Airway resistance estimation by best fit analysis in very premature infants

M Thomas, A Greenough, R Blowes, G F Rafferty, S Calvert, N Marlow, J L Peacock, A D Milner

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Plethysmographic measurement of airway resistance (R-aw) has been determined by single-point analysis, usually at 50% of maximum inspiratory flow (MIF). Computer-assisted (best fit) analysis, however, allows R-aw to be calculated by applying a regression line to any portion of the plethysmograph pressure-flow loop. We determined whether the results of best fit analysis using a computer program, sampling at 200 Hz, were influenced by the portion of the inspiratory loop analysed and if best fit or single-point analysis gave more reproducible results. Twenty infants of median gestational age 26 (range 24-28) weeks, were studied at a median age of 12 (12-14) months corrected for prematurity. R-aw was calculated by best fit analysis between 0 and 33% MIF, 0 and 50% MIF and 0 and 67% MIF and single-point analysis at 50% of MIF. Similar mean R-aw values were obtained by best fit analysis between 0 and 33% MIF (2.79 kPa/(1/s)) and 0 and 50% MIF (3.01 kPa/(1/s)) and single-point analysis at 50% MIF (2.86 kPa/(1/s)), but best fit analysis between 0 and 67% gave higher results (3.60 kPa/(1/s)), p <0.0001, Within the linear portion of the inspiratory loop. the mean intrasubject coefficient of variation was lowest for best fit analysis between 0 and 50% MIF. Best fit computerized analysis between 0 and 50% MIF is recommended as the analysis of choice.
Original languageEnglish
Pages (from-to)279 - 285
Number of pages7
JournalPhysiological Measurement
Issue number2
Publication statusPublished - 2002

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