Newer modes of mechanical ventilation for the neonate

"Current concepts in assisted mechanical ventilation in the neonate" - Part 2: Understanding various modes of mechanical ventilation and recommendations for individualized disease-based approach in neonates

Mechanical ventilation is a lifesaving intervention in critically ill preterm and term neonates. However, it has the potential to cause significant damage to the lungs resulting in long-term complications. Understanding the pathophysiological process and having a good grasp of the basic concepts of conventional and high-frequency ventilation is essential for any medical or allied healthcare practitioner involved in the neonates' respiratory management. This review aims to describe the various types and modes of ventilation usually available in neonatal units. It also describes recommendations of an individualized disease-based approach to mechanical ventilation strategies implemented in the authors' institutions.

Mechanical ventilation modes for respiratory distress syndrome in infants: a systematic review and network meta-analysis

Introduction

The effects of different mechanical ventilation (MV) modes on mortality outcome in infants with respiratory distress syndrome (RDS) are not well known.

Methods

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) in the Cochrane Library, EMBASE, MEDLINE, CINAHL, and Web of Science for studies published through April 2014 that assessed mortality in infants with RDS given different MV modes. We assessed studies for eligibility, extracted data, and subsequently pooled the data. A Bayesian fixed-effects model was used to combine direct comparisons with indirect evidence. We also performed sensitivity analyses and rankings of the competing treatment modes.

Results

In total, 20 randomized controlled trials were included for the network meta-analysis, which consisted of 2,832 patients who received one of 16 ventilation modes. Compared with synchronized intermittent mandatory ventilation (SIMV) + pressure support ventilation (PSV), time-cycled pressure-limited ventilation (TCPL) (hazard ratio (HR) 0.290; 95% confidence interval (CI) 0.071 to 0.972), high-frequency oscillatory ventilation (HFOV) (HR 0.294; 95% CI 0.080 to 0.852), SIMV + volume-guarantee (VG) (HR 0.122; 95% CI 0.014 to 0.858), and volume-controlled (V-C) (HR 0.139; 95% CI 0.024 to 0.677) ventilation modes are associated with lower mortality. The combined results of available ventilation modes were not significantly different in regard to the incidences of patent ductus arteriosus and intraventricular hemorrhage.

Conclusion

Compared with the SIMV + PSV ventilation mode, the TCPL, HFOV, SIMV + VG, and V-C ventilation modes are associated with lower mortality.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-0843-7) contains supplementary material, which is available to authorized users.

Newer nonconventional modes of mechanical ventilation

The conventional modes of ventilation suffer many limitations. Although they are popularly used and are well-understood, often they fail to match the patient-based requirements. Over the years, many small modifications in ventilators have been incorporated to improve patient outcome. The ventilators of newer generation respond to patient's demands by additional feedback systems. In this review, we discuss the popular newer modes of ventilation that have been accepted in to clinical practice. Various intensive care units over the world have found these modes to improve patient ventilator synchrony, decrease ventilator days and improve patient safety. The various modes discusses in this review are: Dual control modes (volume assured pressure support, volume support), Adaptive support ventilation, proportional assist ventilation, mandatory minute ventilation, Bi-level airway pressure release ventilation, (BiPAP), neurally adjusted ventilatory assist and NeoGanesh. Their working principles with their advantages and clinical limitations are discussed in brief.

Daily practice of mechanical ventilation in Italian pediatric intensive care units: a prospective survey

OBJECTIVES

To assess how children requiring endotracheal intubation are mechanically ventilated in Italian pediatric intensive care units (PICUs).

DESIGN

A prospective, national, observational, multicenter, 6-month study.

SETTING

Eighteen medical-surgical PICUs.

PATIENTS

A total of 1943 consecutive children, aged 0-16 yrs, admitted between November 1, 2006 and April 30, 2007.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Data on cause of respiratory failure, length of mechanical ventilation (MV), mode of ventilation, use of specific interventions were recorded for all children requiring endotracheal intubation for >24 hrs. Children were stratified for age, type of patient, and cause of respiratory failure. A total of 956 (49.2%) patients required MV via an endotracheal tube; 673 (34.6%) were ventilated for >24 hrs. The median length of MV was 4.5 days for all patients. If postoperative patients were excluded, the median time was 5 days. Bronchiolitis (6.7%), pneumonia (6.7%), and upper airway obstruction (5.3%) were the most frequent causes of acute respiratory failure, and altered mental status (9.2%) was the most frequent reason for MV. The overall mortality was 6.7% with highest rates for heart disease (nonoperative), sepsis, and acute respiratory distress syndrome (26.1%, 22.2%, and 16.7% respectively). Length of stay, associated chronic disease, severity score on admission, and PICU mortality were significantly higher in children who received MV (p < .05) than in children who did not. Controlled MV and pressure support ventilation + synchronized intermittent mandatory ventilation were the most frequently used modes of ventilatory assistance during PICU stay.

CONCLUSIONS

Mechanical ventilation is frequently used in Italian PICUs with almost one child of two requiring endotracheal intubation. Children treated with MV represent a more severe category of patients than children who are breathing spontaneously. Describing the standard care and how MV is performed in children can be useful for future clinical studies.

Ventilatory management and bronchopulmonary dysplasia in preterm infants

Improvements in antenatal and neonatal care have resulted in increased survival of very preterm infants. However, the incidence of bronchopulmonary dysplasia (BPD) has not changed, probably as a consequence of a demographic shift. The underlying pathophysiology of BPD appears to differ for the current population of preterm infants compared to that described by Northway et al., and management strategies should be targeted to limit ventilator-induced lung injury. Non-invasive respiratory support techniques are currently under evaluation, but results of the trials have thus far failed to show a reduction in BPD. This review will focus upon various ventilation modalities for preventing and managing bronchopulmonary dysplasia.

Newer forms of conventional ventilation for preterm newborns

Although life saving, mechanical ventilation can cause complications such as ventilator-induced lung injury and bronchopulmonary dysplasia in very preterm babies. The ventilator-induced lung injury is multi-factorial. There has been an introduction of a number of newer forms of mechanical ventilation, which are aimed to reduce such complications. These are based on sound physiologic principles and clinicians should familiarize themselves with these advances.

Mechanical ventilation of very low birth weight infants: is volume or pressure a better target variable?

OBJECTIVE

To compare the efficacy and safety of volume-controlled (VC) ventilation to time-cycled pressure-limited (TCPL) ventilation in very low birth weight infants with respiratory distress syndrome (RDS).

STUDY DESIGN

Newborns weighing between 600 and 1500 g and with a gestational age of 24 to 31 weeks who had RDS were randomized to receive either VC or TCPL ventilation and treated with a standardized protocol. The 2 modalities were compared by determining the time required to achieve a predetermined success criterion, on the basis of either the alveolar-arterial oxygen gradient <100 mm Hg or the mean airway pressure <8 cm H(2)O. Secondary outcomes included mortality, duration of mechanical ventilation, and complications commonly associated with ventilation.

RESULTS

The mean time to reach the success criterion was 23 hours in the VC group versus 33 hours in the TCPL group (P = .15). This difference was more striking in babies weighing <1000g (21 versus 58 hours; P = .03). Mean duration of ventilation with VC was 255 hours versus 327 hours with TCPL (P = .60). There were 5 deaths in the VC group and 10 deaths in the TCPL group (P = .10). The incidence of other complications was similar.

CONCLUSION

VC ventilation is safe and efficacious in very low birth weight infants and may have advantages when compared with TCPL, especially in smaller infants.

Minimising ventilator induced lung injury in preterm infants

Ventilator induced lung injury continues to occur at an unacceptably high rate, which is inversely related to gestational age. Although the "new BPD" may not be entirely avoidable in the extremely premature infant, recognition of risk factors and adoption of an appropriate ventilatory strategy, along with continuous real time monitoring, may help to minimise lung damage. This paper will review the pathogenesis of ventilator induced lung injury and strategies that may mitigate it.

Is there an advantage of using pressure support ventilation with volume guarantee in the initial management of premature infants with respiratory distress syndrome? A pilot study

OBJECTIVE

To evaluate the feasibility of using the pressure support ventilation with volume guarantee (PSV-VG) as an initial ventilatory mode in preterm infants with respiratory distress syndrome (RDS) after surfactant treatment to achieve accelerated weaning of peak inspiratory pressure (PIP) and mean airway pressure (MAP).

STUDY DESIGN

Initial 24-hour ventilatory parameters were compared in two groups of preterm infants managed by PSV-VG and the synchronized intermittent mandatory ventilation (SIMV) mode in a randomized controlled pilot study after surfactant treatment for RDS. A total of 16 babies were randomized to PSV-VG (1198+/-108 g [mean+/-SEM]; 27.9+/-0.6 weeks) and 18 babies to SIMV (birth weight 1055+/-77 g; gestational age 27.4+/-0.5 weeks). Repeated measures analysis of variance was used to compare serial values of PIP and MAP in the two groups.

RESULTS

The PIP and MAP decreased over time (p<0.001) during the first 24 hours after surfactant administration in both groups but the decrease in MAP was faster in the SIMV group compared to PSV-VG group (p=0.035). The median numbers of blood gases during the first 24 hours were four and two in the SIMV and PSV-VG groups, respectively (p<0.001). The overall outcomes were not significantly different between the two groups.

CONCLUSION

PSV-VG did not offer any ventilatory advantage over SIMV in the initial management of surfactant-treated premature newborns with RDS except for minimizing the number of blood gases.

Newer techniques of mechanical ventilation: an overview

The introduction of newer, state-of-the-art, microprocessor controlled ventilator systems provides clinicians with opportunities to apply a number of advanced ventilatory modalities which were not previously available for treating newborns. Some of these techniques will need further scientific evaluation in controlled trials, but this should not preclude their use in clinical settings, as their safety has already been proved by "standard setters" for use in neonates. There is a firm physiological rationale for their use, and individual centres have already acquired substantial experience in the application of these modalities. The trend towards increasing sophistication and greater versatility is likely to continue, and clinicians involved in the care of sick newborn infants must keep abreast of these developments.

Weaning newborns from mechanical ventilation

While there is a relative consensus as to whether mechanical ventilation should be initiated, the management of babies during recovery from respiratory failure remains largely subjective and is predominantly determined by institutional or individual practices or preferences. This can lead to babies either being left on the ventilator too long, or extubated too hastily, thus requiring repeated re-intubation. The current scientific literature fails to provide a uniform view of the most appropriate way to wean babies from mechanical ventilation. This might stem from a lack of understanding of the relative merits of the different techniques of discontinuing mechanical ventilation, given the availability of a variety of primary ventilatory modes which were not available to a neonatal population before, and limited research into the pathophysiological mechanisms responsible for an unsuccessful extubation. The purpose of this paper is to review the physiological, mechanical, and clinical principles of weaning, and to highlight areas still in need of investigation.

Neonatal respiratory failure

The classic entity of neonatal distress syndrome, as a lung disease expressing predominant surfactant deficiency, is currently changing to a more complex disease of the developing lung as a result of the number of extremely immature preterm infants. Prenatal factors, such as the fetal inflammatory response syndrome influence short- and long-term outcome in these premature infants presenting with respiratory distress syndrome at birth. Therefore, various previously dismissed treatment strategies, such as surfactant prophylaxis or newer anti-inflammatory approaches have to be reinvestigated in this emerging population. Despite the resurrection of a new picture of bronchopulmonary dysplasia, lung injury induced by mechanical ventilation remains a major issue in neonatal intensive care. With the advance in understanding of mechanical ventilation, it is becoming evident, that improvement in outcome can not be achieved by restoring normal lung physiology in the diseased lung using sophisticated ventilators and ventilation modes. A more disease specific ventilator strategy that will target as early as possible homogenous lung opening while at the same time avoiding overdistention of the lung, has the potential to affect outcome. The possible antiinflammatory properties of surfactant-proteins, nitric oxide and corticosteroids, despite some drawbacks, may show to have a synergistic effect. However, this needs further exploration.