Respiratory rate with the help of power lab and Breath holding effect.

Lecture Outline

Learning Objectives:

At the end of the practical, student should be able to:

•Describe normal respiratory movements.

•Note the relative durations of inspiration and expiration.

Object

In this exercise, you will record normal and rapid breathing, and examine the effects of holding your breath after inhaling and after exhaling.

Theory:

Definition:

Respiration refers to the mechanisms for obtaining oxygen from the air and delivering it to the tissues, while eliminating carbon dioxide from the body.

  • Cells in body consume oxygen and produce carbon dioxide.
  • gases are exchanged between cells and blood through lungs.
  • Breathing movements pump air in and out of the lungs, where close contact between air and blood occurs, allowing interchange of oxygen and carbon dioxide between them.
  • lungs are 'blind sacs'; that is, there is one way in and out.
  • To fill these sacs breathing must be tidal; an in and out series of events rather than continuous.
  • The internal structure of the lungs consists of a series of branching tubes that carry air to the alveoli

Alveoli (air sacs) are tiny thin-walled, highly vascularized structures where respiratory gas exchange occurs. In the alveoli and throughout the body, gases diffuse down their concentration gradients. This is usually expressed in terms of the partial pressures of the gases (PO2 , PCO2) so that comparisons can be made easily between the 'concentrations' of the gases in the atmosphere and in solution in the body. This comparison is possible because the concentration of dissolved gas is proportional to the partial pressure of the gas; this is known as 'Henry's Law'.

Principal muscle activity in quiet breathing

The principal muscle activity in quiet breathing is rhythmic contraction of the diaphragm. During quiet inspiration, contraction of the diaphragm increases the volume of the chest, the intrathoracic pressure therefore falls and air flows into the lungs from the atmosphere down this pressure gradient. In quiet breathing, expiration is mainly passive. The diaphragm relaxes and the elastic recoil of the lungs raises intrathoracic gas pressure above atmospheric. Rib movements also occur in quiet breathing through the activity of the intercostal muscles, but are of small amplitude and thus contribute relatively little to respiration under these conditions (Figure 2).

Figure 2. Diaphragmatic positions and changes in lung volume at the ends of inspiration and expiration.

Forceful Breathing :

  • In forceful breathing, rib movements are obvious, and the volume enclosed by the ribcage changes to a greater extent.
  • In addition, other muscles are recruited.
  • The sternomastoid muscles of the neck assist in raising the sternum in forceful inspiration.
  • During expiration abdominal muscles raise the pressure in the abdomen and push the relaxed diaphragm up, providing a powerful expiratory force.
  • Spontaneous breathing is controlled by the respiratory center in the medulla of the brain.
  • The respiratory center ensures that gaseous exchange at the lung matches the requirements of the body
  • The respiratory center has chemoreceptors that are sensitive to the partial pressure of carbon dioxide (PCO2) and pH of the cerebral spinal fluid.
  • Chemoreceptors sensitive to oxygen partial pressure (PO2 ) are located in the aorta and carotid arteries.

Procedure

Fasten the respiratory belt around the abdomen of a volunteer, as shown. The transducer should be:

  • At the front of the body, level with the navel.
  • Tightened sufficiently that it remains under tension even when the subject fully exhales.

The respiratory belt transducer can be used over clothing, and it doesn't matter whether the volunteer is sitting or standing, so long as they are comfortable (this is quite a long exercise). Because breathing patterns differ, you may need to reposition the transducer over the chest rather than the abdomen to get the best signal.

Connect the plug on the respiratory belt transducer cable to Input 1 on the front of the PowerLab.

It is important when recording normal respiration that the volunteer is facing away from the computer screen and is not consciously controlling breathing. The volunteer mayhave to stare out a window or read a book to avoid conscious control of respiration.

  1. Click Start.
  2. Ask the volunteer to breathe rapidly for a few seconds, and then to breathe slowly. Examine the Breath Rate channel, there should be obvious changes in rate.
  3. Enter a comment: 'Baseline 1' in the slow breathing region of the data.
  4. Click Add.
  5. Record 2-3 minutes of normal, quiet breathing and observe the trace.
  6. Enter a comment: 'inhale, hold'.
  7. Click Add, and immediately ask the volunteer to take a deep breath and hold it in for as long as possible.
  8. Enter a comment: 'breathe'.
  9. When the volunteer begins to breathe again, click Add .
  10. Wait until a normal (baseline) breathing pattern resumes; then let the volunteer rest and breathe normally for another 2-3 minutes.
  11. Enter a comment: 'exhale, hold'.
  12. Click Add, and immediately ask the volunteer to breathe out fully and hold the breath for as long as possible.
  13. Enter a comment: 'breathe'.
  14. When the volunteer begins breathing click Add.
  15. Continue recording until a normal (baseline) pattern resumes.
  16. Click Stop.

The volunteer can now relax and breathe normally.

Analysis

  1. In the Breathing channel, place the Marker on the large peak following the comment 'inhale, hold'.
  2. Move the Waveform Cursor to the start of the first breath afterwards, which should be preceded by the comment 'breathe'.
  3. Click to place the selected data in the Value panel and drag it from the Value panel into the appropriate cell of the table.
  4. Drag the Marker to the large (negative) peak right after the comment 'exhale, hold'.
  5. Move the Waveform Cursor to the start of the first breath afterwards, which should also be preceded by the comment 'breathe'.
  6. Click to place the selected data in the Value panel and drag it from the Value panel into the appropriate cell of the table.