NURS 2090 Lecture Notes - Central Chemoreceptors, Acute Respiratory Distress Syndrome, Cough

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Published on 16 Apr 2013
Dalhousie University
NURS 2090
Altered Ventilation and Diffusion
Respiratory Structures
Rate and volume of ventilation is regulated by:
1. Functioning respiratory control center (RCC): responds to chemical messages in the
body. Composed of neurons in the pons/medulla. It sends impulses to diaphragm,
muscles to contract/relax. (Constriction= Para, Dilation = Symp)
2. Lung receptors: Located in the epithelium/smooth muscle airways.
3. Chemoreceptors: detect gas exchange needs based on PaO2, PaCo2, pH levels.
Central chemoreceptors: near RCC, respond to pH changes in the CSF. Detects CO2
levels in the blood. (↑ CO2 = ↑ ventilation to expel CO2)
Peripheral chemorecepotrs: sensitive to O2 levels, located in aorta/carotid arteries.
( ↓ O2 = ↑ ventilation)
Alveolar type 1: provide structure and air
Alveolar type 2: lubricant that coats the
inner portion of the alveolus, promotes
easy expansion, repels fluid accumulation
** inflation would be impossible w/out it
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Ventilation: Process of moving air in/out of lungs
Involves both acquiring oxygen (inspiration) and removing carbon dioxide (expiration)
from the blood
Neuronal impulses are directed by lung receptors, which map the current state of
breathing and lung function
Uses the intercostal muscles, diaphragm, and sternocleidomastoid muscles
Breathing in to acquire oxygen
Unidirectional from high pressure to low pressure.
Chest cavity size changes to alter the pressure gradient
Neuronal stimulation/movement moves diaphragm down and out (reduces pressure inside
lungs to pull air in)
Removing carbon dioxide out of the body through the lungs
The diaphragm and external intercostal muscles relax
Lungs compress and increase the pressure inside the airways
Chest wall moves in and diaphragm moves upwards.
Inside pressure is more than atm pressure (so air moves OUT)
Measurement of Ventilation
1. Tidal volume (TV): the amount of air exhaled after passive inspiration (air in and out at
rest) ** 500 mL
2. Vital capacity (VC): max amount of air in/out of lungs with forced inhale/exhale
3. Forced capacity (FVC): amount exhaled during forced exhale
4. Forced expiratory volume in 1 second (FEV1): amount exhaled from lungs in 1 sec
5. Residual volume (RV): volume of air left in lungs after maximal expiration
6. Total lung capacity: total air in lungs when they are maximally expanded (VC+ RV)
Diffusion: Process of moving/exchanging O2/Co2 through membranes
Oxygen and carbon dioxide are exchanged at alveolar capillary junctions
Two major process occur:
Oxygen is trying to get to all the cells
Carbon dioxide is trying to escape the body through the lungs
Effectiveness depends on: Pressure (Co2, O2 in blood), Solubility (Co2 more soluble),
and Membranes (thickness/SA)
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Partial Pressure
The collision of oxygen and carbon dioxide creates pressure
Perfusion: Process of supplying oxygenated blood to lungs and organ systems via blood vessels
Respiration: Process in which cells in the body use O2 to make energy
Oxygen Diffusion and Transport
Oxyhemoglobin (HbO2): As PaCO2 ↑ oxygen dissociates from the plasma and connects
with hemoglobin molecules on RBC’s. Based on attraction to iron. When it is attached to
hemoglobin, it is not available to the cell.
Oxygen Saturation (SaO2): Attraction of hemoglobin continutes until the hemoglobin
molecules are completely saturated. It is NOT affected by blood volume.
Once saturation occurs, oxygen continues to diffuse and dissolve in the plasma, until the
partial pressures in arteries = that in the alveoli
Carbon Dioxide Diffusion and Transport
Dissolved in the plasma (10%)
Bound to hemoglobin (20%)
Diffused into the red blood cell as bicarbonate (70%): converted to either carbonic
acid, bicarbonate ions (which helps regulate pH)
Diffusing Capacity
The measurement of carbon monoxide, oxygen, or nitric oxide transfer from inspired gas
to pulmonary capillary blood and is reflective of the volume of a gas that diffuses through
the alveolar capillary membrane each minute.
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