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

ABSTRACT

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 MF 614 614 96 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);MF MaleFemale;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;VEConclusionsPost 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.