Related Experiment Videos
A new technique to demonstrate flow limitation in partial expiratory flow-volume curves in infants
1Department of Medicine, Children's Hospital, Boston, Massachusetts 02115.
Insights
This study shows that rapid pressure oscillations (RPO) can identify expiratory flow limitation in infants during partial expiratory flow-volume (PEFV) curve generation. The technique is effective, especially in infants with obstructive airway disease.
Area of Science:
- Pediatric Pulmonology
- Respiratory Physiology
- Infant Lung Function Testing
Background:
- Partial expiratory flow-volume (PEFV) curves are crucial for assessing infant lung function.
- Generating reliable PEFV curves requires understanding pressure transmission and identifying flow limitation.
Purpose of the Study:
- To evaluate pressure transmission to and across the infant chest wall during PEFV maneuvers.
- To determine the efficacy of the rapid pressure oscillations (RPO) technique in identifying expiratory flow limitation in infants.
Main Methods:
- Eleven sedated infants underwent chest wall compression using an inflatable jacket.
- Neonatal blood pressure cuffs measured pressure transmission to the chest wall.
- Airway pressure during occlusion assessed pressure transmission to air spaces.
- RPO were superimposed on static jacket pressures to detect flow limitation.
Main Results:
- Pressure transmission to the chest wall was 72% +/- 4% of jacket pressure.
- Pressure transmission to air spaces was 56% +/- 6% of jacket pressure.
- RPO technique identified flow limitation in all infants at jacket pressures >50 cmH2O, and in 4 infants with obstructive airway disease at <30 cmH2O.
Conclusions:
- Significant pressure loss occurs across the inflatable jacket and infant chest wall.
- The RPO technique is a valuable tool for recognizing expiratory flow limitation during infant PEFV curve generation.
- RPO facilitates earlier detection of flow limitation, particularly in infants with obstructive airway disease.
Abstract:
Partial expiratory flow-volume (PEFV) curves in infants are generated by applying a compressive pressure over the chest wall with an inflatable jacket. This study addresses two issues: pressure transmission to and across the chest wall and whether flow limitation can be identified. Eleven infants sedated with chloral hydrate were studied. Pressure transmission to the chest wall, measured with neonatal blood pressure cuffs placed on the infant's body surface, was 72 +/- 4% of jacket pressure during compression maneuvers. The pressure transmission to the air spaces, determined by measuring airway pressure during a compression maneuver against an occluded airway, was 56 +/- 6% of jacket pressure. A significant amount of the applied pressure is therefore lost across both the jacket and chest wall. Rapid pressure oscillations (RPO) were superimposed on static jacket pressures while expiratory flow was measured. Absence of associated oscillations of flow measured at the mouth was taken to indicate that flow was independent of driving pressure and therefore limited. Flow limitation was demonstrable with the RPO technique in all infants for jacket pressures greater than 50 cmH2O; however, it was evident at jacket pressures less than 30 cmH2O jacket pressure in four infants with obstructive airway disease. The RPO technique is a useful adjunct to the compression maneuver utilized to generate PEFV curves in infants because it facilitates the recognition of expiratory flow limitation.