Objectives: 

Critical care patients are in need of respiratory assistance, though prolonged mechanical ventilation presents typical complications, such as fatal bacterial infections. Prompt diagnosis and efficient monitoring of the respiratory infection is essential to achieve a positive prognosis. The present study aims to evaluate sputum cell index as a diagnostic tool in upper respiratory tract infection and patient morbidity.

Materials: 

Induced-sputum samples were collected from 17 consecutive critical care patients upon admission and every other day until patient dissolution, over a maximum period of two weeks. Total sputum cell count was evaluated by trypan blue exclusion in fresh suspensions. Differential nucleated cell count was evaluated on cytospin slides by May Grünwald-Giemsa staining. Mucus was tested for microbial infections and GC scale was evaluated by an expert physician. Statistical analysis was performed by Mann-Whitney U test.

Results: 

Expectorate was enriched in neutrophils and macrophages. Squamous cells accounted approximately for 5% of the total nucleated cells, however significant variance among samples was found, probably due to patient handling. Macrophage population and phagocytosis increased in accordance with clinical evidence of tracheobronchitis (p<0.05). Eosinophils count was particularly enhanced in a subset of patients. Lymphocytes index did not show any correlation with tracheobronchitis incidence or progression.

Conclusions: 

Our findings support that the initiation of a respiratory tract infection is associated with foamy macrophages and eosinophils presence. The evaluation of sputum cell index, advantageous compared to the overdue mucus culture, could be useful in the diagnosis of a developing condition. In contrast to the traditional consensus of extensive lymphocyte activation in chronic inflammatory conditions, detected in BAL fluid, mechanical ventilation for a period of two weeks is not associated with lymphocyte infiltration of the upper respiratory tract.