Respiratory failure Flashcards
(35 cards)
Typical pH range for chronic vs acute respiratory failure:
- Acute - pH falls quickly below 7.2
- Chronic - pH typically greater than 7.2 due to HCO3 retention
4 pathophysiological factors causing hypoxemic respiratory failure:
- 1 - Ventilation-perfusion mismatch
- 2 - Shunting
- 3 - Diffusion limitations
- 4 - Alveolar hypoventilation
Ventilation perfusion mismatch - explain with formula
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
Explain what is shunting and the causes
- 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
How much is the anatomic shunting?
5% maximum
Diffusion limitations - cause and etiology
- Thickened alveolar membrane due to:
- Emphysema
- Recurrent PE
- pulmonary fibrosis
Alveolar hypoventilation - definition, causes?
- Ventilation falls under 4L/min
- Restrictive lung disease
- CNS depression
- Chest wall dysfunction
- Neuromuscular disease
Hypoxemic vs hypercapnic respiratory failure
Hypoxemic is PaO2 lessthan 60
Hypercapnic is PaCO2 greater than 50
Hypercapnic respiratory failure causes (6):
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
Early signs of resp. faliure (non-specific):
- Mental status change
- Increased HR
- Increased RR
- Mild HTN
Type 1 resp. faliure symptoms:
- Dyspnea, irritability, confusion, fits, somnolence, CYANOSIS, pulmonary HTN
Prolonged expiration, nasal flaring, tachypnea, dyspnea
Type 2 resp. failure symptoms:
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
Normal values of pH, CO2, HCO3:
7.35-7.45
35-45
23-27
If increased PaCO2 accompanies decreased PaO2, then ARF is secondary to?
Alveolar hypoventilation
Minute ventialtion formula:
Minute ventilation = Tidal volume X respiratory rate
Types of Oxygen therapy:
Nasal oxygen catheter
Venturi mask
Non-rebreathing mask
Intubation
Tracheostomy
Coniotomy
Hypercapnia and hypoxemia values
PaCO2 >45
PaO2 <60
Early manifestations:
Mental status changes
HTN
Increased RR
Increased HR
Mild HTN
Hypoxemic RF signs:
Cyanosis (late sign)
Paradoxical breathing
Retractions
Nasal flaring
Hypercapnic RF signs:
Pursed-lip breathing
Morning headache
Retractions
Rapid shallow breathing
Tripod position
Type 1 signs:
Dyspnea, irritability, confusion, fits, somnolence, cyanosis, pulmonary HTN
Type 2 signs:
High CBF, headache, blurred vision (papilledema), excitation, coma, warm extremities, asterix, collapsing pulse due to hypercapnic peripheral vasodialtion, acidosis
Aims of O2 therapy:
Maintain PaO2 at 55-60mmHg or more
SaO2 at 90% or more
@ lowest O2 conc. possible
Nasal oxygen catheter
____ O2 device
Max flow:
Low
6L/min @ 45%
