Lab Week 4: Respiratory System

Anatomy & Physiology

Lab Week 4: Respiratory System

Station 1 : Using the respiratory lab materials

a)Using a clean and disinfected mouthpiece, Measure your tidal volume (Vt) and fill out your Tv on the chart provided. Look at the variety of Vt’s in the class.

Clean the mouthpieces with alcohol once you are done! Let dry

b)What is your FEV? Over what time period is it measured in?

c)Measure resting breath rate and active breath rate. Put it on the chart provided

d)Now, since you know your Tv, and RR (at rest) what is your minute ventilation? How does this change during exercise.

d)What is meant by “ breath control”. When would it be useful?

Try the breath control exercise – please clean well with alcohol after use

Station 2: Ventilation/Perfusion Ratio

VENTILATION AND PERFUSION

Ventilation is defined as the flow of air into and out of the alveoli.
Perfusion is defined as blood flow to the alveoli.

The lungs are composed of about 300 million alveoli that are capable of gas exchange. Gas is exchanged between the blood and the air. Thus, it depends on both ventilation and perfusion.

To be the most efficient, the right proportion of alveolar air flow (ie.ventilation) and capillary blood flow (perfusion) should be available to each alveolus. Any mismatch is called ventilation-perfusion inequality. In an ideal lung, the V/Q ratio=1, ie. they are equal (V= ventilation and Q = perfusion).
To understand the concept of V/Q inequalities it is best to visualize the simplest situations first. Thus, the two extremes of this phenomenon:

1) A ventilated alveoli with no blood supply (see alveolar dead space).

2) Blood supply to an alveoli that is not ventilated (this is a shunt).

The major effect of any ventilation-perfusion inequality situation is that it lowers the PO2 of systemic arterial blood. In other words, the O2 in the alveoli will remain much higher than the O2 in the arterial blood.

Go to this web site to look at the exercise in VQ Mismatch

Station 3: Compliance/Resistance

A. Resistance

Resistance to air flow is caused by two forms of resistances: Airway resistance and Tissue resistance

AIRWAY Resistance to flow:

The first component of lung resistance is called airway resistance. Airway resistance is composed of:
1- Frictional resistance to flow (discussed below);
2- Acceleration or deceleration of gas flow due to changes in cross sectional area (see Bernoulli Effect). (

Frictional resistance:

In a branched system, like that of our airways, frictional resistance depends on the individual resistances of each pipe and greatly depends on the manner in which they are connected.

A small diameter causes a higher resistance, but the large number of parallel airways in that generation reduces the overall resistance.Remember that if you had 5 identical resistances in parallel, the total resistance would be 1/5 of any single resistance. Now imagine you have 20, 30 or 100 parallel resistance. The total resistance would then be 1/100 of any single resistance. At this distal point in the airways, the resistances become almost insignificant. Most of the overall airway resistance comes from generations 0 through 8.

During normal tidal breathing, both components of airway resistance contribute majorly to air flow resistance.

Look at

B. Compliance Compliance = V / P

Compliance is defined as the change in the volume of a closed system over the change in the pressure distending it.

To explain the concept of compliance, we will use the example of a balloon.
Compliance is the ease with which a balloon (or lung) can expand (ie. increase in volume). Thus the lower the pressure required to inflate the balloon, the greater the compliance.

When a balloon is completely deflated (a collapsed lung), a high pressure is required to begin inflating it. As it is being inflated or if there is some residual air (like at RV), some of the elastic fibers in the balloon break, making it easier (ie. requiring less pressure) to continue inflating the balloon.

As the balloon approaches its maximal distension (like at TLC), the elastic fibers of the balloon have less potential stretch, and therefore it becomes more difficult (requiring a higher pressure) to inflate the balloon further. If a high enough pressure is maintained the balloon will explode.

Look at

Exercise in lab: attach the BVM to the compliance resistance machine.

1. Set to zero, set compliance and resistance also to zero (no springs, and dial to zero)

Have partner not look at machine and just bag gently.

What are the volumes they get with each “bag”?

Measure 10 of them

16

2`7

38

49

510

What is the average Tv your partner delivers with one hand?

Switch and have your partner measure you

1. Set Resistance to ‘100’ what do you notice about both the effort and the volume?

Switch and have your partner try it!

This mimics a moderate asthma patient

1. Set resistance to ‘200’. Now what do you notice about effort and volume. ?? How hard is it to keep Tv at a set amount? Bag for 2 full minutes. What happens to your hand? The volume delivered breath to breath? Imagine doing that from the house to the hospital!

This mimics a very severe asthmatic!

1. Attach the springs to the machine (both). This is the closest mimic to compliance. How does this change your ventilation?

Ensure your partner tries this as well

Station 4

Fill in the partial pressure diagram attached to the lab. Label the percentages of gases that dissolve or are carried by HGB in the blood, as well as the relative partial pressures of both gases at both the alveoli and at the tissues

Exercise 5: Workbook Exercises-

Look at list attached. These are the unique characteristics of infants vs adults respiratory systems. KNOW THESE

Match the condition with its description

Exercise 5 :Arterial Blood Gases

Medical Tests: The Respiratory System

1.What would you say about a patient with the following gases?

pH 7.31 paO2 42 paCO2 50 HCO3 22

1. Which patients (list 10 pathologies ) that would possible get ABG’s taken at the hospital?