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Overview of mechanical ventilation in neonates

Overview of mechanical ventilation in neonates
Authors:
Nicolas Bamat, MD, MSCE
Eric C Eichenwald, MD
Section Editor:
Richard Martin, MD
Deputy Editor:
Laurie Wilkie, MD, MS
Literature review current through: Apr 2022. | This topic last updated: Aug 31, 2021.

INTRODUCTION — Mechanical ventilation (MV) is a lifesaving intervention, but it also risks injury to the lungs, brain, and other organ systems. Supporting gas exchange while minimizing harm is the key therapeutic goal and challenge of MV in neonates.

This topic will review the general principles of MV in neonates and provide a broad overview of MV modes. Detailed discussion of the approach to MV in very preterm neonates (gestational age <32 weeks) is provided in a separate topic review. (See "Approach to mechanical ventilation in very preterm neonates".)

TERMINOLOGY — The following terms are used throughout this topic:

Preterm neonates – For the purposes of this topic review, preterm neonates are defined as infants born at a gestational age (GA) <35 weeks. Different degrees of prematurity are defined by GA or birth weight as detailed in the table (table 1).

Terms related to MV – Terms used to define different modes and settings for MV in neonates are summarized in the table (table 2).

Ventilator-induced lung injury (VILI) – VILI is lung injury caused by MV. It can result from exposure to excessive pressure (barotrauma), excessive stretching of the lung tissue (volutrauma), cyclic collapsing of the alveolar spaces (atelectrauma), and exposure to high fraction of inspired oxygen (FiO2). (See "Ventilator-induced lung injury".)

GENERAL PRINCIPLES

Minimizing ventilator-induced lung injury — While lifesaving, MV also can cause lung injury and impact hemodynamics, with secondary consequences on the brain and other organs. MV can cause ventilator-induced lung injury (VILI) at any age. The general measures used to minimize VILI are fairly consistent regardless of age; however, the impact of VILI and the imperative for utilizing lung-protective strategies are particularly important for preterm neonates. Bronchopulmonary dysplasia (BPD) is a common and consequential morbidity of preterm birth caused by concurrent injury and maldevelopment of the immature lungs. (See "Bronchopulmonary dysplasia: Definition, pathogenesis, and clinical features", section on 'Pathogenesis and risk factors'.)

Therapeutic strategies to support gas exchange while minimizing lung injury are key to neonatal care. These strategies include:

Avoidance of MV through preferential use of noninvasive respiratory support (eg, nasal continuous positive airway pressure [nCPAP]) when possible) (see "Management of respiratory distress syndrome in preterm infants", section on 'Early positive pressure')

Use of lung protective strategies for invasive MV when noninvasive support fails, including:

Volume-targeting that supports gas exchange while minimizing volutrauma (see 'Volume-targeted ventilation' below)

Use of positive end-expiratory pressure (PEEP) to maintain lung recruitment and avoid atelectasis (see "Approach to mechanical ventilation in very preterm neonates", section on 'Initial conventional MV settings' and "Approach to mechanical ventilation in very preterm neonates", section on 'Choice of mode')

Avoidance of high inspired oxygen levels (see "Neonatal target oxygen levels for preterm infants" and "Approach to mechanical ventilation in very preterm neonates", section on 'Gas exchange targets')

Setting targets for gas exchange that do not aim for normal levels (ie, modest permissive hypercapnia), though gas exchange targets may vary depending on the condition (see "Approach to mechanical ventilation in very preterm neonates", section on 'Gas exchange targets')

Use of high-frequency ventilation (either as oscillatory or jet ventilation) as a rescue therapy for neonates with refractory respiratory failure while on conventional mechanical ventilation (CMV) or as an initial ventilation strategy in neonates at high risk of developing VILI (see 'High-frequency ventilation (HFV)' below and "Approach to mechanical ventilation in very preterm neonates", section on 'Role of high-frequency ventilation')

Achieving gas exchange with MV — Selection of ventilator modes and settings must be tailored to meet the needs of the individual neonate. Gas exchange needs may differ between patients and within the same patient over time. This is particularly true in preterm neonates in the early postnatal period when cardiorespiratory physiology changes rapidly. Individualized assessment and frequent reassessment of the adequacy of ventilator settings is critical. The need for tailored ventilator management, however, does not negate the value of developing evidence-based practices, which can be applied as initial settings with subsequent titration.

When using CMV, the primary means of achieving ventilation (carbon dioxide [CO2] clearance) and oxygenation (uptake of oxygen [O2]) are as follows:

Ventilation – CO2 clearance is largely determined by minute ventilation, which in turn is determined by the frequency and size of breaths (ie, respiratory rate [RR] and tidal volume [Tv]). In volume-targeted modes, Tv is a setting and is controlled by the ventilator. In pressure-limited modes, Tv is determined by other settings (inspiratory pressure and inspiratory time [Ti]) and will vary depending upon lung compliance, with compliant lungs having higher Tvs at any given inspiratory driving pressure compared with less compliant lungs.

Oxygenation – Oxygenation is primarily determined by the fraction of inspired oxygen (FiO2) and the mean airway pressure (MAP). In CMV, MAP is largely determined by the set PEEP since the expiratory phase usually predominates the respiratory cycle. Other settings (ie, Tv, inspiratory pressure, and Ti) influence MAP to a lesser extent.

While it can be useful to think of ventilation and oxygenation separately, this is an oversimplification. Each ventilator setting can impact both components of gas exchange. For example, very low minute ventilation may result in poor oxygenation, and excessively low or high PEEP can impair ventilation. Ventilator settings must be considered together since they interact and work together to achieve gas exchange.

The approach to titrating high-frequency oscillatory ventilation (HFOV) and high-frequency jet ventilation (HFJV) settings to achieve adequate gas exchange is discussed separately. (See "Approach to mechanical ventilation in very preterm neonates", section on 'Initiating and titrating HFV'.)

MV IN SELECT NEONATAL CONDITIONS

Conditions related to preterm birth

Very preterm neonates — Very preterm (VPT) infants (gestational age [GA] <32 weeks) are at high risk of respiratory failure requiring MV. In these infants, respiratory distress syndrome (RDS) due to surfactant deficiency is the most common cause of respiratory failure. MV is also used for infants with apnea of prematurity with persistent clinically significant apnea despite medical therapy and noninvasive respiratory support. The approach to MV in these infants is based on volume-targeted ventilation (VTV) to limit lung injury from volutrauma, use of a target pulse oximetry saturation (SpO2) of 90 to 95 percent, and modest permissive hypercapnia. The management of MV in VPT infants is summarized in the table (table 3) and discussed in detail separately. (See "Approach to mechanical ventilation in very preterm neonates" and "Management of apnea of prematurity".)

Established bronchopulmonary dysplasia — In infants with established bronchopulmonary dysplasia (BPD) who require MV, conventional mechanical ventilation (CMV) remains the preferred approach to MV. However, infants with severe BPD may require higher Tv with progressive lung disease, as the ratio of airway dilation and dead space to Tv increase with chronic MV, which reduces effective ventilation. In these infants, higher degrees of permissive hypercapnia are commonly accepted. Management of BPD is discussed in greater detail separately. (See "Bronchopulmonary dysplasia: Management", section on 'Mechanical ventilation'.)

Other conditions

Persistent pulmonary hypertension of the newborn (PPHN) — Persistent pulmonary hypertension of the newborn (PPHN) occurs when pulmonary vascular resistance (PVR) remains abnormally elevated after birth. It can be idiopathic or associated with primary respiratory diseases such as meconium aspiration syndrome, RDS, congenital diaphragmatic hernia, or pneumonia. MV management is tailored to the needs of the individual neonate and varies depending on the underlying etiology. Management of PPHN is discussed in greater detail separately.

Meconium aspiration syndrome — Approximately one-third of neonates with meconium aspiration syndrome (MAS) require MV. The goal of initial CMV is to optimize gas exchange while minimizing ventilator-induced lung injury (VILI). Modest permissive hypercapnia is used, but pH should remain in the normal range to avoid exacerbating pulmonary hypertension, when present. We consider using high-frequency ventilation (HFV) in infants who fail to respond to CMV and pharmacologic treatment (eg, surfactant and inhaled nitric oxide [iNO]), and extracorporeal membrane oxygenation (ECMO) therapy in infants with inadequate gas exchange despite MV. Management of MAS is discussed in greater detail separately. (See "Meconium aspiration syndrome: Prevention and management", section on 'Mechanical ventilation'.)

Congenital diaphragmatic hernia — Patients with congenital diaphragmatic hernia (CDH) are typically intubated and mechanically ventilated after birth to prevent gastric distension and lung compression. The approach to MV is to use CMV with a gentle ventilation strategy that allows for permissive hypercapnia as long as pH remains >7.25 and preductal oxygen saturation targets above 85 percent. Pressure-limited ventilation is most commonly used, with a goal positive inspiratory pressure <25 cm H2O. HFV is reserved for infants who fail to achieve targeted goals on CMV, and ECMO is reserved for those who fail all modes of MV. Management of CDH is discussed in greater detail separately. (See "Congenital diaphragmatic hernia in the neonate", section on 'Ventilation'.)

Congenital heart disease — The approach to MV in neonates with critical congenital heart disease (CHD) depends on the specific lesion and the operative status (preoperative versus postoperative). For patients with ductal-dependent lesions and those who have undergone placement of a surgical shunt (eg, a stage I procedure for hypoplastic left heart syndrome with a modified Blalock-Thomas-Taussig shunt), the goals of MV are to achieve adequate gas exchange and to balance the pulmonary and systemic circulations:

For neonates with inadequate pulmonary blood flow (eg, low SpO2 and decreased pulmonary vascular markings on chest radiograph), MV interventions aim to reduce PVR through the use of higher fraction of inspired oxygen (FiO2) and larger tidal volumes (Tvs).

For neonates with excessive pulmonary blood flow (eg, high SpO2 and pulmonary congestion), MV interventions aim to increase PVR (ie, lower FiO2, smaller Tvs).

Initial management of neonates with cyanotic CHD is discussed separately. (See "Diagnosis and initial management of cyanotic heart disease in the newborn", section on 'Initial management' and "Hypoplastic left heart syndrome: Management and outcome".)

Pneumonia and other primary pulmonary conditions — For neonates who require MV for primary pulmonary conditions such as pneumonia or respiratory syncytial virus (RSV) bronchiolitis, the principles are generally the same as described above (see 'General principles' above). The goal is to support gas exchange while minimizing lung injury. We typically use volume-targeted ventilation (VTV) using synchronized intermittent mandatory ventilation plus pressure support (SIMV + PS) or assist-control ventilation (ACV). Additional details of the management of neonatal pneumonia and bronchiolitis are provided separately. (See "Neonatal pneumonia" and "Bronchiolitis in infants and children: Treatment, outcome, and prevention", section on 'Respiratory support'.)

VENTILATOR MODES — Mechanical ventilators can support gas exchange through many different modes. Broadly, ventilator types can be categorized as conventional mechanical ventilation (CMV) or high-frequency ventilation (HFV). Within each type, there are distinct subcategories or "modes" of ventilation.

Conventional mechanical ventilation (CMV) — In neonates, CMV is used more commonly than HFV. CMV comprises numerous distinct modes with different specific properties that determine how breaths are delivered. The commonality among them is that they allow for the intermittent exchange of bulk gas with tidal volumes (Tvs) and frequencies similar to physiologic breathing.

Accurate description of different CMV modes is complicated by the inconsistent use of terminology among manufacturers and clinical providers. In addition, the term "mode" may refer to one feature of the ventilator that can be flexibly combined with other features, allowing for many distinct combinations. An exhaustive description of all of the different combinations of features that make up different modes is beyond the scope of this topic. We limit our discussion to the following:

Properties that control the initiation of breaths (triggering) (see 'Synchronized modes' below)

Properties that control breath limitation (ie, volume-targeted versus pressure-limited) (see 'Breath limitation' below)

Synchronized modes — Breaths can be initiated or "triggered" by the ventilator ("mandatory" breaths) or the patient ("spontaneous" breaths). Most modern ventilators attempt to synchronize mandatory breaths with the patient's spontaneous breathing efforts, if present. Synchronized modes predominate in high-resource settings [1]. They typically use a flow sensor in the ventilator circuit to detect respiratory effort from the neonate. Synchronization is thought to improve infant comfort, lessen work of breathing, improve pulmonary mechanics and gas exchange, and facilitate earlier weaning from MV [2-8]. In a meta-analysis of five trials (1463 neonates) comparing synchronized MV (ie, synchronized intermittent mandatory ventilation [SIMV] or assist-control ventilation [ACV]) with controlled MV without synchronization, duration of MV was shorter in neonates managed with synchronized modes (mean difference 38 hours; 95% CI 21-54) [8]. Rates of mortality, intraventricular hemorrhage (IVH), and bronchopulmonary dysplasia (BPD) were similar in both groups.

Commonly used synchronized modes include the following; the superiority of one of these over another has not been established in neonates [8]:

Assist-control ventilation (ACV) – ACV provides mandatory breaths at a set rate (control breaths) and also supports spontaneous breaths above the set rate (assist breaths). ACV can be used to deliver volume-targeted or pressure-limited breaths. Breath limitation is the same regardless of whether it is an assist or control breath. (See 'Breath limitation' below.)

Pressure support ventilation (PSV) – In PSV, all breaths are triggered by the patient's spontaneous effort (ie, there is no set rate); breaths are pressure-limited. PSV alone does not allow the provider to ensure a baseline mandatory breath rate in the setting of apnea or hypopnea.

Synchronized intermittent mandatory ventilation (SIMV) – When used alone, SIMV provides only mandatory breaths (ie, spontaneous breaths above the set rate are not supported) but the ventilator attempts to synchronize breaths with the patient's spontaneous effort. It can be used to deliver volume-targeted or pressure-limited breaths.

Synchronized intermittent mandatory ventilation plus pressure support (SIMV + PS) – SIMV + PS is a combination of SIMV and pressure-support ventilation (PSV). It is similar in some ways to ACV in that it provides mandatory breaths at a set rate (SIMV breaths) and also supports spontaneous breaths above the set rate (PS breaths). Unlike ACV, the mandatory and spontaneous breaths are not the same. For example, if the SIMV component uses volume-targeted breaths, the mandatory breaths will be volume-targeted, while the spontaneous (PS) breaths will be pressure-limited. Even if both components use pressure-limited breaths with the same inspiratory pressure setting, they will differ from one another since breath termination is distinct (SIMV breaths have a set inspiratory time which determines how long the breath lasts; PS breaths terminate based upon declining flow).

One argument for using SIMV + PS rather than SIMV alone is that the PS component is thought to improve comfort and facilitate weaning, a notion that is supported by limited clinical trial data [8,9]. The largest trial involved 107 preterm neonates (birth weight 500 to 1000 g) who were randomized to SIMV + PS or SIMV at a median age of 34 hours of life [9]. After 28 days, fewer infants in the SIMV + PS group remained on MV compared with the SIMV group (47 versus 69 percent, respectively). There were nonsignificant trends towards shorter duration of supplemental oxygenation, fewer total days MV, and lower incidence of BPD in the SIMV + PS group.

Neurally-adjusted ventilatory assist (NAVA) – NAVA is a novel mode that detects electrical activity from the diaphragm and uses this signal as the trigger for spontaneous inflations. A specialized nasogastric tube with a sensor positioned within the lower esophagus is used to detect diaphragm activity. Evidence comparing NAVA with other conventional synchronized modes in preterm neonates is limited [10,11]. In a randomized trial of 60 neonates (GA 28 to 36 weeks), infants receiving NAVA had lower peak inspiratory pressures (PIP), but no improvement in Tv, oxygenation, or the duration of MV compared with synchronized time-cycled pressure-limited ventilation [11]. Smaller crossover trials report lower PIP levels with the use of NAVA, but do not consistently show improvements in gas exchange [12-14]. A major disadvantage of NAVA is that it requires specialized equipment and clinical expertise, which may preclude its use at some centers, including our own at present.

Breath limitation — Breath limitation refers to the setting controlling the size, or Tv, of the breath. Ventilator modes can control Tv using a volume-targeted or pressure-limited approach.

Volume-targeted ventilation — In volume-targeted ventilation (VTV), the desired Tv is set, and the peak inspiratory pressure (PIP) delivered to achieve it varies. Some ventilators let the clinician set upper and lower PIP limits in VTV modes providing some control over the allowable PIP range. There are different terms for VTV, including volume control (VC), volume guarantee (VG), and pressure-regulated volume control (PRVC). There are some differences among these with respect to how inspiratory flow and pressure are regulated over time, how the ventilator measures Tv, and how PIP is adjusted in response to measured Tv. Data comparing different types of VTV are limited.

Use of VTV in neonates, especially very preterm infants (gestational age <32 weeks), has increased over time as technical advances have allowed for more accurate measurement of small Tvs and better compensation for endotracheal tube (ETT) leaks. It is important to recognize that the Tv measured by a ventilator includes not only the Tv delivered to the neonate, but also the fixed instrumental dead space volume made up of the portion of the ventilator circuit distal to the flow sensor. Even with a flow sensor just above the endotracheal tube, there is still fixed instrumental dead space volume made up of the ETT and the flow sensor itself (the volume depends in part upon the size of the ETT; approximately 3 mL for a 2.5 mm ETT) [15]. The significance of this dead space is that when using VTV with a weight-based Tv target, (eg, 5 mL/kg), the proportion of the total Tv that is actually delivered to the neonate will decrease as weight decreases. This is because the instrumental dead space volume remains fixed regardless of the neonate's weight, and it accounts for a proportionally larger amount of the delivered Tv in small infants, leaving a smaller residual Tv for alveolar ventilation and gas exchange. Based on this, it is reasonable to use slightly larger initial Tv (5 to 6 mL/kg rather than 4 to 5 mL/kg) in smaller preterm neonates, particularly extremely low birth weight (ELBW, <1000 g) neonates.

Use of VTV in very preterm (VPT) neonates is discussed in greater detail separately. (See "Approach to mechanical ventilation in very preterm neonates", section on 'Choice of mode'.)

Pressure-limited ventilation — In PLV, the inspiratory pressure is set, and the size of the Tv depends on the compliance of the lungs and respiratory circuit. Pressure control (PC) is the main mode in this category. In PC, the ventilator controls both the PIP and the inspiratory time (Ti). PSV is another pressure-limited mode in which the ventilator controls the inspiratory pressure, but there is no fixed Ti setting, and breaths terminate based on declining flow. This allows the patient more control over how long each breath lasts.

Historically, PLV was the standard approach used for neonatal MV. In fact, PLV is the only mode available on many older generations of neonatal ventilators. As discussed above, technical advances have allowed for more accurate measurement of small Tvs and compensation for ETT leaks which have led to newer generations of neonatal ventilators that provide VTV as an option.

There tends to be greater breath-to-breath variability in delivered Tv with PLV compared with VTV [16]. This can be pronounced when the mechanics of the lung and respiratory circuit change dynamically, as may occur after surfactant administration, with changes in lung volume, or when the ETT is partially occluded (eg, from secretions) or has a positional leak.

However, there are some advantages to PLV:

Cost and availability – Unlike VTV, which generally requires more modern ventilators to function effectively in neonates, PLV can be used with older generations of neonatal ventilators, many of which lack a VTV option and only provide PLV. Thus, in resource-limited settings, PLV may be more widely available, less costly, and easier to use.

Less prone to error from ETT leaks – In VTV, a large ETT leak can limit the reliable delivery of the desired Tv. This is less of a problem in PLV since the delivered pressure does not depend upon the accurate measurement of Tv.

High-frequency ventilation (HFV) — High-frequency ventilation (HFV) delivers small tidal volumes (Tvs) at a rapid rate on a sustained mean airway pressure. HFV can be used either as the primary mode of MV support following endotracheal intubation ("elective" HFV therapy), or as "rescue" therapy for neonates with poor gas exchange despite efforts to optimize CMV. HFV modes are often effective in achieving pulmonary gas exchange and may be "lung-protective" relative to CMV, particularly when high settings are required to achieve adequate gas exchange (ie, they may limit lung-injury from the tissue stretch that can occur with cyclic peak inflations in CMV).

The two major forms of HFV are high-frequency oscillatory ventilation (HFOV) and high-frequency jet ventilation (HFJV). HFOV is used more commonly than HFJV. There are few data comparing the effectiveness of one with the other [17]. The general properties of each mode are as follows:

HFOV – In HFOV, a ventilator piston creates positive- and negative-pressure oscillations to deliver small Tvs on a set mean airway pressure (MAP). Expiration is an active process with HFOV (unlike CMV, in which expiration is passive). The frequencies used are typically in the range of 480 to 900 breaths per minute (8 to 15 Hz).

HFJV – HFJV uses a pinch valve to interrupt gas flow and produce small-volume pulses of gas at a high frequency, which are delivered through a port on a specialized ETT adapter. This is applied in parallel to a conventional ventilator that provides positive end-expiratory pressure (PEEP) and delivers optional intermittent "sigh breaths" (typically 2 to 10 times per minute) when additional lung recruitment is desired.

The approach to using HFOV and HFJV in very preterm (gestational age <32 weeks) neonates is discussed separately, including indications, initial settings, titration, and efficacy and disadvantages compared with CMV. (See "Approach to mechanical ventilation in very preterm neonates", section on 'Role of high-frequency ventilation' and "Approach to mechanical ventilation in very preterm neonates", section on 'Refractory respiratory failure'.)

Indications for using HFV in other neonatal conditions are discussed separately:

Persistent pulmonary hypertension of the newborn

Congenital diaphragmatic hernia (see "Congenital diaphragmatic hernia in the neonate", section on 'Type of ventilation')

Meconium aspiration syndrome (see "Meconium aspiration syndrome: Prevention and management", section on 'Mechanical ventilation')

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

Basics topic (see "Patient education: What to expect in the NICU (The Basics)")

SUMMARY AND RECOMMENDATIONS

While lifesaving, mechanical ventilation (MV) can also cause lung injury and contribute to hemodynamic instability, with secondary injury to the brain and other organ systems. The impact of ventilator-induced lung injury (VILI) and the imperative for utilizing lung-protective strategies are important considerations for neonates with respiratory failure who require MV. (See 'General principles' above.)

In neonates, therapeutic strategies to support gas exchange while minimizing VILI include (see 'Minimizing ventilator-induced lung injury' above):

Volume targeting that supports gas exchange while minimizing volutrauma

Use of positive end-expiratory pressure (PEEP) to maintain lung recruitment and avoid atelectasis

Avoidance of high inspired oxygen levels

Setting targets for gas exchange that do not aim for normal levels, when appropriate to the specific disorder

Use of high-frequency ventilation (HFV) for infants with inadequate gas exchange despite high conventional mechanical ventilation (CMV) settings

Neonatal conditions associated with a high risk of respiratory failure include the following (see 'MV in select neonatal conditions' above):

Neonatal respiratory distress syndrome primarily seen in very preterm (VPT) infants (gestational age <32 weeks) (see "Approach to mechanical ventilation in very preterm neonates" and "Management of respiratory distress syndrome in preterm infants")

Bronchopulmonary dysplasia (see "Bronchopulmonary dysplasia: Management", section on 'Mechanical ventilation')

Apnea of prematurity (see "Management of apnea of prematurity", section on 'Management overview')

Persistent pulmonary hypertension of the newborn

Meconium aspiration syndrome (see "Meconium aspiration syndrome: Prevention and management", section on 'Mechanical ventilation')

Congenital diaphragmatic hernia (see "Congenital diaphragmatic hernia in the neonate", section on 'Ventilation')

Critical congenital heart disease (see "Diagnosis and initial management of cyanotic heart disease in the newborn", section on 'Initial management' and "Hypoplastic left heart syndrome: Management and outcome")

Primary pulmonary conditions including pneumonia and respiratory syncytial virus (RSV) bronchiolitis (see "Neonatal pneumonia" and "Bronchiolitis in infants and children: Treatment, outcome, and prevention", section on 'Respiratory support')

Ventilator types can be categorized as CMV or HFV. CMV is used more commonly than HFV in neonates. Within each type, there are distinct subcategories or "modes" of ventilation. (See 'Ventilator modes' above.)

The selection of ventilator modes and settings is tailored to meet the needs of the individual neonate, recognizing that gas exchange needs may differ between patients and within the same patient over time. Individualized assessment and frequent reassessment of the adequacy of ventilator settings is critical. The general approach to achieving adequate gas exchange using CMV is based on the following (see 'Achieving gas exchange with MV' above):

Ventilation (carbon dioxide [CO2] clearance) is largely determined by minute ventilation, which is based on the frequency and size of breaths (ie, respiratory rate [RR] and tidal volume [Tv]). In volume-targeted ventilation (VTV), Tv is set and controlled by the ventilator. In pressure-limited ventilation (PLV), Tv is determined by other settings (inspiratory pressure and inspiratory time [Ti]) and will vary depending upon lung compliance.

Oxygenation (uptake of oxygen [O2]) is primarily determined by the fraction of inspired O2 (FiO2) and the mean airway pressure (MAP). In CMV, MAP is largely determined by the set PEEP.

CMV comprises numerous distinct modes with various properties, including those that control the following:

Initiation of breaths (triggering) – Breaths can be triggered by the ventilator (mandatory breaths), the patient (spontaneous breaths), or a combination of the two. For most neonates requiring MV, we suggest a synchronized mode that provides mandatory breaths and supports spontaneous breaths (ie, synchronized intermittent mandatory ventilation plus pressure support [SIMV + PS] or assist-control ventilation [ACV]) rather than only mandatory breaths (ie, SIMV alone) (Grade 2C). (See 'Synchronized modes' above.)

Breath limitation – The size of the breath can be controlled using a volume-targeted or pressure-limited approach. The choice between VTV and PLV depends on the specific condition for which the neonate requires MV. The use of VTV in VPT neonates is discussed separately. (See 'Breath limitation' above and "Approach to mechanical ventilation in very preterm neonates", section on 'Clinical approach'.)

HFV delivers small Tvs at a rapid rate on a sustained MAP. HFV modes are usually very effective in achieving pulmonary gas exchange. The two major forms of HFV are high-frequency oscillatory ventilation (HFOV) and high-frequency jet ventilation (HFJV). HFOV is used more commonly than HFJV. In our institution, HFOV is primarily used as rescue therapy for neonates who fail to achieve adequate gas exchange despite optimal CMV. (See 'High-frequency ventilation (HFV)' above.)

ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges James Adams, Jr., MD, who contributed to an earlier version of this topic review.

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