Sleep Diagnostics — MCQs
A 40-year-old man presents with daytime sleepiness and impaired concentration and memory. On examination his BMI is 41 kg/m2, BP is 160/100 mm Hg. His awake ABG analysis is given: PaO2=66 mm Hg, PaCO2=50 mm Hg, HCO3=28 mEq/L. What is the most likely diagnosis?
Severe Obstructive sleep apnea is defined as AHI of greater than
A patient at the orthopedics OPD complains of troubled sleep at night due to numbness and tingling sensation involving his lateral 3 digits. His symptoms are relieved as he lays his arms hanging from the bed. Which of the following options correctly describes his condition and the test used to assess it?
Berger waves (alpha waves) of EEG have a rhythm of how many Hz?
What does a pulse oximeter primarily measure?
Which of the following is not a diagnostic criterion for SIRS?
Which of the following statements about obstructive sleep apnea is false?
The sleep apnea syndrome is defined as -
In narcolepsy, the polysomnographic recording typically shows which of the following patterns?
What is the minimum number of apnea episodes required for the diagnosis of obstructive sleep apnea?
Sleep Diagnostics Indian Medical PG Practice Questions and MCQs
Question 1: A 40-year-old man presents with daytime sleepiness and impaired concentration and memory. On examination his BMI is 41 kg/m2, BP is 160/100 mm Hg. His awake ABG analysis is given: PaO2=66 mm Hg, PaCO2=50 mm Hg, HCO3=28 mEq/L. What is the most likely diagnosis?
- A. Obstructive sleep apnea (Correct Answer)
- B. Narcolepsy
- C. Obesity hypoventilation syndrome
- D. Central sleep apnea
Explanation: ***Obstructive Sleep Apnea (Correct Answer)*** - Classic triad: **morbid obesity (BMI 41 kg/m²)**, **excessive daytime somnolence**, and **systemic hypertension (160/100 mmHg)** — hallmarks of OSA - **ABG findings** (PaO2=66 mmHg, PaCO2=50 mmHg, HCO3=28 mEq/L) indicate **chronic nocturnal hypoxemia and hypercapnia** with compensatory **metabolic alkalosis** from repeated apneic episodes - **Cognitive impairment** (impaired concentration and memory) results from **sleep fragmentation** and intermittent nocturnal hypoxia - Obesity promotes **pharyngeal fat deposition** → upper airway narrowing and collapse during sleep → recurrent obstructive events *Narcolepsy* - Causes excessive daytime sleepiness but is **not associated with obesity, hypertension, or ABG abnormalities** - Hallmarks include **cataplexy**, sleep paralysis, and hypnagogic/hypnopompic hallucinations — none present here - Caused by **orexin (hypocretin) deficiency**; associated with **HLA-DQB1*06:02**; ABG is normal *Obesity Hypoventilation Syndrome (OHS / Pickwickian Syndrome)* - Defined as **awake PaCO2 >45 mmHg + BMI >30 kg/m²** with exclusion of other causes of hypoventilation - OHS frequently coexists as an **overlap with and consequence of severe OSA** rather than being the primary diagnosis - In this setting, **OSA is the most prevalent and primary diagnosis**; OHS is specifically considered when awake hypoventilation persists despite adequate OSA treatment *Central Sleep Apnea* - Results from **failure of central respiratory drive** (brainstem), not upper airway obstruction - Associated with **congestive heart failure, opioid use, high-altitude exposure, or neurological disease** — none present here - Not characteristically associated with morbid obesity; clinical and ABG picture here favors an **obstructive** rather than central pattern
Question 2: Severe Obstructive sleep apnea is defined as AHI of greater than
- A. 15 events/hour
- B. 30 events/hour (Correct Answer)
- C. 25 events/hour
- D. 20 events/hour
Explanation: ***30 events/hour*** - A **severe form of obstructive sleep apnea (OSA)** is diagnosed when the Apnea-Hypopnea Index (AHI) is greater than or equal to **30 events per hour** [1]. - The AHI represents the average number of **apnea and hypopnea events** per hour of sleep [1]. *15 events/hour* - An AHI of **15 to 30 events/hour** typically defines **moderate sleep apnea**, not severe. - This level indicates a significant number of sleep disturbances, but less than what is categorized as severe. *25 events/hour* - An AHI of **25 events/hour** falls within the **moderate range** of OSA severity (15-30 events/hour). - It does not meet the criteria for severe OSA, which requires a higher AHI. *20 events/hour* - An AHI of **20 events/hour** also falls into the **moderate category** of OSA. - This value is above the threshold for mild OSA (5-15 events/hour) but below the threshold for severe OSA.
Question 3: A patient at the orthopedics OPD complains of troubled sleep at night due to numbness and tingling sensation involving his lateral 3 digits. His symptoms are relieved as he lays his arms hanging from the bed. Which of the following options correctly describes his condition and the test used to assess it?
- A. Guyon's canal syndrome, Froment's test
- B. Carpal tunnel syndrome, Froment's test
- C. Guyon's canal syndrome, Durkan's test
- D. Carpal tunnel syndrome, Durkan's test (Correct Answer)
Explanation: ***Carpal tunnel syndrome, Durkan's test*** - The symptoms of **numbness and tingling** in the **lateral 3 digits** (thumb, index, middle, and radial half of the ring finger) are classic for **carpal tunnel syndrome (CTS)**, caused by compression of the **median nerve**. Relief with hanging the arm is due to gravity reducing swelling and pressure. - **Durkan's test** (or **median nerve compression test**) is highly specific for CTS. It involves direct pressure over the carpal tunnel, reproducing symptoms within 30 seconds. *Guyon's canal syndrome, Froment's test* - **Guyon's canal syndrome** involves compression of the **ulnar nerve** at the wrist, primarily affecting the **little finger** and the **ulnar half of the ring finger**, not the lateral 3 digits. - **Froment's test** assesses **ulnar nerve palsy** by observing the strength of adductor pollicis during a pinch grip, which is unrelated to median nerve compression. *Carpal tunnel syndrome, Froment's test* - While **carpal tunnel syndrome** is correctly identified based on the symptoms, **Froment's test** is not used to assess it. - As mentioned, Froment's test evaluates **ulnar nerve function**, particularly the adductor pollicis muscle. *Guyon's canal syndrome, Durkan's test* - The symptoms described (lateral 3 digits) are inconsistent with **Guyon's canal syndrome**, which affects the ulnar nerve distribution. - Although **Durkan's test** is appropriate for carpal tunnel syndrome, the diagnosis for Guyon's canal syndrome is incorrect.
Question 4: Berger waves (alpha waves) of EEG have a rhythm of how many Hz?
- A. 0-4 Hz
- B. 4-7 Hz
- C. 8-13 Hz (Correct Answer)
- D. 13-30 Hz
Explanation: ***8-13 Hz*** - **Berger waves**, also known as **alpha waves**, are defined by their frequency range of **8 to 13 Hz** in the electroencephalogram (EEG). - These waves are typically observed when a person is in a relaxed, awake state with their eyes closed. *0-4 Hz* - This frequency range corresponds to **delta waves**, which are characteristic of deep sleep and certain brain pathologies. - Delta waves are much slower and have higher amplitude compared to alpha waves. *4-7 Hz* - This frequency range is associated with **theta waves**, commonly seen during light sleep, drowsiness, and some meditative states. - Theta waves are slower than alpha waves and indicate a state of reduced alertness. *13-30 Hz* - This frequency range represents **beta waves**, which are associated with active thinking, problem-solving, and alertness with open eyes. - Beta waves are faster and typically have lower amplitude than alpha waves.
Question 5: What does a pulse oximeter primarily measure?
- A. Oxygen content of blood
- B. Oxygen saturation (Correct Answer)
- C. Partial pressure of oxygen
- D. Carbon dioxide levels
Explanation: ***Oxygen saturation*** - A pulse oximeter primarily measures the **percentage of hemoglobin** in arterial blood that is saturated with oxygen. - This is often reported as **SpO2** (peripheral oxygen saturation), an estimate of SaO2 (arterial oxygen saturation). *Oxygen content of blood* - The **total amount of oxygen** in the blood includes dissolved oxygen and oxygen bound to hemoglobin. - Pulse oximeters only measure the proportion of hemoglobin bound to oxygen, not the absolute amount of oxygen. *Partial pressure of oxygen* - This refers to the **amount of oxygen dissolved in the plasma** and is denoted as PaO2. - Measurement of PaO2 requires an **arterial blood gas (ABG)** analysis, which is an invasive procedure. *Carbon dioxide levels* - Pulse oximeters do **not measure CO2**; they use light absorption at specific wavelengths to differentiate oxyhemoglobin from deoxyhemoglobin. - Measurement of carbon dioxide requires **capnography** or arterial blood gas analysis.
Question 6: Which of the following is not a diagnostic criterion for SIRS?
- A. Hypotension (Correct Answer)
- B. Tachypnoea
- C. Leucocytosis
- D. Tachycardia
Explanation: ### Hypotension - **Hypotension** is a criterion for **sepsis** and **septic shock**, but not for **SIRS** itself. - **SIRS** criteria are based on inflammatory responses, while hypotension indicates a more severe systemic compromise. *Tachycardia* - **Tachycardia**, defined as a **heart rate >90 beats per minute**, is a diagnostic criterion for **SIRS** [1]. - It reflects the body's physiological stress response to a systemic inflammatory state [1]. *Tachypnoea* - **Tachypnoea**, indicated by a **respiratory rate >20 breaths per minute** or a **PaCO2 <32 mmHg**, is a diagnostic criterion for **SIRS** [1]. - This symptom shows the body's effort to compensate for metabolic acidosis or increased oxygen demand. *Leucocytosis* - **Leucocytosis**, defined as a **white blood cell count >12,000/mm³** or **<4,000/mm³**, or the presence of **>10% immature neutrophils (bands)**, is a diagnostic criterion for **SIRS** [1]. - This indicates a significant systemic inflammatory response in the blood [1].
Question 7: Which of the following statements about obstructive sleep apnea is false?
- A. Apnea is associated with high respiratory effort
- B. Apnea is associated with fall in SpO2
- C. Apnea is associated with sudden awakening
- D. Contraction of pharyngeal muscles can worsen obstruction (Correct Answer)
Explanation: ***Contraction of pharyngeal muscles can worsen obstruction*** - In **obstructive sleep apnea (OSA)**, the pharyngeal muscles are normally responsible for maintaining airway patency [1]. - A *contraction* of these muscles would *open* the airway, whereas *relaxation* or *loss of tone* leads to collapse and obstruction. *Apnea is associated with high respiratory effort* - During an **apneic episode** in OSA, the airway is *obstructed*, leading to continued but **unsuccessful inspiratory efforts** against a closed airway. - This results in a significant increase in **respiratory effort** as the diaphragm and accessory muscles try to overcome the obstruction. *Apnea is associated with fall in SpO2* - The cessation of airflow during **apnea** prevents **gas exchange**, leading to a progressive decrease in **oxygen saturation (SpO2)**. - This **hypoxia** is a hallmark physiological consequence of apneic events and often triggers arousal from sleep [2]. *Apnea is associated with sudden awakening* - The combination of **hypoxia** and **hypercapnia** (increased CO2), along with the increased respiratory effort, stimulates the central nervous system [2]. - This stimulation causes a **brief arousal or awakening** from sleep, often accompanied by gasping or snorting, to re-establish airway patency.
Question 8: The sleep apnea syndrome is defined as -
- A. Apnea-Hypopnea Index (AHI) ≥ 5/hour (Correct Answer)
- B. Apnea-Hypopnea Index (AHI) ≥ 10/hour
- C. Apnea-Hypopnea Index (AHI) ≥ 30/hour
- D. Apnea-Hypopnea Index (AHI) ≥ 15/hour
Explanation: ***Apnea-Hypopnea Index (AHI) ≥ 5/hour*** - The definition of **sleep apnea syndrome** generally requires an **AHI of 5 or more events per hour**, often accompanied by symptoms like excessive daytime sleepiness or cardiovascular complications [1]. - This threshold identifies individuals with clinically significant sleep-disordered breathing that warrants further evaluation and potential treatment [1]. *Apnea-Hypopnea Index (AHI) ≥ 10/hour* - While an AHI of 10/hour indicates sleep apnea, it is a higher severity criterion and does not represent the **minimum threshold** for defining the syndrome [1]. - Patients with an AHI between 5 and 10 also have sleep apnea and can experience significant symptoms. *Apnea-Hypopnea Index (AHI) ≥ 30/hour* - An AHI of 30/hour or more signifies **severe sleep apnea**, which requires aggressive management. - This is far above the **general diagnostic threshold** for sleep apnea syndrome. *Apnea-Hypopnea Index (AHI) ≥ 15/hour* - An AHI of 15/hour is typically classified as **moderate sleep apnea**. - This value is higher than the **lowest AHI threshold** used to define the presence of sleep apnea syndrome.
Question 9: In narcolepsy, the polysomnographic recording typically shows which of the following patterns?
- A. REM intrusion during inappropriate periods (Correct Answer)
- B. An absence of REM sleep in midcycle
- C. Extreme muscular relaxation
- D. Spike-and-wave EEG recording
Explanation: ***REM intrusion during inappropriate periods*** - In narcolepsy, the hallmark polysomnographic finding is **sleep-onset REM periods (SOREMPs)** - the occurrence of REM sleep within 15 minutes of sleep onset. - The **Multiple Sleep Latency Test (MSLT)** in narcolepsy typically shows **≥2 SOREMPs** along with a mean sleep latency of ≤8 minutes. - Clinically, this **REM sleep intrusion** manifests as **sudden, irresistible sleep attacks** during the day, **cataplexy** (sudden muscle weakness triggered by strong emotions), **sleep paralysis**, and **hypnagogic/hypnopompic hallucinations**. - These represent features of REM sleep (muscle atonia, dreams) occurring at inappropriate times. *An absence of REM sleep in midcycle* - This statement is incorrect as narcolepsy is characterized by an **abnormal presence and early onset of REM sleep**, not its absence. - Individuals with narcolepsy enter REM sleep much faster than normal (often within minutes rather than the typical 90 minutes). *Extreme muscular relaxation* - While **cataplexy** (present in Type 1 narcolepsy) involves sudden loss of muscle tone due to REM-related atonia during wakefulness, this is a clinical symptom rather than a continuous polysomnographic finding. - Polysomnography focuses on **sleep architecture** and the timing of **REM sleep onset**, not general muscle relaxation patterns. *Spike-and-wave EEG recording* - **Spike-and-wave patterns** on EEG are characteristic of **absence seizures** (a form of epilepsy), not narcolepsy. - Narcolepsy is a primary **sleep disorder** with distinct polysomnographic features related to **REM sleep dysregulation**, not epileptiform activity.
Question 10: What is the minimum number of apnea episodes required for the diagnosis of obstructive sleep apnea?
- A. AHI ≥ 10 events/hour
- B. AHI ≥ 2 events/hour
- C. AHI ≥ 5 events/hour (Correct Answer)
- D. AHI ≥ 4 events/hour
Explanation: ***AHI ≥ 5 events/hour*** - An **apnea-hypopnea index (AHI)** of 5 or more events per hour of sleep, accompanied by symptoms such as **daytime sleepiness**, snoring, or witnessed apneas, is the diagnostic criterion for obstructive sleep apnea (OSA) [1]. - This threshold signifies a clinically significant frequency of **breathing disturbances** during sleep [1]. *AHI ≥ 2 events/hour* - An AHI of 2 events/hour is generally considered within the **normal range** or indicates very mild, non-pathological sleep disordered breathing. - It is **insufficient** to diagnose OSA in adults, even with associated symptoms. *AHI ≥ 10 events/hour* - An AHI of 10 events/hour would indicate at least **mild to moderate OSA**, well above the minimum diagnostic threshold. - While diagnostic, it is not the *minimum* number required for initial diagnosis. *AHI ≥ 4 events/hour* - An AHI of 4 events/hour is close to the diagnostic threshold but still **below the minimum** required for a formal diagnosis of OSA. - It would typically be considered **mild sleep-disordered breathing** that may not meet diagnostic criteria without other significant factors.
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