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ANPS020
March 28, 2012
PULMONARY VENTILATION
Maximum intrapulmonary pressure
-maximum straining, a dangerous activity, can increase range
--from -30 mmHg to +1—mmHg
Weight lifter breath out (exhale) as they life (expert pressure)
MODES OF BREATHING
Respiratory movements are classified by pattern of muscle activity into:
Quiet breathing (eupnea)
-involves active inhalation and passive exhalation
-diaphragmatic breathing or deep breathing
-costal breathing or shallow breathing
Forced Breathing (hyperpnea)
-involves inhalation and exhalation
-assisted by accessory muscle
-maximum levels occur in exhaustion
RESPIRATORY RATES AND VOLUMES
Respiratory system adapts to changing oxygen demands by varying:
-the number of breaths per minute (respiratory rate = f, 12-16)
-the volume of air moved per breath (tidal volume; 500ml) = VT
The respiratory minute volume = VE
-Amount of air moved per minute
-is calculated by f x VT = VE
-respiratory rate (per minute) x tidal volume
Anatomic Dead Space = VD
-Only a part of respiratory minute volume reaches alveolar exchange surfaces
-volume of air remaining in conducting passages in anatomic dead space
ALVEOLAR VENTILATION =VA
Amount of air reaching alveoli each minute
-remember dead space (air already in lung)
Calculated as:
-respiratory rate x (tidal volume – anatomic dead space
VA = f x (VT – VD)
DEFINITIONS
Resting tidal volume: Amount of air one can move in or out of lungs in single respiratory cycle (resting
conditions)
Expiratory reserve volume (ERV): amount of air one can voluntarily expel after completed normal
respiratory cycle]
Residual Volume: amount of air remaining in lungs after maximal exhalation (1200 males; 1100 females)
-Minimal volume – amount of air left if lungs collapsed
Inspiratory reserve volume (IRV): amount of air one can take in over and above tidal volume
Inspiratory capacity: tidal volume + inspiratory reserve volume
Functional residual capacity: amount of air remaining in lungs after a quiet respiratory cycle
Vial capacity: maximum amount of air one can into or out of lungs in a single respiratory cycle
Totally lung capacity: Total volume of lungs = vital capacity and residual capacity (avg = 6000ml males,
4200 females)
GAS EXCHANGE
How do you get oxygen from the air into your cells?
-principle of diffusion: high pressure to low pressure
-air is composed of many gases
-gases dissolve into liquids
Respiratory – Cardiovascular systems interact
-RBCs (in blood vessels) an carry O2
INTRODUCTION TO HAS EXCHANGE
Respiration refers to two integrated processes
-external respiration
--includes all processes involved in exchanging O2 and CO2 with the environment
*Movement of O2 from air to alveoli to blood (in lungs then system) to interstitium
-internal respiration
--Also called cellular respiration
--involves the uptake of O2 and production of the CO2 within individual cells
Movement of O2 from interstitum into cells
-Cellular respiration –use of O2 in the cells
BLOOD SUPPLE TO THE LUNGS
Blood supple to the lungs
-#1 Pulmonary artery: (deoxygenated blood)
-from the right ventricle
-follow the bronchial…tree to alveoli
#2 Bronchial arteries – capillaries
-provide oxygen and nutrients to tissues of conducting passageways of lung, CT and pleura
GAS EXCHANGE
Occurs between alveolar air and blood
Across the respiratory membrane (blood-air barrier)
Into plasma and then
Into hemoglobin
Depends on
-Diffusion of molecules between gas or liquid
-partial pressures of the gases
The Gas Laws:
Diffusion occurs in response to concentration gradients
Movement is high to low concentration
Rate of diffusion depends on physical principles or gas laws
GAS EXCHANGE
Composition of Air
Nitrogen s about 78.6%
Oxygen is about 20.9%
Water vapor is about 0.5%
Carbon dioxide is about 0.04%
Air in a container – has a pressure
All molecules in air contribute to the total pressure
--each gas has a partial pressure
--all partial pressures together add up to 760 mmHg
Dalton’s Law and Partial Pressure )abbreviate Px
Atmospheric pressure (760 mmHg)
-produced by air (gas) molecules bumping to the container wall
-more bumping = more pressure
Each gas contributes to the total pressure
-in proportion to its number of molecules (Dalton’s Law)...
Air: Nitrogen > Oxygen > Carbon Dioxide
Henry’s Law
When gas under pressure comes in contact with liquid (plasma0
-gas dissolves in liquid until equilibrium is reached
At a given temperature
-amount of a gas in solution is proportional to partial pressure of that gas
Gas Content
The actual amount of a gas in solution (at given partial pressure and temperature) depends on the
solubility of that gas in that particular liquid
Solubility in Blood Fluids (plasma)
CO2 is very soluble
O2 is less soluble
N2 has very low solubility
GAS EXCHANGE
Normal Partial Pressure
In pulmonary vein plasma (with O2)
P CO2 = 40mmHg
P O2 = 100 mmHg
P N2 =573mmHg
Diffusion and the Blood Air barrier
-direction and rate of diffusion of gases across the respiratory membrane is determined by different
partial pressures and solubilities
VARIABLES IN GAS EXCHANGE
Efficiency of gas exchange is due to:
Substantial differences in partial pressure across the respiratory membrane
-diffusion gradients required
Distances involved in gas exchange are short
O2 and CO2 is lipid soluble
Totally surface area is large
-more chances for diffusion
-need more walls – hence more surface area
Blood flow and airflow are coordinated
--blood takes O2 away from alveoli
GAS EXCHANGE
Ineffiencies in gas exchange may occur:
Substantial differences in partial pressure across the respiratory membrane
-skiing in Colorado (lower oxygen in mountains)
-receiving O2 in the hospital
Distances involved in gas exchange are short
-fibrosis (increased CT = increased wall thickness
O2 and CO2 are lipid soluble
-always true…
Total surface area is large
-emphysema – surface area is decreased
Blood flow and airflow are coordinated
-congestive heart failure
ALVEOLI TO BLOOD
O2 & CO2
Blood arriving in (to lungs) pulmonary arteries has
Low P O2
--*deoxygenated blood from the system; right side of the heart
High P CO2
The concentration gradient causes
O2 to enter blood
Co2 to leave blood
--* P O2 is high in alveolar space, P CO2 is low
Rapid exchange allows blood and alveolar air to reach equilibrium
GAS EXCHANGE
MIXING
Oxygenated blood mixes with deoxygenated blood form conducting passageways
Lowers the PPO2 of blood entering systemic circuit (drops to about 95 mmHg)
BLOD TO CELLS
Interstitial fluid
in blood
P O2 40 mmHg  = 95 mmHg
PCO2 45 mmHg  = 40 mmHg
Concentration gradient in peripheral capillaries is opposite of lungs
- O2 diffuses out of blood
- CO2 diffuses into blood
GAS EXCHANGE A PROBLEM
Gas pickup and delivery
Blood plasma cannot transport enough O2 or CO2 to meet physiological needs
GAS TRANSPORT: RBC
RBC with hemoglobin
-transports O2 and CO2 from, peripheral tissues
-Remove O2 and CO2 from plasma, allows gases to diffuse into blood
Blood (cells and plasma) carries O2
1. Dissolved in plasma
2. Attaché to heme groups in RBCs
Hb + O2 HbO2
GAS TRANSPORT: RBCS
Oxygen transport
O2 binds to iron ions in hemoglobin (Hb) molecules
-in a reversible
Each RBC has about 280 million Hb molecules
-each binds to four oxygen
Hemoglobin Saturation
The percentage of heme units in a hemoglobin molecule
-that contain bound oxygen