Dimensional statistics for estimation of lung volumes.

The theory of dimension has been widely used in physics to check the validity of formulae. This theory has not been used more frequently in statistics as compared to physics for development of various prediction formulae/equations in applied physiology. An attempt has, therefore, been made in the present investigation to evolve formulae for estimation of lung volumes from cubic function of height based on dimensional considerations in boys and girls 8-13 and 16-21 years of age.

Suggested predictive indices for high altitude pulmonary oedema.

A study was conducted to evaluate the responses of chemoreceptors and pulmonary vascular bed to hypoxia, on two groups of soldiers exposed to similar altitudes, one group which did not suffer from high altitude (HA) maladies (Gp A) and the other when exposed to similar altitudes suffered from HA maladies (Gp B high altitude pulmonary edema--susceptible group (HAPE-S). Aim of this study was to find out whether these two tests could be used as a screening test for soldiers and sojourners proceeding to HA. Chemoreceptor responses were evaluated by hypoxic ventilatory response (HVR) test and the pulmonary vascular responses were studied by recording pulmonary artery pressure (PAP) changes under simulated hypoxia by breathing hypoxic gas mixtures (HGM) in both the groups. It was observed that HAPE-S subjects showed a reduced HVR response and an increase in PAP (systolic, diastolic, and mean). While Gp A subjects showed an increase in ventilation of 11.39 +/- 3.36 L, the same in Gp B subjects was 3.51 +/- 2.65 L. Thus, the comparison of increase in ventilation following HVR test between the two groups was highly significant. Under hypoxic gas mixture (HGM) breathing, systolic pressure of 28.2 +/- 6.9 and 52.6 +/- 11.0 mm Hg; diastolic pressure of 11.4 +/- 3.8 and 23.6 +/- 5.8 mm Hg and mean pressure of 17.6 +/- 4.3 and 35.0 +/- 7.4 mm Hg were recorded in pulmonary arteries in Gp A and Gp B subjects, respectively. Gp B subjects showed a highly significant increase in all the three pulmonary pressures under HGM breathing.

Clinical observations on tropical men during their sojourn over the Arctic region.

In the present study, besides a detailed clinical evaluation, roentgenographic changes in cardio-respiratory system in Indian soldiers (IS) during their 60 days stay at the arctic have been observed. These results have been compared with the responses at Delhi (before cold acclimatisation) and on return to Delhi (deacclimatisation). An attempt has also been made to compare the same physiological variables with those of Russian Migrants (RM) and Russian Natives (RN) in the arctic region to review significant differences if any. Heart Rate (HR) did not show much change; there was a tendency to increase in both systolic and diastolic blood pressure; and Kerdo's index inclined towards increased sympathetic activity in IS. X-ray chest (PA View) did not show any appreciable change in the lungs in the three groups. One subject amongst IS showed cardiac enlargement and RN subjects showed prominence of pulmonary artery and pulmonary vascular markings. All these physiological changes aim at increasing the cardiac output to overcome the ill effects of cold. Pneumopathy, a clinical condition of increased pulmonary haemodynamics could have resulted in the prominence of pulmonary artery and pulmonary blood flow in the RN. Most of the physiological changes reverted to the baseline value on return to Delhi thus proving that there were no permanent changes during short stay at extreme cold conditions.

Acclimatization at high altitude in gradual and acute induction.

The study assessed physiological responses to induction to high altitude first to 3,500 m and then to 4,200 m and compared the time course of altitude acclimatization in two groups of male volunteers. The acutely inducted group was transported by aircraft (AI) to 3,500 m in 1 h, whereas the gradually inducted group was transported by road (RI) in 4 days. Baseline recordings of basal cardiovascular, respiratory, and blood gas variables were monitored at sea level as well as at 3,500 m on days 1, 3, 5, and 7. Blood gases were measured on day 10 also. After 15 days at 3,500 m, the subjects were inducted to 4,200 m by road, and measurements were repeated on days 1, 3, and 5, except blood gas variables, which were done on day 10 only. Acute mountain sickness symptoms were recorded throughout. The responses of RI were stable by day 3 of induction at 3,500 m, whereas it took 5 days for AI. Four days in transit for RI appear equivalent to 2 days at 3,500 m for AI. Acclimatization schedules of 3 and 5 days, respectively, for RI and AI are essential to avoid malacclimatization and/or high-altitude illness. Both groups took 3 days at 4,200 m to attain stability for achieving acclimatization.

Changes in lung function during adolescence in athletes and non-athletes.

The purpose of this study was to evaluate the lung function in Indian athletes and non-athletes during adolescence. For this, lung functions in 40 boys (twenty athletes and twenty non-athletes) in the age range of 13 to 16 years, were evaluated over a period of two years at yearly intervals. The variables studied were Forced Vital Capacity (FVC), Forced Expiratory Volume in one second (FEV1), Expiratory Reserve Volume (ERV), Inspiratory Capacity (IC) and Maximum Voluntary Ventilation (MVV). Our results suggest that the development of the lung during adolescence under proper nutritional and health conditions is governed by the process of growth with no or negligible additional effects of physical activity. It is summarized that physical activity during growth may increase endurance in respiratory muscles. However, the findings of this study does not reject the possibility that lung size may increase by a strenuous and prolonged strength training regimen during adolescence.

Lung function in middle distance adolescent runners.

Lung functions (FVC, FEV1, ERV, IC AND MVV) were evaluated in 14 boys and 11 girls practising for middle distance running events in the age range of 13 to 17 years before and after one year training. The findings suggest that during adolescence, development of lung under proper nutritional and health conditions is governed by the process of growth with negligible additional effect of physical activity. However, physical exercises during growth may help in developing a reduced resistance to expiration and a greater endurance in respiratory muscles.

Age and height as predictors of peak expiratory flow rate in Indian girls.

Peak expiratory flow rate (PEF) was measured on 175 healthy Indian girls in the age range 8-18 years with the help of Wright's Peak Flow Meter. PEF was recorded in the post absorptive phase at least 1 h after breakfast. The subjects rested for 0.5 h before the test procedure and tests were carried out between 1000-11000 hrs to avoid diurnal changes. The highest of three recordings was noted as the subject's PEF. PEF, age, height and body weight were correlated with each other and an intercorrelation matrix between these variables has been designed. It was observed, after performing multivariate regression analysis, that age and height are significant predictors of PEF. A multiple linear regression equation and a nomogram have been constructed for predicting PEF from age and height in young healthy Indian girls.

Respiratory changes due to extreme cold in the Arctic environment.

Effects of acute exposure and acclimatisation to cold stress on respiratory functions were investigated in healthy tropical Indian men (n = 10). Initial baseline recordings were carried out at Delhi and thereafter serially thrice at the arctic region and once on return to Delhi. For comparison the respiratory functions were also evaluated on Russian migrants (RM; n = 7) and Russian natives (RN; n = 6). The respiratory functions were evaluated using standard methodology on a Vitalograph: In Indians, there was an initial decrease in lung vital capacity (VC), forced vital capacity (FVC), forced expiratory volume 1st s (FEV1), peak expiratory flow rate (PEFR) and maximum voluntary ventilation (MVV) on acute exposure to cold stress, followed by gradual recovery during acclimatisation for 4 weeks and a further significant improvement after 9 weeks of stay at the arctic region. On return to India all the parameters reached near baseline values except for MVV which remained slightly elevated. RM and RN showed similar respiratory functions at the beginning of acute cold exposure at the arctic zone. RN showed an improvement after 10 weeks of stay whereas RM did not show much change. The respiratory responses during acute cold exposure are similar to those of initial altitude responses.

Height-weight relationship in young healthy Indian girls.

The relationship between height and weight in young healthy Indian girls (8--18 years) was developed. It is concluded that the relationship of the form:log w = 0.98 h + 0.14 holds good to the data on height h (in metres) and weight w (in kilograms) for this group of subjects, the logarithm is taken to the base 10. The results of the present study show that Ehrenberg's equation of the form : log w = 0.8 h + 0.4 may not be extended upto the age of 18 years in young healthy Indian girls.

Effect of glucose electrolyte ingestion on physiological changes due to severe heat stress.

Severe heat stress experienced by aircrew during summer months can cause deterioration in performance. Acute heat stress can also lead to dehydration and loss of electrolytes. Previous studies emphasised the need of K+ replacement. This study was carried out to determine the effect of glucose electrolyte ingestion (ELECTRAL) on thermal strain parameters. Ten healthy male subjects in the age group of 19-43 years were exposed to an acute thermal environment of 50 degrees C Tdb with relative humidity of 30% for 40 min. twice each day on two different days with an interval of one hour in between the exposures. At the beginning of rest period electrolyte solution was ingested during electrolyte trials and water under control trials. Physiological parameters of Tsk, T or, HR and electrolyte concentration of Na+ and K+ in sweat did not show any significant difference in both the trials. Sweat loss was significantly higher during electrolyte trials.