Control of Laryngeal Muscle Activity in Preterm Infants

Abstract

Laryngeal muscle activity may be an important determinant of breathing patterns in infants. it has been proposed that retardation of expiratory flow (expiratory braking) and grunting, characteristic of neonates with respiratory distress, are accomplished by active laryngeal adduction (8). Healthy preterm and term infants are also able to control expiratory flow in order to actively maintain end expiratory lung volume above the resting lung volume (9, lo), although the relative contributions of laryngeal and diaphragmatic mechanisms to this regulation of lung volume are unclear. The purpose of this investigation was to determine the response of the laryngeal muscles and the diaphragm in healthy preterm infants to changes in respiratory drive and their resultant effects on airflow patterns. METHODSStudies were performed on 12 preterm infants free of cardiorespiratory problems at the time of study. Mean gestational age at birth was 32 5 2 wk (mean + SD) as determined from both maternal history and physical and neurological examination.The subjects were studied at a postnatal age of 21 + 8 days when their weight was 1.7 .t 0.2 kg. All infants were breathing room air at the time of study, although six had recovered from respiratory distress syndrome.

Positive End Expiratory Pressure during Resuscitation of Premature Lambs Rapidly Improves Blood Gases without Adversely Affecting Arterial Pressure

“…This intrinsic PEEP, or expiratory braking, promotes lung distension (24,25). Intubating infants for resuscitation effectively bypasses the larynx and abolishes this intrinsic PEEP.…”

Patient–Ventilator Interaction

“…The complexity of the mechanisms that determine upper airway patency and modulate its resistance makes it difficult to predict the degree of transmission of the positive pressure applied on the nose to the infant's distal airways. [66][67][68][69][70][71] Sufficient transmission of the positive pressure during apnea is particularly important, because nasal ventilation is often used in infants with immature respiratory control. The efficacy of nasal ventilation during apnea is not consistent, and it is inadequate if the infant's upper airway is not patent.…”

Hypoxemia and low Crs in vagally denervated lambs result from reduced lung volume and not pulmonary edema

“…However, postinflation Crs per kilogram body weight showed no significant differences between the shamoperated and vagally denervated animals (B). absence of afferent vagal feedback, which plays a critical role in the maintenance of lung volume and breathing patterns in both term and preterm neonates (7,8,13,16,30,32). To meet the high-metabolic demands and overcome the adverse effects of a very compliant chest wall, the neonates use various strategies to defend lung volume, including rapid breathing rates, long expiratory time constants relative to the expiratory time, high-dynamic FRC, and higher frequency of augmented breaths (11,40).…”

“…To meet the high-metabolic demands and overcome the adverse effects of a very compliant chest wall, the neonates use various strategies to defend lung volume, including rapid breathing rates, long expiratory time constants relative to the expiratory time, high-dynamic FRC, and higher frequency of augmented breaths (11,40). Evidence suggests that diaphragmatic postinspiratory activity, along with intercostal muscle and laryngeal adductors activation (expiratory braking) during expiration, helps maintain the end-expiratory lung volume in both neonates and adults (8,12,13,18,20,43). Furthermore, in the neonate, expiratory braking assists in keeping the endexpiratory lung volume above the passive FRC (7).…”