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Spr2015_Week7 > ARDS and ALI > Flashcards

ARDS and ALI Flashcards

1
Q

Define hypoxemic respiratory failure

Causes?

A

anything that limits diffusion or V/Q matching so O2 sat decr diffusion across alveolocapillary membrane (impaired gas diffusion)
–> V/Q mismatch

  • -> high altitude (low PIO2)
  • -> alveolar hypoventilation
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2
Q

What is alveolar hypoventilation

A

excess CO2

No room for O2

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3
Q

What are examples of V/Q mismatch diseases

A

1) pneumonia
2) pulm edema
3) obstructive airways

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4
Q

which conditions are more likely to have signif shunt

A

1) alveolar collapse or filling

PNA/ARDS

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5
Q

examples of decr diffusion across alveolocapillary membrane causing hypoxemia

A

1) interstitial fibrosis

2) amyloid

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6
Q

examples of alvolear hypoventilation causing hypoxemia

A

1) sedatives
2) alcohol
3) brain injury
4) neuromuscular disease

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7
Q

define hypercapneic resp failure

separated by?

A

any process that impairs ventilation (CO2 elimination) or elev CO2

can’t breathe vs. won’t breathe

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8
Q

hypercapneic resp failure

if you can’t breathe, causes…

lung diseases

A

1) asthma
2) COPD
3) upper airway obstruction
4) severe burn (chest wall restriction)
5) trauma
6) neuromuscular

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9
Q

hypercapneic resp failure

if you won’t breathe, causes

A

chronic lung disease
adapted to chronic ability to hypoventilate

1) central hypoventilation
2) oversedation
3) brain injury
4) seizure

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10
Q

2 determinants of ventilation

To incr ventilation, incr…

A

1) tidal volume (affects ventilation)

2) respiratory rate (affects ventilation)

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11
Q

To incr oxygenation on ventilation

A

3) incr FIO2 (0.21 vs. 1.00)

4) PEEP (more recruit alveolus)

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12
Q

what ultimately determines PaCO2

A

alveolar ventilation

Va = (Vt - Vd) x f

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13
Q

Define dead space ventilation

causes of deadspace

A

a process that decr perfusion to ventilated alveoli, incr physio dead space (air, but no blood flow)

1) hypovolemia (lower perfusing pressure –> alveolar collapse and need high vent pressures)
2) decr CO
3) PE (stopped blood flow)
4) high airway pressures (when alveolar pressure > capillary pressure = no ventilation = zone 1)

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14
Q

When evaluating respiratory failure,

procedure?

A

1) physical exam
2) CXR
3) ABG

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15
Q

Standard notation of ABG

A

pH/pCO2/pO2

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16
Q

Calculate A-a DO2

7.36/36/65 on room air in Denver

A

PAO2=(Pbar-PH2O) x FIO2-PaCO2/RQ
PAO2=(630-47)x 0.21-36/0.8
PAO2=77

A-a DO2= PAO2-PaO2
A-a DO2= 77-65
A-a DO2= 12

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17
Q

Normal A-a reflects ___

A

normal lung function in regards to oxygenation

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18
Q

Hypoxemia in setting of normal A-a DO2 is due to?

A

Low Pbar
Low FIO2
Low PaCO2

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19
Q

Compensation rules for acute respiratory acidosis

A

[HCO3-] ↑ 1 mEq/L : PaCO2 ↑ 10 mm Hg

∆ pH = 0.008 x (40- PaCO2)

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20
Q

Comepnsation rules for chronic respiratory acidosis

A

[HCO3-] ↑ 4 mEq/L : PaCO2 ↑ 10 mm Hg

∆ pH = 0.003 x (40- PaCO2)

21
Q

Approach to classification of respiratory failure

A

1) calculate A-a DO2 to classify hypoxemia
- primary diffusion, V/Q or shunt
- hypercapnea

2) acute vs. chronic based on clinical
3) if respiratory acidosis is present, THERE IS A COMPONENT OF hypercapneic resp failure
4) determine acute vs chronic based on compensation rule

22
Q

KNOW!!!!!!!!!!
for the exam,
if a patient has hypoxemic due to alveolar hypoventilation, THEY HAVE ____

A

they don’t have hypoxemic respiratory failure

THEY HAVE HYPERCAPNIC RESPIRATORY FAILURE

23
Q

normal A-a gradient excludes ____

A

hypoxemic respiratory failure

24
Q

Example 1
65 year old woman with mild emphysema, no home oxygen requirement, and 3 days of increasing cough and wheeze presents with shortness of breath.
ABG: 7.28/55/30 on room air.

Calculate A-a on room air in Denver

A

PAO2=(Pbar-PH2O) x FIO2-PaCO2/RQ
PAO2=(630-47)x 0.21-55/0.8
PAO2= 54

A-a DO2= PAO2-PaO2
A-a DO2= 54-30
A-a DO2= 24

∆pH = 0.12 (from 7.40)
∆pCO2=15 (from 40 normal)
0.12/15=0.008 (and ratio = 0.008) so pure acute mixed resp failure resp acidosis
(both acute hypoxemic and hypercapneic)

25
Q

Example 1
65 year old woman with mild emphysema, no home oxygen requirement, and 3 days of increasing cough and wheeze presents with shortness of breath.
ABG: 7.28/55/30 on room air.

Diagnosis?

A

∆pH = 0.12 (from 7.40)
∆pCO2=15 (from 40 normal)
0.12/15=0.008

respiratory acidosis
hypercapneic resp failure
hypoxemia

we know she has hx of emphysema and she has no home O2
so likely just ACUTE

26
Q

Long-term smoker who hasn’t seen a doctor in 40 years comes in with obvious emphysema on Xray, saturating 82% on room air, 92% on 4L?

A

has some chronic hypoxemia

feeling fine —> then came
down with cold (acute on chronic)

27
Q

Example 2
42 y/o morbid obesity and chronic low back pain. Has had worsened low back pain the past few days, for which he has been taking oxycodone. Brought into ED after family found him very sleepy and confused.
ABG: 7.30/54/55 on room air.

Calculate the A-a DO2:
on room air in Denver

A

PAO2=(Pbar-PH2O) x FIO2-PaCO2/RQ
PAO2=(630-47)x 0.21-55/0.8
PAO2= 55

A-a DO2= PAO2-PaO2
A-a DO2= 55-55
A-a DO2= 0

∆pH = 0.09
∆pCO2=14
0.09/15=0.006 (between 0.003 and 0.008 since between acute and chronic = acute-on-chronic)

28
Q

Example 2
42 y/o morbid obesity and chronic low back pain. Has had worsened low back pain the past few days, for which he has been taking oxycodone. Brought into ED after family found him very sleepy and confused.
ABG: 7.30/54/55 on room air.

what does he have?

A

∆pH = 0.09
∆pCO2=14
0.09/14=0.006
no hypoxemic

acute-on-chronic hypercapnea
PaCO2 is high, pH low

29
Q

Patient with chronic lung disease on 2L per minute nasal cannula O2 at home

comes in with sat of 92% on 2L?

comes in with saturation of 82% on 2L, 92% on 6L

A

chronic hypoxemic at basleine

acute on chronic resp failure (when there is change in baseline and have chronic so manage the chronic)

30
Q

Define PEEP

A

ET tube prevents glottis’ ability to maintain expiratory pressure and lung inflation

when vent goes into exhalation, provides an adjustable back pressure to stim glottic closure

–> MAINTAIN ALVEOLAR RECRUITMENT AND SURFACE AREA, PREVENT DERECRUITMENT

31
Q

Without PEEP what happens?

A

1) atelectasis = deflation of alveoli causing alveolar de-recruitment, decr surface area

PEEP maintains surface area in hypoxemia

32
Q

100% FIO2 AND 5 PEEP

and not oxygenating well then ____

A

turn up the PEEP

33
Q

22 year old woman with history of asthma comes in with an acute attack, requiring intubation and mechanical ventilation.
What type of respiratory failure do you expect?
7.10/80/470

A

PAO2=(Pbar-PH2O) x FIO2-PaCO2/RQ
PAO2=(630-47)x 1-80/0.8
PAO2= 483

A-a DO2= PAO2-PaO2
A-a DO2= 483-470
A-a DO2= 13

∆pH = 0.3
∆pCO2=40
0.3/40=0.008

ACUTE HYPERCAPNEIC RESP FAILURE
need to incr ventilation

34
Q

22 year old woman with history of asthma comes in with an acute attack, requiring intubation and mechanical ventilation.

Assuming her vent settings are VT 500, RR 20, FIO2 100%, PEEP 5, what next?

A

HYPERCAPNEIC RESP FAILURE
need to incr ventilation

Decrease FIO2
increase RR (or VT),

turn down FIO2 because 470 is too high and don’t have to worry about oxygenation

treat asthma with standard therapies (steroids, bronchodilators, ± antibiotics).

35
Q

62 year old woman with history of chronic systolic heart failure comes in decompensated and volume overloaded. Despite diuresis, afterload reduction, and supplemental oxygen, she requires intubation and mechanical ventilation.

What type of respiratory failure do you expect?
7.50/28/45

A

PAO2=(Pbar-PH2O) x FIO2-PaCO2/RQ
PAO2=(630-47)x 1-28/0.8
PAO2= 578

A-a DO2= PAO2-PaO2
A-a DO2= 578-45
A-a DO2= 533

∆pH = 0.10
∆pCO2=12
0.10/12=0.008

hyperventilating and
hypoxemic respiratory fialure

acute resp alkalosis
pulm edema interstitial and alveolar space –> hypoxemia

36
Q

62 year old woman with history of chronic systolic heart failure comes in decompensated and volume overloaded. Despite diuresis, afterload reduction, and supplemental oxygen, she requires intubation and mechanical ventilation.
Assuming her vent settings are VT 500, RR 20, FIO2 100%, PEEP 5, what next?

A

Ventilation is OK. Since our vents don’t go to 11, our only option is to increase PEEP.

since vent already maxed out at FIO2 = 100% can only change PEEP

37
Q

Definition of ARDS

A

occurs within 1 week of known insult/worsening resp symptoms

2) diffuse bilateral pulm infiltrates
3) not explained by cardiac failure/fluid overload

4) severity classfiied by PaO2: FIO2 with > 5 cM-H2O PEEP
best if 201-300 = mild

38
Q

ARDS pathogenesis

A

1) inflamm and macrophage infiltrate –> disrupt alveolar/capill barrier function –> alveolar flooding with fluid, red cells neutrophils, LOSS surfactant

39
Q

histology of ARDS

A

hyaline membrane with hypoxemic resp failure

1) alveolar filling with protein edema
2) denuded basement membrane
3) HYALINE MEMBRANE (PROTEIN DEPOSITION)
4) neutrophils, hemorrhage
5) type II hyperplasia

40
Q

radiology of ARDS

A

bilateral alveolar infiltrates

41
Q

etiology of ARDS

A

1) Sepsis
2) pancreatitis
3) trauma
4) aspiration
5) transfusion = indirect

42
Q

most likely pathogenesis of ARDS

A

UTI –> cytokines –> lungs –> oxidant damage

humoral
cytokines
activ neutrophils

43
Q

functional disability after ARDS 5 yrs later

A

at 1 yr –> physiologic limitation

over 5 yrs physiology unchanged but return to work improved

44
Q

how to treat ARDS

A

1) treat underlying cause
2) supportive care

3) ventilator management
6 cc/kg tidal voluem, plateau pressure

45
Q

what is ventilator induced lung injury

A

high tidal volume ventilation can worsen lung injury and systemic inflamm

46
Q

why is prone position better for ARDS ventilation

when to use?

A

more uniform transpulmonary pressure and distrib of alveolar stress

PaO2:FIO2

47
Q

Before incr a patient’s tidal volume based on ABG, ___

A

make sure does not meet criteria for ARDS

48
Q

ventilate patient with ___ ON EXAM!!!

A

LOW TIDAL VOLUME

CONSIDER PRONE IN SEVERE

Spr2015_Week7 (10 decks)

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