Unit 1: Mechanical ventilation Case studies
Name:
Date:
Case study # 1
2009
Patient is a 55 YO BF with a history of COPD. She has a respiratory rate of 25 bpm on 24%
Venti-mask. She has HR 125 bpm and systemic BP of 145/88 torr. Her Sp02 is 88% and she has
intercostal retractions and is purse-lip breathing.
1.
List information you would need to diagnosis respiratory failure.

Need ABG to assess the PaC02 and the pH:
i. Is this patient in chronic respiratory failure? Does this patient have fully
compensated respiratory acidosis as a baseline? Or does she now have
partially compensated respiratory acidosis?
ii. Are serial ABG showing a rise in PaC02 as the patient tires out? Is she
suffering acute hypercapnic respiratory failure?
iii. Does the hypoxemia respond to increasing the Fi02? Is she going into
refractory hypoxemia [check a/A ratio] ; hypoxemic respiratory failure?

Assess the patient’s LOC for ability to keep breathing and to protect her airway
2. What information, if any, do you need to diagnosis increased WOB?
She has visible signs of increased WOB; we could palpate the belly for tensing of the abdominal
muscles, but we’ve got plenty of evidence of increased WOB. On interview we could ask if she feels
SOB.
Her BBS show distant breathsounds with prolonged exhalation. The EKG show right heart
hypertrophy. She has the following ABG on 24% Fi02:
pH
7.39
PaC02
51
HC0330
Pa02
52
3. What actions do you recommend at this time?
 She has fully compensated respiratory acidosis with moderate hypoxemia so is not in
chronic respiratory failure, but she needs to increase her Fi02 to 27-28% to get her
Pa02 between 55-65 torr so that cor pulmonale is not complicated.

We need to administer Beta II agonists with cholinergic antagonist and possibly a
mucolytics to mobilize secretions

Get a sputum for gram stain, and if patient is febrile, start her on broad- spectrum
antibiotics
4.
Does this lady have a V/Q mismatch or a shunt?
 She has a V/Q mismatch because increasing the Fi02 to 27-28% will convert her
moderate hypoxemia to mild
5.
Does this lady have any problems with her ventilatory drive at this time?
 No, her pH is fully compensated, showing that her PaC02 is close to her baseline
levels---but her respiratory rate is rapid & she may get tired eventually we need to
watch her.
6. Under what circumstances could this patient develop problems with her ventilatory
drive?
 If she gets tired and the PaC02 starts to rise and the pH drops, she would be in
chronic respiratory failure and may not be able to raise her V E enough.

If her Pa02 was raised above 55-65 torr, she could lose her hypoxic drive

If her PaC02 rises to above 60-70 torr, she could have altered LOC from Co2
narcosis
7.
Would you expect that this person could have low V/Q or high V/Q?
Both:

The EKG shows s/s of right heart failure secondary to lung disease

Wide-spread vasoconstriction hampers blood flow to some areas of the lung so
the patient would have high V/Q,

Patient would also have low V/Q because of the decreased alveolar ventilation
associated with serious airway issues
8. Does this patient show s/s of current respiratory failure?
 Not right now
9. In the PFT lab, her RAW is measured at 15 cmH20/L/sec. Is this abnormal?
 normal RAW of .5 to 2.5 cm H20/L/second, so her RAW is excessive
10. Explain how the RAW would affect her WOB.

Increased RAW increases the driving pressure needed to send gas down the
airways; as driving pressures rise [difference between P1 and P2] the WOB
rises
11. If she was to have problems later, would it be type I, type II or type III respiratory failure?
 type III chronic respiratory failure?
Case study # 2
Your patient is an 18 YO WM with a history of near-drowning. His respiratory rate is 26 bpm,
his HR is 127 BPM and his Sp02 is 81%. You hear diffuse fine crackles in upper lobes and poor
air movement in both basal lobes. He is confused and combative and refuses to lie down.
1. List information you would need to diagnosis respiratory failure.
 I need an ABG to assess his Pa02 for hypoxemia respiratory failure

I need an ABG to assess his PaC02 for hypercapnic respiratory failure

I need to interview him and inspect him to see if he can protect his airway
2. Does this patient have increased WOB?
 His respiratory rate is fast and based on the BBS, he may have decreased
compliance which would increase his required driving pressure
He has the following ABG on 30% Fi02:
pH
PaC02
7.330
51
HC0326
Pa02
48
3. Does this patient have a V/Q mismatch or a shunt?
 Because the Pa02 can be raised to 80 torr by increasing the Fi02 to 50%, technically
we have a V/Q mismatch.
4. What is the most likely cause of the hypoxemia?
 His P[A-a]D02 = 150- 48 = 102 mmHg [high]

His a/A ratio is 48/150 = .32 [low]

Pa02/Fi02 = 48/.30 = 160 [less than 200]

Both show diffusion problems

Fluid buildup in the interstitial area of the lung from aspiration of water or from
osmotic-hydrostatic pressures of adding water to the blood stream

5.
While he was under the water, he was suffering from low Pi02
List causes for the hypercapnia at this time?
 This Patient has altered LOC, he may not recognize hypercapnia & acidosis and
may fail to respond

If he cannot exchange his gases effectively, just raising the Fi02 to 50% will not be
enough
6. What actions do you recommend at this time?
 Intubate to protect his airway and ventilate to raise his VE to return his PaC02 thus
his pH to WNL because he is in respiratory failure type I [acute hypercapnic
respiratory failure]

7.
Once he is intubed and ventilated, sedate him.
If he develops respiratory failure, based on the history and PE, would you expect this
patient to have type I, type II or type III respiratory failure?
 He already has acute hypercapnic respiratory failure type II
Case study # 3
Your patient can raise his head off the pillow and roll over, but he cannot walk since he woke
this morning. He can squeeze your hands but not wiggle his feet. He has a history of viral
infection 2 weeks ago. His current ABG is on .21 is:
pH
PaC02
HC03Pa02
7.44
35
23
78
His IBW is 70 kg. Per doctor’s orders you measure the following parameters Q 2:
time
VT
RR
VE
NIP/
MIP/
PI max
PE max
0930
500 ml
15
7.5 lpm
-50
60
IC
1.5 liters
1130
500 ml
16
8.0
-45
35
1.2 liters
1330
400 ml
19
7.6
-25
20
800 ml
1.
At 0930, are there any s/s of inadequate alveolar ventilation?
 His C02 and his pH are WNL

We need to listen to BBS for diminished BBS or crackles that would imply there
is atelectasis
 We could look at an X-ray to see if there is atelectasis
2. At 0930, are there any s/s of inadequate lung expansion?

We need to listen to BBS for diminished BBS associated with poor lung
expansion

We need to inspect the patient for s/s of poor chest excursion

We could look at an X-ray to see if there is atelectasis

The patient’s VT is more than 5 ml/kg IBW; no problems with lung expansion at
0930

he should be able to cough effectively, because his IC is above 12- ml/kg IBW
3. At 0930, are there any s/s of poor muscle strength?
 No, both the inspiratory and expiratory max pressures are WNL, but we need to
observe his ability to cough- can he lift his head and protect his airway?
4. Do you think an ABG would be required at 1130 or at 1330?
 We need an ABG at 1330 because there are decreases in many parameters
5.
At 1330, are there any s/s of inadequate alveolar ventilation?
 Yes, the VT is now only 5.7 ml/kg IBW & the respiratory rate increased to keep the
VE up to remove C02
6. At 1330, are there any s/s of inadequate lung expansion?
 Yes, the IC has dropped below 12 ml/kg IBW so the ability to cough is hampered
7.
At 1330, are there any s/s of poor muscle strength?

At 1330, we see that both PI max and PE max are low, implying that there is both
chest and abdominal muscle weakness. Note: that there was abdominal muscle
weakness at 1130
8. If this patient’s VD anatomical is 150 ml, calculate his VD /VT at 09:30, at 11:30 and at
13:30.
0930
150/ 500 = .30
9.
1130
150/ 500= .30
1330
150/ 400=.375
Explain this trend in VD / VT

his VD remains the same, so as the VT drops the ratio of VD/VT rises

if the VD/VTrises to .60 --his WOB will be too high
10. If he develops respiratory failure, based on the history and PE, would you expect this
patient to have type I, type II or type III respiratory failure?
 He would have acute hypercapnic respiratory failure [Type II] because the VE will
not be able to blow off the C02.
Case study # 4
Patient is a 25 YO LAM who is status post exposure to a toxic chemical. His
respiratory rate is 45 bpm. He is retracting and is deeply cyanotic. His Sp02 on NRM
is only 82%. On auscultation, you hear BBS with crackles.
pH
PaC02
HC03-
Pa02
7.423
38
24
42
1. Make recommendations to correct his hypoxia.
 We cannot correct his hypoxia with increasing Fi02 & the patient is on
NRM. Even if we add a nasal cannula at a high flow rate, the current
Fi02 is more than 50% with a Pa02 of less than 50 mmHg

level of hypoxemia is refractory

s/s of hypoxemia respiratory failure include:
i. Pa02/Fi02= 42/1.00 = 42 so less than 200
ii. P(A-a)D02 on 100% = P(675-42)D02 = 633 which is more than
350
iii. a/A ratio is 42/675 = .06- refractory hypoxemia

He needs to go on mechanical ventilation so we can add PEEP

As long as he can protect his airway and he is alert, we could manage
him on none-invasive positive pressure ventilation

Negative pressure ventilation would only blow off C02- which he can
do himself
2. Identify further assessment this patient might need.
 We need to assess his LOC; can he protect his airway & respond to
changes in acid/base or 02 levels?

We need to get an X-ray : is there significant atelectasis

Inspection of his chest for poor chest excursion?
3. Does he have V/Q mismatch or a shunt-like affect?
 Because increasing Fi02 is not an option, we know that he has a shuntlike effect
4. How can his gas exposure affect his ability to oxygenate?
 Many toxic gases cause chemical burns. Based on the BBS, the
changes seem to be in the alveoli. Thickened membrane from swelling,
or decreased surface area from atelectasis could both decrease the
diffusion of 02
5. Why has this not affected his ability to exchange C02?
 C02 diffusion is 2o x better than 02 so it is not uncommon to see
hypoxia before hypercapnia
6. Identify the type of respiratory failure this patient is suffering right now.
 Right now, he has hypoxemia respiratory failure,
7. If his C02 was to rise later in the day, what type of respiratory failure might he be
suffering?
 If his C02 rises due to hampered ventilator drive, or fatigue he could
slip into acute hypercapnic respiratory failure