The clinical range is broad, from acute monitoring and addiction care to surgical reconstruction, cancer survivorship and specialist evidence. Pulse oximetry is an estimate, not a diagnosis. A concerning saturation should first trigger assessment of the patient and the signal: inspect the pleth waveform, compare the oximeter pulse with the monitored heart rate, review perfusion and reposition the probe if necessary.

Peripheral readings can lag by 15–30 seconds or longer during rapid deterioration or recovery, especially with low cardiac output or distal probes. A value of 100% cannot distinguish adequate oxygenation from marked hyperoxia, while a normal peripheral oxygen saturation or arterial oxygen tension does not exclude carbon monoxide poisoning or methaemoglobinaemia. When dyshemoglobinaemia is plausible, co-oximetry answers a different question.

Chest-compression technique offers a related measurement problem. Small lateral changes in hand position may alter the structures compressed and the forward flow generated. Transoesophageal ultrasound can show anatomy during cardiopulmonary resuscitation, and a palpable femoral impulse can give immediate feedback. The proposed position 4 cm left of the sternum remains an emerging observation, not established guidance, so it should not distract from high-quality compressions.

Preserve treatment while managing the acute problem

In suspected opioid overdose, use the naloxone formulation immediately available, support ventilation, activate emergency help and allow time for effect before rapidly stacking doses. When an outpatient methadone dose cannot be confirmed, pursue labelled bottles, photographs, family contacts, previous clinicians and records; then use conservative dosing with reassessment of sedation and objective withdrawal.

For acute or perioperative pain, stopping established methadone or buprenorphine creates an opioid deficit and may worsen both withdrawal and analgesic requirements. Continue maintenance treatment, use multimodal analgesia and titrate additional short-acting opioids to physiological tolerance when indicated. Neutral documentation of pain, withdrawal, sedation and response avoids turning tolerance into a judgement about motive.

Do not promote a signal into certainty

Several specialist updates require restrained interpretation. A necrotic lesion does not establish brown recluse envenomation without compatible geography, exposure and ideally expert identification; infectious, inflammatory, vascular and metabolic mimics remain possible. Jaundice or dark urine after a suspected bite should prompt concern for haemolysis and acute kidney injury.

In adult phenylketonuria, a positive regional brain-age gap describes structural resemblance on magnetic resonance imaging, not proven accelerated ageing. Short-term phenylalanine elevation produced subtle, largely reversible changes without major cognitive decline, but it does not answer the consequences of years of exposure.

Vamorolone’s better height Z-scores may indicate less growth suppression in Duchenne muscular dystrophy, yet indirect cross-trial comparisons cannot establish superiority. Early signals for glucagon-like peptide-1 receptor agonists in alcohol use disorder deserve the same discipline: possible reductions in craving or consumption do not make them established first-line treatment.