The number needed to treat can be calculated for ventilator-associated pneumonia reduction strategies such as subglottic secretion drainage technology based on previous work establishing its relative risk reduction. Assuming an incidence of 4%, employing subglottic secretion drainage in 33 patients will prevent one case of ventilator-associated pneumonia, and thus potentially 4 cases annually in an average hospital in the United States. With a previously described limit of £300 ($470 USD) additional cost per 10 days of ventilation as a threshold of investment for technologies to reduce ventilator-associated pneumonia, subglottic secretion drainage technology is both clinically and cost effective.
Wyncoll and Camporota's correspondence  provides a valuable tool allowing clinicians the ability to assess the number needed to treat (NNT) and cost-effectiveness of various ventilator-associated pneumonia (VAP) prevention strategies. Subglottic secretion drainage (SSD) technology is one VAP-reduction strategy for which NNT can easily be calculated based on its established relative risk reduction.
Smulders and colleagues  conducted a randomized clinical trial in 150 patients receiving mechanical ventilation and found that intermittent SSD reduced the risk of VAP by 75% (P = 0.014). Utilizing Wyncoll and Camporota's table, and assuming a VAP incidence of 4%, utilizing SSD in 33 patients will prevent one episode of VAP. In the United States, the average hospital has approximately 131 patients per year who require mechanical ventilation >96 hours (unpublished observations). Utilizing SSD in these average hospitals would likely prevent four cases of VAP per year. In addition, SSD is a cost-effective intervention. At the assumed VAP rate of 4%, Wyncoll and Camporota determined an upper threshold of £300 ($470 USD) additional cost per 10 days of ventilation to be a cost-effective investment in technologies that reduce VAP by up to 75%. Costs of SSD technology interventions are beneath this threshold.
Wyncoll and Camporota's framework illustrates that use of SSD is both a clinically and cost-effective strategy to reduce VAP. The NNT demonstrates that average hospitals will observe and benefit from these strategies. SSD technologies warrant further adoption and appropriate utilization.
NNT: number needed to treat; SSD: subglottic secretion drainage; VAP: ventilator-associated pneumonia.
SK is an employee of Covidien, and receives salary and equity compensation.
SK would like to thank Mary Erslon, RN, MSN, MBA (Covidien) for writing assistance.