sodium-bicarbonate and Lung-Diseases--Obstructive

Topics: Acetazolamide; Bicarbonates; Carbon Dioxide; Chronic Disease; Humans; Lung Diseases, Obstructive; Medroxyprogesterone; Medroxyprogesterone Acetate; Oxygen; Respiration; Respiration Disorders; Sleep Stages; Sodium Bicarbonate

Patients with severe chronic obstructive pulmonary disease (COPD) are limited in their exercise tolerance by the level of ventilation (VE) they can sustain. We determined whether acutely increasing blood bicarbonate levels decreased acid stimulation to the respiratory chemoreceptors during exercise, thereby improving exercise tolerance. Responses were compared with those obtained during 100% O2 breathing (known to reduce VE in these patients) and to the responses of healthy young subjects. Participants were six patients with severe COPD (forced expired volume in 1 s = 31 +/- 11% predicted) but without chronic CO2 retention and 5 healthy young subjects. Each subject performed three incremental cycle ergometer exercise tests: 1) control, 2) after ingestion of 0.3 g.kg-1 of sodium bicarbonate and 3) while breathing 100% O2. During these tests VE was measured continuously and arterialized venous blood (patients) or arterial blood (healthy subjects) was sampled serially to assess acid base variables. Bicarbonate loading increased standard bicarbonate by 4-6 mmol.L-1 and this elevation persisted during exercise. In both groups, bicarbonate loading resulted in a substantially higher arterial pH; arterial PCO2 was either unchanged (healthy subjects) or mildly (averaging 5 torr) higher (COPD patients). However, in neither group did bicarbonate loading result in an altered VE response to exercise or an increase in exercise tolerance. In contrast, superimposing hyperoxia on bicarbonate ingestion yielded, on average, 24% reduction in VE and 50% increase in peak work rate in the patients (but not in the healthy young subjects). We conclude that acute bicarbonate loading is not an ergogenic aid in patients with severe COPD.

Topics: Adult; Exercise Test; Exercise Tolerance; Female; Forced Expiratory Volume; Humans; Lung Diseases, Obstructive; Male; Respiration; Respiratory Function Tests; Sodium Bicarbonate

Trapping of xenon 133 in the stomach due to gas swallowing can mimic xenon 133 retention in the left lower lobe due to obstructive lung disease on pulmonary ventilation/perfusion studies. In such cases, ingestion of sodium citrate-bicarbonate-simethicone crystals, which form CO2 gas on contact with water, can distend the xenon-containing stomach and allow clear delineation of its gastric location. This approach is useful in selected cases and may help avoid false-positive diagnoses of obstructive airways disease.

Topics: Adult; Antacids; Bicarbonates; Citrates; Citric Acid; Diagnosis, Differential; Drug Combinations; Gases; Humans; Lung; Lung Diseases, Obstructive; Male; Radionuclide Imaging; Sodium Bicarbonate; Stomach; Xenon Radioisotopes