Exam 2 Flashcards
________________ is simply the movement of air into and out of the lungs.
Spontaneous ventilation
What is this abbreviation?
Cdyn
Dynamic compliance
What is this abbreviation?
R
Resistance
What is this abbreviation?
PM
Pressure at the mouth
What is this abbreviation?
Pbs
Pressure at the body surface
What is this abbreviation?
Ppl
Intrapleural pressure
What is this abbreviation?
Cst
Static compliance
What is this abbreviation?
Pawo
Pressure at the airway opening; mouth pressure; mask pressure
What is this abbreviation?
Paw
Airway pressure
What is this abbreviation?
Palv
Alveolar pressure
Respiration is typically divided into what two categories?
- External respiration
- Internal respiration
For air to flow through a tube or airway, a _______________ must exist.
Pressure gradient
Air will always flow from the _____________ to the _________________.
Air will always flow from the high-pressure point to the low-pressure point.
A spontaneous breath is accomplished by contraction of the ______________________, which causes the expansion of the thorax.
Muscles of inspiration
Airway opening pressure is most often called __________________.
Mouth pressure or airway pressure
Define transpulmonary pressure.
The pressure difference between the alveolar space and the pleural space.
Define transthoracic pressure.
The pressure difference between the alveolar space or lung and the body’s surface.
What is the normal compliance is spontaneously breathing patients?
0.05 to 0.17 L/cmH2O or 150 to 170 mL/cmH2O
What is the normal compliance is intubated patients?
Males: 40 to 50 mL/cmH2O, up to 100 mL/cmH2O
Females: 35 to 45 mL/cmH2O, up to 100 mL/cmH2O
The compliance of any structure can be described as _____________________.
The relative ease with which the structure distends.
________________ is a measurement of the frictional forces that must be overcome during breathing.
Resistance
Ventilating pressures are commonly measured in what?
Centimeters of water
Define transairway pressure.
The pressure difference between the airway opening and the alveolus.
What is normally the intrapleural pressure at end expiration during spontaneous breathing?
-5 cmH2O
Define transrespiratory pressure.
The pressure difference between the airway opening and the body surface.
What are the two components of transrespiratory pressure?
- Transthoracic pressure
- Transairway pressure
Normally, what two types of forces oppose inflation of the lungs?
Elastic forces and frictional forces
Airway resistance is increased when __________________.
An artificial airway is inserted
The diameter of the airway lumen and flow of gas into the lungs can decrease as a result of:
- Bronchospasm
- Increased secretions
- Mucosal edema
- Kinks in the endotracheal tube
What involves the change of oxygen and carbon dioxide between an organism and its environment?
Respiration
To achieve a maximal inspiration, ____________________ must be used to compress the thorax.
Accessory muscles of inspiration
Explain external respiration.
It involves the diffusion and carbon dioxide between the alveoli and the pulmonary capillaries.
Internal respiration occurs at the _______________________________
Cellular level and involves the exchange of oxygen and carbon dioxide between the systemic capillaries and the cells of the body.
During spontaneous inspiration, contraction of the inspiratory muscles causes enlargement of the thorax resulting in a decrease in _____________________.
Intrapleural pressure and alveolar pressure
Gas flows out of the lungs during expiration because…
The pressure in the alveoli is higher than the pressure at the airway opening.
What is the atmospheric pressure at sea level?
760 mmHg or 1034 cmH2O
Body pressure is equal to zero unless:
The person is placed in a pressurized chamber or negative pressure ventilation
____________________ is the pressure in the potential space between the parietal and visceral pleurae.
Intrapleural pressure
What is the normal intrapleural pressure at the end of expiration?
-10 cmH2O
What is alveolar pressure during spontaneous inspiration?
About -1 centimeters of water
What is alveolar pressure during spontaneous expiration?
About +1 centimeters of water
__________________ represents the pressure that must be generated to overcome resistance to gas flow in the airways.
Transairway pressure
Air can be trapped in the lungs during mechanical ventilation if not enough time is allowed for exhalation. What is the most effective way to prevent this?
Monitor the pressure in the ventilator circuit at the end of exhalation.
What does it mean if no extrinsic PEEP is added and the baseline is greater than zero?
Air trapping or auto-PEEP is present
_______________ reflects the effect of the elastic recoil on the gas volume inside the alveoli and any pressure exerted by the volume in the ventilator circuit that is acted upon by the recoil of the plastic circuit.
Plateau pressure
When is plateau pressure measured?
After a breath has been delivered to the patient and before exhalation begins
To obtain the plateau pressure, the ventilator operator normally selects a control marked ___________________.
“Inflation hold” or “Inspiratory pause”
During positive pressure ventilation, the manometer rises progressively to a _______________________.
Peak pressure
Peak pressure is also called what?
- Peak Inspiratory Pressure
- Peak Airway Pressure
Sometimes the baseline pressure is higher than zero, such as when the ventilator operator selects a higher pressure to be present at the end of exhalation. What is this called?
Positive End-Expiratory Pressure (PEEP)
______________ is the highest pressure recorded at the end of inspiration.
Peak pressure
When does intrinsic peep usually occur?
When a patient does not have enough time to exhale completely before the ventilator delivers another breath
What are the three basic methods that have been developed to mimic or replace the normal mechanisms of breathing?
- Negative pressure ventilation
- Positive pressure ventilation
- High-frequency ventilation
The product of compliance and resistance is called a ________________.
Time constant
Because intrapleural pressures are often hard to obtain in a patient, what is typically used instead?
Esophageal pressure
Alveolar pressure is also called __________________.
Intrapulmonary pressure or lung pressure
Alveolar pressure normally changes as the ____________________ changes.
Intrapleural pressure
During spontaneous inspiration, what is the alveolar pressure?
-1 centimeters of water
During spontaneous expiration, what is the alveolar pressure?
+1 centimeters of water
Which pressure gradient represents the pressure required to expand or contract the lungs and the chest wall at the same time?
Transthoracic pressure
_________________ is the pressure required to maintain alveolar inflation and is therefore sometimes called alveolar distending pressure.
Transpulmonary pressure
___________________ is the pressure gradient required to produce flow in the conductive airways.
Transairway pressure
All modes of ventilation increase _______________________ during inspiration, by either decreasing pleural pressure or increasing alveolar pressure by increasing pressure at the upper airway.
Transpulmonary pressure
Which pressure is used to describe the pressure required to inflate the lungs during positive pressure ventilation?
Transrespiratory pressure
Frictional forces are the result of what two factors?
The resistance of the tissues and organs as they become displaced during breathing and the resistance to gas flow through the airways
Define elastance.
The tendency of a structure to return to its original form after being stretched or acted on by an outside force.
______________ is about the normal amount of pressure lost to airway resistance with a proper-sized endotracheal tube in place.
-5 cmH2O
What is the transairway pressure calculation?
Pta = PIP - P plat
An inspiratory time less than _____ time constants may result in incomplete delivery of the tidal volume.
Three
How may time constants should be considered for the inspiratory time, particularly in pressure ventilation, to ensure adequate volume delivery?
Five time constants
An expiratory time less than ______ may lead to incomplete emptying of the lungs.
Three
______________ attempts to mimic the function of the respiratory muscles to allow breathing through normal physiological mechanisms.
Negative Pressure Ventilation (NPV)
_____________ occurs when a mechanical ventilator is used to deliver air into the lungs by way of an endotracheal tube or positive pressure mask.
Positive Pressure Ventilation
The power used by a mechanical ventilator to generate a positive or negative pressure may be provided by ________________________.
An electrical or pneumatic (compressed gas) source
Pneumatically powered ventilators are classified according to _____________________.
The mechanism used to control gas flow
Most ventilators that are not microprocessor controlled are called _____________________________.
Open-loop systems
Which ventilator type delivers a set volume and does not measure or change?
Open-loop systems
Explain closed-loop systems
Often described as “intelligent” systems because they compare the set control variable with the measured control variable, which allows the ventilator to respond to changes in the patient’s conditions
______________ is when the operator selects a minimum minute ventilation setting that is lower than the spontaneous minute ventilation.
Mandatory minute ventilation
_________________ is located on the surface of the ventilator and is monitored and set by the ventilator operator.
The control panel, or user interface
__________________ is a series of tubes that allow gas to flow inside the ventilator and between the ventilator and the patient.
A pneumatic circuit, or pathway
Explain the internal and external pneumatic circuit.
The gas first is directed from the generating source inside the ventilator through the internal pneumatic circuit to the ventilator’s outside the surface. Gas then flows through an external circuit, or patient circuit into the patient’s lungs. Exhaled gases through the the expiratory limb of the external circuit and to the atmosphere through an exhalation valve.
If the ventilator’s internal circuit allows the gas to flow directly from its power source to the patient, the machine is called _____________________.
Single-circuit ventilator
Most ICU ventilators manufactured today are classified as what type of ventilators?
Single-circuit ventilator
Explain double circuit ventilators.
The primary power source generates a gas flow that compresses a mechanism such as a bellows or “bag-in-chamber”
The external pneumatic circuit, or patient circuit, connects the ventilator to the ____________________.
Patient’s artificial airway
_____________ is a mechanical device that produces gas flow to the patient.
Drive mechanism
What are the major components of mechanical ventilator?
- High-pressure gas source
- Control panel to establish the pressure and pattern of gas flow delivered by the machine
- Control system that interprets the operator’s settings and produce and regulates desired output
The controls set by the ventilator operator are considered part of the:
User interface
The gas-conducting tubes that carry gas from the ventilator to the patient are referred to as the:
Patient circuit
A ventilator in which the gas that enters the patient’s lungs is also the gas that powers the unit is referred to as a:
Single-circuit ventilator
The equation of motion describes the relationships among _________________________.
Pressure, volume and flow during a spontaneous or mechanical breath
When the ventilator maintains the pressure waveform in a specific pattern, the breathing is described as ___________________.
Pressure-controlled
What is the equation of motion for the respiratory system?
Pvent + Pmuscles = Elastance x volume + resistance x flow
What two factors determine the way inspiratory volume is delivered?
- Structural design of the vent
- Vent mode set by clinician
The primary variable the ventilator adjusts to achieve inspiratory pressure is called the ___________________.
Control variable
The ventilator can only control one variable at a time. True or False
True
What are the most commonly used control variables?
Pressure and volume
What is perhaps the single most important function a ventilator accomplishes?
Delivery of an inspiratory volume
When a ventilator remains the same waveform in a specific pattern
Volume-Controlled
When the pressure, volume, and flow waveforms are affected by changes in lung characteristics, the ventilator can control the ventilatory cycle and is described as delivering a breath as _______________________.
Time-controlled ventilation
What type of variable begins inspiration?
Trigger variable
Which variable limits the value of pressure, volume, flow or time during inspiration?
Limit variable
Which variable ends expiration?
Cycle variable
Which variable establishes the baseline during expiration before inspiration is triggered?
Baseline variable
__________ is usually identified as the baseline variable.
Pressure
The mechanism the ventilator uses to begin inspiration is the _________.
Triggering mechanism
What is it called when the ventilator initiates a breath after a set time?
Time triggering
Sometimes clinicians may say that a patient “is being controlled” or “is in control mode” to describe what type of individual?
Patient who is apneic, sedated or paralyzed and makes no effort to breathe.
What happens when the ventilator detects changes in pressure, flow or volume?
A patient-triggered breath occurs
What are common patient-triggered mechanisms?
Pressure and flow
What is the sensitivity level for pressure triggering usually set at?
About -1 centimeters of water
What happens if the sensitivity level is set incorrectly?
The ventilator may not be sensitive enough to the patient’s effort and the patient will have to work too hard to trigger the breath.
What happens if the ventilator is too sensitive?
It can auto-trigger. The machine triggers a breath without the patient making an effort.
___________ occurs when the ventilator detects a drop in flow through the patient circuit during exhalation.
Flow triggering
________ occurs when the ventilator detects a small drop in volume in the patient circuit during exhalation.
Volume triggering
Inspiration is the time from __________ to _________.
The beginning of inspiratory flow to the beginning of expiratory flow.
________ allows pressure to rise to a certain value but no exceed it.
Pressure limiting
How do you prevent excessive pressure for entering the patient’s lungs?
Set a high-pressure limit control. Excess pressure will be vented through a spring loaded pressure release or pop off. Excess gas pressure will be released into the room
If gas flow from the ventilator to the patient reaches does not exceed a maximum value before the end of inspiration. What is this type of ventilator?
Flow limited
What is the maximum safety pressure typically set at?
10 cmH20 above the average PIP
Ventilator manufacturers usually set internal maximum safety pressure at what?
120 centimeters of water
The variable that a ventilator uses to end inspiration is called _______________.
Cycling mechanism
Does setting an inspiratory pause extend inspiratory time or flow?
TIME
The volume of gas that leaves the ventilator’s outlet is the volume that enters the patient’s lungs. T or F?
FALSE!
The actual volume delivered to a patient can be determined by…..
Measuring the exhaled volume at the ETT or TT.
A breath is considered ________ if the inspiratory phase end when a predetermined time has elapsed.
Time cycled
On a pressure-time basis waveform, the curve during the expiratory phase does not return to the baseline as rapidly it normally would. This may be a result of:
An obstruction in the expiratory line
How would you determine if a leak exist on a vent?
PIP will be lower than previous inspiratory pressure and low-pressure alarm may be activated
In most adult ventilator circuits, about how much of gas is lost to tubing compressibility for every 1 cmH20 that is measured by the airway pressure sensor?
1-3 mL of gas
Manufacturers use various name to describe the maximum pressure control such as the ________________________.
Peak/maximum pressure
Normal pressure limit
Pressure limit
High-pressure limit
Upper pressure limit
The inspiratory phase of a volume-cycled breath is terminated when the _______________.
Set volume has been delivered
What is the most common cycling mechanism in the pressure support mode?
Flow cycling
With this type of cycled ventilation, the ventilator cycles into the expiratory phase once the flow has decreased to a predetermined value during inspiration.
Flow-cycled ventilation
With this type of cycled ventilation, inspiration ends when a set pressure threshold is reached at the mouth or upper airway.
Pressure-cycled ventilation
What is designed to maintain air in the lung at the end of inspiration, before the exhalation valve opens?
Inflation hold
What is used to increase peripheral distribution of gas and improve oxygenation?
Inspiratory pause
The expiratory phase encompasses the period from ___________________________.
The end of inspiratory to the beginning of the next breath
What can occur if expiratory time is too short?
Air trapping
The baseline variable is the parameter that is generally controlled during…
Exhalation
Baseline pressure can be zero, which is also called _________________
Zero end-expiratory pressure
The pressure level from which a ventilator breath begins is called _______________________.
Baseline pressure
What is it called when the baseline is above zero?
PEEP
______________ push air into the lungs and pull it back at extremely high frequencies.
Oscillators
During APRV, what two settings are used?
Time 1 controls the time high pressure is applied and Time 2 controls the release time or the time low pressure is applied
What is the purpose of expiratory holds?
To measure pressure associated with air trapped in the lungs at the end of expiration.
An accurate reading of end-expiratory pressure is impossible to obtain if a patient is…..
Breathing spontaneously
What are the two methods of applying continuous pressure to the airways?
CPAP and PEEP
_________ becomes baseline variable during mechanical ventilation.
PEEP
With ___________, the inspiratory positive airway pressure is higher than the expiratory positive airway pressure
Bilevel Positive Pressure - BIPAP
What are the two types of mechanical ventilation breaths?
Spontaneous breaths & mandatory breaths
Which variables are the main variables the ventilator adjusts to produce inspiration?
Control variables
Phase variables control what four phases of a breath?
- Beginning inspiration
- Inspiration
- End Inspiration
- Expiration
What is the primary purpose of ventilation?
Maintain homeostasis
When is mechanical ventilation indicated?
When a person cannot achieve an appropriate level of ventilation to maintain adequate gas exchange and acid-base balance.
Which of the following can compromise oxygen delivery to the tissues?
Anemia and reduced cardiac output
Hypoxemic respiratory failure is the result of what?
Severe V/Q mismatch, diffusion defects, right-to-left shunting, alveolar hypoventilation, aging, inadequate inspired oxygen
How can hypoxemic respiratory failure be treated?
Supplemental O2 or in combination with CPAP or PEEP
Which following types of disorders lead to pump failure?
- CNS disorders
- NMD
- Disorders that increase WOB
What are early indicators of hypoxia?
Tachycardia and tachypnea
In otherwise normal individuals, PaCO2 greater than __________ has a CNS depressant effect which reduces respiratory drive and ventilation
70
What is a good indicator of airway resistance and patient’s ability to maintain airway patency?
PEF
What is the acceptable range for PEF?
350-600 L/min
What are the most obvious indications for invasive ventilation?
Apnea and impending respiratory failure
NIV is the treatment of choice for ___________________.
Acute on chronic respiratory failure unless cardiovascular instability is also a factor.
What are the two types of noninvasive positive pressure ventilation?
CPAP and Noninvasive positive pressure ventilation
Breaths for which the ventilator controls the timing, tidal volume or the inspiratory pressure
Mandatory breaths
Breath delivery and modes are determined by:
- Type of breath: Mandatory, spontaneous, assisted.
- Target controlled variable: Pressure and volume
- Timing of breath delivery: CMV, IMV, CSV
What is the weaning vent mode that’s most preferred?
SMIV
Which vent mode would be more comfortable for spontaneously breathing patients?
Pressure-controlled ventilation
When the breaths are patient triggered during CMV, the breaths are described as _______________.
Assisted ventilation
When the breaths are time triggered during CMV, the breaths are described as _______________.
Controlled ventilation
When is the only time controlled ventilation is appropriate?
Only when the patient cannot make an effort to breathe
