NBRC Sleep Disorders Specialist (SDS) Practice Exam

Build your confidence for the NBRC Sleep Disorders Specialist (SDS) Certification Exam with a professionally developed practice test featuring 670 realistic questions and detailed answer explanations. Designed to reflect the style, difficulty, and clinical reasoning expected on the certification exam, this study resource helps you strengthen your knowledge, improve interpretation skills, and prepare for real-world sleep laboratory scenarios.

Whether you are taking the SDS exam for the first time or preparing for recertification, this comprehensive question bank provides focused practice across the topics tested by the National Board for Respiratory Care (NBRC). Every question is written to reinforce practical decision-making rather than simple memorization, helping you approach exam day with greater confidence.

What’s Included

Our NBRC Sleep Disorders Specialist Practice Test includes everything you need for structured and effective exam preparation.

• 670 comprehensive practice questions
• Detailed answer explanations for every question
• Realistic, exam-style multiple-choice format
• Advanced clinical case studies
• Scenario-based learning that mirrors real sleep laboratory situations
• Questions ranging from foundational concepts to advanced interpretation
• Updated content aligned with current sleep medicine practices
• Unlimited self-paced study
• Instant digital access after purchase
• Suitable for independent study or classroom review

This resource is designed to help you identify knowledge gaps early, reinforce difficult concepts, and improve test-taking confidence before the actual examination.

What You Will Learn

The practice questions are designed to strengthen both theoretical knowledge and practical clinical judgment required in an accredited sleep laboratory.

By working through this question bank, you will learn how to:

• Interpret overnight polysomnography (PSG) studies
• Recognize normal and abnormal sleep architecture
• Differentiate obstructive, central, and mixed respiratory events
• Identify respiratory effort-related arousals (RERAs)
• Interpret airflow, respiratory effort, EEG, EOG, EMG, ECG, and pulse oximetry signals
• Understand respiratory physiology during sleep
• Evaluate PAP titration studies
• Interpret CPAP, APAP, and bilevel therapy reports
• Recognize equipment problems and waveform artifacts
• Apply AASM scoring concepts during clinical interpretation
• Analyze patient symptoms and correlate them with PSG findings
• Improve clinical reasoning for complex sleep medicine cases

Topics Covered

This practice test is built around the core knowledge expected of a Sleep Disorders Specialist and includes extensive coverage of important exam domains.

Sleep Physiology

• Sleep stages (N1, N2, N3, REM)
• Sleep architecture
• Sleep efficiency
• Sleep latency
• REM physiology
• Arousal mechanisms
• Circadian rhythm principles

Polysomnography (PSG)

• Sleep staging
• EEG interpretation
• EOG interpretation
• Chin and leg EMG
• ECG monitoring
• Respiratory monitoring
• Pulse oximetry
• Body position monitoring
• Video monitoring
• Artifact recognition

Sleep-Disordered Breathing

• Obstructive Sleep Apnea (OSA)
• Central Sleep Apnea (CSA)
• Mixed Apnea
• Upper Airway Resistance Syndrome (UARS)
• Respiratory Effort-Related Arousals (RERAs)
• Cheyne-Stokes Respiration
• Treatment-Emergent Central Sleep Apnea
• REM-predominant OSA
• Positional OSA

PAP Therapy

• CPAP titration
• APAP therapy
• BiPAP concepts
• Pressure optimization
• Mask fitting
• Leak management
• Humidification
• Heated tubing
• Rainout prevention
• PAP downloads
• Compliance interpretation
• Pressure trends
• Flow limitation analysis
• Residual AHI interpretation

Respiratory Physiology

• Ventilatory control
• Carbon dioxide regulation
• Oxygen desaturation
• Chemoreceptor physiology
• Upper airway anatomy
• Negative intrathoracic pressure
• Respiratory muscle function
• Gas exchange during sleep

Clinical Disorders

• Obesity Hypoventilation Syndrome (OHS)
• COPD Overlap Syndrome
• Neuromuscular disorders
• Heart failure and sleep apnea
• Stroke-related breathing disorders
• Pregnancy and sleep apnea
• Pediatric obstructive sleep apnea
• Endocrine disorders affecting sleep

Parasomnias & Neurologic Disorders

• REM Sleep Behavior Disorder
• Sleepwalking
• Sleep terrors
• Sleep paralysis
• Hypnic jerks
• Narcolepsy
• Cataplexy
• Idiopathic hypersomnia
• Restless Legs Syndrome
• Periodic Limb Movement Disorder

Equipment & Troubleshooting

• Sensor placement
• Belt malfunction
• Airflow signal loss
• Nasal pressure artifact
• Thermistor troubleshooting
• Leak identification
• Mouth leak recognition
• PAP equipment troubleshooting
• Humidifier issues
• Circuit inspection
• Technical artifact recognition

Clinical Decision Making

• Case interpretation
• Patient assessment
• Differential diagnosis
• Treatment recommendations
• PAP follow-up
• Documentation
• Patient education
• Long-term therapy evaluation

Who Can Benefit from This Practice Test?

This study resource is ideal for:

• Respiratory Therapists preparing for the SDS certification
• Registered Polysomnographic Technologists (RPSGT)
• Sleep Technologists
• Sleep Laboratory Staff
• Respiratory Care students
• Healthcare professionals transitioning into sleep medicine
• Experienced clinicians preparing for recertification
• Anyone looking to improve sleep study interpretation skills

Whether you are building foundational knowledge or reviewing advanced concepts, these questions provide valuable exam-focused practice.

Why This Practice Test Works

Passing the SDS examination requires more than memorizing definitions. The exam measures your ability to analyze patient information, interpret physiologic data, and make sound clinical decisions.

That’s why this question bank focuses on:

• Realistic clinical scenarios
• Progressive learning from basic to advanced concepts
• Detailed explanations that reinforce understanding
• Practical waveform interpretation
• High-quality reasoning questions
• Exam-style wording similar to certification testing
• Broad topic coverage without unnecessary repetition
• Confidence-building review before exam day

Each explanation is designed to help you understand why an answer is correct—not simply memorize it.

How We Create Our Practice Questions

Every practice question is developed using recognized sleep medicine principles and reflects the knowledge expected from working professionals in accredited sleep laboratories.

Our development process includes:

• Careful review of current sleep medicine concepts
• Coverage of major exam domains
• Clinically relevant patient scenarios
• Practical waveform interpretation exercises
• Multiple rounds of editing for clarity and accuracy
• Detailed answer explanations for better retention
• Balanced distribution of foundational and advanced topics

The goal is to provide meaningful practice that prepares you for both the certification exam and everyday clinical practice.

Study Tips for the NBRC SDS Exam

Preparing effectively can make a significant difference in your exam performance.

For the best results:

• Create a consistent weekly study schedule.
• Complete practice questions before reviewing explanations.
• Focus extra time on weak subject areas.
• Review PSG waveforms regularly.
• Practice interpreting PAP download reports.
• Strengthen respiratory physiology concepts.
• Review AASM scoring principles.
• Study patient case scenarios rather than isolated facts.
• Take full-length practice exams under timed conditions.
• Revisit missed questions until you understand the reasoning behind every answer.

Consistent practice is one of the most effective ways to improve both speed and accuracy.

How to Register for the NBRC Sleep Disorders Specialist Exam

Candidates typically register for the examination through the National Board for Respiratory Care (NBRC) after confirming they meet all eligibility requirements.

Before registering:

• Review the current eligibility requirements.
• Complete all required education or credential prerequisites.
• Submit your application through the NBRC.
• Schedule your examination at an authorized testing center.
• Review the official candidate handbook before exam day.

Always verify the latest registration policies, examination fees, and testing procedures directly with the NBRC, as requirements may change over time.

NBRC SDS Exam Eligibility

Eligibility requirements vary depending on your professional credentials, education, and clinical experience.

Candidates should review the official NBRC eligibility criteria before applying to ensure they meet the current requirements. Verifying eligibility in advance helps avoid delays during the application process.

Exam Day Strategy

Walking into the testing center with a plan can help reduce anxiety and improve performance.

Keep these strategies in mind:

• Arrive early with the required identification.
• Read every question carefully before selecting an answer.
• Eliminate clearly incorrect options first.
• Pay close attention to clinical details in case-based questions.
• Manage your time throughout the exam.
• Avoid spending too long on a single question.
• Review flagged questions if time remains.
• Stay calm and trust your preparation.

Remember that many SDS questions evaluate clinical reasoning rather than simple recall.

Why Choose This Practice Test?

PrepPool develops high-quality exam preparation resources designed to help healthcare professionals study with confidence. Our practice questions emphasize practical application, realistic clinical situations, and detailed explanations that reinforce long-term understanding rather than short-term memorization.

Whether you’re preparing for your first attempt or reviewing before recertification, this 670-question NBRC Sleep Disorders Specialist Practice Test provides the comprehensive practice needed to strengthen your knowledge, sharpen your interpretation skills, and approach the certification exam with confidence.

NBRC SDS Sample Questions and Answers

Question 1

A 54-year-old man with obesity, hypertension, and loud snoring undergoes overnight polysomnography. The study demonstrates an apnea-hypopnea index (AHI) of 28 events/hour, oxygen saturation nadir of 82%, and respiratory events occurring predominantly in the supine position. Which interpretation is most appropriate?

A. Mild obstructive sleep apnea
B. Moderate obstructive sleep apnea
C. Severe obstructive sleep apnea
D. Upper airway resistance syndrome

Correct Answer: B. Moderate obstructive sleep apnea

Explanation:
An AHI between 15 and 29.9 events per hour is classified as moderate obstructive sleep apnea (OSA). This patient also demonstrates clinically significant oxygen desaturation and positional worsening while sleeping supine, findings commonly associated with OSA. Although oxygen desaturation provides additional information about disease severity, the AHI remains the primary metric for classification in adults. Upper airway resistance syndrome typically does not produce an elevated AHI of this magnitude. Sleep specialists should also evaluate symptoms, cardiovascular comorbidities, sleep architecture disruption, and positional dependency before recommending appropriate treatment, including positional therapy, CPAP, weight reduction, or oral appliance therapy.

Question 2

A sleep technologist observes repeated episodes of absent airflow and absent respiratory effort lasting 18 seconds during polysomnography. Which type of respiratory event is being recorded?

A. Obstructive apnea
B. Mixed apnea
C. Central apnea
D. Hypopnea

Correct Answer: C. Central apnea

Explanation:
Central apnea is characterized by complete cessation of airflow accompanied by the absence of inspiratory respiratory effort. Unlike obstructive apnea, there is no attempt to breathe because respiratory drive from the central nervous system temporarily ceases. Mixed apnea begins as a central event without effort and transitions into an obstructive event with respiratory effort but persistent airflow cessation. Hypopneas involve partial reductions in airflow rather than complete cessation. Proper differentiation between central and obstructive events is essential because treatment approaches differ substantially, particularly when central sleep apnea is associated with heart failure, opioid use, or neurologic disorders.

Question 3

A patient using CPAP reports persistent daytime sleepiness despite nightly usage averaging 7.5 hours. Downloaded data show an AHI of 1.8 events/hour with minimal mask leak. What should be the next step?

A. Increase CPAP pressure immediately
B. Evaluate for other causes of hypersomnolence
C. Discontinue CPAP therapy
D. Repeat titration because therapy has failed

Correct Answer: B. Evaluate for other causes of hypersomnolence

Explanation:
An AHI below 5 events per hour with excellent adherence suggests CPAP is effectively controlling obstructive respiratory events. Persistent excessive daytime sleepiness should prompt evaluation for alternative explanations such as insufficient sleep, medication effects, depression, narcolepsy, circadian rhythm disorders, restless legs syndrome, periodic limb movement disorder, or other medical conditions. Simply increasing CPAP pressure is unlikely to improve symptoms when residual respiratory events are already well controlled. Comprehensive patient assessment, review of sleep habits, and consideration of objective sleepiness testing may identify the true underlying cause and guide appropriate treatment.

Question 4

During CPAP titration, significant unintentional mask leak develops, reducing treatment effectiveness. What is the most appropriate initial intervention?

A. Increase pressure by 5 cm H₂O
B. Refit or replace the mask interface
C. Stop the study immediately
D. Administer supplemental oxygen

Correct Answer: B. Refit or replace the mask interface

Explanation:
Excessive mask leak is one of the most common reasons for ineffective CPAP therapy. The first intervention should be correcting the mask fit by adjusting straps, repositioning the interface, selecting another mask size, or changing mask style. Increasing pressure without addressing the leak often worsens air escape and patient discomfort. Supplemental oxygen does not correct airway obstruction or mask leak. A properly fitted mask improves pressure delivery, patient comfort, treatment adherence, and the accuracy of respiratory event detection throughout the titration study.

Question 5

A patient demonstrates repetitive leg movements every 28 seconds during sleep. Each movement lasts approximately 3 seconds and is associated with EEG arousals. Which disorder is most consistent with these findings?

A. REM sleep behavior disorder
B. Periodic limb movement disorder
C. Sleep terrors
D. Cataplexy

Correct Answer: B. Periodic limb movement disorder

Explanation:
Periodic limb movement disorder (PLMD) consists of repetitive, stereotyped limb movements occurring during sleep at regular intervals, typically every 20 to 40 seconds. These movements frequently produce sleep fragmentation and EEG arousals, contributing to daytime fatigue and nonrestorative sleep. REM sleep behavior disorder involves dream enactment behaviors due to loss of REM atonia, whereas sleep terrors arise during slow-wave sleep. Cataplexy is characterized by sudden muscle weakness during wakefulness triggered by emotions. Proper identification of PLMD helps guide evaluation for contributing conditions such as iron deficiency, renal disease, or medication effects.

Question 6

Which physiologic parameter is primarily measured by thoracic and abdominal respiratory effort belts during polysomnography?

A. Airflow velocity
B. Respiratory effort
C. Oxygen saturation
D. End-tidal carbon dioxide

Correct Answer: B. Respiratory effort

Explanation:
Thoracic and abdominal inductance plethysmography belts measure respiratory effort by detecting expansion and contraction of the chest and abdomen during breathing. These signals help distinguish obstructive apnea, in which respiratory effort persists despite absent airflow, from central apnea, where respiratory effort is absent. Airflow is measured separately using nasal pressure transducers and thermistors. Oxygen saturation is monitored with pulse oximetry, while carbon dioxide monitoring requires dedicated capnography or transcutaneous CO₂ devices. Accurate respiratory effort measurement is fundamental to proper event scoring and diagnosis.

Question 7

A patient with untreated obstructive sleep apnea experiences frequent oxygen desaturation and repetitive arousals throughout the night. Which long-term complication is most strongly associated with untreated disease?

A. Acute appendicitis
B. Hypertension and cardiovascular disease
C. Cataracts
D. Migraine aura

Correct Answer: B. Hypertension and cardiovascular disease

Explanation:
Untreated obstructive sleep apnea contributes significantly to hypertension, coronary artery disease, stroke, atrial fibrillation, heart failure, and other cardiovascular complications. Repeated episodes of intermittent hypoxemia, sympathetic nervous system activation, oxidative stress, inflammation, and sleep fragmentation increase cardiovascular risk over time. Numerous clinical studies have demonstrated these associations, making early diagnosis and effective treatment important for improving long-term health outcomes. While sleep apnea may coexist with many other medical conditions, hypertension and cardiovascular disease remain among its most well-established complications.

Question 8

During a split-night study, when is CPAP titration generally initiated?

A. Immediately after lights out
B. After adequate diagnostic evidence of significant OSA is obtained during the initial portion of the study
C. Only after completing the full overnight study
D. Only after oxygen saturation falls below 70%

Correct Answer: B. After adequate diagnostic evidence of significant OSA is obtained during the initial portion of the study

Explanation:
A split-night study combines diagnostic polysomnography and CPAP titration in one night. The diagnostic portion must first demonstrate sufficient evidence of clinically significant obstructive sleep apnea before transitioning to CPAP titration. This approach allows diagnosis and treatment during a single visit while maintaining adequate diagnostic accuracy. Beginning CPAP immediately would eliminate the diagnostic portion, whereas delaying titration until another night may unnecessarily postpone treatment. Sleep specialists also consider sleep duration, respiratory event frequency, and available time for an effective titration before making the transition.

Question 9

A patient repeatedly removes the CPAP mask because of nasal dryness and congestion. Which intervention is most appropriate?

A. Add heated humidification
B. Reduce sleep duration
C. Increase oxygen flow
D. Change EEG sensitivity

Correct Answer: A. Add heated humidification

Explanation:
Heated humidification is highly effective in reducing nasal dryness, congestion, irritation, and discomfort associated with positive airway pressure therapy. Improved upper airway moisture often enhances patient comfort and long-term treatment adherence. Simply increasing oxygen flow does not address mucosal dryness, while reducing sleep duration would worsen overall health and sleep quality. EEG sensitivity has no relationship to nasal symptoms. Addressing comfort issues early is a critical strategy for improving CPAP compliance and achieving successful long-term management of obstructive sleep apnea.

Question 10

During REM sleep, a patient develops markedly increased obstructive respiratory events despite stable breathing during non-REM sleep. This finding is best described as:

A. REM-predominant obstructive sleep apnea
B. Sleep-related hypoventilation
C. Central hypoventilation syndrome
D. Idiopathic hypersomnia

Correct Answer: A. REM-predominant obstructive sleep apnea

Explanation:
REM-predominant obstructive sleep apnea occurs when respiratory events become substantially more frequent during REM sleep than during non-REM sleep. Muscle atonia during REM increases upper airway collapsibility, making susceptible individuals more vulnerable to obstruction. Patients may experience severe oxygen desaturation despite a relatively modest overall AHI. Recognition of REM predominance is clinically important because these patients often require consistent PAP therapy throughout the entire night to ensure adequate treatment during REM-rich sleep occurring predominantly in the latter half of the sleep period.

Question 11

A patient undergoing diagnostic polysomnography has frequent respiratory effort-related arousals (RERAs), minimal oxygen desaturation, and an AHI of 3 events/hour. Which diagnosis is most consistent with these findings?

A. Mild obstructive sleep apnea
B. Upper airway resistance syndrome (UARS)
C. Central sleep apnea
D. Obesity hypoventilation syndrome

Correct Answer: B. Upper airway resistance syndrome (UARS)

Explanation:
Upper airway resistance syndrome (UARS) is characterized by increased upper airway resistance that causes repeated arousals from sleep without meeting the scoring criteria for apneas or hypopneas. Patients often have an AHI below 5 events per hour but experience excessive daytime sleepiness, fatigue, and nonrestorative sleep due to frequent respiratory effort-related arousals (RERAs). Unlike obstructive sleep apnea, significant oxygen desaturation is usually absent. Accurate identification of UARS requires careful recognition of airflow limitation and EEG arousals during polysomnography. Treatment options include CPAP therapy, oral appliances, positional therapy, and management of contributing upper airway abnormalities.

Question 12

During polysomnography, which sensor provides the most sensitive measurement for detecting airflow limitation associated with hypopneas?

A. Thermistor alone
B. Nasal pressure transducer
C. ECG leads
D. Pulse oximeter

Correct Answer: B. Nasal pressure transducer

Explanation:
The nasal pressure transducer is the preferred sensor for detecting subtle reductions in airflow associated with hypopneas because it accurately reflects inspiratory airflow changes. Thermistors are excellent for identifying complete cessation of airflow during apneas but are less sensitive for partial airflow reductions. Pulse oximetry identifies oxygen desaturation after respiratory events occur rather than measuring airflow directly. ECG leads monitor cardiac rhythm only. Understanding the strengths of each monitoring device helps sleep specialists accurately score respiratory events according to current scoring standards and minimizes false-negative interpretations.

Question 13

A patient with severe obstructive sleep apnea is prescribed bilevel positive airway pressure (BPAP). What is the primary advantage of BPAP compared with fixed CPAP?

A. It automatically treats insomnia
B. It delivers different inspiratory and expiratory pressures to improve comfort and ventilation
C. It eliminates all central apneas
D. It requires no mask interface

Correct Answer: B. It delivers different inspiratory and expiratory pressures to improve comfort and ventilation

Explanation:
BPAP delivers a higher inspiratory positive airway pressure (IPAP) and a lower expiratory positive airway pressure (EPAP). This pressure difference reduces the work of breathing, improves ventilation, and enhances comfort, especially for patients requiring higher therapeutic pressures or those with hypoventilation disorders. Unlike CPAP, which provides a constant pressure throughout the respiratory cycle, BPAP assists inspiration while maintaining airway patency during expiration. BPAP does not automatically eliminate central sleep apnea or treat insomnia, and it still requires an appropriately fitted patient interface for effective therapy.

Question 14

During a titration study, the sleep technologist observes persistent obstructive hypopneas despite elimination of apneas. According to accepted titration principles, what is the most appropriate action?

A. Maintain the current pressure for the remainder of the study
B. Increase positive airway pressure incrementally until obstructive events are controlled
C. Immediately switch to adaptive servo-ventilation
D. Discontinue positive airway pressure therapy

Correct Answer: B. Increase positive airway pressure incrementally until obstructive events are controlled

Explanation:
The goal of PAP titration is to eliminate obstructive apneas, hypopneas, respiratory effort-related arousals, and snoring across all sleep stages and body positions whenever possible. If obstructive hypopneas persist after apneas have resolved, pressure should be increased gradually while monitoring patient tolerance and sleep quality. Prematurely ending titration or switching to another therapy without indication may leave residual obstructive events untreated. Careful incremental adjustments improve treatment effectiveness while minimizing pressure-related discomfort and maintaining adequate sleep continuity throughout the remainder of the study.

Question 15

A patient develops recurrent episodes of complex motor behaviors during REM sleep, including punching and shouting while vividly recalling dream content after awakening. Which diagnosis is most likely?

A. Sleepwalking
B. REM sleep behavior disorder
C. Nocturnal seizures
D. Confusional arousals

Correct Answer: B. REM sleep behavior disorder

Explanation:
REM sleep behavior disorder (RBD) results from loss of normal skeletal muscle atonia during REM sleep, allowing patients to physically act out vivid dreams. Behaviors may include punching, kicking, shouting, or jumping from bed, sometimes resulting in injury to the patient or bed partner. Video polysomnography typically demonstrates REM sleep without atonia. RBD is clinically important because it may precede neurodegenerative disorders such as Parkinson disease, dementia with Lewy bodies, and multiple system atrophy by several years. Accurate diagnosis enables appropriate safety counseling, treatment, and long-term neurological follow-up.

Question 16

Which finding is most characteristic of obstructive apnea during polysomnography?

A. Absent airflow with continued respiratory effort
B. Absent airflow without respiratory effort
C. Normal airflow with oxygen desaturation only
D. Increased respiratory rate throughout the event

Correct Answer: A. Absent airflow with continued respiratory effort

Explanation:
Obstructive apnea occurs when airflow completely ceases despite ongoing inspiratory effort as the patient attempts to breathe against an occluded upper airway. Thoracic and abdominal effort belts continue to show respiratory movement while airflow sensors detect no airflow. This distinguishes obstructive apnea from central apnea, in which both airflow and respiratory effort disappear simultaneously. Recognizing this physiologic difference is fundamental for accurate event classification because treatment strategies differ depending on the underlying mechanism responsible for sleep-disordered breathing.

Question 17

A patient with obesity hypoventilation syndrome undergoes overnight monitoring. Which additional measurement is particularly valuable for evaluating nocturnal hypoventilation?

A. End-tidal or transcutaneous carbon dioxide monitoring
B. Chin EMG alone
C. Electrooculography only
D. Body position sensor

Correct Answer: A. End-tidal or transcutaneous carbon dioxide monitoring

Explanation:
Carbon dioxide monitoring provides direct assessment of ventilation and is particularly valuable in patients suspected of sleep-related hypoventilation, including obesity hypoventilation syndrome, neuromuscular disorders, and certain pulmonary diseases. Persistent elevation of CO₂ during sleep supports inadequate alveolar ventilation even when oxygen saturation appears relatively preserved. While body position, EMG, and EOG contribute important information during polysomnography, they cannot evaluate ventilation directly. Continuous CO₂ monitoring improves diagnostic accuracy and assists clinicians in selecting the most appropriate ventilatory support therapy.

Question 18

A patient demonstrates significant worsening of obstructive respiratory events only while sleeping supine. Which initial non-PAP intervention may be appropriate if clinically indicated?

A. Positional therapy
B. Sleep restriction therapy
C. Bright light therapy
D. Melatonin administration

Correct Answer: A. Positional therapy

Explanation:
Positional obstructive sleep apnea occurs when respiratory events increase substantially while the patient sleeps on the back. In appropriately selected patients, positional therapy may reduce airway collapse by encouraging lateral sleeping positions through behavioral strategies or specialized positioning devices. Although PAP therapy remains the most effective treatment for many patients, positional therapy may benefit individuals whose disease is predominantly supine-dependent. Proper patient selection requires careful review of polysomnographic data, symptom severity, overall AHI, and the presence of comorbid medical conditions before recommending this intervention.

Question 19

A sleep technologist notices persistent artifact affecting the airflow tracing during polysomnography. Which action should be taken first?

A. Ignore the artifact because oxygen saturation is normal
B. Inspect and correct the sensor placement and connections
C. End the recording immediately
D. Score respiratory events without the airflow signal

Correct Answer: B. Inspect and correct the sensor placement and connections

Explanation:
High-quality physiologic signals are essential for accurate sleep study interpretation. When airflow artifact occurs, the technologist should first verify sensor position, tubing integrity, cable connections, and patient movement before considering equipment malfunction. Correcting the problem promptly minimizes data loss and reduces the likelihood of inaccurate respiratory event scoring. Ignoring poor-quality signals or attempting to score events without reliable airflow measurements increases the risk of diagnostic errors. Continuous quality assurance throughout the study is a critical responsibility of the sleep technologist.

Question 20

A patient reports irresistible daytime sleep attacks, hypnagogic hallucinations, sleep paralysis, and episodes of sudden muscle weakness triggered by laughter. Which diagnosis is most likely?

A. Chronic insomnia disorder
B. Narcolepsy type 1
C. Circadian rhythm sleep-wake disorder
D. Periodic limb movement disorder

Correct Answer: B. Narcolepsy type 1

Explanation:
Narcolepsy type 1 is characterized by excessive daytime sleepiness accompanied by cataplexy, which consists of sudden transient muscle weakness triggered by strong emotions such as laughter or excitement. Additional features commonly include hypnagogic hallucinations, sleep paralysis, and disrupted nighttime sleep. Diagnostic evaluation typically includes overnight polysomnography followed by a Multiple Sleep Latency Test (MSLT), demonstrating short sleep latency and multiple sleep-onset REM periods. Recognition of these classic symptoms is essential because timely diagnosis allows treatment with wake-promoting medications, scheduled naps, safety counseling, and long-term symptom management.

Question 21 

A 51-year-old man undergoes an attended CPAP titration. During N2 sleep in the lateral position at 8 cm H₂O, all obstructive events resolve. Later, after entering REM sleep while supine, he develops two obstructive apneas, four obstructive hypopneas associated with 4% oxygen desaturations, persistent inspiratory flow limitation, and loud snoring. Mask leak remains minimal. What is the BEST next action?

A. Increase CPAP pressure according to titration protocol while continuing to monitor for treatment-emergent central apneas.
B. Leave the pressure unchanged because N2 sleep was adequately treated.
C. Switch immediately to bilevel PAP because REM events occurred.
D. End the titration because REM sleep is not required for determining therapeutic pressure.

Correct Answer: A. Increase CPAP pressure according to titration protocol while continuing to monitor for treatment-emergent central apneas.

Detailed Explanation:

A high-quality PAP titration must demonstrate adequate control of obstructive respiratory events during the patient’s most vulnerable conditions—typically REM sleep and the supine position. Although 8 cm H₂O adequately controlled breathing during lateral N2 sleep, the recurrence of obstructive apneas, hypopneas, snoring, and inspiratory flow limitation during REM-supine sleep indicates that the pressure is insufficient under more challenging physiologic conditions.

The technologist should increase pressure incrementally according to AASM titration guidelines while continuously monitoring airflow, respiratory effort, oxygen saturation, EEG arousals, patient comfort, and the possible appearance of treatment-emergent central apneas. Switching immediately to bilevel PAP is not appropriate because obstructive events have not yet proven resistant to optimal CPAP titration. Ending the study prematurely would risk prescribing an inadequate therapeutic pressure.

Question 22

While reviewing a polysomnogram, you observe the following during a respiratory event:

• Nasal pressure amplitude gradually decreases.
• Inspiratory waveform becomes flattened.
• Thoracic and abdominal effort progressively increase.
• Snoring is present.
• Oxygen saturation falls by 4%.
• EEG demonstrates a cortical arousal at event termination.

Which physiologic process is MOST likely occurring?

A. Progressive upper airway narrowing resulting in an obstructive hypopnea
B. Central apnea caused by absent respiratory drive
C. Normal transition into slow-wave sleep
D. Cardiac artifact affecting the airflow signal

Correct Answer: A. Progressive upper airway narrowing resulting in an obstructive hypopnea.

Detailed Explanation:

This waveform pattern is classic for progressive upper airway obstruction. Inspiratory flow limitation produces flattening of the nasal pressure waveform, indicating increasing upper airway resistance. Continued respiratory effort demonstrates that the patient is attempting to breathe despite the partial obstruction. Snoring reflects turbulent airflow through the narrowed airway. Oxygen desaturation and an EEG arousal complete the physiologic sequence required for scoring an obstructive hypopnea.

A central apnea would demonstrate absent respiratory effort, making Option B incorrect. Accurate waveform interpretation is a critical competency for the SDS examination because subtle airflow abnormalities often precede more severe respiratory events.

Question 23

A patient reports that during the first hour of PAP therapy, breathing feels comfortable. Later in the night, the machine becomes noticeably louder, the patient awakens with dry eyes, and the download demonstrates intermittent periods of large leak occurring almost exclusively after midnight. Residual AHI remains low.

What is the MOST likely explanation?

A. Mask displacement during sleep resulting in intermittent large leak
B. Progressive worsening of obstructive sleep apnea throughout the night
C. Failure of the PAP blower motor
D. Inaccurate pulse oximetry recording

Correct Answer: A. Mask displacement during sleep resulting in intermittent large leak.

Detailed Explanation:

Large leaks that develop later in the night are commonly caused by positional changes, gradual loosening of the mask, facial relaxation during sleep, worn cushions, or pressure changes associated with REM sleep. Dry eyes strongly suggest that airflow is escaping toward the eyes, supporting the diagnosis of mask leak.

Because residual AHI remains low, therapeutic pressure appears sufficient despite intermittent leakage. The first intervention should focus on evaluating mask fit, headgear tension, sleeping position, cushion integrity, and tubing connections before altering pressure settings. Equipment troubleshooting questions frequently appear on the SDS examination because proper mask management directly influences long-term PAP adherence.

Question 24

A patient with obesity, resistant hypertension, type 2 diabetes, atrial fibrillation, excessive daytime sleepiness, loud snoring, and witnessed apneas undergoes diagnostic polysomnography confirming severe obstructive sleep apnea.

Which of these comorbid conditions has the STRONGEST evidence-based association with untreated OSA?

A. Resistant hypertension
B. Seasonal allergic rhinitis
C. Migraine headaches
D. Gastroenteritis

Correct Answer: A. Resistant hypertension.

Detailed Explanation:

Although OSA has been associated with multiple medical disorders, resistant hypertension has one of the strongest and most consistently demonstrated relationships. Repeated nocturnal hypoxemia, sympathetic nervous system activation, oxidative stress, endothelial dysfunction, and activation of the renin-angiotensin-aldosterone system contribute to persistently elevated blood pressure despite antihypertensive therapy.

The SDS examination frequently tests the relationship between sleep-disordered breathing and cardiovascular disease. Candidates should recognize that resistant hypertension, atrial fibrillation, coronary artery disease, heart failure, stroke, pulmonary hypertension, insulin resistance, and type 2 diabetes all have clinically important associations with untreated OSA.

Question 25

A 67-year-old man undergoing CPAP titration reaches 12 cm H₂O. Obstructive apneas, hypopneas, snoring, respiratory effort-related arousals (RERAs), and flow limitation completely resolve. Oxygen saturation remains above 92%, and mask leak is acceptable. However, shortly afterward, repetitive central apneas begin appearing without evidence of upper airway obstruction.

What is the BEST interpretation?

A. Treatment-emergent central sleep apnea has likely developed after elimination of obstructive events.
B. Obstructive sleep apnea is worsening despite higher pressure.
C. The airflow sensor has become disconnected.
D. The patient has entered REM sleep.

Correct Answer: A. Treatment-emergent central sleep apnea has likely developed after elimination of obstructive events.

Detailed Explanation:

This scenario describes treatment-emergent central sleep apnea (TECSA), one of the highest-yield concepts on the NBRC SDS examination. TECSA occurs when obstructive respiratory events resolve with PAP therapy, but central apneas emerge or become more apparent. The proposed mechanism involves increased ventilation reducing arterial carbon dioxide below the patient’s apneic threshold, temporarily suppressing respiratory drive.

Recognition requires careful waveform analysis. Central apneas demonstrate absent airflow and absent respiratory effort, distinguishing them from obstructive events. Appropriate management depends on their frequency, persistence, associated symptoms, and physician-directed protocols. The technologist should document these events carefully, avoid unnecessary pressure escalation, and ensure that oxygen saturation, sleep stage, and patient comfort are fully assessed before concluding the titration.