Question Answer
What is a ventilator? Machine/device that can fully or partially substitute for the ventilatory work accomplished by the patient’s muscles.
This type of ventilator is set to deliver a tidal volume of 600ml. Only 450ml are actually being delivered to the patient. This ventilator contains a system that will compensate for the lost volume. What type of system is this? Closed-loop system
The ventilator you are working with in the ICU is a combination ventilator. What does this mean and what does each power source control? This ventilator is both electrically and pneumatically powered. Pneumatic source powers the energy to deliver the breath and the electrical source powers the internal functions of the vent.
What are the two basic parts of a ventilator? user interface and control system
This type of control system delivers what you set for it to deliver. It does not count for the lost volume. These are mostly found on older types of ventilators or home ventilators. What type of control system is this? Open (Unintelligent) system
This type of ventilator has an on and off switch to start and stop the power. What type of power source is this ventilator and in the hospital, where should this ventilator always be plugged in at? Electrical power source RED outlet
How are ventilators classified? -Positive or Negative pressure -Power source -Control system -Driving mechanism
If you are transferring a patient from the hospital to a rehab center, What type of ventilator would you use and why? IPPB – Because it is pneumatically powered
While setting up a ventilator, you notice that it is not working. After no success at troubleshooting, where would you send the ventilator to be repaired? Biomedical
What is the difference between pneumatic, electrical, and combination powered? Pneumatic- air powered Electrical- has to be plugged in or a battery source Combination- uses both power systems
Define unintelligent circuit. It is an open system where a setting is delivered no matter what.
Give an example of a vent that is a positive, pneumatic powered, open control system and a flow controlled driving mech. Bird or Bennett IPPB
What are the different types of driving mechanisms in ventilators? Blower, volume displacement, flow control values
In an open system, the Vt is set at 600ml what will be the amount delivered to the patient? 600ml, it will deliver the amount set even if it is losing some to the circuit
What is the difference between the user interface and the control system. User interface-what therapists see and use Control system- internal system that takes what we entered as settings and produces the desired output
Describe the type of vent, power source, control system, and driving mechanism of an NIV. Type: Positive Pressure Power: Electrical Control System: Open Driving Mechanism: Blower/Compressor
What type of driving mechanism would an 840 ventilator use? Where are these usually seen? Flow Control Valve ICU
What is the most common type of ventilator found in the ICU? Positive pressure, flow control, closed system, combination powered vent
If we are using a iPPB Bird what is the type of vent, the power source, the control system and the driving mechanism used? Positive pressure, pneumatic, open, and flow control valve
What is a closed system and why is it more favorable in the ICU or with critically ill patients? An intelligent system that compares set settings to measured results. It is favored because it compensates for lost volume or small changes with the patient.
What type of ventilator would you choose for a patient moving from ICU to general care who requires continuous ventilatory support? Bird Mark 7
Who developed the classification system for ventilators? Mr. Robert Chatburn (RQ) (JB)
The user interface consists of what? knobs, buttons, touch screens to enter settings on.
If you are moving a pt home on a ventilator, what would you want this ventilator’s classifications to be? Positive, electrical, open, compressor.
When were there the first ventilators? 1950-1960s
Which type uses valves to control gas flow and uses this driving mechanism in ICU Vents? Flow control
What type of ventilator is both electrically and pneumatically driven and is found on most vents where? Combo; ICU
Ventilation has been around since when? 1800s
When would you want a flow control valve ventilator over a blower/compressor ventilator? short term vs long term, sensitive for patient care vs not sensitive
If a patient was admitted through the ED to the ICU, what ventilator settings would be practical? positive ventilation, combination power source, closed system, and flow control valves due to the acuity of the patient.
Why is it important to have ventilators plugged into the red outlets? In case of a power outage, they would be plugged into the generator back up system.
How does a combination powered ventilator use both the pneumatic power and electrical power? It uses the electrical power to to control the internal function and the pneumatic power to deliver the breath.
What is a micropressor? And what does a micropressor-controlled ventilator have the ability to do? A mircopressor is a single chip made up of many integrated circuits. A micropressor-controlled ventilator comes with pre preprogrammed mode but has the ability to upgrade by downloading new software to it.
Classification system of ventilators was developed by who? Robert Chatburn.
You have a patient that needs to get an airway and be ventilated, the patient has had long term ventilation. What would be best? a Positive pressure, combination source, closed system with flow control valves. With a trach.
An IPPB uses what kind of power transmission and conversion system. Flow control valves
What was introduced first, PEEP or CPAP? PEEP 1967, CPAP 1971
what kind kind of power source(s) can a ventilator be? Electrical (home ventilators) Pneumatic ( transport ventilators) Combination (ICU ventilators)
What classifications does a Bennett have? Positive, pneumatic, open, flow control.
A ventilator using volume displacements uses what mechanism to fill volume? Uses Bellows or Pistons.
When setting up a circuit what parts will you want to check? The main inspiratory line, the patient adapter/y-connection, expiratory line, expiratory valve.
In an open system set to give a Vt of 600 mL if there is a leak what will it deliver to the patient and what would the patient receive? The device would deliver 600 mL, but due to the leak the patient would receive less because it would not compensate for the lost volume.
If you are working with a patient on a vent in the ICU what type of Control System would you find? closed
What type of power source is most commonly used and what does this do. combination, pneumatic source powers the energy to deliver a breath and electrical sources power the internal functions of the ventilator
If you are taking care of an ill patient, why woud a Blower System not be a good driving mechanism? When would it be okay to use for this type of patient? It doesnt have the the highflows we need for ill patients. It can be used if we need to transport the pt. for a procedure or appointment ect.
Robert Chatburn developed a classification system of what? ventilators
The part we see and use as a control panel is called ________. It is an (internal/external) feature containing knobs buttons, touch screen to enter ventilator _________. user interface ; external ; settings
A circuit is set at 750mL and it delivers that amount regardless of lost volume in the circuit. This is an __________ system, which is also called an __________ system. Open ; unintelligent
Of the basic elements in a patient circuit, what does the expiratory valve do? It allows release of exhaled gas from the expiratory line into the room.
If a patient has a VT of 500 mL, and a respiratory rate of 16 what would you use as a Mandatory Minute Ventilation value? A value less than 8 Lpm.
Flow or Pressure: a solenoid can be controlled by _______ to change the __________. A solenoid can be controlled by pressure to change the flow.
Define a closed-loop system Described as “intelligent”. This system compares the set control variable to the measured control variable and can respond to changes in patient’s condition.
What phases of a breath are considered “active.” Exhalation to Inspiration, Inspiration, and Inspiration to Exhalation.
Given the information, find the intrinsic PEEP. Extrinsic PEEP 3cmH2O, Total PEEP 8cmH2O. Intrinsic PEEP= 8cmH2O-3cmH2O=5cmH2O
In an Open-looped system the Vt is set at 700ml. The patient’s exhaled Vt is 550ml. How much of the delivered Vt is lost and where might it have gone? 700ml-550ml=150ml is lost. Might have been lost in ventilator circuit.
If the Vt is set at 550ml once this is acheieved the vent will allow the pt to exhale. This is called _________, and it also ends inspiration and begins ___________. Cycling; exhalation
When will Raw be increased? Airway Obstruction, ET tube with a small diameter, obiesty.
Given the information, calculate PaO2/FiO2 to determine if your pt has extensive lung damage or not. PaO2= 80 FiO2=.28 80/.28= 286. This pt has ALI because our result was 200-300.
In a positive pressure ventilator why does the gas flow into the lungs? This is because the ventilator made a pressure gradient by creating a positive pressure at the opening of the airway
In a closed system the setting for Vt is set at 650 ml. How many ml will be delivered to the patient? In a closed system the ventilator will adjust to give the right Vt to the patient.
Name three setting components that are found on a ventilator control panel and what four variables do they ultimately regulate? Tidal volume, rate, inspiratory time, alarms, and FiO2. Which regulate flow, volume, pressure, and time.
What type of control system delivers a set setting no matter what? What type of setting would you most likely find me? Open System- Unitelligent System In home Setting
What year was the IMV introduced? 1973
How many Clasifications of Vents are there? Name a vent that would fit in each category. 4- pOSITIVE OR nEGATIVE PRESSURE (IPPB, Iron lung) Power Source- LP10 Control System or Circuits- VDR Power Transmission & Conversion System- ICU vents – LTV 1200
This ventilator depends on compressed gas sources for power. Pneumatically powered ventilator
How do spring loaded bellows work as a volume-displacement device? The spring applies force to the bellows, causing the gas to be delivered to the patient.
Compare and contrast open and closed loop systems. Open loop: the ventilator doesn’t diverge from the settings. Closed loop: the ventilator compares the measured variables to those that were set and responds by adapting to meet patient needs.
What kind of driving mechanism uses many valves to detect and change volume delivered to the pt in seconds? Flow control valves
A pt on a volume vent suddenly sneezes while the vent is going through the inspiratory phase. The inspiration phase stops suddenly and the Vt delivered is .3 L less than what you set. What caused this inspiration to end prematurely? The ventilator pressure cycled and raised the peak airway pressure that the vent sensed during the sneeze.
If we set a PEEP for a pt on 10 cmH2O and after a breath hold, the vent says the pt has a total PEEP of 25 cmH2O? What does this tell us? Why would we want to know this? This shows the pt has an intrinsic PEEP of 15cmH2O. This is important to know if the pt is air trapping (COPD).
What makes the closed control system “intelligent”? The ventilator adjusts itself based on the value of measured results.
What is the best uses for a blower/compressor type of system? Transporting a patient or wall outlet failure.
What ventilator power source is the most used today? Combination Electrical/Pneumatic
What type of ventilator delivers a breath that is most like a natural breath? Negative pressure ventilator
If you are on a ventilator that is powered both electrically and pneumaticall, where are you most likely located? The intensive care unit (ICU).
If the Vt is set for 700 ml and there is a leak of 200 ml, how much is the patient receiving? What type of ventilator system can’t compensate for this loss? 500 ml, Open loop


Question Answer
What is ventilation? The process that moves gases between the external environment and the alveoli. It is the mechanism by which oxygen is delivered to the alveoli and carbon dioxide is carried from the alveoli to the atmosphere.
What is pressure gradient? The difference between two pressures.
Pressure gradient is responsible for what? Moving air in and out of the lungs and for maintaining the lungs in an inflated state.
Driving Pressure means what? The pressure difference between two points in a tube or vessel; it is the force moving gas or fluid through the tube or vessel.
Transairway pressure, Pta, (aka transrespiratory pressure) is what? The barometric pressure difference between the mouth pressure (Pm) and the alveolar pressure (Palv). Pta = Pm – Palv
+Pta happens when? Inspiration
-Pta happens when? Expiration
Transmural pressure, Ptm, is what? The pressure difference across the airway wall. Intra-airway pressure minus outside airway pressure. Ptm = Piam – Poaw
Transpulmonary pressure, Ptp, is what? The difference between the alveolar pressure and the pleural pressure. Ptp = Palv – Ppl
In the normal lung, Palv is always greater/less than the Ppl? Greater, this is what maintains the lungs in an inflated state.
Transthoracic pressure, Ptt, is what? The difference between the alveolar pressure and the body surface pressure. Ptt = Palv – Pbs
Transthoracic pressure is another way to view what other pressure? Transairway pressure
The flow of gas in and out of the lungs is caused by what? The Ptp & Pta changes that occur in response to the action of the diaphragm.
When stimulated to contract by the phrenic nerve, the diaphragm does what? Contracts, causing inspirations, and moves downward, causing the thoracic volume to increase and the intrapleural and intra-alveolar pressures to decrease (less than barometric pressure).
End-inspiration (pre-expiration), end-expiration (pre-inspiration) equilibrium is what? When the intra-alveolar pressure and the barometric pressure are equal.
The diaphragm during expiration does what? Relaxes and moves upward, causing the thoracic volume to decrease and the intrapleural and intra-alveolar pressure to increase.
The intrapleural pressure during normal inspiration and expiration is always more/less than the barometric pressure? Less.
At rest, the normal excursion of the diaphragm is what? 1.5cm
At rest, the normal intrapleural pressure change is what? 3cm – 6cm H2O
Deep inspiration can result in what? Diaphragm movement as much as 6 – 10cm, which causes intrapleural pressure to drop as low as 50cm H2O.
Forced expiration can result in what? Intrapleural pressure between 70 – 100cm H2O.
Pressure Force per unit area; mmHg or cmH2O
Flow Volume transfer per unit time; L/min, L/sec or mL/sec
Resistance Impedance to gas flow. When there’s resistance we increase pressure to breath. cmH2O/L/min or cmH2O/L/sec
Elastance Ability of a substance to return to resting shape after being distorted by an external force; recoiling force of the lungs. The higher the elastance the stiffer the lungs. Opposite of compliance.
Compliance – Cl = V/P The measure of ease of inflation of the lungs. Decreased compliance means stiffer lungs. Opposite of elastance.
Decreased Cl Stiff lungs, ie CF, scarring, etc.
Increased Cl Elastic lungs, ie emphysema, air trapping, etc.
Normal Cl 100 mL/cmH2O or 0.1 L/cmH2O
How is negative pressure, or tension, maintained between the parietal pleura and the visceral pleura? The lungs are fibrous and want to contract, while the thorax wants to expand. This causes the intrapleural pressure to remain negative.
Intrapleural pressure 1. Always negative, but, 2. Drops 1-2 mmHg during normal inspiration. 3. Increases 1-2 mmHg on normal expiration.
Diaphragm Primairy muscle of ventilation
Functional Residual Compacity – FRC The resting volume of our lungs.
Ventilation is opposed by: 1. Elastic resistance, ie lung tissue, lung compliance, surface tension. 2. Nonelastic resistance, ie airway resistance, mucous, bronchospasms, tube size.
Hooke’s Law Once the elastic limits of the lung unit are reached, little or no volume change occurs in response to pressure change. If the pressure increases and the elastic limits are exceeded the lung will rupture.
Normal volume-pressure curve 1. A shift to the right = decreased lung compliance. 2. A shift to the left = increased
Resistance How much pressure is needed to allow gas to flow. Determined by physical properties of the airway. Accounts for about 85% of nonelastic resistance to ventilation.
Raw (Airway resistance) = Raw = P/v, where v = flow measured in time
Normal Raw = 0.5 – 1.5 cmH2O/L/sec
Causes of increased resistance are 1. Increased gas viscosity/density, 2. Increased tube length, 3. Decreased tube radius (MOST important & has the GREATEST effect on resistance!)
Decreased tube radius A decrease by 1/2 increases resistance 16 times!
Other causes of increased resistance are, Secretions, inflammation, bronchospasm, tumors
Effects of airway resistance Uneven alveolar ventilation, V/Q abnormality, hypoxemia, increased WOB, increased O2 consumption, fatigue, hypoventilation
Treatment for airway resistance Bronchodilator, suctioning, remove obstruction, bronchial hygiene to mobilize secretions, low-density gas treatment
Types of gas flow through bronchial airway 1. Laminar 2. Turbulent 3. Tracheobronchial or Transitional Flow
Laminar Flow Streamlined, parallel gas flow that occurs at low flow rates & pressure gradients.
Turbulent Flow Random movement that occurs at high flow rates & pressure gradients, ie nose, pharynx, larynx, carina.
Tracheobronchial or Transitional Flow Both laminar and turbulent occurs where the airways branch.
Upper airways contribution to airway resistance 60%
Reynolds Number Used to determine the type of flow. It has no label, it is dimensionless. It is based on gas density, viscosity, velocity, and tube radius. If > 2000 = turbulent, < 2000 = laminar.
Poiseuille’s Law Shows what tube size does to flow and pressure. That flow is directly proportional to pressure and inversely proportional to r to the 4th power (r = radius).
Surface Tension Molecular cohesive force of molecules in a liquid-gas interface.
Surfactant Liquid film that lines the interior surface of the alveoli and creates surface tension.
Pulmonary Surfactant Molecules Hydrophobic end faces the gas, while the hydrophilic end faces the alveolar fluid.
Pulmonary Surfactant Produced and stored in the alveolar type II cells. Composed of phospholipids (about 90%) and protein. Phospholipid DPPC is the main tension-lowering chemical that has a hydrophobic & hydrophilic end.
Critical Opening(Closing) Pressure The high pressure (with little volume change) that is initially required to overcome the liquid molecular force during the formation of a new bubble – similar to the high pressure first required to blow up a new balloon.
Laplace’s Law – P = 2ST/r The distending pressure of a liquid bubble (not the alveolus) is influenced by (1) the surface tension of the bubble and (2) the size of the bubble itself.
Distending Pressure of liquid sphere Directly proportional to surface tension and inversely proportional to the radius. Otherwise, as surface tension increases the distending pressures increases. As the size increases the distending pressure decreases.
Alveolus Surface Tension Low tension when uninflated because of the ratio of surfactant to the alveolar area. Higher tension as inflated because the same surfactant has to cover more alveolar area!
Pulmonary Surfactant Deficiency – General Causes Acidosis, hypoxia, hyperoxia, atelectasis, pulmonary vascular congestion.
Pulmonary Surfactant Deficiency – Specific Causes ARDS, IRDS, pulmonary edema, pulmonary embolism, pneumonia, excessive pulmonary hydration or lavage, drowning, extracorporeal oxygenation.


Question Answer
Driving Pressure The pressure difference between 2 points in a tube or vessel. P1>P2
Transairway Pressure (Pta) The pressure difference between the mouth pressure and the alveolar pressure
Transthoracic Pressure (Ptp) The pressure difference between the alveolar and the body surface pressure
Transpulmonary Pressure (Ttp) The pressure difference between the alveolar and the pleural pressure
Surface tension Condition at the surface of a liquid in contact with a gas or another liquid which causes its’ surface to act as a stretched rubber membrane
Laplace’s Law The distending pressure of liquid sphere is: Directly proportional to the surface tension of the liquid and Inversely proportional tot he radius of the sphere
Three natural mechanisms of the body? Pore of Kohn, Canal of Lambert, and Peduluff Effect.
Poiseuille’s Law The speed of the flow of a fluid (gas or liquid) through a tube is directly proportional to the square of the diameter of the tube and the pressure upon the fluid and indirectly to the viscosity of the fluid and the length of the tube.
Static refers to… the study of matter at rest.
Dynamic Refers to… the study of matter in motion.
Lung Compliance, CL How readily the elastic force of the lungs accepts a volume of air.
Lung Compliance refers to… the “stiffness” of the lungs or “ease of filling”