Respiratory Failure + Mechanical Ventilation and Oxygen therapy

What is the normal A-a gradient

0-10 mmHg

What are the pros and cons of nasal cannulas

Pros: Easy to use, can be worn all the time; cons: Low max of inspired O2, unpredictable concentration

What is the normal PaO2: FiO2 ratio

300 to 500 mmHg

What are the pros and cons of masks

Pros: Provide more O2 than nasal cannula; Cons: Can’t eat while using, not as convenient

What is oxygen dilution

When you give NC at 6 LPM at 45% O2 and patient breathing 20 L/min at room air → FiO2 going to trachea is closer to 21% not 45%

What are high flow delivery systems

Can give 20-60L of O2, better used for patient that has high inspiratory drive (provides higher FiO2

What is the advantage of using a high flow system instead of nasal cannula

High flow delivery washes out dead space and decrease work of breathing (+ humidified means that there won’t be nosebleed)

What are the indications for ventilator

Impaired gas exchange, increased work of breathing

What is the benefit of ventilator

Power to get air into lung, control breathing rhythm, high concentration of O2

What is respiratory failure

Dysfunction of respiratory system causing abnormal gas exchange

What is type 1 and type 2 respiratory failure

Type 1: LOW O2; Type 2: HIGH CO2

What are the ranges of hypoxemia

Normal: 80-100 mmHg; mild hypoxemia: 60-80 mmHg; moderate hypoxemia: 40-60 mmHg; severe <40 mmHg

What are causes of hypoxia

Respiratory failure, circulatory failure (not enough O2 to organ), anemia (lack RBC), histotoxic hypoxia (cyanide)

What is the pathophysiology of type 1 respiratory failure

Hypoventilation, shunt, V/Q mismatch, diffusion abnormality, decreased inspirated PO2

What are the NEUROLOGICAL causes of hypoventilation

Medulla disease, respiratory center damage, anterior horn cell disease, high C spine injury,

What changes the rate of diffusion

Direct to solubility, inverse to molecular weight

What changes the velocity of the gases that are dififusing

Direct to diffusion rate, area, pressure gradient; inverse to thickness

What causes hypercapnic respiratory failure

Hypoventilation (from brain, spinal cord, nerve, muscle), increase dead space, increase CO2 production

What is the effect that increased dead space has on hypoventilation

Ventilation is wasted → Inhale 500 but only 250 ml goes through gas exchange

What is the mechanism of the botulinum toxin and how does it relate to respiratory failure

Binds to nerve endings and cleaves SNARES needed for ACh release → Muscle does not contract → Causes paralysis to breathing muscles

How does a pulse oximeter work

There are sensors that detect O2 based on how infrared and red light passes through your finger → Normal is 95%-100%

What effects the pulse oximetry accuracy

Movement, too much ambient light, electromagnetic interference, bad peripheral perfusion, blue/green/black nail polish

Does pulse oximetry estimates vary with race

Yes, it tends to overestimate more for asians than other races

What formula is used to calculate respiratory failure development

FVC/NIF

What does capnography measure

End tidal CO2/PET CO2 which is close to PACO2

What is the benefit of capnography

Detects hypoventilation post anesthesia