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9.3 Medical technology - Bionics 4. Life support systems

Syllabus reference ( October 2002 version)
4. Life support systems can be used to sustain life during operations or while the body repairs itself	Students learn to: describe the structures of the respiratory system and identify their function including trachea bronchi alveoli capillary network around the alveoli explain why cardio-pulmonary resuscitation techniques can maintain life when the heart has ceased beating identify that artificial lungs remove carbon dioxide and replace it with oxygen discuss the type of operations that would require the use of an artificial lung identify the devices that constitute life support systems in any major hospital	Students: perform an investigation to model the action of the diaphragm in inhalation and exhalation perform a first-hand investigation to identify carbon dioxide in inhaled air and in exhaled air and determine which has the greater concentration gather, process and present information from secondary sources to identify monitoring and other devices that constitute life support systems and use available evidence to explain their roles in maintaining life

Extract from Senior Science Stage 6 Syllabus (Amended October 2002). © Board of Studies, NSW.

[Edit: 10Sept 08]

Prior learning: Preliminary module 8.4 (subsection 2)

Science Stages 4-5 syllabus: Outcomes 4.8 (content 4.8.1 a, b, c, d; 4.8.4 b, c, d and 4.8.5 a, b), Outcome 5.8 (content 5.8.1 a), Outcome 5.12 (content 5.12 d, f, g)

Background:The respiratory system is acutely critical to the proper functioning of the body. The malfunction of the respiratory system quickly affects the quality of life. Science has provided several ways to support the respiratory system when the body can't do the job alone, and this has led to an increase in the survival rate after major operations or accidents.

perform an investigation to model the action of the diaphragm in inhalation and exhalation

Perform the investigation by selecting a procedure like that described below and carrying it out, recognising where and when modifications are needed and analysing the effect of any adjustments that you make. Write an account to explain the effect of the movement of the diaphragm.

Modelling the lungs A simple experiment may be set up using a bell jar, balloon and a cork with glass tube inserted. A second balloon or rubber membrane may be stretched and tied over the base of the bell jar. This second balloon models the diaphragm.

Pull the diaphragm down and note what happens to the balloon.
Let the diaphragm return to its normal position and note what happens to the balloon.
Push on the diaphragm and note what happens to the balloon.

perform a first-hand investigation to identify carbon dioxide in inhaled air and in exhaled air and determine which has the greater concentration

Perform the investigation by selecting a procedure like that described below and carrying it out, recognising where and when modifications are needed and analysing the effect of any adjustments that you make. You should be able to record whether inhaled air or exhaled air has the greater concentration of carbon dioxide.

Testing inhaled and exhaled air

Construct an apparatus like the following, using clean basic laboratory equipment. Carbon dioxide will make limewater go cloudy.
Breathe in and out through the mouthpiece. Observe the colour of the limewater over a period of a few minutes.
Look for differences in the cloudiness of the limewater in the two flasks.
This will give you a qualitative answer about the concentration of carbon dioxide in exhaled and inhaled air. To arrive at an amount you will need to use more sophisticated equipment or get the values from a text book, such as a senior biology book.

describe the structures of the respiratory system and identify their function including

trachea
bronchi
alveoli
capillary network around the alveoli

Trachea

The trachea is the long tube connecting the pharynx, mouth and nasal cavities to the bronchi.
The trachea is supported from collapse by rings of cartilage, which occur around the full length of the tube. The cartilage supports the trachea during inhaling, when the pressure in the lungs is negative.

Bronchi

The bronchi connect the trachea to the lungs.
There are two bronchi, one going to each lung, each having a similar structure to the trachea, with cartilage rings for support during times of negative pressure.

Alveoli

The bronchi divide into smaller bronchioles, which eventually terminate in the gaseous exchange zone of the lung, the alveoli.
There may be as many as 100 million alveoli in each lung.
The walls of the alveoli are thin and moist, allowing gases to dissolve and move easily from inside the alveoli to the blood capillaries that surround the alveoli.

Capillary network around the alveoli

The capillaries are fine blood vessels that transport high-oxygen blood from the lungs to the pulmonary vein (to be taken to the heart and pumped to the body) and low-oxygen blood from the pulmonary artery to the lungs for exhalation.
The intricate capillaries surround each alveolus, maximising the surface area.
When the oxygen enters the alveolus it dissolves in the cells of the moist alveolar wall, moving through the wall into the capillary and then to the pulmonary vein.

Respiratory System Your Total Health, USA

Human Lung Wikipedia, USA

explain why cardio-pulmonary resuscitation techniques can maintain life when the heart has ceased beating

Cardio-pulmonary (heart-lung) resuscitation (CPR) is a combination of expired air resuscitation and external cardiac compression.
Life may be maintained by the use of CPR, because CPR effectively takes over the breathing and the circulation in a person whose body has stopped carrying out these functions.
CPR prevents brain damage by keeping vital organs supplied with oxygen.

Be prepared

Resuscitation Everyone should learn, as it may save someone's life one day. St John Ambulance,
Australia

identify that artificial lungs remove carbon dioxide and replace it with oxygen

An artificial lung works on the same principles as natural lungs, but it works from an external perspective. The pressure inside the iron lung is varied, causing the thoracic cavity to move up and down and forcing breathing.
In this way the artificial lung removes carbon dioxide from the lungs and replaces it with oxygen.

The iron lung

Artificial lungs are not a new development. In fact they have been in use for many years. In the 1940s the “iron lung” was used in treating polio.

Iron Lung . Wikipedia, The Free Encyclopedia, USA

discuss the type of operations that would require the use of an artificial lung

Artificial lungs may be used to treat patients with acute respiratory distress syndrome, pneumonia and chronic lung disease, as well as organ transplant patients and patients in intensive care.

A current artificial lung in use is the Extra Corporeal Membrane Oxygenator. (ECMO) Children's Hospital Boston, Masuchusetts, USA

gather, process and present information from secondary sources to identify monitoring and other devices that constitute life support systems and use available evidence to explain their roles in maintaining life.

Gather informationby looking in encyclopaedias, scientific and popular journals and magazines and medical text books, as well as searching the Internet under specific titles such as heart-lung machines, pacemaker and kidney machine. If you have access to CD-ROMs, such as Encarta or Encyclopedia Brittanica, search in them under specific titles also.

Hint about searching for information

Searching using “life support systems” will usually find information on things like life support systems in space and under water.

A definition of artificial life support High Beam Encyclopedia, USA

Information on renal dialysis Howstuffworks, Inc., USA
Process the information. One way could be to type a summary of the information your collect as you read it from various sources into a table in a spreadsheet using the following headings: Device, Role in maintaining life, Source of information. Keep the information simple, with just the facts that were asked for in the dot point. If different sources give you different information about the one device, check a third source or assess which source would be more reliable e.g. a weekly magazine such as New Idea may not be as accurate as Australasian Science. This approach also allows you to efficiently share information gathered by other students.
Present the information by sorting rows of your table into useful and logical groupings related to the devices identified.
Use the evidence available in your table to write general explanations for the roles of monitoring and other devices in maintaining life.

identify the devices that constitute life support systems in any major hospital

Life support is defined as any therapeutic technique or device used to maintain life function.
There are many devices that are considered as “life supporting” in hospitals, including suction machines, medications and drips. (See above dot point for many examples.)
The life support machines pictured by many are the ones used in intensive care, or in palliative care. These systems consist basically of a ventilator unit (to assist breathing) and a heart rate monitor (to alert staff to any changes in heart beat).