Respiratory Tract Infections Explained

Introduction to Respiratory Tract Infections

• All body functions need a constant oxygen supply for metabolic processes.
• The respiratory tract is highly exposed to microorganisms due to its direct interface with the external environment.
• The respiratory tract has comprehensive defense mechanisms against harmful pathogens in both the upper and lower tracts.

Upper Respiratory Tract

• The upper respiratory tract includes the nasal cavities, pharynx, and larynx.
• Nares and nasal cavities contain coarse hairs (vibrissae) and mucus to trap large particles preventing infection
• Epithelial tissues and blood vessels in the nasal cavities warm inspired air.
• Surface epithelium secretes antimicrobial peptides with bactericidal effects.
• Cilia in the nasal cavities use wavelike motion to move trapped particles via the mucociliary escalator, expelling them through sneezing and coughing.
• Tonsils and adenoids support immune response through pathogen filtering.
• The larynx (voice box) houses the epiglottis for airway protection.
• The epiglottis remains open during breathing and closes during swallowing to prevent food or fluids from entering the trachea to enable air to pass
• Resident bacteria and viruses like Staphylococcus, Streptococcus, spirochetes, mycobacteria, Pseudomonas, Proteus, and Enterococcus colonize the upper respiratory tract to maintain a healthy respiratory status.
• Competition with pathogens for attachment and bactericidal substance production eliminates microorganisms.

Lower Respiratory Tract

• The lower respiratory tract begins with the trachea, followed by bronchi, bronchioles, and alveoli.
• Ciliated and mucus-secreting cells in the lower tract use the mucociliary escalator to protect against smaller particles.
• Pathogens are trapped in a ciliated mucous layer and moved upwards to be destroyed in the stomach.
• The lower respiratory tract lacks resident flora, considered a "sterile site".
• Alveolar macrophages in the alveoli are vital for eliminating microorganisms through phagocytosis.
• Efficient gas exchange requires the alveoli to be pathogen-free.
• Respiratory infections occur if the respiratory epithelium is damaged or the number of inhaled pathogens exceeds the protective mechanisms

Inflammatory Response

• Pathogens in the respiratory tract initiate an inflammatory response.
• Direct stimulation causes airway epithelial cells to secrete pro-inflammatory cytokines (interleukin [IL] and tumor necrosis factor [TNF]).
• Neutrophils are recruited to the infected alveoli with immune cells and serum components.
• Capillary permeability increases, causing alveoli to fill with fluid, plasma proteins, and exudate, promoting pathogen proliferation.
• Fluid-filled alveoli prevent effective gas exchange, leading to hypoxia dependent on infection severity.

Influenza Epidemiology

• Influenza spreads by highly contagious infection.
• Outbreaks are tracked, recorded, and reported annually by the CDC.
• Localized outbreaks affecting more than the expected population are epidemics that occur usually every 1 to 3 years.
• Global or widespread outbreaks that affect more people than expected are pandemics.
• H1N1 in 2009 was the last influenza pandemic, with estimated deaths from 151,700 to 575,400, with high rates of morbidity and mortality.
• The CDC reported the highest influenza burden since the 2009 pandemic in the 2017-2018 season with an estimate of 48 million illnesses.
• Significant reduction influenza infection occurred from 2019-2020, the 2020-2021 season direct influenza-related deaths were markedly affected by mitigation strategies from the ongoing COVID-19 pandemic.

Risk Factors for Influenza

• Age is a risk factor with young children and older adults (under 2 and over 65) having immature or less active immune systems.
• Healthcare workers, caregivers, daycare providers, and educators are more likely to be infected with influenza.
• People in dormitories, military housing, and long-term care facilities are at a higher risk.
• A compromised immune system with malignancies treated with chemotherapy, transplant recipients, HIV/AIDS with low CD4+ counts are considered risk factors
• Chronic illnesses are risk factors such as diabetes, renal failure, asthma, and cardiac/respiratory diseases are more likely to develop serious complications.
• Pregnancy, considering pregnancy or recently postpartum pose a greater risk for severe viral pneumonia and a higher mortality rate.

Influenza Pathophysiology

• Human influenza viruses are designated as types A, B, and C.
• Influenza A viruses are divided into subtypes based on hemagglutinin (H) and neuraminidase (N) differences.
• Influenza types A and B are responsible for respiratory illness epidemics mostly in winter with increased hospitalizations and deaths.
• Influenza A causes the most severe outbreaks due to frequent mutation of H and N antigens.
• New emerging influenza viruses contributing to pandemics are caused by seasonal mutations of the viruses.
• Mutation in the influenza allows the viruses to evade the host's immune system.
• Hantavirus, metapneumoviruses, and coronavirus (SARS) are other identified pathogens.
• Control efforts largely focus on influenza types A and B.
• Influenza C causes very mild illness or no symptoms, with no major public health concerns unlike influenza A and B.
• The primary event in influenza infection involves the aerosolization of small droplets (less than 5 µm) from sneezing or coughing or by direct contact with fomites from those who are infected.
• Infected cells reproduces for 4 to 6 hours once deposited in the epithelial cells of the upper respiratory tract and spreads throughout the respiratory tract.
• Incubation period is 18 to 72 hours to develop symptoms then illness severity depends on the virus shed and the number of respiratory cells that are affected.
• Individuals are infectious for up to 7 to 10 days and virus shedding usually ends 2 to 5 days after symptoms appear.

Clinical Manifestations of Influenza and Interprofessional Management

• Clinical manifestations of the flu are more severe than a cold with a rapid onset.
• Indications such as fever, headache, sore throat, severe nasal congestion, cough, myalgia/muscle aches, malaise, and fatigue are common.
• Gold standard identifies influenza infection by sampling respiratory secretions for viral culture however viral cultures take up to 10 days to provide confirmation.
• Emergency departments and outpatient clinics use rapid influenza diagnostic tests (RIDTs).
• An influenza virus infection is identified in less than 30 minutes via nasopharyngeal/throat swab or nasal washings/aspirate.
• Clinicans should not make a diagnosis from RIDT results, and should consider patient symptoms, history, and clinical judgment when administering diagnostic tests.
• Circulating antibodies can be detected in the blood after 2 weeks of initial infection with specific laboratory tests (hemagglutination inhibition, complement-fixation, and enzyme-linked immunosorbent assay).
• Influenza illness is mainly prevented by annual vaccination.
• Inactivated influenza viruses from previous outbreaks provide up to 80% protection
• Vaccines are reformulated annually to match mutations in the HA protein in circulating viral strains.
• Vaccinations can cause fever, and soreness at the injection site, and those with egg allergies shouldn't receive this specific vaccine which contains an inactive ingredient of egg protein. Alternative forms of vaccine are available.
• Vaccination times are typically done during fall.
• Mild influenza illnesses are treated toward symptom relief from adequate fluid intake to avoid dehydration, and rest
• Significant antiviral medications are available for serious forms of influenza or widespread local outbreaks, for prophylaxis or treatment.
• Antiviral medications' effects aid toward viral replication and are not a ‘cure’ for the flu
• Antiviral medications should be initiated within 24 to 48 hours of symptom onset.

Medication Details

• Neuraminidase inhibitors like Zanamivir inhaled (Relenza), Oseltamivir (Tamiflu), and Peramivir (Rapivab) are Antiviral medications for Influenza A/B that binds to the active site of neuraminidase protein and prevent viral escape from host cell.
  • Monitor for onset of worsening respiratory status with underlying airway disease (dyspnea, wheezing, coughing) and skin reactions (rash, pruritus, urticaria), Agitation, delirium, and hallucinations.
  • It can be administered one-time through IV dose administration during pregnancy and breastfeeding.
• Baloxavir (Xofluza) is an Endonuclease inhibitor Influenza A/B that inhibits virus cap-dependent endonuclease activity that prevents viral replication.
  • Monitor for development of angioedema and blood in emesis or stool, and is contraindicated for pregnancy and breastfeeding.
• Rimantadine (Flumadine) is an RNA synthesis inhibitor Influenza A and inhibits uncoating of viral RNA in infected cells, preventing viral replication.
  • Monitor for onset of new seizures/seizure-like activity, tremors, and gait disturbances, neuropsychiatric events, palpitations or irregular heartbeat and is not recommended for use in pregnancy and breastfeeding.

Complications and Nursing Management

• Primary influenza viral pneumonia is the least common but most severe complication and occurs more frequently in individuals over 65.
• It is marked by cardiovascular compromise and progressive shortness of breath that may be visibly blood-streaked
• The frequent bacterial organisms linked to secondary pneumonia are Streptococcus pneumoniae, Staphylococcus aureus, and Haemophilus influenzae. This Classical presence presents an improvement in viral symptoms from purulent nasal and tracheal secretions.
• Common manifestations observed are the result of the inflammatory response from the influenza once the viral has invaded the respiratory epithelium.
• Interventions include assessments like oxygen satruation, breath sounds, Arterial blood gases and actions such as initiate appropriate isolation precautions and administer humidified supplemental oxygen.
• Teach patients measures like Practicing good hand hygiene, emphasizing limit contact with others for 10 days after symptoms, or 24 hrs after a fever to avoid infections.

Covid-19

• Symptoms for Covid-19 can range from Asymptomatic, and Mild to Severe.
• Individuals with Covid-19 or respiratory symptoms are recommended to self-isolate for 5 to 10 days
• All New respiratory symptoms should be treated as COVID-19 with consideration to contact with those who are sick, and travel to known hot spots
• The Gold Standard for diagnosis is Reverse Transcriptase where samples are obtained by a nasopharyngeal swab. Tests are performed in 24 to 36 intervals to increase confidence in the results.
• In two large cohort studies during the COVID-19 pandemic, patients of color were found to have three times the frequency of occult hypoxemia not detected by pulse oximetry but demonstrated on arterial blood gas sampling.

Longterm Care for Covid-19

• The CDC has many public health guidelines to reduce Community spread.
• The most preventive strategy to curtail the pandemic is deemed to be vaccination.
• Isolate and initiate airborne, contact, and droplet isolation, and continuously monitor for patients with severe Covid-19 and respiratory compromise.
• Manage patients with high or low oxygen saturation appropriately and treat with the safest known medication
• Covid 19 can lead to long term side effects that can last for months and are defined as ”post-COVID syndrome” and "long COVID.”

Pneumonia

• Pneumonia can occur anytime in individuals of any age and affects 3 to 4 million recorded persons in the U.S
• The Key Risks include advanced age, smoking, and lung disease
• Key organisms include streptococcus pneumoniae, pseudomonas aeruginosa, staphylococcus aureus, and mycoplasma pneumoniae
• Manifestations can range from fever, tachynea and dyspnea to purulent sputum, hypertension, and dysrhythmias.

Diagnosis and Complications of Pneumonia

• Diagnoses is through imaging studies such as elevated WBC counts, c reactive protein, arterial blood gases, and sputum cultures
• Severe CAP can lead to bacterial pneumonia requiring hospitalization to treat.
• One such major problem is needing to prevent atelectasis in hospitalized patients
• Other complications include bacteremia and septic shock which require attention to detail
• Pneumonia can be a result of Aspiration, Community Acquired, hospital Aquired and Health Care Associated Pnuemonia

Tuberculosis

• Tuberculosis is an infection caused from mycobacterium tuberculosis which causes many to be exposed to such disease
• Drug-resistant is a high concern.
• Treatment entails a four-drug combination is recommended for 9 to 12 months.
• The testing involves a skin test also called Mantoux test, and laboratory testing such as sputum Immediate isolation is a priority when the infection is confirmed or expected, and those who move the patient need to wear appropriate Surgical Masks.