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Mar.25.2021
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Mechanical Ventilation: Pediatric Pressure 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

The basic goals of mechanical ventilation are to improve oxygen delivery to meet metabolic demand and eliminate carbon dioxide, while reducing the work of breathing (WOB). The basic aim of assisted ventilation is to meet the goals while minimizing the associated deleterious effects.undefined#ref1">1

Modes of mechanical ventilation provide positive pressure ventilation (PPV) in an attempt to improve oxygenation and ventilation, prevent cardiovascular failure, manage intracranial pressure, protect the airways, and improve oxygen delivery to the tissues. PPV can be either pressure mode or volume mode.

Most conventional ventilators are equipped with graphics that enable the practitioner to understand how the lungs are 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 waveforms graphics can be used to determine the MAP.2
  • Normal glottis closure at end exhalation is prevented by an endotracheal (ET) tube; therefore, a minimal amount of PEEP maintains physiologic functional residual capacity (FRC).
  • 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 (PaO2) 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.7

Although an appropriate PEEP level may result in clinical benefits, both inappropriately low and high levels may cause harm. An appropriate PEEP level may also 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 PAO2 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)Table 1.

Normal glottic closure at end-exhalation is prevented when an artificial airway is present; therefore, minimal PEEP (approximately 5 cm) maintains physiologic FRC, which is the amount of air left in the lungs at end-expiration.1

Common modes of ventilation:

  • Pressure-regulated ventilation delivers a breath with a preset pressure for a specific length of time.
  • In the assist-control (A/C) mode, the volume or pressure and the inspiration and expiration durations are set, which determines the ventilator rate. This mode allows triggering by the patient; in response, the machine delivers a tidal volume (VT) approximating the mandatory breath. If the patient fails to trigger, the ventilator automatically delivers the preset volume or pressure.
  • Pressure-supported breaths are flow cycled based on the patient's spontaneous inspiratory time and flow demand. Mechanical breaths are time cycled. Theoretically, flow-cycled, pressure-supported breaths should be more comfortable and promote improved patient-ventilator synchrony because the patient has more control over the breath than with mechanical breaths.4

It is important to understand how and when to make ventilator adjustments to improve oxygenation and ventilation (Figure 1). Patients with severe acute respiratory distress syndrome (ARDS) may require even lower VT (4 to 5 ml/kg). In addition, PIP, plateau pressure, or both should be maintained at less than 28 cm H2O and driving pressure at less than or equal to 15 cm H2O.1

EDUCATION

  • Provide developmentally and culturally appropriate education based on the desire for knowledge, readiness to learn, and overall neurologic and psychosocial state.
  • Explain the therapy and equipment to the patient and family, including the reasons for and the purpose and risks of PPV therapy, and provide an explanation of the equipment alarms.
  • Discuss sensory information, including the sounds of the ventilator and alarms, the sensation of lung inflation, and coughing.
  • Explain that medications, including local anesthetics, sedatives, and pain medications will be used to minimize pain and anxiety during the procedure.
  • Discuss the concept of a sedation holiday as a weaning tool while on mechanical ventilation.
  • 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 health care team members.
  • Provide assurance that the family can be present and involved in their child’s care.
  • Discuss the need for suctioning of the artificial airway at regular intervals 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. Determine the family’s desire to be present during the procedure.
  6. Assess the family’s understanding of the reasons for and the risks and benefits of the procedure.
  7. Assess the patient’s vital signs.
  8. 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 acidosis, decreased mental status, tachycardia, hypertension, and dilated pupils.
  9. 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 WOB (retractions).
  10. 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 a slightly elevated position, with the head in a position of comfort as not to place pressure on the ET tube and ventilator circuit interface, unless the patient must be prone to improve ventilatory status.5,6
  10. Ensure that the ventilator graphics are recording data.
  11. Verify the patient’s daily weight in kilograms. Stated, estimated, or historical weight should not be used.3

PROCEDURE

  1. Perform hand hygiene.
  2. Verify the correct patient using two identifiers.
  3. Explain the procedure to the patient and family and ensure that they agree to treatment.
  4. Ensure that a cardiopulmonary monitor is in place to measure end-tidal carbon dioxide (ETCO2) levels and oxygen saturation levels, if indicated.
  5. Select the mode of ventilation.
    1. The PIP-to-PEEP ratio is proportionate to VT; therefore, changes in the PIP-to-PEEP ratio will cause proportional changes in VT.
    2. Pressure-controlled/limited mode, A/C, or synchronized intermittent mandatory ventilation (SIMV) allows for support while still allowing the patient to breathe spontaneously.
    3. Pressure-controlled ventilation regulates pressure during each cycle but does so without a preset VT.
      Rationale: Pressure-controlled ventilation is selected when a ventilation strategy focused on maintaining an exact PIP-to-PEEP ratio is the goal.
  6. Adjust the PIP and PEEP to achieve the targeted VT.
    1. The initial settings are based on the clinical assessment of the patient.
    2. One method is to set the desired PEEP and then adjust the PIP upward until the desired VT is achieved.
    3. Rationale: Parameters are based on previous ventilator settings and the RT’s assessment after reviewing ventilator graphics.
  7. Set the cycle mechanism.
  8. Rationale: The cycle mechanism determines the termination of inspiration with a preset inspiratory time, V T, or flow.
  9. Set the rate, trigger, inspiratory-to-expiratory (I:E) ratio, and PEEP, based on the patient and disease state. Monitor the MAP and minute volume closely as the rate and I:E ratio are adjusted.
  10. For pressure-regulated volume control (PRVC), set a targeted VT and an appropriate I:E ratio.
    1. In most cases, the PRVC is time cycled.
    2. The VT is established by the ventilator measuring resistance and compliance and is controlled with variable flow (VT = inspiratory time × flow).
    3. The patient may struggle initially with the patient-ventilator asynchrony as he or she learns to breathe with the ventilator and ET tube.
    4. If the high-pressure limit alarm sounds, the patient may need suctioning or may have progressive lung disease with decreasing compliance.
      Rationale: The goal is to set the ventilator to deliver the target V T with the least amount of pressure, which may be preset or variable (with a high-pressure limit). The patient’s size and condition guide the I:E ratio.
  11. Set and activate the low-pressure and high-pressure alarms.
    Rationale: Alarm settings are based on the cycling mechanism chosen. Low-pressure alarms are used to detect disconnections in the system. High-pressure alarms are used for notification of increased pressure in the system.
  12. If a spontaneous breathing trial (i.e., spontaneous awakening trial) is attempted, coordinate it with a reduction in the level of sedation.
    In some cases, a spontaneous breathing trial may not be feasible because a reduction in sedation may result in the patient pulling the ET tube and IV lines, and unplanned extubation may occur.4
  13. Discard supplies and perform hand hygiene.
  14. Document the procedure in the patient’s record.

MONITORING AND CARE

  1. Monitor the patient’s cardiopulmonary status, including vital signs and indicators of oxygenation and ventilation.
  2. Monitor the patient’s physiologic stability, including cardiac function and hemodynamic changes (heart sounds, heart rate, blood pressure, and perfusion).
  3. Rationale: Increased intrathoracic positive pressure may reduce venous return and cardiac output. Likewise, positive pressure may cause a pneumothorax, which may also decrease cardiac output.
  4. Observe for patient-ventilator synchrony.
    Rationale: Asynchrony causes increased WOB and distress. Asynchrony in a small child is commonly associated with flow regulation; access to flow and speed of delivery influence the patient’s ability to breathe comfortably.
  5. Perform a ventilator check, including FIO2, PIP, VT, PEEP, MAP, and other relevant settings, such as the temperature of the inspired gas.
    Rationale: Body temperature can be significantly altered by the temperature of inspired gas.
    Make sure that the parameters being set meet the patient’s physiologic demands by allowing sufficient flow, FIO2, and PEEP without compromising hemodynamics and reducing the WOB.
  6. Confirm the activation of all alarms during each shift.
  7. Provide additional ventilatory support, including manual breaths and adjustments in mechanical ventilation as indicated by signs of hypoxemia, hypercarbia, and hemodynamic instability. Provide manual ventilation with a manual resuscitation bag, if needed because of deterioration.
    Rationale: Early intervention when inadequate ventilator support and hemodynamic instability occur may prevent further clinical deterioration.
  8. Monitor and adjust the ventilator’s settings according to treatment strategies.
    Rationale: Changes in lung compliance may change the PIP or V T.
  9. Monitor the ventilator alarms and watch for changes from prescribed settings, including an increased PIP or a change in VT.
    Rationale: An alarm indicating an increased PIP or change in VT may be associated with a need for suctioning or an airway obstruction. A low-pressure alarm may indicate that the ventilator tubing has been disconnected.
  10. Ensure that the patient’s artificial airway is secure and stabilized.
    1. Resecure the tape whenever it loosens. Use fresh tape and fresh skin barrier materials with each change of tape. This is a two-person procedure.
    2. Confirm the depth of the ET tube before adjusting the tube.
    3. Use a commercial artificial airway tube holder whenever possible.
    4. Confirm bilateral breath sounds when the task is complete and document results.
  11. Suction the patient’s artificial airway as indicated and observe the characteristics of secretions.
    Rationale: Suctioning the artificial airway maintains airway patency and removes secretions.
  12. Encourage a daily sedation holiday and check paralytic status 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. Daily sedation interruption improves outcomes and significantly reduces the duration of mechanical ventilation and intensive care. 4
  13. 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, pneumopericardium, subcutaneous emphysema)
  • ARDS
  • Ventilator-induced lung injury (volutrauma, atelectrauma, biotrauma)
  • Hemodynamic instability
  • Facial pressure injury
  • Malpositioned artificial airway
  • Unplanned extubation or decannulation
  • Ventilator-associated pneumonia
  • Tenacious sputum
  • Artificial airway obstruction
  • Inadequately managed pain or anxiety
  • Patient-ventilator dyssynchrony

DOCUMENTATION

  • Cardiopulmonary assessment, including vital signs, lung sounds, WOB, and arterial blood gas, pulse oximetry, and ETCO2 monitoring values
  • Date and time of initiation of ventilator assistance
  • Record of ventilator settings, including FIO2, mode, VT, PIP, rate, and PEEP
  • Timing of suctioning and characteristics of respiratory secretions
  • Pain assessment and specific interventions provided
  • Patient’s response to the procedure
  • Education
  • Unexpected outcomes and related interventions

REFERENCES

  1. Chipman, D.W. (2021). Chapter 54: Neonatal and pediatric respiratory care. In R.M. Kacmarek, J.K. Stoller, A.J. Heuer (Eds.), Egan’s fundamentals of respiratory care (12th ed., pp. 1212-1242). St. Louis: Elsevier.
  2. Gupta, S., Janakiraman, S. (2018). Volume ventilation in neonates. Paediatrics and Child Health, 28(1), 1-9. doi:10.1016/j.paed.2017.09.004
  3. Institute for Safe Medication Practices (ISMP). (2020). 2020-2021 Targeted medication safety best practices for hospitals. Retrieved January 12, 2021, from https://www.ismp.org/sites/default/files/attachments/2020-02/2020-2021%20TMSBP-%20FINAL_1.pdf (Level VII)
  4. 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.
  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, 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.

ADDITIONAL READINGS

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

van der Staay, M. Chatburn, R.L. (2018). Advanced modes of mechanical ventilation and optimal targeting schemes. Intensive Care Medicine Experimental, 6(1), 30. doi:10.1186/s40635-018-0195-0

Elsevier Skills Levels of Evidence

  • Level I - Systematic review of all relevant randomized controlled trials
  • Level II - At least one well-designed randomized controlled trial
  • Level III - Well-designed controlled trials without randomization
  • Level IV - Well-designed case-controlled or cohort studies
  • Level V - Descriptive or qualitative studies
  • Level VI - Single descriptive or qualitative study
  • Level VII - Authority opinion or expert committee reports
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