Related Experiment Videos
Assessment of thoracic gas volume by low-frequency ambient pressure changes in children
R Peslin1, F Marchal, C Gallina
1Unité 14 INSERM de Physiopathologie Respiratoire, Vandoeuvre-les-Nancy, France.
Insights
A new method for measuring thoracic gas volume (TGV) showed promising correlations with existing techniques in children. However, poor reproducibility due to breathing regularity issues prevents its current recommendation for routine clinical use.
Area of Science:
- Respiratory Physiology
- Pulmonary Function Testing
- Pediatric Medicine
Background:
- Accurate measurement of thoracic gas volume (TGV) is crucial for diagnosing and managing pediatric respiratory diseases.
- Existing methods like plethysmography and helium dilution have limitations in pediatric populations.
- A novel method utilizing slow sinusoidal pressure variations was developed to measure TGV.
Purpose of the Study:
- To evaluate the validity and reliability of a new method for measuring thoracic gas volume (TGV) in children aged 4-16 years.
- To compare the new TGV measurement method with established techniques: plethysmography and helium dilution.
- To assess the suitability of the new method for routine use in pediatric pulmonary function testing.
Main Methods:
- The study involved 69 children (4-16 years) with normal respiratory function or obstructive/restrictive lung diseases.
- A new method applied slow sinusoidal ambient pressure variations (0.05 Hz) to measure TGV (TGVapc).
- TGVapc-derived functional residual capacities (FRCapc) were compared with plethysmography (FRCplet) and helium dilution (FRCdil).
Main Results:
- FRCapc showed no significant difference compared to FRCplet in the overall group and subgroups.
- A trend towards lower FRCapc was observed in children with severe obstruction.
- FRCdil was significantly lower than both FRCapc and FRCplet, especially in obstructed children.
- Significant correlations were found between all three methods (p < 0.001).
- The new method demonstrated unacceptably low reproducibility due to difficulties in achieving regular breathing patterns.
Conclusions:
- The new TGV measurement method demonstrates good agreement with plethysmography in children.
- The method's requirement for consistent, regular breathing limits its current applicability and reproducibility.
- The novel method is not recommended for routine use in pediatric pulmonary function testing at this time.
Abstract:
The validity of a new method for measuring thoracic gas volume (TGV) was studied in 69 children, 4-16 yrs old, including twelve normal children and 57 children with an obstructive (n = 38) or restrictive (n = 19) respiratory disease. The method consisted of applying very slow (0.05 Hz) sinusoidal variations of ambient pressure around the body (delta Pam = 40 cmH2O peak to peak) and studying the relationship between delta Pam and the resulting gas displacement at the mouth (Vaw): TGVapc = PB.delta Vaw/delta Pam.cos phi, where PB is barometric minus alveolar water vapour pressure and phi the phase angle between Pam and Vaw. Functional residual capacities derived from TGVapc (FRCapc) were compared to the values obtained by plethysmography (FRCplet) and by helium dilution (FRCdil). FRCapc did not differ significantly from FRCplet in either the entire group (1.75 +/- 0.62 l vs 1.79 +/- 0.45 l) or in the patient subgroups. However, with the new method a trend to slightly lower FRCs was seen in patients with the most obstruction (p less than 0.05). FRCdil was significantly lower than both FRCapc and FRCplet (p less than 0.001), particularly in children with obstruction. Significant correlations were found between the three methods (p less than 0.001). On the other hand, the method investigated requires that the subject breathe very regularly for a period of several minutes. This was rarely achieved, so that the reproducibility of the measurements was unacceptably low. At present, the method cannot be recommended for routine use in 4-16 yr old children.