Ventilatory control and supplemental oxygen in premature infants with apparent chronic lung disease

Abstract

Objectives: Our goal was to evaluate changes in respiratory pattern among premature infants born at <29 weeks gestation who underwent a physiological challenge at 36 weeks postmenstrual age with systematic reductions in supplemental oxygen and inspired airflow.

Study design: Subjects were all infants enrolled in the Prematurity and Respiratory Outcomes Project at St. Louis Children's Hospital and eligible for a physiological challenge protocol because they were receiving supplemental oxygen or augmented airflow alone as part of their routine care. Continuous recording of rib cage and abdominal excursion and haemoglobin oxygen saturation (SpO2%) were made in the newborn intensive care unit.

Results: 37 of 49 infants (75.5%) failed the challenge, with severe or sustained falls in SpO2%. Also, 16 of 37 infants (43.2%) who failed had marked increases in the amount of periodic breathing at the time of challenge failure.

Conclusions: An unstable respiratory pattern is unmasked with a decrease in inspired oxygen or airflow support in many premature infants. Although infants with significant chronic lung disease may also be predisposed to more periodic breathing, these data suggest that the classification of chronic lung disease of prematurity based solely on clinical requirements for supplemental oxygen or airflow do not account for multiple mechanisms that are likely contributing to the need for respiratory support.

Keywords: Neonatology; Respiratory.

Conflict of interest statement

Conflicts of interest: The authors have no other financial relationships or other conflicts of interest that compromise, or may be perceived to compromise, the integrity of the observations herein.

Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Figures

Figure 1

Subject enrollment and outcomes.

Figure 2

Diagram showing a 5-minute recording from a patient who failed the challenge. The upper 2 tracings show respiratory excursions. The lowest tracing is SpO2% averaged every 3 to 5 sec. Note the stable SpO2% > 90% when respirations are regular. Note the intermittent hypoxemia and characteristic oscillations in SpO2% seen with the brief run of periodic breathing early in the tracings, and the continuous oscillations when PB is established. This pattern occurred in 43.2% of challenge failures. For this subject, continuous periodic pattern was associated with failure-range falls in SpO2% to < 80%. First vertical mark: challenge begun, followed by brief run of periodic breathing. 2nd vertical mark: quiet sleep. 6th vertical mark: RAC failure was declared. The smaller box is an enlarged 30 sec excerpt from between vertical marks 5 and 6.

Figure 3

Prevalence of changes in minute ventilation and respiratory pattern among infants receiving the physiologic challenge. The majority of infants (73.6%), whether they passed or failed, either developed PB or did not increase their minute ventilation, or both, in response to the challenge. Potentially beneficial response defined as increase in minute ventilation and no periodic breathing. Potentially detrimental, or dysfunctional, response is no change or reduction in minute ventilation, much periodic breathing, or combination of failure to increase minute ventilation while having periodic breathing.