New Horizons in Hospital Acquired Pneumonia in Older People

Victoria Ewan; Thomas Hellyer; Julia Newton; John Simpson

Disclosures

Age Ageing. 2017;46(3):352-358. 

In This Article

Abstract and Introduction

Abstract

Approximately 1.5% of hospital patients develop hospital acquired pneumonia. Aspiration is the major risk factor for pneumonia and is associated with reduced ability to mechanically clear respiratory pathogens into the stomach. Currently non-invasive methods of diagnosing hospital acquired pneumonia are less robust than invasive methods, and lead to over-diagnosis. Accurate diagnosis is key to surveillance, prevention and treatment of HAP, and also to improving outcomes; newer imaging modalities such as phase contrast X-ray imaging and nanoparticle enhanced magnetic resonance imaging may help. Potential preventative strategies such as systematic swallowing assessment in non-stroke patients, and interventions such as improving oral hygiene need further, robust randomised controlled trials. Antibiotics are likely to continue to be the mainstay of treatment, and new antibiotics such as ceftobiprole are likely to have a role in treating hospital acquired pneumonia. Given the spread of antimicrobial resistance, alternative treatment strategies including bacteriophages, peptides and antibodies are under investigation. Reducing the incidence of hospital acquired pneumonia could decrease length of hospital stay, reduce inappropriate antibiotic use, and both improve functional outcomes and mortality in our increasingly aged population.

Introduction

Respiratory infections are now the commonest healthcare-associated infection in Europe,[1] and include hospital acquired pneumonia (HAP) and ventilator associated pneumonia (VAP). HAP refers to pneumonia (infective inflammation of the alveoli) contracted after 48 h in a hospital setting visible as new infiltrates on chest radiograph, not associated with mechanical ventilation. VAP refers to pneumonia contracted after 48 h of mechanical ventilation either via endotracheal tube or tracheostomy.

HAP is something of a Cinderella disease; compared to its estimated incidence of 1.5% of all hospital admissions[2] it has received little attention or research.[3] This may be in part because HAP is hard to study. While advances have been made in diagnosing VAP using invasive sampling techniques such as bronchoalveolar lavage,[4] and preventative strategies have been extensively investigated.[5,6] HAP remains relatively understudied. The majority of HAP is seen in older, frailer people, where cognitive impairment, delirium and dementia are common, and where bronchoscopy or ventilation (and thus invasive sampling) may not be in the patient's best interests.

Respiratory infections account for 26% of healthcare associated infections across Europe.[1] In one study of over 600,000 patients undergoing abdominal surgery, patient diagnosed with HAP experienced a 10-day increase in length of stay, a fourfold increase in the likelihood of transfer to a healthcare institution, a 75% increase in mean healthcare cost and treatment with antibiotics.[7] However, diagnostic uncertainty means that at least some of these antibiotic prescriptions, frequently with broad-spectrum action, are likely unnecessary, potentially contributing to the spread of antibiotic resistance, while the real underlying diagnosis goes untreated.

HAP occurs because of micro (or macro-) aspiration of the patients' own oropharyngeal material[8] and the process is outlined in Figure 1. 'Hospital' type respiratory pathogens occur more commonly in the mouths of those who are unable to mechanically clear their oral secretions, a situation seen in patients with dysphagia or in patients with a reduced level of consciousness.[9] Thus impaired swallow has two steps. Firstly there is stagnation within the mouth, such that environmental organisms are not cleared effectively into the stomach. Secondly this stagnant oral material is then misdirected into the lungs, a process known as aspiration. Once aspirated, the host immunity may not be capable of reacting in a sufficiently vigorous manner to the altered microbiota,[10] and infection occurs. VAP can be seen as an extension of HAP, with each risk factor being stronger. HAP occurs due to infection developing from endogenous microbiota, rather than person to person transmission, explaining why improved environmental cleaning has not made the same impact on respiratory infection as other healthcare associated infections and hence why respiratory infection now accounts for a larger proportion of healthcare infections relative to infections that are sensitive to environmental decontamination.

Figure 1.

The pathophysiology of hospital acquired pneumonia and ventilator associated pneumonia.

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