Respiratory System

• The respiratory system allows for gas exchange, ventilation, and transportation of gases.

Key Processes

• Pulmonary ventilation involves the movement of air into and out of the lungs
• Pulmonary respiration is the exchange of O2 and CO2 between the lungs and blood
• O2 is transported from the lungs to the tissues
• CO2 is transported from tissues to the lungs
• Capillary gas exchange is the exchange of gases between the blood and tissues
• Oxygen utilization is the use of oxygen by cells to produce energy

Structure of the Respiratory System

• The respiratory system consists of the nose/nostrils, nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles, terminal bronchioles, respiratory bronchioles, and alveoli.
• The two zones of the respiratory system are the conductive zone and the respiratory zone

Conductive Zone

• Includes structures from the nose to the terminal bronchioles
• The conductive zone transports air
• There is no gas exchange in the conductive zone, therefore it is known as anatomical dead space
• Air reaches body temperature and 99.5% humidity as it reaches the lungs, protecting it from injury and maintaining core temperature
• Ciliated mucus membranes in the conductive zone filter incoming air, and smoke and pollutants can damage the cilia

Respiratory Zone

• The respiratory zone includes the respiratory bronchioles and alveoli
• Alveoli are the site of gas exchange and have a large surface area
• Capillaries that surround the alveoli permit efficient exchange of O2 from alveoli into the bloodstream.
• High-altitude pulmonary edema (HAPE) is when fluid accumulates in the lungs, impairing gas exchange

Structure: Alveoli

• Gas exchange occurs in the alveoli to optimize diffusion
• The respiratory membrane is very thin (0.3 micrometers)
• Two cell membranes compose alveoli: alveolar and capillary epithelium

Oxygen Journey

• After gas exchange in the alveoli, oxygen travels through the pulmonary veins
• Blood is then transported to the left atrium, through the bicuspid valve to the the left ventricle
• Oxygenated blood is pumped through the aorta then enters systemic circulation

Mechanics of Ventilation

• Airflow equals the pressure gradient divided by resistance, measured in L/min

Airflow Resistance & The Conduction Zone

• Nasal strips may be used during exercise but are not effective, as nose is not limiting ability to get air, due to mouth breathing
• Changes in airway resistance can be problematic, because muscles work harder to get the same amount of air

Asthma

• Airways become narrowed and inflamed by triggers
• Airway resistance increases as a result
• Medication can return resistance to normal in asthmatic patients

Exercise-Induced Bronchoconstriction (EIB)

• During exercise, the rate and depth of breathing increases as does bronchodilation
• It can cause a narrowing of the airway
• EIB can occur in those with or without asthma, and 30-70% of elite athletes experience EIB
• Endurance, aquatic and cold weather athletes are more prone to be affected
• EIB treatment: warm-up, medication, avoiding cold air, and cool-down

Testing

• Pulmonary function testing determines if an individuals has a respiratory disorder

Alveolar and Atmospheric Pressure

• Atmospheric pressure is constant at the same altitude, so the lung's pressure must be changed to create airflow

Boyle's Law

• The pressure of gas is inversely related to its volume
• Low pressure equals high volume
• High pressure equals low volume

Lung capacity

• Increasing the volume of the thoracic cavity decreases intrapulmonic pressure, resulting in air rushing into the lungs, or inspiration
• Decreasing the volume of the thoracic cavity increases interpulmonic pressure, resulting in air rushing out of the lungs, or expiration

Interpulmonic Pressure= Pressure in the Lungs

• Inhalation and exhalation generate a pressure difference between the lungs and the external environment
• Gas flows from high concentration to low concentration
• Intrapulmonic pressure is less than atmospheric pressure during inhalation
• Intrapulmonic pressure is more than atmospheric pressure during exhalation
• At rest, there is no movement
• PAtm and PIntrapulmonic are the same, 760mmHg
• Air moves from high to low pressure

Inspiration

• The diaphragm contracts and flattens
• This action increases volume
• Diaphragm creates most of this effort during rest
• During exercise, external intercostals and accessory muscles contract
• They pull ribs up and out
• Increasing volume and decreasing pressure
• Accessory muscles like Sternocleidomastoid and scalenes, move ribs up and out
• There is a resulting increase in Volume and decreased intrapulmonic pressure, resulting in airflow
• Diaphragm, external intercostals and accessory muscles contract during inspiration
• The chest cavity expands and lung volume goes up
• Lung volume goes down
• This creates a pressure gradient
• Air flows into the lungs

Expiration

• Inspiratory muscles and the diaphragm relax
• The chest cavity recoils reducing volume
• This increases the lung pressure
• Air flows out
• During exercise expiration is active
• Rectus abdominus, and internal obliques contract, to pull the ribs down
• This Reduces lung volume
• Incremental rise in pressure causes air flows out

Pleura

• Change from chest cavity translates to lungs through the pleurae
• Lungs are bound by visceral pleura and chest cavity is bound by parietal pleura
• Pleural fluid is lubrication, fills space in between the layers, creating intrapleural pressure
• This allows smooth gliding with lung movement and keeps lungs inflated
• Intrapleural pressure is always lower than pressure then in the lungs
• A pneumothorax affects this intrapleural pressure

Pulmonary Ventilation

• Volume of air entering and exiting lungs over given time, in L/min
• AKA minute ventilation
• Equal to tidal volume x breathing rate
• Minute ventilation increases through mild, moderate, and heavy exercise with higher max ventilation for athelites

Alveolar Ventilation

• This is the amount of air that actually reaches the alveoli
• Air remains in the conducting zone (dead space) so doesn't partake in gas exchange
• Alevolar Ventilation = Tidal Volume x Breathing Rate + Dead Space

Gas Exchange

• Adequate alveolar ventilation allows for proper gas exchange
• At the Lungs replenish O2, remove CO@

Driving Factors for Pulmonary Diffusion

• Thickness, surface area and pressure gradient

Fick's Law of Diffusion

• Surface area, diffusion coefficient, pressure difference
• Divded by membrane thickness

Emphysema

• Destroys the alveoli to impair gas exchange

Partial Pressure

• Gasses exert pressure on everything they touch
• Gasses exert forces on a surface which effects barometric pressure
• Partialpressure calculated by Total pressure x fraction (or percentage) of the gas
• Atmospheric gases are a mixture of N2, O2, CO2.
• Atmospheric pressure equals 760 mmHg at sea level
  • The fractions (%) of O2, CO2, and nitrogen stays the same at high altitude, but the atmospheric pressure does not

Alveoli Values at Rest

• PACO2 ~ 40 mmHg
• PAO2 ~ 105 mmHg
• PAH20 ~ 47 mmHg
• PAN2 ~ 568 mmHg
• PAtotal 760 mmHg

Inspiration

• This results in a move from High to low pressure with
• Alveolar Alveolar PO2 = 105 mmHg
• Pulmonary arterial P02 = 40 mmHg
  • This results in Alveolar air mixes with air in the lungs

Oxygen Diffusion

• Oxygen diffuses down a pressure gradient until equilibrium is reached
• Oxygen diffuses from the lung to the blood because of the pressure gradient

High Altitude

% doesn't change, barometric pressure goes down

Exchange

• This occurs due to a partial pressure different between muscle and tissue
• O2 delivered equals cardiac output X arterial-venous O2 difference

Hemoglobin & transport

• Oxygen dissolved in the blood accounts for 1.5-3% of all transport, which is responsible for the partial pressure of O2 in blood, and
• Hemoglobin binds iron to account for 97-98.5% of the total -Hemoglobin contains iron which binds heme and protein
  • Each molecule has 4 identical subunits that contain Fe and bind/ relese

Hb and Saturation & Dalton

• O2 saturation dependent on PO2 in the blood in healthy people about 97/98%
• Except: Exercise Induced Arterial hypoxemia likely ineffective gas exchange at high intensities

Function of myoglobin

• functions as an oxygen reserve during exercise

Carbon Monoxide

• Is deadly because CO attracts hemoglobin instead of O2

Oxygen Dissociation Curve

• Hb Affinity is based on where it is ->
• Lungs- oxygen need associate
• Body oxyen needs dissociation
• Hb needs to bind O2 in an easy switch dependening on location with low affinity with oxygen at the muscles and high saturation
• This is aided by the H+, K+, C02, PH

Factors That Effect the Curve

• Temp
• PH
• C02

Bohr Effect

• ↑ H+ = ↓ pH= ↑ acidity will decrease the affintiry, facilitate unloading shift
• When high acidity releases Hemoglobin, there is a Right shift
• Hemoglobin can then act as a buffer by binding This allows an increase in PO to also Increase pressure

Carbon Dioxide

• An incremental risein levels can lead to increased affinity during unloading
• This leads to an incrimental right shift

Carbaminohemoglobin

• O2 +Hb (decreases affinity for CO2 (Haldane effect)

Carbon BiOxide Tranport

7 % -10% is dissolved into plasma to go to hemoglobin and redbloodcells

• Not in competition 70 % converted back to bicarbonate to bind in high CO2 areas
• this helps push gas back to lungs 2 H will lead lower for PH and then facilitate lower hemoglobin which the body acts as a buffer

What about exercise

The body is not always as active but still creates a partial gradient

• The body to help maintain alvealor ventilation to still compensate with low levels

Control

• Respatory control helps keep track of COs and acidity to stimulate with muscles Also important to note what is in the diaphram through the pont

Potassium & Ventilation

• During exercise k+ is increased , this will effect C02 to be strongular
• Also there is a high change in sensitivity to messgae from cortex
• And what muscle and hypothalmis are sending Overall we need change for 02 or we will not make benefits

Ventilation Response to Submaximal Exercise

3 key phases Phase1. Prociptors - fast rate up which causes to much oxygen 2 cortex feeds back with precepors in order 4 phase 3- the fine tuning to meet needs

Exercise

• For 02 that have been satisfied , and also an enviro level During this there is also incremental increase and deacrese but more will need at top