Clinical signs

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A UK-based mixed-methods study, which included a rapid review of the literature and an extensive consensus-building exercise among UK clinicians, provides the following guidance for remote assessment of primary care patients who do not have red alert symptoms or signs.20  

Oxygen saturation


  • Resting oxygen saturations of 94% to 95% are of clinical concern
  • patients with resting oxygen saturation of 93% or below require urgent referral from primary care
  • a fall of 2% after a 40-step exercise test would be of clinical concern
  • a fall of 3% or more requires urgent referral
  • a 40-step test should not be undertaken without clinical supervision if a patient’s resting oximetry reading is below 96%
  • for patients without access to a pulse oximeter, profound tiredness or fatigue such that the patient is noticeably more tired doing usual activities or struggling to get out of bed indicate clinical concern
  • being unable to speak because of tiredness suggests the need for urgent referral.20

Home oximetry guidance for Scotland advises people to seek immediate medical assistance if they have an at-rest reading of <94%, and seek advice from their healthcare professional if the reading is 94%,  A discussion paper highlighted the importance of individual patient baselines and of trends in saturations as part of assessment (rising, stable, falling).22

People with black or brown skin are three times more likely than people with light skin pigmentation to have pulse oximeter readings in the normal range but arterial blood gas levels in the hypoxic range. This relates mainly to saturations below 90%.22 

Respiratory rate


  • A respiratory rate (per minute) of 21–24 is of some clinical concern
  • respiratory rate of 9–11 or 25–29 is of greater concern
  • <8 or >30 should lead to urgent referral from primary care
  • if respiratory rate cannot be measured, breathlessness on mild to moderate exertion eg walking room to room or getting out of a chair should be considered to be of clinical concern and severe breathing difficulty or inability to complete sentences at rest is indicative of need for urgent referral
  • the trajectory of breathlessness should also be considered important with worse breathlessness than yesterday being of clinical concern and significant deterioration in the last hour indicating need for urgent referral.20


Heart rate


  • A heart rate of 41–50 or 91–110 beats per minute is of clinical concern
  • a heart rate of 111–130 is of greater clinical concern
  • heart rate <40 or >130, if unexplained, indicates need for urgent referral from primary care.20