Effect of forced breathing on ventilatory functions of the lung.LN Joshi, VD Joshi
Department of Physiology, L.T.M. Medical College, Sion, Mumbai.
Ventilatory functions were studied in 36 male and 35 female subjects (mean age 18.5 years), who underwent six weeks course in forced breathing. Ventilatory functions were studied in the form of Forced Vital Capacity (FVC), Forced Expiratory Volume at the end of one second as % of FVC (FEV1%), Maximum Voluntary Ventilation (MVV), Peak expiratory flow rate (PEFR) and Breath Holding Time. Some of these ventilatory functions were found to be increased after a course of forced breathing.
Keywords: Adult, Breathing Exercises, Female, Human, Male, Pulmonary Ventilation, physiology,Respiratory Function Tests, Sex Factors, Vital Capacity,
Forced breathing is, to breath deeply and slowly for certain duration of time voluntarily, overcoming the autonomic or involuntary breathing drive. ‘Pranayam’ is a kind of voluntary regulated forced breathing characterized by timed breath holding (Kumbhak) either at the end of inspiratory phase or at the end of expiratory phase. There are different kinds of ‘pranayams’ varying in duration of the phases in breathing cycle and in other details like the nostrils used and ‘Bandhas’ employed. Our earlier study showed that short term practice of one kind of such pranayamic breathing improve many of the ventilatory functions of the lung and also prolonged breath holding time.
The present study was undertaken to ascertain whether practice of forced breathing involving only a phase of deep inhalation and forceful exhalation without a phase of breath holding as practiced in ‘Pranayam’ also prolongs breath holding time and improves ventilatory functions of the lung.
36 healthy male (Nonsmokers) and 33 healthy female medical student (mean age 18.5 years) were studied for ventilatory lung functions before and after the six weeks course of forced breathing. The subjects did not undertake any other physical exercise programme nor any type of yogic exercise practice during the study. Each subject acted as his or her own control.
The practice of forced breathing each time lasted for 10 minutes and was practiced once a day for six days in a week for a period of six weeks. Subjects were instructed to sit erect and to breath through both nostrils with eyes closed concentrating on breathing. A prerecorded audiotape was played to synchronise the rate of breathing of all the subjects. The subjects were asked to take maximal sustained inspiration lasting for five seconds, followed by maximum sustained expiration, which also lasted for five seconds. Thus breathing rate was controlled to 6 breaths / min during each practice.
Study of ventilatory functions was carried out on a computerized pulmonary testing machine (Jaeggar - Flow mate). Each subject was given three trials and the best of three was taken for study. A stopwatch recorded breath-holding time.
Following ventilatory functions were studied
1. FVC (lit) - Forced Vital Capacity
2. FEV1% - Forced Expiratory Volume at the end of one second as of % of FVC.
3. MVV (lit/min) - Maximum Voluntary Ventilation
4. PEFR (lit/sec) - Peak Expiratory Flow Rate
5. Breath holding time (BHT) in Seconds at
a. TLC - Total lung Capacity
b. RV - Residual Volume
Results were analysed statistically by paired student ‘t’ test.
[Table - 1] shows spirographic values and breath holding time at TLC and RV in males before and after a course of forced breathing. There is no significant change in FVC, FEV1% and MVV values, but PEFR is significantly increased. Breath holding time at TLC and RV has increased significantly.
[Table - 2] shows spirographic values and breath holding time at TLC and RV in females. A significant increase in FEV1% and MVV was observed. Breath holding time at TLC and RV has increased significantly. No significant increase was observed in PEFR.
The absolute volume of Forced Vital Capacity (FVC) is important because it is an index of the state of elastic properties of the respiratory apparatus, whereas the rate at which FEV1 is expelled from the lungs is predominantly a reflection of the flow resistive properties. Most laboratories assess flow resistance by an analysis of the volume of air expired in particular time, the most frequent one being that expired in the first second (FEV1%). FEV1% predominantly reflects resistance to air-flow in airways that are greater than 2 mm in diameter.
The Peak Expiratory Flow Rate (PEFR) is generally considered as a sensitive indicator of changes in elastic recoil pressure and / or of the resistance of small airways. PEFR is subject to wide variability and is effort dependent.
Maximum Voluntary Ventilation (MVV) is an over all test of the respiratory apparatus measuring the status of respiratory muscles, the mechanical properties of lungs and chest and also the flow resistive properties of the system. MVV also is an effort dependent test and subject to wide variability.
During practice of forced breathing lungs and chest were inflated and deflated to the fullest possible extent and muscles worked to their maximum capacity.
A significant increase in FEV1% and MVV in females [Table - 2] was observed. This could be due to strengthening of respiratory muscles and improvement in elastic properties of the lungs and chest incidental to regular practice of forced breathing. Similar ventilatory training even in elderly subjects and subjects with chronic obstructive pulmonary diseases have been shown to improve these ventilatory functions of the lungs,. Additionally inflation near to total lung capacity is a major physiological stimulus for the release of surfactant thus increasing compliance of the lungs.
These functions did not show significant increase in males, but a trend toward an increase in these functions was observed [Table - 1].
The Peak Expiratory Flow Rate (PEFR) is significantly increased in males but not in females. This discrepancy in the result could be due to poor motivation and inadequate efforts by the subjects, and requires reconfirmation by further study on a larger sample.
Breath holding time (BHT) at TLC and RV has significantly increased both in males and females [Table - 1] & [Table - 2]. It shows that even when the specific breath holding manoeuvre was not performed during daily practice of forced breathing, it prolonged the BHT. Prolonged BHT indicates either decreased responsiveness of the respiratory centre to CO2 or of some unconfirmed chemoreceptors as reported in the subjects who regularly practice breath holding manoeuvre. Such breath holding manoeuvres are practiced by Hathyogies, deep sea-divers and scuba divers,,. Prolonged breath holding time could also be due to increased endurance of respiratory muscles, delaying their onset of fatigue.
It is suggested that the practice of forced breathing without breath holding phase, also can strengthen the respiratory muscles and increase the elastic properties of lungs and chest and thereby improve some of the ventilatory functions of the lungs.
[Table - 1], [Table - 2]