Arterial blood gas and pulse oximetry in initial management of patients with community-acquired pneumonia

OBJECTIVE: To identify the factors associated with the use of arterial bloo d gas (ABG) and pulse oximetry (PO) In the initial management of patients w ith community-acquired pneumonia (CAP) and arterial hypoxemia at presentati on. PARTICIPANTS: A total of 944 outpatients and 1,332 inpatients with clinical and radiographic evidence of CAP prospectively enrolled from 5 study sites in the United States and Canada. ANALYSES: Separate multivariate logistic regression analyses were used to 1) compare measurement of ABG and PO withi n 48 hours of presentation across sites while controlling for patient diffe rences, and 2) Identify factors associated with arterial hypoxemia (PaO2 <6 0 MM Hg Or SaO(2) <90% for non - African Americans and <92% for African Ame ricans) while breathing room air. RESULTS: Range of ABG use by site was from 0% to 6.4% (P =.06) for outpatie nts and from 49.2% to 77.3% for inpatients (P <.001), while PO use ranged f rom 9.4% to 57.8% for outpatients (P <.001) and from 47.9% to 85.1% for inp atients (P <.001). Differences among sites remained after controlling for p atient demographic characteristics, comorbidity, and illness severity. In p atients with 1 or more measurements of oxygenation at presentation, hypoxem ia was independently associated with 6 risk factors: age >30 years (odds ra tio (OR], 3.2; 95% confidence Interval [CII, 1.7 to 5.9), chronic obstructi ve pulmonary disease (OR, 1.9; 95% CI, 1.4 to 2.6), congestive heart failur e (OR, 1.5; 95% CI. 1.0 to 2.1), respiratory rate >24 per minute (OR, 2.3; 95% CI, 1.8 to 3.0), altered mental status (OR, 1.6; 95% Cl, 1.1 to 2.3). a nd chest radiographic infiltrate involving >1 lobe (OR, 2.2; 95% Cl, 1.7 to 2.9). The prevalence of hypoxemia among those tested ranged from 13% for I npatients with no risk factors to 54.6% for inpatients with greater than or equal to 3 risk factors. Of the 210 outpatients who had greater than or eq ual to2 of these risk factors, only 64 (30.5%) had either an ABG or PO perf ormed. in the 48 outpatients tested without supplemental O-2 with greater t han or equal to2 risk factors 8.3% were hypoxemic. CONCLUSIONS: In the initial management of CAP, use of ABG and PO varied wid ely across sites. Increasing the assessment of arterial oxygenation among p atients with CAP Is likely to increase the detection of arterial hypoxemia, particularly among outpatients.