Practical Workbook of Human Physiology K Sri Nageswari, Rajeev Sharma
Chapter Notes

Save Clear

Respiratory System1

The respiratory system of the subject should ideally be examined with the subject comfortably resting on a bed, sitting at an angle of 45º. The general physical examination for the vital signs should also be carried out at the same time viz.: temperature, pulse, blood pressure, pallor, edema, cyanosis, jugular venous pressure, and lymphadenopathy. Respiratory examination should be done under four headings:
  • Inspection
  • Palpation
  • Percussion
  • Auscultation
The subject is asked to lie supine on the bed, bare-chested. The examiner stands at the foot end of the bed and the rate, rhythm, type of respiration: thoracic/abdominal/thoracoabdominal and shape of the chest is noted.
Rate: Normal rate is 14 to 16 breaths/min. Rate is more in females, childhood and infancy and less in males.
Rhythm: The abnormalities in rhythm like Cheyne Stokes breathing are noted.
Shape of the chest: Normal shape of the chest is bilaterally symmetrical.
  • Approximating the tips of the thumbs in the midline and keeping the fingertips in fixed position on lower rib cage, symmetry of expansion of the chest is assessed.
  • Position of the trachea is noted. The trachea is felt in the suprasternal notch, by insinuating fingers on both sides of it and its placement in relation to the suprasternal notch is noted.2
  • Vocal fremitus: With the ulnar border of hand placed on chest of subject along intercostal space, subject is asked to repetitively utter some word. The intensity of vibrations in the corresponding area on the two sides of the chest in each intercostal space is assessed, which should be equal.
  • Position of apex beat: It is felt in the left 5th intercostal space, 1 cm internal to the midclavicular line.
  • Percussion of different areas of chest is done to note down the degree of resonance
  • The middle finger of left hand is placed on the part to be percussed and struck with the tip of the middle finger of right hand
  • Percussion note is compared on the two corresponding areas of the chest always
  • Percussion should be carried out in three to four areas on anterior chest wall, in the axilla and four areas on the back, comparing left with the right
  • The intercostal area where hepatic dullness appears is noted
  • Any additional site of dullness is noted.
For the auscultation the patient should be in sitting position. He should breathe deeply and regularly with the mouth open and face turned to other side.
  • Breath sounds and their character
  • Character of vocal resonance
  • Presence of added sounds.
Breath sounds: Note whether the breath sounds are vesicular or bronchial.
  • Vesicular breath sounds: These are produced by passage of air in and out of normal lung tissue and heard all over the chest in normal condition. Inspiratory sounds are fairly intense and heard for the duration twice that of the duration of expiration. The quality of the sounds is rustling and low pitched. There is no distinct pause between the end of inspiration and start of expiration.
  • Bronchial breath sounds: Normally produced by passage of air through trachea, larynx and large bronchi when the lung tissue between these airways and chest wall is airless. The sound resembles that obtained by listening over the trachea. The expiratory sounds are generally more intense than inspiratory sounds and extend through greater part of the expiratory phase. Inspiratory sounds are moderately intense and do not extend through out the inspiratory phase and there is a pause between the end of inspiration and start of expiration. The quality of sounds is harsh, high pitched.
Vocal resonance: It is the resonance of sounds in the chest made by the voice. Intensity and character of vocal resonance on each side of the chest over different areas of the lung is noted. The patient is asked to repeat the word one-one or ninety-nine while auscultation is being done.
Adventitious/added sounds: They can arise from either lung or pleura.3
Lung Sounds
  • Dry sounds: Known as rhonchi. They are continuous sounds produced by partialobstruction of respiratory passages. For example bronchitis, bronchial asthma or bronchospasm.
  • Moist sounds: Known as rales (coarse crackles) or crepitations (fine crackles). They are discontinuous crackling sounds produced in the alveoli, bronchioles, and bronchi. They indicate the presence of fluid secretion in the air sacs or tubes.
Pleural Sounds
The common adventitious sound arising in the pleural cavity is a friction sound or pleural rub characteristic of pleuritic pain (pleurisy).
  1. Enumerate the conditions in which
    • Trachea deviates from the midline
    • Vocal resonance increases
    • Vocal resonance decreases
    • Rhonchi are heard
    • Crepitations are heard
    • Bronchial breathing is heard.
  2. Differentiate between vocal resonance and vocal fremitus.
  3. Define Cheyne Stokes breathing. Name the physiological conditions resulting in Cheyne Stokes breathing.
Equipment Description
Simple Spirometer/Vitalograph: The simple spirometer/vitalograph consists of an outer container filled with water in which 6-liter capacity gas bell floats. The float is attached to a chain, which passes over a calibrated pulley bearing a spring-loaded indicator needle; the needle moves with the pulley. The gas bell is counterpoised and has very little inertia and friction. The inlet tube is corrugated rubber canvas bearing a mouthpiece and is attached to a pipe fitted at the bottom of the outer water container.
  • The subject is explained about the procedure
  • The gas bell is brought to the lowest position so that pointer needle indicates zero
  • The patient is asked to breathe normally for a few minutes. Then he is asked to inspire as deeply and fully as possible with nostrils closed with his thumb and fingers and to expire with maximum effort into the mouthpiece held tightly between the lips
  • The gas bell moves up and the pointer on the pulley indicates the volume of expired air
  • This indicates vital capacity, which should be noted in the sitting and standing position, in order to study the effect of posture
  • Three readings are noted at an interval of 5 minutes
  • Each of the volumes is noted.
  1. Define vital capacity. Give its normal values in males and females.
  2. What are the physiological factors affecting vital capacity?
Equipment Description
Benedict Roth Spirometer : It consists of a bell of 6-liter capacity, four speed recording unit, a kymograph, gearbox, and three stop cocks-one to serve as a water outlet and other two for oxygen and any other gas. The two-way stopcock is carried in an adjustable arm and fitted with mouthpiece via corrugated rubber tubing (Fig. 1, Plate 1).
  • The bell is filled with atmospheric air by lifting it and allowing the air to be drawn in. To ensure that the spirometer is leak proof, the bell is slightly pressed while keeping the breathing tube closed
  • After cleaning the mouthpiece with antiseptic solution, it is placed in the mouth of the subject. Its edge plate is inserted between gums and teeth and the horizontal plates are clenched with teeth
  • The nostrils are closed with thumb and fingers and breathing is continued into atmosphere, till it becomes normal
  • After turning the valve and connecting the mouthpiece to spirometer, the subject is asked to breathe normally for 30 seconds. The drum speed is kept at 2 mm per second and the record for the tidal volume is taken
  • To record inspiratory reserve volume, the subject is asked to breathe in maximally after a normal tidal inspiration, and to exhale maximally after normal tidal expiration to note expiratory reserve volume
  • To record vital capacity, he/she is instructed to exhale maximally after maximal inspiration
  • To record FEV1, the subject exhales as forcefully and rapidly as possible after maximal inspiration, with the drum adjusted at a higher speed
zoom view
Fig. 1: Benedict Roth apparatus
  1. Enumerate and define all lung volumes and capacities (static and dynamic) and give their normal values in adults.
  2. From the sample record obtained, calculate the following:
    1. Tidal volume
    2. Inspiratory reserve volume
    3. Expiratory reserve volume
    4. Vital capacity
    5. Forced expiratory volume in one second (FEV1)
  3. Give some examples of Restrictive and Obstructive diseases.
  4. What is Maximum Voluntary Ventilation?
Stethograph, Marey's tambour, Stopwatch, Kymograph and time marker or Physiograph
Stethograph : It consists of corrugated rubber tubing, which has a side tube, and a chain attached. The side tube is connected to Marey's tambour, which has a lever with a pointer that records the movement. Whenever the corrugated rubber tube is stretched due to respiratory movements, there is an increase in the length of the tube and the mean radius remaining constant, an increase in volume of the air inside the tube is associated with a fall in pressure. This results in depression of the diaphragm of the Marey's tambour and its lever records a down stroke with each inspiration. The opposite occurs with expiratory phase.
  • The corrugated rubber tube is tied around the subject's chest, in the fourth intercostal space
  • The connecting pressure tube is joined to Marey's tambour, which is mounted along with time marker on the same stand and the two levers made to touch the kymograph drum in the same vertical line. Normal respiratory movements are recorded keeping the speed of the kymograph at 2.5 mm/sec
  • The effect of following variables on respiratory movements is observed
    • Cough
    • Speech
    • Deglutition
    • Hyperventilation
    • Breath holding
    • Exercise
Attach your recording and comment on your observations.
  1. Do not allow the subject to see the recordings during the experiment
  2. Subject should be allowed to hyperventilate for a short period only
  1. What is the principle of Stethography?
  2. Define Breaking Point. Enumerate the factors which delay the breaking point.
  3. Comment upon your observations on respiratory movements following Hyperventilation.
Equipment Description (Fig. 2, Plate 2)
Medspiror : Medspiror is a fiberglass cabinet, which houses the electronics, power supplies and operator controls. It is used with electromechanical pneumotach supplied with the instrument. The built in 40 column printer permits one or more printouts containing patient information, calculated, predicted and percentage predicted values of all the 14 parameters, clinical interpretation of the results and two plots viz. flow-volume and volume-time.
The Medspiror may be used to test the following parameters:
  • FVC: Forced vital capacity
  • FEV0.5: Forced expiratory volume in half second
  • FEV1.0: Forced expiratory volume in one second
  • FEV3.0: Forced expiratory volume in three seconds
  • PEFR: Peak expiratory flow rate
  • FEF25-75: Mean forced expiratory flow during the middle half of the FVC.
  • FEF2-12: Mean forced expiratory flow rate between 0.2 and 1.2 liters of volume change.
  • FEF 25 percent: Forced expiratory flow after 25 percent of the FVC has been expired.
  • FEF 50 percent: Forced expiratory flow after 50 percent of the FVC has been expired
    zoom view
    Fig. 2: Medspiror
  • FEF 75 percent: Forced expiratory flow after 75 percent of the FVC has been expired
  • MVV: Maximal voluntary ventilation.
To record the above parameters Medspiror should be calibrated and the subject's data should be fed in.
To record FVC
  • A nose clip is attached to the subject and a clean mouthpiece is attached to the breathing tube
  • Maximum inspiration is performed
  • Mouthpiece is placed firmly into the mouth
  • Maximum expiration is performed
  • Mouthpiece is removed
  • Immediately before the subject begins the forced expiratory phase of the manoeuvre, the E key should be pressed
To record MVV
  • Enter M to prepare for an MVV manoeuvre
  • Enter 2 digits to establish the number of seconds the MVV test is to be run (between 1030 seconds)
  • A nose clip is attached to the subject, the mouthpiece is placed into the subject's mouth and the subject is instructed to breathe normally
  • With display reading 00 and the subject settled, he is asked to breathe as rapidly and deeply as possible
  • After the subject has begun the manoeuvre (one or two breaths), the E key is pushed, the display shows the number of seconds entered earlier
  • The display counts down (in seconds) to 0 simultaneously as the subject performs the MVV test
  1. Name the conditions that affect the Peak Expiratory Flow Rate.
  2. Explain MMFR.
  3. What is the clinical significance of Timed Vital Capacity?
Equipments: Benedict Roth apparatus, Oxygen cylinder
Basal metabolic rate refers to the minimum rate of energy expenditure under basal conditions that is compatible with life. It can be determined clinically by measuring the O2 consumption of the subject in a resting state and is expressed as kcal/hour/m2 body surface area (BSA).
Prerequisites for Measuring Basal Metabolic Rate
  • The subject should be kept fasting for 12-14 hours before the start of the test. This ensures that the subject is in post- absorptive state and the SDA of food does not affect BMR.
  • He/she should be in a state of complete physical and mental rest at the time of the test. Physical rest is ensured by making the subject lie down on a comfortable couch and mental rest is ensured by providing him a relaxed, quiet atmosphere free from noise. Room temperature is adjusted in a comfortable range. The procedure is explained to the subject to clear any apprehensions regarding the experimental procedure.
  • The subject's age, sex, height and weight are noted
  • Barometric pressure and the temperature of the spirometer are measured
  • The subject is made to relax in the recumbent position for about half an hour before the commencement of the test
  • The calibrated spirometer chart is pasted on the drum of the spirometer and the inverted bell of the spirometer is filled with 100 percent O2
  • The subject is asked to breathe in and out of the spirometer through the mouthpiece with nostrils clipped
  • The subject becomes familiarised with the breathing technique in few seconds after which the respiratory excursions are recorded on the moving drum of the Benedict Roth apparatus for six minutes
  • As the O2 in the bell gets consumed during respiration, the baseline of the respiratory tracing moves upwards
  • The difference between the starting point and the end point of the baseline indicates the O2 consumed during six minutes
  • The O2 consumption in one hour is derived from this value
  • Caloric equivalents for 1 liter O2 (kcal/hour) are noted down after correction is done for temperature and barometric pressure from Mckesson chart11
  • The body surface area (BSA) of the subject is calculated by using the Dubois body surface chart or Dubois formula
  • This gives O2 consumption in kcal/hour/sq.m. body surface area i.e. Basal Metabolic Rate (BMR)
  • Predicted BMR is obtained from the table of the Mckesson chart as per age and sex of the subject
  • The percentage deviation of the obtained BMR from predicted BMR is calculated. A deviation of ±15 percent is considered within normal limits.
Normal Values of BMR in Adults
Males : 40 kcal/hour/m2 body surface area.
Females : 37 kcal/hour/m2 body surface area.
  1. Enumerate the factors that affect Basal Metabolic Rate (BMR).
The cardiopulmonary resuscitation is an emergency life saving procedure for a person presenting with cardio-respiratory arrest.
Cardio-respiratory arrest is defined as the abrupt failure of the heart or respiration or both to maintain adequate cerebral blood flow.
It can be divided under two headings:
  1. Artificial Respiration
  2. Cardiac Massage
Artificial Respiration
Mouth to mouth breathing:
  • The subject is positioned flat on the back and the neck is extended
  • The patency of his airways is checked and any obstructions if present are cleared
  • The nostrils are closed and his mouth is opened
  • A deep inspiration is taken by the examiner and the examiner's mouth is applied to the subject's mouth and forceful exhalation is done into the subject's mouth. The expansion of his chest is noted
  • A rate of 10-12 breaths per minute is maintained.
Cardiac Massage
  • The palm of one hand is placed at the junction of upper 2/3 and lower 1/3 of the sternum and the heel of the other hand over the first
  • Keeping the elbows straight, the pressure is exerted vertically downwards on to the sternum and the sternum is compressed by about 4-5 cm in each compression
  • Compressions should be maintained at a rate of 70-80 per minute
If resuscitation is being done by one person only then a ratio of 15 compressions to two breaths should be maintained and if resuscitation is done by two persons then a ratio of 5 compressions to one breath should be maintained.
  1. Mention the procedure for carrying out, cardiac and respiratory resuscitation simultaneously
  2. Name the different methods of artificial respiration.