Clinical Assessment of Airway Function in Health and Disease

Thomas H. Shaffer; Aaron B. Cullen; Marla R. Wolfson

doi:10.1542/neo.3-7-e131

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Objectives

After completing this article, readers should be able to:

Describe which pulmonary function tests can be used to measure tidal lung mechanics and forces of expiratory flow.
Describe the airway conditions that can be assessed radiographically.
Delineate clinical methods of diagnosing central airway collapse and quantifying airway wall stiffness.

Introduction

Clinical assessment of pulmonary function is a valuable tool in the identification and treatment of neonatal disease. As shown in the Table⇓, a multitude of tests is available to identify and measure airway function clinically in pediatric populations. These tests often identify functional abnormalities in the airways of preterm infants exposed to mechanical ventilation, including elevated resistance, decreased forced expiratory flow, airway hyperreactivity, and excessive central airway collapsibility. In addition to aiding in diagnosis, these procedures help predict the effects of early injury on future airway growth and function and can be used to evaluate the effectiveness of newer therapies. Serial evaluation of airway function is especially useful for infants who fail to improve as expected; who have frequent severe exacerbations of pulmonary dysfunction; or who demonstrate stridor, chronic wheezing, or focal areas of chronic atelectasis or hyperinflation.

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Table

Clinical Evaluation of Airway Function

Pulmonary Function Profile

With the simultaneous measurement of respiratory pressures, volumes, and air flow, pulmonary mechanics can be monitored relatively noninvasively. Pulmonary function profiles can be determined to assess initial disease etiology, the response to therapy, and disease sequelae during follow-up. For example, the pressure-volume relationship of a preterm infant can identify the degree of respiratory function and monitor the response following surfactant administration (Fig. 1). The evaluation of tidal breath pressure-volume relationships serves as a tool to optimize the parameters of mechanical ventilation (Fig. 2). Over time, sequential pulmonary mechanics can be used to monitor the progression and improvement in both lung and airway abnormalities (Fig. 3).