Objective     To analyze the clinical features of 46 hospitalized patients with influenza A (H1N1) pneumonia and to study the risk factors for the development of respiratory failure.      Methods     Medical records of 46 hospitalized patients with influenza A (H1N1) pneumonia were collected and analyzed

including basic status

symptoms

physical signs

laboratory data

therapeutic regimens

etc. The patients were divided into two groups: a respiratory failure group and a non-respiratory failure group.     

Results     Of the 46 patients

14 developed respiratory failure

with 1 dead case. All of the non-respiratory failure patients survived. Presence of dyspnea (10 cases vs 6 cases)

presence of hemoptysis (10 cases vs 5 cases)

lymphopenia (158±18/μl vs 192±26/μl)

PaO

2

/FiO

2

ratio (182±23 mmHg vs 426±45 mmHg)

SOFA score (4 vs 1)

and score of infiltration on chest X-ray at admission (2.3±1.3 vs 1.2±0.8) were significantly different between the respiratory failure group and non-respiratory failure group (P0.01). The patients with respiratory failure had longer ICU stay than those without respiratory failure (26 d vs 5 d; P=0.000 1). A multivariate logistic regression analysis showed a correlation between the development of respiratory failure and the following factors: SOFA score at admission ≥4

initial lymphocyte count ≤600/μl

duration from onset to initial administration of oseltamivir 48 h

and infiltration on chest X-ray at admission ≥75%.      Conclusion     The risk factors for influenza A (H1N1) pneumonia with respiratory failure includes duration from onset to initial administration of oseltamivir 48 h

initial lymphocyte count ≤600/μl

SOFA score at admission ≥4

and infiltration on chest X-ray at admission ≥75%.