ARDS/ARF Flashcards
How is ARF (Acute respiratory failure) classified?
Two ways:
Hypoxemic (<60 PaO2, remember normal is 80–100)
Hypercapnic (>50 PaCO2, remember normal is 35–45)
What is meant by V/Q mismatch?
Ventilation (V) to perfusion (Q)
This means that healthy ventilation (at 4-6 L/min) matches the amount of blood flow to lungs (also 4–6 L/min). This yields a 1:1 ratio in healthy pt.
However, in V/Q mismatch, either ventilation or perfusion is not happening normally.
Normal range for V/Q?
0.8—1.2
Anything outside this is V/Q mismatch.
What are the normal differences in V/Q within the areas of the lungs?
Apex=always higher vent than perfusion
Base=lower ventilation than perfusion
What is the main difference between hypoxemic RF and hypercapnic RF?
Hypoxemic=problem oxygenating
Hypercapnic=problem ventilating
Common causes of hypoxemic RF?
ARDS
Asthma
Bronchitis
Emphysema
Pulm Edema
Any problem with respiratory system that prevents gas exchange.
Any cardiac problem that prevents perfusion to lungs.
What is a shunt?
2 types?
When blood is pumped through heart but didn’t get oxygenated.
This causes a serious V/Q mismatch that O2 therapy won’t help much. Will probably need vent.
2 types: anatomic (problem in heart anatomy)
Capillary (problem at pulmonary capillaries/alveoli) like pneumonia, etc.
Common causes of hypercapnic RF?
ARDS
Asthma
Bronchitis
Emphysema
Pulm. Edema
COPD
Cystic Fibrosis
Anything that causes hypoventilation like:
Chest wall trauma/damage/pain
CNS damage (injury, OD, CVA)
Neuromuscular problems (anything affecting muscles involved in breathing like ALS, MD, MS, etc)
What is diffusion impairment?
Classic sign?
Cause of hypoxemic RF
Alveolar/capillary membrane damaged (usually permanently and chronically)
Can become fibrotic and/or filled with fluid
Classic sign: Hypoxemia with exercise but not at rest. (this is because the blood pumps faster through lungs and doesn’t have time to oxygenate)
Consequences of hypoxemia?
Consequences of hypercapnia?
Hypoxemia: Increase in lactic acid»metabolic acidosis.
Remember lactic acid leaves the body through kidney’s buffer system, not lungs, so takes time.
Hypercapnea: Body tolerates better than hypoxemia. Usually a slow, gradual climb that the body compensates for in renal buffer system.
What is one condition that causes an increase in CO2 production?
Sepsis
First sign of hypoxemic RF?
Change in mental staus
Early signs of ARF?
Tachycardia
Tachypnea
Pallor
Rise in BP
Mild increase in WOB
(these are compensatory signs)
What is paradoxical breathing?
What does it indicate?
When chest/abdomen move in with inhalation and out with exhalation (the opposite of normal).
This indicates max use of accessory muscles and WOB. Indicates SEVERE respiratory distress.
What will be usually heard in pulmonary edema?
What is heard with fluid in airways?
Fine crackles
Coarse crackles on expiration. This may be from pneumonia or HF
What may diminished lung sounds indicate?
Atelectasis
Pleural effusion
Hypoventilation
Morning headache indicates…
Possible hypercapnia
What is good lung down?
When patient has one lung that is functioning better than the other, place pt lateral on side with good lung down. This increases oxygenation, blood flow and helps move out secretions to infected lung.
Caution when using corticosteroids in ARF?
May worsen hypokalemia caused by diuretics.
Will cause hyperglycemia, especially in pts with DM
What is ARDS?
Most common causes?
Sudden progressive form of ARF
Alveolar/cap membrane damaged, permeable»fills with fluid
Most common causes:
Sepsis»MODS
Aspiration
Pneumonia
Trauma
Shock
Classic sign of ARDS?
Refractory hypoxemia
(This means we are treating with O2 therapy, but O2 sats continue to decline)
What is the P/F ratio?
Helps determine severity of hypoxemia.
P=PaO2 (normal is 80–100)
F=FiO2 (room air is 21%)
P/F is the ratio of the PaO2 to FiO2 given.
Normal P/F= >400 This means breathing 21% FiO2 we can maintain a PaO2 of 80–100.
Severe P/F= <100. This means their PaO2 is low despite high FiO2 delivery.
What is ventilator bundle?
This is protocol of care for pts on vent
Includes:
1. Handwashing
2. Oral care
3. Daily extubation assessment
4. VTE prophylaxis
5. GI ulcer prophylaxis
6. Strict infection control measures
Best practice components of ARDS pt?
- O2
- Vent
- Low tidal volume (4–8 ml/kg)
- Permissive hypercapnia
- PEEP
- Prone
- ECMO
