Acute Respiratory Failure

Question 1

Hypoxemia is defined as ___.

Answer 1

Pao2 < 60 mmHg.

Question 2

A hypoxemic patient clinically presents with __ (list all).

Answer 2

-cyanosis
-decreased SpO2
-tachypnea
-tachycardia
-sob
-pleuritic chest pain
-AMS

Question 3

What is the best initial test for a patient suspected of hypoxemia?

Answer 3

ABG
-to confirm PaO2 < 60 mmHg, and
-to calculate the A-a O2 gradient to ascertain the cause of hypoxemia.

A-a Gradient = 150 - (PaCO2/0.8) - PaO2

or PAO2 - PaO2

Question 4

Increased A-a o2 gradient suggests hypoxemia due to ____ (list all).

Answer 4

1. R->L shunt: intra-cardiac or vascular shunt within the lungs.
2. VQ mismatch
   -airway disease (asthma, COPD)
   -Interstitial lung disease
   -Alveolar disease (atelectasis, pneumonia, pulmonary edema, ARDS).
   -Pulmonary vascular disease (pulmonary HTN)

Question 5

A normal A-a gradient in a hypoxemic patient suggests ___ (list all possibilities).

Answer 5

-low atm. o2 (low Fio2; high altitude).

or

-hypoventilation d/t obesity, decreased respiratory drive, NM disease, CNS depression.

Question 6

PaCo2 levels will be high in hypoxemia d/t ___.

Answer 6

hypoventilation (Aa gradient normal).

Question 7

Pao2 is not correctable with o2 supplementation in hypoxemia d/t ___.

Answer 7

in hypoxemia d/t shunt (right to left) such as seen in
-intracardiac R-> L shunt, or
-vascular shunt within the pulmonary circuit.

Question 8

____ is respiratory failure with refractory hypoxemia, decreased lung compliance, and non-cardiogenic pulmonary edema with a Pao2/Fio2 ≤ 300.

Answer 8

ARDS.

Question 9

What are some common triggers for ARDS?

Answer 9

-sepsis (most common)
-severe pulmonary infections (pneumonia)
-aspiration
-blood transfusion
-inhaled/ingested toxins
-trauma
-drowning.

Question 10

Overall mortality a/w ARDS is ___.

Answer 10

30-40%

Question 11

What are the clinical exam findings in acute injury (phase I) of ARDS?

Answer 11

normal physical exam +/- resp. alkalosis.

Question 12

Phase II of ARDS is clinically marked by ____.

Answer 12

-hyperventilation–> hypocapnia
-widening A-a gap
-begins-lasts: 6-48 hours

Question 13

Phase 3 of ARDS is clinically characterized by ___.

Answer 13

-acute respiratory failure
-tachypnea
-dyspnea
-decreased lung compliance
-scattered rales
-diffuse chest opacities on CXR

Question 14

Phase 4 of ARDS is clinically characterized by ___.

Answer 14

-Severe hypoxemia unresponsive to t/t
-Increased intrapulmonary shunting
-metabolic and respiratory acidosis.

Question 15

Development of pulmonary edema on CXR < 24 hours after trauma is most likely suggestive of ___ than ___.

Answer 15

more likely suggestive of pulmonary contusion than ARDS.

Question 16

According to the Berlin definition, for an ARDS diagnosis, the onset of respiratory distress is ____ (? time).

Answer 16

is acute < 1 week onset of respiratory distress (12-48 hrs mostly).

Question 17

____ position in select patients with *severe ARDS is a/w reduced mortality.

*severe s/s with Pao2/Fio2 < 150 mmHg at Fio2 ≥ 0.6, and PEEP ≥ 5 cm of H2o.

Answer 17

prone position

Question 18

Goal oxygenation in m/m of ARDS is ___.

Answer 18

Pao2 > 55 mmHg or Spo2 > 88%.

Question 19

Fio2 must be attempted to be kept below ___ to prevent o2 toxicity in ARDS m/m.

Answer 19

≤ 60% (0.6)

Question 20

VT is usually set to ___ mL/kg in OLD, and to ___ in RLD/ARDS.

Answer 20

6-8 mL/kg in OLD;

6 mL/kg in RLD/ARDS.

Question 21

The respiratory rate is set lower for OLD at ___/min as compared to ___ in ARDS.

Answer 21

10-14/min in OLD;

14-18 in ARDS.

Question 22

I:E ratio is set to ___ in OLD and ___ in ARDS/RLD.

Answer 22

1:3 in OLD; and
1:1.5 in ARDS/RLD.

Question 23

What is the mechanism by which acute hypotension may be induced in patients on mechanical ventilation?

Answer 23

1. Tension pneumothorax –> sudden ↓↓↓ in CO –> ↓↓ BP (clue: sudden ↑↑ in PIP).

and/or

2. ↓↓ Venous Return: d/t ↑↑ intra-thoracic pressure d/t high PEEP
3. Sedatives & Opioids.

Question 24

High PEEP is beneficial in patients with ___-sided HF d/t ___.

Answer 24

Lt-sided HF as high PEEP –> ↑↑ intra-thoracic pressure –> ↓↓ VR (pre-load) and ↓↓ afterload.

Question 25

High PEEP worsens ___-sided HF d/t ___.

Answer 25

high PEEP worsens right-sided HF because↑↑ intra-thoracic pressure d/t high PEEP–> ↑↑ pulmonary vascular pressure.

Question 26

What are the target Spo2 and Pao2 goals in patients with acute brain injury?

Answer 26

target Spo2 of 94%-98%

target Pao2 of 80-100 mmHg.

Question 27

How does intracranial pressure respond to hypoxemia?

Answer 27

rises.