title: Inspiratory capacity at inflation hold in ventilated newborns: a surrogate measure for static compliance of the respiratory system.
abstract: OBJECTIVE
  To study appropriateness of respiratory system compliance calculation using an inflation hold and compare it with ventilator readouts of pressure and tidal volume as well as with measurement of compliance of the respiratory system with the single-breath-single-occlusion technique gained with a standard lung function measurement.
  
  
  METHODS
  Prospective clinical trial.
  
  
  METHODS
  Level III neonatal unit of a university hospital.
  
  
  METHODS
  Sixty-seven newborns, born prematurely or at term, ventilated for a variety of pathologic conditions.
  
  
  METHODS
  A standardized sigh maneuver with a predefined peak inspiratory pressure of 30 cm H2O, termed inspiratory capacity at inflation hold, was applied. Using tidal volume, exhaled from inspiratory pause down to ambient pressure, as displayed by the ventilator, and predefined peak inspiratory pressure, compliance at inspiratory capacity at inflation hold conditions could be calculated as well as ratio of tidal volume and ventilator pressure using tidal volume and differential pressure at baseline ventilator settings: peak inspiratory pressure minus positive end-expiratory pressure.
  
  
  RESULTS
  For the whole cohort, the equation for the regression between tidal volume at inspiratory capacity at inflation hold and compliance of the respiratory system was: compliance of the respiratory system = 0.052 * tidal volume at inspiratory capacity at inflation hold - 0.113, and compliance at inspiratory capacity at inflation hold conditions was closely related to the standard lung function measurement method of compliance of the respiratory system (R = 0.958). In contrast, ratio of tidal volume and ventilator pressure per kilogram calculated from the ventilator readouts and displayed against compliance of the respiratory system per kilogram yielded a broad scatter throughout the whole range of compliance; both were only weakly correlated (R = 0.309) and also the regression line was significantly different from the line of identity (p < .05). Peak inspiratory pressure at study entry did not affect the correlation between compliance at inspiratory capacity at inflation hold conditions and compliance of the respiratory system.
  
  
  CONCLUSIONS
  After a standard sigh maneuver, inspiratory capacity at inflation hold and the derived quantity compliance at inspiratory capacity at inflation hold conditions can be regarded as a valid, accurate, and reliable surrogate measure for standard compliance of the respiratory system in contrast to ratio of tidal volume and ventilator pressure calculated from the ventilator readouts during ongoing mechanical ventilation at respective ventilator settings.
authors.affiliation: Department of Pediatrics and Adolescent Medicine, Division of Neonatology/Intensive Care, University Hospital of Freiburg, Freiburg, Germany. roland.hentschel@uniklinik-freiburg.de
authors.forename: Roland
authors.initials: R
authors.lastname: Hentschel
authors.forename: Nicole
authors.initials: N
authors.lastname: Semar
authors.forename: Josef
authors.initials: J
authors.lastname: Guttmann
mesh_terms: D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007320:Inspiratory Capacity; D015931:Intensive Care, Neonatal / Q000379:methods*; D008170:Lung Compliance; D011312:Pressure; D012121:Respiration, Artificial; D012131:Respiratory Insufficiency / Q000503:physiopathology* / Q000628:therapy; D015656:Respiratory Mechanics / Q000502:physiology*; D013990:Tidal Volume