Ch 4 - Atmos, Gas Laws, Respiratory System Flashcards
Boyle’s Law
Volume is inversely proportional to Pressure
PV = K
Barotraumas - Otic
- Gastro Intestinal
- Sinus
Aerodontalgia - Air pockets in teeth
Charles’ Law
Volume is proportional to Temperature
Guy Lussac’s Law
Temperature is proportional to Pressure
Combined Gas Law
PV/T = K
P1V1/T1 =P2V2/T2
Dalton’s Law
Law of Partial Pressures
Sum of partial Pressures = Total Pressure
Linked to; Hypoxia and Night vision
Henry’s Law
Amount of gas dissolved in a liquid is proportional to the amount of pressure acting on it.
Linked to decompression sickness (DCS)
- Nitrogen in the blood, coming out of the solution in bubbles
Fick’s Law
Law of diffusion
Gas transfer in 2 areas
High to Low
Atmosphere Compromised Of
Nitrogen 78% Oxygen 21% 1% Other gasses compromising: - Argon 0.93% - Carbon Dioxide 0.038% - Others 0.0407%
Water Vapour roughly 1% (0%-5%)
ISA
MSL
Temperature +15 degrees C
Pressure 1013.25hPa or 29.92inHg or 760mmHg
Density 1.225kg/m cubed
Lapse Rate -1.98 degrees/ 1000ft
Tropopause
Edge of our atmosphere
11km (36,090ft)
11km - 20km = -56.5 degrees C
Humidity
Absolute - Weight of water vapour in a unit volume of air at a given temp
Relative (%) = Actual/Mass
Atmospheric Partial Pressures
MSL 760mmHg
3/4 = 8000ft
1/2 = 18,000ft
1/4 = 36,000ft
Lung Partial Pressures
MSL = 713 mmHg (47mmHg Water vapour)
= 98 Partial pressure of oxygen (13.7%)
12,000ft = 436mmHg roughly 55-59 partial pressure of oxygen
55 partial pressure of oxygen is the minimum required to function satisfactorily
Haemoglobin
Protein in the blood that absorbs and carries Oxygen
Made in bone marrow
Blood Saturation Levels (haemoglobin)
MSL = 97.5% 10,000ft = 87% 20,000ft = 65%
O2 Requirements in a non-pressurised cabin
0 - 10,000ft Air only
10,000 - 33,700ft Oxygen and Air mix
- Keeps body at ground/sea level
33,700 - 40,000ft 100% Oxygen
- Keeps body at 10,000ft (partial pressure)
40,000ft< Oxygen under pressure
- Keeps body at 10,000ft
Pressurised Cabin
Keeps body at 6000 - 8000ft
Helps prevent barotrauma, hypoxia, decompression sickness
The Anatomy of the Respiratory System
Nose - Filters, Moistens, Warms up to increase efficiency of gas exchange
Larynx
Trachea
2 Bronchus (Bronchi)
Bronchioles
Alveoli (300,000,000)
Respiration
External - Breathing -> the gas diffusion in the alveoli
Internal - Metabolism -> All cells in the body, Oxygen and Glucose metabolised to give energy to the cells
- 2 Waste Products - Water
- CO2 -> Carbonic Acid which increases Alkalinity
Lung Volumes
Tidal Volume 500ml Normal intake and exhale
Inspiratory Reserve Volume 3100ml Forcible inhale after TV
Expiratory Reserve Volume 1200ml Forcible exhale after TV
Residual Volume 1200-1400ml Always remains in lungs after ERV
Lung Capacities
Total Lung Capacity 6000ml Total of everything
Vital Capacity 4800ml 80% Total - Forcible exhale after inhale
Inspiratory Capacity 3600ml - Max air inhaled
Functional Residual Capacity 2400ml Amount of air in lungs after a normal exhale
Hypoxia Causes
Caused by low saturation levels of oxygen in the blood
- Reduced levels of atmospheric oxygen
- Lung Infections
- Blocked Airways
- Drug Overdose
Zones of Hypoxia
Indifferent Zone GL-10,000ft
- Night vision effected as low as 5000ft
Compensatory Zone 10,000ft - 15,000ft
- Automatic responses provide some protection against hypoxia trying to maintain homeostasis
Disturbance Zone 15,000ft - 20,000ft
- Classic Symptoms of Hypoxia
Critical Zone 20,000ft - 30,000ft
Homeostatic systems can no longer cope
Thresholds of Hypoxia
Reaction Threshold GL - 7000ft
- Dark adaption is adversely affected, can be as low as 5000ft
Disturbance Threshold 7000ft - 12,000ft
- Automatic responses provide some protection against hypoxia training to maintain Homeostasis
Critical Threshold 12,000ft - 22,000ft
- Incapacitation with loss of consciousness follows with little or no warning
Time of Useful Consciousness (TUC)
20,000ft 30 Minutes seated 5 minutes (halved if a smoker)
30,000ft 1 - 2 Minutes seated
35,000ft 30-90 seconds seated
40,000ft 15-20 seconds seated
Hypoxia Symptoms
Vary from person to person
- Skin discolouration - Cyanosis (blue) Paccor
- Cough
- Fast HR
- Rapid Breathing
- Shortness of breath
- Sweating/Wheezing
- EUPHORIA (the bad one)
- > Impaired judgement (another bad one)
- Formication (ants)
Hyperventilation & Causes
Losing too much Carbon Dioxide
Causes;
- Anxiety - Personal
- Motion Sickness
- Stress - Personal
- Self induced (deliberate)
Hyperventilation Symptoms
- Rapid Breathing
- Tingling
- Dizziness
- Nausea
- Blurred Vision
- Loss of consciousness -> Reset Body
Decompression Sickness/ Illness (DCS)
When dissolved gasses, usually Nitrogen, come out of solution as bubbles in the blood
Going from high to low pressure too quickly
Above 14,000ft
Won’t occur in a pressurised cabin
Scuba diving makes it more likely pre-flight
Heavy Exercise
Hung over
Fat/Obese. All make it worse!!
Decompression Sickness Symptoms
Bad hang over or flu like symptoms Weakness Arthritis pinch points Numbness Ringing ears Tired Chest Pain Sweating
Avoid Alcohol pre flight
Previous flight too close to next flight
Avoid heavy exercise pre flight.
Emergency descent, land see specialist, O2 mask
Effect of Decompression at altitude
The higher pressure in the aircraft will want to escape to the low pressure outside of the aircraft
Escaping air:
- Increased velocity
- Decreased Static Pressure inside the aircraft making the cabin pressure feel like it is 5000ft higher than it actually is
- Rapid reduction in temperature which could reach the dew point of the moisture in the air, leading to condensation and then fog in the cabin
What to do in the event of a decompression
O2 mas on breathing 100% O2
Start decent to 10000ft or minimum safety altitude (MSA) or which ever is higher
- Inform ATC
