title: Determinants of pulmonary dead space in ventilated newborn infants.
abstract: Pulmonary dead space (VD) is an index of ventilation inhomogeneity and one of the determinants of the magnitude of tidal volume to maintain optimal blood gases.
  
  
  
  To identify the determinants of VDin ventilated newborns and to investigate differences in VDbetween prematurely born and term infants and those prematurely born infants who did or did not develop bronchopulmonary dysplasia (BPD).
  
  
  
  Sixty-one mechanically ventilated infants (15 term, 46 preterm) were studied at a median age of 8 (IQR 2-31) days; 32 of the preterm infants developed BPD. VDwas determined from the difference between arterial and end tidal carbon dioxide (CO2) using a low dead space CO2detector using the Bohr/Enghoff equation and was related to body weight (VD/kg) at the time of study. The time to peak tidal expiratory flow/expiratory time (TPTEF/TE) was measured during spontaneous breathing using a fixed orifice pneumotachograph.
  
  
  
  VD/kg was related to gestational age (r=-0.285, p=0.001), birth weight (r=-0.356, p<0.001), weight (r=-0.316, p<0.001) and postmenstrual age (r=-0.205, p=0.020) at measurement, days of ventilation (r=0.322, p<0.001) and TPTEF/TE(r=-0.397, p=0.003). The median VD/kg was higher in prematurely born infants [2.3 (IQR: 1.7-3.0) ml/kg] compared to term infants [1.5 (1.3-2.1) ml/kg, (p=0.003)] and in premature infants that developed BPD [2.6 (IQR 1.8-3.4) ml/kg] compared to those who did not [1.7 (IQR 1.1-1.9) ml/kg], (p<0.001).
  
  
  
  Numerous factors influence pulmonary dead space and thus an optimum tidal volume will differ according to the underlying demographics and respiratory status.
authors.affiliation: Neonatal Intensive Care Centre, King's College Hospital NHS Foundation Trust, London, UK. Electronic address: theodore.dassios@kcl.ac.uk.
authors.forename: Theodore
authors.initials: T
authors.lastname: Dassios
authors.affiliation: Neonatal Intensive Care Centre, King's College Hospital NHS Foundation Trust, London, UK.
authors.forename: Ourania
authors.initials: O
authors.lastname: Kaltsogianni
authors.affiliation: Division of Asthma, Allergy and Lung Biology, MRC-Asthma UK Centre in Allergic Mechanisms of Asthma, King's College London, UK; National Institute for Health Research (NIHR), Biomedical Research Centre, Guy's and St Thomas' NHS Foundation Trust, King's College London, UK.
authors.forename: Anne
authors.initials: A
authors.lastname: Greenough
mesh_terms: D001997:Bronchopulmonary Dysplasia / Q000209:etiology / Q000503:physiopathology*; D005260:Female; D006801:Humans; D062071:Infant, Extremely Premature / Q000502:physiology*; D007231:Infant, Newborn; D008297:Male; D012121:Respiration, Artificial / Q000009:adverse effects*; D012126:Respiratory Dead Space