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Am J Perinatol 2003; 20(8): 453-464
DOI: 10.1055/s-2003-45388
ORIGINAL ARTICLE

Copyright © 2003 by Thieme Medical Publishers, Inc., 333 Seventh Avenue, New York, NY 10001, USA. Tel.: +1(212) 584-4662

Low-Birth-Weight Neonates Exhibit a Physiological Set-Point to Regulate CO2: An Untapped Potential to Minimize Volutrauma-Associated Lung Injury

Ravi Mishra1 , Sergio G. Golombek1 , Susan R. Ramirez-Tolentino2 , Santanu Das2 , Edmund F. La Gamma1
  • 1The Regional Neonatal Center, New York Medical College-Westchester Medical Center, Valhalla, New York
  • 2The Division of Newborn Medicine, Department of Pediatrics, State University of New York at Stony Brook, New York
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Publication History

Publication Date:
02 January 2004 (online)

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ABSTRACT

The objective of this article is to determine whether low-birth-weight (LBW) infants have the capacity to modulate minute ventilation to achieve a CO2 set-point within ranges acceptable to clinicians during a procedure designed to identify the best dynamic compliance loops. By using dynamic flow-loop mechanics, we performed a prospective stepwise reduction of tidal volume (by reduction of peak inspiratory pressure, keeping end-expiratory pressure constant), in a group of LBW infants to identify the steepest slope of the dynamic flow-loop. We used flow-synchronized, assist-control mechanical ventilation with termination sensitivity set at 5%. Vital signs and blood gases were assessed every 15 minutes at each stepped-pressure change during the first hour after enrollment and after 12 hours, to evaluate oxygenation and ventilation. Peak inspiratory pressure (PIP) was selected at the lowest level that achieved target range blood gases. The acute reduction of PIP and the resulting lower tidal volume was initially associated with an increase in the spontaneous respiratory rate in the first hour that also was associated with a significant decrease in patient-selected inspiration time. After 12 hours, the spontaneous respiratory rate returned to baseline; the peak PaCO2 was 43.8 ± 2.03 (mean ± SEM). LBW infants have the capacity to alter respiratory rate to change minute ventilation in response to a reduction of tidal volume created by lowering the PIP. Using this model of endogenous CO2 challenge in ventilated infants, we conclude that LBW neonates have the capacity to select a CO2 set-point. This approach suggests an important avenue through which a clinician can minimize volutrauma through a reduction of PIP and use of expiratory trigger to limit excessive PIP and an overall lower mean airway pressure.

KEYWORDS

Very-low-birth-weight - physiological set-point - CO2 sensitivity - permissive hypercapnia - respiratory distress syndrome

REFERENCES