3.1 : Pneumonia I: Introduction

Pneumonia is an acute respiratory infection that targets the lungs, specifically the alveoli. These tiny air sacs, essential for oxygen exchange, become engorged with pus and fluid, severely hindering breathing, decreasing oxygen absorption, and causing significant pain and discomfort during respiration.

Risk Factors

Various factors influence the likelihood of developing pneumonia. Age plays a crucial role, with infants, children under two, and individuals over 65 at increased risk due to their less robust immune systems. Smoking further exacerbates this risk by damaging the lungs' natural defense mechanisms against infection. Hospitalization, particularly in intensive care units or when mechanical ventilation is required, markedly heightens pneumonia risk. This is also true for people with compromised immune systems, including those living with HIV/AIDS, organ transplant recipients, or those undergoing specific treatments like chemotherapy or prolonged steroid use. Additionally, residing in nursing homes or other long-term care facilities can amplify exposure to infectious agents, increasing pneumonia risk, as does recent surgery or trauma to the chest or abdomen. Chronic diseases, such as COPD or diabetes, also elevate the risk.

Classification

Pneumonia can be broadly categorized into Community-Acquired Pneumonia (CAP) and Medical Care–Associated Pneumonia.

• Community-Acquired Pneumonia (CAP): CAP affects the general population, including healthy individuals. This form occurs outside of hospital settings or within the first 48 hours of hospitalization. It occurs when people are exposed to common pathogens like Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, and Respiratory Syncytial Virus.

• Medical Care–Associated Pneumonia: This encompasses hospital-associated pneumonia, which develops more than 48 hours after admission without being present or incubating at the time of hospitalization. These include ventilator-associated pneumonia, occurring after endotracheal intubation; and healthcare-associated pneumonia, affecting individuals with recent hospital stays or those in long-term care facilities. Individuals who have received recent antibiotic or chemotherapy treatments are especially vulnerable.

Other Types:

• Aspiration Pneumonia: This type arises from inhaling food, liquid, vomit, or saliva into the lungs and is typically seen in individuals with difficulties swallowing or impaired gag reflexes.

• Opportunistic Pneumonia: Opportunistic pneumonia occurs in individuals with compromised immune systems, such as AIDS patients, chemotherapy recipients, or recent organ transplant patients. Opportunistic pathogens typically do not cause disease in healthy individuals but can lead to serious infections when the immune defenses are compromised. Examples of these pathogens include Cytomegalovirus and certain fungal infections like Aspergillus.

A comprehensive understanding of pneumonia's risk factors, classifications, and varieties is vital for its prevention, timely diagnosis, and effective management.