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PubMed1997

Role of nitric oxide and tumor necrosis factor on lung injury caused by ischemia/reperfusion of the lower extremities.

PURPOSE: Acute aortic occlusion with subsequent ischemia/reperfusion (I/R) of the lower extremities is known to predispose to lung injury. The pathophysiologic mechanisms of this injury are not clear. In the present study, we studied the role of tumor necrosis factor (TNF) and nitric oxide (NO) in lung injury caused by lower extremity I/R. METHODS: A rat model in which the infrarenal aorta was cross-clamped for 3 hours followed by 1 hour of reperfusion was used. The rats were randomized into five groups: group 1, aorta exposed but not clamped; group 2, aorta clamped for 3 hours, followed by 1 hour of reperfusion; group 3, 1 mg/kg dexamethasone administered before the aorta was clamped; group 4, 25 mg aminoguanidine, a specific inducible NO synthase (iNOS) inhibitor, administered before the aorta was clamped; and group 5, 2 mg/kg TNFbp, a PEG-ylated dimeric form of the high-affinity p55 TNF receptor I (RI), administered before the aorta was clamped. NO concentration in the exhaled gas (ENO) was measured, as an index of NO production by the lung, in 30 minute intervals during I/R. Serial arterial blood samples for TNF assay were obtained during the course of the experiment. At the end of the experiment, the lungs were removed and histologically examined for evidence of injury. RESULTS: ENO in group 2 increased from 0.7 +/- 0.3 ppb at baseline to 54.3 +/- 7.5 ppb at the end of ischemia and remained stable during reperfusion (54.6 +/- 8.5 ppb at the end of reperfusion). ENO production was blocked by aminoguanidine, by dexamethasone, and by TNFbp given before aortic occlusion. Serum TNF in groups 2, 3 and 4 increased rapidly during early ischemia, reaching its peak value 60 minutes after occlusion of the aorta, then gradually declined to baseline levels at the end of ischemia, and remained low during reperfusion. TNFbp decreased serum TNF concentration significantly when it was given before aortic occlusion. Histologic examination of the lungs at the end of the experiment revealed that aminoguanidine, dexamethasone, and TNFbp had a protective effect on the lungs. CONCLUSIONS: Serum TNF increases rapidly during lower extremity ischemia and causes increased production of NO from the lung by upregulating iNOS. Increased NO is associated with more severe lung injury, and iNOS blockade has beneficial effects on the lung. TNF blockade before ischemia decreases NO production by the lung and attenuates lung injury. ENO can be used as an early marker of lung injury caused by lower extremity I/R.

Animals↗
PubMed1997

Upper extremity deep venous thrombosis and its impact on morbidity and mortality rates in a hospital-based population.

PURPOSE: Although much attention has been focused on lower extremity deep venous thrombosis (LEDVT), there is a relative paucity of data regarding the impact of upper extremity deep venous thrombosis (UEDVT) on morbidity and mortality rates. To increase our knowledge with the latter disease, we have reviewed our experience at our institution with 170 patients who had brachial, axillary, and subclavian vein thromboses. METHODS: Over the past 5 years, UEDVT was diagnosed in 170 patients by duplex scanning. The indications for duplex examination were either upper extremity swelling (95%) or as part of the workup for pulmonary embolism (5%). There were 103 women (61%) and 67 men (39%), with ages ranging from 9 to 101 years (mean, 68 +/- 17 years). The diagnosis was made in 152 patients (89%) while they were admitted to the hospital and in 18 patients (11%) in the outpatient clinic. Risk factors included presence of a central venous catheter or pacemaker in 110 patients (65%), malignancy in 63 patients (37%), concomitant LEDVT in 19 patients (11%), and history of LEDVT in 18 patients (11%). Fifty-six patients (33%) had multiple risk factors, whereas 36 patients (21%) had no obvious risk factor. RESULTS: The 1-month and 3-month mortality rates for the entire study group were 16% and 34%, respectively. Patients who had concomitant LEDVT, were 75 years of age or older, and were not treated with anticoagulation medication had a significantly higher 1-month mortality rate. Patients whose diagnoses were made in the outpatient setting were statistically younger and had a lower 3-month mortality rate when compared with the patients whose diagnoses were made as inpatients. Pulmonary embolism was documented by ventilation/perfusion scan in 12 patients (7%). Although no patient in the group in which UEDVT was diagnosed on an outpatient basis was documented to have a pulmonary embolism and 12 patients (8%) in the inpatient group had pulmonary emboli, this difference was not statistically significant. Anticoagulation medication did not totally prevent pulmonary embolism in this review. All patients were followed-up for between 0 to 49 months (mean, 13 +/- 1 months). No swelling of the affected arm was observed in 145 patients (94%); four patients complained of mild intermittent swelling (2%), and seven patients reported significant swelling (4%). CONCLUSIONS: Contrary to previous reports, these data suggest that UEDVT is associated with a low incidence of postthrombotic upper extremity swelling, but a significant incidence of pulmonary embolism and rate of mortality. This review suggests that UEDVT is at least as serious a disease entity as LEDVT and should be managed as aggressively as LEDVT.

APACHE↗
PubMed2001

Stability after laser in situ keratomileusis in moderately and extremely myopic eyes.

OBJECTIVE: To evaluate the stability, mechanism, and degree of regression following laser in situ keratomileusis (LASIK) in cases with moderate to extreme myopia after 2 years of follow-up. SETTING: Single-center clinical trial. METHODS: Fifty-two eyes of 38 patients were enrolled in the study. One year follow-up was available for 47 eyes of 35 patients and 2 year follow-up for 39 eyes of 27 patients. Eyes were divided into 2 groups based on the level of preoperative myopia: Group 1, moderate to high myopia > or =15.0 diopters (D) (range -7.0 to -15.0 D, n = 24); Group 2, extreme myopia >15.0 D (range -15.3 to -25.8 D, n = 15). Laser in situ keratomileusis was performed using the Chiron Automated Corneal Shaper(R) microkeratome and the Summit OmniMed excimer laser. Manifest spherical equivalent, mean central keratometry, and central corneal thickness (CCT) were measured preoperatively and 12 and 24 months postoperatively. RESULTS: Group 1 exhibited a mild myopic shift (mean -0.07 +/- 0.28 D; P >.2) and a mild increase in keratometry (mean 0.05 +/- 0.46 D; P >.6), with an accompanying increase in CCT (mean 7.5 +/- 12.2 microm; (P =.006) at 24 months. Group 2 displayed a significant myopic shift (mean -0.7 +/- 0.7 D; P =.001) and a significant increase in keratometry (mean 0.4 +/- 0.5 D; P =.01), with a mild increase in CCT (mean 2.4 +/- 9.7 microm; P =.35) at 24 months. Corneal ectasia was evident in 1 eye in the extreme myopia group. CONCLUSION: The refractive effect of myopic LASIK up to -15.0 D remained reasonably stable during the second postoperative year. Significant regression of the refractive effect occurred in eyes with higher levels of myopia (>15.0 D), with the risk of progressive ectasia. Extreme caution is recommended when myopic LASIK is performed in eyes with higher levels of myopia.

Adult↗
PubMed1998

Photorefractive keratectomy for astigmatism greater than -2.00 diopters in eyes with low, high, or extreme myopia.

PURPOSE: To assess the efficacy of excimer laser photorefractive astigmatic keratectomy (PARK) in correcting astigmatism of more than -2.00 diopters (D) in eyes with low, high, and extreme myopia. SETTING: Pusan National University Hospital, Pusan, Korea. METHODS: Eighty-five patients (110 eyes) whose spherical error ranged from -3.00 to -13.00 D and cylinder ranged from -2.00 to -5.50 D had PARK with a VISX Twenty-Twenty excimer laser; follow-up was 6 months. All cases of myopic astigmatism were treated using the elliptical method and multizone ablation technique. Eyes were divided into 3 groups: low myopia, less than 6.00 D (n = 47); high myopia, from 6.25 to 10.00 D (n = 43); extreme myopia, over 10.25 D (n = 20). Alpins vector analysis was used to calculate the astigmatic change. RESULTS: By vector analysis, the success rate of astigmatic correction was more predictable in the low and high myopia groups than in the extreme myopia group (P < .05). There was little improvement in astigmatism in the extreme myopia group. CONCLUSION: Using PARK to correct astigmatism greater than -2.00 D in eyes with myopia less than -10.00 D tended to result in undercorrection; astigmatic correction in eyes with myopia over 10.25 D was minimal.

Adult↗
PubMed2000

Lower extremity nerve blocks.

Lower extremity nerve blocks have not become as popular as upper extremity blocks for anesthesia; however, the use of lower extremity nerve blocks will become more widespread, as teaching programs are now providing more regional anesthesia experiences for their trainees so that the anesthesia provider will have the familiarity to use these blocks. To increase the enthusiasm among our surgical colleagues, we must begin to use these blocks for surgery, and if the block must be supplemented with local anesthetic or a light general anesthetic, we must educate them that the block is not a failure but a success, as it will provide analgesia after surgery in a method of multimodal pain control. Lower extremity nerve blocks will become more popular when it is realized that they are an effective way of increasing operating room efficiency. Because the block may be placed in an induction room, there is no induction or emergence in the operating room. Patients may be discharged without the need for pain medications, thus lowering the incidence of nausea postoperatively and decreasing PACU and discharge times.

Humans↗
PubMed2002

Incomplete benefit of antihypertensive therapy on stroke reduction in older hypertensives with abnormal nocturnal blood pressure dipping (extreme-dippers and reverse-dippers).

To determine whether the benefits of antihypertensive treatment vary according to dipper status, 811 asymptomatic elderly Japanese hypertensives underwent 24-h ambulatory blood pressure monitoring. During a mean follow-up period of 41 months, 32 stroke events were observed in patients who remained nonmedicated (n = 385), and in 27 patients in the medicated group (n = 426), indicating a 24% lower rate of stroke as a result of antihypertensive therapy. Patients were divided into a white-coat hypertensive (WCHT) group (ambulatory blood pressure <130/80 mm Hg; n = 236) and a sustained hypertensive (SHT) group (n = 575). Sixty-one percent of SHT and 32% of WCHT patients were being medicated. In the SHT group, the stroke rates were 12.4% in nonmedicated and 7.4% in medicated group (P =.04), whereas in the WCHT group the stroke rates were 2.5% in nonmedicated and 1.3% in medicated group (P = not significant). The SHT were further classified according to their nocturnal systolic blood pressure (BP) decrease, as follows: 97 extreme-dippers with >20% nocturnal systolic BP decrease; 230 dippers with >10% but <20% decrease; 185 nondippers with >0% but <10% decrease; 63 reverse-dippers with <0% decrease. In the dipping groups of SHT, the stroke rates were similar according to medication versus no-medication in extreme-dippers (12% v 13%), and reverse-dippers (23% v 22%), but in nondippers there was a significantly lower rate (by 65%, P =.038) in the medicated (4.4%) than the nonmedicated (13%) groups. In dippers, the stroke rate was also lower in the medicated than the nonmedicated patients (4.7% v 8.8%), a decrease of 47% (P =.217), although the difference was not significant. In conclusion, in older SHT subjects, antihypertensive therapy using clinic BP may be less effective for the groups with extremely abnormal diurnal BP patterns (extreme-dippers and reverse-dippers) than those with relatively normal patterns (dippers and nondippers). Patients with WCHT also showed no benefit.

Aged↗
PubMed2001

Body warmer and upper extremities position affect the accuracy of cutaneous thermometers during anesthesia.

STUDY OBJECTIVE: To evaluate whether axillary skin temperature can accurately reflect distal esophageal temperature. DESIGN: Prospective, randomized study. SETTING: Teaching hospital. PATIENTS: 48 ASA physical status I and II adult patients undergoing abdominal surgery. INTERVENTIONS: Patients received standard general anesthesia. 19 patients had abducted upper extremities and an upper body surface warmer, 19 patients had abducted upper extremities with no upper body surface warmer, and 10 patients had adducted upper extremities with no upper body surface warmer. MEASUREMENTS AND MAIN RESULTS: The temperatures were measured 60 minutes after the induction of general anesthesia. There was no significant difference between axillary skin temperature (36 +/- 1.7) (degrees C) and core temperature (36 +/- 0.7) (degrees C) when the upper body surface warmer was used. There was no difference between axillary skin temperature (35.5 +/- 0.4) (degrees C) and core temperature (35.8 +/- 0.4) (degrees C) when upper extremity was adducted 0 degrees. CONCLUSIONS: At 0 degrees of arm adduction, or at 90 degrees using the upper body, forced-air surface warmer, axillary skin temperature accurately identified the core temperature in patients during general anesthesia.

Anesthesia↗
PubMed1997

Utility of carotid duplex in young adults with lower extremity atherosclerosis: how aggressive should we be in screening young patients?

The purpose of this study was to determine the prevalence and degree of carotid disease in patients with premature lower-extremity atherosclerosis. Seventy-six young men (mean age at onset of symptoms 42+/-0.5 years with premature lower extremity atherosclerosis who underwent complete carotid duplex scans were studied. The mean lowest ankle: brachial index was 0.49+/-0.02. Forty-seven patients (62%) required interventions to treat advanced leg symptoms, and 18 (24%) experienced disease progression during the study period. Carotid duplex scans showed internal carotid occlusions in eight (11%); advanced or critical plaque disease (60-99% diameter loss) in 14 (18%); moderate plaque disease (40-59% diameter loss) in 16 (21%); mild plaque disease (intimal thickening or 1-39% diameter loss) in 18 (24%); and normal carotid arteries in 20 (26%). Comparing the 20 subjects with normal carotid arteries to the S6 with any evidence of disease, there were no differences in age of onset, risk factors, coronary artery disease, mean ankle: brachial index, number of interventions, disease progression, amputation, or death. Fifteen (27%) of the patients with carotid atherosclerosis ultimately developed transient ischemic attack or stroke; 13 of these had advanced carotid stenoses or carotid occlusions. In conclusion, carotid plaque disease is prevalent among patients with premature atherosclerosis of the lower extremity. The presence of carotid atherosclerosis is not related to the degree of lower extremity atherosclerosis, nor to the rate of disease progression. Carotid duplex scans are indicated to screen these young patients for compelling lesions that might warrant prophylactic carotid endarterectomy.

Adult↗
PubMed2002

Radiation protection system for interventional procedures of the upper extremity: evaluation in a phantom model.

PURPOSE: To design a radiation protection system for interventional procedures of the upper extremity and to evaluate the effectiveness of the system. MATERIALS AND METHODS: The radiation protection system consisted of an image intensifier (I-I) hood and x-ray tube cover. The I-I hood encircled the I-I to protect against scattered radiation from the patient's upper extremity and the table. The I-I hood consisted of four components: a device for attaching the hoods, two acrylate hoods with an 0.50-mm Pb equivalent, and a lead curtain hood with a 0.35-mm Pb equivalent. The x-ray tube cover was constructed of lead curtain to protect against backscattering radiation from the catheter table. An extremity phantom was used to measure the scattered radiation around the angiographic apparatus. The scattering dose rates were measured with an ionization dosimeter with and without a radiation protection system. The heights of the measuring points from the floor were 50 cm (operator's lower limbs), 100 cm (operator's abdomen), and 150 cm (operator's head/neck). RESULTS: The dose rates were reduced most with the combination of the I-I hood and the x-ray tube cover. The x-ray tube cover was effective in reducing scattering when it was set close to the table and the phantom. The maximum percentage decreases in dose rates by the radiation protection system were 99% at 50 cm, 73% at 100 cm, and 100% at 150 cm. Therefore, at 50 cm and 150 cm, the high-dose-rate area around the angiographic apparatus was reduced almost completely by the radiation protection system. CONCLUSION: The radiation protection system for interventional procedures of the upper extremity was effective in reducing scattered radiation around the angiographic apparatus.

Angiography↗
PubMedDate not supplied

Lower extremity amputations in diabetic Mexican American elders: incidence, prevalence and correlates.

This study was designed to determine the incidence and prevalence of amputations in diabetic Mexican American elders and to identify correlates of lower extremity amputations. Data for this study came from baseline and two follow-up interviews of the Hispanic Established Population for the Epidemiological Study of the Elderly (EPESE) conducted in five southwestern states (Texas, California, New Mexico, Colorado and Arizona) in 1993-1994. Of the 3050 subjects aged 65 and older, 690 reported diabetes, and from these, 60 (8%) reported having at least one lower extremity amputation. Losing a leg was the most common type of amputation (53%). Twelve percent of respondents reported a new amputation and 40% of amputees reported a second amputation during follow-up. Mortality among amputees was 46% during a 5-year follow-up. Multiple logistic regression analysis showed that being male and having eye problems, hip fracture and diabetes for 10 or more years were significantly associated with lower extremity amputations at baseline, whereas obesity, stroke and 10 or more years with diabetes were significantly associated with new amputations at 5-year follow-up. Gender and disease history were associated with lower extremity amputations at baseline and follow-up. These variables may be useful in developing patient education and intervention programs.

Aged↗
PubMed1996

The quality of life of the limb-threatened patient after lower-extremity revascularization.

There is limited research evaluating the quality of life after lower-extremity revascularization surgery. Nursing is concerned not only with survival and decreased morbidity, but also with the whole patient. An impact analysis survey was used to investigate whether patients perceived their quality of life to be improved after they underwent lower-extremity revascularization surgery. The Medical Outcomes Study-36 (MOS-36, 1990) survey was used to help us assess the patients' overall perceptions after lower-extremity revascularization surgery. The MOS-36 has a scale that measures life health concepts and a health-transition item. The purpose of this study was to determine the effect of lower-extremity revascularization on the quality of life in limb-threatened patients. The study examined quality of life as an outcome after revascularization.

Aged↗
PubMedDate not supplied

Lower extremity manifestations of Vibrio vulnificus infection.

Vibrio vulnificus is a potentially lethal marine bacterium that has not been previously described in podiatric literature. A review of the microorganism's characteristics, susceptible patient population, and lower extremity manifestations of infection is presented. V. vulnificus is found as part of the normal flora of the Gulf of Mexico, Atlantic, and Pacific coastal waters and is often isolated from the filter feeding shellfish of these regions. Its pathogenicity is generally reserved for the immunocompromised host, and is specifically related to disease states which exhibit high serum iron levels. V. vulnificus infections present in two distinct clinical syndromes: primary sepsis secondary to raw oyster ingestion, or localized infection from wound exposure to V. vulnificus-inhabited salt water. Both syndromes demonstrate characteristic skin lesions of the trunk and extremities that present as hemorrhagic bullae and progress to necrotic ulcerations. Although V. vulnificus infection is rare, its extreme virulence in patients suffering from a chronic disease process and its manifestation of characteristic lower-extremity lesions require the podiatric physician to be able to recognize and treat such a condition.

Combined Modality Therapy↗
PubMedDate not supplied

The lower extremity manifestations of Prader-Willi syndrome.

A case of a rare genetic disorder with typical lower extremity and gait alterations as the chief concern was presented. A description of the characteristic lower extremity and gait manifestations of this syndrome has been developed. The major and minor diagnostic criteria, which have been published to identify this syndrome, were reviewed with respect to this case. The practitioner who has the opportunity to evaluate patients for gait and lower extremity complaints should be aware of these correlations to aid in timely diagnosis of this condition. Management of compensations from these lower extremity pathologies may improve stability and prognosis for normal function. Management may also include surgical correlation of deformities found in association with this syndrome.

Child↗
PubMed2004

Infections of the upper extremity in hospitalized diabetic patients: A prospective study.

OBJECTIVES: To study the clinical characteristics of a group of patients with diabetes and established upper extremity infections and to determine the causative factors of hand infections. METHODS: Prospective study of diabetic patients referred in to our service with infections of the upper extremity from January 1992 to December 2001. RESULTS: Twenty-six diabetic patients with an infection of the upper extremity were studied (17 F, 9 M). The admission rate equalled 0.7%. Twenty-one patients (80.8%) presented a Type 2 diabetes and 5 a Type 1 diabetes (19.2%). The diagnosis age of diabetes was 44.6 +/- 13.8 Years (range: 16-62). The average age at the occurrence of the lesion was 52.5 +/- 15.1 Years (range: 21-73). The average duration of diabetes was 8.3 +/- 5.9 Years (range: 0-22). Diabetes was, in all the cases, poorly controlled because of an inadequate hypoglycaemic treatment and/or bad compliance. The patients had a high prevalence of peripheral neuropathy (n=17; 65.4%). The delays in presentation to the doctor and those related to hospitalization were respectively 9.1 +/- 10.0 days (n=23) and 16.8 +/- 12.1 days. The hospitalization length reached 33.6 +/- 22.6 days (range: 7-93). The final results, 6 Months after hospitalization, were as follows: the death rate reached 19.2% (n=5); 23.1% of the patients (n=6) had a minor amputation; for 53.8% of the patients (n=14), the lesions healed without any amputation. One patient left hospital against medical advice. Eleven out of 20 patients (55%), amputated or not, were left with deformities and a subjective dysfunction of the affected limb. CONCLUSION: Infections of the upper extremity in diabetic patients constitute an uncommon but serious complication. They seem to be more frequent in housewives. They result in a high morbIdity. Prevention of these infections should be based on patients' education (compliance with diabetes treatment, hand care, prompt visit to the doctor) and General Practitioners' training for an adequate treatment and/or a rapId patient referral to hospital.

Algeria↗
PubMedDate not supplied

Hip spine syndrome: management of coexisting radiculopathy and arthritis of the lower extremity.

BACKGROUND CONTEXT: Significant lumbar spinal stenosis and lower extremity arthritis may coexist in the elderly. This combination of lumbar stenosis with radiculopathy and lower extremity arthritis may lead to diagnostic uncertainty. PURPOSE: To describe the findings of hip spine syndrome, a constellation of symptoms with extensive overlap of radiculopathy and lower extremity arthritis. CONCLUSIONS: Evaluation of the patient with lower extremity pain in consideration for total joint arthroplasty should include functional inquiry of the spinal nerves. Diagnostic tests and injections may allow an informative weighting of the patient's symptoms, leading to a better understanding of the patient's pain syndrome. There is a group of patients who have a total hip arthroplasty and then develop or may continue to have pain of groin and buttock, secondary to sciatica of lumbar spinal stenosis. For the patient undergoing total hip arthroplasty with asymptomatic spinal stenosis, there may be increased neurological risk at surgery, related to the stenosis. The patient with both conditions may require surgical decompression of the lumbar stenosis as well as joint arthroplasty of the arthritic joint.

Arthritis↗
PubMed2003

Thermal biofeedback and lower extremity blood flow in adults with diabetes: is neuropathy a limiting factor?

Thermal biofeedback may be a useful adjunctive technique for enhancing cutaneous blood flow in patients with lower-extremity vascular complications of diabetes. However, autonomic, sensory, and/or motor neuropathies may impair vasomotion and limit the ability to alter blood flow and achieve significant foot warming with thermal biofeedback. We examined nerve function associated with four common types of diabetic neuropathy (sympathetic-autonomic, vagal-autonomic, sensory, and motor), hypothesizing that both sympathetic-autonomic and sensory neuropathies would limit the acquisition of biofeedback-mediated foot warming. Twenty-four participants with diabetes mellitus (19 with type II and 5 with type I) received a nerve conduction study and neurological evaluation of the upper and lower extremities. Hand temperature, foot temperature, and electrodermal gradient at the toes were monitored across six thermal biofeedback sessions. Participants were able to significantly raise p < .01) foot temperatures across sessions, an average of 2.2 degrees F. Consistent with our hypotheses, 41% of the variance in foot warming was explained by lower-extremity sympathetic-autonomic and sensory nerve function tests. This study demonstrated that a general diabetic population, including patients with mild-to-moderate neuropathy, can increase skin perfusion with thermal biofeedback. As hypothesized, lower-extremity sympathetic-autonomic and sensory neuropathies interfered with foot warming.

Adolescent↗
PubMed1994

Salience, set size, and illusory correlation: making moderate assumptions about extreme targets.

Salient persons and objects are often evaluated more extremely than other targets. Our study integrated research on illusory correlation, set size, and salience and explored when and why these salience effects occur. The results indicate that the tendency to evaluate salient targets more extremely is attenuated when the number of targets present in the judgmental context is low or when considerable time is available to process the relevant evidence. These illusory correlations are also less likely to form when the descriptions of the targets are moderate as opposed to extreme. The findings reveal that people tend to learn much about salient targets, but they are often left to making assumptions about nonsalient targets. An illusory correlation often forms because the salient target is recognized to have extreme qualities, whereas nonsalient targets are erroneously assumed to have more moderate qualities.

Attention↗
PubMed2005

A frequency comb in the extreme ultraviolet.

Since 1998, the interaction of precision spectroscopy and ultrafast laser science has led to several notable accomplishments. Femtosecond laser optical frequency 'combs' (evenly spaced spectral lines) have revolutionized the measurement of optical frequencies and enabled optical atomic clocks. The same comb techniques have been used to control the waveform of ultrafast laser pulses, which permitted the generation of single attosecond pulses, and have been used in a recently demonstrated 'oscilloscope' for light waves. Here we demonstrate intra-cavity high harmonic generation in the extreme ultraviolet, which promises to lead to another joint frontier of precision spectroscopy and ultrafast science. We have generated coherent extreme ultraviolet radiation at a repetition frequency of more than 100 MHz, a 1,000-fold improvement over previous experiments. At such a repetition rate, the mode spacing of the frequency comb, which is expected to survive the high harmonic generation process, is large enough for high resolution spectroscopy. Additionally, there may be many other applications of such a quasi-continuous compact and coherent extreme ultraviolet source, including extreme ultraviolet holography, microscopy, nanolithography and X-ray atomic clocks.

Journal Article↗