101

Question 1

Hypoxaemia

Answer 1

Reduction below normal levels of O2 in arterial blood.
PaO2= 80-100 mmHg
<8PKa

Question 2

Hypoxia

Answer 2

Reduction below normal levels of oxygen in tissues necessary for cellular metabolism

Question 3

Hypercapnia

Answer 3

Abnormally raised CO2 levels in the blood >40mmHG ,>6pKa
From dead space and hypoventilation
Respiratory acidosis

Question 4

Types of Hypoxia

Answer 4

Hypoxaemia
Stagnant Hypoxia
Anaemic Hypoxia
Histotoxic hypoxia

Question 5

Causes of Hypoxaemia

Answer 5

Hypoventilation
Diffusion restriction/abnormality - ILD,PF
V/Q mismatch
Decreased O2 level in inspired air
Venous to arterial shunt (tetralogy of Fallot)

Question 6

Tetralogy of Fallot

Answer 6

LV Hypertrophy
VSD - Ventricular Septal Defect
Pulmonary Stenonis - thickening and narrowing
Over-ridding Aorta

Question 7

Anaemic Anaemia

Answer 7

Decr in quantity of Hb in blood or affinity for O2
.CO poisoning
.Fe Poisoning

Question 8

Stagnant/Ischemic Hypoxia

Answer 8

Inadequate blood flow leading to inadequate O2 supply to tissues - tissue congestion and ischaemia
Systemic- Shock
Local- LHF, Thrombosis, Arterial stenosis

Question 9

Histotoxic Hypoxia

Answer 9

Adequate O2 delivery but tissue unable to use the O2

• Mitochondrial damage
  Cyanide, radiation,toxins
  -B vit deficiency

Question 10

Respiratory Failure

Answer 10

Syndrome where gas exchange is impaired ; O2 uptake or CO2 elimination
Either; Hypoxaemia(Type 1 PaO2<60mmHg) or Hypercapnia (Type 2)

Question 11

Effects of Hypoxaemia

Answer 11

Restlessness
Confusion
Tachycardia
Tachypnoea
Poor peripheral 
Central cyanosis
Sweating

Question 12

Hypercapnia

Ventilatory failure

Answer 12

Decrease in alveolar ventilation ; Balance between load and drive (Neuromuscular Compentence) determines ability to sustain alveolar ventilation
Decrease in TV
Decreased in RR

Question 13

Causes of Hypercapnia

Answer 13

Won’t breath - Central drive depression _ decreased RR ; Sedation, narcotic overdose
Can’t breath enough - Pulmonary _ Overwelmed Mechanism; COPD, Asthma exacerbations
Can’t breath -Neuromuscular _ insufficient TV ; GB syndrome, Polio, Myasthemia Gravis, Botulism

Question 14

Components of Respiratory drive to breathe

Answer 14

Rhythmic breathing - Central Respiratory Pattern Generator (CRPG) in Pons and Medulla
Motor Neurons - activate resp skeletal muscles
Chemoreceptors and streth receptors sense alterations in blood gas or ventilatory performance ffeedbacks to CRPG to alter appropriately (-ve feedback mechanism)

Question 15

Effects of hypercarpnia

Answer 15

Irritability
Incr Somnolence
Tachycardia
Papilloedema
Flushed warm skin
Sweating
Tremore
Confusion
Coma
Myoclonic jerks
Seizure

Question 16

Detection of respiratory failure

Answer 16

Clinical examination
Pulse oximetry
Cal of A-a gradient - normal excludes pulmonary conditions
Blood gases and serum electrolytes

Question 17

ARDS

Answer 17

Respiratory failure from non cardiac related factors
Lung injury leading to inflammation, incr permeability (protein rich exudate), Oedema
Direct or indirect
Sepsis
Trauma
Penumonia
Apspiration

Question 18

ARDS confirmation

Answer 18

Acute
Low oxygenation
Not cardiogenic
Bilateral pulmonary infiltrates

Question 19

Aa gradient calculation

Answer 19

A-a Gradient = PAO2 – PaO2.
PAO2 = (Patm – PH2O) FiO2 – PaCO2/RQ

Easy
Age/4 + 4 or Age/10+4