Publications & Reports

Inability of single resting arterial blood gas to predict significant hypoxaemia in chronic obstructive pulmonary disease.

Trauer JM, Gielen C, Trauer T, Steinfort C
Department of Respiratory Medicine, The University of Melbourne, Melbourne, Victoria, Australia. [email protected]


BACKGROUND: While point measurement of resting arterial partial pressure of oxygen (P(a)O(2)) is the traditional gold-standard for assessment of oxygenation in chronic obstructive pulmonary disease (COPD), 24-h oximetry may identify further patients with clinically significant hypoxaemia. We aimed to describe the relationship between these two parameters and identify other correlated variables. METHODS: All patients registered with the Barwon Health Hospital Admission Risk Program from 1 March to 31 October 2008 for the diagnosis of COPD were identified. The main inclusion criteria were obstructive spirometry, clinical stability and moderate resting hypoxaemia (P(a)O(2) 56-70 mmHg). All patients underwent 24-h oximetry, arterial blood gas, spirometry, anthropometry and telephone questionnaire, and 23 patients also completed polysomnography. RESULTS: Inclusion criteria were met in 35 of 287 patients. Mean recording time was 23.5 h, representing 97% of intended oximetry time. Nineteen patients (54%) spent greater than 30% of recorded oximetry time below 90%. There was a moderate inverse correlation between time below 90% saturations and P(a)O(2) (r=-0.40, P= 0.02), with body mass index (BMI) the only other independent predictor of the primary outcome identified (r= 0.39, P= 0.02). Correlations were similar for waking hours considered separately. However, for sleeping oximetry, BMI and age were the only independent predictors of time below 90%. Polysomnography demonstrated a high prevalence of rapid eye movement-related hypoventilation and obstructive sleep apnoea syndrome. CONCLUSIONS: Many patients with moderate hypoxaemia on resting P(a)O(2) desaturate significantly on ambulatory oximetry. The correlation between P(a)O(2) and proportion of saturations below 90% is moderate and similar to BMI, but this pattern does not hold during sleeping hours.


  • Journal: Internal Medicine Journal
  • Published: 01/04/2012
  • Volume: 42
  • Issue: 4
  • Pagination: 387-394