What should be done if a pulse oximeter's heart rate reading is significantly inaccurate?

Managing Inaccurate Pulse Oximeter Heart Rate Readings

When a pulse oximeter's heart rate reading is significantly inaccurate, alternative methods of heart rate measurement should be used, with ECG being the most reliable option for accurate heart rate determination.

Understanding Pulse Oximeter Limitations

Pulse oximeters detect pulsatile blood flow by identifying changes in light absorption that occur with each heartbeat. However, they have several limitations when measuring heart rate:

• Studies show that oximeter readings significantly underestimate heart rates above 155 beats/min during exercise 1
• Recent evidence demonstrates that heart rates of acutely ill patients are not reliably measured by pulse oximeters, with limits of agreement ranging from -22.6 to 19.9 beats per minute compared to ECG 2
• Pulse oximeters failed to identify more than half of ECG recordings that would have awarded 3 NEWS points for heart rate in acutely ill patients 2

Factors Affecting Pulse Oximeter Heart Rate Accuracy

Several factors can contribute to inaccurate heart rate readings:

• Poor peripheral perfusion and low blood pressure (readings become unreliable when systolic BP < 80 mmHg) 3
• Motion artifacts and patient movement 4
• Sweating during exercise 1
• Interference from other electronic devices (nerve stimulators, evoked-potential stimulators) 5
• Low flow states 6
• Dark skin pigmentation 7, 4
• Nail polish or artificial nails 4

Recommended Actions When Heart Rate Readings Are Inaccurate

1. Verify with alternative methods:

   • ECG provides the most rapid and accurate estimation of heart rate 7
   • Manual pulse palpation can be used as an immediate alternative

2. Check for technical issues:

   • Ensure proper probe placement and contact
   • Check that the probe is detecting an adequate signal
   • Verify the displayed pulse waveform is clear and consistent
   • For ear probes, remove jewelry and gently rub the lobe to improve local perfusion 7
   • For finger probes, ensure the patient isn't tightly gripping support bars 7

3. Consider patient factors:

   • Assess for poor peripheral perfusion
   • Check blood pressure (readings are unreliable with systolic BP < 80 mmHg) 3
   • Evaluate for conditions that might affect readings (hypothermia, vasoconstriction)

4. Document the discrepancy:

   • Record both the pulse oximeter reading and the alternative measurement
   • Note the potential cause of inaccuracy

Clinical Implications

Inaccurate heart rate readings from pulse oximetry can lead to inappropriate clinical decisions:

• False bradycardia readings may prompt unnecessary interventions 7
• Missed tachycardia may delay recognition of deterioration
• During procedural sedation, accurate heart rate monitoring is essential for patient safety 7

Special Considerations

• During resuscitation: ECG should be prioritized for heart rate determination in neonatal resuscitation 7
• During procedural sedation: Vital sign monitoring should include assessment of blood pressure, pulse rate, respiratory rate, and pulse oximetry 7
• During exercise testing: Pulse oximeter heart rate readings become increasingly unreliable at higher exercise intensities 1

Remember that pulse oximetry remains valuable for oxygen saturation monitoring even when heart rate readings are inaccurate. The physical assessment of the patient should never be superseded or replaced by pulse oximeter readings 7.