Respiratory failure

Question 1

Typical pH range for chronic vs acute respiratory failure:

Answer 1

• Acute - pH falls quickly below 7.2
• Chronic - pH typically greater than 7.2 due to HCO3 retention

Question 2

4 pathophysiological factors causing hypoxemic respiratory failure:

Answer 2

• 1 - Ventilation-perfusion mismatch
• 2 - Shunting
• 3 - Diffusion limitations
• 4 - Alveolar hypoventilation

Question 3

Ventilation perfusion mismatch - explain with formula

Answer 3

V/Q=1
V = Q = 4mL
V - amount of gas that reaches lungs
Q - amount of blood perfusing the lungs

• Decreased V - interstitial lung disease - pneumonia, COPD, asthma
• V/Q = 1/4
• Overperfusion with normal V - PE, decreased CO
• V/Q = 4/1

Question 4

Explain what is shunting and the causes

Answer 4

• Blood supply to lungs does not pass pulmonary capillaries:
• Anatomic
• Cardiac - R/L shunt, Talot’s tetralogy, Eisenmenger’s syndrome
• Intrapulmonary shunt (pneumonia, atelectasis, collapse, oedema
• Exaggerated V/Q mismatch

Question 5

How much is the anatomic shunting?

Answer 5

5% maximum

Question 6

Diffusion limitations - cause and etiology

Answer 6

• Thickened alveolar membrane due to:
• Emphysema
• Recurrent PE
• pulmonary fibrosis

Question 7

Alveolar hypoventilation - definition, causes?

Answer 7

• Ventilation falls under 4L/min
• Restrictive lung disease
• CNS depression
• Chest wall dysfunction
• Neuromuscular disease

Question 8

Hypoxemic vs hypercapnic respiratory failure

Answer 8

Hypoxemic is PaO2 lessthan 60
Hypercapnic is PaCO2 greater than 50

Question 9

Hypercapnic respiratory failure causes (6):

Answer 9

1 - CNS disorder w/ diminished resp. drive - general anesthesia, narcotics, barbiturates, brainstem stroke or trauma

2 - Disorders of the spinal cord - high cervical spinal cord trauma, cervical myelitis, amyotrophic lateral sclerosis

3 - Disorders of peripheral nerves and muscles - Myasthenia gravis, Guillian-Barre syndrome, NM blockade, polimyelitis, muscular dystrophy

4 - Disorders of the thoracic cage w/ increased chest stiffness - kyphoscoliosis, morbid obesity, flail chest

5 - Disorders of lung parenchyma - pulmonary fibrosis, sarcoidosis

6 - Disorders of airways - asthma, COPD, CF

Question 10

Early signs of resp. faliure (non-specific):

Answer 10

• Mental status change
• Increased HR
• Increased RR
• Mild HTN

Question 11

Type 1 resp. faliure symptoms:

Answer 11

• Dyspnea, irritability, confusion, fits, somnolence, CYANOSIS, pulmonary HTN

Prolonged expiration, nasal flaring, tachypnea, dyspnea

Question 12

Type 2 resp. failure symptoms:

Answer 12

High CBF, headache, blurred vision (papilledema), excitation, coma, warm extremities, asterix, collapsing pulse, acidosis

Pursed lip breathing, morning headache, rapid and shallow breathing, tripod position

Question 13

Normal values of pH, CO2, HCO3:

Answer 13

7.35-7.45
35-45
23-27

Question 14

If increased PaCO2 accompanies decreased PaO2, then ARF is secondary to?

Answer 14

Alveolar hypoventilation

Question 15

Minute ventialtion formula:

Answer 15

Minute ventilation = Tidal volume X respiratory rate

Question 16

Types of Oxygen therapy:

Answer 16

Nasal oxygen catheter
Venturi mask
Non-rebreathing mask
Intubation
Tracheostomy
Coniotomy

Question 17

Hypercapnia and hypoxemia values

Answer 17

PaCO2 >45
PaO2 <60

Question 18

Early manifestations:

Answer 18

Mental status changes
HTN
Increased RR
Increased HR
Mild HTN

Question 19

Hypoxemic RF signs:

Answer 19

Cyanosis (late sign)
Paradoxical breathing
Retractions
Nasal flaring

Question 20

Hypercapnic RF signs:

Answer 20

Pursed-lip breathing
Morning headache
Retractions
Rapid shallow breathing
Tripod position

Question 21

Type 1 signs:

Answer 21

Dyspnea, irritability, confusion, fits, somnolence, cyanosis, pulmonary HTN

Question 22

Type 2 signs:

Answer 22

High CBF, headache, blurred vision (papilledema), excitation, coma, warm extremities, asterix, collapsing pulse due to hypercapnic peripheral vasodialtion, acidosis

Question 23

Aims of O2 therapy:

Answer 23

Maintain PaO2 at 55-60mmHg or more
SaO2 at 90% or more
@ lowest O2 conc. possible

Question 24

Nasal oxygen catheter
____ O2 device
Max flow:

Answer 24

Low
6L/min @ 45%

Question 25

Venturi mask:

Answer 25

Up to flow 24-30L/min Total gas flow
Maximum 60%

Question 26

Non-rebreathing mask:

Answer 26

High O2 device
2 valves prevent: entrapment of air during inspiration, retention of exhaled gas during expiration

Question 27

PPV

Answer 27

Via endotracheal tube, tracheostomy tube
Invasive

Question 28

Non-invasive PPV

Answer 28

B-level positive airway pressure (BiPAP)
Continuous positive airway pressure (CPAP)

Question 29

Gold standard to monitor ETI?

Answer 29

Capnography
Measure ETI
5 to 6% (35-45mmHg)

Question 30

ETI complications:

Answer 30

Ttrauma, hypoxia, dysrhythmia, aspiration, intubation of exophagus or R main stem bronchus, laryngospasm, bronchospasm

Question 31

Advantages of TT over ETT:

Answer 31

Faster weaning
Enhanced patient comfort, communication
Oral feeding
More effective clearing of secretions

Question 32

Disadvantages of TT:

Answer 32

Risk of hemorrhage, pneumothorax, tracheal stenosis, accidental decanulation
Requires operative procedure

Question 33

Parts of tracheostomy tube
Types:

Answer 33

Neck plate, obturato, innner cannula
Fenestrated, cuffed, cuffless

Question 34

Tissue hypoxia occurs at:

Answer 34

Venous PaO2 <20mmHg (SVO2<40%)
Arterial PaO2 <38mmHg (SVO2<70%)

Question 35

Coniotomy passes through:

Answer 35

Skin, SC tissue
Lamina superficialis
Lamina Pretrachealis
Median cricothyroid ligament and mucosa