PRETERM INFANTS

Preterm Infants

Preterm Infants

Abstract

Few preterm infants succumb nowadays to respiratory failure. However, the combination of prematurity and prolonged mechanical ventilation often results in Chronic Lung Disease (CLD) that may continue throughout infancy and early childhood. This review will focus on current controversies in the respiratory care of extremely preterm infants

Introduction

Laryngomalacia is the leading cause of stridor in infancy. It is the most common laryngeal anomaly of the newborn followed by subglottic stenosis and bilateral vocal fold paralysis. It is characterized by flaccidity of the supraglottic structures, which prolapse inward during inspiration leading to upper airway obstruction.

Discussion

Etiology

Review of literature suggests that there are three basic theories that attempt to explain the development of laryngomalacia. These are

Cartilage Immaturity Theory

Theory of Anatomic Abnormality and

Neuromuscular Immaturity Theory (Thompson, 2007, 1-33).

Cartilage Immaturity Theory

Cartilage Immaturity Theory was first proposed by Sutherland and Lack in the late 19th century. According to this theory laryngeal flaccidity develops due to delayed maturation of the cartilageneous support of the larynx. This theory has since been disproved because there is no evidence of chondropathy in these patients. According to the Theory of Anatomic Abnormality, laryngomalacia is an exaggeration of the normal anatomic features of an infant larynx. The infant larynx is softer, more pliable, and easily prone to mucosal edema. There can often be an omega- shaped epiglottis. Exaggeration in one or more of these anatomic features may lead to laryngomalacia. The most accepted theory is that of neuromuscular immaturity which suggests that laryngeal hypotonia occurs due to delayed neuromuscular control of the larynx. The prevlance of other neurological disorders in infants with laryngomalacia supports this hypothesis.

Classification of Laryngomalacia

There are various types of laryngomalacia and various classification schemes have been attempted to correlate type with severity and treatment. For the sake of our presentation, we have classified laryngomalacia into mild, moderate or severe depending upon history, physical exam and flexible laryngoscopy findings. One can describe the location of the laryngomalacia as anterior (the epiglottis prolapses posteriorly into the airway), lateral (AE folds and the cuneiform or corniculate cartilages prolapse medially into the airway) and posterior (the redundant mucosa over the arytenoids prolapses anteriorly into the airway). Laryngomalacia may present as a combination of these subtypes (Richter, Thompson, 2008, 837-64).

Association with Reflux

It has been found that there is a strong association of GERD with laryngomalacia and studies have found that 80-100% of infants with laryngomalacia will also have reflux. It is unclear however, whether GERD is a cause or an effect of the respiratory obstruction. It has been proposed that the fixed respiratory obstruction in laryngomalacia leads to a large negative intrathoracic pressure, which in turn leads to reflux and worsening laryngeal edema and obstruction. In addition, the vagal tone to the lower esophageal sphincter may be reduced contributing to the reflux. These observations underscore the importance of empiric reflux therapy in patients with laryngomalacia.

Risk Factors

Risk factors for severe laryngomalacia include:

Prematurity- Although premature infants do not necessarily have a higher incidence of laryngomalacia, they ...