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A nonlinear regression analysis of nonlinear, passive-deflation flow-volume plots
W S Jarriel1, P Richardson, R D Knapp
1Department of Pediatrics, Baylor College of Medicine, Houston, Texas 77030.
Pediatric Pulmonology
|March 1, 1993
Summary
Conventional linear analysis fails to detect airway resistance changes in premature infants. Nonlinear regression reveals significant improvements in airway resistance after terbutaline, indicating its utility in studying infant lung mechanics.
Area of Science:
- Neonatal Physiology
- Respiratory Mechanics
- Computational Biology
Background:
- Intubated premature infants often exhibit abnormal lung mechanics, characterized by curvilinear flow-volume plots.
- Conventional linear analysis methods may not accurately reflect lung mechanics in these patients.
- Existing methods for quantifying plot curvature have limitations.
Purpose of the Study:
- To develop and validate a microcomputer-based nonlinear regression algorithm for analyzing lung mechanics in premature infants.
- To assess the effect of terbutaline on respiratory system resistance (Rrs), compliance (Crs), and expiratory time constants (TCrs) in very low birth weight infants.
- To compare the findings from nonlinear analysis with conventional linear methods.
Main Methods:
- Developed a microcomputer-based, reiterative regression algorithm optimizing a nonlinear function for data fitting.
- Studied six very low birth weight infants with clinical evidence of pulmonary gas trapping.
- Measured Rrs, Crs, and TCrs using passive deflation before and after terbutaline administration.
- Analyzed data using nonlinear regression based on a two-compartment model of parallel inhomogeneities.
Main Results:
- Conventional linear analysis showed no change in lung mechanics after terbutaline.
- Nonlinear regression revealed two compartments: one normal, and a second with very high Rrs.
- The high Rrs in the second compartment decreased by 50% after terbutaline administration.
- Terbutaline did not significantly affect heart rate.
Conclusions:
- Abnormalities in airway resistance in ventilated preterm infants may not be identifiable by classic linear analysis.
- Nonlinear regression techniques, particularly those based on compartmental models, offer a more sensitive approach to characterizing lung mechanics in this population.
- The findings suggest potential therapeutic targets for improving airway resistance in premature infants.