Can you develop a PICO question for the instillation of saline during endotracheal suctioning?

Looking for the best practices on endotracheal suctioning often involves determining whether open or closed suctioning is better.  Open suctioning requires disconnecting the patient from the ventilator, while closed suctioning allows the patient to remain connected to the ventilator.  While closed suctioning is generally preferred, it is not always the best practice, but the research investigated looked specifically at closed suctioning because of the research question presented.   

In 1999, Kinloch ran an observational study that compared oxygenation in patients that either had normal saline instilled at the start of endotracheal tube suctioning or did not have saline instilled.  Until that point in time, it was believed that by removing secretions, saline instillation would improve oxygenation status. However, the conclusions of that study suggested that instillation of normal saline before the beginning of endotracheal suctioning actually resulted in lower mixed venous oxygen saturation and longer recovery times to return to baseline level.

In 2007, Branson looked at secretion management and determined that normal saline instillation was simply not supported by the literature, but did recommend other techniques, specifically high-temperature humidity, that could be used to help manage secretions.

In 2017, Wang et al. did a meta-analysis of randomized controlled trials to assess the efficacy of normal saline instillation before suctioning.  They were concerned that, although normal saline instillation was the standard-of-care, it is associated with negative health outcomes such as increased heart rate, decreased oxygenation, dyspnea, and blood pressure. The results revealed that normal saline instillation decreases oxygenation, but showed no impact on other vital parameters.