A preliminary investigation into maximal expiratory pressures in some village children.

A clinical mercury sphygmomanometer was used to measure Maximal Expiratory Pressure (MEP) in 29 boys (mean age 8 +/- 1.4 yr) and 21 girls (mean age 7.6 +/- 1.5 yr) of a village in interior Maharashtra. The values of 70.6 +/- 13.4 mmHg SD for the boys and 61.9 +/- 18.9 mmHg for the girls were quite comparable to the respiratory pressures reported elsewhere in literature, even though the subjects were apparently poorly nourished. There was no statistical difference between the MEPs of boys and girls. The MEP was positively and significantly (P<0.01) correlated to height (r=0.51) and weight (r=0.05) in the boys. The MEP denoting respiratory muscle strength also correlated positively with handgrip power used to represent non-respiratory muscle strength (r=0.34) (P>0.05). The simple, reproducible method of measuring MEP as described may be useful for measuring this important physiological parameter at the bedside in children whose respiratory muscle function needs to be evaluated.

Lung functions with spirometry: an Indian perspective--II: on the vital capacity of Indians.

Spirometry has been used in India since 1929 to evaluate vital capacity. The mean value for this parameter has changed slightly for the better over about eight decades. It is currently recorded at about 21.8 ml/cm height for males and about 18 ml/cm height for females, the difference between the two sexes being statistically significant throughout the period studied. The vital capacity reaches its peak at about 30 years of age in both Indian men and women and declines there after. There is no significant statistical difference in the vital capacities of subjects from different regions of India. Composite regressions have been generated for use as reference equations for estimating. Vital capacity of Indians is lower than that of Caucasians, but the age related decline is much greater for Caucasians.

Lung functions with spirometry: an Indian perspective--I. Peak expiratory flow rates.

Peak expiratory flow rate is an effective measure of effort dependent airflow. It is relatively a simple procedure, and may be carried out in the field using portable instruments. The average PEFR of healthy young Indian males and females is around 500 and 350 lpm respectively. The PEFR reaches a peak at about 18-20 years, maintains this level up to about 30 years in males, and about 40 years in females, and then declines with age. Common regression equations for Indians enveloping major studies from various parts of the country have been formulated. Indian PEFR values compare favourably with other ethnic groups such as Americans and Europeans.

Heart rate and blood pressure responses of left-handers and right-handers to autonomic stressors.

We hypothesized that cerebral dominance may contribute to differences in cardio-vascular responses of right-handers (RH) and left-handers (LH) to autonomic stressors. We tested this hypothesis by exposing 14 RH, and 14 LH males to category I tests in which the hand and cerebral cortex were involved in performing the test viz.--i) Cold pressor test (CPT), ii) Handgrip dynamometry (HGD) and; category II (no use of hand)--i) Orthostatic Tolerance Test (OTT), ii) Valsalva Manuever (VM), iii) Controlled Breathing Test for sinus arrhythmia (SA) in a random sequence, and measured their heart rate (HR/min) and blood pressure (MAP mmHg). All subjects had similar resting HR and MAP values, and responded to the category I interventions with increased HR and BP. The absolute HR values of LH and RH did not differ significantly during the interventions. However, the increase in HR from control induced by the CPT, and the HGD was greater for LH (P<0.05). Also, LH showed a greater decrease in HR and MAP in the recovery phase (P<0.05). The VAS scores for degree of discomfort during the CPT were similar for both the groups. During the OTT, the increase in HR was more in RH (P<0.05). The Valsalva ratios for LH and RH were similar. Our findings suggest that the autonomic control over the cardio-vascular system may be different in LH and RH, and that this imbalance could be attributable to a variation in cerebral dominance.

Comparison of respiratory sensations induced by J receptor stimulation with lobeline in left handers & right handers.

We examined the hypothesis that right handers and left handers may differ in sensory perceptions and respiratory responses to J receptor stimulation with intravenous injections of lobeline HCl in incremental doses. The comparison was made between 6 right handers and 9 left handers (all males) for (i) the dose of lobeline required to produce sensory threshold (viz., first appearance of respiratory sensations) and cough threshold (first appearance of cough); and (ii) latency and duration of sensations for sensory and cough threshold. All these comparisons were not found to be significant statistically. The sensation of breathlessness, and feelings of drowsiness, giddiness and headache were perceived in 3 of the 9 left handers, and in none of the right handers, but the difference was not significant. Reflex bradycardia was recorded only in left handers (5 of 9). The time (sec) for cough threshold was negatively correlated to threshold dose of lobeline (r = -0.5, and P < 0.05). The left handers perceived cough at the threshold as more distressing as compared with right handers (VAS P < 0.05). In conclusion, handedness did not influence J receptor responses to i.v. lobeline.

Helium/oxygen flow volume curves in normal Indian males > 50 year, and the effect of bronchodilator aerosols on airflow variables in this subject group.

Fourteen healthy males (mean age 54.7 yr) described maximal flow volume curves after Air breathing (AB) and after inspiring 10 deep breaths of a mixture of 80% Helium/20% Oxygen (He/O2). Vmax 50% FVC as obtained from the AB curves was 3.11 +/- 1.27 lps, and this increased by 38.1 +/- 17%, with He/O2. The Vmax 50% He-O2/Air ratio was 1.32 +/- 0.17, while the V iso V was 1.1 +/- 0.35 liters (30.9% of the FVC). Inhalation of 80 micrograms (4 puffs) of Ipratropium bromide, a vagolytic aerosol, or salbutamol (200 micrograms; 2 puffs), a beta 2 adrenergic stimulant did not alter the He/O2 curves significantly. As another aspect of the study, airflow variables viz. Vmax 50% of the FVC, Vmax 25%-75%, and Vmax 25% were measured from the AB curves, and the effect of bronchodilator aerosols was investigated in order to evaluate the degree of control of the bronchomotor tone by either the adrenergic receptors, or the vagus. Only the Vmax 25%-75% increased significantly with Salbutamol administration. While the degree of increase brought about by salbutomol aerosol for all of the variables under investigation was more than that seen with ipratropium br., the difference in this increase between the two bronchodilators used was not significant. The result may indicate that almost an equivocal influence is exerted by the two arms of the autonomic nervous system on bronchomotor tone in middle aged normal males, and that a more sensitive test (viz He-O2 breathing) does not elucidate this any further.

Beta-adrenoreceptor blockade attenuates heat-induced tachycardia,but not the tolerance to the stress.

Ten healthy males (age 34 +/- 3 yr 9 SE) underwent 40 min of heat exposure (WD 39.7.C) after 2 hours of ingesting 120 mg of Propranolol (Inderal; ICI), or a placebo, in a random manner, the exposures being about a week apart. That there was no placebo effect was ensured by giving a control run (no medication). In the placebo trials, the end-experiment heart rate had increased by 52%, while after propranolol the increase was only 43%. Regression analysis showed that with the placebo, the HR increased by 22 beats/min/o rise in core (aural) temperature, while with propranolol, the rise (14 beats/min) was significantly lower (P < 0.02). The various heat strain indices viz the Craig's Index, the Body heat storage (Kilocals/m2/hr), and the effective heat storage were also similar for both the treatments. We conclude that beta-adrenoreceptor activity plays a significant role in producing tachycardia of heat exposure in humans, but blocking this activity with propranolol does not affect tolerance to heat stress.

Calcium channel blockers and the CVS reflex responses during lower body suction.

Nine normal men (mean age 27.6 yr) were exposed to continuous lower-body suction pressure (LBSP) of -20 to -50 mmHg (for 5 min at each level) on four different occasions after having consumed a single oral therapeutic dose of either diltiazem, nifedipine, verapamil, or a placebo, randomly, in a single blind manner. The suction was applied at 12.30 pm in all experiments, while the medications were administered in such a manner so that their expected peak plasma levels would have been achieved at the time of suction application. The cardiovascular reflex effects commenced at a pressure of -30 mmHg, and peaked at -50 mmHg. The increases in the heart rate for all treatments at -50 mmHg was statistically similar (about 16-20 beats/min). The systolic BP fell by about 9 mmHg for the placebo experiments, and this change was not different from the changes produced by the 3 Calcium channel blocker treatments. The diastolic BP increase was about 3 mmHg. The Cardiac index did not vary significantly. Our results suggest that the commonly used Ca++ channel blockers do not adversely affect orthostatic tolerance.

Peak expiratory flow rates in elderly Indians.

Peak expiratory flow rates were measured in 124 normal elderly men (55-85 yr) using the Wright's peak flow meter. In the less than 60 yrs age group (n = 32; mean age 57.7 yr) the PEFR was 431 +/- 13 lpm, while for the group greater than 60 yr (mean age 69.0 +/- 6.0; n = 92), the PEFR value was 373 +/- 11 1pm. These values are similar to those reported in other Indian studies, suggesting that the ethnic variations amongst Indian subjects do not affect the PEFR. However, the reported values are lower than those observed in Europeans, but greater than those of Chinese. The PEFR regressed at a rate of 4.47 1pm/year increase in age, but is positively correlated to the subjects' height (cm), and their FVC and FEVI. The smokers had a significantly higher PEFR as compared with the non-smokers. This finding was contrary to what was expected.

Lower-body suction and cardiovascular reflexes: physiological and applied considerations.

Lower body subatmospheric pressure (LBSP) can be applied in a graded manner to a supine subject enclosed in a box upto the level of the iliac crest in order to elicit cardiovascular reflexes without a change of posture, and without a gravity induced shift of the central blood volume into the periphery. The procedure effectively produces a controlled, non-haemorrhagic hypovolaemia. The method may be used to differentiate the reflex cardiovascular effects induced by the deactivation of the low-pressure cardiovascular receptors (LBSP less than 30mmHg), and those produced by the deactivation of the arterial baroreceptors (LBSP greater than 30 mmHg). The former results in an increase in the limb vascular resistance without a change in heart rate and blood pressure, while the latter produces a tachycardia, an increase in the diastolic BP with a fall in the sytolic BP. The CVP and the cardiac output reduce with increasing suction. Cardiovascular reflex effects of -40 mmHg are similar to those produced by a change of posture from supine to standing. Vaso-vagal syncope appears with increasing frequency when LBSP exceeds -60 mmHg even in the normal subjects. The test is useful in the aeromedical assessment of apparently normal individuals with low orthostatic tolerance, in the evaluation of the effects of physiological and pharmacological interventions on cardiovascular reflexes, and in the evaluation of patients of autonomic neuropathies. LBSP is also a means of inducing safe, well controlled syncope in order to study the genesis of this phenonmenon.

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.

Postural stress tests for the clinico-physiological evaluation of cardiovascular reflexes.

Postural stress tests are useful in the assessment of cardiovascular reflex response of normal subjects who may be involved in specialised occupations such as flying; in order to study the effects of physiological stresses such as heat stress, hypoxia, simulation of weightlessness; physiological evaluation of cosmonaut candidates, in patients who may have autonomic neuropathy. Most commonly quiet standing is used but head-up tilt table test and the application of lower body suction may provide a better method of evaluation. These three tests for assessing reflex cardiovascular function are discussed.

Beta-adrenoceptor blockade and cardiovascular response to the cold pressor test.

Seven healthy subjects immersed a hand in random order in either warm water or in cold water at 5 degrees C for 2 min, after taking orally a single dose of 120 mg of propranolol or a placebo in a double blind fashion. The cold stress resulted in a significant increase in blood pressure and the rate pressure product without a change in heart rate. Beta-adrenoceptor blockade did not affect the pressor response the cold. The changes induced by the cold stress in the cardiovascular variables in the placebo and propranolol experiments were not statistically different. The highest rate pressure product during the cold pressor test was about 109 units. This was well below the pain threshold value of about 200 found during exercise in patients with ischaemic heart disease. In the recovery phase, the cardiovascular variables reverted to pre-immersion values within 1 min inspite of continued low hand skin temperature.