Mechanical ventilation may contribute to an acute or a chronic respiratory tract injury, such as atelectrauma, volutrauma, barotrauma, oxygen toxicity, and a pulmonary or systemic inflammatory response to lung trauma.undefined#ref2">2
Mechanical ventilation is respiratory support using mechanical assistance.3 The goals of mechanical ventilation are to facilitate adequate gas exchange and decrease the neonate’s work of breathing, while minimizing the risk of lung injury and optimizing comfort.4
Neonatal respiratory support is an ever-evolving field. The increased use of improved noninvasive respiratory modalities, which are generally accepted as the preferred modes of support, can reduce the need for invasive mechanical ventilation. Indications for mechanical ventilation are respiratory failure, pulmonary insufficiency, severe apnea and bradycardia, congenital cardiac disease, central nervous system disease, and surgery.
Neonates present unique challenges that complicate the use of mechanical ventilation, including noncompliant lungs; rapid, irregular respiratory rates; short inspiratory times; and limited muscle strength. In addition, the approach to respiratory support and treatment differs based on gestational age.4
In positive pressure ventilation, a breath is delivered until a specific pressure or volume is reached. There are four main categories of how pressure or volume of air is delivered:
Positive pressure ventilation measuring volume delivers more stable tidal volume (VT) (Table 1) and allows the ventilator to adjust to the patient’s lung compliance over time.5 Volume ventilation has the advantage of automatically reducing inflation pressure when lung compliance improves because the underlying pulmonary condition resolves. Volume ventilation as compared to pressure ventilation is associated with a significant reduction in the incidence of pneumothorax, hypocarbia, intraventricular hemorrhage, periventricular leukomalacia, and the duration of mechanical ventilation.3
There are two modes for how ventilation rates are determined: intermittent mandatory ventilation and patient-triggered ventilation. For patient-triggered ventilation, there are five options available.3
These various modes of mechanical ventilation are best classified based on how each breath is initiated, how the gas flow controls each breath, and how the breath ends (Table 2).
In addition to these modes of mechanical ventilation, there are high-frequency ventilation (HFV) modes, which use small VT at rapid rates. The most common forms of HFV used in the neonate are high-frequency oscillatory ventilation (HFOV) and high-frequency jet ventilation (HFJV).2,3 The advantage of HFV modes over other modes of mechanical ventilation is the ability to deliver adequate volumes with decreased airway pressure.
Indications for the use of HFV include severe lung disease that is unresponsive to other forms of mechanical ventilation, pulmonary air leaks, and pulmonary hypoplasia. Both HFOV and HFJV deliver gentle ventilation and are very effective with disorders in which carbon dioxide elimination is the major problem. Severe atelectatic disorders (e.g., respiratory distress syndrome) and obstructive disorders (e.g., meconium aspiration syndrome) have been shown to respond to HFJV.2,3 Determining the appropriate ventilator mode is based on the individual patient’s condition, disease process, and response to previous ventilatory support (Table 3).
Ensuring the proper placement of the endotracheal (ET) tube is essential during mechanical ventilation. Monitoring exhaled carbon dioxide levels helps determine if the ET tube is in the correct place. End-tidal and side-stream carbon dioxide monitors are available to assess the levels of exhaled carbon dioxide effectively. Failure to detect exhaled carbon dioxide in patients with adequate cardiac output strongly suggests esophageal intubation.
Because neonates have a limited volume of exhaled gas, in some cases several breaths must be passed through the sensor to detect carbon dioxide. Sometimes poor or absent pulmonary blood flow (e.g., during cardiac arrest) may result in failure to detect exhaled carbon dioxide despite correct tube placement in the trachea. Failure to detect carbon dioxide can lead to the conclusion that the tube is incorrectly placed and thus results in unnecessary extubation and reintubation in these critically ill neonates.1
The use of an uncuffed ET tube is preferred in neonates to prevent airway necrosis; however, this type of ET tube is less secure, and unplanned extubations can occur with minimal tube movement. Signs of extubation include sudden deterioration in clinical status, abdominal distention, crying, decreased chest wall movement, breath sounds in the abdomen, agitation, cyanosis, and bradycardia.
Rationale: Emergency equipment is necessary for sudden changes in the patient’s condition or in the event of ventilator failure.
Rationale: Early identification of the patient’s comfort level allows immediate attention to problems. Sedation may be necessary to achieve ventilator synchrony but should be used with caution.
Rationale: Chest wall vibration is an indicator of lung compliance, airway patency, and effectiveness of ventilator settings. An increase in chest wall vibration accompanied by an increase in partial pressure of arterial oxygen (Pa
2) and a decrease in arterial partial pressure of carbon dioxide (Pa
2) is an indication to consider weaning the ventilator settings. A sudden decrease in chest wall vibration may indicate a plugged or displaced ET tube or a pneumothorax. Unless ventilation is stopped, assessing the patient’s breath sounds during HFV is impossible.
Rationale: Elevating the head of the bed reduces the incidence of aspiration and is a recommended practice in the prevention of ventilator-associated pneumonia.
Suctioning is not a benign procedure. Suction only as needed to maintain airway patency and remove secretions. Carefully assess the patient’s conditions that require ET tube suctioning.
Rationale: An alarm may be associated with the need for suctioning or the need to drain water from the tubing, or it may indicate that the ventilator tubing has been disconnected.
Report to the practitioner any inappropriate sounding of alarms.
Rationale: Changes in lung compliance may occur, resulting in the need for more or less ventilator support.
Rationale: Closed, inline suctioning devices allow suctioning while ventilation continues, which minimizes the fluctuations in oxygenation, changes in cerebral blood flow, and other hemodynamic changes. Closed, inline suctioning also decreases the risk of infection by decreasing the potential for contamination of the ET tube and suction catheter.
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