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Best evidence topic report
Capillary blood gases in COPD
Free
  1. Ross Murphy,
  2. Magnus Harrison
  1. Department of Emergency Medicine, Manchester Royal Infirmary, Oxford Road, Manchester M13 9WL, UK

    http://dx.doi.org/10.1136/emj.18.2.117

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      Report by Ross Murphy, Senior Clinical Fellow Search checked by Magnus Harrison, Clinical Research Fellow

      Clinical scenario

      A 60 year old man presents to the emergency department with an acute exacerbation of COPD. Analysis of blood gases is required. You wonder whether a capillary blood sample will be as accurate as an arterial blood sample.

      Three part question

      In [a patient with an acute exacerbation of COPD] is [a capillary blood sample as good as an arterial blood sample] at measuring [Pao2, Paco2 and pH]?

      Search strategy

      Medline 1966–11/00 using the OVID interface. {[Capillar$.mp AND (exp blood gas analysis OR blood gas$.mp OR blood gas$.mp)] AND [(exp arteries OR arter$.mp) AND (exp blood gas analysis OR blood gas$.mp OR blood gas$.mp)]} LIMIT to human AND english.

      Search outcome

      Altogether 280 papers found of which 276 were irrelevant or of insufficient quality. The remaining four papers are shown in table 2.

      View this table:
      Table 2

      Comments

      Different studies have given slightly different results. There have been no statistically significant differences identified. Moreover the differences that have been seen are clinically insignificant as well. Further research in patients with COPD would be useful.

      Clinical bottom line

      Properly taken capillary blood samples accurately reflect arterial blood gas measures of Po2, Pco2 and pH.

      Report by Ross Murphy, Senior Clinical Fellow Search checked by Magnus Harrison, Clinical Research Fellow

      References

      1. Langlands JH, Wallace WF. Small blood samples from ear-lobe puncture. Lancet1965;ii:315–17.
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      2. Begin R, Racine T, Roy JC. Value of capillary blood gas analysis in the management of acute respiratory distress. Am Rev Resp Dis1975;112:879–81.
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      3. Pitkin AD, Roberts CM, Wedzicha JA. Arterialised earlobe blood gas analysis: an underused technique. Thorax1994;49:364–6.
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      4. Dar K, Williams T, Aitken R, et al. Arterial versus capillary sampling for analysing blood gas pressures. BMJ1995;310:24–5.
        OpenUrlFREE Full Text