Buteyko breathing technique for obstructive Eustachian tube dysfunction: Preliminary results from a randomized controlled trial.

PURPOSE: To assess the effectiveness of Buteyko breathing technique in patients with obstructive Eustachian tube dysfunction (ETD). MATERIALS AND METHODS: Fifty-one patients (77 ears) aged between 21 and 62 years were randomized to Buteyko breathing in conjunction with medical management (nasal steroid) group or medical management alone group. The Eustachian Tube Dysfunction Questionnaire (ETDQ-7) symptom scores, tympanogram, positive Valsalva maneuver were evaluated at baseline, 6-week and 12-week follow-up. RESULTS: Normalization of ETDQ-7 symptom scores at 6-week follow-up was observed in 30.0% (12/40) of the Buteyko breathing group versus 16.2% (6/37) of the controls (P > 0.05). At 12-week follow-up, the ratio rose to 50.0% (20/40) in the Buteyko breathing group and 24.3% (9/37) in the controls (P < 0.05). Tympanogram normalization at 12-week follow-up was observed in 53.6% (15/28) of the Buteyko breathing group versus 26.9% (7/26) of the controls (P < 0.05). The Buteyko breathing group showed slight improvement in positive Valsalva maneuver at 6- and 12-week follow-up (P > 0.05). CONCLUSIONS: Our study shows that Buteyko breathing technique might be an effective adjunctive intervention in treatment of obstructive ETD, especially for those patients who are refractory to medical treatment and cannot afford Eustachian tube balloon dilation surgery.

[Endovascular treatment of a patient with post-thrombotic disease and obstruction of a cava filter]. / Éndovaskuliarnoe lechenie bol'nogo s posttromboticheskoi bolezn'iu i obstruktsiei kava-fil'tra.

Balloon angioplasty and stenting have increasingly been gaining widespread application for treatment of post-thrombotic alterations in the system of the vena cava. Endovascular ultrasonographic examination makes it possible with the utmost degree of reliability to determine both the extension and degree of the narrowing of venous segments, thus proving a possibility of choosing a venous stent of an appropriate diameter. Restoration of an adequate venous lumen leads to normalization of blood flow and elimination of venous hypertension. However, unsolved as yet remains the problem concerning proper management of post-thrombotic obstructions of the inferior vena cava at the level of a cava filter. Owing to a wide variety of configurations of cava filters to deploy, there are no common approaches to elimination of such obstruction. Presented herein is a clinical case report regarding successful endovascular treatment of a patient diagnosed with post-thrombotic disease secondary to endured thrombosis. The findings of both phlebography and endovascular ultrasonographic examination made it possible to diagnose obstruction of the left common iliac vein, external iliac vein, and inferior vena cava to the level of the cava filter previously deployed. In the segment of the inferior vena cava at the level of the cava filter also revealed was a pronounced luminal narrowing exceeding 90% of its diameter. We carried out stenting of the common and external iliac veins, inferior vena cava, and the cava filter. Swelling of the left leg subsided spontaneously within 2 weeks and the first postoperative month was accompanied by gradual disappearance of the previously existing feeling of heaviness in the lower limbs and a dramatic decrease in fatigue by the end of the working day.

Morphological analysis of pressure wave in the arterial tree with stenosis - a modeling approach.

This paper describes the morphological changes in peripheral signals due to arterial diseases with various severity conditions and site of stenosis using modeling approaches, and its effect in the morphological parameters of radial artery. As stenosis induces abrupt change in geometry and elastic properties of arterial tree (constitutes major reflection sites), hybrid model is well suited for studying the changes in shape of the pressure and flow wave transmitted through the stenosis. These morphological changes in wave shape of peripheral signal have significant diagnostic value in both modern and traditional medicine systems. It can be used for the quantitative assessment of the severity of the arterial diseases.

The effects of electroacupuncture on the extracellular signal-regulated kinase 1/2/P2X3 signal pathway in the spinal cord of rats with chronic constriction injury.

BACKGROUND: Electroacupuncture (EA), as a traditional clinical method, is widely accepted in pain clinics, but the analgesic effect of EA has not been fully demonstrated. In the present study, we investigated the effect of EA on chronic pain and expression of P2X3 receptors in the spinal cord of rats with chronic constriction injury (CCI). METHODS: The study was conducted in 2 parts. In part 1, Sprague Dawley rats were divided into 6 groups (n = 10): sham-CCI, CCI, LEA; CCI + 2 Hz EA at acupoints), HEA; CCI + 15 Hz EA at acupoints), NA-LEA (CCI + 2 Hz EA at nonacupoints), and NA-HEA (CCI + 15 Hz EA at nonacupoints). EA treatment was performed once a day on days 4 to 9 after CCI. Nociception was assessed using von Frey filaments and a hotplate apparatus. The protein and the messenger RNA (mRNA) levels of P2X3 receptors in the spinal cord were assayed by Western blotting and real-time polymerase chain reaction, respectively. In part 2, rats were divided into 5 groups (n = 10): sham-CCI, CCI, EA (CCI + EA at acupoints), NA-EA (CCI + EA at nonacupoints), and U0126 (CCI + intrathecal injection of U0126). EA treatment was conducted similar to part 1. Rats were given 5 µg U0126 in the U0126 group and 5% dimethyl sulfoxide intrathecally. Ten microliters was used as a vehicle for the other 4 groups twice a day on days 4 to 9 after CCI. Extracellular signal-regulated kinase 1/2 (ERK1/2) and ERK1/2 phosphorylation in the spinal cord were also assayed by Western blotting. RESULTS: EA treatment exhibited significant antinociceptive effects and reduced the CCI-induced increase of both protein and mRNA expression of P2X3 receptors in the spinal cord. Furthermore, 2 Hz EA had a better analgesic effect than 15 Hz EA, and the protein and mRNA level of P2X3 receptor in spinal cord were lower in rats treated with 2 Hz EA at acupoints than 15 Hz EA at acupoints. Either EA at acupoints or intrathecal injection of U0126 relieved allodynia and hyperalgesia and reduced the expression of P2X3 receptors and ERK1/2 phosphorylation in the spinal cord. CONCLUSIONS: The data demonstrated that EA alleviates neuropathic pain behavior, at least in part, by reducing P2X3 receptor expression in spinal cord via the ERK1/2 signaling pathway. Low frequency EA has a better analgesic effect than high frequency HEA on neuropathic pain.

Neurogenic stunned myocardium after acute hydrocephalus.

Neurogenic stunned myocardium (NSM) is a syndrome of cardiac stunning after a neurological insult. It is commonly observed after aneurysmal subarachnoid hemorrhage but is increasingly being reported after other neurological events. The underlying mechanism of NSM is believed to be a hypothalamic-mediated sympathetic surge causing weakened cardiac contractility and even direct cardiac myocyte damage. The authors report 2 cases of NSM in pediatric patients after acute hydrocephalus. Both patients experienced severe cardiac dysfunction in the acute phase but ultimately had a good neurological outcome and a full cardiac recovery. The identification, treatment, and outcome in 2 rare pediatric cases of NSM are discussed, and the history of the brain-cardiac connection is reviewed.

Motor cortex stimulation in rats with chronic constriction injury.

Motor cortex stimulation (MCS) has gained a significant role in treatment of neuropathic pain. In order to evaluate effect of MCS in experimental animals we applied MCS to rats with neuropathic pain, which was evoked by chronic constriction injury (CCI) to the left sciatic nerve. Pain thresholds of both hind limbs were measured before, immediately after MCS, 1 h after MCS and 1 day after MCS. Effect of the stimulation was studied with respect to laterality (contralateral and ipsilateral MCS) and duration (short-term 10-min and long-term 1-h stimulation). It was found out that in control rats MCS did not affect thermal nociceptive thresholds. However, in CCI animals following results were obtained: difference score (difference in paw withdrawal latency between ligated and non-ligated hind limb) significantly decreased after both short- and long-term contralateral MCS; the difference score after the long-term ipsilateral MCS (related to the ligated hind limb) was not significantly different from that of intact animals; the effects of the contralateral short-term and the ipsilateral long-term stimulation faded within 1 h after the end of MCS, while the effect of the contralateral long-term MCS remained 1 h after the end of the MCS and faded within 24 h. It is concluded that MCS in experimental animals exerts similar effects as in human suffering from neuropathic pain and that the effect might be evoked from both cerebral cortices.

Quercetin-supplemented diets lower blood pressure and attenuate cardiac hypertrophy in rats with aortic constriction.

Quercetin (Q), a flavonoid found in berries and onions, can reduce blood pressure in hypertensive animals and inhibit signal transduction pathways in vitro that regulate cardiac hypertrophy. We hypothesized that quercetin could prevent cardiovascular complications in rats with abdominal aortic constriction (AAC). Rats consumed standard or Q-supplemented chow (1.5 g Q/kg chow) for 7 days before AAC or sham surgery (SHAM, n = 15; AAC, n = 15; SHAMQ, n = 15; AACQ, n = 14). Fourteen days after surgery, plasma and liver Q concentrations were elevated (P < 0.05) and hepatic lipid oxidation was reduced (P < 0.05) in Q-treated versus untreated rats. Carotid arterial blood pressure and cardiac hypertrophy were attenuated (P < 0.05), and cardiac protein kinase C betaII translocation was normalized (P < 0.05) in AACQ versus AAC. Expression of cardiac beta-myosin heavy-chain mRNA was also reduced in AACQ versus AAC (P < 0.05). However, extracellular regulated kinase 1/2 phosphorylation was similar in AAC versus AACQ. The level of aortic endothelial dysfunction (wire myography) was also similar between AAC and AACQ, in spite of reduced aortic thickening in AACQ. Importantly, Q-treated rats did not show any deleterious changes in myocardial function (echocardiography). Our data supports an antihypertensive and antihypertrophic effect of Q in vivo in the absence of changes concerning vascular and myocardial function.

Antinociceptive action of the extract and the flavonoid quercitrin isolated from Bauhinia microstachya leaves.

This study examined the antinociceptive effect of Bauhinia microstachya (Leguminosae), a native plant widely distributed in the South of Brazil, in several chemical and mechanical models of pain. The methanolic extract (ME) from B. microstachya (3--30 mg kg(-1), i.p.) and the isolated compound quercitrin (1--10 mg kg(-1), i.p.), given 30 min earlier, produced a dose-dependent inhibition of acetic-acid-induced visceral pain in mice, with a mean ID50 value (dose necessary to reduce the nociceptive response by 50% relative to the control value) of 7.9 and 2.4 mg kg(-1), respectively. The ME of B. microstachya (3--100 mg kg(-1), i.p., 30 min earlier) also caused a dose-dependent inhibition of capsaicin-induced pain, with a mean ID50 value of 18.8 mg kg(-1). Moreover, the ME (3--100 mg kg(-1), i.p., 30 min earlier) produced marked inhibition of both phases of formalin-induced pain, with mean ID50 values for the neurogenic and the inflammatory phases of 30.3 and 17.2 mg kg(-1), respectively. In addition, the ME of B. microstachya (3--300 mg kg(-1), i.p., 30 min earlier) inhibited, in a graded manner, the hyperalgesia induced by bradykinin (3.2 microg/paw), substance P (13.5 microg/paw), carrageenan (300 microg/paw), capsaicin (100 microg/paw) and adrenaline (100 ng/paw) in the rat paw, with mean ID50 values of 20.5, 17.9, 101.8, 54.2 and 99.7 mg kg(-1), respectively. Taken together, these data demonstrate that ME of B. microstachya elicited a pronounced antinociceptive action against several chemical and mechanical models of pain in mice and rats. The precise mechanism responsible for the antinociceptive effect of the extract still remains unclear, but seems to be partly related to modulation of the release or action of pro-inflammatory mediators involved in the models of pain used. Finally, the flavonoid quercitrin isolated from this plant appears to contribute for the antinociceptive property of the methanolic extract.

[Nitric oxide and isolated aortic contraction in a pregnant hypertension model by the inhibition of nitric oxide synthase in pregnant Wistar rats]. / Monoxyde d'azote (NO) et contraction de l'aorte isolée dans un modèle d'hypertension artérielle gravidique par inhibition de la NO synthase chez la rate Wistar gestante.

During gestation endothelium induces decreases in vascular responses to vasopressor agents but endothelium disease is followed by hypertension and enhanced vascular reactivity during preeclampsia. In a rat model of preeclampsia induced by NO synthase inhibition we study here isolated aortic contractions. From day 13 of gestation 2 groups of Wistar female rats were fed control (C) or nitro-arginine enriched diets (0.063%, i.e. 30 mg/kg/d) (treated) (T). On gestational day 20 systolic blood pressure (SBP, mmHg) is measured by tail cuff method and isolated thoracic ring aorta contractions are studied after depolarisation (KCl 60 mM) or norepinephrine (cumulative concentrations 10-9 M-10-5 M). After chronic NOS inhibition, hypertension develops: SBP is 154 +/- 2.17 in T and 116 +/- 3.75 in C, p < 0.01 and significant proteinuria (mg/d) appears: T, 63.4 +/- 21.6 versus C 3.08 +/- 0.48, p < 0.01. NO synthase inhibition in treated rats impairs the depressed contractile response obtained in the presence of endothelium in control rats but addition of L-arginine suppresses the effect of nitroarginine. Taking in account our results and those described in literature it appears that L-arginine treatment could ameliorate some pathologic pregnancies.

Implantation of Accuflex and Strecker stents in malignant bronchial stenoses by flexible bronchoscopy.

Silicone and metal stents are available for the treatment of malignant bronchial stenoses. This project sought to compare the self-expanding nitinol Accuflex stent (Boston Scientific Corp; Watertown, Mass) with the passively expandable tantalum Strecker stent (Boston Scientific Corp; Watertown, Mass), both implanted by flexible bronchoscopy under local anesthesia and sedation. In 51 patients with malignant bronchial stenosis, 14 nitinol and 51 tantalum stents were used and stenoses of 75 to 100% were treated. The intervention was successful in all but one patient; a mean patency of 93% was achieved. In the follow-up period, the probability of survival was significantly lower in patients with total bronchus occlusion than in patients with stenotic alterations (44 vs 109 days; p<0.05). In 10 patients, lung function analysis after stent implantation revealed a significant increase in PaO2 (65 vs 71 mm Hg; p<0.01), inspiratory vital capacity (2.5 vs 2.7 L; p<0.05), and FEV1 (1.8 vs 2.0 L; p<0.05). Mucus retention was the main (39%) adverse factor in the early phase after stent implantation, whereas tumor penetration became the most frequent problem (67%) in the later phase. Recanalizing interventions were necessary in 18% of the cases in which tumor penetration occurred. Stent distortion occurred in 12 patients with Strecker and in none with Accuflex stents. In comparison to the Strecker stent, the self-expanding Accuflex stent is preferable owing to its excellent flexibility and faster delivery system. Both types of stents could be sufficiently deployed within the lesion and allowed for highly precise positioning. Furthermore, no general anesthesia was required. The fiberbronchoscopic mode of implantation under sedation is very efficient even for tumor patients with severe impairment of their physical and respiratory condition.

Hypertension increases the contractions to sumatriptan in the human internal mammary artery.

BACKGROUND: The internal mammary artery is the graft of choice for myocardial revascularization. The tendency to spasm increases toward the distal end of the internal mammary artery, which is the portion generally used for anastomosis. The distal internal mammary artery is more pharmacologically responsive to 5-hydroxytryptamine and several other vasoconstrictor agents than its midsection. METHODS: We examined the effects of 5-hydroxytryptamine and a 5-hydroxytryptamine1-like receptor agonist sumatriptan on internal mammary artery segments (length, 3-4 mm) obtained from patients undergoing coronary artery bypass grafting. To unmask a 5-hydroxytryptamine1-like receptor-mediated contractile response, threshold concentrations of potassium chloride were used. RESULTS: 5-Hydroxytryptamine induced concentration-dependent contractions in all, quiescent and potassium chloride precontracted, preparations. Sumatriptan induced marked contraction in some of the quiescent internal mammary artery rings, whereas it elicited marked and concentration-dependent contractions in all of the preparations given a moderate tone by a threshold concentration of potassium chloride. The sensitivity to sumatriptan was higher in potassium chloride-precontracted distal arteries than it was for the quiescent distal segments. Additionally, the sensitivity to and the efficacy of sumatriptan were much more markedly potentiated by precontraction in the preparations taken from hypertensive patients. CONCLUSIONS: The more marked potentiation of the responses in arteries from hypertensive patients may be one of the factors influencing the patency rates.

Betelnut chewing causes bronchoconstriction in some asthma patients.

A previous questionnaire interview had revealed that betelnut chewing may aggravate asthma in 61% of asthma patients attending an outpatient clinic at Port Moresby General Hospital; the rest said it had no effect. The aim of the present study was to verify patients' subjective feelings through objective measurements. 7 asthma patients (Group C) who said betelnut aggravated their asthma, 8 asthma patients (Group B) who denied any effect and 8 nonasthmatic, healthy subjects (Group A) were given betelnut with accompanying ingredients and asked to chew as they would usually chew it. Their spirometric forced expiratory volume in the first second (FEV1) readings, heart rate and blood pressure were monitored before and after this challenge. Group A nonasthmatic subjects experienced only minor rises and falls in their FEV1 in response to betelnut chewing. 3 patients in Group B experienced overall rises (mean maximal % rise 25 +/- 19) while 5 patients had overall falls (mean maximal % fall 11 +/- 6). In Group C 1 patient had an overall rise in her FEV1 (maximal rise 10%) while 6 patients had falls (mean maximal % fall 22 +/- 7). In all groups the heart rate increased in response to betelnut. Betelnut chewing caused bronchoconstriction as demonstrated by decreases in FEV1 in a majority of the asthmatic patients studied; hence betelnut may act as a trigger factor for their asthma. In a few others increases in FEV1 were noted, while the rest experienced only minor changes.

Development of a new laser-Doppler microvelocimetering and its application in patients with coronary artery stenosis.

A new Laser-Doppler microvelocimetering (LDMV) was developed to study blood flow in individual vessels in patients with coronary artery stenosis. The LDMV measures steady blood flow velocity, diameter of vessels and pulsation flow. In addition, the effects of China's traditional herbs--Salvia Mitiorrhyza and other drugs--on the blood flow in the patients were investigated. LDMV constitutes a new quantitative procedure and is a promising tool for rapid monitoring of tissue perfusion in cardiovascular disease and estimating the action of drugs on microcirculation.

Refractoriness of eucapnic hyperventilation-induced bronchoconstriction in rabbits.

The mechanism of refractoriness in bronchoconstriction after repeated hyperventilation was investigated in 18 sensitized rabbits. Rabbits were separated into three groups: an untreated control group (n = 7), a cimetidine-treated group (n = 6), and an indomethacin-treated group (n = 5). After anesthetization, hyperventilation was performed for 15 min (120 breaths/min, 7 ml/kg tidal volume) with dry air containing 5% CO2. Total lung resistance (RL) and dynamic compliance (Cdyn) were measured before (baseline) and after hyperventilation challenge. After RL and Cdyn had returned to baseline values, the hyperventilation challenge was repeated. In the control group maximal increase in percent RL (max %RL) was 49 +/- 9% after the first challenge, but 16 +/- 4% after the second challenge, indicating refractoriness. A similar tendency was observed in percent Cdyn. In the cimetidine- and indomethacin-treated groups, max %RL were 42 +/- 3% and 60 +/- 15% after the first challenge, and 35 +/- 8% and 60 +/- 7% after the second challenge, respectively, indicating no refractoriness. These results suggest that the H2-receptor and bronchodilating prostanoids play an important role in producing the refractoriness to bronchoconstriction observed in sensitized rabbits after repeated hyperventilation.

Extracellular metabolites of Pseudomonas aeruginosa produce bronchoconstriction by different mechanisms.

Bacterial supernatants (BS) obtained from broth cultures of Pseudomonas aeruginosa cause bronchoconstriction in sheep, suggesting that BS contain proinflammatory metabolites. In this study we investigated the mechanism(s) responsible for this bronchial effect. BS were obtained from 48 h cultures and sterilized by filtration. Sheep (n = 6) were intubated and swallowed an esophageal balloon for the measurement of specific lung resistance (SRL). Aerosols of BS (3 ml total) immediately increased SRL (541%). Neither aerosolized broth (control) nor inhaled endotoxin in excess of that contained in the BS had an effect. BS challenges were repeated on separate occasions except that the sheep were treated 30 min before challenge with the anticholinergic agent atropine (0.2 mg/kg, intravenously); the anti-allergic agent nedocromil (1 mg/kg, aerosol); the histamine H1 antagonist chlorpheniramine (2 mg/kg); or the bradykinin (BK) B2 receptor antagonists NPC-567 (5 mg/ml, aerosol) or NPC-17761 (1 mg/ml aerosol). The results showed that greater than 90% protection (p < 0.05) was achieved when the animals were pretreated with atropine, nedocromil sodium, or either of the two BK antagonists, but only 27 +/- 21% protection was seen with chlorpheniramine pretreatment. These findings are characteristic of a BK-mediated response. Analysis of bronchoalveolar lavage fluid obtained before and after BS challenge confirmed that i-kinins, but not histamine, increased (p < 0.05) from 61 +/- 7 to 304 +/- 55 pg/ml. Control (broth) challenges produced no such change. To identify the metabolites involved, we tested the effects of aerosolizing two suspected components of BS, 1-hydroxyphenazine (1-HP) and pyocyanine (PYO) in five sheep.(ABSTRACT TRUNCATED AT 250 WORDS)

Action of carbon dioxide on hypoxic pulmonary vasoconstriction in the rat lung: evidence against specific endothelium-derived relaxing factor-mediated vasodilation.

OBJECTIVES: The effect of hypercapnia on pulmonary vascular tone is controversial with evidence for both a vasoconstrictor and vasodilator action. The objective of this study was to investigate the possibility that this dual response to CO2 could be explained by a direct constrictor action on smooth muscle and an indirect dilator action via the release of endothelium-derived relaxing factor. The effect of ventilation with hypercapnia (FICO2 0.15) on pulmonary pressor response to hypoxia (FIO2 0.3) was investigated. DESIGN: Prospective, randomized study. SETTING: The National Heart and Lung Institute, UK. SUBJECTS: The isolated, blood-perfused rat lung. INTERVENTIONS: Angiotensin-II and a blocker of endothelium-derived relaxing factor synthesis, NG-monomethyl-L-arginine (L-NMMA). MEASUREMENTS AND MAIN RESULTS: The vasomotor effect of hypercapnia depended on pulmonary arterial pressure. Under resting tone, CO2 acted as a mild constrictor (change in mean pulmonary arterial pressure from 14 +/- 2 to 15 +/- 2 mm Hg, n = 4; p < .05. At increased tone, induced either by hypoxia or Angiotensin-II, CO2 was a vasodilator. Thus, hypoxia increased mean pulmonary arterial pressure from 17 +/- 2 to 32 +/- 2 mm Hg (n = 8; p < .01), but simultaneous ventilation with hypoxia and hypercapnia reduced this by 16 +/- 1% (p < .01). Angiotensin-II (1 microgram) increased pulmonary arterial pressure from 14 +/- 2 to 39 +/- 5 mm Hg (n = 8; p < .01), but with hypercapnia, this angiotensin-induced pulmonary vasoconstriction was reduced by 18 +/- 6% (p < .001). The reduction in hypoxic pulmonary vasoconstriction induced by hypercapnia was not significantly different from that seen with Angiotensin-II hypercapnia. Blocking endothelium-derived relaxing factor synthesis using 30 microM NG-monomethyl-L-arginine did not significantly change either basal pulmonary arterial pressure or the response to hypercapnia, but increased hypoxic pulmonary vasoconstrictor by 24 +/- 4% (n = 4; p < .01). There was no significant difference between the change in hypoxic pulmonary vasoconstriction induced by hypercapnia after saline control (21 +/- 8% decrease) and the change in hypoxic pulmonary vasoconstriction caused by CO2 after 30 microM L-NMMA (25 +/- 10% decrease, p < .05, n = 8). CONCLUSION: Endothelium-derived relaxing factor seems unlikely to specifically modulate CO2-induced vasodilation in the rat pulmonary circulation.

[Effect of calcium antagonists on cerebral and systemic hemodynamics in patients with ischemic disorders of cerebrovascular circulation]. / Vliianie antagonistov ka'ltsiia na tserebra'lnuiu i sistemnuiu gemodinamiku u bo'lnykh s ishemicheskimi narusheniiami mozgovogo krovoobrashcheniia.

Doppler ultrasound and Evans blue dilution techniques were applied to investigate the corinfar and finoptin effects on cerebral circulation in 97 patients, and on regional circulation in 40 patients with cerebral ischemia. In patients with severe ischemic brain damage, the vasodilating effect without intracerebral stealing was most pronounced. Cardiodepressant effects were negligible. The authors discuss indications and contraindications to finoptin and corinfar treatment in ischemic brain disorders.

Doppler ultrasound of orbital vessels.

The techniques of doppler ultrasound have been applied to blood vessels within the orbit. The doppler frequency shifts of ultrasonic pulses scattered from blood cells moving within orbital vessels are a measure of velocities rather than the amount of blood flow. The doppler signal from the ophthalmic artery behind the globe is responsive to changes in ocular blood flow. Blood flow can also be detected at the optic nerve head, and from the coats of the eye adjacent to the nerve head. Flow rate in the ophthalmic artery is reduced following retrobulbar anaesthesia. The source of the pulsatile retrograde flow signal which can be detected in some cases of internal carotid stenosis is located in the region of the ophthalmic artery.