Question

1. Why does predicted vital capacity vary with height? (2pts)

2. Explain how factors other than height might affect lung capacity? (2pts)

3. How would the volume measurements change if data was collected after vigorous exercise? (2pts)

4. What is the difference between volume measurements and capacities? Why does this difference exist? (2pts)

5. Discuss the four general components of an instrument that acquires a body signal, and relate them specifically to the BIOPAC exercise. (6pts)

6. How did your vital lung capacity compare with the predicted vital lung capacity? (2pts)

7. Maximal voluntary ventilation decreases with age. Why? (2pts)

8. Asthmatics tend to have their smaller airways narrowed by smooth muscle constriction, thickening of the walls, and mucous secretion. How would this affect vital capacity, FEV1, and MVV? (2pts)

9. Bronchodilator drugs open up airways and clear mucous. How would this affect the FEV and MVV measurements? (2pts)

10. Would a smaller person tend to have less or more vital capacity than a larger person? Why? (2pts) Finally, discuss the following.

11. Were the devices used in the labs user friendly? Who were the instruments designed to be used by? What happens if they are used incorrectly? Did you have any problems using any of the equipment? What were they? How do these problems with the equipment affect their clinical use? (3pts)

12. How are respiratory volume measurements clinically useful? What sort of problems can these measurements identify? (This may require some additional independent research. Be sure to cite your sources.

Answer 1

1. Why does predicted vital capacity varies with height? (2pts)

Vital Capacity (VC) is the volume change of lung after maximal inspiration followed by maximal expiration. It is measured as the sum of tidal volume, inspiratory reserve volume and expiratory reserve volume. The normal range of vital capacity of normal adults is between 3 to 5 litres.

The lung size and thoracic cavity size increases with increased height. This will proportionately affect the tidal volume, inspiratory reserve volume and expiratory reserve volume and thereby the vital capacity.

The equations for Predicted Vital Capacity

Male: Vital Capacity = 0.052H – 0.022A – 3.60

Female: Vital Capacity = 0.041H – 0.018A – 2.69

H:      Height in centimeters

A:      Age in years

This formula also uses the height as a parameter to calculate vital capacity.

2. Explain how factors other than height might affect lung capacity? (2pts)

Lung function values like volumes and capacities are traditionally based on anthropometric measurements like weight, height, sex, and age.

Forced Vital Capacity (VC) and Forced Expiratory Volume₁ (FEV₁) reduces with age, and the volumes and capacities like RV and FRC, increase.

TLC, VC, RV, FVC and FEV₁ values are also affected by height since they are proportional to body size.

A tall individual will experience the greater decrease in lung volumes as they get older and as the stature changes.

The variables like FRC and ERV, decline greatly with an increase in weight, to the extent that tidal volume is close to that of RV. (morbidly obese patient)

Gender: The airways of men are longer than women and that causes greater specific resistance in the respiratory tract. Their consumption of oxygen is higher than men under similar conditions of physical intensity.

Position: Lung volumes are more in standing than in other positions.

Physical exercise will improve some lung volumes and lung capacities by strengthening and training the lungs.

Geographical location: People living in sea level have lesser lung capacity than living in high altitude. The body's diffusing capacity increases in order to process more air. The air pressure within the breathing system must be lower in order to inhale compared to the lower environmental air pressure at higher altitudes. The diaphragm has a tendency to lower to a greater extent during inhalation and causes an increase in lung volume.

Air pollution exposure affects FVC and FEV1 in healthy adults even at low concentrations.

Physiological changes like pregnancy also cause the change in lung volumes. FRC drops to 18-20% due to an inability of the diaphragm to expand affected by the growing uterus.

3. How would the volume measurements change if data was collected after vigorous exercise? (2pts)

During exercise the cardiothoracic function increases to meet the excess demand for gas exchange to provide energy and remove carbon dioxide, the waste product created when you produce energy. In order adjust with the extra demand, breathing has to increase from about 15 times a minute (12 litres of air) then resting, up to about 40–60 times a minute (100 litres of air) during exercise. The circulation increases to meet the oxygen demand of the muscles.

• Tidal volume (VT).

It is the amount of air inspired or expired during normal tidal breathing. Tidal volume increases with activity to accommodate the increased need for gas exchange. VT at rest for men and women are 500ml and 400ml respectively.

• Inspiratory Reserve Volume (IRV).

Maximum air that can be inspired above the volume inspired tidally. IRV decreases with exercise.

• Expiratory Reserve Volume (ERV).

The maximum volume of air that can forcibly be expired beyond a normal tidal expiration. The ERV also decreases when exercising.

• Residual Volume (RV). The residual volume is the amount of air that remains in the lungs following a maximal expiration, and can only be forced out of the lungs by collapsing the lungs. The RV for men is approximately 1200 ml and approximately 900 ml in women.

Fig. 11.3. Illustration of a spirometer recording depicting measurements of the primary lung volumes (left) and the lung capacities (right)

There are also four lung capacities, each of which is the sum of two or more primary lung volumes.

• Total Lung Capacity (TLC). The total lung capacity is the maximum amount of air that can be held within the lungs at one time and is the volume of air in the lungs following a maximal inspiration. TLC is the sum of all four primary volumes (TLC = IRV + VT + ERV +RV).

• Vital Capacity (VC). The vital capacity is the maximum amount of air that can be exchanged between the lungs and atmosphere in a single breath, and is the volume of air that can be forcibly expired from the lungs following a maximal expiration. The vital capacity is the sum of the three primary volumes that can be directly exchanged with the atmosphere (VC = IRV + VT + ERV).

• Inspiratory Capacity (IC). The inspiratory capacity is the maximum amount of air that can be inspired following a normal tidal expiration. It is the sum of the inspiratory reserve volume and the tidal volume (IC = IRV + VT).

• Functional Residual Capacity (FRC). The functional residual capacity is the volume of air that remains in the lung following a normal tidal expiration. It is the sum of the expiratory reserve volume and the residual volume (FRC = ERV + RV).

4. What is the difference between volume measurements and capacities? Why does this difference exist? (2pts)

There are four lung volumes like tidal volume, expiratory reserve volume, inspiratory reserve volume, and residual volume. Lung capacities are measurements of two or more volumes.

The vital capacity (VC) is the maximum amount of air that can be inhaled or exhaled during a respiratory cycle(inspiration and expiration).

It can be measured as the sum of the expiratory reserve volume, tidal volume, and inspiratory reserve volume.

The inspiratory capacity (IC) is the sum of the tidal volume and inspiratory reserve volume.

The functional residual capacity (FRC) measures the amount of additional amount of air that can be exhaled after a normal exhalation.

The total lung capacity (TLC) is the sum of the residual volume, expiratory reserve volume, tidal volume, and inspiratory reserve volume.

Spirometry is the technique used to measure Lung volumes. As the lung capacity are measurements of two or more volumes, it can be estimated from spirometry values.