surgery were eligible and were randomized to the HFOV (n = 29) or the HFOV-VG (n = 29) between January 2020 and January 2021.

INTERVENTIONS

Tracheal aspirate samples for the measurement of interleukin (IL)-6, IL-8, and tumor necrosis factor-α (TNF-α) were obtained on days one, two, and three of HFOV or HFOV-VG ventilation.

MEASUREMENTS AND MAIN RESULTS

The authors found a significantly increasing trend in the HFOV group mean values of IL-6, IL-8, and TNF-α (p < 0.05 on days two and three v day one), and IL-6, IL-8, and TNF-α levels were significantly higher on day three in the HFOV group versus the HFOV+VG group (p < 0.05). In addition, the incidences of hypocapnia and hypercapnia in infants supported with HFOV-VG were significantly lower (p < 0.05). Furthermore, the postoperative mechanical ventilation duration in the HFOV-VG group also was shorter than that in the HFOV group (p < 0.05).

CONCLUSION

Compared with HFOV alone, HFOV-VG reduced proinflammatory systemic reactions after congenital cardiac surgery, decreased the incidences of hypercapnia and hypocapnia, and shortened the postoperative mechanical ventilation duration.

Application of high-frequency oscillation ventilation combined with volume guarantee in infants with acute hypoxic respiratory failure after congenital heart surgery

OBJECTIVE

This study aimed to evaluate the efficacy and safety of high-frequency oscillation ventilation combined with volume guarantee (HFOV-VG) compared with the safety and efficacy of HFOV alone in infants with acute hypoxemic respiratory failure (AHRF) after congenital heart surgery.

METHODS

We retrospectively analyzed the clinical data of 44 infants who were ventilated for AHRF after congenital heart surgery between January 2020 and January 2021. HFOV alone was used in 23 of the 44 infants, whereas HFOV-VG was used in the other 21 infants.

RESULTS

The average frequency tidal volume (VThf) of the HFOV-VG group was lower than that of the HFOV group, and the proportion of VThf exceeding the target range of infants in the HFOV-VG group was also lower (p < .01). In addition, the incidence of hypocapnia and hypercapnia in infants supported with HFOV-VG was significantly lower (p < .01). Furthermore, the duration of invasive ventilation and the median ventilator adjustment per hour in the HFOV-VG group was also lower than that in the HFOV group (p < .01).

CONCLUSIONS

Compared with HFOV alone, HFOV-VG decreases the fluctuation of VThf and the incidence of hypercapnia and hypocapnia. Moreover, it reduces the workload of bedside medical staff. Further studies are needed to confirm the efficacy and safety of HFOV-VG as a routine respiratory support strategy for congenital heart disease during the perioperative period.

Comparison of Volume-Guaranteed or -Targeted, Pressure-Controlled Ventilation with Volume-Controlled Ventilation during Elective Surgery: A Systematic Review and Meta-Analysis

For perioperative mechanical ventilation under general anesthesia, modern respirators aim at combining the benefits of pressure-controlled ventilation (PCV) and volume-controlled ventilation (VCV) in modes typically named “volume-guaranteed” or “volume-targeted” pressure-controlled ventilation (PCV-VG). This systematic review and meta-analysis tested the hypothesis that PCV-VG modes of ventilation could be beneficial in terms of improved airway pressures (P_peak, P_plateau, P_mean), dynamic compliance (C_dyn), or arterial blood gases (P_aO₂, P_aCO₂) in adults undergoing elective surgery under general anesthesia. Three major medical electronic databases were searched with predefined search strategies and publications were systematically evaluated according to the Cochrane Review Methods. Continuous variables were tested for mean differences using the inverse variance method and 95% confidence intervals (CI) were calculated. Based on the assumption that intervention effects across studies were not identical, a random effects model was chosen. Assessment for heterogeneity was performed with the χ² test and the I² statistic. As primary endpoints, P_peak, P_plateau, P_mean, C_dyn, P_aO₂, and P_aCO₂ were evaluated. Of the 725 publications identified, 17 finally met eligibility criteria, with a total of 929 patients recruited. Under supine two-lung ventilation, PCV-VG resulted in significantly reduced P_peak (15 studies) and P_plateau (9 studies) as well as higher C_dyn (9 studies), compared with VCV [random effects models; P_peak: CI −3.26 to −1.47; p < 0.001; I² = 82%; P_plateau: −3.12 to −0.12; p = 0.03; I² = 90%; C_dyn: CI 3.42 to 8.65; p < 0.001; I² = 90%]. For one-lung ventilation (8 studies), PCV-VG allowed for significantly lower P_peak and higher P_aO₂ compared with VCV. In Trendelenburg position (5 studies), this effect was significant for P_peak only. This systematic review and meta-analysis demonstrates that volume-targeting, pressure-controlled ventilation modes may provide benefits with respect to the improved airway dynamics in two- and one-lung ventilation, and improved oxygenation in one-lung ventilation in adults undergoing elective surgery.

Effects of High-Frequency Oscillatory Ventilation With Volume Guarantee During Surfactant Treatment in Extremely Low Gestational Age Newborns With Respiratory Distress Syndrome: An Observational Study

OBJECTIVE

To evaluate the effect of volume guarantee (VG) combined with high-frequency oscillatory ventilation (HFOV) on respiratory and other physiological parameters immediately after lung recruitment and surfactant administration in HFOV elective ventilated extremely low gestational age newborns (ELGAN) with respiratory distress syndrome (RDS).

DESIGN

Observational study.

SETTING

Tertiary neonatal intensive care unit.

PATIENTS

Twenty-two ELGANs of 25.5 ± 1.1 weeks of gestational age requiring invasive mechanical ventilation and surfactant administration for RDS during the first 6 h of life.

INTERVENTIONS

All infants intubated in delivery room, were managed with elective HFOV and received surfactant after a lung recruitment manoeuver. Eleven infants received HFOV + VG and were compared with a control group of 11 infants receiving HFOV alone. HFOV was delivered in both groups by Dräger Babylog VN500 ventilator (Dräger, Lubeck, Germany).

MAIN OUTCOME MEASURES

Variations and fluctuations of delivered high-frequency tidal volume (VT_hf), fluctuation of pressure amplitude (ΔP) and partial pressure of CO₂ (pCO₂) levels after recruitment manoeuver and immediately after surfactant administration, in HFOV + VG vs. HFOV ventilated infants.

RESULTS

There were no significant differences in the two groups at starting ventilation with or without VG. The mean applied VT_hf per kg was 1.7 ± 0.3 ml/kg in the HFOV group and 1.7 ± 0.1 ml/kg in the HFOV + VG group. Thirty minutes after surfactant administration, HFOV group had a significant higher VT_hf/Kg than HFOV + VG (2.1 ± 0.3 vs. 1.6 ± 0.1 ml/kg, p < 0.0001) with significantly lower pCO₂ levels (43.1 ± 3.8 vs. 46.8 ± 1.5 mmHg, p = 0.01), 54.4% of patients having pCO₂ below 45 mmHg. Measured post-surfactant ΔP values were higher in HFOV group (17 ± 3 cmH₂O) than in HFOV + VG group (13 ± 3 cmH₂O, p = 0.01).

CONCLUSION

HFOV + VG maintains pCO₂ levels within target range and reduces VT_hf delivered variations more consistently than HFOV alone after surfactant administration.

New indicators for optimal lung recruitment during high frequency oscillator ventilation

Previous research has demonstrated the potential benefit derived from the combination of high frequency oscillatory ventilation and volume guarantee mode (HFOV-VG), a procedure that allows us to explore and control very low tidal volumes. We hypothesized that secondary spontaneous change in oscillation pressure amplitude (∆Phf), while increasing the mean airway pressure (MAP) using HFOV-VG can target the lung recruitment.

METHODS

A two-step animal distress model study was designed; in the first-step (ex vivo model), the animal's lungs were isolated to visually check lung recruitment and, in the second one (in vivo model), they were checked through arterial oxygen partial pressure improvement. Baseline measurements were performed, ventilation was set for 10 min and followed by bronchoalveolar lavage with isotonic saline to induce depletion of surfactant and thereby achieve a low compliance lung model. The high-frequency tidal volume and frequency remained constant and the MAP was increased by 2 cmH₂ O (ex vivo) and 3 cmH₂ O steps (in vivo) every 2 min. Changes in ΔPhf to achieve the fixed volume were recorded at the end of each interval to describe the maximum drop point as the recruitment point.

RESULTS

Fourteen Wistar Han rats were included, seven on each sub-study described. After gradual MAP increments, a progressive decrease in ΔPhf related to recruited lung regions was visually demonstrated. In the in vivo model we detected a significant comparative decrease of ΔPhf, when measured against the previous value, after reaching a MAP of 11 cmH₂ O up to 17 cmH₂ O, correlating with a significant improvement in oxygenation.

CONCLUSION

The changes in ∆Phf, linked to a progressive increase in MAP during HFOV-VG, might identify optimal lung recruitment and could potentially be used as an additional lung recruitment marker.

Volume Guarantee High-Frequency Oscillatory Ventilation in Preterm Infants With RDS: Tidal Volume and DCO2 Levels for Optimal Ventilation Using Open-Lung Strategies

High frequency oscillatory ventilation with volume-guarantee (HFOV-VG) is a promising lung protective ventilator mode for the treatment of respiratory failure in newborns. However, indicators of optimal ventilation during HFOV-VG mode are not identified yet. In this study, we aimed to evaluate optimal high-frequency tidal volume (VThf) and the dissociation coefficient of CO₂ (DCO₂) levels to achieve normocapnia during HFOV-VG after lung recruitment in very low birthweight infants with respiratory distress syndrome (RDS). Preterm babies under the 32nd postmenstrual week with severe RDS that received HFOV-VG using open-lung strategy between January 2014 and January 2019 were retrospectively evaluated. All included patients were treated with the Dräger Babylog VN500 ventilator in the HFOV-VG mode. In total, 53 infants with a mean gestational age of 26.8 ± 2.3 weeks were evaluated. HFOV mean optimal airway pressure (MAPhf) level after lung recruitment was found to be 10.2 ± 1.7 mbar. Overall, the mean applied VThf per kg was 1.64 ± 0.25 mL/kg in the study sample. To provide normocapnia, the mean VThf was 1.61 ± 0.25 mL/kg and the mean DCO₂corr was 29.84 ± 7.88 [mL/kg]²/s. No significant correlation was found between pCO₂ levels with VThf (per kg) or DCO₂corr levels. VThf levels to maintain normocarbia were significantly lower with 12 Hz frequency compared to 10 Hz frequency (1.50 ± 0.24 vs. 1.65 ± 0.25 mL/ kg, p < 0.001, respectively). A weak but significant positive correlation was found between mean airway pressure (MAPhf) and VThf levels. To our knowledge, this is the largest study to evaluate the optimal HFOV-VG settings in premature infants with RDS, using the open-lung strategy. According to the results, a specific set of numbers could not be recommended to achieve normocarbia. Following the trend of each patient and small adjustments according to the closely monitored pCO₂ levels seems logical.