AUTHOR=Bokov Plamen , Peiffer Claudine , Gallego Jorge , Pautrat Jade , Matrot Boris , Delclaux Christophe 

TITLE=A decrease in plant gain, namely CO2 stores, characterizes dysfunctional breathing whatever its subtype in children

JOURNAL=Frontiers in Physiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2023.1217391

DOI=10.3389/fphys.2023.1217391

ISSN=1664-042X

ABSTRACT=<p><bold>Background:</bold> Whether dysfunctional breathing (DB) subtype classification is useful remains undetermined. The hyperventilation provocation test (HVPT) is used to diagnose DB. This test begins with a 3-min phase of hyperventilation during which fractional end-tidal CO<sub>2</sub> (FETCO<sub>2</sub>) decreases that could be an assessment of plant gain, which relies on CO<sub>2</sub> stores. Our aim was to assess 1) whether the children suffering from different subtypes of DB exhibit decreased plant gain and 2) the relationships between HVPT characteristics and plant gain.</p><p><bold>Methods:</bold> We retrospectively selected 48 children (median age 13.5 years, 36 females, 12 males) who exhibited during a cardiopulmonary exercise test either alveolar hyperventilation (transcutaneous PCO<sub>2</sub> &lt; 30 mmHg, <italic>n</italic> = 6) or inappropriate hyperventilation (increased VE’/V’CO<sub>2</sub> slope) without hypocapnia (<italic>n</italic> = 18) or dyspnea without hyperventilation (<italic>n</italic> = 18) compared to children exhibiting physiological breathlessness (dyspnea for sports only, <italic>n</italic> = 6). These children underwent tidal-breathing recording (ventilation and FETCO<sub>2</sub> allowing the calculation of plant gain) and a HVPT.</p><p><bold>Results:</bold> The plant gain was significantly higher in the physiological group as compared to the dyspnea without hyperventilation group, <italic>p</italic> = 0.024 and hyperventilation without hypocapnia group, <italic>p</italic> = 0.008 (trend for the hyperventilation with hypocapnia group, <italic>p</italic> = 0.078). The slope of linear decrease in FETCO<sub>2</sub> during hyperventilation was significantly more negative in physiological breathlessness group as compared to hyperventilation without hypocapnia group (<italic>p</italic> = 0.005) and dyspnea without hyperventilation group (<italic>p</italic> = 0.049).</p><p><bold>Conclusion:</bold> The children with DB, regardless of their subtype, deplete their CO<sub>2</sub> stores (decreased plant gain), which may be due to intermittent alveolar hyperventilation, suggesting the futility of our subtype classification.</p>