Prevention of Respiratory Infections in Older Patients During and After Hospitalisation: A Randomised Controlled Trial

Background:

Hospital-acquired infections impact patient recovery and increase risk of deterioration. Pneumonia is the second commonest cause of death in Singapore accounting for 19% of deaths in 2014. Hospital acquired pneumonia (HAP) or nosociomal pneumonia refers to any pneumonia contracted by a patient in a hospital at least 48-72 hours after admission and is usually caused by a bacterial infection, rather than a virus. It is the most prevalent hospital-acquired infection, and has the highest mortality among the hospital-acquired infections (20-50%) . Local audit data has shown that around 60% of deaths in hospitalised older patients are due to pneumonia, of which a significant proportion are due to HAP or health care associated pneumonia (HCAP).

A meta-analysis of respiratory studies has shown low numbers of studies evaluating novel antimicrobial agents for hospital-acquired pneumonia (15.9%) suggesting further research or novel approaches are needed. The prevalence of nosociomal pneumonia in a European study was 13.9%. Pneumonia acquired during periods of hospitalisation has a high morbidity, mortality and increased hospital length of stay (LOS). Audit of the 2014 data from the Geriatric Mortality meetings has shown all cause pneumonia (community acquired pneumonia (CAP) and HAP) is 55%. Currently this data is being analysed to calculate the proportion of deaths attributable to HAP vs CAP.

The pathophysiology of pneumonia in the elderly is primarily due to aspiration pneumonia (ASP). ASP comprises predominantly two pathological conditions: airspace infiltration with bacterial pathogens and dysphagia-associated aspiration. The primary route of infection is believed to be through microaspiration of organisms that have colonised the oropharynx and gastrointestinal tract. Hospitalised patients become colonised with microorganisms from the hospital environment within 48 hours and severity of respiratory infection is related to the number and virulence of these microorganisms as well as the hosts immune response.

Swallowing difficulties, poor oral hygiene and reduced immune response are inherent in the older population contributing to an increased risk of HAP. In addition, older patients have an increased risk of aspiration of gastric contents due to a laxity of lower oesphageal sphincter, an anatomical sphincter that relies on diaphragmatic function. Many older patients locally are fed via naso-gastric tube and the presence of a naso-gastric tube increases the risk of aspiration pneumonia occuring during hospitalisation. Supine positioning also predisposes to micro aspiration from the oropharynx and stomach with many patients placed routinelyin a supine position to undertake their basic care needs. Positioning in the semi recumbant position has been shown to reduce microaspiration with elevations of 30-45 degrees by improving supraglottic drainage.