Respiratory System Review - Oxygen Supply and Demand Flashcards
Surfactant
reduces the amount of pressure needed to inflate the alveoli. Decreases surface tension
Anatomical deadspace
Nose to the bronchioles. only the conducting pathway and is it termed anatomic deadspace. Not involved in gas exchange
Where the trachea bifurcates
the carina or angle of louis
anything above it is the upper respiratory tract and anything below is the lower respiratory tract
which lung is more likely to have aspirate in it and why?
the right lung because the bronchi is shorter, fatter and less angled. also more likely for deep suction catheter or NG tubes to go into that side.
Blood supply
Pulmonary circulation (pulmonary arteries bring deoxygenated blood)
Bronchial circulation (supplies blood to the larger airways of the respiratory tract)
Normal tidal volume
500 mls
Three structures involved in ventilatory function
Thoracic cage
Pleura
Respiratory muscles
Thoracic cage
24 ribs (12 on each side)
Sternum
Pleura (2 layers)
Chest cavity is lined with parietal pleura and lungs are lined with visceral pleura these are joined and form a sac for the lungs.
Intrapleural space is the space between the layers. increases cohesion, faciliates chest expansion and lubrication.
how much fluid should be in the intrapleural space?
20-25 mls
Respiratory Muscles
Diaphragm
Intercostal muscles
Abdominal muscles
How is fluid drained from the intrapleural space
lymphatic circulation drains fluid from the intrapleural space. shouldnt have additional fluid. If we develop fluid its because there is deficiency in normal drainage.
what is it called when too much fluid accumulates in the pleural space
pleural effusion
what causes a pleural effusion
malignant cells blocking lymphatic drainage
imbalance between fluid pressures (intravascular and oncotic pressure) this occurs in HF and is an example of third-spacing. can’t be brought back into the vascular space
Which nerve innervates the diaphragm
the phrenic nerve. paralysis at or above C3 will mean the patient is reliant on mechanical ventilation.
Empyema
the presence of purulent fluid with bacterial infection
Pneumothorax
Air in the pleural space
Hemothorax
Blood in the pleural space
Empyema
Pneumothorax
Hemothorax
each of these conditions can lead to partial or complete collapse of the lung
ventilation involves
inspiration and expiration
inspiration is
active
expiration is
passive
Compliance
a measure of the elasticity of the lungs and the thorax
when compliance is decreased, inflation of the lungs is more difficult.
what conditions decreased lung complaince (3):
those that increase fluid in the lungs (pulmonary edema)
diseases that affect lung tissue and make it less elastic (pulmonary fibrosis)
conditions that restrict lung movement (pleural effusion)
how do O2 and CO2 move across the alveolar capillary membrane ?
diffusion
The ability of the lungs to properly oxygen arterial blood is determined by
Partial pressure of oxygen in arterial blood or PaO2 (the amount of O2 dissolved in the plasma)
Arterial oxygen saturation or SaO2 (amount of O2 bound to hemoglobin of how much is available)
Oxygen-Hemoglobin Dissociation Curve
Oxygen delivered to the tissues depends on the amount of oxygen transported to the tissues and the ease with which hemoglobin gives up hemoglobin onces it gets to the tissues. Affinity
Upper flat portion – large changes in PaO2 cause small changes in hemoglobin saturation. Large change in PaO2 before we see it in the pulse ox. For this reason, if the PaO2 drops from 100 to 60 the percentage of the SaO2 will only drop 7%. Also explains why a patient is considered adequately oxygenated when the PaO2 is > 60 mmHg. Increasing the PaO2 does little for the SaO2.
On the left side – as hemoglobin is desaturating, larger amounts of oxygen are released for tissue use. This is an important method to ensure adequate oxygen supply even if O2 delivery is compromised.
End Organ Perfusion Assessment: Brain
Level of consciousness is the most sensitive neurological assessment parameter for evaluating cerebral perfusion and oxygen supply
End Organ Perfusion Assessment: Heart
Signs of myocardial ischemia will alert us to imbalances in myocardial oxygen supply and demand. Anginal chest pain, SOB, and ECG changes provide clues to myocardial perfusion
End Organ Perfusion Assessment: Lungs
Inadequate pulmonary perfusion will result in poor gas exchange. decreased PaO2 and SaO2
End Organ Perfusion Assessment: Gut
Decreased gut function will result from poor gut perfusion. Decreased gut perfusion can result in decreased gut motility, abdominal pain, nausea, and vomiting.
End Organ Perfusion Assessment: Liver
The liver is responsible for many functions that are important to the body (metabolic, filtration, and storage). Changes in lab parameters related to these functions would alert us to decreased liver perfusion.
End Organ Perfusion Assessment: Kidneys
BUN and creatinine provide information regarding renal perfusion, as does the amount of urine being produced by the kidneys.
End Organ Perfusion Assessment: General tissue perfusion
Skin warmth, color, pulse strength, and capillary refill all provide indications of general tissue perfusion
Oxygen Supply: Arterial Oxygen Content
amount of oxygen that is present in the arterial blood when it leaves the lungs (PaO2)
Oxygen Supply: Hemoglobin
capacity of the blood to transport oxygen to the cells (hgb)
Oxygen Supply: Heart Function
Effectiveness of the pump that circulates the blood throughout the body
Oxygen Demand (3)
- Temperature
- Activity Level
- Stress (emotional and physiological)
Factors Affecting Oxygen Supply: Ventilation (4)
- PaCO2
- RR
- Tidal volume, vital capacity, functional residual capacity
- Work of breathing (resp muscle function, lung compliance, airway resistance)
Tidal Volume
The amount of air that moves in or out of the lungs with each inspiration and expiration
Vital Capacity
greatest volume of air that can be expelled from the lungs after taking the deepest possible breath
Functional Residual Capacity
The volume remaining in the lungs after a normal passive expiration - 3L
Work of Breathing 3 Factors that impact a patient’s capacity to increase their work of breathing
Respiratory Muscle Function
Lung compliance
Airway resistance
Respiratory Muscle Function
Neuromuscular function, spinal cord injuries, pts who cant expectorate
Lung compliance
the lungs ability to stretch and expand. Pulmonary fibrosis or COPD
Alveolar Gas Exchange
PaO2
V/Q mismatch
- alveoli ventilated?
- alveoli perfused?
Cardiac Output (CO)
Diffusion
V/Q mismatch
typically our lungs have a 1:1 ratio. We should be equally as well ventilated as we are perfused. The lung is receiving oxygen but doesn’t have blood flow or is receiving blood flow but doesn’t have oxygen.
where the mismatch is happening impacts the treatment we give
Diffusion
CO2 diffuses 20x more rapidly than O2
CO2 levels are significantly affected by ventilation
Driving pressure of CO2
CO2 monitor is a more accurate representation of oxygen than pulse ox. another vital sign of ventilation
Oxygen transport and Delivery Impacted By (2)
Hbg Level
Oxygen Hemoglobin Affinity
a) PH
b) CO2
c) Temperature
- lower the CO2, higher pH and low temperature - the higher the oxygen hemogloin affinity SHIFT TO THE LEFT
Higher Co2, lower pH, higher temperature (sepsis) - tissues get more oxygen. Lower afinity. This is a shift to the right.
Shift to the RIGHT
higher CO2
Higher temp
lower pH
tissues get more oxygen. lower affinity between oxygen and hemoglobin
Shift to the LEFT
Lower CO2
Lower temp
Higher pH
The higher the oxygen hemoglobin affinity.
Cardiac Output
Heart Rate x Stroke Volume
Stroke Volume (3)
Contractility - how effectively te heart pumps and can eject its full volume of blood
Preload - the filling time of the heart
Afterload: systemic vascular resistance. The pressure it has to pump against
Blood Pressure and HR
What is MAP?
Essentially reflects the diameter and elasticity of the blood vessels
MAP: influenced by CO. care about it because if its low it means we aren’t perfusing tissues properly. The definition of MAP is the average arterial pressure throughout one cardiac cycle, systole and diastole.
