Lung pathology in ICU

Question 1

what 2 things result in respiratory failure

Answer 1

1. oxygenation
2. carbon dioxide elimination

Question 2

what are the types of resp failure

Answer 2

1. type 1 resp failure
   - the respiratory cannot adequately provide oxygen to the body leading hypoxemia
2. type 2 resp failure
   - the respiratory system cannot adequately remove carbon dioxide from the body leading to hypercapnia

Question 3

what is the PaO2 like in type 1 resp failure

Answer 3

<60mmHg

Question 4

what is the PaCO2 like in type 1 resp failure

Answer 4

normal or decreased

Question 5

in type 1 resp failure what is the Alveolar-arterial gradient like

Answer 5

normal or increased

Question 6

how do you calculate the Alveolar-arterial gradient

Answer 6

A-a gradient = PAO2 - PaO2
PAO2= Alveolar partial pressure of oxygen
PaO2 = Arterial partial pressure of oxygen

Question 7

what is the PaCO2 and pH like in type 2 resp failure

Answer 7

• PaCO2 >45mmHg
• pH<7.35

Question 8

what are causes of respiratory failure (4)

Answer 8

1. Hypoventilation
2. Impaired gas exchange
3. Airway obstruction
4. Ventilation/Perfusion mismatch (V/Q mismatch)`

Question 9

what are causes of hypoventilation (5)

Answer 9

1. neurological depression
   - medications ( benzodiazepines, opioids)
   - drug overdoses (alcohol, OPP)
   - anesthesia
2. increased ICP
   - head injuries
   - stroke
   - encephalitis
3. Nerve or neuromuscular impairment
   - spinal cord injury ( C4 impairment and above)
   - ALS ( amyotrophic lateral sclerosis)
   - guillain barre syndrome
   - botulism
   - myasthenia graves
4. fatigue of resp muscles
5. chest wall injury
   - flail chest
   - kyphoscoliosis

Question 10

How does impaired gas exchange come about (4)

Answer 10

1. direct membrane damage
2. collection of fluid in alveoli
3. collection of fluid in interstitial space
4. collapse of alveoli

Question 11

what are some causes of impaired gas exchange (8)

Answer 11

1. inhalation of toxic gases
2. pneumonia
3. sepsis
4. ARDS
5. pulmonary edema
6. pneumothorax
7. pleural effusion
8. atelectasis

Question 12

what are causes of airway obstruction (4)

Answer 12

1. airway thickening
   - fibrosis
   - edema
2. constriction
   - asthma
   - COPD
3. blockage
   - foreign body
   - secretions
   - fluid
4. compression of airway
   - tumor
   - enlarged lymph nodes
   - interstitial edema

Question 13

what are causes of V/Q mismatch (7)

Answer 13

Shunt ( good perfusion w/o ventilation of alveoli)
1. impaired gas exchange
2. airway obstruction
3. pulmonary A/V fistulas
4. intra cardiac shunt (R-L)

Physiologic dead space ( good ventilation w/o perfusion)
5. shock
6. PE
7. emphysema/ COPD/ asthma

Question 14

what are some causes of type 1 resp failure (5)

Answer 14

1. alveolar hypoventilation
2. Low atmospheric pressure/fraction of inspired oxygen
3. Diffusion defect
4. Ventilation/perfusion mismatch
5. Right-to-left shunt

Question 15

what are some causes of type 2 resp failure (2)

Answer 15

1. Respiratory pump failure
2. Increased carbon dioxide production

• The respiratory pump is comprised of the chest wall, the pulmonary parenchyma, the muscles of respiration, as well as the central and peripheral nervous systems. The inability to ventilatecan occurif any of the components mentioned above of the respiratory pump fails.