Alveolar–capillary reserve during exercise in patients with chronic obstructive pulmonary disease

Figures & data

Table 1 Cardiopulmonary responses to exercise in COPD patients (N=32)

	Rest	First workload	70%–90% of peak	Peak
Exercise capacity
Work (W)	0	18±4	33±14	43±19
VO2 (mL/kg/min)	3.66±0.84	8.34±1.40	10.00±2.50	11.40±3.12
Symptoms
RPE (6–20 Borg Score)	7±2	11±3	15±3	17±2
Dyspnea (0–10 Score)	1±1	3±2	5±2	7±2
Cardiovascular
Heart rate (bpm)	77±10	92±11	100±11	106±12
O2 pulse (VO2/HR)	4.1±0.9	7.8±2.1	8.9±2.7	9.3±3.1
SBP (mmHg)	118±24	137±17	146±20	152±21
DBP (mmHg)	73±10	82±11	86±10	88±11
Ventilation and breathing pattern
Ventilation (L/min)	12±3	24±6	28±9	34±10
Tidal volume (L)	0.79±0.17	1.13±0.37	1.15±0.36	1.17±0.37
Breathing frequency (bpm)	18±6	25±7	28±7	31±5
IC (L)	2.15±0.67	1.89±0.71	1.78±0.83	1.70±0.69
Vt/IC	37±13	52±12	61±25	65±27
VE/breathing capacity (%)	27±9	51±25	58±21	69±21
Gas exchange – pulmonary vascular
VE/VCO2 ratio	47±7	37±5	37±5	36±5
PetCO2 (mmHg)	35±5	37±5	37±5	37±5
PeCO2 (mmHg)	19±3	23±3	24±3	24±3
PeCO2/PetCO2 ratio	0.54±0.04	0.63±0.05	0.66±0.06	0.67±0.06
GxCap	143±40	289±85	317±102	341±116

Notes: Data shown as mean ± standard deviation.

Abbreviations: DBP, diastolic blood pressure; fb, breathing frequency; GxCap, O₂ pulse × PetCO₂; HR, heart rate; IC, inspiratory capacity; O₂ pulse, VO₂/heart rate; PeCO₂, partial pressure of mix expired CO₂; PetCO₂, partial pressure of end tidal CO₂; RPE, rated perceived exertion; SaO₂, arterial oxygen saturation estimated from pulse oximetry; SBP, systolic blood pressure; TI, inspiratory time; TTOT, total respiratory cycle time; VCO₂, carbon dioxide production; V_E, minute ventilation; VO₂, oxygen consumption; V_t, tidal volume.

Table 2 Intrabreath lung diffusing capacity and pulmonary blood flow at rest and during exercise in COPD patients (N=32)

	Rest	First workload	% change	Range, % change
IBDLCO (mL/min/mmHg)	9.6±5.9	13.3±7.1	45%±44%	−22% to 137%
IBQc, L/min*	4.8±0.9	6.6±1.4	40%±28%	0.6% to 123%
Cardiac stroke volume (mL)	62±14	73±20	18±23	36% to 133%
IBDLCO/IBQc	2.01±1.1	2.03±1.0	14%±51%	−50% to 161%

Notes: Data shown as mean ± standard deviation.

* Qc measured with soluble gas method.

Abbreviations: DLCO, lung diffusing capacity for carbon monoxide; IB, intrabreath technique; Qc, pulmonary blood flow.

Figure 1 Change in intrabreath DLCO from rest to first stage of exercise in patients with COPD.

Abbreviation: DLCO, diffusing capacity for carbon monoxide.

Figure 2 Change in intrabreath DLCO relative to Qc from rest to first exercise workload in patients with COPD.

Abbreviations: DLCO, diffusing capacity for carbon monoxide; Qc, pulmonary blood flow measured with soluble gas method.

Figure 3 Relationship of GxCap to DLCO in COPD patients.

Abbreviations: DLCO, diffusing capacity for carbon monoxide; GxCap, O₂ pulse × PetCO₂; PetCO₂, partial pressure of end tidal CO₂.

Figure 4 Relationship of VO₂ peak (A) and VCO₂ peak (B) with DLCO/Qc.

Abbreviations: DLCO, diffusing capacity for carbon monoxide; Qc, pulmonary blood flow; VCO₂, carbon dioxide production; VO₂, oxygen consumption.

Figure 5 Relationship of VO₂ with the change in GxCap from rest to peak exercise.

Abbreviations: GxCap, O₂ pulse × PetCO₂; PetCO₂, partial pressure of end tidal CO₂; VO₂, oxygen consumption.

Figure 6 Relationship of DLCO/Qc relative to IC.

Note: Qc measured with soluble gas method.
Abbreviations: DLCO, diffusing capacity for carbon monoxide; IC, inspiratory capacity; Qc, pulmonary blood flow.