|Year : 2017 | Volume
| Issue : 2 | Page : 57-63
Mechanical ventilation in newborn infants: Clinical practice guidelines of the Saudi Neonatology Society
Fahad Nasser Al Hazzani1, Khalid Al Hussein2, Saleh Al Alaiyan1, Saad Al Saedi3, Khalid Al Faleh4, Fahad Al Harbi5, Zakariya Al-Salam6, Sameer Yaseen Al Abdi7, Aziza S Al Harbi8, Abbas Al Omran9, Mahasen Azzouz10
1 Department of Pediatrics, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
2 Department of Pediatrics, Security Forces Hospital, Riyadh, Saudi Arabia
3 Department of Pediatrics, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia
4 Department of Pediatrics, College of Medicine, King Saud University, Riyadh, Saudi Arabia
5 Department of Pediatrics, Neonatal Intensive Care Unit, Al Takhassusi Hospital, Dr. Suliman Al Habib Medical Group, Riyadh, Saudi Arabia
6 Department of Pediatrics and Neonatology, Oasis Hospital, Al Ain, Unite Arab Emirates
7 Department of Pediatrics, King Abdulaziz Hospital, Ministry of National Guard, Al Ahsa, Saudi Arabia
8 Department of Pediatrics, Madina Maternity and Children Hospital, Al-Madinah Al-Munawarah, Saudi Arabia
9 Department of Pediatrics, AlMana Genereal Hospital, Al Ahsa, Saudi Arabia
10 Department of Pediatrics, Maternity and Children Hospital, Jeddah, Saudi Arabia
|Date of Web Publication||13-Apr-2017|
Fahad Nasser Al Hazzani
Department of Pediatrics, King Faisal Specialist Hospital and Research Centre, Riyadh
Source of Support: None, Conflict of Interest: None
Mechanical ventilation is one of the most common therapies in the neonatal intensive care unit (NICU), it is an area where technical complexity overlap individual preferences due to lack of extensive scientific evidence. Our aim is to provide clinical practice guidelines for conventional mechanical ventilation of newborn infants, utilizing the best available scientific evidence and to address the controversies. These guidelines are meant to help the clinician in managing ventilated newborn infants; it should not replace clinical judgment.
Keywords: Infant, mechanical ventilation, newborn, preterm, very low birth weight infants
|How to cite this article:|
Al Hazzani FN, Al Hussein K, Al Alaiyan S, Al Saedi S, Al Faleh K, Al Harbi F, Al-Salam Z, Al Abdi SY, Al Harbi AS, Al Omran A, Azzouz M. Mechanical ventilation in newborn infants: Clinical practice guidelines of the Saudi Neonatology Society. J Clin Neonatol 2017;6:57-63
|How to cite this URL:|
Al Hazzani FN, Al Hussein K, Al Alaiyan S, Al Saedi S, Al Faleh K, Al Harbi F, Al-Salam Z, Al Abdi SY, Al Harbi AS, Al Omran A, Azzouz M. Mechanical ventilation in newborn infants: Clinical practice guidelines of the Saudi Neonatology Society. J Clin Neonatol [serial online] 2017 [cited 2017 Jun 25];6:57-63. Available from: http://www.jcnonweb.com/text.asp?2017/6/2/57/204509
| Introduction|| |
Mechanical ventilation is one of the most common therapies in the neonatal Intensive Care Unit and is associated with increased morbidity and mortality. The management of infants receiving mechanical ventilation remains largely dependent on individual preferences. Mechanical ventilation is a complex and highly specialized area of neonatology, made more complicated by the availability of many different modes, techniques, and devices. In the face of a lack of clear scientific evidence for many aspects of mechanical ventilation in preterm infants, achieving consensus may not be easy.
The development and implementation of mechanical ventilation protocols are well supported in the adult literature and have been recommended by the American College of Chest Physician and the American College of Critical Care Medicine. In neonates, only one single-center retrospective study evaluated the impact of a ventilation protocol on the respiratory outcomes of preterm infants born with birth weight <1250 g. In that center, the implementation of a respiratory therapist-driven protocol was associated with earlier extubation, decreased rate of extubation failure, and shorter duration mechanical ventilation, without any reported side effect.
| Objectives|| |
- To provide clinical practice guidelines for conventional mechanical ventilation of newborn infants, utilizing the best available scientific evidence
- To address the controversial issue related to mechanical ventilation.
| Scope of the Guidelines|| |
- The guidelines address the conventional mechanical ventilation of newborn infants for various disease processes in preterm and term infants
- Other forms of ventilation such as high-frequency oscillatory ventilation and noninvasive ventilation will be covered in a separate clinical practice guidelines
- Delivery room care is covered by separate clinical guidelines
- Guidelines are meant to help the clinician in managing ventilated infants; it should not replace clinical judgment
- The guidelines do not endorse the use of any commercial device or any specific type of ventilator.
| List of Abbreviations|| |
The following explains the terminology used in the guidelines:
- PIP: Peak inspiratory pressure
- PEEP: Positive end-expiratory pressure
- MAP: Mean airway pressure
- VT: Tidal volume
- RR: Respiratory rate
- Ti: Inspiratory times
- Te: Expiratory time
- AC: Assist-control mode
- IMV: Intermittent mandatory ventilation
- SIMV: Synchronized intermittent mandatory ventilation
- PLV: Pressure-limited ventilation
- PC: Pressure control mode
- PS: Pressure support mode
- VTV: Volume-targeted ventilation
- VC: Volume control mode
- VG: Volume guarantee mode
- PRVC: Pressure-regulated volume control mode
- ETT: Endotracheal tube
- RDS: Respiratory distress syndrome
- PPHN: Persistent pulmonary hypertension of the newborn.
| Choice of Basic Synchronized Ventilation Mode|| |
The three basic synchronization modes are assist/control (AC), pressure support ventilation (PSV), or synchronized intermittent mandatory ventilation (SIMV).
AC results in more even tidal volume (VT), lower work of breathing, and more rapid weaning from mechanical ventilation compared to SIMV. PSV provides more complete synchronization because it is flow cycled, thus avoiding inspiratory hold, but may result in very short inspiratory time (Ti) and rapid respiratory rate in very small infants in the first few days of life when time constants are very short. Because the short Ti results in relatively low mean airway pressure (MAP), adequate positive end-expiratory pressure (PEEP) must be used with PSV to avoid atelectasis.
During weaning process in AC mode, reduction in ventilator rate has no impact on minute ventilation if the infant breathes above the control rate; primary weaning parameter is peak inspiratory pressure (PIP) or VT. It is preferable to switch to SIMV mode during weaning process or to SIMV combined with PSV.
In AC mode, the Ti is fixed; this can lead to a very short expiratory time at high respiratory rates with resultant incomplete expiration and air trapping (auto-PEEP).
| Volume Preset Ventilator Versus Pressure Preset Ventilators|| |
Volume preset ventilators deliver the same VT of gas with each breath, regardless of the inflating pressure that is needed. Pressure preset ventilators, in contrast, are designed to deliver a volume of gas with each breath until a preset limiting pressure designated by the physician is reached. The remainder of volume in the unit is then released into the atmosphere. As a result, the VT that is delivered to the patient by pressure preset ventilators with each breath may be variable, but the peak pressure delivered to the airway remains constant.
| The Choice of Volume-Targeted Versus Pressure-Limited Ventilation|| |
Pressure-limited ventilation (PLV) became the standard of care early in the history of neonatal respiratory support because of its ease of use and ability to cope with large leaks around uncuffed endotracheal tubes (ETTs). The main disadvantage of PLV is the risk of volutrauma and inadvertent over ventilation when lung compliance improves as often happens soon after birth when lung fluid is cleared, surfactant is administered and optimal lung volume is achieved. Volume-controlled (VC) ventilation as implemented on available universal ventilators (neonatal to adult population) controls the VT delivered into the proximal end of the ventilator circuit, not the VT delivered to the patient. The loss of volume to compression of gas in the circuit and humidifier and to ETT leak may be 75% or more of the total, making standard VC ventilation difficult to use effectively in small newborn infants.
Volume guarantee (VG) is one of the several modes of volume-targeted pressure-limited ventilation. These modes control delivered VT indirectly by adjusting either the inflation time (volume limit) or inflation pressure (VG) to target a user-selected target VT. In VG, the microprocessor compares exhaled VT of the previous breath to the desired target and adjusts the working pressure up or down to achieve the target VT. Thus, inflation pressure is reduced continuously, in real time, rather than intermittently in response to blood gas measurement.
It is very important to know that VG ventilation does not work properly in the presence of significant ETT leak; in such case, a pressure-limited mode should be used.
A recent Cochrane review demonstrated that the use of volume-targeted ventilation (VTV) modes as compared to PLV resulted in a reduction in the combined outcome of death or bronchopulmonary dysplasia (BPD), pneumothorax, days of ventilation, hypocarbia, and the combined outcome of periventricular leukomalacia or grade 3–4 intraventricular hemorrhage.
| Technical Issues with Volume-Targeted Ventilation|| |
In the presence of large leak around the ETT, then VTV might not work properly. In case of major tube leakage, the actual VT in the patient's lungs can (as in other ventilation modes also) be larger than the VT measured on the expiratory side. Then, the inspiratory and expiratory tidal volumes are different.
It is important to understand that different mechanical ventilators use different mechanisms to deliver target volume and to compensate for the leak.
The clinician should refer to the ventilator manual to understand the followings:
- Where is the VT measured? Measuring VT at the tip of ETT is more accurate than measuring VT at the ventilator box (which will include the circuit volume)
- Does the ventilator measure the Inspiratory tidal volume (VTi) or expiratory tidal volume (VTe); in some ventilators using the neonate patient category, the VT measured on the expiratory side is taken as a basis for the control. While in the pediatric patient category, the VTi is used
- What is the mechanism by which the ventilator compensates for the leak? Most modern ventilators provide the option of using a leak compensation algorithm to offset this problem. Some ventilators can compensate for 15%–20% of the leak while others may compensate up to 50% of the leak
- What is the volume of flow sensor used? Flow sensor represents a part of the dead space; standard neonatal flow sensor is about 0.9 ml (generally <1.3 ml). Long ETT contributes to the dead space also; ETT can be cut short to decrease such dead space
- What is the scale used for flow sensor trigger sensitivity? This could be an arbitrary scale from 1 to 10. 1 is the most sensitive setting, corresponds to a flow trigger at 0.2 L/min with no minimum volume required, or the trigger sensitivity could be a set value in liter per minutes and the most sensitive setting (0.2 L/min).
| Modalities of Volume-Targeted Ventilation|| |
Volume guarantees ventilation
This modality consists of automatic adjustments to PIP aimed at maintaining the measured exhaled VT at a target level to compensate for changes in lung mechanics and spontaneous breathing effort. The PIP for the next breath is adjusted based on the difference between the target and measured exhaled VT from previous breaths. Proximal measurements of exhaled VT help in circumventing the effects of inspiratory leaks and gas compression in the circuit.
Pressure-regulated volume control
In this modality, PIP is automatically regulated to deliver a set volume in the A/C mode. A diagnostic VC breath is used to calculate respiratory compliance. Subsequently, PIP is adjusted stepwise based on volume measurements obtained by internal flow sensors during the inspiratory phase of prior breaths. In preterm infants, pressure-regulated volume control may be limited by the accuracy of internally measured volumes. Although circuit compliance compensation methods appear to be effective, these have not been tested in small preterm infants. Furthermore, measurements of inspired volume may overestimate VT in the presence of leaks around the ETT.
Targeted tidal volume mode
In the targeted tidal volume (TTV) mode, a ventilator delivers gas of a set VT. During TTV, an inspiratory pressure and an Ti are adjusted so that a VT of each breath will reach the target VTe. In some older ventilators, the target was not VTe but VTi and a significant gap often occurred between the setting and VTe when there was a leakage. In newer ventilators, a function of leak compensation within a range of 0%–20% is added in the TTVplus mode. While there is a leak, a unit increases an VTi up to 20% and compensates the leak.
| Suggested Settings for Volume Guarantee Ventilation|| |
Inflation pressure limit should initially be set 3–5 cm H2O above the level estimated to be sufficient to achieve a normal VT. If the target VT cannot be reached with this setting, the pressure limit is increased until the desired VT is generated. It is important to make sure that the ETT is not kinked, is in the main stem bronchus or obstructed on the carina. Significant volutrauma and/or air leak could result from failure to recognize single-lung intubation. Pressure limit is subsequently adjusted to be about 20% above the current working pressure and adjusted periodically as lung compliance improves and working pressure comes down. If the ventilator is unable to reach the target VT with the set inflation pressure limit, an alarm will sound. This serves as an early warning system that should prompt an evaluation of the reason for this change.
The following settings are recommended when using VG ventilation:
- VT target should be 4–6 cc/kg
- Pressure limit: 20–22 cm H2O for small infants and 25–28 cm H2O for large infants.
| Selecting Optimal Positive End-Expiratory Pressure|| |
PEEP should be set in proportion to the current oxygen requirement because hypoxemia is usually a reflection of ventilation–perfusion mismatch due to atelectasis and low lung volume. Therefore, using a PEEP of 5 cm H2O for all infants with respiratory distress syndrome (RDS) is not optimal for oxygenation and lung recruitment.
Using high PEEP may lead to lung hyperinflation, air leak, pneumothorax, decrease cardiac venous return, as well as higher PaCO2 (as VT will be lower). Using low PEEP may lead to lung hypoinflation, lung collapse, and increase requirement for FiO2.
We recommend starting with a PEEP of 5–6 cm H2O. PEEP should be increased gradually up to 8 cm H2O if the FiO2 is more than 0.30 and/or there is evidence of low lung volume on chest X-ray.
| Pressure-Targeted Modalities|| |
Pressure-targeted modalities are characterized by limiting the amount of pressure that can be delivered during inspiration. The clinician sets the maximum pressure, and the ventilator does not exceed this level. The volume of gas delivered to the infant varies according to lung compliance and the degree of synchronization between the infant and the ventilator. If compliance is low, less volume is delivered than if compliance is high. In intermittent mandatory ventilation, VT fluctuates depending on whether the infant is breathing with the ventilator or against it. There are three main pressure-targeted modalities: Pressure limited ventilation (PLV), pressure control ventilation (PCV), and PSV, which is also a mode [Table 1].
All three are pressure limited. Some devices allow both PLV and PCV to be time or flow cycled. PSV is flow cycled but time limited. Inspiratory flow during PLV is continuous and is set by the clinician. During both PCV and PSV, inspiratory flow is variable and is related to lung mechanics and patient effort. It accelerates rapidly early in inspiration, then decelerates quickly, producing a characteristic waveform.
PCV was recently introduced into neonatal ventilators. It differs from PLV primarily in the manner in which flow is regulated. This produces a waveform that accelerates then decelerates rapidly. A rapid rise in flow early in inspiration leads to earlier pressurization of the ventilator circuit and delivery of gas to the infant early in inspiration. Intuitively, this should be beneficial in disease states characterized by homogeneity and the need for a higher opening pressure, such as RDS. Variable flow should be advantageous when resistance is high, such as when a small ETT is used. The relative novelty of PCV has thus far precluded adequate comparison to PLV.
As discussed previously, VTV is better for preterm infants than pressure-targeted ventilation (except if there is a major ETT leak).
| Pressure Support Ventilation|| |
PSV is used mainly as a weaning mode.
Pressure support (PS) is a patient-triggered, pressure-limited, flow-cycled mode of ventilation designed to assist an infant's spontaneous effort with an inspiratory pressure “boost.” PS can be used in conjunction with other modes, such as SIMV, or it can be applied independently. Most neonatal pressure–support systems are flow triggered. It is important to recognize that in PSV, the Ti is set by the infant (not the ventilator). The clinician can control the max Ti to avoid long inspiration.
To set an appropriate PS level, select a value between the difference of PIP and PEEP, for example, if PIP is 18, PEEP is 6, then give a PS between 6 and 11 cm H2O; assessment of work of breathing, blood gas, and chest X-ray should be used to choose the most appropriate level.
Different ventilators display the PS value differently; some ventilators display the “actual value” of PS while other ventilators display the PS value “above PEEP.”
| Setting Inspiratory Time|| |
An Ti as long as 3–5 times constants (a measure of how rapidly gas can get in and out of the lungs) allows relatively complete inspiration. Selection of Ti with AC should reflect the infant's time constants. Small preterm infants with RDS have very short time constants and should be ventilated with Ti of 0.35 s or less. Larger infants or those with increased airway resistance (e.g., chronic lung disease or meconium aspiration) have longer time constants and require longer Ti up to 0.5 s. PSV is a flow-cycled mode that results in automatic adjustment of effective Ti in response to the infant's changing lung mechanics. PSV is preferred in most infants, with the exception of those <1 kg during the first 2–3 days of life when their time constants are very short. During PSV, the maximum Ti should be set at about 0.4 s in preterm infants, longer in term infants, and those with increased airway resistance.
| Setting the Respiratory Rate|| |
In SIMV mode: Use a high rate, especially in premature infant with RDS. In A/C or PSV mode: Use backup rate of 30–40, so there is enough room for the infant to trigger the ventilator.
If SIMV is used at a low rate, then it is advisable to add PSV to decrease the work of breathing. Additional settings are provided in the appendix[Additional file 1] .
| Suggested Blood Gas Targets|| |
Suggested initial ventilatory settings and blood gas targets are summarized in [Table 2].
|Table 2: Suggested Initial Ventilatory Strategies for Common Neonatal Respiratory Disorders|
Click here to view
| Extubation|| |
It is important to recognize that extubation is a critical transitional time, and many infants can experience significant problems during this process. Therefore, for the extreme preterm infant, we recommend the presence of senior staff experienced in intubation.
|Table 3: Desired blood gas goal and corresponding ventilator parameter changes|
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In a preterm infant, extubation should be attempted when:
- FiO2 is <0.35
- PaCO2 is <55 mm Hg
- Ventilator rate is 15–20
- MAP <8 cm H2O
- Adequate spontaneous respiratory effort without excessive work of breathing on the current settings
- Methylxanthines are already started.
| Summary of Recommendations|| |
- Mechanical ventilation should be managed by a skilled clinician with good expertise in the care of newborn infants
- The principles of neonatal resuscitation program should be followed in relation to equipment, ETT size, and stabilization
- Clinicians should be familiar with the specific type of mechanical ventilators that are used in their units. The knowledge should include and not limited to the modes of ventilation and the algorithms used for leak compensation. The ventilator manual should be reviewed carefully before use
- VTV is superior to PLV in preterm infants (in the absence of large ETT leak)
- VG ventilation mode is available in most neonatal ventilators. Suggested initial settings are:
- VT target should be 4-6 cc/kg
- Pressure limit: 20–22 cm H2O for a small infant and 25–28 cm H2O for a large infant
- In the presence of large ETT leak, PLV should be used
- Use the lowest effective PIP to maintain adequate gas exchange and avoid volutrauma
- PEEP should be set at 5–6 cm H2O. If the FiO2 is more than 0.30 and/or if there is evidence of low lung volume on chest X-ray, then the PEEP should be increased gradually up to 8 cm
- A short Ti of 0.35 s or less should be used for preterm infants. A longer Ti (up to 0.5 s) should be used for infants with increased airway resistance such as: BPD or meconium aspiration syndrome
- Suggested initial ventilatory strategies for common neonatal respiratory disorders are provided in [Table 2].
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Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]