P142 Chaotic breathing in post COVID-19 breathlessness: a key feature characterised by approximate entropy

P142 Table 1Baseline characteristics and exercise measurements Post COVID-19 BPD (N = 20) Non-COVID BPD (N = 20) Healthy controls (N = 15) BASELINE CHARACTERISTICS Age/years 41 (10) 49 (14) 50 (18) Gender M:F 6:14 6:14 9:6 BMI (kg/m2) 25 (4) 26 (5) 25 (4) Nijmegen score (/64) 23 (12–44) 23 (14–41) - FEV1 (% pred) 111 (13) 107 (16) 96 (6) FVC (% pred) 118 (14) 114 (16) 107 (12) FEV1/FVC Ratio 80 (6) 78 (6) 75 (12) Resting SpO2 (%) 98 (95–100) 99 (94–100) 97 (96–99) Resting HCO3 − (earlobe) (mmol/L) 24 (5) 22 (3) 24 (2) Resting PaCO2 (kPa) 4.4 (0.8) 4.3 (0.7) 4.7 (0.5) Resting BORG CR-10 dyspnoea (/10) 0.7 (0.8) 1.4 (1.3) 0.2 (0.6) PEAK exercise CPET Variables Duration of test (minutes) 10 (4) 9 (2) 15 (3) Main reason cited for exercise cessation Legs = 6 Legs = 8 Legs = 6 Breathing = 14 Breathing = 12 Breathing = 4 BORG CR-10 dyspnoea (/10) End=5.3 (2.3) End=4.2 (1.5) End=4.1 (1.7) Peak VO2 (L/min) 2.18 (0.87) 1.52 (0.62) 2.77 (1.22) Peak VO2 (% predicted) 106.5 (33.1) 79.8 (17.5) 124.8 (27.3) Peak VO2 (mL/min/kg) 29.6 (7.6) 20.7 (7.1) 37.8 (14.8) Peak Heart Rate (beats/min) 170 (12.6) 141 (26) 167 (15) Heart Rate Reserve (beats/min) 20 (19) 30 (20) 2 (13) Peak VE (L/min) 89 (26) 60 (27) 96 (35) Peak Tidal Volume (L) 2.6 (1.3) 1.86 (0.88) 2.37 (0.71) Peak Breathing Frequency (/min) 43 (23) 31 (9) 33 (8) Peak SpO2 (%) 97 (93–100) 99 (94–100) 95 (73–98) PEAK exercise gas exchange values PaO2 (kPa) 13.3 (3.2) 13.8 (1.2) 13.7 (1.2) PaCO2 (kPa) 4.4 (1.1) 4.2 (0.7) 4.1 (0.7) PETCO2 (kPa) 4.4 (0.6) 4.3 (0.5) 4.8 (0.8) P(A-a)O2 difference (kPa) 2.8 (1.2) 2.1 (0.9) 2.6 (0.9) P(a-ET)CO2 difference (kPa) - 0.10 (0.25) −0.09 (0.37) −0.35 (0.53) Approximate entropy (ApEn) of ventilatory variables during incremental exercise ApEn Tidal Volume 1.61 (0.05) 1.28 (0.23) 1.02 (0.29) ApEn Breathing Frequency 1.40 (0.10) 1.41 (0.20) 1.32 (0.21) ApEn Minute Ventilation 1.22 (0.11) 0.97 (0.30) 0.65 (0.23) Data shown as mean (SD) or median (range);M:F: Male:Female;BMI: body mass index;FEV1: forced expiratory volume in the first second;FVC: forced vital capacity;SpO2;oxygen saturation;CPET: cardiopulmonary exercise test;VO2: oxygen consumption;VE:ConclusionsPost COVID BPD can be characterised by application of non-linear statistical modelling of exercise ventilatory data. This approach now needs further validation to facilitate application in automated CPET equipment, to identify and highlight this important differential diagnosis.