To address the first objective of the study, the first and last sample obtained from each subject will be analyzed individually for pH, volume, and microorganisms; all other samples will be evaluated for volume. The amount of colony forming units (CFUs) will be determined semi-quantitatively across all organisms, and presented separately for individual genera and species. The samples will be characterized with descriptive statistics including frequencies, percentages, means, medians, standard deviations, and 95% CIs. To address the second objective of the study, comparisons of pH, volume, microorganisms, and CFUs by suctioning scheme and patient-level characteristics will be conducted using chi-squared tests of independence and analysis of variance (ANOVA). Graphical methods will be developed to aid interpretation, both as a function of time and cumulatively over time.