Flow-pressure looping during plethysmography in wheezy infants

Pediatr Pulmonol. Jan-Feb 1985;1(1):27-31. doi: 10.1002/ppul.1950010108.


Marked looping of the expiratory portion of the flow-pressure relationship was noted in some infants during measurements of airway resistance in a whole-body plethysmograph while the respired air was maintained at body temperature and humidity. An investigation of 13 infants who had varying degrees of airway obstruction showed that there was a negative correlation (r = 0.72) between the severity of the looping and specific airway conductance (SGaw). An even stronger correlation (r = 0.85) was found between the tangent of the angle of phase lag between flow and pressure (theta) and the forced expiratory time constant (t) obtained from the partial forced expiratory flow-volume curve. Such a relationship would be predicted from a model in which the lung behaved as a simple electrical resistance-capacitance network during expiration. It is suggested that the looping is the result of small airway closure during expiration in wheezy infants, with a consequent rise in resistance and prolongation of the time constant of the lung.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Airway Resistance*
  • Forced Expiratory Flow Rates
  • Humans
  • Infant
  • Plethysmography, Whole Body
  • Respiratory Sounds / diagnosis*
  • Respiratory Tract Diseases / diagnosis*