Sphygmomanometric Blood Pressure Drop on Consecutive Measurements: The Search for a Cause.

This study was inspired by our oft-noted observation that the first sphygmomanometric reading of blood pressure (BP) is invariably higher than the subsequent ones recorded immediately thereafter. The objectives of this study were to establish the statistical validity of this observation and further, to probe the possible causes of the same. The sphygmomanometric BP was recorded in 30 non-obese young adults using two different protocols. In protocol-1, BP in the left arm was repeated thrice in quick succession, both in standing and supine postures. In protocol-2, BP was recorded in the supine position six times in quick succession, thrice in the left arm and immediately thereafter, thrice in the right arm. Data was compiled and analysed using appropriate statistical tests. In protocol-1, a statistically-significant drop in the blood pressure was consistently noted between quickly consecutive measurements in both standing and supine postures. Importantly, this pressure drop was not significantly affected by posture. In protocol-2, significant pressure drop was recordable from both arms. These findings rule out baroreflex as a cause of the pressure-drop on consecutive measurements and suggest a likely role of tissue compaction in the same.

A simple device for measuring static compliance of lung-thorax combine.

Explaining the concept of lung compliance remains a challenge to the physiology teacher because it cannot be demonstrated easily in human subjects and all attempts until now have used only simulation models. A simple device is described in the present article to measure the compliance of the "lung-thorax" combine in human subjects with the caveat that what is recorded is not "lung" compliance and the data generated are of little clinical use. The device comprises a spirometer, a manometer, a mouthpiece, and interconnecting tubes guarded with stopcocks.

Effect of Sub Maximal Dynamic and Static Exercises on QTc interval in Healthy Young Men.

INTRODUCTION: The QTc interval depends largely on cardiac repolarization since the duration of cardiac depolarization is fairly constant in the normal heart. QTc at rest as well as during exercise has many clinical implications. In this study, we have compared the relative effects of dynamic and static exercise on QTc. AIM: To measure QTc interval in young men at rest and also assess how it is further modulated by submaximal dynamic and static exercises. MATERIALS AND METHODS: This observational study was conducted in the Department of Physiology on 30 non-obese young men randomly selected from the students of our institute after obtaining the consent and institutional ethical clearance. Continuous blood pressure monitoring and ECG recording was done in the subjects. Baseline (pre-exercise), post submaximal dynamic (Harvard's step test) and post submaximal static exercise (hand-grip exercise) recordings of ABP and ECG were taken for analysis. The measured QT interval was corrected for heart rate using the formula of Bazett et al., {QTc=QT/RR(1/2)}.Statistical analysis was done using Graph pad Prism 5 software (California, USA). The baseline and post-exercise data were compared using paired t-test. A p<0.05 was taken to be statistical significant. RESULTS: There were statistically significant increases in HR, SBP, DBP and QTc interval after dynamic exercise in comparison to the baseline values (p<0.05). Significant increase in HR (p<0.05) with no significant change in QTc and other cardiovascular parameters were recorded following static exercise (p>0.05). CONCLUSION: Significant increase in QTc interval was observed after dynamic exercise, however, no change in QTc was observed following static exercise, and hence we conclude that static exercises may not be useful in assessing the cardiovascular status of an individual or in predicting cardiovascular events.

A preliminary study on the influence of glutathione S transferase T1 (GSTT1) as a risk factor for late onset Alzheimer's disease in North Indian population.

INTRODUCTION: Oxidative stress plays key role in pathogenesis of Alzheimer's disease. Glutathione S-transferases (GSTs), a family of phase-II isoenzymes, play a critical role in providing protection against electrophiles and products of oxidative stress. Among different classes of GSTs, GSTM1 (Mu) and GSTT1 (theta) are found to be genetically deleted which results in decreased expression of the concerned enzyme. This study aims at preliminary analysis of the frequency of deletion of GSTM1 and GSTT1 and their association with late-onset Alzheimer's disease. MATERIAL AND METHODS: In this study, association of the deletion type polymorphism of GST M1 and T1 as possible risk factors for dementia of Alzheimer's type was studied in 50 patients and 100 controls. Dementia was diagnosed by Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) criteria, Mini Mental State Examination (MMSE) and Clinical Dementia Rating (CDR) scale. Genotyping was done by multiplex Polymerase Chain Reaction (PCR). Associations between null genotype of either GSTM1 and GSTT1 or both with Alzheimer's disease were analyzed by Chi-Square test. RESULTS: Deletion of GSTT1 was found significantly associated with Alzheimer's disease (χ(2)=5.08, p=0.02*). CONCLUSIONS: The odds of Alzheimer's disease in null GSTT1 is found to be increased by 2.47 times in comparison to positive GSTT1.

Post-task changes in visual P300 and their reversibility through brief hyperventilation.

Long hours of continuous, mental task reportedly increase the average auditory P3 latency of the normal subjects significantly, a change that is thought to be related to mental fatigue. We have tried out several protocols of varying task difficulty and duration in an effort to study the onset of the assumed fatigue-related changes. The present study shows that changes in visual event-related potential occur in less than two minutes if the task is sufficiently rigorous. The changes occur both in latency and in amplitude. Moreover, the changes are reversible with a brief (30 second) period of hyperventilation. The changes were most marked at Fz. Following the difficult task, the P3 amplitude at Fz decreased from 8.588 micro/V +/- 0.966 to 5.800 microV +/- 0.795 and the P3 latency increased from 368 +/- 4 ms to 380 +/- 3. Following hyperventilation, the P3 amplitude at Fz reverted to 8.457 +/- 5 and the P3 latency reverted to 371 +/- 5 ms. These observations call for further investigations on the cause of the post-task changes and their quick reversibility.

Role of uterine artery velocimetry using color-flow Doppler and electromyography of uterus in prediction of preterm labor.

AIM: To evaluate the role of Doppler waveforms of uterine vessels and electromyography (EMG) of the uterus in predicting preterm labor. METHODS: One hundred ante-natal women at >or=24 weeks of gestation who fulfilled the selection criteria were included in the study. A single Doppler recording for bilateral uterine vessels was taken at >or=26 weeks gestation using the transvaginal route. Transabdominal EMG of the uterus was recorded serially at 4-week intervals from 24 weeks until delivery or until 37 weeks were completed. RESULTS: Women with a sensation of heaviness in the lower abdomen during pregnancy had a significant association with preterm delivery. Of the three Doppler indices, the systolic/diastolic ratio and the resistivity index of uterine vessels were found to have a sensitivity as high as 83-95% for the prediction of preterm labor. The electrical activity of uterine musculature, as recorded using EMG, showed that there was a statistically significant difference between the electrical activity recorded for the two groups at 31 weeks and later, while the duration of burst activity was significantly longer in the preterm group at 26 weeks and later. CONCLUSIONS: Patients with a dull aching sensation in the lower abdomen should not be neglected. Doppler of the uterine vessels and EMG of the uterus could prove to be a good predictor of preterm labor.

Post-task P3-changes following a brief, rigorous visual task indicate individual differences in the task-specific ability.

The P3 latency in an auditory oddball ERP paradigm is known to get prolonged after a few hours of mental task. The present study shows that it takes merely a few minutes of challenging visual mental activity to produce significant changes in P3 latency in the visual oddball ERP paradigm. However, the mental activity results in a shortening of P3-latency almost as often as it results in its prolongation. Similarly, the post-task P3 amplitude is higher or lower with nearly equal incidences. Following the task, the reaction time shortens as often as it prolongs. It seems that the P3 changes and their variations through electrode sites signify individual differences in the amount and extent of additional neuronal resources tapped by the subject in coping with the challenging task, and that it leaves an aftereffect for several minutes after the mental workload is withdrawn. These aftereffects get indexed in the P3 wave characteristics of a much simpler ERP paradigm with more change occurring in the better performers. In the clinical context, these observations raise doubts about the diagnostic value of P3 latency or amplitude without knowledge of the immediate history of mental workload.