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What is Boyle's Law?
The volume of a gas is inversely proportional to the pressure under constant temperature (Boyle's Balloon)
What is Barotitis Media?
- Air in the middle ear
- Eustachian tube gets clogged
- Descent problem
What is Barodontalgia?
- Air trapped beneath dental work
- Ascent problem
- Air expands due to barometric PSI, exerts
- pressure on nerve & dental cap or work
- Slow your ascent
What is Barosinusitis?
- Air trapped in the sinuses
- Ascent problem
- Slow ascent
- Nasal decongestant
What is Barobariotrauma?
Gas trapped in tissue suddenly released
Describe typical Barobariotrauma patient
- Heavy/Obese pt w/lots of adipose tissue
- Large amount of N released during ascent
- Pt can’t blow it off fast enough
- N bubbles form in bloodstream (The Bends)
Describe the treatment modality for Barobariotruma
- PreOxygenate all obese pts w/100% O2
- Pressure gradient results – Hyperoxygenation
- results in N getting washed out of lungs (100% O2 = 0% N inspired),
- High N pressure gradient in bloodstream,
- N moves to lungs and is exhaled
Define Charles' Law
- At a constant pressure, the volume of gas is directly proportional to the absolute temperature of the gas
- “Heat a gas and it’s volume will expand if it can, cool it back down and it’s volume will contract”
- Charles – centigrade – volume
What is the relationship between altitude gain & temperature drop?
100 m altitude increase = 1° C drop
Define Henry's Law
- At a constant temp, the amt of a given gas dissolved in a liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid
- Henry’s Heineken
- Cx = (Px)(k)
What is Gay-Lussac's Law?
- Charles’ gay brother
- Same as Charles law only in a vessel with a fixed size
- Directly proportional relationship btn temp & pressure
- Temp ↑, PSI ↑; Temp ↓, PSI ↓
Define Partial Pressure of a Gas
The pressure that a gas, in a mixture of gases, would exert if it alone occupied the whole volume occupied by the mixture
Define Graham's Law
The diffusion rate of a gas through a liquid medium is directly related to the solubility of the gas & inversely proportional to the sq rt of its density
What are the factors relevant to Graham's Law?
- Maximize alveolar surface area, Minimize diffusion distance through removing as much edema as possible
- Surface Area
- Diffusion Gradient
- Diffusion distance
- Molecular size
What is Dalton's Law?
- Total Pressure = Sum of the Partial Pressures of all the Gases
- Dalton’s Gang
What are the 5 flight stressors?
- OTCs count too
- Predisposes you to spatial disorientation
- Night vision lost @ 5,000’
- Tobacco use = lose 4,000’
- Periphery is your rods, night vision
- CoHb affects retina swiftly
What is MSL?
Mean Sea Level
Wht is AGL?
Above Ground Level
What is ATM?
- @ sea level, the weight of a one square inch column of air extending to the edge of space is called “one atmosphere”. This refers to atmospheric pressure.
- 1 ATM weighs 14.7 psi or (760 mmHg [torr])
- Atmosphere increase w/every 33’ of depth below water, atmosphere decreases to 0.5 ATM or 380 mmHG @ 18,000’
- Atmosphere is 250k’ to 300k’
- Atmosphere is non-uniform in density
- Perfect Day: 59°F
measurement of pressure in mmHg
measurement of pressure in pounds per sq inch
Define "physiologic zone"
Sea level to 10,000’
Define "physiologic deficient zone"
10,000' to 50,000’
What is the "space-equivalent zone"?
50,000' to 250,000'
At what elevation does "space" begin?
Define "Hypoxic hypoxia"
- Deficiency in alveolar O2 exchange (aka altitude hypoxia)
- Any drop in available PO2
- Venous mixing
Define "Histotoxic Hypoxia"
- A failure of the tissue’s ability to use O2 presented. Commonly a result of poisoning or metabolic disorders.
- Ex: Cyanide
Define "Hypemic hypoxia"
- Reduction in the O2 carrying capacity of the blood
- Anemias: Ex. Sickle cell
- CO poisoning
What are the characteristics of the "Indifferent" stage of hypoxia?
- Slightly ↑ HR & RR
- ↓ Night vision
What are the characteristics of the "Compensatory" stage of hypoxia?
↓ BP & ↓ Task performance (esp multitasking)
What are the characteristics of the "Disturbance" stage of hypoxia?
- Tunnel vision
What are the characteristics of the "Critical" stage of hypoxia?
- Marked mental confusion & incapacitation
- Seizure / Coma / Death
What is the Altitude Adjustment Calculation?
What effect does altitude have on PaO2?
PaO2 ↓ ~5mmHg/1000’ ↑ in altitude
Define "Effective Performance Time"
- The amount of time a FCM is able to perform useful flying duties in an inadequately oxygenated environment
- Minutes to hours to days
Define "Time of Useful Consciousness"
The elapsed time from exposure to oxygen deprived environment to point where deliberate function is lost
What are the 2 types of decompression events?
Explosive & Controlled
Compare the impact an Explosive Decompression has on Time of Useful Consciousness to that of a Controlled Decompression
In an Explosive Decompression, Time of Useful Consciousness is ~ ½ that of Controlled Decompression
What is ATP (Adenosine Triphosphate)?
A compound of of adenosine containing 3 phosphoric acid groups. Its chemical formula is C10H16N5O13P3. ATP is present in all cells & is formed when energy is released from food molecules during cell respiration. Cells contain enzymes to hydrolyze ATP into ADP, phosphate & energy, which is then available for cellular functions such as mitosis
What is ADP (Adenosine Diphosphate)?
A compound of adenosine containing 2 phosphoric acid groups. ADP is used to synthesize ATP w/the energy released in cell respiration. When ATP is used for cellular functions, such as protein synthesis, ADP is reformed.
What is AMP (Adenosine monophosphate)?
A substance formed by condensation of adenosine & phosphoric acid. It is one of the hydrolytic products of nucleic acids & is present in muscle, RBCs, yeast & other nuclear material.
What is adenosine?
A nucleotide containing adenine & ribose. Also pharmacological agent used to block cardiac conduction through the AV node.
- Fraction of inspired O2 The conc’n of O2 in the inspired air, esp. that supplied as supplemental O2 by mask or catheter.
The partial pressure in arterial blood; arterial O2 conc’n, or tension; usually expressed in mmHg
What is the difference between PaO2 and PAO2?
The difference btn PaO2 & PAO2 is the Aa Gradient – should be small in most pts but can expand.
What is PAO2?
Partial pressure of ALVEOLAR O2
Partial pressure of venous O2. Symbol for partial pressure of O2 in mixed venous blood.
Arterial Saturation of O2. % of arterial hemoglobin saturated w/O2
What is the difference btn SpO2 & SaO2?
The difference btn SaO2 & SpO2 is generally the measuring hardware – SaO2 uses art line co-oximeter, SpO2 uses infrared wavelength. When there are differences in readings, susp Methemoglobin & Methemoglobinemia & CO intoxication
Define ABG (Arterial Blood Gas)
Any of the gases present in blood. Operationally & clinically, ABGs include the determination of levels of pH, O2, & CO2 in the blood.
Aerobic metabolism yields how many ATP?
Anaerobic metabolism yields how many ATP?
2 or 3
What are the factors affecting O2 delivery?
- FiO2Adequate Hemoglobin
- Cardiac Output – The ability to move hemoglobin & O2Ability to extract O2 from hemoglobin
- Ability for cells to use O2
What is the ultimate test for acidosis?
What is considered a normal lactate level?
1 mmol/L ± 0.5
Above what level is a lactate level considered a sign of significant acidosis?
What is the expression of the sodium bicarbonate buffer system?
CO2 + H2O ⇋ H2CO3 ⇋ H+ + HCO3-
Define the Bohr Effect
The effect of an acid environment on hemoglobin; H+ ions alter the structure of Hgb & ↑ the release of O2. It is esp. important in active tissues producing CO2 & lactic acid.
What are the signs of a Leftward shift in the Oxyhemoglobin Dissociation Curve?
- HoLds O2
- Low temp
- Low 2-3DPG
- Lots of CO
What are the signs of a Rightward (BohR Effect) shift in the Oxyhemoglobin Dissociation Curve?
- Releases O2
- Raised acidosis
- Raised Temp
- Raised 2-3DPG
- Reduced Oxygenation
What is the normal relationship of HCO3- to H2CO3?
20 : 1
Where does the carbonic acid-bicarbonate buffer system operate?
Primarily in the blood, lungs & kidneys
What organ can eliminate fixed acids?
How much HCl can the respiratory system eliminate daily?
How does PaCO2 relate to ETCO2?
ETCO2 should be slightly lower than PaCO2 (otherwise there wouldn't be a conc'n gradient to drive the diffusion of CO2 into the alveoli)
What 4 elements must be in place in order to obtain reliable ETCO2?
- CO2 production must occur at the tissue level & diffuse to the blood following a conc’n gradient
- Cardiac output must be high enough to carry the blood to the lungs from the tissue
- CO2 must diffuse from the blood to the alveoli following a conc’n gradient
- Tidal Volume (Vt) & ultimately alveolar volume (VA) must move the CO2 to the ETCO2 sensor inlet
How does PaCO2 relate to pH?
PaCO2 Δ of 10 mmHg will cause a pH Δ of 0.08 ⇅
What are the secondary buffer systems?
- Protein buffer system
- Phosphate buffer system
What is the most prominent intracellular cation?
What is the most prominent extracellular cation?
How does acid-base balance influence potassium?
- The more acidic the blood, the greater the amount of H+. The more H+ in the ICF, electrical polarity forces K+ out to the Interstitial Fluid (ISF). The Law of Mass Action results in a K+ shift into the blood, Lab samples will show a hyperkalemia.
- The inverse of this holds true.
How can we predict K+ shifts?
- For every Δ in pH of 0.1, we will see a Δ K+ of 0.06 ⇅
- For every Δ in PaCO2 of 10 torr, we will see a Δ in K+ of 0.5 mEq/L
How do we correct hyperkalemia d/t acid-base disturbance?
- CaCl (raises the action potential)
- NaHCO3- (raise the pH, electrical gradient manipulated)
- D50 (K+ follows the D50)
- Insulin (Helps sugar into the cell; for every amp D50 give 5-10 u of insulin)
- β2 agonist (albuterol on continous neb)
How do we correct true hyperkalemia?
- furosemide (need functioning kidneys, foley in place)
- sodium polystyrene sulfonate (Kayexalate) (Faster than furosemide but will bind with Ca+, Mg+ & Na+)
How do we manage hypokalemia?
- You should administer K+ typically @ 10-20 mEq/hr
- Do NOT exceed 0.5-1.0 mEq/kg/hr
What is the normal ARTERIAL pH on an ABG?
7.35 - 7.45
What is the normal ARTERIAL PaCO2 on an ABG?
35 - 45
What is the normal ARTERIAL HCO3- on an ABG?
22 - 26
What is the normal ARTERIAL PaO2 on an ABG?
80 - 100
What is the normal ARTERIAL SaO2 on an ABG?
What is the normal ARTERIAL BE on an ABG?
-2 - 2
What is the normal VENOUS pH on an ABG?
7.31 - 7.41
What is the normal VENOUS PvCO2 on an ABG?
40 - 50
What is the normal VENOUS HCO3- on an ABG?
22 - 26
What is the normal VENOUS PvO2 on an ABG?
35 - 40
What is the normal VENOUS SvO2 on an ABG?
70 - 75%
What is the normal VENOUS BE on an ABG?
-2 - 2
Generalize ABG interpretatio
- A “high” CO2 suggests ACIDOSIS
- A “low” CO2 suggests ALKLOSIS
- A “high” HCO3- suggests ALKALOSIS
- A “low” HCO3- suggests ACIDOSIS
What is the 1st Golden Rule of ABG analysis?
For every 10 mmHg Δ in CO2, the pH will Δ 0.08 in the opposite direction
What is the 2nd Golden Rule of ABG analysis?
For every Δ in HCO3- of 10 mEq, the pH will Δ 0.15 in the same direction
What is the 3rd Golden Rule of ABG analysis?
Formula for calculating HCO3- replacement is: (kg/4) x Base Deficit = mEq of HCO3-
How do you calculate anion gap?
Sum Na+, Cl- & TCO2 (HCO3-)
What are normal anion gap values?
- 8-16 (w/o K+)
- 10-20 (w/K+)
What is the significance of an anion gap of > 20?
- Metabolic Acidosis
- The higher the anion gap, the worse the acidosis
Name the 4 suspects in Metabolic Acidosis
- Lactic Acid
How do we check for lactic acid?
- Lactate level
- Altered LOC
- ↓ Urine Output
- Decreased Cardiac Output
How do we check for Renal issues?
- ↑ BUN
- ↑ Creatinine (better)
How do we assess for toxins?
What does MUDPILES stand for?
- Isoniazide & Iron
- Ethylene Glycol
What are the causes of electrolyte disorders in metabolic alkalosis?
- GI Loss of H+: OG/NG Suctioning & N/V
- GI Loss of K+: Diarrhea
What is the Alveolar O2 Pressure Formula?
What is the A-a Gradient Formula
- A-a Gradient= PAO2-PaO2
- PAO2 is generally held to be 101.73 torr
When should your A-a gradient calculation prompt an investigation?
A calculation of > 10 torr
At what point does your A-a gradient calculation indicate the presence of disease?
A calculation of > 20 torr
How do you improve Oxygenation?
- Assure adequate VA (Assess Vt & rate)
- Maximize FiO2Add PEEP
- Invert I:E ratio