Understanding Neonatal Ventilation: Strategies for Decision Making in the NICU
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Continuing Nursing Education (CNE) Credit A total of 3.6 contact hours may be earned as CNE credit for reading the articles in this issue identifi ed as CNE and for completing an online posttest and evaluation. To be successful the learner must obtain a grade of at least 80% on the test. Test expires three (3) years from publication date. Disclosure: The author/planning committee has no relevant fi nancial interest or affi liations with any commercial interests related to the subjects discussed within this article. No commercial support or sponsorship was provided for this educational activity. ANN/ANCC does not endorse any commercial products discussed/displayed in conjunction with this educational activity. The Academy of Neonatal Nursing is accredited as a provider of continuing nursing education by the American Nurses Credentialing Center’s Commission on Accreditation. Provider, Academy of Neonatal Nursing, approved by the California Board of Registered Nursing, Provider #CEP 6261; and Florida Board of Nursing, Provider #FBN 3218, content code 2505. Understanding Neonatal Ventilation: Strategies for Decision Making in the NICU Julia Petty, BSc, MSc, PGCE, MAAP, RGN, RSCN ROVIDING RESPIRATORY SUPPORT IN THE SICK OR PRETERM support the neonate’s respiratory system in the intensive care Pneonate is a signifi cant component of the care deliv- unit. Secondly, the article will outline the factors that can ered in the neonatal unit. Many of the neonates admitted guide and assist decision making for learners in this area of to neonatal care require some practice. The reader is directed degree of mechanical ventila- to many sources for further tion. A core aim of neonatal ABSTRACT reading in this area that provide ventilation is to achieve adequate Neonatal ventilation is an integral component of care an overview of ventilation gaseous exchange without any delivered in the neonatal unit. The aim of any ventilation modes and strategies in neonatal resultant lung injury or chronic strategy is to support the neonate’s respiratory system practice. 1–13 lung disease (CLD), 1 a potential during compromise while limiting any long-term damage and signifi cant long-term effect to the lungs. Understanding the principles behind neonatal NEONATAL ventilation is essential so that health professionals caring for of prolonged mechanical ven- POSITIVE PRESSURE sick neonates and families have the necessary knowledge tilation in the neonatal period. to understand best practice. Given the range of existing VENTILATION: Understanding the complexi- ventilation modes and parameters available, these require OVERVIEW ties of care given to any neonate explanation and clarifi cation in the context of current Ventilation strategies can be requiring mechanical ventila- evidence. Many factors can infl uence clinical decision viewed across a continuum of tion is essential to deliver safe making on both an individual level and within the wider dependency starting with the and effective care. The range perspective of neonatal care. neonate who requires oxygen of modes and parameters in only, through to the fully ven- ventilation practice can pose tilated neonate requiring inten- a challenge for both the novice nurse and for those more sive care. This article will focus on the latter area; that of experienced who require an update of knowledge. The deci- positive pressure ventilation for the intensive care neonate sion to use a specifi c type of strategy depends on a complex specifi cally. interplay of factors such as the nature and progression of the Positive pressure ventilation (sometimes referred to as underlying condition, the state of the lungs, age, and ges- mechanical, mandatory, or intermittent positive pressure tation. The fi rst aim of this article is to provide the reader ventilation [IPPV]) is a term that applies to the whole spec- with an understanding of the range of strategies used to fully trum of ventilation modes that deliver pressure according to Accepted for publication March 2013. N EONATAL NETWORK 246 © 2013 Springer Publishing Company JULY/AUGUST 2013, VOL. 32, NO. 4 http://dx.doi.org/10.1891/0730-0832.32.4.246 FIGURE 1 ■ An intubated neonate receiving full ventilator support. the neonate attempting to breathe and the ventilator deliver- ing a mechanical breath. Synchronized Intermittent Mandatory Ventilation (SIMV) SIMV delivers a predetermined number of breaths per minute (BPM), but the breaths are triggered by detecting the neonate’s spontaneous breathing efforts and synchronizing the delivery of the ventilator breaths to match the neonate’s own breaths. 2–4,6,7,13 In SIMV, the neonate can take addi- tional spontaneous breaths between the ventilator-assisted breaths. SIMV can be used to wean the ventilator support and move toward extubation by reducing the preset rate and pressure over time. If a neonate has a high respiratory rate, it is challenging for him to fi t all his own breaths along with those set as backup into one minute, unless the inspiratory time (IT ) is minimal (less than 0.4 seconds; see later section). This mode is a widely used choice in neonatal practice.5 Patient Trigger Ventilation (PTV) parameters set on a ventilator. It is used for full respiratory or “Assist Control” (A/C) support in neonates who have undergone endotracheal intu- For this mode, each time the neonate starts to breathe, bation (Figure 1) and are unable to self-ventilate adequately this triggers the ventilator to deliver a breath or assist the and where noninvasive methods such as continuous posi- neonate’s breath at a set pressure and IT . Therefore, the rate tive airway pressure (CPAP) are not suffi cient to maintain delivered and recorded is determined by the neonate. If the adequate respiratory function. Full ventilation includes fi rstly neonate becomes apneic and does not trigger a breath, the “conventional” modes that aim to mimic the normal respi- ventilator will deliver the set backup rate, again with the ratory cycle and are based on traditional pressure-limited, predetermined pressure and IT . This mode can also be used time-cycled ventilators.11 More recently, “nonconventional” to wean from ventilation support by reducing pressure only, and newer modes of mechanical ventilation have been intro- because rate is controlled by the neonate. A meta-analysis14 duced, including pressure support, volume targeting, and comprising 14 studies concluded that triggered ventilation high-frequency oscillation. 2 Adjunct therapies such as inhaled leads to a shorter duration of ventilation overall as well as nitric oxide (NO) and extracorporeal membrane oxygenation a reduction in air leaks compared with mandatory conven- (ECMO) that are used as “rescue” therapies for specifi c cases tional ventilation. Another recent randomized, crossover trial are beyond the scope of this article. of 26 stable preterm neonates with a mean gestational age of 27 weeks found that a reduced backup rate (30 BPM com- VENTILATOR MODES pared with 50 BPM) resulted in greater triggering of breaths The terminology used to identify modes of ventilation and no discernible difference in cardiovascular stability. 15 may differ between makes and models of different venti- Supporting a neonate’s own respiratory efforts should there- lators. The reader should refer to Table 1 for explanations fore be encouraged by the use of triggered ventilation with of ventilator terminology and relevant formulas referred to an optimum backup rate while allowing him to take control throughout this article. In addition, Case Studies 1 through of his own breathing in time. 3 provide examples of ventilator modes and the rationale for selecting them based on the individual pathophysiology and Target Tidal Volume (TTV) or Volume Guarantee (VG) assessment. TTV or VG can be added to either SIMV, PTV, or A/C. A desired tidal volume (VT ) is set by the operator and delivered Continuous Mandatory Ventilation (CMV) by the ventilator using the lowest possible pressure necessary This term refers to mandatory ventilation with a contin- to reach the set volume. A further explanation of VT follows uous fl ow of gases, where the neonate can attempt to take later in the article and within Table 1. TTV or VG ensures 9,10,12 spontaneous breaths between ventilator breaths. With that the neonate receives an optimal VT but at minimal pres- CMV, the ventilator will deliver a breath regardless of the sures to avoid the risk of barotrauma 8 and volutrauma to neonate’s efforts, leading to the potential for asynchronous the lungs. It should be remembered that the measured peak ventilation between the neonate and the ventilator. This inspiratory pressure (PIP) is likely to vary with each breath mode is used for neonates who require maximum support particularly as the lung compliance changes; in other words, in the presence of little or no spontaneous effort or where how easy or not it is to expand the lung. For example, as breathing should be minimal to avoid “asynchrony” between the lung compliance worsens, the desired VT will be more N EONATAL NETWORK VOL. 32, NO. 4, JULY/AUGUST 2013 247 TABLE 1 ■ Ventilation Terminology, Definitions, and Useful Formulas49,59,60 Parameter Definition Formula if Applicable and Further Information Parameters that influence adequate ventilation status Fraction of inspired oxygen How much oxygen is delivered—expressed as a Multiply FiO2 by 100 to calculate the percentage ϭ (FiO2) fraction of 1. Can also be expressed as a percentage. oxygen delivered (e.g., FiO2 of 1 100% oxygen) ϭ FiO2 of 0.3 30% oxygen Mean