Apnea of Prematurity Clinical Presentation

Updated: Nov 06, 2016
  • Author: Dharmendra J Nimavat, MD, FAAP; Chief Editor: Ted Rosenkrantz, MD  more...
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Presentation

History

Initial identification and assessment of apnea

The bedside caregivers—namely, the nurse in the neonatal intensive care unit (NICU) the respiratory care practitioner—identify the problem for the physician. Apnea should be distinguished from periodic breathing and documented. Use of a cardiorespiratory monitor is essential for identifying apnea of prematurity (AOP) and for monitoring the patient's blood pressure. Events associated with apnea, such as bradycardia and cyanosis, must be quantified. For bradycardia, the magnitude of reduction in heart rate from baseline and the duration of the event should be recorded. The presence and duration of central cyanosis should also be noted.

Pulse oximetry may be helpful for measuring the severity and duration of central O2 desaturation. Caregivers should be aware of the problems associated with the use of pulse oximetry to evaluate O2 saturation. [61]

When apnea is observed, its duration must be established. Cardiorespiratory monitors can be used to quantify the duration. Caregivers should attempt to define the type and severity of the patient's apnea. The type of apnea is identified as central, obstructive, or mixed. A nasal thermistor may be needed in conjunction with pneumography to differentiate the type of apnea.

Classification of the severity of apnea

Criteria to classify the severity of apnea have not been well developed in clinical studies.

The University of Washington published indications for different treatments based on the severity of apnea of prematurity. [62] This classification for apnea of prematurity uses the terms spontaneous, mild, moderate, or severe. Note the following:

  • A spontaneous event might be defined by apnea with minimal physiologic changes, an event of brief duration, one associated with self-recovery, or an event only occurring once or twice in 24 hours.

  • Mild or moderate events involve apnea, bradycardia, and/or O2 desaturation of intermediate magnitude. These events require therapeutic interventions less rigorous than those needed for severe episodes.

  • A severe event entails prolonged apnea associated with clinically significant and persistent bradycardia, as well as O2 desaturation (ie, central cyanosis). A severe event requires vigorous stimulation, administration of an increased concentration of inspired O2, and/or assisted ventilation (eg, bag-mask ventilation).

Clinical centers must develop the classification system they wish to use to measure the severity of apnea. Factors often used to judge the need for future interventions include these:

  • Severity of the apnea

  • Number of events per day

  • Magnitude of the intervention required to alleviate the event

The therapeutic approach used in most NICUs involves a progression from tactile stimulation to methylxanthine therapy and then some form of assisted breathing (eg, nasal continuous airway pressure or assisted ventilation).

Exclusion of other causes of apnea

Before a diagnosis of apnea of prematurity is made, other causes of apnea in neonates must be excluded (see Differentials).

All forms of apnea may be difficult to detect visually, although obstructive apnea is usually most obvious to a trained observer.

Cardiorespiratory monitoring and pulse oximetry have improved bedside detection of apnea of prematurity. [63] Caregivers should familiarize themselves with the advantages and disadvantages of cardiorespiratory monitoring and pulse oximetry in neonates. Apnea, bradycardia, and desaturation events are very subjective in nature unless the standard definition is strictly followed. Current cardiorespiratory monitors are very sophisticated; however, their use and interpretation are also very subjective. Clinicians heavily rely on nursing documentation to make decisions. By introducing standard definitions, individual subjectivity may be reduced which, in turn, may lead to fewer interventions and potentially decrease the length of stay. [64]

Developing a NICU-specific standardized approach to the apnea of prematurity leads to reduce variations among clinicians. Brief isolated events need not be treated same as apnea of prematurity e.g. spontaneously resolving events and feeding related events which improves with interruption of feeding. [65]

Published findings show that even highly trained observers miss more than 50% of apnea of prematurity episodes.

Precise diagnosis of apnea of prematurity requires multichannel recordings, which are most commonly measurements of nasal airflow, thoracic impedance, heart rate, and O2 saturation. Expanded testing may include electroencephalography and/or use of an esophageal pH probe with a high thoracic Clark electrode. Hydrochloric acid may be added to the feedings to increase the gastric concentration of hydrogen ions.

Next:

Physical Examination

Physical examination should include observation of the infant's breathing patterns while he or she is asleep and awake. The prone or supine sleeping positions and other lying postures may be important during this clinical observation.

Important to the assessment of neonatal apnea is the identification of airway abnormalities (eg, choanal obstruction, anomalies of the palate, jaw deformities, neck masses) and conditions in distant organs that influence breathing (eg, brain hemorrhages, seizures, pulmonary disorders, congenital heart disease).

Findings in the head and neck and other obvious major and minor anomalies identified may suggest chromosomal abnormalities or a malformation syndrome. Appropriate work-up must then follow.

Physical examination elements

Monitor the baby's cardiac, neurologic, and respiratory status.

Observe the infant for any signs of breathing difficulty, desaturation, or bradycardia during feeding.

Reflex effects of apnea include characteristic changes in heart rate, blood pressure, and pulse pressure. Note the following:

  • Bradycardia may begin within 1.5-2 seconds of the onset of apnea.

  • Apneic episodes associated with bradycardia are characterized by decreases in heart rate of more than 30% below baseline rates.

  • This reflex bradycardia is secondary to hypoxic stimulation of the carotid body chemoreceptor or a direct effect of hypoxia on the heart.

  • Transient bradycardias also occur relatively often in very low birth weight infants who also have apnea of prematurity. [66] These events are not associated with apnea, but they are presumed to be mediated by an increase in vagal tone.

Pulse oximetry may reveal clinically significant desaturation. However, pulse oximeters typically have a delay in recording the event.

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