Mechanics of breathing

Question 1

The average Pediatric BVM holds how much volume?

Answer 1

500 mL

Question 2

The average Adult BVM holds how much volume?

Answer 2

1600 mL

To put this into perspective, even if you delivered 2/3rds of that 1600 mL volume (about 1000 mL), that would still be 8ml/kg of IBW for Yao Ming (7’6” tall).

Question 3

Define the term “Dead Space.”

Answer 3

Anatomical space in the airways that does not participate in gas exchange

Question 4

f stands for

Answer 4

frequency (RR)

Question 5

Define the abbreviation “Va.”

Answer 5

Va refers to the alveolar ventilation.

This is the air that is available for gas exchange.

Question 6

Your patient has a frequency of 12 and tidal volume of 400. What is their current Minute Volume (MV)?

Answer 6

Minute Volume= respiratory rate (f) over 1 minute x tidal volume.

12 x 400 = 4800ml or 4.8L

Question 7

An adult patient has a Vt (tidal volume) of 450mL and a f (frequency) of 10. The patient’s ideal body weight is 150 lbs. What is their alveolar minute volume?

Answer 7

We calculate this by

1. ) subtracting the dead space (1mL / lbs)
2. ) from the tidal volume,
3. ) then multiplying by the frequency.

(450 - 150) x 10 = 3000.

Question 8

When we choose to ventilate an adult patient with a ventilator or BVM, we always must keep in mind that the volume (ml) we deliver will be based on their __________.

Answer 8

Height / sex:

The size of our rib cage and lungs, where our diaphragm sits, and how much volume our lungs can handle is all based on our height and sex.

Question 9

Excessive positive pressure ventilation will result in a decreases in cardiac output through this mechanism:

Answer 9

decrease venous return.

Positive pressure ventilation will decrease cardiac output by impeding venous return.

Question 10

A normal adult cardiac output (CO) is approximately _______L / min.

Answer 10

4-8 L/min

Something I’ve always found interesting about minute volume is that our cardiac output is usually the same reference range - both are 4-8 liters per minute. In other words, the amount of air coming in and out and blood going around and around is the same in liters / min.

Question 11

While ventilating a 5’10” male with a goal of 8cc/kg, which of the following is an appropriate tidal volume?

Answer 11

This patient has an idea body weight of 73 inches (50kg because he is at least 5 ft and 2.3 x the additional 10 inches).

50kg + (2.3 x inches past 5ft (10”) )

50 kg + 23 = 73

73 x 8cc = 584

This is approximately 600 mL’s.