4.4 Artifact Recognition, Troubleshooting & ECG Dysrhythmias
Key Takeaways
- Polysomnographic artifacts must be promptly identified by their distinctive morphology: 60 Hz line interference, slow rolling sweat sway, pulse/vascular waves, periodic ECG QRS crosstalk, high-frequency muscle fuzz, and electrode pops.
- The primary resolution for 60 Hz electrical interference is establishing low, balanced electrode impedances (<5 kΩ, difference <2 kΩ) and verifying patient grounding, rather than relying exclusively on the 60 Hz notch filter.
- ECG artifact on EEG derivations is corrected by re-referencing to the contralateral backup electrode or linked mastoids, while sweat artifact is resolved by cooling the room environment and wiping skin with alcohol.
- Continuous single-lead ECG monitoring requires accurate recognition of cardiac dysrhythmias, including sinus bradycardia (<60 bpm / severe <40 bpm), sinus tachycardia (>100 bpm), PACs, PVCs (unifocal, multifocal, bigeminy, couplets), and asystolic pauses (≥3.0 seconds).
- Lethal dysrhythmias—including sustained Ventricular Tachycardia (VT), Ventricular Fibrillation (VF), and prolonged asystole—require immediate in-room patient assessment, activation of the facility emergency response system (Code Blue / EMS), and immediate initiation of CPR/BLS.
Last updated: August 2026
4.4 Artifact Recognition, Troubleshooting & ECG Dysrhythmias
During polysomnographic recording, the technician must maintain pristine signal quality by identifying and resolving non-physiological artifacts that obscure sleep architecture. Simultaneously, the technician must continuously monitor the patient's single-lead electrocardiogram (ECG) to identify life-threatening cardiac dysrhythmias. On the Certified Polysomnographic Technician (CPSGT) examination, troubleshooting skills and cardiac emergency protocols represent high-yield core competencies.
1. Polysomnographic Artifact Recognition & Troubleshooting
Artifacts are unwanted electrical, mechanical, or biological potentials superimposed upon true physiological recordings.
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| COMMON POLYSOMNOGRAPHIC ARTIFACTS |
| |
| [1] 60 Hz Interference ---> Continuous dark sinusoidal 60-cycle band |
| [2] Sweat / Galvanic ---> Slow, undulating baseline sway (0.1-0.5 Hz) |
| [3] ECG Crosstalk ---> Periodic sharp spikes time-locked to QRS |
| [4] Pulse / Vascular ---> Smooth rolling waves delayed ~100-200ms QRS |
| [5] Muscle (EMG) Fuzz ---> High-frequency jagged spikes (>30 Hz) |
| [6] Electrode Pop ---> Abrupt vertical square/triangular jump |
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Detailed Artifact Breakdown & Step-by-Step Resolution:
| Artifact Type | Visual Characteristics | Biophysical Cause | Immediate Corrective Actions |
|---|---|---|---|
| 60 Hz (AC) Line Interference | Continuous, uniform 60 cycles/sec sinusoidal waveform giving a "thick fuzzy" appearance. | Unequal electrode impedances ($>5\text{ k}\Omega$ or $>2\text{ k}\Omega$ mismatch); unshielded power cords crossing lead wires; detached ground (Fpz). | 1. Check impedances.<br/>2. Re-scrub skin and re-paste high-impedance lead.<br/>3. Relocate AC power cables away from headbox.<br/>4. Engage 60 Hz notch filter only if physical troubleshooting fails. |
| Sweat Artifact (Galvanic Sway) | Very slow, large amplitude rolling baseline sway ($0.1\text{--}0.5\text{ Hz}$) mimicking delta waves. | Perspiration creates variable battery-like chemical potential between skin and conductive paste. | 1. Cool patient room ($2\text{--}4^\circ\text{F}$ drop).<br/>2. Remove heavy blankets; turn on fan (directed away from airflow sensor).<br/>3. Clean skin with alcohol and re-apply paste.<br/>4. Temporary LFF increase to 1.0 Hz if authorized by lab protocol. |
| ECG Crosstalk on EEG/EMG | Sharp, periodic QRS-like deflections appearing in-phase across EEG or Chin EMG channels, synchronous with ECG. | Reference electrode (M1/M2) placed over vascular bed picking up far-field cardiac dipole (common in short, thick necks). | 1. Switch active channel to contralateral backup derivation (e.g., C3-M2 instead of C4-M1).<br/>2. Re-reference to linked mastoids $[(\text{M1}+\text{M2})/2]$.<br/>3. Reposition mastoid lead higher on non-vascular mastoid bone. |
| Pulse / Vascular Artifact | Smooth, rhythmic sinusoidal waves repeating with every heartbeat, delayed by $\sim 100\text{--}200\text{ ms}$ after QRS. | Scalp electrode placed directly over a superficial temporal or occipital branch artery. | 1. Palpate scalp around electrode to feel arterial pulse.<br/>2. Reposition electrode $1\text{--}2\text{ cm}$ away from artery while maintaining 10-20 compliance.<br/>3. Re-secure with fresh conductive paste and tape. |
| Muscle Tension (EMG) | High-frequency ($>30\text{ Hz}$), jagged, dense fuzzy deflections obscuring background EEG. | Patient clenching jaw, grimacing, or contracting scalp/cervical muscles. | 1. Reassure patient; instruct them to relax jaw, drop tongue to floor of mouth.<br/>2. Reposition neck pillow for better cervical support.<br/>3. Do not lower EEG HFF below 35 Hz to mask muscle tension. |
| Electrode Pop / Detachment | Sudden, high-voltage vertical square or triangular spikes with amplifier baseline recovery. | Drying conductive paste, air bubble under cup, loose tape, or mechanical pulling on wire. | 1. Identify specific channel and check impedance.<br/>2. Enter room quietly; re-gel, press, and re-tape loose electrode. |
2. Cardiac Dysrhythmia Recognition in Polysomnography
Sleep technologists continuously monitor single-lead ECG (Modified Lead II) to evaluate baseline cardiac rhythm and detect sleep-related arrhythmogenesis.
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| AASM CARDIAC DYSRHYTHMIA DEFINITIONS |
| |
| SINUS BRADYCARDIA: Heart rate < 60 bpm in adults |
| Severe / Critical: Heart rate < 40 bpm |
| SINUS TACHYCARDIA: Heart rate > 100 bpm in adults |
| ASYSTOLE / PAUSE: Cardiac flatline / absence of QRS >= 3.0 seconds |
| PREMATURE ATRIAL (PAC):Early abnormal P wave with narrow normal QRS |
| PREMATURE VENTR. (PVC):Early wide (>120 ms) bizarre QRS without P wave |
| ATRIAL FIBRILLATION: Irregularly irregular R-R intervals; absent P waves|
| VENTRICULAR TACH (VT): Run of >= 3 consecutive wide PVCs at rate > 100 bpm|
| VENTRICULAR FIB (VF): Chaotic, disorganized baseline; no cardiac output |
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Morphological Patterns of Premature Ventricular Contractions (PVCs):
- Unifocal PVCs: All PVCs exhibit identical morphology, indicating origin from a single ectopic ventricular focus.
- Multifocal PVCs: PVCs exhibit differing morphological shapes and polarities, reflecting multiple irritable myocardial foci (higher clinical risk).
- Ventricular Bigeminy: Alternating pattern where every normal sinus beat is paired with one PVC ($1:1$ ratio).
- Ventricular Trigeminy: Repetitive pattern of two normal sinus beats followed by one PVC ($2:1$ ratio).
- Ventricular Couplet: Two consecutive PVCs occurring in rapid succession.
- Non-Sustained Ventricular Tachycardia (NSVT): A run of 3 or more consecutive PVCs lasting $< 30\text{ seconds}$ at a rate $> 100\text{ bpm}$.
- Sustained Ventricular Tachycardia (SVT): VT lasting $\ge 30\text{ seconds}$ or producing immediate hemodynamic instability.
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| PVC PATTERN CLASSIFICATION |
| |
| BIGEMINY: [ Normal ] ──> [ PVC ] ──> [ Normal ] ──> [ PVC ] |
| TRIGEMINY: [ Normal ] ──> [ Normal ] ──> [ PVC ] ──> [ Normal ] |
| COUPLET: [ Normal ] ──> [ PVC ] ──> [ PVC ] ──> [ Normal ] |
| RUN OF VT: [ Normal ] ──> [ PVC ] ──> [ PVC ] ──> [ PVC ] ... |
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3. Emergency Escalation Protocols & Clinical Response
When cardiac dysrhythmias occur, sleep technologists follow a three-tiered escalation framework based on clinical severity and patient stability.
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| POLYSOMNOGRAPHIC CLINICAL ESCALATION TIERS |
| |
| TIER 1: ROUTINE / DOCUMENTATION ONLY |
| - Isolated unifocal PACs or PVCs (< 6/min) |
| - Mild sinus bradycardia (50-59 bpm) during N3 in healthy patient |
| - Transient post-apnea tachycardia (100-110 bpm) |
| --> ACTION: Document in tech log; include epoch timestamps. |
| |
| TIER 2: URGENT / PHYSICIAN NOTIFICATION |
| - New-onset Atrial Fibrillation with rapid ventricular response (>120 bpm)|
| - Frequent multifocal PVCs, bigeminy, or couplets |
| - Sustained sinus bradycardia < 40 bpm or sinus tachycardia > 130 bpm |
| - Asymptomatic sinus pauses between 3.0 and 5.0 seconds |
| --> ACTION: Monitor closely, check patient vitals, notify on-call physician|
| |
| TIER 3: LIFE-THREATENING EMERGENCY (CODE BLUE / 911) |
| - Sustained Ventricular Tachycardia (VT) |
| - Ventricular Fibrillation (VF) |
| - Asystole >= 5.0 to 6.0 seconds or any asystole with unresponsiveness |
| - Acute signs of Myocardial Infarction / Severe chest pain / Shock |
| --> ACTION: Immediate in-room assessment, initiate CPR/BLS, call EMS/Code|
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Step-by-Step Life-Threatening Emergency Algorithm:
- Immediate In-Room Assessment: Enter the room immediately; check responsiveness (tap and shout) and check carotid pulse and breathing simultaneously for no more than 10 seconds.
- Call for Immediate Help & Activate EMS / Code Blue: If unresponsive and pulseless, shout for assistance, activate the facility emergency alarm, and dial 911 / internal hospital code line.
- Initiate High-Quality Basic Life Support (BLS):
- Place patient on firm surface (or insert backboard).
- Begin high-quality chest compressions: rate of $100\text{ to } 120\text{ compressions/minute}$, depth of $2.0\text{ to } 2.4\text{ inches}$ (5–6 cm), allowing complete chest recoil.
- Retrieve and attach the Automated External Defibrillator (AED) immediately; follow voice prompts to shock shockable rhythms (VF or Pulseless VT).
- Deliver ventilations with bag-valve-mask (30 compressions : 2 breaths) if trained.
- Document & Hand Off: Maintain precise chronological log of event start time, CPR initiation, shocks delivered, and hand off directly to arriving paramedics/code team.
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Test Your Knowledge
During an all-night polysomnogram, the technician observes a continuous, thick, uniform 60 cycles/second sinusoidal waveform across derivation C4-M1. What is the most appropriate first-line troubleshooting action?
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Test Your Knowledge
A technician notices sharp, periodic spike waveforms appearing synchronously with every heartbeat across all EEG channels. What is the biophysical cause of this artifact and its standard correction?
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Test Your Knowledge
On the single-lead ECG channel, the technician observes every normal sinus beat followed immediately by a premature, wide (>120 ms), bizarre QRS complex in a repeating 1:1 alternating pattern. Which cardiac dysrhythmia does this pattern represent?
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Test Your Knowledge
Four hours into a polysomnography recording, the ECG channel suddenly displays sustained Ventricular Tachycardia (VT) at a rate of 180 bpm. What is the immediate, mandatory sequence of actions for the sleep technician?
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