Effects of bicarbonate on oxyhaemoglobin desaturation and exercise performance in athletes.

AIM: Decrease in peripheral oxygen delivery may impact exercise performance in athletes with exercise-related arterial oxygen desaturation (ERD). We evaluated whether sodium bicarbonate ingestion would be effective to reduce ERD and what is the consequences upon exercise performance. METHODS: Seventy highly trained athletes performed an incremental treadmill cardiopulmonary exercise test (incCPX) and a high intensity constant speed test (ctCPX) on separate days. Subjects who developed ERD by pulse oximetry were randomly allocated to oral sodium bicarbonate or placebo during 5 days. At the end of treatment subjects repeated both tests. RESULTS: ERD prevalence was 33% during the incCPX (17 % severe, 48% moderate and 35% mild) and 34% (5 % severe, 37% moderate and 58% mild) in the ctCPX. Athletes who developed ERD have greater aerobic capacity (incCPX) and endurance time (ctCPX). Active treatment, but not placebo, reduced ERD during ctCPX (P<0.05). However, there were no significant positive effects on main parameters of aerobic function and endurance exercise capacity (P>0.05). CONCLUSION: Sodium bicarbonate was effective in lessening ERD during ctCPX in athletes. However, this intervention failed to improve maximal and submaximal exercise capacity in these subjects.

Respiratory muscle unloading improves leg muscle oxygenation during exercise in patients with COPD.

BACKGROUND: Respiratory muscle unloading during exercise could improve locomotor muscle oxygenation by increasing oxygen delivery (higher cardiac output and/or arterial oxygen content) in patients with chronic obstructive pulmonary disease (COPD). METHODS: Sixteen non-hypoxaemic men (forced expiratory volume in 1 s 42.2 (13.9)% predicted) undertook, on different days, two constant work rate (70-80% peak) exercise tests receiving proportional assisted ventilation (PAV) or sham ventilation. Relative changes (Delta%) in deoxyhaemoglobin (HHb), oxyhaemoglobin (O(2)Hb), tissue oxygenation index (TOI) and total haemoglobin (Hb(tot)) in the vastus lateralis muscle were measured by near-infrared spectroscopy. In order to estimate oxygen delivery (Do(2)est, l/min), cardiac output and oxygen saturation (Spo(2)) were continuously monitored by impedance cardiography and pulse oximetry, respectively. RESULTS: Exercise tolerance (Tlim) and oxygen uptake were increased with PAV compared with sham ventilation. In contrast, end-exercise blood lactate/Tlim and leg effort/Tlim ratios were lower with PAV (p<0.05). There were no between-treatment differences in cardiac output and Spo(2) either at submaximal exercise or at Tlim (ie, Do(2)est remained unchanged with PAV; p>0.05). Leg muscle oxygenation, however, was significantly enhanced with PAV as the exercise-related decrease in Delta(O(2)Hb)% was lessened and TOI was improved; moreover, Delta(Hb(tot))%, an index of local blood volume, was increased compared with sham ventilation (p<0.01). CONCLUSIONS: Respiratory muscle unloading during high-intensity exercise can improve peripheral muscle oxygenation despite unaltered systemic Do(2 )in patients with advanced COPD. These findings might indicate that a fraction of the available cardiac output had been redirected from ventilatory to appendicular muscles as a consequence of respiratory muscle unloading.