Airway resistance estimation by best fit analysis in very premature infants.
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/(l/s)) and 0 and 50% MIF (3.01 kPa/(l/s)) and single-point analysis at 50% MIF (2.86 kPa/(l/s)), but best fit analysis between 0 and 67% gave higher results (3.60 kPa/(l/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.
Thomas
M
M
Department of Respiratory Medicine, King's College Hospital, London, UK.
Greenough
A
A
Blowes
R
R
Rafferty
G F
GF
Calvert
S
S
Marlow
N
N
Peacock
J L
JL
Milner
A D
AD
D000403:Airway Resistance; D006801:Humans; D007231:Infant, Newborn; D007232:Infant, Newborn, Diseases / Q000175:diagnosis*; D007234:Infant, Premature; D008171:Lung Diseases / Q000175:diagnosis*; D010991:Plethysmography / Q000379:methods*; D012984:Software