Altitude Physiology and the Stresses of Flight We will cover the following: The Atmosphere...

Altitude Altitude Physiology Physiology

and the and the Stresses of Stresses of

FlightFlight

We will cover the following:

The Atmosphere

• Composition

• Structure

• Physiologic Zones

GAS LAWSGAS LAWSUniversal Gas Law

Boyle’s Law

Charles’ Law

Henry’s Law

Dalton’s Law

Graham’s Law

Gay-Lussac’s Law

STRESSES OF FLIGHTSTRESSES OF FLIGHT

The Atmosphere

21%

OXYGEN

78% NITROGEN

1% O

ther

“Others” include: Argon, CO2, Neon, Helium, Krypton, Hydrogen

The AtmosphereAtmospheric composition percentages REMAIN THE SAME regardless of the

altitude.

O2 is 21%

N2 is 78%

Other is 1%

AT

Sea Level1,000 ft7,000 ft

14,000 ft30,000 ft

With an INCREASE in altitude, there is a DECREASE in pressure:

Alveolar 02 and Hgb Saturation Altitude Correction

ALTITUDE BAROMETRIC ALVEOLAR OXYGEN

(FEET) PRESSURE OXYGEN SATURATION

(mmHg) ( PAO2) % (SPO2)

Sea level 760 104 99

10,000 523 67 90

20,000 349 40 70

30,000 226 21 20

40,000 141 6 5

50,000 87 1 1

Oxygen transport in the blood:

Dependent on thepartial pressure of oxygen.

pOpO22

Universal Gas Law

GA

S LA

WS

Gas molecules of higher pressure move in the Gas molecules of higher pressure move in the direction of gas molecules of a lower pressuredirection of gas molecules of a lower pressure

PO2 = 100mmHg PO2 = 40mmHg

PO2 = 74mmHg PO2 = 66mmHg

Blood GaBlood Gass Exchange Exchange

PCO2 = 46 mm

PO2 = 100 mmPCO2 = 40 mm

PO2 = 40 mm

PO2 = 100 mm

PCO2 = 40 mmPCO2 = 46 mmPO2 = 1 - 60 mm

Arterial CapillaryArterial Capillary

Hemoglobin Saturation 98%Hemoglobin Saturation 98%

O2

O2

COCO22

O2

COCO22

O2

Venous CapillaryVenous Capillary

Hemoglobin Saturation 75%Hemoglobin Saturation 75%

Tissue Alveoli

TROPOSPHERE

Sea level to flight level 300 - 600 depending on temperature, latitude and season.

Physical Divisions of the Atmosphere

STRATOSPHERE

IONOSPHERE

EXOSPHERE

MOUNT EVEREST 29,028 FEET

1200 miles

600 miles

50 miles

Tropopause

Physiological Zones of the Atmosphere

EFFICIENT ZONE: Sea level to 10,000 feet

SPACE EQUIVALENT ZONE: 50,000 feet and above

DEFICIENT ZONE: 10,000 to 50,000 feet

10,000

50,000

18,000 ft

63,000 ft

The Principle of Atmospheric Pressure

• At sea level, the weight of a one square inch column of air extending to the edge of space is called “one atmosphere”. (ATM) 1 ATM weights 14.7 lbs (760 mmHg [torr]).

• As you ascend the pressure becomes less (0.5 ATM or 380 mm Hg at 18,000 ft)

• As you dive in water you increase the forces (or weight) on your body by 1 ATM for every 33 ft you are submerged. Hence the term diving “ 1atmosphere”.

GAS LAWS

Boyle’s Law

GA

S LA

WS

Robert Boyle

The volume of a gas is inversely proportional

to its pressure; temperature remaining

constant.

P1 x V1 = P2 x V2

DRY GAS EXPANSIONWET GAS EXPANSION1.8X 2.0X18,000

2.5X 25,000 3.0X

34,,000 5.0X

43,000

4.0X

9.5X6.0X

Gas Expansion

SEA LEVEL

Barotrauma and Boyle’s Law

• Free air in the Chest• Endotracheal Tubes• Gastrointestinal

Concerns– NG/OG tubes– Ostomies

• IV Fluids and Medications

• MAST

• Air Splints

• Dysbarisms– Barotitis Media– Barosinustitis– Barodontalgia

PN

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PN

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PN

EU

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PN

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-Ostomies and Gastic Tubes

• DO NOT allow air to become trapped in a closed –ostmy or NG/OG system. To include the space.

Endotracheal/ Trach. Tubes

• Air in the ET tube cuff should be replaced with sterile water/ NS prior to flight. Make sure to place in PCR and tell receiving hospital. Why?

• Some flight crews may elect to decrease and increase cuff pressure with ascent/decent.

• More prevalent in FW than RW (>1500 MSL)– Greater altitude span in FW– Longer exposure duration in FW

• Do not forget about Foley’s and NG Tubes

MAST/ Air Splints

• Document pulses prior to lift off.

• Monitor for decrease in circulation.

• Adjust pressure and document pulses at altitude as needed.

• Make sure to have pop-off values in place prior to take off.

DYSBARISMS

Barotitis Media

Barosinusitis

BarodontalgiaGastrointestinal

Changes

Barodontalgia

Tooth pain due to:

• Gum abscess: (dull pain on ascent)• Inflamed pulp: (sharp pain on ascent)• Inflamed maxillary sinus: (pain primarily on

descent)

Middle Ear Cavity

Eustachian Tube

Atmospheric Pressure

Tympanic Membrane

External Ear

Middle Ear Cavity

Eustachian TubeBlocked / Infected

Tympanic Membrane

External EarAtmospheric Pressure

Barotitis Media

Ear Block

Clear

Barosinusitis/ Sinus Blocks

Frontal

Ethmoid

MaxillarySphenoid

Treatment of Barosinusitis

• Stop the descent of the aircraft and attempt to clear by valsalva.

• If unable to clear, climb back to altitude until clear by pressure or valsalva.

• Descend slowly and clear ear frequently during descent.

• Use nasal spray (Afrin or Neosynephrine)

Charles’ LawAt a constant

pressure, the volume of a gas is directly proportional to the

absolute temperature of that gas.

V1/ T1 = V2/ T2

Charles’ Law in the Aero-Medical Environment

• For every 1° C temperature decreases gas volume will decrease by 1/273. Gas volume shrinks as temperature decreases.

• For every 1° C temperature increases gas volume will increase by 1/273. Gas volume increases as temperature increases.

1° C = V (-1/273)

1° C = V (+1/273)

Charles’ Law in the Aero-Medical Environment

1000’ Altitude

2 Degrees C

For every 1000 feet altitude increases,

Temperature decreases 2 degrees centigrade

Or

Climb 100m = 1°C drop

Charles’ Law in the Aero-Medical Environment

• Consider patients thermoregulatory status!– Warm blankets– Aircraft Heater– Warmed IV Fluids

• Consider effects on compress gases!– Oxygen/ medical air will compress/ expand

due to temperature changes.

Gay-Lussac’s LawDefines the relationship between pressure and temperature

At a constant volume, the pressure and absolute temperature of a gas are directly

proportional.

Example: O2/ SCBA bottles cool when opened & Heat when filling.

OR

That’s why if you check your bottle in the morning, you have less pressure then in the afternoon.

Gay-Lussac’s Law

Pressure

Pressure

Temperature

Temperature

Constant Volume

Henry’s Law• The amount of gas

dissolved in solution is directly proportional to the pressure of the gas over the solution.

Decompression Sickness

• Descend Immediately

• Compression greater than 1 atmosphere (ATM)

• 100% Oxygen

• Land at the nearest location where qualified medical assistance is available

Treatment

Evolved Gas Disorders

• Evolved gas disorders are considered serious medical emergencies and require emergent specialized care

WARNINGWARNING

Evolved Gas Disorders

The Bends (Limb Pain)

The Chokes (Respiratory Disturbances)

The Creeps (Skin Irritation)

The Staggers (CNS Effects)

Syncope (Cardiovascular Collapse)

Evolved Gas Disorders

• N2 bubbles become trapped in the joints. Onset is mild, but eventually painful !

The Bends

Evolved Gas Disorders

• N2 bubbles block smaller pulmonary vessels. Burning sensation in sternum. Uncontrollable desire to cough. Sense of suffocation ensures.

• N2 bubbles form along nerve tracts. Burning, tingling, itchy sensation and possibly a mottled red rash.

The Chokes The Creeps

Evolved Gas Disorders

• N2 bubbles affect spinal cord. Visual disturbances, paralysis, one sided tingling.

The Staggers

Dalton’s Law• The pressure exerted

by a mixture of gases is equal to the sum of the partial pressures of each gas in the mixture.

Pt = P1 + P2 +…+…

Dalton’s GangSimply stated, the sum of the partial

pressures is equal to the total pressure of a gaseous mixture.

P1 + P2 + P3 + P4 = P total

Oxygen Correction for Dalton’s Law

%FiO2 x P1 = %FiO2 needed at altitude

P2

P1= Beginning Barometric Pressure

P2 = Maximum Altitude Barometric Pressure

FiO2 35% x 760 (sea level) = FiO2% 51% needed

523 (10,000 ft )

Graham’s LawThe rate of diffusion of a gas through a liquid membrane is directly proportional to the solubility of the gas and is inversely proportional to the square root of its density or gram molecular weight.

How easily it moves across the membrane.

Graham’s Law and the Aero-Medical Environment

• CO2 has a solubility factor 20 times greater than O2 and will thereby, more readily diffuse across a liquid membrane.

Questions????1. The flight medic is more likely to feel the effects of altitude changes

when working in this environment?

1. Warm upper latitudes

2. Cold upper latitudes

3. Warm lower latitudes

4. Cold lower latitudes

2. When caring for the patient in the flight environment, the medic realizes that there are many flight stressors that affect the patient’s condition. Which of the following gas laws best describes the need to place supplemental oxygen on the patient during transport?

1. Boyle’s Law

2. Charles Law

3. Dalton’s Law

4. Gay-Lussac’s Law

Questions????

3. Medical equipment such as MAST/ air splints, IV drip rates, and endotracheal tube cuffs are more effected by which of the following?

1. Boyle’s Law2. Charles’ Law3. Dalton’s Law4. Henry’s Law

4. Which of the following gas laws is most responsible for soft tissue swelling during flight?

1. Boyle’s Law2. Charles’ Law3. Dalton’s Law4. Henry’s Law

Take a 5 minute Break!

The 8 Stressors of Flight• Hypoxia• Barometric Change• Thermal Change• G- Forces• Decrease Humidity• Noise• Vibration• Fatigue

Hypoxia

• Types of Hypoxia:– Hypoxic– Hypemic– Histotoxic– Stagnant

Hypoxia is a poor stimulus for respiration

Hypercarbia is much better

Hypoxic HypoxiaReduced

pO2 in the lungs

(high altitude)

Body tissueBody tissue

Red Red blood cellsblood cells

Inadequate Availability of Oxygen Molecules

Reduce pO2 in the lungs due to lower availability of oxygen molecules

Also Calle

d Altit

ude Hypoxia

Hypemic HypoxiaInability of the

blood to accept oxygen in

adequate amounts

++

++++

++

++++

++

++++

++

++

++

++ ++++

Medical Conditions

•COPD

•Pneumonia

•Pulmonary Edema

•Alcohol

•Pulmonary Embolism

Carbon m

onoxide

Histotoxic Hypoxia

Red blood cellsRed blood cells retain oxygenretain oxygen

Inability of the cell to accept or use oxygen

Poisoned tissuePoisoned tissue

AdequateAdequateoxygenoxygen

Medical Conditions

•Cyanide Toxicity

•CO Poisoning

•Anaphylaxis

•ETOH

•OD

Alcohol

Reduced bloodflow

Blood Blood movingmovingslowlyslowly

AdequateAdequateoxygenoxygen

Red blood cells Red blood cells not replenishing not replenishing

tissue needs tissue needs fast enoughfast enough

Stagnant HypoxiaMedical Conditions

• AMI

•Cadiomyopathy

•Cardiogenic Shock

•Crush Injuries

G-Forc

es

Hypoxia

Air HugerApprehension

FatigueNausea

HeadacheDizziness

Denial

Hot/ Cold FlashesEuphoria

BelligerenceBlurred Vision

NumbnessTingling

Symptoms

Subjective: Feel

HypoxiaSymptoms

Subjective: See

Hyperventilation

Mental Confusion

Cyanosis

Poor Judgment

WARNING !!!Failure to recognize the signs and symptoms of HYPOXIA in flight crew members may lead to a

Significant Emotional Event.

Stages of Hypoxia

Indifferent Stage

Compensatory Stage

Disturbance Stage

Critical Stage

Stages of Hypoxia

Indifferent Stage

Sea Level

10,000 ft.

Decrease in Night Vision at 4,000 ft.

MSL

Compensatory Stage

10,000 ft.

15,000 ft.

Impaired Efficiency Decreased Motor Skills Drowsiness Poor Judgment

Stages of Hypoxia

Stages of Hypoxia

Disturbance Stage

15,000 ft.

20,000 ft.

Marked loss in vision acuity. Marked loss of sensory function. Marked loss in audible acuity. Absence of memory. Loss of cognitive understanding. Complete loss of judgment

Disturbance Stage

Loss of Motor Coordination Speech Degradation Loss of Handwriting Skills

Performance Deficits

Time of Oxygen

1 Minute

2 Minutes

3 Minutes

4 Minutes

5 Minutes

6 Minutes

Put Back on Oxygen

Time of Useful Consciousness

• 5 minutes at 22,000 feet

• 18 seconds at 40,000 feet

• O2 required on all flights over 10’000 feet.

The elapsed time from exposure to oxygen deprived environment to the point where deliberate function is lost.

Protect yourself first !!!!!!!Protect yourself first !!!!!!!

Stages of Hypoxia

Critical Stage

20,000 ft.

ABOVE

Loss of Consciousness

Coma

Convulsion

Death

WWAARRNNIINNGG

WWAARRNNIINNGG

When Oxygen saturation falls to below 65%

serious cellular dysfunction occurs; and if

prolonged, will result in DEATH !!!!DEATH !!!!

Factors modifying hypoxia symptoms

• Pressure altitude• Rate of ascent

• Time at altitude

• Temperature

• Physical activity• Individual factors• Physical fitness• Self-imposed stresses

Self-Imposed Stresses

• Drugs

• Exhaustion

• Alcohol

• Tobacco

• Hypoglycemia

DDEEAATTHH

Be prepared to deal with these factors as seen

in your patients!!

Alcohol and Hypoxia

1 oz. of Alcohol is

physiologically equivalent to

2,000 ft.

1 oz.

2000 ft.

Tobacco and Hypoxia

3 Cigarettes smoked in rapid succession is equivalent to

5,000 ft.

3 chain smoked or ¼ pack in 4 hrs.

5,000 ft. MSL

Decreased Night Vision

Barometric Pressure Changes

Free Air in the Chest

ET Tubes

Pneumocephalis

GI/GU Concerns

NG/OG Tubes

Foley Catheters

Ostomies

Glass Bottles

PASG

Air Splints/ CAST

Dysbarism

Barotitis Media

Sinus Blocks

Barodontalgia

GAS LAWS

Thermal Stress

Increase in altitude produces a decrease in temperature.

Decrease in temperature produces an increase in metabolic demands.

What gas law covers this principle? CHARLES LAWCHARLES LAW

Gravitational Forces

Gravitational Forces

Col. John P. Stapp, USAF

632 mph acceleration in 5 sec. Decelerated to a complete stop in 1.4 seconds

Gravitational Forces

Gravitational Forces and the Medical Environment

• +G forces applied to Gz axis.

• Slow transition to horizontal flight.

• Little or no effect on hemodynamic status, perfusion or patient mental status

• Best of all options.Vertical Take Off

Gravitational Forces and the Medical Environment

• +G forces applied to Gx axis (seated) or –G axis (supine)

• Rapid transition to horizontal flight

• Significant effects on hemodynamic status, perfusion and mental status of the patient

• Take in consideration when deciding how to load the patient

Patient Positioning and Gravitational Forces

• Feet forward or head forward???

• Cardiac patient or Neurological patient?

• What about the high-risk OB patient?

Most patients are loaded along the long axis of the aircraft.

Decreased Humidity• An increase in altitude will produce a

decrease in humidity.

• Oxygen should be humidified for transports lasting longer than 1 hour.

• In general, most patients are dehydrated as a baseline.

• Consider fluid replacement early.

Noise Pollution

The Surgeon General has

established 85 decibels as the maximum level of continuous

unprotected exposure to steady-state noise for 8 hours

WWAARRNNIINNGG

WWAARRNNIINNGG

Noise Pollution Solution

Noise in the Aero-Medical Environment

Fixed Wing

• Most cabins are well insulated.

• Engines are placed away from patient and crew.

• Loudest during takeoff

• Does not require same protection

Rotor Wing

• Constant high noise environment.

• Engines directly over patient and crew.

•Greatly reduced communications.

• Requires soft plugs and headset/ helmet

Vibration

• Aircraft vibration can override the normal thermoregulatory mechanism, reducing

the body’s ability to generate or disperse heat.

Fatigue

Limit your self imposed stressors Drugs

Exhaustion

Alcohol

Tobacco

Hypoglycemia

Questions ????What is hypoxia?

The lack of oxygen to the tissues of the body

What are the four classifications of hypoxia?Hypoxic, hypemic, stagnant, and histotoxic

Give me an example of each classification of hypoxia:

Hypoxic – altitude; Hypemic – anemia, carbon mon-oxide poisoning; Stagnant – “G” forces, heart failure; Histotoxic – alcohol or drugs

What are the five signs (subjective) of hypoxia?

Hyperventilation, cyanosis, mental confusion, poor judgment, and muscle incoordinationWhat are the four stages of hypoxia with altitude?

Indifferent 0-10,000, compensatory 10,000-15,000, disturbance 15,000- 20,000 and critical stage 20,000- 25,000

Questions ????What are the SPO2 % with the four stages of hypoxia?

Indifferent 98%-90%, compensatory 89%-80%, disturbance 79%-70%, and critical stage 69%-60%

How can hypoxia be prevented?Use of oxygen, if available, or flights at lower altitudes

At what altitude will crew members start losing night vision?4,000 feet

How many times will carbon monoxide bind with hemoglobin molecules of red blood cells then to oxygen?

200 to 300 times

Smoking how many cigarettes in a rapid succession or how many in a 24 hour period will decrease your night vision by 20% and

give a physiological altitude of 5,000 feet?3/ 20

Lets play JeopardyLets play Jeopardy

This gas law states that gas expands as it rises What is Boyles Law

This gas law is responsible for decompression sickness What is Henry’s Law

This gas law states that as temperature increases so will volume

What is Charles’ Law

Alcohol and cigarettes decrease the ability for the hemoglobin to carry oxygen. Altitude has this same effect and is an example of this law What is Dalton’s Law

This law states that the rate of diffusion of gas is inversely proportional the square root of the density

What is Graham’s Law (Ex: C02 is more readily diffused across cell membranes)

SU

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AR

Y

Atmospheric Composition and Structure

Gas Laws in the Aero-

Medical World

Stresses Of Flight

Thank You for your

Attention!!!!