Ch. 11 Ventilator Management Flashcards
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
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.
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.
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.
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
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
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.
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
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.
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.
What are some indications for MV?
- Apnea
- Acute Ventilatory Failure
- Impending Acute Ventilatory Failure
- Oxygenation
Define Acute vent failure (2)
- PaCO2 > 50 mm Hg
- pH <7.30
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)
What is normal Vital capacity (vc)?
65 to 75 mL/kg
What is the normal range for P(A-a)O2?
25 to 65 mm Hg
What is normal percentage range for Vd/Vt and calculation?
25% to 35%
Vd/Vt= PaCO2- PetCO2/PaCO2
What is normal range for MIP (NIF)?
-50 to -100 cm H2O
What is normal Positive expiratory pressure (PEP)?
100 cm H2O
Normal RR
12 to 20/ min
Normal range for P/F ratio
400 to 500 torr
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
Explain Volume- Control Ventilation
A preset VT is delivered to the patient in
each machine breath, and once it is delivered, inspiration ends.
Explain Pressure Control Ventilation
A preset inspiratory pressure is delivered to
the patient, and once it is reached, inspiration
ends.
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
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?
- Target Vt of 4 to 6 mL/kg of IBW
- Maintenance of alveolar (plateau) pressure <30 cm H2O
- High PEEP (up to 24 cm H2O)
- Permissive hypercapnia
- Oxygenation traget PaO2 55 to 80 torr (SpO2 88% to 95%)
- pH of 7.30 to 7.45
- 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)
