Background: Devices that limit microaspiration through the cuffs of endotracheal tubes could help prevent ventilator-associated pneumonia (VAP). The amount of tracheal microaspirations could be a relevant study endpoint. The aim of our study was to assess whether amylase measured in tracheal secretions constituted a relevant marker for microaspiration.
Methods: Twenty-six patients, intubated for at least 48 h and supplied with a subglottic secretion-suctioning device, constituted a group with a high risk of microaspiration. Twelve non-ventilated patients that required a bronchoscopy procedure constituted a group with a low risk of microaspiration (the control group). Tracheal (T) amylase was compared between the groups. In the intubated group, a series of oral (O), subglottic (Sg) and tracheal (T) suction samples were collected and T/O, T/Sg, Sg/O amylase ratios were determined.
Results: Amylase was measured in 277 (89 Sg, 96 B, 92 T) samples from the intubated group and in 12 T samples from the control group. Tracheal amylase was lower in the control group than the intubated group (191 [10-917] vs. 6661 [2774-19,358] IU/L, P<0.001). Amylase gradually increased from tracheal (6661 [2774-19,358] IU/L), to subglottic (130,750 [55,257-157,717] IU/L), to oral samples (307,606 [200,725-461,300] IU/L), resulting in a median 5.5% T/O ratio. In a subset of intubated patients, T amylase samples were assessed in two different laboratories, and gave reproducible results.
Conclusion: Tracheal amylase was easy to collect, transport, and measure. The T/O amylase ratio is a first step towards quantifying oropharyngeal to tracheal microaspiration in mechanically-ventilated patients.