High-frequency vs. conventional ventilation at the time of CDH repair is not associated with higher mortality and oxygen dependency: a retrospective cohort study

PURPOSE

The VICI-trial reported that in patients with congenital diaphragmatic hernia (CDH), mortality or bronchopulmonary dysplasia (BPD) were equivalent using conventional mechanical ventilation (CMV) and high-frequency oscillatory ventilation. The purpose of this study was to determine if the mode of ventilation at the time of CDH repair affected mortality or oxygen dependence at 28 days.

METHODS

We performed a retrospective cohort study of infants born wih CDH from 1991 to 2015. A generalized linear model was applied to the data using a propensity score analysis.

RESULTS

Eighty patients met the inclusion criteria; at the time of surgery 39 (48.8%) patients were on HFV and 41 (51.3%) patients were on CMV. In the HFV group, 16 (47.1%) patients remained oxygen dependent and there were 5 (12.8%) deaths at 28 days. In the CMV group, 5 (12.2%) patients remained oxygen dependent at 28 days but none had died. The base model demonstrated that the HFV group had increased rates of oxygen dependence [OR = 6.40 (2.13, 22.2), p = 0.002]. However, after propensity score analysis, we found no difference between HFV and CMV.

CONCLUSION

Our study suggests that in infants with CDH, there is no significant difference between HFV and CMV in oxygen dependency or death.

The effect of high-frequency oscillatory ventilation or airway pressure release ventilation on children with acute respiratory distress syndrome as a rescue therapy

BACKGROUND

To investigate the effects of high-frequency oscillatory ventilation (HFOV) or airway pressure release ventilation (APRV) as a rescue therapy on children with moderate and severe acute respiratory distress syndrome (ARDS).

METHODS

We retrospectively enrolled 47 children with ARDS who were transitioned from synchronized intermittent mandatory ventilation (SIMV) to either HFOV or APRV for 48 h or longer after failure of SIMV. The parameters of demographic data, arterial blood gases, ventilator settings, oxygenation index (OI), and PaO₂/FiO₂ (PF) ratio during the first 48 h of HFOV and APRV were recorded.

RESULTS

There was no significant difference between the HFOV and APRV groups with survival rates of 60% and 72.7%, respectively. Compared to pre-transition, the mean airway pressures at 2 and 48 h after transition were higher in both groups (P<0.01), and the PF ratio at 2 and 48 h in both modes was significantly improved (P<0.001). PF ratio and PaCO₂ have significant differences at 48 h between two groups. The OI at 2 h after transition had no improvement in either group and was substantially lower at 48 h relative to the pre-transition level (P<0.001) in both groups. At 48 h after the transition to both HFOV and APRV, the survivors had lower mean airway pressures, higher PF ratios, and a lower OIs than non-survivors (P<0.01).

CONCLUSIONS

There was no significant difference on the survival rates of HFOV and APRV application as a rescue therapy for ARDS, but improved oxygenation at 48 h reliably discriminated survivors from non-survivors in both groups.

Comparison of the ventilation characteristics in two adult oscillators: a lung model study

BACKGROUND

Two recent large randomized controlled trials did not show the superiority of high-frequency oscillatory ventilation (HFOV) in adults with ARDS. These two trials had differing results, and possible causes could be the different oscillators used and their different settings, including inspiratory time % (IT%). The aims of this study were to obtain basic data about the ventilation characteristics in two adult oscillators and to elucidate the effect of the oscillator and IT% on ventilation efficiency.

METHODS

The Metran R100 or SensorMedics 3100B was connected to an original lung model internally equipped with a simulated bronchial tree. The actual stroke volume (aSV) was measured with a flow sensor placed at the Y-piece. Carbon dioxide (CO₂) was continuously insufflated into the lung model ([Formula: see text]CO₂), and the partial pressure of CO₂ (PCO₂) in the lung model was monitored. Alveolar ventilation ([Formula: see text]A; L/min) was estimated as [Formula: see text]CO₂ divided by the stabilized value of PCO₂. [Formula: see text]A was evaluated with several stroke volume settings in the R100 (IT = 50%) or several airway pressure amplitude settings in the 3100B (IT = 33%, 50%) at a frequency of 6 and 8 Hz, a mean airway pressure of 25 cmH₂O, and a bias flow of 30 L/min. Assuming that [Formula: see text]A = frequency^a × aSV^b, values of a and b were determined. Ventilation efficiency was calculated as [Formula: see text]A divided by actual minute ventilation.

RESULTS

The relationship between aSV and [Formula: see text]A or ventilation efficiency were different depending on the oscillator and IT%. The values of a and b were 0 < a < 1 and 1 < b < 2 and were different for three conditions at both frequencies. [Formula: see text]A and ventilation efficiency were highest with R100 (IT = 50%) and lowest with 3100B (IT = 33%) for high aSV ranges at both frequencies.

CONCLUSIONS

In this lung model study, ventilation characteristics were different depending on the oscillator and IT%. Ventilation efficiency was highest with R100 (IT = 50%) and lowest with 3100B (IT = 33%) for high aSV ranges.

Bias flow rate and ventilation efficiency during adult high-frequency oscillatory ventilation: a lung model study

Background

Bias flow (BF) is essential to maintain mean airway pressure (MAP) and to washout carbon dioxide (CO₂) from the oscillator circuit during high-frequency oscillatory ventilation (HFOV). If the BF rate is inadequate, substantial CO₂ rebreathing could occur and ventilation efficiency could worsen. With lower ventilation efficiency, the required stroke volume (SV) would increase in order to obtain the same alveolar ventilation with constant frequency. The aim of this study was to assess the effect of BF rate on ventilation efficiency during adult HFOV.

Methods

The R100 oscillator (Metran, Japan) was connected to an original lung model internally equipped with a simulated bronchial tree. The actual SV was measured with a flow sensor placed at the Y-piece. Carbon dioxide (CO₂) was continuously insufflated into the lung model (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{\mathrm{V}} $$\end{document}V˙CO₂), and the partial pressure of CO₂ (PCO₂) in the lung model was monitored. Alveolar ventilation (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{\mathrm{V}} $$\end{document}V˙A) was estimated as \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{\mathrm{V}} $$\end{document}V˙CO₂ divided by the stabilized value of PCO₂. \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{\mathrm{V}} $$\end{document}V˙A was evaluated by setting SV from 80 to 180 mL (10 mL increments, n = 5) at a frequency of 8 Hz, a MAP of 25 cmH₂O, and a BF of 10, 20, 30, and 40 L/min (study 1). Ventilation efficiency was calculated as \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{\mathrm{V}} $$\end{document}V˙A divided by the actual minute volume. The experiment was also performed with an actual SV of 80, 100, and 120 mL and a BF from 10 to 60 L/min (10 L/min increments: study 2).

Results

Study 1: With the same setting SV, the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{\mathrm{V}} $$\end{document}V˙A with a BF of 20 L/min or more was significantly higher than that with a BF of 10 L/min. Study 2: With the same actual SV, the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{\mathrm{V}} $$\end{document}V˙A and the ventilation efficiency with a BF of 30 L/min or more were significantly higher than those with a BF of 10 or 20 L/min.

Conclusions

Increasing BF up to 30 L/min or more improved ventilation efficiency in the R100 oscillator.

Electronic supplementary material

The online version of this article (10.1186/s40635-018-0176-3) contains supplementary material, which is available to authorized users.