Acoustic Guided System for Positing of Endotracheal Tube During Ventilation

Acoustic Guided System for Positing of Endotracheal Tube During Ventilation

1) Objectives:

The main objective of this seminar is to define respiratory system and explain its importance to multicellular organisms. Describe the ways that oxygen and carbon dioxide are transported in the bloodstream and to study available and modern techniques for position measurement of endotracheal tubes. The need for Instrumentation is to make proper and accurate measurement of various parameters related to medical science. All the measurement mainly depends on the detection, acquisition and display of biological signal.

2) Respiration:

Respiration is a vital function of all living organisms. The exchange of gases in any biological process is termed as Respiration. Respiration is to get Oxygen Into the Body and Waste Gases Out of the Body. To sustain life, the human body must take in oxygen, which combines with carbon, hydrogen, and various nutrients to produce heat and energy for the performance of work. As a result of this processes of Metabolism, which takes place in the cell, a certain amount of water is produced along with the principle waste product, carbon dioxide. The entire process of taking in oxygen from environment, transporting the oxygen to the cells, removing the carbon dioxide from the cells, and exhausting this waste product to the atmosphere must be considered with in the definition of respiration. It is the function of the Respiratory System to Transport gases to and from the circulatory system.

3) Level of Respiration:

Respiration occurs at different levels: The first is pulmonary ventilation in which air is moved into and out of the body. The second, external respiration, involves the exchange of oxygen and carbon dioxide between the lungs and the blood. The third is internal respiration, which involves the exchange of oxygen and carbon dioxide at the cellular or tissue level. Finally, cellular respiration is the utilization of oxygen to produce energy, which also produces carbon dioxide as a by-product.

4) Physiology of Respiration System:

Inspiration and expiration are accomplished by the creation of pressure gradients.

  1. The respiratory musculature is relaxed, atmospheric pressure equals chest cavity pressure, and so no air movement occurs.
  2. The external intercostals and diaphragm contract, moving the ribs up and out and the diaphragm down, respectively. This muscle action enlarges the chest cavity laterally, anterioposterially, and downward, increasing the volume. As a result chest cavity pressure is lower than atmospheric pressure and air flows in.
  3. The inspiratory muscles relax, and the chest cavity recoils, creating a pressure higher than atmospheric pressure. Air flows out. The respiratory cycle then begins again.

The main job of the Respiratory System is to get oxygen into the body and waste gases out of the body.

A respiratory system is a group of organs working together to bring about the exchange of oxygen and carbon dioxide with the environment. A single-celled organism living in water (Diffusion) gets its oxygen directly from its surroundings (the water). The oxygen easily diffuses across the Cell Membrane. Carbon dioxide also diffuses across the Cell Membrane; thus single-celled organisms do not need a Respiratory System. In Multicellular Organisms, Each Cell consumes Oxygen and produces Carbon dioxide. Large Multicellular organism must have a Respiratory System to ensure the effective exchange of gases with the Atmosphere quickly and efficiently to survive. This occurs every time an organism takes a breath. The atmosphere of planet Earth is approximately 78% Nitrogen and 21% Oxygen. The remaining 1% is made up of Carbon Dioxide, Water Vapor, and other trace gases. Humans are Air Breathers; our Respiratory System has adapted to these concentrations of gases in the Atmosphere. If the amount of Oxygen Falls much below 15 %, our Respiratory System will be Unable to provide enough Oxygen to support cellular respiration.

1. The Human Respiratory System consists of the Nose, Nasal Cavity, Pharynx, Larynx, Trachea, smaller conducting passageways (Branchi and Bronchioles) and Lungs.

2. The respiratory system may be divided into the upper and lower respiratory tract.

3. The upper respiratory tract consists of the parts outside the Thoracic (chest) cavity; the air passages of the Nose, Nasal cavities, Pharynx (windpipe) Larynx (voice box) and upper Trachea.

4. The lower respiratory tract consists of the parts found in the Thoracic (chest) cavity: the lower Trachea and the lungs themselves

5. Air enters the Respiratory System through the Mouth or Nose.

6. Air entering the Nose passes into the Nasal cavity. The Nasal Cavity is richly supplied with arteries, veins, and capillaries, which bring nutrients and water to its cells.

7. As air pushes back from the Nasal Cavity, it enters the Pharynx. The Pharynx is located in the back of the mouth and serves as a passageway for Both air and food. When food is swallowed, a Flap of Cartilage called the Epiglottis, presses down and covers the opening to the air passage (ever have food go “Down the Wrong Way”?).

8. From the Pharynx, the air moves through the Larynx, the upper end of the Trachea, and into the Trachea (windpipe) which leads directly to the lungs.

9. These passageways provide a direct connection between the outside air and some of the most Delicate Tissues in the body.

10. These passageways must filter out dust, dirt, smoke, bacteria, and a variety of other contaminants found in air.

11. The first filtering is done in the nose. The nose will do three things to the air we breathe in:

  • filter the air,
  • warm the air,
  • provide moisture (water vapor or humidity to the air)

12. As air passes through the nasal cavities it is warmed and humidified, so that air that reaches the lungs is warmed and moist.

13. The Nasal Airways are lined with Cilia and kept moist by Mucous secretions. The combination of Cilia and Mucous helps to filter out solid particles from the air and Warm and Moisten the air, which prevents damage to the delicate tissues that form the Respiratory System.

14. The moisture in the nose helps to heat and humidify the air, increasing the amount of Water Vapor the air entering the Lungs contains.

15. This helps to keep the air entering the nose from Drying out the Lungs and other parts of our Respiratory System.

16. When air enters the Respiratory System through the Mouth, much less filtering is done. It is generally better to take in air through the Nose.

17. At the top of the Trachea is the Larynx (Voice Box). Inside, and stretched across the Larynx are two highly elastic folds of tissue (Ligaments) called the Vocal cords. Air rushing through the voice box causes the vocal cords to vibrate producing sound waves.

18. From the Larynx, the Warmed, Filtered, and Moistened air passes downward into the Thoracic Cavity through the Trachea.

19. The Walls of the Trachea are made up of C-Shaped rings of tough flexible Cartilage. These rings of cartilage protect the Trachea, make it Flexible, and keep it from Collapsing or over expanding.

20. The Cells that line the trachea produce Mucus; the mucus helps to capture things still in the air (Dust and Microorganisms), and is swept out of the air passageway by tiny Cilia into the Digestion System.

21. Within the Thoracic Cavity, the Trachea divides into Two Branches, the Right and Left Bronchi. . Each Bronchus enters the Lung on its respective side. The Lungs are the Site of Gas Exchange Between the Atmosphere and the Blood. The Right Lung has Three Divisions or Lobes, and is slightly larger than the Two Lobed Left Lung. The Lungs are inside the Thoracic Cavity, bounded by the Rib Cage and Diaphragm. Lining the entire cavity and encasing the Lungs are Pleura Membranes that secrete Mucus that decreases friction from the movement of the Lungs during Breathing.

22. The further branching of the Bronchial Tubes is often called the Bronchial Tree.

23. Imagine the Trachea as the trunk of an upside down tree with extensive branches that become smaller and smaller; these smaller branches are the Bronchioles.

24. Both Bronchi and Bronchioles contain Smooth Muscle Tissue in their walls. This muscle tissue controls the Size of the Air Passage.

25. The Bronchioles continue to subdivide until they finally end in Clusters of Tiny Hollow Air sacs called Alveoli. Groups of Alveoli look like bunch of grapes. All exchange of gases occurs in the Alveoli.

26. The Alveoli consist of thin, flexible membranes that contain an extensive network of Capillaries. The Membranes separate a gas from liquid. The gas is the air we take in through our Respiratory System, and the liquid is Blood.

27. The Functional Unit of the Lungs is the Alveoli; it is here that the Circulatory and Respiratory Systems come together, for the purpose of gas exchange. All exchange of gases in the lungs occurs in the alveoli. Each Lung contains nearly 300 Million Alveoli and has a total surface area about 40 times the surface area of your skin.

5. Available position measurement techniques for endotracheal tube during ventilation

  1. Clinical Methods:


    • Chest Expansion,
    • Respiratory Mechanism,
    • Sweating, etc
  1. Measurement of O2 (Pulse Oximeter)
  2. Measurement of Blood pressure
  3. Measurement of Heart Rate
  4. Chest X-Ray
  5. Lung Volume

    6) Proposed Modern Techniques.

    Acoustic guidance system for position measurement of Endotracheal Tube (ETT). Endotracheal tube is used during intubation.

    The process of intubation:

    1. Head positioning: The correct position for the head is “sniffing the morning air”, with the neck slightly flexed and the head extended. One places a pillow under the head and neck but NOT under the shoulders. This allows a straight line of vision from the mouth to the vocal cords.

    2. The Laryngoscope is introduced into the right hand side of the mouth (it is held by the left hand). The tongue is swept to the left and the tip of the blade is advanced until a fold of skin / cartilage is visualized at twelve o’ clock. This is the epiglottis, and this sits over the glottis (the opening of the larynx) during swallowing. (Laryngoscopes are the instruments used for performing intubations. A laryngoscope consists of a blade, of varying sizes (1 to 4), which includes a fibreoptic light source, and a handle, which contains the power source for the light.)

    3. The tip of the blade is advanced to the base of the epiglottis, known as the vallecula, and the entire laryngoscope is lifted upwards and outwards. This flips the epiglottis upwards and exposes the glottis below. An opening is seen with two white vocal cords forming a triangle on each side.

    4. The tip of the endotracheal tube is advanced through the vocal cords and once the cuff has passed through, one stops advancing. The tube is secured at this level and the cuff inflated.

    5. There are two types of cuff: high pressure-low volume (which takes 2-3ml of air) and high volume-low pressure (30 – 50ml of air). The principle with both is the same: the cuff is inflated until the leak is abolished; no more, no less. Too high a cuff pressure will necrose the tracheal mucosa (by cutting off it’s circulation) and cause a tracheal stricture.

    6. The tube may be secured in a variety of ways, all that is important is that it is held tightly, and cannot slide up and down the trachea. It is preferable to secure the tube to the upper jaw (the maxilla) than to the lower one (the mandible) as this moves up and down. Ensuring that the end of endotracheal tube (ETT) is properly located with in the trachea, and that the tube is not obstructed by mucus deposition, is a major clinical concern in patient that require mechanical ventilation. A novel acoustic system was developed to allow for the continuous monitoring ETT position. A miniature sound source and two sensing microphones are placed in line between the ventilator hose and the proximal end of the ETT. Reflections of an acoustic pulse emitted in to the ETT lumen and the air way are digitally analyzed to estimate the location and degree of lumen obstruction, as well as the position of the distal end of the tube in the air way. The system estimates tube position and differentiated between proper tracheal, bronchial or esophageal intubation in all cases. These finding indicates that this miniature technology could improve the quality of care provided to the ventilated adults and infant.

    7). Conclusion:

    Obtaining data from a respiratory system greatly increases the complexity of instrumentation problem. Fortunately, however, new developments resulting in improved, smaller and effective measuring devices are continuously being announced, thereby making possible measurements and treatment various diseases that had previously been considered being impossible. New types of radiation therapy, lasers and new drugs are being researched and developed to improve the treatment and outlook of patients with lung cancer. All of this will benefit the engineers, the physician and the patient as the time goes on by adding the tools at their disposal overcoming instrumentation problems. One most important tool is use of computers. Although the computer based patient monitoring schemes are available, but the success of complicated systems is a direct function of the skills and tenacity of staff involved and that this involves a true partnership between staff with medical, nursing and scientific background.

    Prof. Prashant B. Patel

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