Airway closure in anesthetized infants and children: influence of inspiratory pressures and volumes
Article first published online: 20 MAY 2002
Acta Anaesthesiologica Scandinavica
Volume 46, Issue 5, pages 529–536, May 2002
How to Cite
Thorsteinsson, A., Werner, O., Jonmarker, C. and Larsson, A. (2002), Airway closure in anesthetized infants and children: influence of inspiratory pressures and volumes. Acta Anaesthesiologica Scandinavica, 46: 529–536. doi: 10.1034/j.1399-6576.2002.460510.x
- Issue published online: 20 MAY 2002
- Article first published online: 20 MAY 2002
- Received 20 August 2001,accepted for publication 10 January 2002
- airway closure;
- sulfur hexafluoride;
- multibreath washout;
- functional residual capacity
Background: Cyclic opening and closing of lung units during tidal breathing may be an important cause of iatrogenic lung injury. We hypothesized that airway closure is uncommon in children with healthy lungs when inspiratory pressures are kept low, but paradoxically may occur when inspiratory pressures are increased.
Methods: Elastic equilibrium volume (EEV) and closing capacity (CC) were measured with a tracer gas (SF6) technique in 11 anesthetized, muscle-relaxed, endotracheally intubated and artificially ventilated healthy children, aged 0.6–13 years. Airway closing was studied in a randomized order at two inflation pressures, +20 or +30 cmH2O, and CC and CC/EEV were calculated from the plots obtained when the lungs were exsufflated to −20 cmH2O. (CC/EEV >1 indicates that airway closure might occur during tidal breathing). Furthermore, a measure of uneven ventilation, multiple breath alveolar mixing efficiency (MBAME), was obtained.
Results: Airway closure within the tidal volume (CC/EEV >1) was observed in four and eight children (not significant, NS) after 20 and 30 cmH2O inflation, respectively. However, CC30/EEV was >CC20/EEV in all children (P≤0.001). The MBAME was 75±7% (normal) and did not correlate with CC/EEV.
Conclusion: Airway closure within tidal volumes may occur in artificially ventilated healthy children during ventilation with low inspiratory pressure. However, the risk of airway closure and thus opening within the tidal volume increases when the inspiratory pressures are increased.