Using inhaled sodium bicarbonate as a catalyst for hemoglobin's oxygen uptake improve respiratory distress: a two-cases report

Abstract

Acidosis decreases hemoglobin's affinity for oxygen. It shifts the oxyhemoglobin dissociation curve to the right side, thus facilitating the release of oxygen at the tissue level. This is the Bohr effect. The opposite of the Bohr effect can be seen operating in the lungs. Under the law of gas diffusion, carbon dioxide leaves the blood, where its concentration is higher, to diffuse into the alveoli. With the release of carbon dioxide, the pH of the blood in the pulmonary capillaries increases, creating an alkaline environment that reverses the Bohr effect, increases hemoglobin's affinity for oxygen, and facilitates its uptake. Authors reported the clinical cases of two patients admitted to the intensive care unit of the Kinshasa University Hospital for respiratory distress whose arterial oxygen saturation was improved by using inhaled sodium bicarbonate in addition to the mechanical ventilation. These patients were placed under a high-concentration mask, then intubated and ventilated with 100% FiO2, a tidal volume of 6 ml/Kg and a PEEP greater than 5 cm of water, but remained hypoxic despite a slight increase in arterial oxygen saturation. It was ultimately the addition of sodium bicarbonate, used here as a humidifier and alkalizer, that improved arterial oxygen saturation for both patients. Presumably that alkalinization of pulmonary capillaries may have increased hemoglobin's affinity for oxygen, thereby explaining greater hemoglobin saturation and, consequently, the correction of hypoxia. Received: July 15th, 2025 Accepted: November 8th, 2025 https://dx.doi.org/10.4314/aamed.v19i1.19