What electrolyte is often assessed in emphysema patients that is low when chronic ventilatory failure is present

In emphysema patients, particularly those experiencing chronic ventilatory failure, the electrolyte that is often assessed and tends to be low is ** bicarbonate (HCO3-)**.

Chronic ventilatory failure can lead to respiratory acidosis due to the accumulation of carbon dioxide (CO2) in the blood, resulting in an increase in carbonic acid (H2CO3) levels. To compensate for the acidosis, the kidneys may retain bicarbonate to help buffer the excess acid, but in the case of chronic respiratory failure, bicarbonate levels can become low if the patient's ability to compensate is overwhelmed.

Assessing bicarbonate levels is important in the management of emphysema and other chronic obstructive pulmonary diseases (COPD), as it provides insights into the acid-base balance and the severity of respiratory failure.