title: Relationship between respiratory impedance and positive end-expiratory pressure in mechanically ventilated neonates.
abstract: OBJECTIVE
  To evaluate the feasibility of forced oscillation technique (FOT) measurements at the bedside and to describe the relationship between positive end-expiration pressure (PEEP) and lung mechanics in different groups of ventilated infants.
  
  
  METHODS
  Twenty-eight infants were studied: 5 controls, 16 newborns with respiratory distress syndrome (RDS) and 7 chronically ventilated newborns that developed bronchopulmonary dysplasia. An incremental/decremental PEEP trial was performed by changing PEEP in 1-min steps of 1 cmH(2)O between 2 and 10 cmH(2)O. Forced oscillations at 5 Hz were superimposed on the ventilator waveform. Pressure and flow, measured at the inlet of the ETT, were used to compute resistance (Rrs) and reactance (Xrs).
  
  
  RESULTS
  In controls Rrs and Xrs were on average 41 ± 21 and -22 ± 6 cmH(2)O s/l respectively and were almost unaffected by PEEP. RDS infants presented similar Rrs (48 ± 25 cmH(2)O s/l) and reduced Xrs (-71 ± 19 cmH(2)O s/l) at the beginning of the trial. Two behaviours were observed as PEEP was increased: in extremely low birth weight infants Xrs decreased with PEEP with marked hysteresis; in very low and low birth weight infants Xrs and Rrs were less PEEP dependent. Chronically ventilated infants had very high Rrs and very negative Xrs values at very low PEEPs (121 ± 41 and -95 ± 13 cmH(2)O s/l at PEEP = 2 cmH(2)O) that markedly changed as PEEP exceeded 3-4 cmH(2)O.
  
  
  CONCLUSIONS
  Rrs and Xrs measurement in preterm newborns is feasible, and data are representative of the lung mechanics and very sensitive to its changes with PEEP, making FOT a promising technique for the non-invasive bedside titration of mechanical ventilation in preterm newborns.
authors.affiliation: Dipartimento di Bioingegneria, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan, Italy. raffaele.dellaca@polimi.it
authors.forename: Raffaele L
authors.initials: RL
authors.lastname: Dellacà
authors.forename: C
authors.initials: C
authors.lastname: Veneroni
authors.forename: V
authors.initials: V
authors.lastname: Vendettuoli
authors.forename: E
authors.initials: E
authors.lastname: Zannin
authors.forename: P G
authors.initials: PG
authors.lastname: Matassa
authors.forename: A
authors.initials: A
authors.lastname: Pedotti
authors.forename: M
authors.initials: M
authors.lastname: Colnaghi
authors.forename: F
authors.initials: F
authors.lastname: Mosca
mesh_terms: D017097:Electric Impedance; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D011175:Positive-Pressure Respiration; D012121:Respiration, Artificial; D012127:Respiratory Distress Syndrome, Newborn / Q000503:physiopathology* / Q000628:therapy*