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.
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:
Additional facts about PPV include:
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
Rationale: The choice of mode must be individualized to the patient (Table 2).
Rationale: The VT is individualized to the patient and disease state.
Rationale: The cycle mechanism is individualized to the patient and determines when inspiration terminates.
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.
Rationale: Inspiratory time influences oxygenation, and expiratory time influences carbon dioxide elimination.
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.
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.
Rationale: Increased intrathoracic positive pressure may reduce venous return and cardiac output. Likewise, positive pressure may cause pneumothorax, which may also decrease cardiac output.
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.
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.
Rationale: Early intervention when inadequate ventilator support and hemodynamic instability occur may prevent further clinical deterioration.
Rationale: Changes in lung compliance may change the PIP or 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.
Rationale: A device eliminates undue pressure on the patient’s skin from the ET tube and tubing.
Rationale: Suctioning the ET tube maintains airway patency and removes secretions.
Rationale: Ventilator-associated events (VAE) can be a factor in morbidity in patients undergoing ventilation.
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.
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