Oxygenation

upper airway and function

• nose, pharynx, larynx, epilogitts

• warm, filter, humidify air

Lower airway and function

• tracheobronchial tree (trachea, right and left mainstem, segmental bronchi, terminal bronchioles)

• Lower respiratory tract: trachea divides into bronchi ending in terminal bronchioles with alveoli sacs at the end

• Function: conduction of air, mucociliary clearance, makes surfactant

what supports the trachea

cartilage rings

what supports the bronchioles

smooth muscle

how can the respiratory system be divided functionally

1. the conducting airway = air moves as it passes between atmosphere and the lungs

2. respiratory tissues is where gas exchange occurs

Where does gas exchange occur

terminal bronchioles in the alveoli

Pulmonary defense mechanisms

1. protective structures - hairs and cilia trap and remove foreign particles

2. mucosal lining - warms and humidifies air

3. irritant receptors - recognize injurious agents and respond by sneezing or coughing

4. Immune protections - immune coating in the mucosa and macrophages in alveoli that ingest and remove bacteria by phagocytosis

5. Muscles - intercostal and chest muscles protect against injury

Type 1 alveolar cells

• thin squamous

• provide structure

• facilitate gas exchange

Type II alveolar cells

• large cuboidal 

• secretes surfactant

Ventilation

inspiration and expiration

Respiration

gas exchange between atmospheric air in the alveoli and blood in the capillaries

How do the muscles move during inspiration

diaphragm contracts down, intercostal muscles contract and pull in, ribs are lifted and sternum pushes outward

How do the muscles move during expiration

diaphragm moves back up, sternum and ribs drop down

Factors that affect ventilation

1. drive to breathe (neural impulse): the brainstem sends neural impulses to the diaphragm, intercostal muscles, etc to contract or relax

2. Lung compliance: ease at which lungs can be inflated

3. Chemoreceptors detect gas exchange based on PaO2 and PaCO2 and pH levels

4. Airway resistance

5. musculature

Factors affecting respiration

1. Oxygen saturation: amount of oxyhemoglobin

2. Oxygen-carrying capacity: max amount of O2 that blood can carry

3. diffusing capactiy: amount of O2, cabon monoxide, and nitric oxide that transfer from inspired gas to pulmonary capillary blood & it reflects the volume of gas that diffuses through alveolar capillary membrane each minute

Oxyhemoglobin

• oxygen binds to hemoglobin and is attracted based on the iron

• 4 O2 molecules is 100% saturated

• Once saturation occurs, O2 continues to diffuse until PO2 in arteries equals the PO2 in the alveoli 

Oxygen hemoglobin dissociation curve

• graphical representation of relationship between amount of oxgeyn bound to hemoglobin and the partial pressure of O2 in the blood

• Curve is sigmoidal with steep slope at low partial pressures of O2 and more gradual with higher partial pressures

What causes impaired ventilation?

• compression or narrowing of airways = increases airway resistance. Caused by edema, exudate, foreign body accumulation

• Disruption of neuronal transmission from sedation or drug overdose 

Ventilation Perfusion Ratio

• defined as the ratio of the amount of air reaching the alveoli to the amount of blood reaching the alveoli

• Deadspace: adequate ventilation but poor perfusion. There is oxygen ready to be delivered, but no blood is there to pick it up.

• Shunt: adequate perfusion but poor ventialtion. There is blood but no oxygen to pick up

• VQ mismatch leads to hypoxemia and hypercapnia

What is diffusion and what does it depend on

• Transfer of O2 and CO2 across ACJ

• depends on: solubility and partial pressure of gas and surface area and thickness of the membrane

Diagnostic tests

• ABG: determines acid base imbalance

• pulse oximetry: measures oxygen saturation

• bronchoscopy: direct visualization of bronchioles

• VQ scan: detects resaon for VQ mismatch by using computer iaging to visualize lungs

Mild assessment findings of altered ventilation and diffusion

cough, fatigue, irritability

severe assessment findings of altered ventilation and diffusion

• hypoxemia leading to hypoxia

• Early cues: dyspnea, VS changes, pallor, anxiety, diffusion

• Late cues: headache, chest pain, cyanosis, weakness, decreased LOC

• Chronic changes: clubbing, barrel chest