Mechanical Ventilators for Newborns
Mechanical Ventilators and their Role in Newborn Respiratory Support
Although the goal is to use noninvasive ventilation whenever possible, these methods, like bCPAP won’t initiate breaths if a baby isn’t breathing on its own, therefore invasive ventilation may be necessary for supporting pre-term newborns with lung disease and is considered to be an important component within the neonatal respiratory care continuum if non-invasive (e.g. bCPAP) ventilation support is insufficient. (1) Reasons for using invasive ventilation include poor gas exchange, apnea from prematurity, need for surfactant therapy, and increased work of breathing. (1) Positive pressure ventilation (PPV) (sometimes referred to as mechanical, mandatory, or intermittent positive pressure ventilation [IPPV]) refers to a spectrum of ventilation modes that deliver pressure according to the newborn who is attempting to breathe, and the ventilator assisting with breathing support. (3)
Advances in technology have improved neonatal ventilators, specifically patient triggered ventilation, monitoring, tidal volume monitoring, and more ventilation modes. However, even when invasive ventilation is required, strategies are now focused than ever on how quickly patients can transition from invasive support as it can cause lung injury and oxygen toxicity is a risk factor for newborns developing bronchopulmonary dysplasia. (1)
The decision to use a ventilator and ventilation strategy depends on a complex set of factors including age, gestation, lung condition, or other underlying conditions of the baby, as well as the availability of skilled health care workers in a neonatal intensive care unit (NICU) providers or others trained in ventilator use. For any neonatal unit, accurate patient assessment is the key element in diagnosing the condition, and fully understanding how compromised the respiratory system may be as a basis for initiating ventilation, changing ventilation strategy, or referring the newborn to higher level care.
Mechanical Ventilator Modes
The ventilation strategy, or “mode” will depend on the severity of the neonate’s condition, response to different ventilation strategies, and the attempt to wean, all of which can be affected by age, gestational age, birth weight and the level of the unit, or facility, where care is being delivered.
Modes of ventilation may differ between different models of ventilators, but typically include:
- Continuous Mandatory Ventilation (CMV) which is continuous flow of gases, but in which the neonate can attempt to take spontaneous breaths between ventilator breaths but the ventilator will deliver a breath regardless. This is the “maximum” support and for neonate has little or no spontaneous breathing in order to avoid asynchrony between the neonate and the ventilator.
- Synchronized Intermittent Mandatory Ventilation (SIMV) delivers a predetermined number of breaths per minute (BPM), which are established by detecting the neonate’s spontaneous breathing efforts and synchronizing the delivery breaths from the ventilator to match those of the neonate. (4). SIMV also allows neonate to take additional spontaneous breaths and therefore can be useful to transition ventilator support by reducing the preset rate and pressure, unless the neonate has high respiratory rates.
- Patient Trigger Ventilation (PTV) or “Assist Control” (A/C) in which with each breath from the neonate, the ventilator is triggered to deliver a breath or assist the neonate’s breath at a set pressure and inspiratory time (IT) which allows the rate to be determined by the neonate and the ventilator will provide a “backup” rate.
- Target Tidal Volume (TTV) or Volume Guarantee (VG) can be added to either SIMV, PTV, or A/C. A desired tidal volume (V T) is set by the operator and delivered by the ventilator using the lowest possible pressure necessary to reach the set V T.
- Pressure Support Ventilation (PSV) provides ventilator breaths set to a predetermined pressure to support the neonate’s breathing efforts but does not supply a backup rate; it merely assists the infant’s own breath by pressurizing the breath to the set pressure support level. This mode can be used with other modes as an “additional” feature.
- High-Frequency Ventilation (HFV) uses breath rates or “frequencies” much greater than normal physiologic breath rates
- High-frequency oscillatory ventilation (HFOV) where the pressure “oscillates” around a constant distending pressure equivalent to PEEP and Mean Airway Pressure (MAP)
- Proportional Assist Ventilation (PAV) gives assistance that is proportional to the neonate’s effort, and therefore relies more on a mature respiratory system, and less likely relevant for preterm neonates. (3)
- Neurally Adjusted Ventilatory Assist (NAVA) NAVA is another mode of ventilation intended to reduce asynchrony that can develop between the neonate and the ventilator.
Mechanical Ventilator Settings
In addition to determining what ventilation mode is most appropriate for a neonate, understanding the parameters and settings are critical to achieve ventilation goals while protecting the lungs, and ultimately moving toward weaning the newborn from the ventilator. Settings would include being able to change the thresholds and alarms or alerts for:
- PIP (at the end of inspiration) and the
- PEEP (at the end of expiration)
- Changing oxygenation flow and concentration and carbon dioxide (CO2) elimination
- Inspiratory Time (IT) and Expiratory
- Time (ET)
- Tidal Volume (VT)
- Oxygen Saturation
- Blood Gas Analysis
Considerations for Selecting a Mechanical Ventilator
- Safety. The key to protecting neonatal lungs during mechanical ventilation is to optimize lung volume and limit excessive lung expansion, with appropriate Positive End Expiratory Pressure (PEEP), short inspiratory time, small tidal volume (VT 4–6 mL/kg), and permissive hypercapnia. (1,4)
- Goal of Ventilation: Selecting a ventilator and appropriately skilled staff to achieve a balance in optimizing respiratory status while avoiding overventilation or excessive time on mechanical ventilation and the potential adverse effects on the newborn.
- Maintenance, consumables, and accessories. Mechanical ventilators are complex machines requiring careful preventive maintenance and the appropriate corresponding accessories and consumables for them to be appropriate for care of very ill patients.
- Integration into overall level of care. Skills and training on the appropriate use of a mechanical ventilator may not be available at all levels of a health care system, and mechanical ventilators might be more appropriate for advanced NICUs or where there are staff who have the skills to include mechanical ventilation as part of an overall system for safe respiratory care
- Modes and Settings that best enable skilled providers to deliver and adapt ventilation strategy
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References and Acknowledgments
(1) ECRI Institute. Pulse oximeters product comparison. Plymouth Meeting (PA): Emergency Care Research Institute; 4/1/2018.
(2) “WHO-UNICEF technical specifications and guidance for oxygen therapy devices.” 2019