Ch. 11 Ventilator Management Flashcards by Kiesha Alexis

The following information has been obtained from a ventilator patient

Peak inspiratory pressure - 42 cm H2O
Plateau pressure - 27 cm H20
VT - 500 mL
PEEP- 6 cm H2O

On the basis of these data, the patient’s static lung compliance (CL) is approximately which of the following?

A. 18 mL/cm H2O
B. 24 mL/cm H2O
C. 31 mL/cm H2O
D. 37 mL/cm H2O

24 mL/cm H2O

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A patient is receiving volume-controlled ventilation in the assist-control (A/C) mode, and the I:E ratio alarm is sounding. Which control adjustment would correct this problem?

A. Decrease the flow rate.
B. Increase the VT.
C. Increase the respiratory rate.
D. Increase the flow rate.

Increase the flow rate.

The I:E time alarm is triggered when the ventilator settings are delivering ventilator breaths with an inverse I:E ratio or when the inspiratory time is longer than the expiratory time. The potential hazards of an inverse I:E ratio include decreased cardiac output, barotrauma, and intrinsic PEEP. To return the I:E ratio to a normal condition of 1:2 or 1:3, increase the inspiratory flow. If the flow is increased, the VT is delivered faster, which results in a decreased inspiratory time.

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Mechanical ventilation can lead to which of the following complications?
1. Increased renal output
2. Barotrauma
3. Increased cardiac output

2 only

Complications of mechanical ventilation include barotrauma, decreased renal output, decreased venous blood return, and decreased cardiac output. Positive pressure ventilation results in decreased venous return and cardiac output by compressing the blood vessels returning blood to the heart (superior and inferior vena cavae). Renal output may decrease because of hypotension resulting from decreased cardiac output and an increased production of antidiuretic hormone (ADH). As venous blood returns to the heart, pressure receptors in the right atrium sense the drop in blood return and send a signal to the hypothalamus. The pituitary gland is then stimulated to release more ADH, which causes the kidneys to hold on to more fluid to increase the fluid level in the blood. It is one way the body compensates for hypovolemia.

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Static CL will decrease as a result of which of the following?

A. Bronchospasm
B. Mucosal edema
C. Atelectasis
D. Bronchial secretions

Atelectasis

Static lung compliance is the measurement of how easily the lung is stretched. The higher the compliance, the more easily it stretches. The lower the lung compliance, the less easily it stretches or the stiffer and harder it is to ventilate. Conditions that decrease compliance include atelectasis, pulmonary edema, pulmonary fibrosis, consolidation, pneumonia, pleural effusion, ARDS, and pneumothorax. The stiffer or less compliant the lung is, the more pressure is needed to ventilate the lung, which is observed by increasing peak and plateau pressures.

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These data have been collected from a sedated, paralyzed patient whose ventilator is in A/C mode.
VT 600 mL
Rate 15/min
FiO2 0.45
ABGs: pH -7.50
PaCO2 - 30 mm Hg
PaO2- 98 mm Hg

To increase this patient’s PaCO to 40 mm Hg, the venttilator rate should be adjusted to what rate?

A. 10/min
B. 11/min
C. 12/min
D. 13/min

11/ min

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The following data have been collected from a patient receiving volume-controlled ventilation in the A/C mode.

VT 500 mL
Rate 10/min
FiO2 0.50
PEEP 5 cm H2O
ABGs: pH 7.44
PaCO2 - 42 mm Hg
PaO2 58 mm Hg

Based on this information, the respiratory therapist should recommend which of the following ventilator changes?

A. Increase FiO2 to 0.70.
B. Increase VT to 600 mL.
C. Increase PEEP to 10 cm H2O.
D. Initiate CPAP at 4 cm H2O and an FiO2 of 0.50.

Increase PEEP to 10 cm H2O.

This blood gas indicates normal ventilation with hypoxemia. To increase the PaO2 either the FiO2 or PEEP must be increased. Since the choice to increase the FiO2 is to 0.70, which is excessive and may result in O2 toxicity, the better choice is to increase the PEEP level

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A patient being mechanically ventilated in the A/C mode at a rate of 12/min is triggering the ventilator at a rate of 34/min. The patient is anxious and agitated and has the following arterial blood gas (ABG) results:

pH 7.55
PaCO2 - 25 mm Hg
PaO2 - 96 mm Hg
HCO3 25 mEq/L
BE +1

Which of the following medications should the respiratory therapist recommend at this time?

A. Albuterol (Proventil)
B. Nitroprusside (Nipride)
C. Theophylline (Aminophylline)
D. Midazolam (Versed)

Midazolam (Versed)

It is important to check the PaO2 when the blood gases indicate hyperventilation (PaCO2 ,35 mm Hg). Hypoxemia results in hyperventilation. That is not the case in this scenario. The question states the patient is anxious and agitated, which is the cause of the hyperventilation. The patient will benefit from sedation, and a common sedative for ventilator patients is Versed.

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A 5’7”, 65-kg (143 lb) female patient arrives in the emergency department intubated and being manually ventilated with 100% O2. Paramedics state she was discovered unconscious at home with an empty pill bottle by her side. The respiratory therapist should select which of the following ventilator settings to best ventilate this patient?

A. Mode: AC, VT: 500 mL, rate: 12, FiO2: 1.0, PEEP: 5
B. Mode: Control, VT: 550 mL, rate: 12, FiO2: 0.60, PEEP: 10
C. Mode: SIMV, VT: 700 mL, rate: 6, FiO2: 1.0, PEEP: 5
D. Mode: SIMV, VT: 650 mL, rate: 12, FiO2: 0.80, PEEP: 10

Mode: AC, VT: 500 mL, rate: 12, FiO2: 1.0, PEEP: 5

Typically, use these initial ventilator settings on the exam:
Mode: A/C or SIMV
VT: 6 to 8 mL/kg of ideal body weight; RR: 10 to 16/min FiO2: Level prior to initiation of ventilator assistance PEEP: 5 cm H2O; 10 to 15 cm H2O with ARDS

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A 34-year-old patient with congestive heart failure (CHF) is in the ICU receiving noninvasive positive pressure ventilation by mask. The settings and ABG results are below:

Inspiratory positive airway pressure (IPAP): 14 cm H2O
Expiratory positive airway pressure (EPAP): 5cmH2O
RR: 12/min
pH: 7.29
PaCO2: 51 mm Hg
PaO2: 63 mm Hg
HCO3: 23 mEq/L
BE: - 1

Which of the following should be recommended to improve the patient’s ventilatory status?

A. Increase the EPAP to 10 cm H2O.
B. Decrease the IPAP to 12 cm H2O.
C. Decrease the EPAP to 3 cm H2O.
D. Increase the IPAP to 18 cm H2O.

Increase the IPAP to 18 cm H2O.

The blood gas results indicate respiratory acidosis or acute ventilatory failure. To lower the PaCO2, the minute volume must be increased. This is accomplished with noninvasive ventilation by increasing the delta-P, by either increasing the IPAP or decreasing the EPAP, which increases delivered VT. Since EPAP affects oxygenation more, increasing the IPAP is the best choice.

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The following data are collected on a 70-kg (154 lb) female receiving mechanical ventilation in volume control:

Mode: SIMV
Ventilator rate:12/min
Total rate: 24/min
VT: 500 mL
FiO2: 0.35
Pressure support: 7 cm H2O
PEEP: 5 cm H2O
ABGs:
pH: 7.48
PaCO2: 30 torr
PaO2: 62 torr
HCO3: 23 mEq/L
BE:-2

Which of the following ventilator changes are appropriate at this time?
A. Increase the PEEP to 10 cm H2O.
B. Decrease the tidal volume to 450 mL.
C. Decrease the SIMV rate to 8/min.
D. Increase the FiO2 to 0.45.

Increase the FiO2 to 0.45

The blood gas results indicate the patient is hyperventilating, but not because the minute volume is excessive, but because the patient is hypoxemic. The PaO2 must be corrected first, since that is what is causing the patient to hyperventilate. It is very important to ALWAYS look at the PaO2 when the patient is hyperventilating to determine if the patient’s hyperventilation is the result of hypoxemia. If the PaO2 is normal, then decreasing minute ventilation (VT, PIP, or rate) is indicated. Since the patient in this question is on an FiO2 of 0.35, increase the FiO2 first. If the patient was on an FiO2 of 0.50 to 0.60 or higher, increasing the PEEP would be appropriate.

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What are some indications for MV?

Apnea
Acute Ventilatory Failure
Impending Acute Ventilatory Failure
Oxygenation

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Define Acute vent failure (2)

PaCO2 > 50 mm Hg
pH <7.30

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What are the criteria for initiation of MV?

VC: < 10 to 15 mL/kg
P(A-a)O2: >450 mm Hg w/ the use of 100%
Dead space/ tidal volume ratio: > 60%
MIP (NIF): -20 cm H2O
Positive expiratory pressure (PEP): <40 cm H2O
RR: >35/ min
P/F ratio: <300 mm Hg (ALI)
<200 mm Hg (ARDS)

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What is normal Vital capacity (vc)?

65 to 75 mL/kg

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What is the normal range for P(A-a)O2?

25 to 65 mm Hg

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What is normal percentage range for Vd/Vt and calculation?

25% to 35%

Vd/Vt= PaCO2- PetCO2/PaCO2

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What is normal range for MIP (NIF)?

-50 to -100 cm H2O

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What is normal Positive expiratory pressure (PEP)?

100 cm H2O

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Normal RR

12 to 20/ min

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Normal range for P/F ratio

400 to 500 torr

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What are some complications of MV?

Barotrauma
Pulmonary infection (VAP)
Atelectasis
Pulmonary O2 Toxicity
Tracheal Damage
Decreased Venous Blood Return to the Heart
Decreased Urinary Output
Lack of Nutrition

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Explain Volume- Control Ventilation

A preset VT is delivered to the patient in
each machine breath, and once it is delivered, inspiration ends.

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Explain Pressure Control Ventilation

A preset inspiratory pressure is delivered to
the patient, and once it is reached, inspiration
ends.

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Peak inspiratory pressure (PIP) should be set to obtain a specified exhaled VT, generally 6 to 8 mL/kg of ideal body weight, or 4 to 6 mL/kg on patients with acute respiratory distress syndrome (ARDS). In other words, if the target exhaled VT is 600 mL and the actual exhaled VT is 500 mL, then PIP should be increased.

KNOW

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Studies have shown that PCV improves gas exchange, increases oxygenation, reduces PIP, increases mean airway pressure (MAP), reduces required PEEP levels, and decreases minute ventilation, especially when it is combined with an inverse I:E ratio. It has also been shown to reduce cardiovascular side effects and barotrauma compared with volume- controlled ventilation and PEEP.

KNOW

Auto-PEEP may result in (4)

- barotrauma - decreased venous return - cardiac output - increased patient effort to initiate a breath if the patient is triggering.

What is ARDS net strategies?

1. Target Vt of 4 to 6 mL/kg of IBW 2. Maintenance of alveolar (plateau) pressure <30 cm H2O 3. High PEEP (up to 24 cm H2O) 4. Permissive hypercapnia 5. Oxygenation traget PaO2 55 to 80 torr (SpO2 88% to 95%) 6. pH of 7.30 to 7.45 7. Avoidance of high FiO2 (maintain levels below 0.60)

pressure support ventilation is used to aid in the

weaning process from the vent

PSV is what kind of breath?

- pt-triggered - pressure limited - flow cycled breath

PSV is used to make spontaneous breathing through the ET tube during weaning more comfortable by overcoming the high resistance and increased inspiratory work caused by the ETtube (**5 to 10 cm H2O is all that is required to overcome tubing resistance**)

KNOW

NPPV (BiPAP) has 2 levels, what are they?

IPAP EPAP

IPAP= CO2 EPAP= O2

KNOW

The difference between IPAP and EPAP is called

Pressure support

What is control mode

- Patient is not able to trigger a ventilator breath. - Inspiration is strictly time-triggered. - The patient should be heavily sedated or paralyzed.

A/C mode

- In this mode, each breath is either patient- triggered or time-triggered. - This is a commonly used mode of ventilation. - The patient may initiate as many ventilator breaths as required above the set rate; therefore, the patient’s VE is not consistent.

Synchronized intermittent mandatory ventilation (SIMV)

- Allows for spontaneous breathing along with positive pressure ventilator breaths. It senses when the patient is breathing spontaneously; therefore, no “breath stacking” occurs. - It is used as both a weaning technique and for ventilation before weaning.

Continuous positive airway pressure (CPAP)

A preset pressure is maintained in the airways and alveoli as the patient breathes totally on his or her own. No positive pressure breaths are delivered.

**Patients whose PaO2 level cannot be maintained within normal limits using a 50% to 60% or more O2 mask and who have normal or low PaCO2 levels should be placed on CPAP. CPAP is also indicated for patients with obstructive sleep apnea who gain benefit from the positive airway pressure, which relieves the obstruction in the upper airway.**

KNOW

What should IBW be set to?

6 to 8 mL/kg 4 to 6 mL/kg for ARDS pt

IBW for male calculation

106+6 (H-60)/ 2.2

IBW for women

105+5 ( H-60)/2.2

Example: The physician wants your recommendation for the ventilator VT setting for a 5’3” female patient who weighs 150 kg (330 lb). 105+5 (H-60)/2 105 +5(63-60)/2 105+5 (3)/2 105+15= 120 120/2= 60 60 x 6= 360 mL To 60 x 8 = 480 mL

KNOW

Alveolar Minute Ventilation

VA= (VT-VD) x RR

Dead space equation

Paco2-Peco2/ Paco2 (small number # goes inside)

static compliance equation

Cs=Vt/Pplat-PEEP (big # goes on inside)

dynamic compliance equation

Dyan=Vt/ PIP-PEEP (big # goes on inside)

Alveolar air equation

Pb-Ph2O x FiO2 - PaCO2 x (1.25)

A-a gradient equation

P(A-a)O2

Airway Resistance Calculation

Raw= PIP-Pplat / Flow (L/sec divide by 60) (Big # goes on the inside)

In volume control, by increasing Vt, it increases the

inspiratory time

In volume control, by decreasing the Vt it decreases

inspiratory time, which increases E-time

Normal initial setting for RR (vent) is For ARDS pts For COPD

10 to 16 breaths/min 20 to 35/min 10 to 12/min

Adjusting the rate control alters the expiratory time, therefore altering the I:E ratio

KNOW

Increasing the rate decreases

expiratory time (E-time)

Decreasing the rate increases

E-time

Adjusting the rate alters Ve

KNOW

Increasing the rate

increases Ve

Decreasing the rate

decreases Ve

Adjusting the rate affects the PaCO2 levels

KNOW

Increasing the rate

decreases PaCO2

Decreasing the rate increases

PaCO2

Normal flow setting

40 to 80 L/min

Adjusting the flow rate alters the inspiratory time, therefore altering the I:E ratio

KNOW

Increasing the flow rate decreases

inspiratory time which increases E-time

Decreasing the flow rate increases

inspiratory time

Normal I:E ratio for the adult is

1:2 **means expiration is twice as long as inspiration**

What is normal I:E ratio for an infant?

1:1

The I:E ratio is establish by the use of 3 ventilator controls for volume-controlled ventilation. What are they?

- VT - Flow rate - RR

Increasing the Vt increases ______________ _______, which in turn makes inspiratory time (I-time) longer

inspiratory time

Decreasing the Vt decreases.....

inspiratory time which makes inspiratory time (I-time) shorter

Increasing flow rate

decreases I-time

Decreasing flow rate

increases I-time

Increasing RR...

decreases E-time

Decreasing RR

increases E-time

O2 percentage should be increased to a **maximum of 50% to 60% to maintain normal PaO2 levels. Once the FiO2 is reached, PEEP should be added or increased**

KNOW

O2 percentage should be reduced first to a level of 50% to 60% before decreasing PEEP levels in hyperoxygenated pts. Once the level is at 50% to 60% begin reducing PEEP, **except in pts w/ ARDS and/or pulmonary edema**

KNOW

What should the initial setting of FiO2 be set when beginning MV?

The same FiO2 the level the pt was getting prior to MV (30 to 40% for COPD pts)

Define sensitivity control.

It determines the amount of pt effort required to trigger the vent into inspiration

The sensitivity control should be set so that the pt generates

-0.5 to -2.0 cm H20 pressure

If the vent self triggers, the sensitivity is to high, what should be done to correct this?

Decrease the sensitivity

If it takes MORE than -2.0 cm H2O pressure to trigger the vent into inspiration, then..

increase the sensitivity

What is the purpose of an inflation hold?

The primary purpose of this control is to obtain a Pplat to calculate static CL.

Inflation hold should never be used on a spontaneous breathing pt

KNOW

What is PEEP and why is it used?

Positive-end expiratory pressure It is used to maintain positive pressure in the airway after a ventilator breath

What are some indictations of PEEP

- Atelectasis - PaO2 of <60 mm Hg on FiO2 of 50% O2 - Decreased Functional residual capacity (FRC) - Decreased CL - Pulmonary Edema - ARDS

Name some hazards of PEEP (4)

- Barotrauma - Decreased venous return - Decreased Cardiac output - Decreased urinary output

A decreased cardiac output (or cardiac index) caused by PEEP is indicated by a decrease in BP and PvO2 values

KNOW

What is optimal PEEP

the level of PEEP that improves lung compliance (CL) w/o cardiac compromise

Normal PvO2

35 to 45 mm Hg

A PvO2 _______ indicates a possible decrease in ___________ __________

<35 mm Hg cardiac output

If the PvO2 decreases after the initiation of PEEP, it is an indicator of

reduced venous return and cardiac output caused by PEEP

The PvO2 value indicates the adequacy of _________ ______________

tissue oxygenation (optimal PEEP= PvO2)

Low pressure alarms should be set to

5 to 10 cm H2O **BELOW** PIP

Low-pressure alarms is activated by (5)

- leaks in the vent circuit - leaks around the chest tube - ruptured ET tube cuff - inadequate cuff pressure - pt disconnection

High-pressure alarms should be set about

10 cm H2O **ABOVE** PIP

What happens when the high-pressure limit is reached w/ volume- controlled ventilation?

Inspiration ends prematurely, decreasing delivered Vt

High-pressure alarms may be activated by:

- Decreasing CL - Increasing Raw

Mean airway pressure (MAP or Paw) Monitoring is the average

pressure applied to the airway over a specific time

Paw is directly affected by (7)

- ventilator - PIP - I-time - E-time - PEEP level - Pressure waveform - I:E ratio

Capnography is a technique by which

exhaled CO2 is measured (PETCO2)

Normal PETCO2 is

35 to 45 mm Hg or 4.5% to 5.5%

The PETCO2 is normally about 4 to 6 mm Hg lower than the PaCO2

KNOW

PETCO2 readings may decrease as a result of any of the following:

- Hyperventilation - Apnea (readings falls to 0) - Total airway obstruction (readings fall to 0) - Conditions in which perfusion is deceased (hypotension, pulmonary embolism, decreased cardiac output)

PETCO2 readings may increase due to

- Hypoventilation - Hyperthermia (increased CO2 production)W

What is Dead space volume (Vd)

The portion of the Vt that does not participate in gas exchange

What are some types of Vd (4)

- Anatomic Vd - Alveolar Vd - Physiologic Vd - Mechanical Vd

Consist of the conducting airways from the nose and the mouth to the terminal bronchioles (i.e air that does not reach the alveolar epithelium where gas exchange occurs)

Anatomic Vd

Anatomic Vd = 1mL/lb of IBW

KNOW

What reduces anatomic Vd by 50% due to bypassing the upper airway ?

Tracheostomy

Air reaches the alveoli but does not take part in gas exchange. Results from lack of perfusion to air-filled alveoli (ex: pulmonary embolism)

Alveolar Vd

The sum of anatomic and alveolar Vd. The most accurate measurement of Vd

Physiologic Vd

Define Lung compliance (CL)

the ease w/ which the lung expands. It varies inversely w/ the pressure required to move a specific volume of air

The more compliant the lungs are...

the easier it is to ventilate the lung (the lung requires less pressure to ventilate)

The less complaint the lungs are...

the stiffer the lung is and harder it is to ventilate. ( The lung requires more pressure to ventilate)

Normal total CL

0.1 L/cm H2O (100 mL/cm H2O)

How is dynamic compliance measured?

air flowing through the circuit and airways. It is actually a measurement of Raw and CL

Dynamic compliance changes with changes in Raw caused by (4)

- Water in the ventilator tubing - Bronchospasm - Airway secretions - Mucosal edema

Dynamic compliance is NOT an accurate measurement of CL

KNOW

This is more accurate measurement of CL b/c it is measured w/ no air flowing through the circuit and airways (i.e. static conditions

Static compliance

EXAM NOTE: Sometimes on the exams the data provided to calculate static CL will include not only the ventilator Vt, but also the actual or exhaled. **ALWAYS use the actual volume and the equation if it is provided in the question.**

KNOW

Decreasing static CL results from

- PNA - Pulmonary edema - Consolidation - Atelectasis - Air-trapping - Pleural effusion - Pneumothorax - ARDS - Mainstem intubation

What is static CL range in the pt receiving ventilation is

60 to 70 mL/ cm H2O

EXAM NOTE: Calculation of CL is also important in the determination of optimal PEEP level

KNOW

Calculation of Raw: For an intubated ventilator patient, the amount of pressure being delivered to the airways and how much is going to the alveoli must be known. The difference between these two, the PIP and plateau pressure, referred to as transairway pressure, is the amount of pressure lost as a result of RAW

KNOW

Normal RAW in nonintubated individuals is

0.6 to 2.4 cm H2O/L/s, based on a flow rate of 30 L/min or 0.5 L/s.

Normal RAW in a ventilator patient is approximately

5 cm H2O/L/s.

Because RAW is measured in cm H2O/L/s, flow rate must be converted from L/min to L/s by dividing flow by 60

KNOW

What are the 3 ways we can manipulate CO2 in **volume control** ventilation?

- increase Vt (Always start with this first, if not outside IBW range) - increase RR (second choice if vt is maxed out) - Deadspace (decrease by removing ballard, HME, cut the tube)

How do we manipulate volume in **pressure control**

- increase PIP - Increase I-time (decrease I-time which increases I-time)

In pressure control when lung compliance increases....

pressure decreases

When assessing Raw subtract PIP and Pplat

KNOW

Pressure support helps overcome WOB

KNOW

In liberation of MV what Vt does a pt need to sustain life

5 mL/kg IBW

When Vd is over 60% pt needs to be on MV

KNOW

Hyperventilation is defined as

Paco2 < 35mm Hg

Hypoventilation is defined as

Paco2 > 45 mm Hg

Ch. 11 Ventilator Management Flashcards

(136 cards)