Respiratory Acidosis in the Intensive Care Unit

Abstract

This chapter explains that the interpretation of acid–base abnormalities is an essential skill required when caring for critically ill patients. The differential causes of respiratory acidosis include central nervous system depression, upper and lower airway obstruction, and hypermetabolic states with increased production of CO2, such as malignant hyperthermia and thyroid storm. The treatment for hypoxic and hypercarbic respiratory failure involves reversing the offending agents if applicable, treatment of the underlying cause, and mechanical ventilation. The 2 commonly used strategies for mechanical ventilation are non-invasive ventilation with a mask and endotracheal intubation. The selection of ventilation strategy is dependent on numerous patient factors. Clinicians must set respiratory rate, tidal volume, positive end-expiratory pressure, inspiratory flow, fraction of inspired oxygen, mode (volume versus pressure control), and the amount of assistance per breath. All need to be tailored toward each patient’s specific goals. In patients with severe acidosis, there may be a temptation to hyperventilate in order to treat the hypercarbia and hypoxia as quickly as possible. This can be deleterious as high tidal volumes may lead to ventilator-induced lung injury due to volutrauma, cytotrauma, and barotrauma.