Chp 2-Flight Physiology And The Physiological Stresses Of Flight Flashcards
Dalton’s Law
The law of partial pressure. The total pressure of a gas mixture is the sum of the individual (or partial) pressures of all gases in the mixture. Barometric/atmospheric pressure is the pressure exerted against an object by the atmosphere. As altitude increases, barometric pressure decreases. Oxygen concentration remains 21% regardless of altitude. Barometric pressure multiplied by the concentration of gas is equal to the partial pressure of the gas. As altitude increases, the partial pressure of a gas decreases. The actual available oxygen decreases with altitude because oxygen mol- ecules move farther apart, possibly resulting in hypoxia.
Boyle’s Law
The principles of gas expansion. At constant temperature, the volume of gas is inversely proportional to the pressure. An increase in altitude causes a decrease in barometric pres- sure. One example is the volume of gas in a balloon will expand at altitude
Charles’ Law
When the pressure is constant, the volume of gas is nearly proportional to its absolute temperature. If the mass of gas is kept under constant pressure and the temperature of the gas increases or decreases the volume will increase or decease accordingly. When flying at sea level to 35,000 ft, temperature decreases 1 degree every 100 meters (330 ft)
Henry’s Law
The principle of evolved gas disorders. The solubility of gases in liquids: The quantity of gas dissolved in 1 cm3 (1 ml) of a liquid is proportional to the partial pressure of gas in contact with the liquid. The weight of gas dissolved in a liquid is directly proportional to the weight of the gas above the liquid. An example is shaking a can of soda and opening it immediately.
Graham’s Law
The law of gaseous diffusion. Gases flow from higher pressure (or concentra- tion) to a region of lower pressure (or concentration). Simple diffusion or gas exchange at the cellular level is an example
Stresses of Flight
decreased partial pressure of oxy- gen, barometric pressure and thermal changes, decreased humidity, noise, vibration, fatigue, and gravitational forces (G-Forces)
Decreased Partial Pressure of Oxygen (paO2)
At altitude oxygen is decreased
Barometric Pressure Changes
Gas expands
Thermal Changes
An increase in altitude results in a decrease in ambient temperature. Air- craft cabin temperature fluctuates considerably depending on the temperature outside the aircraft
Decreased Humidity
When air is cooled, it loses its ability to hold moisture. Air at altitude is cold, possessing very little moisture. The higher the altitude, the colder and drier the air.
Gravitational Forces (G-Forces)
Acceleration and deceleration along the longitudinal axis (fore/aft) is the most important G- force to be considered in aeromedical transport. Newton’s First Law of Motion states that unless acted upon by a force, a body at rest will remain at rest, and a body in motion will move at constant speed in a straight line.
Types Of Hypoxia?
Hypoxic, Hypemic, and Stagnant
Hypoxic Hypoxia (Altitude Hypoxia)
Caused by exposure to the airborne environ- ment. Results in deficiency in alveolar oxygen exchange. A lower barometric pressure at altitude results in a decrease in alveolar paO2 and interferes with ventilation and perfusion. Any condition requiring oxygen at sea level must be closely monitored at altitude.
Hypemic Hypoxia
A reduction in the oxygen-carrying capacity of the blood caused by anemia, hemorrhage, hemoglobin abnormalities (sickle cell disease), drugs (sulfur nitrites), or chemicals (cyanide, carbon monoxide). Carbon monoxide has a 200 x greater affinity to bond to hemoglobin than oxygen.
Stagnant Hypoxia
A reduction in total cardiac output due to the pooling of blood and the reduced blood flow to the tissues. Interferes with the transportation phase of oxygen by reduc- ing systemic blood flow.
