A 3-week-old boy is evaluated in the neonatal intensive care unit due to apnea. The patient was born at 27 weeks gestation and had a birth weight of 1 kg (2 lb 2 oz). For the past 2 weeks, he has been stable on minimal respiratory support via nasal cannula but has had intermittent episodes of no respiratory effort for up to 30 seconds at a time. These episodes are associated with bradycardia and desaturation. The patient recovers spontaneously or with brief stimulation from the nurse. He is well appearing between episodes. Examination of the lungs reveals bilateral, clear breath sounds with easy work of breathing. Ultrasound of the head is normal. Arterial blood gas values are normal. This patient's clinical findings are most likely caused by an abnormality in which of the following areas?

Question

A 3-week-old boy is evaluated in the neonatal intensive care unit due to apnea.  The patient was born at 27 weeks gestation and had a birth weight of 1 kg (2 lb 2 oz).  For the past 2 weeks, he has been stable on minimal respiratory support via nasal cannula but has had intermittent episodes of no respiratory effort for up to 30 seconds at a time.  These episodes are associated with bradycardia and desaturation.  The patient recovers spontaneously or with brief stimulation from the nurse.  He is well appearing between episodes.  Examination of the lungs reveals bilateral, clear breath sounds with easy work of breathing.  Ultrasound of the head is normal.  Arterial blood gas values are normal.  This patient's clinical findings are most likely caused by an abnormality in which of the following areas?

Quizplus · Accepted Answer

11ec160b_3cd2_c4e4_9249_27de6e246fe2_MD0001_00 Apnea is defined as episodes of respiratory cessation lasting >20 seconds, often associated with decreased heart rate and oxygen saturation. Apnea may be obstructive, in which respiratory effort occurs but is blocked, or central, which is characterized by the absence of any respiratory effort. This patient has apnea of prematurity, a type of central apnea that occurs in virtually all extremely preterm newborns at gestational age <28 weeks due to immature central respiratory centers. The normal respiratory drive originates from respiratory centers in the medulla and pons. The medullary respiratory centers are stimulatory neurons that trigger inspiration (from the dorsal respiratory group) and expiration (from the ventral respiratory group). These neurons send impulses to the diaphragm via the phrenic nerve and to the intercostal muscles. The medullary respiratory centers also receive constant input from the pontine respiratory center to modify respiratory rate and depth of inspiration as well as from chemoreceptors, stretch receptors, and proprioceptors to further modify respiration. The respiratory centers can be consciously overridden by the cortex (eg, intentional deep sigh, breath-holding). In apnea of prematurity, the central stimulatory neurons are not fully developed, leading to intermittent interruptions in the normal respiratory drive. Apneic episodes typically develop within the first few days of life and may persist for several months while the central respiratory centers mature. Treatment is with methylxanthines (eg, caffeine), which stimulate respiratory neural output. (Choices B and C) Failure of the lower motor neurons that innervate the intercostal muscles or mixed motor sensory nerves, such as the phrenic nerve that innervates the diaphragm, can cause apnea in conditions such as spinal muscular atrophy type 1 or phrenic nerve injury, respectively. This newborn has normal breathing between episodes, making nerve impairment unlikely. (Choice D) Peripheral chemoreceptors (eg, carotid bodies, aortic body) sense changes in carbon dioxide, oxygen, and pH levels and trigger the central respiratory center to modify respiration. This patient's normal blood gas values indicate that the respiratory changes are not being driven by chemoreceptors. (Choice E) Stretch receptors in the lung trigger cessation of inspiration when the lung is approaching total lung capacity. This newborn has normal respiration between episodes and is not hyperexpanding the lungs, so the stretch receptors are not involved in his apnea. Educational objective: The pontine and medullary respiratory centers coordinate normal respiratory drive. Immaturity of these central respiratory centers causes apnea of prematurity, which is common in extremely preterm newborns.

A 3-Week-Old Boy Is Evaluated in the Neonatal Intensive Care