Prognostic value of on admission arterial PCO2 in hospitalized patients with community-acquired pneumonia

Zeynab Yassin, Mohammad Saadat, Hamidreza Abtahi, Abbas Rahimi Foroushani, Soheil Peiman


Background: There is little data about the correlation between the outcome of community acquired pneumonia (CAP) and the hypercapnic type respiratory failure. In this study we prospectively investigated the prognostic significance of first arterial CO2 tension in patients hospitalized with CAP.
Methods: In this prospective study patients with CAP, admitted to a general hospital were included. PaCO2 was measured for each subject in an arterial blood sample drawn in the first 2 hours and its correlations with three major outcomes were evaluated: intensive care unit (ICU) admission, duration of admission and mortality in 30 days.
Results: A total of 114 patients (mean age: 60.9±18.3; male: 51.8%) diagnosed with CAP were included. Significant relationship was not found between PaCO2 and mortality (P=0.544) or ICU admission (P=0.863). However advanced age, associated CHF, high BUN levels, high CURB-65 scores, associated pleural effusion in chest X-ray and being admitted to the ICU (P=0.012, 0.004, 0.003, <0.001, 0.045 and <0.001 respectively) were all significant prognostic factors of higher mortality risks. Prognostic factors for ICU admission were a history of malignancy (P=0.004), higher CURB-65 (P<0.001) scores and concomitant pleural effusion (P=0.028) in chest X-ray. Hypercapnic patients hospitalized for longer duration compared with normocapnic subjects. Furthermore, patients with lower pH (P=0.041) and pleural effusions (P=0.002) were hospitalized longer than the others.
Conclusions: There was less prominent prognostic value regarding on-admission PaCO2 in comparison to other factors such as CURB-65. Considering the inconsistent results of surveys conducted on prognostic value of PaCO2 for CAP outcomes, further investigations are required to reach a consensus on this matter.