OPTA 222 (respiratory)
Conducting Airways
The air we breathe is warmed, filtered and moistened as it moves through the conducting airways: nasal passages, mouth, pharynx, larynx, bronchi, bronchioles
Heat is transferred to flowing air from blood flowing through the walls of the respiratory passages.
Mucociliary system traps, dust, dirt and bacteria but is not as effective during drier conditions and during the winter months.
Moisture is drawn from mucus membranes to moisten air we breath (we use approx 500mL of water/day to do so)
Increased amount of air flow from increased respiratory rate can make it difficult to moisten all ingoing air, leading to thicker secretions.
Physiology
Alveoli is the primary site for gas exchange.
Type I alveolar cells: occupy 95% of the surface of the alveoli. Cannot divide. Main cells for gas exchange.
Type II alveolar cells: occupy 5% of surface area bc different shape than type I. Capable of division. Synthesize surfactant, assist in repair of type I.
Synthesize pulmonary surfactant.
What is surfactant?
Pulmonary vasculature and lymphatic supply
- Lungs have pulmonary and bronchial blood supply
Pulmonary is how blood is oxygenated for the rest of the body
Bronchial supply supplies the lungs themselves
- As blood moves through lungs, O2 is picked up by capillaries and oxygenated blood is returned to L side of the heart to be pumped out to systemic circulation
- The lymphatic system parallels the dual blood supply to allow drainage from surface of the lung and interior down to the bronchioles
Lung Compliace
Refers to the ease with which lungs can be inflated at a given pressure change. It takes more pressure to move air into a non compliant lung than it would a compliant lung.
Determined by elastin and collagen fibres. Lung diseases like pulmonary fibrosis can make these fibres less mobile. Cellular damage in emphysema can make it more difficult for cells to recoil.
Surfactant
soapy type substance allows for better expansion of aveoli = more surface area for gas exchange
Respiratory centre and regulation of breathing
Has involuntary and voluntary components
- Automatic portion is controlled by input from chemoreceptors and lung receptors
- Chemoreceptors: Monitor blood levels of CO2, pH and O2, Lung receptors monitor breathing patterns and lung function
- Voluntary regulation: Breathing, singing, blowing
Cough reflex
Protects lungs from accumulation of secretions and from irritating substances entering lungs
- Initiated by receptors in the tracheobronchial wall.
- Requires rapid inspiration of large volume of air (usually 2.5L) followed by rapid closure of the glottis and forceful contraction of the abdominal and expiratory muscles
- Greatly increases expulsion pressures
- Reflex is impaired for those with weak respiratory or abdominal muscles
Dyspnea
Shortness of breath
Difficult to quantify bc describes a person’s perception of the sensation.
Often in variety of acute or chronic states:
- Pneumonia
- Asthma
- Emphysema
- Heart disease
- Pulmonary congestion
Treatment depends on the cause
- Oxygen therapy
- Reducing fluid retention for pulmonary edema
- Decrease anxiety
- Energy conservation breathing retraining
Upper respiratory tract
Nose, oropharynx and larynx
Lower respiratory tract
lower airways and lungs
Respiratory Infections
Viruses are most common cause
- Large range of severity
From self-limiting cold to life threatening pneumonia
- Viral infections can damage bronchial epithelium and obstruct airways leading to a secondary bacterial infection
- Respiratory infections, in addition to viruses and bacteria, can also be caused by mycobacteria and fungi
Common cold
Viral infection of upper respiratory tract (URT)
- Adults have 1-3 URT infections/year
- Infants up to 11 episodes/year
- Preschool up to 8 episodes/year
- School age 4 episodes/year
Mucous membranes of URT become red, swollen and bathed in secretions
Involvement of pharynx and larynx causes sore throat and hoarseness, can be further irritated by post nasal drip
Children can present with otitis media
common cold part 2
Self limiting in 7-10 days
Associated with a number of viruses
80% caused by rhinoviruses
Other pathogens include:
- Parainfluenza
- Respiratory syncytial
- Coronavirus
- Adenovirus
Factors affecting what virus infects person and what symptoms they get are: Age, Prior exposure
One type of virus can have many different serotypes (strain)
- People can develop immunity to a certain type of serotype but not ALL serotypes
Most highly contagious period is first 3 days and incubation period up to 5 days
Inflenza: One of the most common causes of URT infections
- Each year approx 10-20% of canadians get influenza and 4000 persons die each year from influenza related illness
- Rates of infection are highest among children
- Rates of serious illness and death are highest among immunocompromised children and persons over age 65
- Similar to viral infections, influenza is more contagious than bacterial respiratory tract infections: Droplet transmission, Young children most likely to spread infection, Virus shedding can occur both before and after infectious symptoms are present
Influenza viruses can cause 3 types of infections
- Uncomplicated upper respiratory tract infections
- Viral pneumonia
- Respiratory viral infection followed by a bacterial infection
Virus first infects upper airway, targeting and killing certain types of cells. This leaves gaping holes between the underlying basal cells and allows extracellular fluid to escape- this is what causes runny nose symptom.
Can spread to lower respiratory tract infection and can shed the bronchial and alveolar cells.
- This decreases the defenses of the lungs, making them more susceptible to bacterial infection, this is how a viral infection can turn bacterial
Pnuemonias caused by
- Inflammation of the parenchymal structures of the lungs such as alveoli and bronchioles.
Common cause of death from infectious disease.
Can be caused by:
-Virus
-Bacteria
-Funghi
-Inhalation of irritating fumes
-Aspiration of gastric contents
Pneumonias Commonly classified by:
Type
- Typical: caused by bacteria that multiply extracellularly
- Atypical: caused by viral and mycoplasma infections
Distribution of the infection (lobar or bronchial)
Setting in which it was acquired (community or hospital)
Tuberculosis
World’s largest cause of death from a single infectious agent (mycobacterium tuberculosis)
Outer waxy capsule allows them to be more resistant to destruction. Spread by inhaling mycobacterium droplet nuclei which can remain suspended in the air and recirculated
- Locations with overcrowding make it more likely to spread
- Complicated immune response
- Immune response is complicated and different in persons with a primary infection vs. a secondary infection.
- Primary infection: Immune cells wall off bacteria and in the process cause destruction of lung tissue, Takes 3-6 weeks to activate proper immune response, The process that walls off the bacteria can allow some bacteria to remain viable for years
- Secondary infection: Reinfection from inhaled droplet bacteria or Reactivation of previous infection
- Skin test
Fungal Infections
- Classified as yeasts and molds
- Virulent fungi can live in nature, soil or decaying organic matter
- Form infections that create spores that enter through the respiratory system
- Many fungal infections can be asymptomatic, can be fatal with heavy exposure
- Immunocompromised persons are more susceptible and can require lifelong treatment (ex. Person with HIV)
Hemothorax
- Blood in the pleural cavity
- Could be result of chest injury, malignancies
- Rupture of a vessel
- Complication of chest surgery
Pneumothorax
- Presence of air in the pleural space
- Collapse of a lung
- Can be a result of injury or can occur without known cause
Atelectasis
Incomplete expansion of a lung (or portion of a lung)
Can be caused by:
Airway obstruction (mucus plug, tumor)
Lung compression
Pleural effusion
Decreased surfactant
Can be present at birth or develop later in life
signs/symptoms:
Tachypnea
Tachycardia
Dyspnea
Cyanosis
Signs of hypoxemia
Decreased chest expansion
Treatment depends on severity but can include:
Ambulation, deep breathing, positioning
Asthma
Chronic inflammatory airway disorder
signs/symptoms:
Wheezing
shortness of breath
Chest tightness
Coughing
Triggers:
Allergies
Irritants
Infection
exercise
plural infusion
swelling around the lungs
asthma
in asthma multiple factor ( both ealy and late in the attack)
can lead to bronchospasm making an asthma attack difficult to control without treatment