Anemia of Prematurity - Portal Neonatal

Assisted Ventilation of the Newborn
Last Updated: December 23, 2003
Synonyms and related keywords: assisted ventilation of the neonate, respiratory support,
breathing support, neonatal care, chronic lung disease, pulmonary mechanics, gas exchange,
control of breathing, lung injury, conventional mechanical ventilation, CMV
AUTHOR INFORMATION Section 1 of 11
Author: Wally Carlo, MD, Director, Professor, Department of Pediatrics, Division of Neonatology,
University of Alabama at Birmingham
Coauthor(s): Massimo Bellettato, MD, Fellow, Department of Pediatrics, Division of Neonatology,
University of Alabama at Birmingham
Wally Carlo, MD, is a member of the following medical societies: American Academy of Pediatrics,
American Medical Association, American Thoracic Society, Society for Pediatric Research, and
Society of Critical Care Medicine
Editor(s): Steven M Donn, MD, Professor of Pediatrics, Director, Neonatal-Perinatal Medicine,
Department of Pediatrics, University of Michigan Health System; Robert Konop, PharmD, Director,
Clinical Account Management, Ancillary Care Management; Brian S Carter, MD, Associate Director,
Associate Professor, Department of Pediatrics, Division of Neonatology, Vanderbilt University
Medical Center and Gateway Medical Center; Carol L Wagner, MD, Associate Professor,
Department of Pediatrics, Division of Neonatology, Medical University of South Carolina; and Neil N
Finer, MD, Director, Division of Neonatology, Professor, Department of Pediatrics, University of
California at San Diego
INTRODUCTION Section 2 of 11
The primary objective of assisted ventilation is to support breathing until the patient's respiratory
efforts are sufficient. Ventilation may be required during immediate care of the infant who is
depressed or apneic or during prolonged periods of treatment of respiratory failure. Improved survival
from advances in neonatal care has resulted in an increased number of infants at risk for chronic lung
disease. Even though the etiology of lung injury is multifactorial, recent animal and clinical data
indicate that lung injury depends in large part on the ventilatory strategies used. Optimal ventilatory
strategies provide the best possible gas exchange with minimal or no lung injury or other adverse
effects. This article highlights the concepts of pulmonary mechanics, gas exchange, control of
breathing, and lung injury that can be used to optimize conventional mechanical ventilation (CMV).
GAS EXCHANGE Section 3 of 11
Newborns are vulnerable to impaired gas exchange because of their high metabolic rate, propensity
for decreased functional residual capacity (FRC) and decreased compliance, increased resistance,
and potential for right-to-left shunts through the ductus arteriosus and/or foramen ovale. Thus,
impaired gas exchange is common in newborns. Hypercapnia and hypoxemia may coexist, although
some disorders may affect gas exchange differentially.
Hypercapnia
Hypercapnia usually is caused by hypoventilation or severe ventilation/perfusion (V/Q) mismatch.
Carbon dioxide normally diffuses readily from the blood into the alveoli. Elimination of carbon dioxide
from the alveoli is directly proportional to alveolar minute ventilation (see Picture 1), which is
determined by the product of tidal volume (minus dead space ventilation) and frequency. Thus, the
alveolar minute ventilation is calculated as follows:
Alveolar Minute Ventilation = (Tidal Volume - Dead Space) X Frequency