• If respiratory acidosis is present, identify the precipitating factors and assess whether the symptoms (hypoxemia, hypercapnia, and acidosis) are themselves life threatening.
• There are no threshold values for PaO2, PaCO2, and pH which dictate symptomatic correction. The indications for mechanical support are based on global clinical assessment (age, consciousness, cardiovascular stability, and trend of respiratory impairment).
• Assessment of the precipitating factors and the time required for their correction is of paramount importance in planning therapeutic strategy.
• The target blood gases during respiratory support must be established according to the previous respiratory conditions.
• Since hyperinflation of the lung, with its cardiovascular consequences, is the most harmful complication of mechanical ventilation in chronic respiratory acidosis, it is essential to set a small tidal volume associated with an adequate expiratory time.
• Non-invasive ventilation appears to be a promising treatment of chronic respiratory acidosis.
• Infusion of HCO3- to correct acidosis may be appropriate only if the decrease in pH is itself harmful, the infusion rate is titrated against the increase in PaCO2, the ventilation can be increased to clear the extra CO 2 generated, and the cardiac output is adequate. In these conditions HCO 3- administration is equivalent to an acceleration of the natural process in the kidneys (if renal control is adequate).
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