Abnormal ventilatory responses during cardiopulmonary exercise testing in children with upper airway obstruction. Why am I short of breath when I have a large reserve?

<bold>Background:</bold> Cardiopulmonary exercise testing (CPET) is used to assess for ventilatory limitation. This will often be identified by a breathing reserve (BR%) <15% of the maximal voluntary ventilation. We have identified a cohort of patients with varying diagnoses which cause upper airway obstruction (UAO) who display abnormal ventilatory responses during CPET and evidence of ventilatory limitation with a high BR%. <bold>Aim:</bold> To evaluate the ventilatory responses during CPET in children with UAO and compare this to a control group (CON). To describe a unique pattern of ventilation during CPET in UAO. <bold>Methods:</bold> A retrospective analysis of results from patients referred from Ear Nose & throat with UAO. These were compared to a CON group who had been referred for CPET with exercise induced dyspnoea. <bold>Results:</bold> 13 patients with UAO performed CPET (4 males) and 13 age & sex matched CONs. Mean age was 12.4 ±2.9. Results from peak exercise are shown in the table. The UAO group had a significantly lower VO_2peak (VO₂%), peak ventilation (V_Epeak), breathing frequency (BF), higher BR% and end tidal CO₂ (ETCO₂₎ (p<0.05). Mean & 95%CI <bold>Discussion:</bold> We have shown that UAO shows a unique pattern of ventilatory limitation during CPET. This is presented as low peak ventilation which is primarily due to a low breathing frequency. This results in elevated CO₂ levels, a high BR% and the inability to achieve a RCP. <table-wrap><object-id>erj;64/suppl_68/PA2606/TB1</object-id><object-id>T1</object-id><object-id>TB1</object-id><table><colgroup><col></col><col></col><col></col></colgroup><tbody><tr><td></td><td>UAO</td><td>CON</td></tr><tr><td>VO2%</td><td>80 (67, 92)</td><td>114 (100, 127)</td></tr><tr><td>V_Epeak(L/min)</td><td>39 (31, 46)</td><td>73 (59, 87)</td></tr><tr><td>BF(min⁻¹)</td><td>35 (30, 40)</td><td>55 (49, 61)</td></tr><tr><td>Tidal Volume(ml/min)</td><td>1115 (952, 1276)</td><td>1373 (1083, 1664)</td></tr><tr><td>BR%</td><td>44 (37, 50)</td><td>26 (19, 32)</td></tr><tr><td>ETCO₂(kPa)</td><td>5.44 (5.05, 5.83)</td><td>4.38 (4.06, 4.70)</td></tr></tbody></table></table-wrap>