Pulm Content; Final Exam Flashcards
Atmospheric Pressure is a Result of What?
Gravity and the weight of the atmosphere between us and outer-space
Sea level: 760mmHg
Outer Space: 0mmHg
What is the highest point of altitude on earth?
How do hikers acclimatize to this?
What are short-term & long-term compensation methods?
Highest point of altitude on Earth
Summit of Mount Everest: ~9km (8848m)
PB: 243mmHg
PIO2: 43.1mmHg
* This PO2 can typically only be tolerated by a human for ~2 hours.
* Fractional concentration of atmospheric pressures should remain the same.
* PIH2O will remain 47mmHg
- Base camps are used to acclimatize hikers to the high altitude
- Hyperventilation typically occurs as a short-term compensation to the high altitude
- After a few days: EPO is increased in response to hypoxia –> increases HCT in order to facilitate increased oxygen carrying capacity
Barometric pressure is the amount of pressure available to….?
Push oxygen and other inspired gases into the blood
What is different about the body if a person has grown up in a high-altitude area?
- Increased surface area in the lungs as a function of an increased number of alveoli
- More surface area for gas exchange
How does descending in altitude into a body of water affect the body?
What is the make-up of the O2 tank used in low altitudes?
- Descending in altitude into a body of water significantly magnifies the amount of atmospheric pressure that is felt
- Descending 500ft below sea level causes the atmospheric pressure to be as high as 16x the PB at sea level
- If the body is subjected to this high of a pressure, the source you are breathing from needs to be highly pressurized as well
- Typically the contents of the tank is the same composition as air. Eliminating the N2 would eliminate the risk associated with sudden decompression; however, O2 is explosive
Lowest Altitude on Earth?
Death valley
Sudden Decompression
- The gases in the blood increase in proportion to the increase in atmospheric pressure
- N2 partial pressure is the main concern in people who are diving —> if there is a sudden decompression of the body, the pressures will adjust by the gas coming out of solution
- This is essentially boiling your blood. Taking N2 in a liquid form in the blood and releasing it in gas form
- This causes air emboli to form
The best way to avoid this is to decompress gradually.
Arnold Schwarzennegar Movie- Total Recall
Altitude Sickness & Mt. Everest
- Some people are genetically prone to altitude sickness
- Typically Camp #3 is when people discover whether they can handle the altitude or not
-PB: 317mmHg
-PIO2: 56.5mmHg
Standard vs military, hyperbaric rooms? Benefits? Michael Jackson?
Hyperbaric Chamber Therapy
Standard Hyperbaric Chamber
* Can simulate up to 3x ATM
* Usually seen in large, academic hospitals
* Single or multiperson
* Can be mobile
Military Hyperbaric Chambers
* Expensive
* Dangerous
* Can significantly increase the ATM pressure
Oil rigs have hyperbaric “rooms” so that people that are constantly diving very deep for work can live in a high-pressure environment
Benefits
* Decompression treatment
* Wound healing
Michael Jackson had one in his house
How do we increase dissolved PaO2?
- O2 is relatively insoluble
- Travels via Hb so that it doesn’t have to dissolve in solution
- In order to increase PaO2 –> PAO2 must be increased by:
- Increase FIO2
- Increase ATM (hyperbaric chamber) - Any of the additional O2 being pushed into the blood will have to be in the dissolved form
Why do we give a higher FIO2 in the OR?
General anesthetics interfere with normal physiologic functions such as HPV and airway reactivity
Dangerous Oxygen Molecules
O2- Superoxide
- O2 molecule with an extra, unpaired e- that is very reactive and degrade many different compounds
OONO- Peroxynitrite
- “Oh no!”
- Very bad. Interacts with and mutates/destroys DNA (Cancer)
- Need Superoxide & NO in large amounts to form this compound
H2O2 Hydrogen Peroxide
-ROS used as an aseptic cleaning substance
NO Nitric Oxide
- Toxic if there is a high concentration of NO in the presence of other dangerous oxygen molecules
How are dangerous oxygen molecules used and contained in the body?
Macrophages and immune killer cells can release these compounds in order to destroy harmful things in the body
Superoxide dismutase
- Degrades superoxide
Peroxidases
- Degrades H2O2
Catalases
- Can degrade or form H2O2
Acetylcysteines
- Excellent at scavenging excess ROS
- N-Acetylcysteine used for APAP overdose
- Can get OTC, FDA wants to regulate it because it’s effective
What was this used for? And how does it work?
- Postive pressure valve
- Negative pressure valve
- Leather Diaphragm
- Used heavily for Polio victims in the 1960’s.
- Polio destroys the ability of the CNS to communicate with skeletal muscles
- Can be used long-term
How does it work?
- Leather diaphragm is fitted around the patient’s neck or upper body in order to create a seal between the iron-lung and the environment
- Leather diaphragm on the distal end pulls the diaphragm outward causing the pressure inside the iron-lung to become negative/reduced —> allowing for air to be pulled into the patient
Negative Pressure Breathing vs PPV
Negative pressure breathing
- Diaphragm contracts –> PPl is reduced –> outer lung is pulled closer to the chest wall bringing air into the lungs evenly
- Alveoli closest to superficial lung tissue will fill first
- Allows for deeper alveoli to fully-fill and stretch (mechanical stretch is important for surfactant)
PPV
- PP pushes air into the lungs
- Alveoli closest to the large airways fill first (deep alveoli)
- Deeper alveoli compress alveoli between the deep areas and the border of the lung
- Loss of mechanical stretch
Iron Lung Guy vs Christopher Reed
Irong Lung Guy
- Used the iron lung for 50+ years
- Became a lawyer while in the iron lung
- Had to source spare parts for the iron-lung when they wore out
- Not mobile, so inconvenient
Christopher Reed
- Did not live 50 years with the PPV (trach)
- Died from pulmonary complications
- Mobile, but not normal ventilation for the lung
Airplanes: Altitude & Pressurization
- Planes fly at high altitude (40,000ft) because the air is thinner and they better gas mileage
- Modern planes are pressurized to mimic the atmosphere of ~8,000ft
- Sick lungs, a sick right heart will be affected by this atmosphere
- 760mmHg
- 523mmHg
- 349mmHg
- 226mmHg
- 141mmHg
- 87mmHg
What happens if a plane depressurizes?
- O2 masks are connected to a container, once pulled from the container, an exothermic chemical reaction is set off (heat)
- Chemicals combine –> produce a higher concentration of oxygen
- Masks contain just enough O2 to keep you conscious until the pilot takes the plane down to a safer altitude
- This is not sufficient O2 for the pilots. They keep their own tanks with 100% O2
- With sudden depressurization at an altitude of 40,000ft, the PO2 of the air in the airplane will become 29mmHg. Because this is lower than the PO2 in the lungs, gas exchange will begin to work in reverse —> O2 leaves the lungs to move into the environment
The acidity of a solution is dependent on…
⍺ represents acidity
⍺ H+
- the acidity of a solution is dependent on hydrogen ion activity (directly related to concentration)
Volatile, Non-Volatile, & Pathologic Acids in the body
Volatile Acids
Means this acid can take the form of a gas
- CO2
Non-Volatile Acids
Because these are non-volatile, they cannot turn into a gas (CO2) and be removed from the body. Must be removed by the kidney or liver
- Typically formed from dietary protein metabolism
- Sulfuric acid (sulfate)
- HCl
- Lactic acid (lactate)
- Phosphoric acid (phosphate)
Pathologic Acids
- Acetoacedic acid (acetone):
- produced in poorly managed DM
- produced by the liver after large amount of ETOH metabolism
- Butryic acid:
- produced in poorly managed DM
Why is CO2 considered a weak acid?
- CO2 & H2CO3 are considered weak acids in the body
- CO2 can combine with H2O to form H2CO3
- CO2 +H2O ⇌ H2CO3
CO2 is considered a weak acid because:
- H2O & CO2 are largely present throughout the body, meaning that CO2 can rapidly combine with H2O to form H2CO3
- Since CO₂ indirectly causes an increase in free H⁺ ions, it’s effectively considered an acid
CO2:H2CO3 Ratio –> 1000:1
Why Does CO₂ ≈ H₂CO₃ in Physiology?
Extremely Fast Equilibrium:
- The enzyme carbonic anhydrase, especially abundant in red blood cells, catalyzes the CO₂ ⇌ H₂CO₃ reaction almost instantaneously.
- Because of this, any change in CO₂ rapidly affects [H⁺], influencing pH.
H₂CO₃ is Hard to Measure:
- In clinical practice, we don’t measure H₂CO₃ directly.
- Instead, we estimate it using the partial pressure of CO₂ (PaCO₂), since:
[H2CO3] ≈ 0.03 × PaCO2
So physiologically, changes in PaCO₂ directly imply changes in H₂CO₃.
Acid Dissociation Equation: What is it?
What makes a component of the equation a conjugate base?
HA ⇌ H+ + A-
- H+ is the weak acid
- A- is a conjugate base
When an acid dissociates, and in the process a weak base is produced, that base is called a conjugate base.
