Related Experiment Videos
Problems with plethysmographic estimation of lung volume in infants and young children
Insights
Estimating lung volume in infants using plethysmography can be inaccurate. Performing airway occlusions at higher lung volumes and noting pressure changes improves accuracy for lung volume and airway resistance measurements.
Area of Science:
- Pediatric Pulmonology
- Respiratory Physiology
Background:
- Plethysmographic techniques are commonly used to estimate lung volumes and airway resistance.
- Accurate measurement of these parameters is crucial for diagnosing and managing cardiopulmonary illnesses in infants and young children.
Purpose of the Study:
- To investigate potential errors in lung volume estimation using plethysmography in infants and young children.
- To identify methods to improve the accuracy of these measurements in this age group.
Main Methods:
- Studied 57 infants and young children (<2 years) with cardiopulmonary illnesses.
- Utilized airway occlusions at varying lung volumes during plethysmography.
- Measured changes in intraesophageal pressure (Pes) and mouth pressure (Pm).
Main Results:
- Inconsistent thoracic gas volume (TGV) calculations were observed when occlusions were performed at low versus high lung volumes.
- Discrepancies between Pes and Pm changes indicated potential airway issues.
- Performing occlusions at higher lung volumes and using Pes-derived TGV improved agreement with specific resistance (sRaw) and total pulmonary resistance (TPR) derived volumes.
Conclusions:
- Plethysmographic techniques may yield inaccurate lung volume estimations in young children due to airway closure.
- Performing airway occlusions at lung volumes above functional residual capacity and considering the Pes/Pm pressure ratio can mitigate errors.
- Proposed two lung models (segmental and generalized airway closure) to explain observed discrepancies.
Abstract:
In 57 infants and very young children, less than 2 yr of age and with a variety of cardiopulmonary illnesses, problems were encountered in the estimation of lung volume with the plethysmographic technique. In 19 subjects calculated thoracic gas volume (TGV) was found to be consistently larger when airway occlusions were performed at low lung volumes than when performed at higher lung volumes. In 13 infants, changes in intraesophageal pressure (Pes) during airway occlusions were found to be larger than simultaneous changes in mouth pressure. In 25 subjects in whom none of the above changes were observed, total pulmonary resistance (TPR) and airway resistance (Raw) did not differ significantly [mean TPR, 50.1 +/- 27.5 cmH2O X l-1; mean Raw, 48.1 +/- 26.5 (P greater than 0.5)]. In the 13 subjects in whom the delta Pes-to-delta Pm occlusion ratio exceeded 1.05, closest agreement with specific resistance (sRaw) and TPR derived lung volume was found when TGV was calculated with delta Pes rather than mouth pressure change (delta Pm). A similar close agreement with the sRaw TPR derived volume was obtained when TGV was calculated during airway occlusions at the higher lung volume. Two separate lung models are proposed to explain these observations, one with a segmental airway closure and the other with more a generalized airway closure. If plethysmographic techniques are to be used in these young subjects for the estimation of lung volume and airway resistance, possible errors may be reduced by performing airway occlusions at lung volumes above functional residual capacity and noting the delta Pes-to-delta Pm ratio obtained during the occlusion.