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New modes of mechanical ventilation in the preterm newborn: evidence of benefit
  1. Nelson Claure,
  2. Eduardo Bancalari
  1. Division of Neonatology, Department of Pediatrics, University of Miami Miller School of Medicine, Miami, USA
  1. Eduardo Bancalari, PO Box 016960 R-131, Miami, FL 33101, USA; EBancalari{at}miami.edu

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The introduction of modern mechanical ventilation in neonatal medicine in the 1960s was followed shortly thereafter by its use in premature infants with hyaline membrane disease. Most premature infants born before 30 weeks’ gestation receive some form of respiratory support, particularly those with fewer weeks of gestation.1 Although mechanical ventilation is frequently a life-saving therapy, its use increases the risk of lung injury, particularly in preterm infants in whom the incidence of bronchopulmonary dysplasia (BPD) remains high.2

Before the current generation of neonatal ventilators, conventional mechanical ventilation (CMV) was provided mainly with time-cycled pressure limited (TCPL) ventilators developed from adaptation of Ayre’s T piece.3 This method, also known as intermittent mandatory ventilation (IMV), was and probably still is in many centres, the most common mode of ventilation.

During IMV mechanical breaths of fixed duration are delivered at predetermined time intervals. This frequently leads to asynchrony depending on the phase of the spontaneous breath when these IMV breaths are delivered. Inspiratory asynchrony occurring when a mechanical breath is delivered at the end of and extends beyond spontaneous inspiration can produce an inspiratory hold that limits the spontaneous respiratory rate or results in excessive lung inflation. Expiratory asynchrony occurring when a mechanical breath is delivered during exhalation can delay lung deflation and elicit active expiratory efforts against positive pressure producing large fluctuations in intrathoracic pressure. Asynchrony can affect gas exchange, and has been linked to increased risk of air leaks4 5 and intraventricular haemorrhage (IVH).6 As volume monitoring was lacking in most IMV devices, it was difficult to detect excessive lung inflation, gas trapping or hypoventilation.

SYNCHRONISED MECHANICAL VENTILATION

Advances in ventilator technology allowed mechanical breaths to be synchronised with the onset of spontaneous inspiration. This was achieved by using signals derived from spontaneous respiratory activity. Synchronisation was also extended …

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Footnotes

  • Competing interests: Viasys Healthcare, Draeger Medical, Tyco Healthcare Puritan Bennett and Maquet Inc. support an annual post-graduate educational event at the University of Miami. The University of Miami and Drs Bancalari and Claure have a patent licensing agreement with Viasys Healthcare unrelated to the material discussed here.

  • Abbreviations:
    A/C
    assist/control ventilation
    BPD
    bronchopulmonary dysplasia
    CMV
    conventional mechanical ventilation
    CTGI
    continuous tracheal gas insufflation
    ET
    endotracheal tube
    IMV
    intermittent mandatory ventilation
    IVH
    intraventricular haemorrhage
    MMV
    mandatory minute ventilation
    N-A/C
    nasal A/C
    NCPAP
    nasal continuous positive airway pressure
    N-SIMV
    nasal SIMV
    PAV
    proportional assist ventilation
    PIP
    automated peak inspiratory pressure
    PRVC
    pressure-regulated volume-controlled
    PSV
    pressure support ventilation
    PTV
    patient triggered ventilation
    RDS
    respiratory distress syndrome
    SIMV
    synchronised intermittent mandatory ventilation
    SIPPV
    synchronised IPPV
    TCPL
    time-cycled pressure limited
    VAPS
    volume-assured pressure-support
    VC
    volume controlled ventilator
    VG
    volume guarantee ventilator
    VT
    tidal volume

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