MIDW1014 Respiratory system lab report PDF

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Lab Manual week 11...

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2019 MIDW1014: Laboratory report

Respiratory system Learning objectives      

List the structures that make up the upper and lower respiratory system. List the components of the respiratory conduction zone Review the function of the pulmonary circulation and respiration. Explain the lung physiology involved with oxygen and carbon dioxide exchanged. Describe the role of intra and extra thoracic pressure in the movement of air in and out of the lungs Describe what a “Peak Flow Meter” measures and the implications of low and normal peak flow readings.

Introduction The process of respiration involves the movement of air into and out of the lungs in cycles of inspiration and expiration. This process is known as PULMONARY VENTILATION. Air entering the lungs passes via the upper airways past the LARYNX to the TRACHEA, then down the two main BRONCHI, secondary bronchi and BRONCHIOLES to the ALVEOLI of the lungs. Exchange of gases between air in the alveoli of the lungs and blood in the capillaries of the lungs is known as EXTERNAL RESPIRATION. Gas exchange between blood and tissue cells is known as INTERNAL RESPIRATION. Red blood cells / haemoglobin are important in transporting oxygen and carbon dioxide to and from the lungs/tissue cells. Effective pulmonary ventilation relies on differences in pressure between atmospheric air externally and alveolar air internally. This is maintained by slightly negative pressure between the VISCERAL and PARIETAL PLEURAL of the lungs. A lubricating serous fluid secreted into the intra pleural space also reduces friction during INSPIRATION and EXPIRATION. Inspiration involves contraction (active!) of the diaphragm and external intercostal muscles which increases the thoracic volume and results in an inward movement of air. The lungs are enclosed within the THORACIC CAVITY and contain a lot of ELASTIC CONNECTIVE TISSUE which allows them to RECOIL passively during expiration. The ease with which the lungs expand and recoil is known as LUNG COMPLIANCE. PULMONARY FUNCTION TESTS are often used to assess the nature and extent of lung disease as well as the patient’s response to medication. During normal breathing a relatively constant volume of air is exchanged during the respiratory cycle. This is termed the TIDAL VOLUME (TV). However, as quiet respiration continues over a period of time there is a pause, which is followed by deep inspiration. The volume of air inhaled at this point is above that inspired during normal quiet inspiration and is termed INSPIRATORY RESERVE VOLUME (IRV). Similarly, more air can be exhaled after a normal quiet expiration and is termed EXPIRATORY RESERVE VOLUME (ERV). After every expiratory cycle there is always air which remains in the lungs. This is termed RESIDUAL VOLUME (RV). The maximal amount of air that can be inspired and then expired is termed the VITAL CAPACITY (VC). All of the pulmonary volumes (except Residual Volume) can be measured using a Respirometer (Spirometer). The PEAK EXPIRATORY FLOW RATE (PEFR), which is the highest rate of flow of air (litres per minute) that can be achieved during a maximal forced expiration, can be measured simply with the Wright Peak Flow Meter.

Activity 1 Drag and drop the labels to complete the following diagrams.

UPPER RESPIRATORY SYSTEM LOWER RESPIRATORY SYSTEM Larynx Left Lung Bronchioles Ribs Nose Frontal sinus Diaphragm Clavicl e Nasal conchae Esophagu s Apex of lungs Base of lungs

Alveolar sac Alveolar duct Alveolus Smooth muscle Capillaries Respiratory bronchiole Elastic fibers

Overview of the Key steps in Respiration Label the steps

Pulmonary ventilation

Gas diffusio n

Lungs

Gas diffusio n

CO2 transport Internal Respiration

Gas diffusio n O2 transport

External Respiration

Gas diffusio n

Activity 2 Look at models of the lungs and respiratory system and identify structures and answer the following questions.

1. Describe the functions of the upper respiratory system. ................................................................................................ ................................................................................................ ................................................................................................ 2. Describe the functions of lower respiratory system. ................................................................................................ ................................................................................................ ................................................................................................ 3. Describe surfactant and its function during respiration. ................................................................................................ ................................................................................................ 4. What path does air take when flowing from the glottis to the respiratory membrane? ................................................................................................ ................................................................................................ ................................................................................................ 5. What is the anatomical difference between the bronchi and bronchioles and list their respective functions? ................................................................................................ ................................................................................................ ................................................................................................ ................................................................................................ 6. Where are the alveoli located what is their function? ................................................................................................ ................................................................................................ ................................................................................................ 7. Describe external respiration and where it takes place. ................................................................................................

................................................................................................ ................................................................................................ 8. Describe Internal respiration and where it takes place. ................................................................................................ ................................................................................................ ................................................................................................ 9. Describe the protective mechanisms within the respiratory tract. ................................................................................................ ................................................................................................ ................................................................................................

10.

List three ways carbon dioxide is transported via the blood.

1.______________________________________________ 2.______________________________________________ 3.______________________________________________

11. Discuss and understand the concepts of intrapulmonary and intrapleural pressure. ................................................................................................ ................................................................................................ 12. Which muscles are used for inhalation and which are used for exhalation? ................................................................................................ ................................................................................................ 13. What is the role of peripheral and central chemoreceptors in the control of breathing? ................................................................................................ ................................................................................................ ................................................................................................ 14. Discuss oxygen and carbon dioxide diffusion within the alveoli. ................................................................................................ ................................................................................................ 15. When blood leaves the lungs, what is its normal level of oxygen saturation? ................................................................................................ ................................................................................................ 16. What does 100% Oxygen saturation represent? ................................................................................................ ................................................................................................

Activity 3—Measuring PEFR with the Wright Peak Flow Meter The device is not considered a reliable diagnostic tool but it can give some indication of the state of the lungs and chest, and is often used by patients pre- and post-medication as an indicator of the effectiveness of the medication. The Peak Expiratory Flow Rate (PEFR) during a forced expiration is the number of litres which can be blown out in one minute, if the subject could maintain the measured rate for the whole of a minute, not just a fraction of a second. All students will perform this task individually. 1. Take a new disposable mouth piece and write your name on it. Attach that disposable mouth piece to the Peak Flow meter and zero the meter. 2. After one deep inspiration blow as hard and as rapidly as possible, to provide one forced expiration. Return to normal breathing for at least 60 seconds. You may remove the disposable mouth piece, allow someone else to use the meter, and then use it again yourself with your mouthpiece re-inserted. 3. Measure your PEFR nine times, with a period of normal breathing between each recording. 4. Write your nine individual PEFR readings in your log. Also note the highest and lowest PEFR readings, the mean (average) PEFR, and the expected PEFR (using the chart provided). Now answer the following questions related to the PEFR activity.

1.

What can you say about the reproducibility of your measure of PEFR? ................................................................................................ ................................................................................................ ................................................................................................

2. Respiratory physicians require a patient to repeat a lung function test (such as PEFR) at least three times. Why? ................................................................................................ ................................................................................................ ................................................................................................

3. Generally why might you expect there to be differences between male and female subjects in PEFR? ................................................................................................ ................................................................................................ ................................................................................................ 4. Why would you encourage an anxious person to breathe more deeply? ................................................................................................ ................................................................................................

5. Define the anatomical term ‘dead space’ .................................................................................................. .................................................................................................. ..................................................................................................

6. Define for the following medical terms: Eupnoea, Apnoea, Bradypnoea, Tachypnoea, Dyspnoea.

.................................................................................................. .................................................................................................. .................................................................................................. .................................................................................................. .................................................................................................. .................................................................................................. ..................................................................................................

Activity 4—Measuring FEV1: Spirometry using the Vitalograph The Vitalograph Spirometer measures parameters which can be determined from forced and slow expiratory manoeuvres. It not only measures lung volumes, but the rate at which air is moved from the lung. In diseases in which the airways are narrowed the rate parameters are of more clinical value than most other measures.

FEV1 greater 80% of predicted

= normal

FEV1 60% to 79% of predicted

= Mild obstruction

FEV1 40% to 59% of predicted

= Moderate obstruction

FEV1 less than 40% of predicted

= Severe obstruction

1. What does FEV1 stand for and what is it used for? .............................................................................................. ..............................................................................................

.................................................................................................. Activity 5—Measuring Pulmonary parameters: Spirometry using the Spirotrac IV flowhead & computer Select one of the students from your group to be the subject. Use the same subject for all the experiments. It is important that the subject does not have chronic lung problems or had a recent episode of respiratory infection (e.g. cold or influenza). Estimate of Residual Volume (RV) Residual volume is the amount of air that remains in your lungs even after a maximum exhalation – it is not simple to measure. Your estimated RV in litres is required for this spirometry exercise. For females RV = (2.63 × height) – (0.02 × weight) - 1.78 litres (Note: height = height in metres, e.g. 1.76 m; weight = weight in kg, e.g. 72 kg)

Setting up Spirotrac Read the displayed instructions for using Spirotrac.

** Use your phone camera to photograph the righthand graph after returning to tidal breathing. It looks like Fig 1 below.

Fig 1 Normal spirometer trace

Flow rate - volume graph After a full inhalation, a normal Flow rate - Volume loop begins on the Xaxis (Volume axis): at the start of the test both flow rate and volume are equal to zero. As you forcefully exhale, the curve rapidly mounts to a peak: Peak (Expiratory) Flow (see Fig 2B). After the PEF the curve descends (= the flow decreases) as more air is expired. A normal, non-pathological F/V loop will descend in a straight or a convex line from top (PEF) to bottom. At the end of exhalation the graph’s position indicates the volume of air that has been exhaled (FVC). The forced inspiration that follows the forced expiration has roughly the same morphology, but the PIF (Peak Inspiratory Flow) is not as high as PEF. The small ellipse on the x axis, when measured left to right, indicates the (resting) tidal volume.

Volume – Time graph Another way of representing the spirometry test is through the volumetime graph (See Fig 2A). The start is at coordinates 0-0 (at time 0, flow is 0). In a forced blow, most air is expired at the beginning, when the patient empties the large airways, and the graph rapidly rises. About 80% of total volume is expired in the first second (FEV1). As the lungs are emptied, the rise in expired volume gets lower and lower to end in a horizontal level.

Fig 2: A normal volume-time loop (left); A normal flow rate-volume loop (right)

Spirometry values are compared with predicted values. A FEV1/FVC ratio A ratio of...