What acid-base imbalance is caused by sleep?

From the Guidelines

Sleep can cause respiratory acidosis due to hypoventilation, as evidenced by an increase in PaCO2 during sleep compared to awake supine values. This is supported by the American Academy of Sleep Medicine's definition of "sleep hypoventilation" as a ≥ 10 mm Hg increase in PaCO2 during sleep compared to an awake supine value 1. During sleep, the body's respiratory rate and depth can decrease, leading to a decrease in ventilation and an increase in PaCO2. This can cause a shift in the acid-base balance towards acidosis.

Some key points to consider include:

• The definition of hypoventilation during sleep is an increase in PaCO2 of ≥ 10 mm Hg compared to awake supine values 1
• Patient A and B in Table 7 of the study 1 meet the criteria for hypoventilation according to the 2007 AASM scoring manual, with a 10 mm Hg increase in PaCO2 during sleep
• The Center for Medicare and Medicaid services (CMS) has added a hypoventilation category for patient qualification for a respiratory assist device, which includes a daytime PaCO2 ≥ 45 mm Hg and either a PaCO2 during sleep or immediately on awakening that is ≥ 7 mm Hg greater than the awake PaCO2 1

In terms of treatment, addressing the underlying sleep disorder is crucial to preventing acid-base imbalances. This can include the use of continuous positive airway pressure (CPAP) therapy for obstructive sleep apnea (OSA), as well as other interventions such as weight loss, positional therapy, and surgical interventions. The goal of treatment is to maintain airway patency during sleep and prevent the hypercapnia that leads to acidosis, thereby maintaining acid-base homeostasis and preventing the development of respiratory acidosis.

From the Research

Acid-Base Imbalance Caused by Sleep

• Sleep disorders such as obstructive sleep apnea syndrome (OSAS) can lead to acid-base imbalance, characterized by increased lactate levels and decreased pH 2.
• The use of continuous positive airway pressure (CPAP) treatment can reduce serum lactate and increase pH in OSAS patients, alleviating acid-base balance disorders 2.
• Idiopathic central sleep apnea (ICSA) is associated with chronic hyperventilation, leading to decreased PCO2 levels and increased ventilatory responsiveness to CO2 3.
• Respiratory acidosis, a condition characterized by increased arterial partial pressure of carbon dioxide, can occur due to various factors, including alveolar hypoventilation, abnormal respiratory drive, and increased dead space 4, 5.

Types of Acid-Base Imbalance

• Respiratory acidosis can be acute or chronic, with chronic respiratory acidosis resulting in sustained increases in arterial partial pressure of carbon dioxide and renal adaptation 4, 5.
• Metabolic compensation, such as increased bicarbonate reabsorption, can occur in response to respiratory acidosis 5.
• Hypocapnia, or decreased PCO2, can also occur in sleep disorders, such as ICSA, due to chronic hyperventilation 3.

Treatment and Management

• CPAP treatment is effective in improving symptoms and quality of life in patients with sleep apnea/hypopnea syndrome, and can also alleviate acid-base balance disorders 2, 6.
• Treatment of respiratory acidosis may include invasive or noninvasive ventilatory support and specific medical therapies directed at the underlying pathophysiology 4.