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

Abstract

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.

• Authors: J M Trauer, C Gielen, T Trauer, C L Steinfort
• Journal: Internal medicine journal (Intern Med J) Vol. 42 Issue 4 Pg. 387-94 (Apr 2012) ISSN: 1445-5994 [Electronic] Australia
• PMID: 21118412 (Publication Type: Journal Article)
• Copyright: © 2010 The Authors. Internal Medicine Journal © 2010 Royal Australasian College of Physicians.

Chemical References

• Oxygen

Topics

• Aged
• Aged, 80 and over
• Blood Gas Analysis
• Body Mass Index
• Female
• Humans
• Hypoxia (blood, physiopathology)
• Male
• Oximetry
• Oxygen (blood)
• Polysomnography
• Pulmonary Disease, Chronic Obstructive (blood, physiopathology)
• Spirometry