Respiratory Therapy - Mechanical Ventilation
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Define compliance using a mathematical equation.
Define VD/VT using a mathametical equation.
(PaCO2 - PECO2)/PaCO2
Define minute ventilation using a mathmatical equation.
VE = VT X RR
Define alveolar ventilation using a mathematical equation.
(VT - VD) X RR
State the 13 physiological effects of positive pressure ventilation.
- Increases Mean Airway Pressure
- Increases Mean Intrathoracic Pressure
- Decreases Venous Return
- Decreases Cardiac Output
- Increases Intracranial Pressure
- Decreases Urinary Output
- Decreases Work of Breathing
- Mechanical Bronchodilation
- Increases Deadspace Ventilation
- Increases Intrapulmonary Shunting
- Manipulation of Level of Ventilation
- Effects on GI (Increases Gastric Secretions)
- Psychological Effect (Insomnia, Anxiety, Frustration, Depression, Apprehension, Fear)
Your 120 pound (IBW) patient has a tidal volume of 500 ml and a delivery rate of 12 bpm. Calculate the patient's minute ventilation.
12 X 500 = 6.000
Your 120 pound (IBW) patient has a tidal volume of 500 ml and a delivery rate of 12 bpm. Calculate the patient's alveolar ventilation.
(500 - 120) 12 = 4.56 L/m
Give the normal value for pulmonary shunt.
2 - 5%
Give the normal value of BUN.
Give the normal value of creatinine.
0.7 - 1.5
What are the 4 variables that a ventilator uses to end inspiration?
Define mean airway pressure.
The average amount of air in the airway during respiratory cycle.
If you have the following parameters calculate the total minute ventilation.
VT = 700
Mode = SIMV
Rate = 10
Rate Spt = 4
VT Spt = 400
10 X 700 + 4 X 400 = 8.6 L
When CPAP is in use, the total amount of the work of breathing is produced by the _________.
Interpret the following blood gas:
pH = 7.48
PaCO2 = 30 mmHg
PaO2 = 79
HCO3 = 26
Uncompensated respiratory alkalosis w/ mild hypoxemia
Mechanical ventilation is used to support ____a____ and one of its most frequent uses is an acute care setting is to manage conditions associated with ____b____.
- a) hypoventilation
- b) post anesthesia recovery
Poiseuille's Law demonstrates that the work of breathing increases 16 times when the radius of an airway is reduced by _________ of its original size.
During mechanical ventilation rounds, you are trending a patient's dynamic compliance measurements. The primary purpose of this procedure is to monitor changes in the patient's:
Dr. Abel asks you to recommend a method for assessing the elastic properties of a patient's lungs. You would suggest measuring the:
The criticalrange of dynamic compliance is between ____a____ and this measurement is used to evaluate the condition of a patient's ____b____.
- A) 30 and 40 mL/cm H2O
- B) airways
The pulmonary measurements for an intubated post-operative patient are below:
Corrected Tidal Volume = 900 mL
PEEP = 5 cm H2O
Peak Airway Pressure = 60 cm H2O
Plateau Pressure = 36 cm H2O
Based on this information, the dynamic compliance is about:
16 mL/cm H2O
The critical range of static compliance is between ____a____ and this measurement is used to evaluate that condition of a patient's ____b____.
- A) 40 and 60 mL/cm H2O
- B) lung parenchyma
The pulmonary measurements for a patient being treated for a 40% tension pneumothorax are below:
Corrected Tidal Volume = 750 mL
PEEP = 8 cm H2O
Peak Airway Pressure = 74 cm H2O
Plateau Pressure = 49 cm H2O
Based on this information, the static compliance is about:
18 mL/cm H2O
The volume of air in the conducting airways is known as ____a____ deadspace and under normal conditions it can be estimated to be about ____b____ ml per pound of ideal body weight.
Dr. Plauche asks you to evaluate his patient in the CCU who has developed oxygenation failure secondary to congestive heart failure. In assessing the patient, you would expect to observe all of the following clinical signs except:
During spontaneous breathing, alveolar pressure is _________ barometric pressure at end-inspiration.
During positive pressure ventilation, the pressure in the airway, alveoli, and pleural space:
You are assessing the condition of a 20 year-old patient with status asthmaticus who is being mechanically ventilated. You note that the peak inspiratory pressures as well as the patient's work of breathing have steadily increased over the last three hours. You would initially check the patient's:
Ms. Warren has the following laboratory results: prothrombin time: 5 sec., bilirubin level: 60 mg/L, albumin level: 13 g/L. This finding suggests _________ impairment.
In reviewing Mr. Johnason's chart, you note that he is receiving total parenteral nutrition (TPN). This means that he is getting a complete nutritional program provided by any route other than:
Patients with neurological impairment due to ventilatory and oxygenation failure will usually describe their headache as _________ in the head.
The ventilator is a _________ controller if the pressure waveform does not change when airflow resistance and compliance are changed.
Th eventilator is a volume controller if the _________ is measured and used as a feedback signal to control the volume delivered.
Heated wire grids, venture pneumotachometers and vortex sensors are devices used to measure the inspiratory:
When the ventilator delivers a breath every 5 seconds, it is operating under the ____a____ mode and the breaths are considered ____b____.
- A) control
- B) time-triggered
In order to control the I:E ratio during mechanical ventilation, a _________ cycled mechanism is most effective.
The term "triggered" describes the mechanism by which ventilator:
begins the inspiratory phase
You are asked to calculate the VD/VT for Mr. Goosby, a 19-year-old patient who is being mechanically ventilated following a motor vehicle crash. The following information is available from teh chart:
PaO2 = 64 mmHg
PaCO2 = 60 mmHg
PECO2 = 18 mmHg
VE = 16 L
FIO2 = 40%
His deadspace percentage is:
A VD/VT ratio of a 19-year-old patient who is being mechanically ventilated following a motor vehicle crash, is 70%. Th edifferential diagnosis may include:
The pressure gradient that must be generated between the airway opening and alveoli in order to produce inspiratory flow is known as:
PEEP offers which of the following physiological benefits?
- Increased functional residual capacity
- Decreased alveolar distending pressures
- Decreased work of breathing
Patients with ____a____ are least likely affected by the hemodynamic effects of PEEP because the compliance of the patients is very ____b____.
Mrs. Smith is being ventilated with assist control mode at a rate of 10 breaths per minute. Under this setting, a ventilator triggered breath will be delivered every _________ seconds if the patient becomes apneic.
Mechanical ventilation is initiated with pressure support of 15 cm H2O. Which of the following parameters would you monitor in order to ascertain that the pressure support level is adequate?
- Spontaneous Tidal Volume
- Spontaneous Respiratory Rate
- Arterial Blood Gas Results
Dr. Goodnow asks you to initiate mechanical ventilation on a patient with myasthenia gravis. In order to obtain an I:E ration that is near physiologic, you would adjust the ventilaatior setting until an I:E ratio is about _________ is reached.
How do you assess adequacy of ventilation
Decreas in VA =
- Increase in PaCO2
Increase in VA =
- Decrease in PaCO2
What factors affect VA?
- Underestimation of tidal volume
- Improper setting of ventilator controls
- Leaks in the circuit
- Tubing and ventilator compliance
- Measuring tidal volume
What are the clinical signs of O2 failure and hypoxia?
When is static compliance measured?
When no air flow is present.
State the static compliance equation.
(Corrected Tidal Volume)/(Plateau Pressure - PEEP)
What is the critical range for static compliance?
40 - 60 mL/cm H2O
When is dynamic compliance measured?
When air flow is present.
State the dynamic compliance equation.
(Corrected Tidal Volume)/(PIP - PEEP)
What is the critical range for dynamic compliance?
30 - 40 mL/cm H2O
State the equation for corrected tidal volume.
Exp VT - (PIP - PEEP)3
What could be the cause of both peak and plateau pressures sincreasing?
- Pulmonary edema
- Tension pneumothorax
- Splinting-thoracic injury
- Bronchial intubation
Why could peak pressure be increased?
- Increased peak flow
- Small or obstructed ET tube
- Mucus plug
What clincal conditions decrease static compliance?
- Tension Pneumothorax
- Retained secretions
What clinical conoditions decrease dynamic compliance?
- Kinking of the ET tube
- Airway obstruction
What 5 mechanisms lead to ventilatory failure?
- Persistent V/Q mismatch
- Persistent intrapulmonary shunting
- Persistent diffusion defect
- Persistent reduction of PiO2
How can oxygenation failure be diagnosed?
- Severe hypoxemia
- Patient does not respond to moderate to high levels of supplemental oxygen
- Hypoxia can occur with a normal PaO2
What is MAWP directly related to?
- Inspiratory time
What is the amount of pressure transmitted to intrathoracic space dependent on?
- Lung compliance
- Thoracic compliance
If you have a decreased lung compliance (stiff lung) is the amount of pressure transmitted increased or decreased?
If you have a decrease in compliance of the thorax (stiff thorax) is the amount of pressure transmitted greater or lower?
Why is venous return decreased due to positive pressure ventilation?
- Increase in intrathoracic pressure
- Compression of the vessels
- Decrease in venous flow to the right side of the heart
Why is cardiac output decreased due to positive pressure ventilation?
- Venous return is decreased
- A reduction in stroke volume occurs
- A reduction of cardiac output and pulmonary blood flow occurs
Why is intracranial pressure increased due to positive pressure ventilation?
- Venous return is decreased
- Blood will pool in periphery and cranium
- An increase of volume in cranium will occur
Why is urinary output decreased due to positive pressure ventilation?
- Cardiac output decreases
- Blood flow decreases
- Filtration rate is altered
- Urine formation is diminished
Why is work of breathing decreased due to positive pressure ventilation?
Force for ventilation is provided by the ventilator
How is mechanical bronchodilation produced due to positive pressure ventilation?
Positive pressure causes mechanical dilation of all conducting airways
Why is deadspace ventilation increased due to positive pressure ventilation?
- Positive pressure distends conducting airways
- It inhibits venous return
- Portion of the VT that is deadspace increases
- Alteration in distribution of ventilation occurs
What is the normal VD/VT ratio?
0.20 to 0.40
What will mechanical ventilation cause VD/VT ratios to increase to?
0.40 to 0.60 in the normal individual
Why is intrapulmonary shunt increased due to positive pressure ventilation?
- With positive pressure ventilation, gas distribution and pulmonary perfusion is altered
- Ventilation to gravity depended area decreases
- Perfusion to these areas increases
Mecanical ventilation may increase shunt fraction to approximately what percent in a normal adult?
Manipulating the level of ventilation can cause:
- Hyperventilation or hypoventilation by innappropriate settings
- RR, VT, IT, and flow can be manipulated
Why is GI effected due to positive pressure ventilation?
Stress from positive pressure ventilation leads to and increase in gastric secretion and results in stress ulcers.
What is indicated with an increase in BUN?
An increase in creatinine indicated what?
What does TPN stand for?
Total Parenteral Nutrition
What is oliguria?
Decreased Urine Output
What values define urine output?
- U.O. of < 400 mL in 24 hours
- U.O. < 160 mL in 8 hours
What is ventilatory work dependent on?
- Load - Pressure required to deliver VT
- Elastic Load - Volume/Compliance
- Resistance Load - RAW and Iflow
What classifies a mechanical ventilator?
- Input Power
- Drive Mechanism
- Control Circuit
- Control Variables
- Phase Variables
- Output Waveforms
- Alar Systems
What are the types of input power?
- Pneumatic - 50 psi compressed gas
- Electric - Uses electricity
- Combined - Uses both pneumatic and electric
What do drive mechanisms provide?
Mechanical force that produces the flow of gas necessary for delivery of VT
The type of drive mechanism determines chaaracteristic flow and pressure patterns. The types of drive mechanisms are:
- Reducing Valve
What does a control circuit do?
It controls venilator drive mechanism or output control valve.
What kind of control circuits are there?
What does the trigger variable do?
It determines the start of inspirations
What does the limit do?
The limit does not allow variable to rise above a preset value.
What is the cycle?
The method the ventilator uses to end inspiration.
What is the baseline?
The variable that is controlled during the expiratory phase/expiratory time
WHat are the types of alarm systems?
- Input Power Alarms
- Control Circuit Alarms
- Output Alarms
List the modes of mechanical ventilation?
What does the ventilator provide to the patient in spontaneous mode?
- Flow to patient in a timley manner
- Flow adequate to meet patient's inspiratory needs
- Provides adjunct modes like PEEP
What is PEEP?
Increased baseline pressure above zero.
What are the indications for PEEP?
- Intrapulmonary shunting and refractory hypoxemia
- Decreased FRC and lung compliance
Complications of PEEP
- Decreased venous return
- Increased ICP
- Alterations of renal functions and H2O metabolism
When should CPAP be used?
- On a spontaneously breathing patient
- Intrapulmonary shunting and refractory hypoxemia
- Decreased FRC and lung compliance
- On a patient with adequate lung function
How is CPAP applied to patients?
- Adult - mask, ET, nasal mask
- Neonate - nasal method
List the indications for BiPAP?
- Prevent intubation of end-stage COPD patients
- Support patients in chronic ventilatory failure
- Restrictive chest wall disease, neuromuscular disease and nocturnal hypoventilation
Where should BiPAP settings be set to start with?
- IPAP - 8 cm H2O
- EPAP - 4 cm H2O
- These are increased by 2 cm H2O increments at a time
BiPAP's volume delivered is ovtained by:
- Increase IPAP level
- Decrease EPAP level
- Increase compliance
- Decrease air flow resistance
How does a CMV work?
- It delivers a preset tidal volume and respiratory rate
- The machine is responsible for initiation and delivery of each tidal volume
- Total minute ventilation determined by machine
List the indications for CMV.
- Patient fights ventilator
- Seizure activity or tetnus
- Complete rest for patient
- Crushed chest injury
What are the hazards of CMV?
- - These are caused by disconnect or the ventilator failling to operate.
What does assist control do?
- Sets a rate and tidal volume
- Patient can initiate inspiratory phase
- Minute ventilation may increase from preset
What is the indication for assist control
Full ventilatory failure
What does IMV do?
- Delivers a control breath
- Allows patient to breath spontaneously at any tidal volume
- Allows for breath stacking
What does SIMV do?
- Ventilator delivers a control breath
- Patient breathes spontaneously at any tidal volume
- Mandatory breaths are synchronized with patients spontaneous breath
- Avoids breath stacking
What does MMV do?
- A minimum minute volume is set
- Patient receives volume by breathing totally spontaneously, being mechanically ventilated, combination of spontaneous and mechanical ventilation.
What does PSV do?
- Lowers work of spontaneous breathing and augments patient's spontaneous tidal volume
- Patient establishes frequency, inspiratory flow, and inspiratory time
What does PCV do?
- It makes all breathes time or patient triggered, pressuer limited and time cycled
- Minimizes PIP while maintaining adequate oxygenation and ventilation
What does APRV do?
It provides 2 levels of CPAP and allows spontaneous breathing at both levels.
What does IRV do?
- Lengthens inspiratory time and shortens expiratory time
- 2:1 to 4:1
- It is used with PCV
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