Overview of cardiopulmonary exercise testing-based studies on ventilatory efficiency in different clinical scenarios in chronic obstructive pulmonary disease (COPD)
| Clinical context | Subjects n | Disease severity | Main results |
| Exercise intolerance | |||
| Palange [13] | 9 | FEV1 <50% | ↑V′E−V′CO2 slope in walking than cycling |
| O’Donnell [14] | 20 | FEV1=34±3% | ↓V′E at a given V′CO2 in CO2 retainers compared with non-retainers |
| Nakamoto [15] | 10 | FEV1=27–70% | V′E−V′CO2 slope not related to increased muscle ergoreflex activity |
| Ofir [16] | 42 | FEV1=91±8% | ↑V′E/V′CO2 nadir in mild COPD with chronic dyspnoea |
| Ora [17] | 36 | FEV1=49±10% | ↓V′E/V′CO2 nadir in obese patients with COPD |
| Paoletti [18] | 16 | FEV1=54±18% | ↓V′E−V′CO2 slope in more extensive emphysema |
| Guenette [19] | 64 | FEV1=86±11% | No sex effect on V′E/V′CO2 nadir |
| Caviedes [20] | 35 | FEV1=59±22% | ↑V′E/V′CO2 nadir associated with lower maximal exercise capacity |
| Chin [21] | 40 | FEV1=87±11% | ↑V′E/V′CO2 with added external dead space in mild COPD |
| Teopompi [22] | 56 | FEV1=26–80% | ↑V′E−V′CO2 intercept related to greater dynamic hyperinflation ↑V′E−V′CO2 slope associated with lower maximal exercise capacity |
| Guenette [23] | 32 | FEV1=93±9% | ↑V′E/V′CO2 throughout incremental exercise in mild COPD |
| Ciavaglia [24] | 12 | FEV1=60±13% | No effect of exercise modality on V′E/V′CO2 in obese patients with COPD |
| Barron [25] | 24 | FEV1=60±13% | V′E/V′CO2 nadir showed excellent test–retest reliability superior to V′E−V′CO2 slope V′E/V′CO2 nadir showed better test–retest reliability in COPD than heart failure |
| O’Donnell [26] | 208 | GOLD 1 and 2 | ↑V′E/V′CO2 throughout incremental treadmill tests in GOLD 1 and 2 |
| Neder [27] | 276 | GOLD 1 to 4 | ↑V′E−V′CO2 slope associated with ventilation inhomogeneity in GOLD 1 and 2 |
| Elbehairy [28] | 40 | FEV1=91±10% | ↑V′E/V′CO2 nadir in GOLD grade 1B with and without chronic bronchitis |
| Neder [29] | 316 | GOLD 1 to 4 | ↑V′E−V′CO2 intercept from GOLD 1 to 4 associated with exertional dyspnoea ↑V′E−V′CO2 slope in GOLD 1 and 2 but lower slopes in GOLD 3 and 4 |
| Elbehairy [30] | 22 | FEV1=94±10% | ↑V′E/V′CO2 associated with greater VD/VT in symptomatic GOLD 1 |
| Faisal [31] | 48 | FEV1=63±22% | ↑V′E/V′CO2 in COPD and ILD presenting with similar resting inspiratory capacity |
| Crisafulli [32] | 51 | FEV1=55±16% | ↑V′E/V′CO2 slope associated with emphysema extension on chest CT |
| Elbehairy [33] | 20 | FEV1=101±13% | Similar V′E/V′CO2 in smokers without COPD and healthy controls |
| Soumagne [34] | 20 | FEV1=−1.02±0.64 z-score | ↑V′E/V′CO2 nadir in asymptomatic smokers with airflow obstruction |
| Jones [35] | 19 | FEV1=82±13% | ↑V′E/V′CO2 nadir associated with emphysema extension and lower transfer factor |
| Influence of co-morbidities | |||
| Holverda [36] | 25 | NA | ↑V′E/V′CO2 nadir associated with mean pulmonary artery pressure |
| Vonbank [37] | 42 | FEV1=1.1±0.5 L | ↑ Rest and peak V′E/V′CO2 in patients with associated PAH |
| Boerrigter [38] | 47 | FEV1=55±17% | Pronounced ↑ V′E−V′CO2 slope in a sub-group (n=9) with severe PAH |
| Thirapataratong [39] | 48 | FEV1=31±10% | No effect of β-blockers on V′E/V′CO2 nadir |
| Thirapataratong [40] | 98 | FEV1=20±7% | No association of peak V′E/V′CO2 with PAH in severe to very severe COPD |
| Teopompi [41] | 46 | FEV1=52±16% | ↓V′E−V′CO2 slope in COPD compared with heart failure in patients with poorer exercise capacity ↑V′E−V′CO2 intercept in COPD compared with heart failure |
| Thirapataratong [42] | 108 | FEV1=26±14% | ↑V′E/V′CO2 nadir in COPD patients with coexistent coronary artery disease |
| Apostolo [43] | 95 | FEV1=53±13% | ↑V′E−V′CO2 intercept in COPD and COPD- heart failure compared with heart failure |
| Arbex [44] | 98 | FEV1=55±17% | ↑V′E−V′CO2 slope and V′E/V′CO2 nadir in COPD- heart failure compared with COPD ↓V′E−V′CO2 intercept in COPD- heart failure compared with COPD |
| Rocha [45] | 68 | FEV1=60±18% | ↑V′E−V′CO2 slope in COPD- heart failure with exercise oscillatory ventilation |
| Risk assessment/prognosis | |||
| Torchio [46] | 145 | FEV1=73±16% | V′E−V′CO2 slope ≥34 predicted mortality after lung resection surgery |
| Brunelli [47] | 225 | FEV1=81±18% | V′E−V′CO2 slope ≥35 predicted poor outcome after lung resection surgery |
| Shafiek [48] | 55 | FEV1=60±17% | V′E−V′CO2 slope >35 predicted poor outcome after lung resection surgery |
| Neder [49] | 288 | FEV1=18–148% | V′E/V′CO2 nadir >34 added to resting hyperinflation to predict mortality |
| Alencar [50] | 30 | FEV1=57±17% | V′E/V′CO2 nadir >34 and right ventricular function predicted mortality in COPD–heart failure |
| Effects of interventions | |||
| Orens [51] | 5 | FEV1=57±4% | Single lung transplant decreased V′E/V′CO2 peak |
| Somfay [52] | 10 | FEV1=31±10% | Decrements in V′E with hyperoxia correlated with decreases in V′CO2 |
| O’Donnell [53] | 11 | FEV1=31±3% | Proportional decrements V′E and V′CO2 with hyperoxia in advanced COPD |
| O’Donnell [54] | 23 | FEV1=42±3% | Salmeterol proportionally increased V′E and V′CO2 during constant work rate exercise |
| Palange [55] | 12 | FEV1 <50% pred | Heliox increased V′E/V′CO2 during constant work rate exercise |
| O’Donnell [56] | 187 | FEV1=44±13% | ↑V′E (due to higher VT) at a given V′CO2 with tiotropium compared with placebo |
| Porszasz [57] | 24 | FEV1=36±8% | Exercise training proportionally reduced V′E and V′CO2 during constant work rate exercise |
| Bobbio [58] | 11 | FEV1=53±20% | Lobectomy increased V′E−V′CO2 slope |
| Eves [59] | 10 | FEV1=47±17% | Normoxic heliox increased V′E/V′CO2 more than hyperoxic heliox |
| Chiappa [60] | 12 | FEV1=45±13% | Heliox increased V′E/V′CO2 during constant work rate exercise |
| Habedank [61] | 8 | NA | Bilateral lung transplant decreased V′E−V′CO2 slope |
| Gagnon [62] | 8 | FEV1=67±8% | Spinal anaesthesia reduced V′E/V′CO2 during constant work rate exercise |
| Kim [63] | 1475 | FEV1 <45% | LVRS reduced V′E/V′CO2 during unloaded exercise |
| Guenette [64] | 15 | FEV1=86±15% | ↑V′E/V′CO2 at isotime with fluticasone/salmeterol compared with placebo |
| Queiroga [65] | 24 | FEV1=35±10% | Heliox increased V′E/V′CO2 during constant work rate exercise |
| Armstrong [66] | 55 | FEV1=26±7% | LVRS reduced V′E/V′CO2 peak and nadir |
↑: increased; ↓: decreased; FEV1: forced expiratory volume in one second; VʹE: ventilation; VʹCO2: carbon dioxide output; PAH: pulmonary arterial hypertension; GOLD: Global Initiative for Obstructive Lung Disease; ILD: interstitial lung disease; LVRS: lung volume reduction surgery; NA: not available.