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Updated: Feb 18, 2026

Combining Volumetric Capnography And Barometric Plethysmography To Measure The Lung Structure-function Relationship
Published on: January 8, 2019
Physiological and anatomical dead space in mechanically ventilated newborn infants
Theodore Dassios1, Paul Dixon2, Ann Hickey1
1Neonatal Intensive Care Centre, King's College Hospital NHS Foundation Trust, London, United Kingdom.
Objectives:
To compare the anatomical (VD-Ana ) and alveolar dead space (VD-Alv ) in term and prematurely born infants and identify the clinical determinants of those indices.
Working Hypothesis:
VD-Ana and VD-Alv will be higher in prematurely born compared to term born infants.
Study Design:
Retrospective analysis of data collected at King's College Hospital NHS Foundation Trust, London, UK.
Patient Selection:
Fifty-six infants (11 term, 45 preterm) were studied at a median age of 8 (IQR 2-33) days.
Methodology:
VD-Ana was determined using Fowler's method of volumetric capnography. VD-Alv was determined by subtracting VD-Ana from the physiological dead space which was determined by the Bohr-Enghoff equation. VD-Ana and VD-Alv were related to body weight at the time of study.
Results:
The median VD-Ana /kg was higher in prematurely born infants [3.7 (IQR: 3.0-4.5) mL/kg] compared to term infants [2.4 (IQR: 1.9-2.9) mL/kg, adjusted P = 0.001]. The median VD-Alv /kg was not higher in prematurely born infants [0.3 (IQR: 0.1-0.5)] compared to term infants [0.1 (IQR: 0.0-0.2) mL/kg] after adjusting for differences in respiratory rate and days of ventilation (P = 0.482). VD-Ana /kg was related to postmenstrual age (r = -0.388, P < 0.001), birth weight (r = -0.397, P < 0.001), and weight at measurement (r = -0.476, P < 0.001). VD-Alv /kg was related to postmenstrual age (r = -0.254, P < 0.001), birth weight (r = -0.291, P = 0.002), and weight at measurement (r = -0.281, P = 0.003) and related to days of ventilation (r = 0.194, P = 0.044).
Conclusions:
VD-Ana /kg and VD-Alv /kg increased with decreasing weight and gestation. VD-Alv was higher in infants that have undergone prolonged mechanical ventilation.
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