What could be causing my rib and shoulder pain, decreased heart rate variability (HRV), and fluctuations in oxygen saturation (SpO2) levels after changing sleep positions?

Your Symptoms Are Likely Benign Musculoskeletal Pain Combined with Anxiety-Related Hypervigilance, Not a Cardiopulmonary Emergency

Your SpO2 of 91-97% (average 93%) during sleep and HRV of 16 are concerning measurements that warrant medical evaluation, but your morning SpO2 of 97-98% and symptom resolution with stretching strongly suggest positional discomfort and anxiety rather than serious cardiopulmonary disease.

Understanding Your Oxygen Saturation During Sleep

Normal Nocturnal Oxygen Variation

• Healthy adults experience greater oxygen saturation variation during sleep than wakefulness, with mean nocturnal nadirs around 90.4% (±3.1%) 1
• Adults over 60 years typically spend 10% of the night below 92.8%, with a mean nadir of 89.3% (±2.8%) 1
• Your average SpO2 of 93% falls within the normal range for nocturnal sleep, and transient dips are physiologic 2, 1

When to Be Concerned About Oxygen Levels

• Most experts emphasize maintaining SpO2 above 90% for acutely ill patients, as sudden exposure below 80% can cause altered consciousness 3, 1
• Your morning finger oximeter reading of 97-98% indicates normal oxygenation when awake and at rest 3
• The critical threshold is sustained SpO2 below 90% for 5 minutes or more, not transient dips 4, 2

Important Caveat About Single Readings

• A single "spot reading" during sleep should be interpreted with extreme caution 1
• Ideally, oxygen saturation should be observed for several minutes to differentiate sustained hypoxemia from transient normal nocturnal dips 2, 1
• Motion artifacts and position changes can affect pulse oximetry readings 1

Understanding Your Heart Rate Variability

HRV and Sleep Quality

• HRV naturally decreases during periods of stress, anxiety, and poor sleep quality 5, 6
• Your HRV of 16 (compared to your baseline of 18-25) likely reflects the anxiety and disrupted sleep you experienced, not underlying cardiac disease 5
• Autonomic nervous system responses can be blunted under stress and anxiety, affecting HRV measurements 7

HRV in Context of Your Symptoms

• The temporal relationship is key: your HRV dropped during a night of anxiety and poor sleep positioning, not before your symptoms started 5
• HRV typically recovers with improved sleep quality and reduced anxiety 6
• In fibromyalgia patients with pain and poor sleep, HRV shows modest positive correlations with sleep quality and negative correlations with pain 6

Understanding Your Rib and Shoulder Pain

Positional Musculoskeletal Pain

• Your pain pattern—occurring with specific sleep positions, worsening with pressure from the bed, and resolving with stretching—is classic for musculoskeletal discomfort 4
• The fact that sitting up for 20 minutes reduced your pain and allowed you to sleep again strongly suggests positional rather than cardiac or pulmonary pathology 4

The Anxiety-Pain Cycle

• Your description reveals a clear anxiety escalation: mild rib discomfort → worry → left shoulder pain → more worry → inability to sleep 4
• This pattern is characteristic of anxiety-amplified pain perception, not progressive cardiopulmonary disease 4
• Vital signs (including SpO2) can change during anxiety but should not be used alone to assess pain or cardiac status 4

What You Should Do Next

Immediate Actions (Next 24-48 Hours)

• Monitor your symptoms during normal daily activities—if rib/shoulder pain persists with movement or deep breathing, seek medical evaluation 4
• Check your wearable device's SpO2 data for tonight: if average SpO2 remains above 90% and you sleep normally, this supports benign etiology 2, 1
• Practice sleep hygiene: avoid sleeping in positions that cause pressure pain, use supportive pillows 4

When to Seek Urgent Medical Attention

• Seek immediate care if you develop: chest pain with exertion, shortness of breath at rest, sustained SpO2 below 90% while awake, or worsening symptoms despite position changes 3, 1
• New onset of daytime sleepiness, witnessed apneas, or morning headaches warrant sleep evaluation 4, 2

Recommended Medical Evaluation (Within 1-2 Weeks)

• Schedule a primary care visit to review your wearable device data comprehensively, including trends over multiple nights 4, 2
• Consider overnight oximetry or polysomnography if your device consistently shows average SpO2 below 90% or if you develop symptoms of sleep-disordered breathing 4, 2
• Pulmonary function testing is indicated only if you have daytime symptoms (fatigue, concentration difficulties, shortness of breath) or concerning SpO2 patterns persist 4

Critical Pitfalls to Avoid

Don't Over-Interpret Single Night's Data

• One night of abnormal readings during anxiety and poor sleep positioning does not indicate chronic disease 2, 1
• Alcohol, sedatives, and anxiety can all exaggerate normal nocturnal oxygen variation 1

Don't Ignore Persistent Patterns

• If your HRV remains consistently low (below 18) for multiple nights with normal sleep, this warrants evaluation 5
• If your average nocturnal SpO2 remains below 90% for multiple consecutive nights, polysomnography is indicated 4, 2

Recognize Anxiety's Physical Manifestations

• Anxiety can cause real physical symptoms including chest wall pain, altered breathing patterns, and autonomic changes 4
• The resolution of your symptoms after calming down and changing position strongly supports anxiety as a contributing factor 4

Your symptoms most likely represent a combination of uncomfortable sleep positioning causing musculoskeletal pain, amplified by anxiety that disrupted your sleep and temporarily affected your HRV. The normal morning SpO2 and symptom resolution with stretching are reassuring. However, if patterns persist or worsen, formal sleep and cardiac evaluation is warranted.