Accuracy of PaO2 /FiO2 calculated from SpO2 for severity assessment in ED patients with pneumonia.

BACKGROUND AND OBJECTIVE: Assessment of oxygenation in patients with community-acquired pneumonia is critical for treatment. The accuracy of percutaneous oxygen saturation (SpO2 ) determined by pulse oximetry is uncertain, and it has limited value in patients receiving supplemental oxygen. We hypothesized that calculation of partial arterial oxygen concentration/inspired oxygen faction (PaO2 /FiO2 ) from SpO2 by the Ellis or Rice equations might adequately correlate with PaO2 /FiO2 measured by arterial blood gases. METHODS: We studied 1004 patients with pneumonia in the emergency department with simultaneous measurement of SpO2 and PaO2 from two cohorts from Valencia, Spain and Utah, USA. We compared SpO2 with measured SaO2 , compared the equations' accuracy in calculating PaO2 /FiO2 and determined how often patients would be misclassified at clinically important thresholds. We compared estimated PaO2 /FiO2 to measured PaO2 /FiO2 using the Spearman correlation. RESULTS: Pairwise correlation of SpO2 with SaO2 was moderate (rho = 0.66; P < 0.01). Both equations performed similarly among patients with lower PaO2 /FiO2 ratios. The Ellis equation estimated PaO2 /FiO2 from SpO2 more accurately than the Rice equation in patients with PaO2 /FiO2 ≥200. Simple agreement between calculated and measured P/F was 91% and 92%, respectively. CONCLUSIONS: The Ellis equation was more accurate than the Rice equation for estimating PaO2 /FiO2 , especially at higher levels of P/F ratio. Estimation of PaO2 /FiO2 from SpO2 is accurate enough for initial oxygenation assessment. Ellis and Rice equations could misclassify 20% and 30% of patients, respectively, at higher levels of PaO2 /FiO2 . For patients with abnormal oxygenation falling near thresholds for clinical decision making, arterial blood gas measurement preferably on room air is more accurate.

Does prolonged onset of symptoms have a prognostic significance in community-acquired pneumonia?

BACKGROUND AND OBJECTIVE: Severity assessment is made at the time of the initial clinical presentation in patients with community-acquired pneumonia (CAP). It is unclear how the gap between time of presentation and duration of symptoms onset may impact clinical outcomes. Here we evaluate the association of prolonged onset of symptoms (POS) and the impact on clinical outcomes among hospitalized patients with CAP. METHODS: This was a prospective, multicentre study of CAP in Spain. The primary outcomes were the clinical factors associated with POS defined as days from symptoms onset to pneumonia diagnosis >7 days. The secondary outcomes were intensive care unit (ICU) admission, the presence of suppurative complications, septic shock and 30-day mortality. RESULTS: We enrolled 1038 patients diagnosed of CAP: 152 (14.6%) patients had a POS. In multivariate analysis, the presence of prior corticosteroid therapy, alcohol abuse, prior antibiotic therapy, and confusion, urea, respiratory rate, blood pressure and age 65 years or older score 0-1 was independently associated with POS. Patients with POS had a higher incidence of suppurative complications, but not of 30-day mortality when compared with a shorter onset of symptoms. CONCLUSIONS: Approximately 15% of patients diagnosed with CAP had POS. Risk factors associated with POS were previous corticosteroids and antibiotic therapy, alcoholism and less severe pneumonia. POS was associated with a higher rate of suppurative complications and less need for ICU admission.

Hypoxemia adds to the CURB-65 pneumonia severity score in hospitalized patients with mild pneumonia.

BACKGROUND: Hypoxemia may influence the prognosis of patients with mild pneumonia, regardless of the initial CURB-65 score (confusion, blood urea nitrogen > 20 mg/dL, respiratory rate > 30 breaths/min, blood pressure < 90/60 mm Hg, and age ≥ 65 y). OBJECTIVE: To determine the risk factors associated with hypoxemia and the influence of hypoxemia on clinical outcomes in hospitalized patients with mild pneumonia. METHODS: We performed a multicenter prospective cohort study of 585 consecutive hospitalized patients with mild pneumonia (CURB-65 groups 0 and 1). We stratified the patients according to the presence of hypoxemia, defined as a P(aO(2))/F(IO(2)) < 300 mm Hg on admission. We assessed the risk factors associated with hypoxemia, hypoxemia's influence on the course of pneumonia, and clinical outcomes (mortality, hospital stay, and need for intensive care unit admission), with multivariable regression. RESULTS: Fifty percent of the patients (294 cases) had hypoxemia on admission. The risk factors independently associated with hypoxemia were: bilateral radiological involvement (odds ratio 2.8, 95% CI 1.1-7.5), history of COPD (odds ratio 2.5, 95% CI 1.4-4.3), and hypoalbuminemia (odds ratio 2.0, 95% CI 1.1-3.5). The hypoxemic patients had longer hospital stay, higher intensive care unit admission rate, higher rate of severe sepsis, and higher mortality than the non-hypoxemic patients. CONCLUSIONS: Hypoxemia in patients with mild pneumonia is independently associated with several adverse clinical and radiological variables, and the hypoxemic patients had worse clinical outcomes than the non-hypoxemic patients. Therefore, additional attention should be paid to the presence of hypoxemia, regardless of a low CURB-65 score.