Mechanical Ventilation: Pediatric Volume Mode (Respiratory Therapy)

ALERT

Mechanical ventilation has inherent risks, including infection, barotrauma, volutrauma, bronchopulmonary dysplasia, and lung injury.

Increased levels of supplemental oxygen during mechanical ventilation can result in retinopathy of prematurity and lung injury from excessive arterial oxygen levels.

OVERVIEW

Conventional modes of mechanical ventilation provide positive pressure ventilation (PPV) to improve oxygenation and ventilation, prevent cardiovascular failure, manage intracranial pressure, protect the airways, and improve oxygen delivery to the tissues. Volume-targeted ventilation (VTV) aims to produce a more stable tidal volume (VT) to reduce lung damage and stabilize the partial pressure of carbon dioxide (PCO₂).^{undefined#ref3">3}

Most conventional ventilators are equipped with graphics that enable the practitioner to understand how the lung is responding to treatment. Changes in mechanical ventilation should be made in response to the patient’s status.

The respiratory therapist (RT) must use critical thinking skills around these key factors related to mechanical ventilation:

• Lung volumes and capacities
• Differences in lung volumes for infants and children
• Interface between volume and pressure for the thorax, lungs, and chest wall for adults and infants
• Physiologic concepts of lung mechanics that interface with the ventilator
• How and when to make ventilator adjustments to improve oxygenation and ventilation

Additional facts about PPV include:

• Mean airway pressure (MAP) is computed using various ventilator variables. It depends on peak inspiratory pressure (PIP), positive end-expiratory pressure (PEEP), inspiratory time and flow. Ventilator waveform graphics can be used to determine the MAP.¹
• Normal glottic closure at end exhalation is prevented by an endotracheal (ET) tube; therefore, a minimal PEEP maintains physiologic functional residual capacity (FRC) in pediatric patients.
• A goal for the use of PEEP is to reduce the fraction of inspired oxygen (FIO₂) to maintain an adequate partial pressure of arterial oxygen (PaCO₂) range. In pediatric patients with pulmonary disease, PEEP is adjusted according to underlying pathophysiology.
• Mechanical ventilators can be used in a volume or pressure mode as well as hybrid variations that combine aspects of both modes.
• The potential complications with mechanical ventilation include decreased cardiac output and increased intracranial pressure.

Although an appropriate PEEP level may result in clinical benefits, both inappropriately low and high levels may cause harm. An appropriate PEEP level may be best achieved by an individualized approach, based on the patient’s disease process. PEEP should be set at the lowest level to achieve an acceptable level of PaCO₂ within a lung-protective strategy. An open-lung model with a stepwise progression of PEEP to recruit atelectatic lung segments should be used in pediatric patients with restrictive lung disease (i.e., acute lung injury [ALI]) (Table 1).

In VTV, the device delivers a set volume of gas into the ventilator circuit. Pressure rises passively, inversely related to lung compliance, as gas enters the lungs. A portion of the volume delivered into the circuit is lost to compression of gas in the circuit and humidifier and to stretching of the elastic tubing. There is often a large and unpredictable loss of VT to the ubiquitous and highly variable leak around an uncuffed ET tube, which cannot be easily compensated.^3,4

Lung protective strategies include low VT in the range of 5 to 7 ml/kg and a goal of a plateau pressure of 30 mm Hg or less² in infants in acute respiratory failure, acute respiratory distress syndrome, and ALI. In a volume-regulated mode of mechanical ventilation, the patient’s upper airway and lung compliance influence the peak pressure needed to achieve the set VT.

Those infants being ventilated are at risk of iatrogenic lung injury, including ventilation induced lung injury. Synchronizing the ventilation to the patient’s breathing pattern and minimizing lung injury are crucial in reducing complications such as bronchopulmonary dysplasia and long-term respiratory morbidity. VTV in preterm neonates has been evaluated in the last two decades and is now the standard of care.^3,4

EDUCATION

• Provide developmentally and culturally appropriate education based on the desire for knowledge, readiness to learn, and overall neurologic and psychosocial state.
• Explain the reasons for and the purpose and risks of PPV therapy.
• Discuss sensory information, including the sounds of the ventilator, the sensation of lung inflation, and coughing.
• Provide the family with descriptions and explanations of the equipment alarms.
• Discuss with the family the role of sedation during the period of mechanical ventilation and the use of a sedation holiday for weaning.
• Explain that medications, including local anesthetics, sedatives, and pain medications will be used to minimize pain and anxiety during the procedure.
• Discuss relaxation methods that can be incorporated into the patient’s care, including reading to him or her, providing quiet distractions, and facilitating rest.
• Identify a method of communication between the patient and family and the authorized practitioners.
• Provide assurance that the family can be present and involved in their child’s care.
• Discuss the need for suctioning of the ET tube and the expected coughing sensation.
• Encourage questions and answer them as they arise.

ASSESSMENT AND PREPARATION

Assessment

1. Perform hand hygiene before patient contact.
2. Introduce yourself to the patient and family.
3. Verify the correct patient using two identifiers.
4. If able, assess the patient’s developmental level and ability to interact.
5. Assess the family’s understanding of the reasons for and the risks and benefits of the procedure.
6. Assess the patient’s vital signs.
7. Assess the patient for signs and symptoms of ventilatory failure, including increased arterial partial pressure of carbon dioxide (PaCO₂) and symptoms of hypercarbia, such as respiratory acidosis, decreased mental status, tachycardia, hypertension, and dilated pupils.
8. Assess the patient for signs and symptoms of hypoxemia, including decreased arterial oxygen saturation, pale or cyanotic color, tachycardia or bradycardia, tachypnea, agitation or decreased mental status, and increased work of breathing (WOB).
9. Assess the patient’s cardiovascular stability.

Preparation

1. Ensure that all necessary equipment and supplies have been collected and that the equipment is working properly.
2. Ensure that a manual ventilation bag, a mask, and suction are immediately available and connected at the patient’s bedside.
3. Ensure that the ventilator has been appropriately self-tested per the organization’s practice and the manufacturer’s recommendations.
4. Ensure that the ventilator circuit and humidification device are appropriately assembled on the ventilator and that they are ready for attachment to the patient.
5. Ensure that all necessary connections are made to connect the ventilator to medical air, oxygen, and electricity (emergency red outlets).
6. Ensure that all the ventilator alarms are functioning appropriately.
7. Ensure that the ventilator circuit humidification system is turned on and heating properly with water in the heater chamber and that the temperature alarms are appropriately set per the organization’s practice and the manufacturer’s recommendations.
8. Ensure that the ET tube is secured to the patient with appropriate tape or a commercially available securing device.
9. Position the patient supine with elevation of the head of the bed, with the head in a midline position.^5,6
10. Ensure that the ventilator graphics are recording data.

PROCEDURE

1. Perform hand hygiene and don gloves, gown, mask, and eye protection as indicated.
2. Verify the correct patient using two identifiers.
3. Explain the procedure to the family and ensure that they agree to treatment.
4. Ensure that end-tidal carbon dioxide (ETCO₂) and peripheral oxygen saturation (SpO₂) monitoring are in place.
5. Select the mode of ventilation.

   Rationale: The choice of mode must be individualized to the patient (Table 2).

6. Set the initial VT; observe chest excursion and auscultate lung sounds to ensure that the patient has adequate aeration.

   Rationale: The VT is individualized to the patient and disease state.

7. Set the cycle mechanism (volume, time, or flow). A patient with hypoxemia may benefit from a longer controlled inspiratory time, and the time-cycled mode may be preferred over the flow- or volume-cycled mode.

   Rationale: The cycle mechanism is individualized to the patient and determines when inspiration terminates.

8. Set the ventilator rate.
1. An initial rate setting should be based on the patient’s age and size (Table 2).
2. In the event of apnea or if sedative medication is used, an appropriate minimum rate is set. The rate may be adjusted on the basis of PaCO₂, with the assumption that the VT is held constant.
3. Initially, VT can be estimated. For complete control, a calculated rate is used:



New rate =		PaCO2 (patient) × (set)
		Desired PaCO2



4. For spontaneous breathing, a lower rate is chosen and then adjusted based on the PaCO₂.
5. When permissive hypercapnia is desired for lung protection, pH (rather than PaCO₂) drives changes in the rate.⁷

   Rationale: The rate is set to achieve appropriate minute ventilation, where minute ventilation = VT × respiratory rate. The rate setting depends on how much mandatory ventilation is desired.

9. Set the inspiratory:expiratory (I:E) ratio; typically, it is 1:2.²
1. For a patient with restrictive lung disease, a longer inspiratory time may be beneficial.
2. For a patient with obstructive disease, a longer expiratory time may be necessary.

   Rationale: Inspiratory time influences oxygenation, and expiratory time influences carbon dioxide elimination.

10. Select the PEEP. Set PEEP for an optimal balance between hemodynamics and oxygenation. To improve oxygenation, attempt to titrate PEEP based on the patient’s lung function and disease process.⁴

    Increasing the level of PEEP can cause an increase in intrathoracic pressure, which leads to a decrease in venous return (hemodynamic compromise).

    Do not interrupt the ventilator circuit (e.g., during suctioning) for a patient on higher levels of PEEP; doing so may cause a significant loss of FRC.

11. Adjust the trigger sensitivity to the most sensitive level to reduce the effort the patient must make to access flow from the circuit.
    1. For a patient who has just started mechanical ventilation, the sensitivity is adjusted to provide complete comfort and rest.
    2. The ventilator is triggered when either a pressure sensor or a flow sensor recognizes the patient’s effort.
12. Tailor the flow rate and pattern to meet or exceed the patient’s needs (asleep versus awake). The circuit may provide continuous flow or demand flow.
13. Set the appropriate alarms and limits.

    Rationale: High- and low-pressure alarms, inspiratory time, and VT limits are always set, and the values are based on the cycling mechanism chosen. Low-pressure alarms are used to detect disconnection or leaks in the system. High-pressure alarms are used for notification of increased pressure in the system.

    In the volume-controlled mode, the patient’s lung compliance may cause variable PIP. Set the high-pressure alarm per the organization’s practice, above the patient’s PIP to protect the lungs from sudden changes in resistance or compliance.

14. Set the pressure-support ventilation (PSV), if required.
    1. Consider comfort and a target VT with the initiation of PSV. PSV is used with or without synchronized intermittent mandatory ventilation.
    2. Set a pressure level that provides enough support to achieve a targeted VT. Some patients may need higher initial PSV levels, depending on their disease, to overcome the WOB of the ET tube.
15. Discard supplies, remove personal protective equipment (PPE), and perform hand hygiene.
16. Document the procedure in the patient’s record.

MONITORING AND CARE

1. Monitor cardiopulmonary status including vital signs and indicators of oxygenation and ventilation.
2. Monitor physiologic stability, including cardiac function and hemodynamic changes (heart sounds, heart rate, blood pressure, and perfusion).

   Rationale: Increased intrathoracic positive pressure may reduce venous return and cardiac output. Likewise, positive pressure may cause pneumothorax, which may also decrease cardiac output.

3. Observe the patient for patient-ventilator synchrony.

   Rationale: Asynchrony causes increased WOB and distress. Asynchrony in a small patient is commonly associated with flow regulation; access to flow and speed of delivery influence the patient’s ability to breathe comfortably.

4. Perform a ventilator and patient assessment, including FIO₂, PIP, VT, PEEP, MAP, and other relevant settings, such as the temperature of the inspired gas.

   Rationale: Changes in oxygen flow may occur from the oxygen source; auto-PEEP may also occur. Body temperature can be significantly altered by the temperature of inspired gas.

5. Confirm the appropriate limits of all alarms during each shift.
6. Provide additional ventilatory support, including manual breaths and adjustments in mechanical ventilation as indicated by the signs of hypoxemia, hypercarbia, and hemodynamic instability.

   Rationale: Early intervention when inadequate ventilator support and hemodynamic instability occur may prevent further clinical deterioration.

7. Monitor and adjust the ventilator’s settings according to treatment strategies.

   Rationale: Changes in lung compliance may change the PIP or VT.

8. Monitor the ventilator’s alarms and watch for changes from prescribed settings, including an increased PIP or a change in VT.

   Rationale: An alarm indicating an increase in PIP or change in VT may be associated with a need for suctioning or an airway obstruction. A low-pressure alarm may indicate that there is a leak or break in the ventilator circuit and a disconnect has occurred.

9. Ensure that the ET tube is secure and stabilized. Change the tape or tube holder per the organization’s practice. Assess the skin for signs of pressure injury from the device.
   1. Use a device to ensure security while allowing the patient to move.

      Rationale: A device eliminates undue pressure on the patient’s skin from the ET tube and tubing.

   2. Suction the ET tube as needed and observe the characteristics of secretions.

      Rationale: Suctioning the ET tube maintains airway patency and removes secretions.

10. Minimize sources of infection by limiting interruptions of the circuit and by emptying condensation from the tubing into a trap and not back into the humidification system.

    Rationale: Ventilator-associated events (VAE) can be a factor in morbidity in patients undergoing ventilation.

11. Encourage daily sedation holidays or neurostimulation monitors if the patient is undergoing paralytic therapy.

    Rationale: Sedation and neuromuscular blockade may be necessary to achieve ventilator synchrony, but paralytics mask the patient’s underlying neurologic state. Early identification of the patient’s discomfort allows immediate attention to problems.

12. Observe the patient for signs and symptoms of pain. If pain is suspected, report it to the authorized practitioner.

EXPECTED OUTCOMES

• Adequate oxygenation and ventilation
• Maintenance of adequate pH and PaCO₂
• Decreased WOB
• Ventilation without lung injury
• Hemodynamic stability
• Maintenance of skin integrity
• Airway in correct position
• No infection
• Mobilization and removal of secretions
• Adequate airway humidification
• Adequate pain control during the procedure

UNEXPECTED OUTCOMES

• Inadequate ventilation and oxygenation (hypoxemia, hypercarbia, acidosis, alkalosis)
• Lung overinflation, air-leak syndrome (pneumothorax, pneumomediastinum, pneumoperitoneum, subcutaneous emphysema)
• ALI (volutrauma or progression of lung disease)
• Hemodynamic instability
• Skin breakdown or pressure injury
• Unplanned extubation or malpositioned ET tube
• Ventilator-associated pneumonia (VAP)
• Tenacious sputum
• ET tube obstruction
• Infection
• Inadequately managed pain or anxiety

DOCUMENTATION

• Cardiopulmonary assessment before and after procedure, including vital signs, lung sounds, WOB, arterial blood gas analysis, pulse oximetry, and ETCO₂ monitoring
• ET tube size: cuffed or uncuffed
• ET tube marking at the teeth or gums for correct placement
• Date and time of initiation of ventilator assistance
• Record of ventilator settings, including FIO₂, mode, VT, PIP, rate, and PEEP
• Record of ventilator checks as indicated, including FIO₂, mode, VT, PIP, rate, and PEEP
• Timing of suctioning and characteristics of ET tube secretions
• Significant events that have occurred during the shift
• Temperature of inspired gas
• Pain assessment and specific interventions provided
• Patient’s response to the procedure
• Patient and family education
• Unexpected outcomes and related interventions

REFERENCES

1. Gupta, S., Janakiraman, S. (2018). Volume ventilation in neonates. Paediatrics and child health, 28(1), 1-5. doi:10.1016/j.paed.2017.09.004
2. Kacmarek, R.M. (2021). Chapter 49: Initiating and adjusting invasive ventilatory support. In R.M. Kacmarek, J.K. Stoller, A.J. Heuer (Eds.), Egan’s fundamentals of respiratory care (12th ed., pp. 1072-1104). St. Louis: Elsevier.
3. Klingenberg, C. and others. (2017). Volume-targeted versus pressure-limited ventilation in neonates. Cochrane Database of Systematic Reviews, 10, Art. No.: CD003666. doi:10.1002/14651858.CD003666.pub4 (Level I)
4. Kneyber, M.C.J. and others. (2017). Recommendations for mechanical ventilation of critically ill children from the Paediatric Mechanical Ventilation Consensus Conference (PEMVECC). Intensive Care Medicine, 43(12), 1764–1780. doi:10.1007/s00134-017-4920-z (Level VII)
5. Rivas-Fernandez, M. and others. (2016). Infant position in neonates receiving mechanical ventilation. Cochrane Database of Systematic Reviews, 11, Art. No.: CD003668. doi:10.1002/14651858.CD003668.pub4 (Level I)
6. Rocha, G. and others. (2018). Respiratory care for the ventilated neonate. Canadian Respiratory Journal, 2018, 7472964. doi:10.1155/2018/7472964
7. Walsh, B.K. (2019). Chapter 17: Invasive mechanical ventilation of the neonate and pediatric patient. In B.K. Walsh (Ed.), Neonatal and pediatric respiratory care (5th ed., pp. 301-337). St. Louis: Elsevier.

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