Subglottic secretion volume and viscosity: effect of systemic volume and oral hydration

Removal of secretions from the subglottic space, which is the larynx cavity below the glottis that contains the vocal cords, reduces the risk for ventilator associated pneumonia. Relationships between factors associated with subglottic secretion volume and viscosity have not been investigated. Subglottic secretions may have a possible link with systemic volume status and oral cavity hydration. The purpose of this study was to examine the relationships among systemic volume, oral cavity hydration, and subglottic secretion (SS) volume and viscosity in mechanically ventilated adults.

Seventy daily oral and SS samples were obtained over a 24-hour collection period from 15 mechanically ventilated adults. Markers of systemic volume and oral cavity hydration and measurements of SS volume and viscosity were collected and analyzed.

The daily volume of oral secretions ranged from 0 to 1.0 mL (SD 0.180 mL), and SS ranged from 0 to 15 mL (SD 22.9 mL). BUN/creatinine ratio (marker of systemic volume status) was moderately correlated with oral secretion volume (r = -0.43). Weak correlations were identified between SS volume and oral volume (r = 0.29) and SS viscosity and oral viscosity (r = 0.22). No other linear relationships were identified among the variables.

This study confirmed that SS accumulation occurs, the amount varies widely, and the secretions are highly viscous. SS volume and viscosity were not found to have a very strong relationship with the variables measured. Nevertheless, clinical implications for practice are present. Further research is needed to understand secretion dynamics in ventilated adults to prevent complications and promote positive patient outcomes.