Volume-Limited and Volume-Targeted Ventilation
Section snippets
Background
When pediatricians first started ventilating babies in the early 1970s there were no ventilators that were capable of delivering accurate tidal volumes to neonates, especially preterm neonates. Those that did deliver a tidal volume only delivered a set tidal volume into the entire ventilatory circuit, which included the baby. The volume of the ventilator circuit per se was several times greater than the volume of the baby's lungs, therefore much of the volume leaving the ventilator was lost by
Indications for mechanical ventilation of a neonate
When considering whether VTV is the appropriate mode for ventilating neonates, it is important to consider the indications for mechanical ventilation in this population. The 3 main reasons to ventilate neonates are: (1) the infant is apneic and needs positive pressure ventilation; (2) the infant has developed respiratory failure, defined by a high and rising arterial CO2 (Paco2) level; and (3) the infant has inadequate oxygenation. However, improving oxygenation in a spontaneously breathing
Physiologic principles of neonatal ventilation
Achievement of adequate oxygenation does not require gas to move regularly in and out of the lungs and so does not need rhythmic ventilation. Three factors control oxygenation.
- 1.
Oxygenation is proportional to the exposed alveolar surface area. If the lung volume is abnormally low, oxygenation will also be low. Improving lung volume improves oxygenation. Applying a positive pressure to the lungs by altering the positive end-expiratory pressure (PEEP) if the infant is ventilated, or continuous
Why use volume-targeted ventilation rather than PLV?
PLV was used for many years because it was the only mode of ventilation available. With PLV, a PIP is used to push a tidal volume into the lungs. However, a set PIP will not produce a specific tidal volume, because the size of the tidal volume will depend on how much the baby breathes and contributes to the tidal volume,9 the amount of ETT leak, and the compliance and resistance of the lungs. The major problem with using PLV is that these can vary from breath to breath especially in an infant
How do volume-targeted ventilators control the tidal volume?
All of the author’s experience with VTV has been gathered through using the Dräger Babylog 8000 (Dräger, Lübeck, Germany) in the volume guarantee mode.9, 21, 22, 23, 24, 25, 26 The author does not have experience of using volume targeting with other neonatal ventilators, so what is written about them here has been gleaned from reading articles and manufacturers’ literature and talking to neonatologists who use such ventilators. A problem is that the myriad of neonatal ventilators delivering VTV
How accurate is the tidal volume?
There are several reports about the accuracy of VTV.6, 7, 9 McCallion and colleagues9 studied the tidal volumes delivered to ventilated preterm babies with both triggered and untriggered inflations during volume guarantee ventilation with the Dräger Babylog. On average, both triggered and untriggered inflations were found to be almost identical to the set target expired tidal volume; however, there was a wide variation from 0% to 300% of the set volume. On careful examination of detailed
When should volume targeting be used?
VTV can be very useful as soon as mechanical ventilation is started, because all the clinician has to do is set the tidal volume to approximately 5 mL/kg and the ventilator will adjust its settings to try and ensure that the set volume is delivered. Using this method results in much better control of Paco2 and tidal volume than using a set PIP, observing the chest-wall movement and intermittent blood gases.
VTV can also be useful when surfactant is given because surfactant has been shown to
Cochrane review of tidal volume–targeted ventilation
A Cochrane systematic review of volume-targeted ventilation was published in 201021 and summarized in Neonatology.30 It included all 9 randomized trials comparing VTV with PLV (Fig. 1) and excluded crossover studies, which only assessed short-term outcomes.6, 14, 31, 32, 33, 34, 35, 36, 37, 38 It included trials using several ventilators and modes. Three used the Siemens Servo 300 (Siemens, Erlangen, Germany) pressure-regulated volume control mode, which controls inflating tidal volume at the
Summary
Volume-targeted ventilation is physiologically more logical than pressure-limited ventilation and is associated with a reduced risk of pneumothorax, hypocarbia, duration of ventilation, death or bronchopulmonary dysplasia, and severe intraventricular hemorrhage. It should now be adopted as the main mode for mechanical ventilation of preterm neonates.
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Cited by (21)
Technology in the delivery room supporting the neonatal healthcare provider's task
2022, Seminars in Fetal and Neonatal MedicineCitation Excerpt :However, due to rapidly changing pulmonary physiology and inconsistent respiratory drive of infants at birth, variable tidal volume are administered that might be inadequate or excessive. Large tidal volumes could overstretch the delicate alveoli and airways (volutrauma), while small tidal volumes could lead to loss of lung volume or cycling between collapse and recruitment (atelectotrauma) thereby injuring the lungs [87,88]. A recent multicentre trial evaluating tidal volume monitoring during manual ventilation reported that, despite using a respiratory function monitor (RFM) (Fig. 2), ineffective ventilation <4 mL/kg and potentially harmful ventilation >8 mL/kg was provided 40.7% and 20.0% of the time, respectively [89].
Management of the infant with bronchopulmonary dysplasia
2022, Goldsmith's Assisted Ventilation of the Neonate: An Evidence-Based Approach to Newborn Respiratory Care, Seventh EditionSmaller facemasks for positive pressure ventilation in preterm infants: A randomised trial
2019, ResuscitationCitation Excerpt :Other studies of preterm PPV in the delivery room have reported expired tidal volumes of 5.7–8.7 ml/kg.6,8–10 During PPV, tidal volume is proportional to peak inspiratory pressure and lung compliance.32 Although lung compliance was not measured in this study, we hypothesise that these infants had a higher lung compliance than those in the delivery room and that the peak inspiratory pressure of 25 cm H2O used in the study therefore resulted in higher tidal volumes than expected, despite the leak observed.
Pathophysiology of Ventilator-Dependent Infants
2017, Fetal and Neonatal Physiology, 2-Volume SetManagement of the Infant with Bronchopulmonary Dysplasia
2017, Assisted Ventilation of the Neonate: An Evidence-Based Approach to Newborn Respiratory Care: Sixth Edition
Disclosures: The author is Consultant to Fisher and Paykel Healthcare, Laerdal Global Health, and Dräger Medical.