Figures
- FIGURE 1
Increases in Borg breathlessness during 20% epochs of cycle-exercise time. Data points represent median and interquartile range.
- FIGURE 2
Tidal volume expressed as a percentage of predicted vital capacity (VT%VCpred) and mean root mean square (RMS) diaphragm electromyogram (EMGdi) activity per breath, expressed as a percentage of maximum RMS EMGdi recorded during maximal inspiratory manoeuvres (EMGdi%max) during 20% epochs of cycle-exercise time. Data points represent median and interquartile range.
- FIGURE 3
A comparison of the relationship between minute ventilation (V′E), breathlessness and the mean root mean square (RMS) diaphragm electromyogram (EMGdi) activity per breath, expressed as a percentage of maximum RMS EMGdi recorded during maximal inspiratory manoeuvres (EMGdi%max) during 20% epochs of cycle-exercise time. V′E and EMGdi%max have been plotted on the same scale to highlight the difference in the slopes of the relationships with breathlessness after the onset of neuroventilatory uncoupling. Data points represent median and interquartile range.
Tables
- TABLE 1 Demographic, anthropometric and lung function data from patients undergoing incremental exercise testing
Age 66.7±6.96 Sex Male 11 Female 1 Height m 1.63±0.06 Weight kg 53.7±7.52 Body mass index kg·m−2 20.2±3.42 Forced expiratory volume in 1 s % predicted 38.7±14.5 Vital capacity % predicted 83.9±20.0 Inspiratory capacity % predicted 82.9±25.7 Total lung capacity# % predicted 120.4±16.1 Residual volume # % predicted 165.9±48.5 -
Data are presented as mean±sd or n. #: n=8.
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- TABLE 2 Symptoms, ventilation, metabolic data, diaphragm electromyogram (EMG) activity and neuroventilatory uncoupling at rest before cycle exercise and at end of exercise
Before exercise End of exercise Work W 30 (20–47.5) Exercise time min 10.7 (8.1–16.8) Borg breathlessness score 0 (0–0.5) 8 (5–10) Borg leg fatigue score 0 (0–0) 5 (4.25–8.75) V′E L·min−1 10 (8.9– 0.7) 23.7 (18.5–29.4) Inspiratory capacity L 1.8 (1.5–1.9) 1.39 (1.0–1.98) Change in inspiratory capacity pre/post exercise mL 270.0 (100.0–440.0) V′O2 mL·kg−1··min−1 3.5 (3.2–4.3) 12.8 (9.8–14.1) V′CO2 mL·kg·min−1 3.6 (3.0–4.0) 12.3 (10.0–15.3) Respiratory exchange ratio 1.0 (0.9–1.1) 1.0 (0.92–1.06) Oxygen saturation % 96.2 (95.1–97.0) 92.3 (90.9–94.5) ti/ttot% 34.1 (32.2–35.3) 33.7 (29.2–34.4) Respiratory rate min−1 21.0 (14–23.7) 28.8 (26.9–34.4) VT mL 476.6 (426.6–607.2) 789.1 (645.4–1008.0) VT%VCpred % 15.7 (13.1–16.8) 23.6 (20.4–33.7) EMGdi%max 16.9 (14.3–20.6) 73.3 (60.6–77.4) EMGdi%max/VT%VCpred 1.05 (0.94–1.31) 2.86 (2.06–3.83) -
Data are presented as mean (IQR). V′E: minute ventilation; V′O2: oxygen uptake, V′CO2: carbon dioxide production; ti/ttot: ratio of inspiratory time to total breath duration; VT: tidal volume; VT%VCpred: tidal volume expressed as a percentage of predicted vital capacity; EMGdi%max: mean root mean square (RMS) diaphragm electromyogram (EMGdi) activity per breath, expressed as a percentage of maximum RMS EMGdi recorded during maximal inspiratory manoeuvres.
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- TABLE 3 Spearman coefficient and p-values for correlations between observed measurements during cycle exercise
Spearman coefficient p-value EMGdi%max 0.98 (0.94–0.99) 0.0001 EMGdi%max/VT%VCpred 0.94 (0.84–0.99) 0.005 V′E 0.96 (0.93–0.99) 0.003 VT%VCpred 0.90 (0.67–0.96) 0.01 -
Date are presented as mean (IQR), unless otherwise stated. EMGdi%max: mean root mean square (RMS) diaphragm electromyogram (EMGdi) activity per breath, expressed as a percentage of maximum RMS EMGdi recorded during maximal inspiratory manoeuvres; VT%VCpred: tidal volume expressed as a percentage of predicted vital capacity; V′E: minute ventilation.
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- TABLE 4 Slopes of the relationships with breathlessness before and the breathlessness threshold
V′E VT%VCpred EMGdi%max EMGdi%max/VT%VCpred Cycle exercise Before 0 (0–2.3) 0 (0–2.6) 0 (0–0.9) 0 (0–1.2) After 10.4 (7.0–19.8) 9.9 (4.1–31.5) 5.7# (3.0–6.6) 6.5 (4.7–15.2) p-value 0.0005 0.1 0.0005 0.0005 -
Data are presented as mean (IQR) unless otherwise stated. V′E: minute ventilation; VT%VCpred: tidal volume expressed as a percentage of predicted vital capacity; EMGdi%max: mean root mean square (RMS) diaphragm electromyogram (EMGdi) activity per breath, expressed as a percentage of maximum RMS EMGdi recorded during maximal inspiratory manoeuvres. #: indicates that the slope of the normalised EMGdi%max and breathlessness relationship was significantly less than the slope of the normalised V′E and breathlessness relationships.
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