The Science Journal of the American Association for Respiratory Care

2003 OPEN FORUM Abstracts

COMPARISON OF AN ADAPTIVE CONTROL OXYGEN BLENDER WITH MANUAL TITRATION OF OXYGEN THERAPY IN AN OLEIC ACID INJURED PIGLET MODEL

Tom Blackson, RRT1, 3, Tami Irwin-Sherman, RN4, Tim Cox, RRT2, John Rendle, RRT2, Suzanne M. Touch, MD4, 5, Thomas H. Shaffer, Ph.D.2, 4. 1Christiana Care Health System, 2duPont Hospital for Children, 3Delaware Technical and Community College, Wilmington Campus, 4Nemours Lung Center, DE, 5Neonatology, Thomas Jefferson Univ, Phila, PA.

Background:
The toxic effects of oxygen therapy (O2) are considered a predisposing factor for chronic lung disease (CLD) in the neonate. To minimize the toxic effects of O2, the lowest adequate concentration of oxygen should be employed. Conventionally, air-oxygen blenders are used to precisely mix gas for O2. The desired O2 concentration is often guided by arterial pulse oximetry (SpO2). Bedside caregivers are employed to effect timely adjustment of O2 based upon SpO2 values. This practice is both time and labor intensive which limits the frequency of O2 adjustment. Hyperoxic and hypoxic conditions may exist in neonates despite aggressive protocols for O2 titration. 

Purpose: To compare a closed-loop, adaptive control smart blender (SB) to an "aggressive" manual titration (MT) approach to FIO2 adjustment used in our NICU, with the goal of maintaining an SpO2 of 95% ± 2%, while attempting to adjust the FIO2 to the lowest acceptable level. 


Methods:
Spontaneously breathing neonatal pigs (n=12; wt=2.62 ±0.62kg) were anesthetized, instrumented, given continuous positive airway pressure, oleic acid (0.08 cc/kg) and randomized to either MT of FIO2 (± 5% every 15 min.) or the adaptive control SB programmed to automatically adjust FIO2 to maintain an SpO2 of 95% ± 2%. Vital signs, arterial blood gases, pulmonary mechanics, functional residual capacity, and thoracoabdominal motion were monitored throughout the study. During the MT approach, FIO2 and SpO2 were documented every 15 min. followed by FIO2 adjustment to achieve the target SpO2. FIO2 and SpO2 were averaged every 15 min. from a data logger integrated into the SB prototype for data collection from that arm of the study.

RESULTS:
Vital signs, gas exchange, lung mechanics, and pulmonary function were not different between groups. The SB group spent a greater percentage (%) of time within the targeted SpO2 range when compared to the MT group, (77% and 33% respectively). The SpO2 in the SB group reached a low of 91%, accounting for 2% of total sample time out of range, but never went below this value. The SpO2 in the MT group reached a low of 82% with SpO2 values below 91% accounting for 14% of total sample time out of range. 

O2 Adjustment Technique % Time In Target Range SpO2 93 - 97% % Time Hyperoxic SpO2> 97% % Time Hypoxic SpO2< 93%
Manual 33% 49% 18%
Smart Blender 77%  8% 15%



Conclusions:
These first pre-clinical results demonstrate that SB technology provides a more timely, yet safe reduction in O2 when compared to an MT O2 approach. SB technology achieved the desired SpO2 target range a greater % of time than the MT technique resulting in less time spent in hyper- or hypoxic conditions. When compared with the MT approach, SB technology may significantly reduce elements of CLD that result from oxidative stress associated with hyperoxia while reducing the frequency, duration, and intensity of hypoxic events. Clinical evaluation of SB technology may be warranted. 

Disclosure: Supported in part by the Nemours Foundation and Hill-ROM Corp.

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