Valsalva ratio: Assessment of autonomic modulation in patients of cervical spondylosis

Background: Cervical spondylosis is a common progressive degenerative disorder of the human spine often caused by the natural aging process. Osteophytic formations contribute to biomechanical changes that result in neural and vascular compression. The spinal compression of the obliquely passing cervical nerve roots can result in possible autonomic imbalance in the body. Valsalva maneuver is a simple, non-invasive and cost effective means to assess the autonomic activity. The results are appreciably reproducible if done properly under standardized conditions. Valsalva ratio is an important index of the baroreflex-mediated bradycardia and gives a fair idea about the parasympathetic tone. Aim: The aim of our study was to assess the level of autonomic activity by studying the valsalva ratio in patients with cervical spondylosis and to compare it with healthy controls. Materials and methods: This prospective random case control study was conducted at Pt. B. D. Sharma PGIMS, Rohtak. The study sample comprised of group I consisting of thirty randomly selected age and sex matched healthy controls and group II of thirty patients diagnosed with cervical spondylosis (age group 30-60 years of either sex). Results: In our study, valsalva ratio was found to be significantly low (p<0.01) in patients of cervical spondylosis as compared to healthy individuals. Conclusion: Altered parasympathetic tone can predispose the patients to hemodynamic instability leading to adverse cardiovascular implications in the long run.

Role of vagal and sinoaortic baroreflexes in circulatory adjustments to passive head up tilt.

To evaluate the contribution of vagal and sinoaortic baroreflexes in circulatory adjustments anaesthetized rabbits were subjected to 70 degree head up tilt with (i) both reflexes intact; (ii) after elimination of sinoaortic reflexes; (iii) after elimination of vagal reflexes; and (iv) after elimination of both categories of reflexes. The results suggest that vagal mediated baroreflexes from cardiopulmonary baroreceptors contribute significantly in circulatory adjustments to passive head up tilt while sinoaortic baroreflexes play the major role.

Cardiovascular responses to cold pressor test: a test for autonomic functions.

Circulatory dynamics during the cold pressor test, done by immersing the hand in water at 5 degrees C for one minute, were studied in 30 male healthy volunteers. All the subjects responded to the test with statistically significant increase in blood pressure (22.04%, p less than 0.001), heart rate (11.21%, p less than 0.001), galvanic skin resistance (36.17%, p less than 0.001) and decrease in forearm blood flow (40.85%, P less than 0.001). The measurement of cardiovascular responses following cold pressor test constitutes another test which can be used to test the efficiency of the autonomic nervous system in various autonomic neuropathies.

Role of vagal and sinoaortic baroreflexes in restoration of arterial pressure after acute mild haemorrhage in rabbits.

To evaluate the contribution of vagal and sinoaortic baroreflexes (SBR) in circulatory adjustments, anaesthetized rabbits were subjected to acute mild haemorrhage and the extent of recovery produced after haemorrhage was estimated. The recovery of arterial pressure after acute mild haemorrhage with reflexes intact was 96.19%, after elimination of SBR it was 79.20%, after bilateral vagotomy 87.38%, and after eliminating both reflex systems it was 75.66%. The results suggest that vagally mediated baroreflexes from cardiopulmonary baroreceptors contribute significantly in restoring the arterial pressure in response to haemorrhage while the sinoaortic baroreflexes play the major role.

Baroreceptor reflexes in postural control of circulation in rabbits.

The present study was undertaken to evaluate reflex cardiovascular responses to postural stress in rabbits. The changes in mean arterial pressure (MAP) and heart rate (HR) were monitored in the supine position and following sudden passive head up tilt (HUT), and head down tilt (HDT) to 70 degrees. The results show a significant increase in MAP (18.57%, P less than 0.001) and HR (2.92%, P less than 0.02) with HUT; and a marked decrease in MAP (43.48%, P less than 0.001) and HR (8.21%, P less than 0.001) with HDT (as compared to the values in supine position). The changes in MAP were found to be more marked than those in HR. The depressor responses to HDT were more marked than the pressor responses to HUT.

Decreased tolerance to orthostatic stress in diabetics.

Cardiovascular responses to head up tilt (HUT) were investigated in chronic diabetics (having disease of 8 to 10 years duration) and in control subjects. The parameters recorded were heart rate (HR), blood pressure (BP), forearm blood flow (FABF) and forearm vascular resistance (FAVR). Recordings were made first in the supine position, next after HUT, and thirdly in the recovery period after return to the supine position. Normal subjects responded to HUT by a marked increase in HR (P less than 0.001), decrease in FABP (P less than 0.001) and increase in FAVR (P less than 0.001). The diastolic blood pressure (DBP) and mean blood pressure (MBP) showed appreciable increase (P less than 0.001, P less than 0.01 respectively) without significant fall in systolic blood pressure (SBP). The maximum alteration in cardiovascular responses was observed immediately after HUT (within 15 sec). The cardiovascular responses to HUT in diabetics were found to be significantly impaired compared to control subjects. The impairment of cardiovascular responses in diabetics in indicative of autonomic neuropathy which can be detected by these tests before the development of clinical signs of the neuropathy.