Spirometry : To record static and dynamic lung volumes and capacities

Physiology practical Spirometry. Aim is to record the static and dynamic lung volumes. Video description of the spirometry also included

1. Spirometry: Determination of Lung volume and capacities By: Dr. Ravi Dutt (MBBS, MD) * With video description of Spirometer

2. AIM To measure the static lung volumes using spirometer To measure the Dynamic lung volumes using spirometer

3. Apparatus Required Recording Spirometer Nose clips Potassium permanganate solution/Spirit to clean mouth piece Graph paper

4. Recording Spirometer The recording spirometer, which is electrically driven, is used to provide a graphic record (called spirogram) of various lung volumes and capacities. Pulley chain Outer cylinder Pen marker attached to counter weight Kymograph Bi Directional Valve to connect mouthpiece with atmospheric air/ spirometer Control panel for kymograph O2 inlet Water outlet Corrugated rubber tube with mouthpiece 2 corrugated rubber tube one for inspiration ,other for expiration each with unidirectional valve

5. Schematic diagram of Spirometer

6. Parts of Spirometer Double-walled cylindrical chamber. It contains water between its two walls (as in vitalograph or simple spirometer) to maintain an airtight seal. Bell: A 9-liter lightweight metal “gas bell” dips into the water from above and floats in it. A chain attached to the top of the bell passes over a frictionless pulley and carries a counter-weight and a pen writer. As the volume of air increases and decreases, the writing point moves down and up on the surface of the paper that passes under it. This provides a continuous record of the displacement of air in the bell with each inspiration and expiration.

7. Soda lime absorber . It is fitted within the spirometer and removes (absorbs) CO2 from the expired air so that one can continue to breathe into and out of the spirometer. The kymograph . There is an on/off switch and a pilot lamp on the front of the apparatus. There is a control panel on the front of the apparatus from where the speed of the kymograph can be set. i . 60 mm/ min ( 1mm/sec) speed is for normal recordings ii. 1200 mm/ min (20 mm/sec) is for recording timed vital capacity

8. The chart paper : The calibration along Y-axis is for volume. The paper has horizontal lines over the full length of paper, each line is separated by a distance equivalent to 100 ml as shown in the picture. A slot on the upper and lower part of the kymograph drum allows exit of recorded paper. Breathing assembly. The breathing assembly has a mouthpiece which is connected to the spirometer, via a Y piece, by 2 rubber-canvas corrugated tubes, one carrying a unidirectional valve for inspiring air from the bell and the other carries a unidirectional valve for expiring air into the atmosphere. The third component of the assembly is a free-breathing valve which has a directional tap. The tap can be turned to permit a person either to breathe room air, or air from the spirometer bell .

9. Also provided are: Inlet for filling the gas bell with oxygen or any other gas. A tap for draining water out of the apparatus. A chart reverse knob can rewind the recorded chart paper by turning the knob clockwise. A nose-clip is provided for closing the nostrils during recording.

10. Video description of spirometry

11. Procedure: Recording of static lung Volumes Familiarizing subject with the spirometer Fill 3/4th of the space between the two walls of the chamber with water. Dip the gas bell from above into the water. Connect the gas valve to the atmosphere and wash and fill the gas bell with fresh room air by slowly raising and lowering it 3–4 times. Seat the subject facing the spirometer and instruct her/him about the procedures that will be carried out. Insert the mouthpiece between the teeth and lips and apply nose clip on the nostrils. Tell the subject to breathe through the mouth for about a minute to familiarize him/her with mouth breathing.

12. After famil iarizing the subject with the apparatus , start taking the readings as described below Connect the subject to the spirometer and allow her/him to breathe quietly for a short time. Then start the kymograph at the speed of 60 mm/ min and record the excursions of the pen writer for about a minute. Note that the upstrokes are inspirations and down strokes expirations. This record of tidal breathing will be used for calculating the rate of respiration, tidal volume (TV) and minute ventilation (minute volume; MV). TV- Volume of air breathed in or out during quiet respiration. Normal- 500 ml Minute ventilation: Volume of air inspired or expired out of the lungs in one minute. MV = TV x RR = 500 x 12= 6L/min. Upstroke- inspiration Downstroke- expiration TV

13. Recording of Inspiratory reserve volume(IRV) and inspiratory capacity(IC) IRV: It is the maximal volume of air which can be inspired after completing a normal tidal inspiration i.e. inspired from the end in spiratory position . Normal: 2000-3000 ml IC: It is the maximal volume of air which can be inspired after completing tidal ex piration i.e. from the end ex piratory position . IC= TV+ IRV Normal: 2500-3500 ml To record IRV, ask the subject to breathe in as deeply as possible after a quiet inspiration. IRV + TV will give IC. Record a few tidal breaths afterwards. IC

14. Recording of Expiratory reserve volume(ERV) Expiratory Reserve Volume (ERV). It is the extra amount of air that can be expelled (expired) by forceful expiration from the spontaneous end-expiratory point, i.e. over and above the normal tidal expiration. Normal: 750-1100 ml. To record ERV, ask the subject to breathe out as forcefully as possible after a quiet expiration.

15. Recording of Vital capacity (VC) After few tidal breaths, subject is asked to inspire as deeply and as fully as possible to fill the lungs, then subject is asked to expel all the air that he can with maximum effort into the spirometer.

16. THE LUNG VOLUMES AND CAPACITIES THAT CANNOT BE MEASURED ON A SPIROMETER Residual Volume (RV): It is the amount of air that remains behind in the lungs after a maximum voluntary expiration. It amounts to 1300 ml. The lungs cannot be emptied out completely of air even with maximum effort because as the pressure outside small air passages increases (i.e. the high intrathoracic pressure due to maximum expiratory effort) they are compressed and thus block the flow of air out of the lungs. So, The lung capacities that have RV as their component , cannot be measured on a spirometer. These include Total lung capacity (TLC): It is the volume of air that is present in the lungs at the end of a deepest possible inspiration. It is a measure of VC + RV , and amounts to 6Litres. F unctional residual capacity (FRC): This is the amount of air remaining in the lungs at the end of a normal (quiet) expiration. FRC= ERV + RV It amounts to about 2300-2500ml .

17. RECORDING OF DYNAMIC LUNG VOLUMES AND CAPACITIES Maximum Voluntary Ventilation (Maximum ventilation volume, MVV). It is the amount of air which can be moved into or out of the lungs with maximum effort during one minute. Formerly called Maximum Breathing Capacity (MBC ), the MVV amounts to 140–180 liters/min. This means that pulmonary ventilation of 6–8 l/min can be increased by 20 –25 times with maximum effort, though for short periods Procedure: After taking few tidal breaths, the subject is asked to breath in and out as deep and as fast as possible for 15 seconds. Count the number of Either inspiratory or expiratory peaks in 15 seconds. Let it be N. MVV (L/min) = N x 4 x Volume VOLUME

18. Parameters derived from MVV Breathing reserve(BR) or Pulmonary Reserve (PR) is the maximum amount of air above the pulmonary ventilation which can be breathed in and out of lungs in one minute. Breathing Reserve (BR) = MVV – PV Lets take ,MVV = 100 L/min, and Pulmonary ventilation(TV x RR) = 10L/min BR= 100 – 10 = 90 liters . This means that breathing (ventilation) can be increased by 90 liters, i.e. from 8–10 liters/min to 100 litres /min or more. This is a large reserve for ventilation. The breathing reserve percent is also called dyspnea index . Breathing reserve % or Dyspnea Index (DI) = (MVV - PV /MVV) × 100 Normal DI is greater than 60-70% Dyspnea is present when this index falls to 60–70% which is called the dyspnea point .

19. Timed vital capacity or Forced Expiratory Volume (FEV) When the expired volume of vital capacity is timed, its is known as timed vital capacity, which can be timed for 1st, 2 nd and 3 rd seconds and represented as FEV1, FEV2 and FEV3 respectively. To record Timed vital capacity (TVC) andFEV1, quickly change the kymograph speed to 1200 mm/min , and take 2-3 tidal volumes. Then A sk the subject to first take a deep breath and then expel the air from the lungs as forcefully and as quickly as possible (as for VC). Take 3 readings at intervals of about 2 minutes.

20. Calculation of FEV1 1 st sec 2 nd sec 3 rd sec 20 mm Drum speed = 1200 mm/min or 20mm/sec For calculating FEV1, First of all Mark Zero point (or time): The point where inspiration ends and expiration begins. Since the speed of kymograph drum is 1200 mm/min i.e. 20 mm/sec, move 20 mm (=1sec) on X- axis from zero point, drop a perpendicular line from here on the expiratory tracing, this will give the volume of air expired in the first second of exhalation(FEV1). Similarly, FEV2 and FEV3 will be determined by moving 40 mm and 60 mm respectively to the right of Zero Time. Normal values: FEV1 is about 80% of FVC FEV2 is about 93% of FVC FEV3 is about 97% of FVC 20 mm VOLUME TIME

21. Other parameters derived from TVC spirogram In addition to FVC and FEV1, the average expiratory flow rate during the middle 50% of FVC, also called “maximal mid-expiratory flow rate” (MMEFR; or FEF 25–50%) can also be calculated. This is also called Mid- expiratory Time (MET). Divide the expiratory tracing in to 4 equal parts and draw two perpendicular lines as described below A horizontal line drawn from 25% (gives the time) and a vertical line from the 75% mark (gives volume) will denote FEF 25–75%.This indicates the patency of smaller airways. Normal range = Males: 1.5–4.5 l/sec. Females: 1.3–3.0 l/sec. These value are increased in obstructive lung disorders.

22. Precautions Subject should not face the recording spirometer during recording. All lung volume and capacities are measured from the end that is expiratory position. Look for the color of the soda lime ( change of color from white to pink indicates that it is near point of exhaustion) Make sure that there is no leak (of air) from the vitalograph and spirometer.

23. References Ghai’s Text book of Practical Physiology (9 th edition) Revised & edited by Dr. V.P. Varshney and Dr. Mona Bedi Essentials of MD/DNB Physiology Practical Examination by Dr. A.K. Jain Comprehensive Text book of Physiology by Dr. G.K.Pal

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