What is the difference between a split-night study and polysomnography (PSG)?

From the Guidelines

A split-night study is recommended over polysomnography for diagnosing obstructive sleep apnea (OSA) in uncomplicated adult patients, as it provides acceptable accuracy and improves efficiency of care 1. When considering the diagnosis of OSA, the choice between a split-night study and polysomnography depends on various factors, including the patient's symptoms and the pre-test probability of sleep apnea.

• A split-night study is a modified version of a polysomnography (PSG) that combines diagnostic testing and treatment in a single night.
• In a split night study, the first part of the night is used to diagnose sleep apnea, and if criteria are met (typically an apnea-hypopnea index of 15 or greater), the second part is used to titrate continuous positive airway pressure (CPAP) therapy.
• This approach is supported by the American Academy of Sleep Medicine, which suggests that a split-night study has acceptable accuracy to diagnose OSA in an uncomplicated adult patient, as stated in their clinical practice guideline for diagnostic testing for adult obstructive sleep apnea 1.
• The split-night protocol potentially provides enhanced efficiency of care by diagnosing OSA and establishing PAP treatment needs within a single night recording, making it a more efficient and cost-effective option for patients with moderate to severe sleep apnea symptoms.
• However, standard polysomnography remains the gold standard for diagnosing complex or unclear sleep disorders, as it provides more comprehensive data over a full night.
• The quality of evidence supporting the use of split-night studies is low due to imprecision, indirectness, and risk of bias, but the available data suggest that it is a viable option for uncomplicated adult patients with symptoms of OSA 1.

From the Research

Comparison of Split Night Study and Polysomnography

• Split night study and polysomnography (PSG) are two diagnostic tools used in the evaluation of sleep disorders, particularly obstructive sleep apnea (OSA) 2, 3, 4, 5, 6.
• PSG is considered the gold standard for diagnosing OSA, as it provides a comprehensive recording of sleep stages, respiratory parameters, and other physiological variables 2, 6.
• A split night study, on the other hand, involves a single night of PSG, which is divided into two parts: a diagnostic portion and a therapeutic portion 3.
• The diagnostic portion of the split night study is used to diagnose OSA, while the therapeutic portion is used to titrate continuous positive airway pressure (CPAP) therapy 3.
• The American Academy of Sleep Medicine (AASM) recommends the use of PSG for the diagnosis of OSA, but also suggests that a split night study can be used in certain situations, such as when a patient has a high pretest probability of OSA 3.

Advantages and Disadvantages of Split Night Study

• Advantages of split night study:
  • Can be more cost-effective than a full night PSG 6.
  • Can provide a diagnosis and treatment plan in a single night 3.
• Disadvantages of split night study:
  • May not provide as comprehensive a recording of sleep stages and respiratory parameters as a full night PSG 2, 6.
  • May not be suitable for patients with complex sleep disorders or those who require more detailed diagnostic information 4.

First Night Effect in Polysomnography

• The first night effect (FNE) refers to the phenomenon where patients sleep differently on the first night of PSG compared to subsequent nights 5.
• FNE can affect the accuracy of PSG results, particularly in patients with OSA 5.
• A study found that FNE was seen in 48.9% of patients, while 30.5% slept as usual, and 20.6% had a reverse first night effect (RFNE) 5.