P133 PREDICTION EQUATIONS FOR PULMONARY FUNCTION VALUES IN HEALTHY IRANIAN CHILDREN (AGED

Background Many body systems may be affected by chronic hyperventilation and symptoms may be wide-ranging. There is no obvious cause, no gold standard test and not all patients with Hyperventilation Syndrome (HVS) demonstrate characteristic low resting PaCO2. No previous studies were found that reported the breath-hold time of HVS subjects at functional residual capacity, subjects’ end-tidal carbon dioxideat the breakpoint of breath-hold, the subjective experience of breath-hold or the effect of carbon dioxide inhalation on the perception of breathing discomfort in HVS subjects. Methods Five HVS patients, diagnosed by a respiratory physician, with no organic cause for breathlessness and referred for physiotherapy assessment (females, aged 21e70) and five healthy controls (females, aged 21e28) were studied. Breath-hold tests at total lung capacity (TLC) and functional residual capacity (FRC). Incremental inhalation of CO2 was performed, whilst breathing frequency and volume was unconstrained (‘free’) and when‘fixed’ by a breathing circuit and metronome. Components of minute ventilation were recorded via inductive plethysmography, in addition to end-tidal carbon dioxide (PETCO2). A 100-mm visual analogue scale (VAS) was used to obtain a measure of breathing discomfort during breath-hold tests and CO2 inhalation. The breathlessness experience associated with each CO2 inhalation was assessed with the previously-published D-12 questionnaire.