title: The influence of tobacco smoking on the relationship between pressure and flow in the middle cerebral artery in humans.
abstract: BACKGROUND
  Cigarette smoking is associated with an increased risk of stroke but the mechanism is unclear. The study examined whether acute and chronic cigarette smoking alters the dynamic relationship between blood pressure and cerebral blood flow. We hypothesised that acute and chronic smoking would result in a cerebral circulation that was less capable of buffering against dynamic fluctuations in blood pressure. Further, these changes would be accompanied by a reduction in baroreflex sensitivity, which is reduced after smoking (acute smoking).
  
  
  METHODS
  We recruited 17 non-smokers and 15 habitual smokers (13 ± 5 pack years). Continuous measurements of mean cerebral blood flow velocity (transcranial Doppler ultrasound), blood pressure (finger photoplethysmography) and heart rate enabled transfer function analysis of the dynamic relationship between pressure and flow (gain, normalised gain, phase and coherence) and baroreflex sensitivity during supine rest before and after smoking a single cigarette (acute smoking).
  
  
  RESULTS
  There were no between-group differences in gain, phase or coherence before acute smoking. However, both groups showed a reduction in gain and coherence, associated with a reduction in baroreflex sensitivity, and increase in phase after acute smoking.
  
  
  CONCLUSIONS
  Contrary to our hypothesis, these findings suggest that in the face of a reduction in baroreflex sensitivity acute smoking may potentially improve the ability of the cerebral circulation to buffer against changes in blood pressure. However, chronic smoking did not alter the dynamic relationship between blood pressure and cerebral blood flow velocity. These results have implications on understanding mechanisms for attenuating stroke risk.
authors: Cardiovascular Systems Laboratory, University of Otago, Wellington, New Zealand.
authors: Karen C
authors: KC
authors: Peebles
authors: Helen
authors: H
authors: Horsman
authors: Yu-Chieh
authors: YC
authors: Tzeng
mesh_terms: D000328:Adult; D017704:Baroreflex / Q000502:physiology; D001783:Blood Flow Velocity; D001794:Blood Pressure / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003710:Demography; D005260:Female; D006801:Humans; D008297:Male; D020768:Middle Cerebral Artery / Q000503:physiopathology*; D009538:Nicotine / Q000009:adverse effects; D012907:Smoking / Q000009:adverse effects*
chemical_list: D009538:Nicotine
references: Philos Trans A Math Phys Eng Sci. 2009 Apr 13;367(1892):1319-36
references: 19324711
references: Science. 1996 Jul 12;273(5272):245-8
references: 8662509
references: Eur J Clin Invest. 2006 May;36(5):320-5
references: 16634835
references: Am J Physiol Heart Circ Physiol. 2006 Jul;291(1):H251-9
references: 16489099
references: J Physiol. 2009 Jun 1;587(Pt 11):2567-77
references: 19359366
references: J Chromatogr Sci. 2005 Mar;43(3):133-40
references: 15842752
references: J Auton Pharmacol. 1999 Apr;19(2):105-8
references: 10466943
references: Am J Physiol Heart Circ Physiol. 2004 Aug;287(2):H695-703
references: 15277201
references: J Appl Physiol. 1973 Dec;35(6):820-2
references: 4765817
references: Handb Exp Pharmacol. 2009;(192):29-60
references: 19184645
references: Am J Physiol. 1998 Jan;274(1 Pt 2):H233-41
references: 9458872
references: Stroke. 1992 May;23(5):693-6
references: 1579968
references: Am J Physiol. 1997 Sep;273(3 Pt 2):H1555-60
references: 9321849
references: J Hum Hypertens. 1989 Dec;3(6):443-9
references: 2691689
references: Circulation. 2002 Mar 12;105(10):1155-7
references: 11889006
references: J Physiol. 2011 Jul 1;589(Pt 13):3263-74
references: 21540346
references: Stroke. 2000 Jul;31(7):1672-8
references: 10884472
references: Neurosurgery. 1990 Sep;27(3):362-8
references: 2234328
references: Hypertension. 2003 Oct;42(4):481-7
references: 12975383
references: Brain Res. 2004 Nov 19;1027(1-2):48-58
references: 15494156
references: Hypertension. 2003 May;41(5):1102-5
references: 12682081
references: Nature. 1972 Apr 7;236(5345):308-10
references: 4552162
references: N Engl J Med. 1976 Sep 9;295(11):573-7
references: 950972
references: J Neurol Sci. 2002 Dec 15;205(1):15-20
references: 12409178
references: J Biol Chem. 1997 May 9;272(19):12257-60
references: 9139666
references: J Cereb Blood Flow Metab. 1996 Jul;16(4):746-9
references: 8964816
references: Stroke. 2003 May;34(5):1151-5
references: 12663877
references: Stroke. 2005 Dec;36(12):2595-600
references: 16254228
references: Stroke. 2008 Sep;39(9):2439-43
references: 18703815
references: Stat Med. 2003 Nov 30;22(22):3527-41
references: 14601017
references: Stroke. 1998 Aug;29(8):1656-65
references: 9707209
references: J Appl Physiol (1985). 2008 Oct;105(4):1060-8
references: 18617625
references: Circ Res. 2001 Feb 16;88(3):359-65
references: 11179206
references: Br J Anaesth. 2004 Nov;93(5):710-24
references: 15220174
references: Physiol Meas. 1998 Aug;19(3):305-38
references: 9735883
references: Arterioscler Thromb Vasc Biol. 2005 Dec;25(12):2630-5
references: 16210569
references: Stroke. 1983 Sep-Oct;14(5):720-4
references: 6658956
references: Cerebrovasc Brain Metab Rev. 1990 Summer;2(2):161-92
references: 2201348
references: JAMA. 1983 Nov 25;250(20):2796-800
references: 6644957
references: Circulation. 1998 Aug 11;98(6):528-34
references: 9714109
references: J Hypertens. 1997 Dec;15(12 Pt 2):1659-64
references: 9488219
references: Psychopharmacology (Berl). 1997 Jun;131(3):220-9
references: 9203232