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Background HVP testing has been used for > 25 years within a service to investigate a patients breathing pattern. The protocol utilises a 3-minute resting phase, then if resting values are within the normal range voluntary hyperventilation (VH) is commenced for 3 minutes followed by recovery monitoring for 3 minutes. Low PETCO2 may cause cardiac arrhythmias, coronary artery spasm and seizures (Kane et al, Seizure.2014) in susceptible patients and therefore if a shorter period of VH could be utilised within the test then this may be safer for patients. Other Services have used a 1 min VH within their protocol.Aim Can the VH stage of the HVPT be reduced from 3 minutes to 1 minute (in keeping with other Services protocol) and still elicit the required reduction in PETCO2?Method Patients that attended for HVPT over 3 months were identified, demographics and clinical details recorded. PETCO2 at 1, 2 and 3 minutes were noted in those patients who progressed to the VH stage and compared using a one-way Anova and post Hoc Tukey analysis.Results 73 patients were identified, 3 were excluded.70 patients were included: 22 being classified as experiencing chronic hyperventilation, 22 acute and 26 showing normal PETCO2 responses. 4 patients with normal PETCO2 had evidence of a breathing pattern disorder (BPD). 48 patients went on to perform VH.A one-way Anova was used to assess whether there was a statistical difference between PETCO2 at 1 minute, 2 minutes, 3 minutes and combinations of all 3.P between all 3= 0.006P between 1 and 2 minutes= 0.002P between 2 and 3 minutes= 0.285P between 1 and 3 minutes= 0.016(Figure 1)Abstract P18 Figure 1Conclusion Data suggests that VH could be reduced from 3 minutes to 2 minutes. ETCO2 at 1 minute is significantly higher than at 2 minutes suggesting that either a change in protocol may be required to reduce ETCO2 to desired level or that 2 minutes of VH is required to reach ‘target’ ETCO2. A standardised protocol for HVPT by the ARTP that offers guidance on protocol and target ETCO2 range would be desirable.