Mechanisms affecting exercise ventilatory inefficiency-airflow obstruction relationship in male patients with chronic obstructive pulmonary disease

Table 2 Summary of correlation (r) of \( \dot{\mathrm{V}}\mathrm{E}/\dot{\mathrm{V}}\mathrm{CO}2 \) slope (\( \dot{\mathrm{V}}\mathrm{E}/\dot{\mathrm{V}}\mathrm{CO}2\mathrm{S} \)) and its intercept (\( \dot{\mathrm{V}}\mathrm{E}/\dot{\mathrm{V}}\mathrm{CO}2\mathrm{I} \)) with pulmonary physiology

r	Slope		Intercept
N =	118	46	118	46
Intercept	-0.44^†	−0.40^**	1	1
Expiration
FEV₁%	0.20^*	0.42^**	−0.09	−0.12
FEV₁/VC	0.27^**	0.15	0.02	−0.02
GOLD	−0.26^**	−0.44^**	0.08	0.11
Inspiration
V_T/T_Ipeak	0.20^¶	0.03	0.22^*	0.30^*
Volume excursion/dynamic hyperinflation:
V_Tpeak/FEV₁	−0.15	−0.32^*	0.14	0.18
V_Tpeak/IC	−0.15	−0.05	0.15	−0.00
V_Tpeak/VC	0.01	−0.04	0.02	−0.04
V_Tpeak/TLC	−0.01	−0.06	0.10	0.13
Gas exchange:
S_PO_2peak	0.32^***	0.50^***	0.03	−0.19
P_ETCO_2peak-rest	–	− 0.62^†	–	0.53^***
V_D/V_Trest	–	0.03	–	0.28^¶
V_D/V_Tpeak	–	0.41^**	–	−0.23
Exercise capacity
\( \dot{\mathrm{V}}\mathrm{O}2 \)_peak^θ	−0.33^***	− 0.27^¶	0.28^**	0.27^¶
Work_peak^θ	−0.1	−0.3^*	0.30^***	0.43^**

Abbreviations: FEV₁ forced expired volume in 1 s, VC vital capacity, GOLD stage of global initiatives for chronic obstructive lung disease, V_T/T_Ipeak the ratio of tidal volume and inspiratory time in second indicating mean inspiratory flow, IC inspiratory capacity, TLC total lung capacity, S_PO₂ oxyhemoglobin measured by pulse oximetry, P_ETCO₂ end-tidal CO₂ pressure, \( \dot{\mathrm{V}}\mathrm{O}2 \) oxygen uptake
^θ% of predicted maximum
−-: not available
^¶ 0.05 < p < 0.1
^* < 0.05
^** < 0.01
^*** ≤ 0.001
^†< 0.0001

ISSN: 1465-993X