Pneumonia: Introduction

Overview and Implications

Pneumonia is an infection of the lungs deﬁned as the presence of "new lung inﬁltrate plus clinical evidence that the inﬁltrate is of an infectious origin, which include the new onset of fever, purulent sputum, leukocytosis, and decline in oxygenation" (Kalil et al., 2016). Pneumonia can be caused by viruses, bacteria, and fungi and can cause mild to severe illness in people of all ages and (Centers for Disease Control and Prevention (CDC), 2020).

For pneumonia to occur in any setting, at least one of the following three conditions must occur:

significant impairment of host defenses,
introduction of an inoculum of sufficient size into the lower respiratory tract to overwhelm the host's defenses, or
the presence of highly virulent organisms (Centre for Communicable Diseases and Infection Control, 2010).

Despite advances in the understanding of contributing causes and prevention, hospital acquired pneumonia (HAP) and ventilator associated pneumonia (VAP) continue to be frequent complications of hospital care. Together, they are among the most common hospital-acquired infections (HAIs), accounting for 22 per cent of all HAIs (Kalil et al., 2016).

Hospital-acquired pneumonia (HAP)

HAP is an acute lower respiratory tract infection that is, by definition, acquired after at least 48 hours of admission to the hospital and is not incubating at the time of admission. Among patients with hospital-acquired infections, HAP is the leading cause of death and causes 22% of all hospital-acquired infections. Though generally considered to be less severe than ventilator-associated pneumonia (VAP), even in HAP serious complications occur in approximately 50% of patients, including respiratory failure, pleural effusions, septic shock, renal failure, and empyema (Kalil et al., 2016).

Ventilator-associated pneumonia (VAP)

Ventilator-associated pneumonia (VAP) is defined by infection of the pulmonary parenchyma in patients exposed to invasive mechanical ventilation for at least 48 hours and is part of ICU-acquired pneumonia. VAP remains one of the most common infections in patients requiring invasive mechanical ventilation.

VAP is reported to affect five to 40 per cent of patients receiving invasive mechanical ventilation for more than two days (Papazian et al., 2020). Compared to similar patients without VAP, these infections negatively impact important patient outcomes and prolong both the length of mechanical ventilation and hospitalization (Kalil et al., 2016). Kalil et al. indicate that while all-cause mortality associated with VAP has been reported to range from 20 to 50 per cent, the mortality directly related to VAP is debated (2016).

Risk of Transmission

In all healthcare settings, there is significant risk of transmission of acute respiratory infection (ARI) to patients and to healthcare providers. This is due to:

the large number of people (i.e., patients, family members, volunteers, visitors, workers) who come and go in these settings;
the ease with which droplet-spread respiratory illnesses can pass from one person to another;
the fact that many clients/patients/residents have other illnesses that make them more likely to experience complications from respiratory infections; and
the large number of people who seek care for or develop ARI in these settings

(Provincial Infectious Diseases Advisory Committee (PIDAC), 2013)