Aeromedical/Gas Laws/ Mech. Ventilation Flashcards
What is Tidal Volume? (Vte)
The volume of air drawn into the lungs during inspiration from the end expiratory position, which leaves the lungs passively during expiration in the course of quiet breathing.
What is Peak inspiratory pressure (PiP)?
The highest airway pressure measured during inspiration.
PiP is a product of Vt/Compliance/Resistance/ Flow. Measured in cm/h20
What is inspiratory time (Ti)?
Measured in seconds
The time duration from the end of exhalation to the end of inhalation
What is expiratory time (Te)?
Measured in seconds
The time duration from the end of inhalation to the end of exhalation.
What is Flow? (vCalc)
Flow is the speed of airflow during inhalation, it is measured in LMP
-Flow (vCalc) is the product of Vt, resistance, and Ti
What is Plateau Pressure (pPlat)
pPlat is the pressure applied to the small airways and alveoli during a pause during inspiration on the mechanical vent.
Describe positive end expiratory pressure (PEEP)
The pressure that remains in the lungs after exhalation has stopped and a no flow state exists.
PEEP is the product of the remaining volume of gas not exhaled during the respiratory cycle.
What is Auto PEEP?
The pressure that remains in the lungs after exhalation has stopped and a no flow state exists beyond the set PEEP.
This is the product of remaining volume of gas not exhaled during the respiratory cycle, usually this is caused by a lack of expiratory time (Te).
What is PEEP compensation?
is when the mechanical vent. recognizes PEEP and will deliver desired pressure breaths on top of set PEEP.
Non-PEEP compensation
When the mech. Vent. does not recognize PEEP and will deliver desired pressure breaths to a total pressure including PEEP.
I:E Ratio
The ratio of inspiratory time vs expiratory time (Ti VS Te)
I:E is set into the ventilator, however patients may need a specific I:E to support their condition (ie. Asthma)
What is Trans-Pulmonary pressure (Ptp)
The difference between the alveolar pressure and pleural pressures
What is Trans-Pulmonary PEEP?
The Pip calculated at end exhalation
Trans pulmonary plateau pressure (Pplat)
The Pip calculated at the end of inhalation
What is Bias Flow?
10 LMP of flow in the vent circuit
What is “patient triggering”
When the patient initiates a delivered breathe before the next set interval
what is Sensitivity in mechanical ventilation?
A measure of 1-9 indicates the detected change in bias flow required for the patient to trigger.
Name the 8 modes of ventilation
- Volume Control
- A/C Volume
- Pressure Control
- A/C Pressure
- Pressure Support
- SIMV
- CPAP
- BiPAP
Describe Volume Control mode
Volume control is a set volume with a defined rate, no patient triggering, volumes constant, pressure variable
A/C Volume
Allows for patient triggering, WOB dependent on sensitivity
Pressure control
- Set pressure
- Defined Rate
- No patient triggering
- Pressures constant, volume variable
A/C Pressure
Allows for patient triggering, WOB dependent on sensitivity
Pressure Support
- Requires spontaneous respiratory efforts
- Flow triggered
- Flow terminated
- Most physiological mode of ventilation
- Most comfortable mode of ventilation
- Volumes rate and pressure are variable
Synchronized Intermittent mandatory ventilation (SIMV)
- Garuteed minimum minute volume
- Allows patient triggered breathes
- Allows patient to assume WOB
- Synchronicity with the ventilator.
CPAP (Continuous positive airway pressure)
- Provides a set pressure during exhalation
- Assuring a minimum airway pressure
BiPAP (Bi level positive airway pressure)
- Delivers inspiratory pressure
- Maintains expiratory pressure
- Practitioner sets E pressure and I pressure independently
General Hypoxia
inadequate oxygen supply to the body as a whole.
Tissue Hypoxia
Lack of oxygen to a specific region
4 types of hypoxia
- Hypoxic hypoxia
- Histotoxic Hypoxia
- Stagnant Hypoxia
- Hypemic Hypoxia
Hypoxic Hypoxia
Caused by a decreased amount of oxygen in the blood due to a reduction in O2 pressure in the lungs, reduced gas exchange area, exposure to high altitude or lung disease.
Histotoxic Hypoxia
Caused by the inability of the tissues to utilize oxygen. Usually a result of poisoning (cyanide/carbon monoxide)
Stagnant Hypoxia
Hypoxia caused by a malfunction of the circulatory system resulting in a decrease in blood flow.
(Cardiogenic shock, Distributive shock)
Hypemic Hypoxia
Hypoxia caused by a decreased level of hemoglobin carrying capacity or a reduced number of red blood cells.
Describe the “Physiologic Zone”
The area of sea level to 10,000ft. Barometric pressure is an average of 760mmHg, 101.3 kilopascal, 14.7 psi aka 1 atm.
What are the air contents at sea level?
78% Nitrogen, 21% oxygen, 1% Argon, 0.04% carbon dioxide. Remainder is all trace gases.
What is the “physiologic deficient” Zone?
The area from 10,000-50,000ft. Above 10,000ft barometric pressure begins to decrease resulting in hypoxic hypoxia
What are the 4 stages of hypoxia
- Indifferent stage
- Compensatory Stage
- Disturbances stage
- Critical Stage
Indifferent stage
ranges from sea level to 10,000ft. However symptoms may manifest themselves as low as 5,000ft.
Minor effects, spo2 varies to 97-98%
Compensatory stage
Ranges from 10,000 and 15,000ft OR 39,000 to 42,000 ft if breathing 100% oxygen.
At this stage the Body is able to compensate physiologically by increasing respiratory rate and depth, cardiac output. Spo2 ranges from 80-87%.
Disturbance Stage
Ranges from 15,000 to 20,000ft
-The body is no longer able to depend upon physiologic compensatory mechanisms. Hypoxia occurs leading to impaired physiology.
Critical Stage
Ranges from 20,000 - 25,000ft
Spo2 less tha. 65%. Badness.
Name 5 primary stressors of flight.
- Decreased PaO2
- Thermal Changes
- Vibration
- Decreased Humidity
- Gravitational forces
Name 3 patient populations that will no tolerate moderate to severe turbulence or severe G-forces
- TBI
- SCI
- Hemodynamically compromised patients
what are the 7 Gas-Laws?
- Boyles Law
- Charles Law
- Daltons Law
- Ficks Law
- Henrys Law
- Gay-Lussacs Law
- Grahams Law
Boyles Law
As barometric pressure drops, Gas will expand. Increased altitude causes decreased pressure, causing gas expansion.
Charles Law
Volume of gas is directly proportional to the temperature, pressure remains constant.
as altitude increases, pressure decreases and so does temperature, and volume.
As temperature increases, air becomes thinner.
Daltons Law
The total of a mix of gas is the sum of all its parts.
As altitude increases pressure goes down and so do the individual components of a gas
Ficks Law
Diffusion rate of gas across a membrane depends on pressure, surface area, and inversely proportionate to membrane thickness.
Henrys Law
As pressure decreases, gas dissolved in liquid will also decrease. These are directly proportionate.
Gay-Lussacs Law
As altitude increases, pressure decreases and temperature decreases
Grahams Law
Molecullar weight alters rate of diffusion. The heavier the molecule the faster it diffuses.
