Electrocardiographic Electrodes Research Articles

Electrocardiographic Motion Artifact Versus Electrode Impedance

We degraded electrocardiographic electrodes by exposing them to air for four days and evaluated them on 12 subjects. After application, we recorded the electrocardiogram (including motion artifact), missed QRS detections and electrode impedance during 5 min of arm and body movements. Missed QRS detections increased with electrode impedance but correlation was poor. Increased electrode impedance was not a reliable predictor of a poor electrode and the need to replace it.

Captopril blocks the cardiac actions of centrally administered angiotensin I in the trout Oncorhynchus mykiss

The present study was performed in order to gain new insights into the existence of a brain renin–angiotensin system (RAS) in teleost fish. For this purpose, we investigated the effects of centrally administered angiotensin (ANG) I ([Asn 1,Val 5,Asn 9]ANG I) and ANG II ([Asn 1,Val 5]ANG II) on heart rate (HR) and heart rate variability (HRV) in the unanesthetized trout. The animals were studied before and after treatment with captopril, an angiotensin-converting enzyme (ACE) inhibitor. Trout were equipped with two subcutaneous electrocardiographic electrodes and with an intracerebroventricular (i.c.v.) cannula inserted within the third ventricle of the brain. The i.c.v. injection of vehicle had no effect on the recorded parameters. The i.c.v. injections of ANG I and ANG II at doses of 5 and 50 pmol had a marked effect on HR and HRV. At a dose of 50 pmol, ANG I and ANG II produced a progressive and significant increase in HR (+36% and+45%, respectively) but elicited a profound decrease in HRV (−88% and−92%, respectively). I.c.v. injection of captopril (10 μg) had no effect on HR or HRV. However, this ACE inhibitor prevented the tachycardia and abolished the decrease in HRV mediated by 50 pmol of ANG I. In contrast, captopril had no effect upon the cardiac actions of 50 pmol of ANG II. These results give the first support for the existence of functional important ACE-like activity in the brain of a teleost fish and suggest that the brain RAS in this class of vertebrate may be involved in the control of cardiac chronotropic activity.

Induction of bradycardia in trout by centrally administered corticotropin-releasing-hormone (CRH)

The cardiovascular effects of centrally and peripherally administered synthetic salmon corticotropin-releasing-hormone (CRH), a member of a family of stress-related neuropeptides, were investigated in the unanesthetized trout, Oncorhynchus mykiss. In group 1, trout bearing a cannula in the dorsal aorta, neither intracerebroventricular (i.c.v.) nor intra-arterial (i.a.) injections of CRH produced any significant change in mean heart rate (HR) and mean dorsal aortic blood pressure. These results stand in contrast to the previously reported hypertensive effects of i.a. and i.c.v. injections of trout urotensin-I. In group 2, non-cannulated trout bearing two subcutaneous electrocardiographic electrodes, conditions that are considered to be less stressful to the animals, the baseline level of HR was significantly reduced compared to the corresponding value for cannulated trout. In these trout, no significant change occurred in the HR after i.c.v. administration of 1 pmol of CRH. However, i.c.v. injection of 5 pmol of CRH caused a 12% ( P<0.01) decrease in HR during the 20–25 min post-injection period. In addition, the heart rate variability (HRV), a marker of vagal input to the heart, was increased by 120%. The CRH antagonist, CRH-(9–41)-peptide alone had no effect on HR or HRV but blocked CRH-induced bradycardia. In the non-cannulated trout, i.c.v. injection of trout urotensin-I (5 pmol) produced no significant change in HR and HRV. In contrast, i.c.v. administration of angiotensin II (5 pmol) elicited a highly significant 33% ( P<0.001) increase in the mean HR as well as inducing a marked (64%) reduction in HRV. Our results suggest that picomolar doses of CRH act centrally to evoke a bradycardia by a probable mechanism that involves enhancement of the parasympathetic drive to the heart.

An unanticipated effect of meditation on cardiovascular pharmacology and physiology

T late George Harrison helped to usher in a fascination with diverse aspects of Indian culture, from sitar music to meditation. Thousands of young people embraced meditation in search of relaxation, enlightenment, or altered states of consciousness. Numerous studies examined various aspects of the physiology of meditation, and some investigators suggested that meditation was a useful adjunct in treating many medical problems such as hypertension. Meditation has been observed to decrease adrenergic receptor sensitivity and to increase cardiac parasympathetic activity. In recent years the “zeitgeist” has shifted and interest in the medical aspects of meditation has diminished. We report here a serendipitous observation of the effects of meditation to counter the effects of pharmacologic doses of the adrenergic agonist isoproterenol. As part of our institutional review board-approved studies of sympathetic nervous system regulation in hypertension, for many years we have administered intravenous isoproterenol in incremental doses as a way of gauging in vivo -adrenergic receptor sensitivity. This venerable tool in the cardiovascular physiology armamentarium has been widely used; the chronotropic (or heart rate-increasing) qualities of isoproterenol are well known. • • • A 36-year-old healthy normotensive white woman was studied using a standard isoproterenol challenge test. An intravenous catheter was placed in an antecubital vein the night before the study. On the day of study, she consumed a light non–caffeine-containing breakfast and lunch. About 1 hour after lunch, electrocardiographic electrodes were attached in the lead II configuration and she rested quietly in a supine position for 20 minutes. Isoproterenol was infused intravenously by bolus injection every 3.5 minutes at the following doses: 0, 0.1, 0.5, 1.0, 2.0, and 4.0 g. Heart rate was measured electrocardiographically 60 seconds after each bolus injection. To our surprise her heart rate diminished—plummeted even—after receiving the 0.5g dose of isoproterenol. When the test was concluded, we asked if she had noticed any unusual subjective sensations in response to the isoproterenol. Had she been feeling nauseous, dizzy, faint? She replied that she had felt fine during the infusion studies but did not really recall them very well because she had started meditating shortly after the infusions began. She indicated that for many years she had meditated as a way of quieting her mind. She did not follow any particular school of meditation but found that she could readily “enter another realm” while meditating. She reported that she routinely meditated 20 to 30 minutes at a time once a day and that her meditation involved focusing on her breathing. She noted parenthetically that her meditation was so deep that she needed an alarm clock to rouse her from meditation, lest she meditate for hours on end and miss work. Because we suspected that the isoproterenol studies were invalidated because of her meditation, we asked her to return to the hospital about 2 weeks later to repeat the isoproterenol studies—this time with the instructions to keep her eyes open and not to meditate during infusion. Figure 1 is a graph of her heart rate response on the initial occasion while meditating and on the second occasion while not meditating; for comparison purposes the figure also shows the responses observed in 93 other women studied over the years in our laboratory. In the face of a dose increment from 0 to 4.0 g, the expected response is an increase in heart rate by 21 beats/min (Figure 1). However, during meditation, her heart rate actually decreased by 17 beats/ min. When she was instructed not to meditate, her heart rate response was entirely consistent with the typical response observed in our laboratory. • • • The higher central command associated with her meditation was apparently able to override a powerful adrenergic stimulus provided by the pharmacologic infusion. Although we have no data on the precise mechanism of this unusual phenomenon, a reasonable speculation would be sizeable vagal activation. Had we obtained the electrocardiogram digitally, it would have been possible to examine vagal activity explicitly as inferred from heart rate variability. Unfortunately, the heart rate was obtained from transient electrocardiographic rhythm strips, and analysis of heart rate variability was therefore not feasible.

Characteristics of maternal heart rate patterns during labor and delivery

OBJECTIVE: To find patterns characteristic of maternal heart rates recorded by an electronic fetal monitor and compare them with concomitant fetal heart rate (FHR) patterns. METHODS: Maternal heart rates and FHRs during active labor and delivery were simultaneously recorded in 26 parturients with singleton pregnancies in vertex presentation. The FHRs were obtained by an external ultrasound transducer or via a spiral scalp electrode and maternal heart rates by a triple-wire cable with electrocardiographic electrodes attached to the chest. Representative tracings of 30–60 minutes duration were selected from all stages of labor and after delivery of the placenta. Quantitative assessments were carried out under guidelines from the National Institute of Child Health and Human Development after blinding the source of these tracings. Patterns were compared by appropriate statistical analyses. RESULTS: Baseline maternal heart rates were significantly lower and their variability significantly higher than FHRs during all stages of labor. Maternal heart rates showed no decelerations; the proportion of tracings with accelerations increased as labor advanced, most of them coinciding with uterine contractions or bearing down efforts. The FHRs had both decelerations and accelerations. However, tracings with only accelerations (and no decelerations) were observed in decreasing frequency as labor advanced. Maternal accelerations had higher amplitudes and longer durations than fetal accelerations, especially in the second stage of labor. CONCLUSION: Maternal heart rate patterns recorded by electronic fetal monitors closely resemble fetal patterns. Baseline “fetal bradycardia,” the absence of decelerations in the second stage of labor, and marked accelerations coinciding with uterine contractions may suggest a maternal heart rate rather than an FHR recording.

Electrocardiographic Electrodes Provide the Same Results as Expensive Special Sensors in the Routine Monitoring of Anesthetic Depth

Electrocardiographic Electrodes Provide the Same Results as Expensive Special Sensors in the Routine Monitoring of Anesthetic Depth

A novel method to detect electrocardiographic electrode interchanges

Electrode misplacement and interchange errors are known problems when recording the 12‑lead electrocardiogram (ECG). Automatic detection of these errors could play an important role for improving clinical decision making and outcomes in cardiac care. The objectives of this systematic review and meta-analysis is to 1) study the impact of electrode misplacement on ECG signals and ECG interpretation, 2) to determine the most challenging electrode misplacements to detect using machine learning (ML), 3) to analyse the ML performance of algorithms that detect electrode misplacement or interchange according to sensitivity and specificity and 4) to identify the most commonly used ML technique for detecting electrode misplacement/interchange. This review analysed the current literature regarding electrode misplacement/interchange recognition accuracy using machine learning techniques.A search of three online databases including IEEE, PubMed and ScienceDirect identified 228 articles, while 3 articles were included from additional sources from co-authors. According to the eligibility criteria, 14 articles were selected. The selected articles were considered for qualitative analysis and meta-analysis.The articles showed the effect of lead interchange on ECG morphology and as a consequence on patient diagnoses. Statistical analysis of the included articles found that machine learning performance is high in detecting electrode misplacement/interchange except left arm/left leg interchange.This review emphasises the importance of detecting electrode misplacement detection in ECG diagnosis and the effects on decision making. Machine learning shows promise in detecting lead misplacement/interchange and highlights an opportunity for developing and operationalising deep learning algorithms such as convolutional neural network (CNN) to detect electrode misplacement/interchange.

Anetoderma of prematurity in association with electrocardiographic electrodes

Anetoderma in premature infants is an uncommon lesion that may be associated with the use of various types of monitoring leads. In 2 infants multiple papules of anetoderma occurred on the forehead in association with the use of gel electrocardiographic electrodes. It is postulated that the cause of these papules was a local hypoxemia caused by pressure from the electrodes. Growth-restricted infants may be particularly predisposed to iatrogenic anetoderma. (J Am Acad Dermatol 1999;41:478-81.)

Comparison of Two Techniques for Attaching Electrocardiographic Electrodes to Psittacines

Casares, M., Enders, F. and Montoya, J.A. 1999. Comparison of two techniques for attaching electrocardiographic electrodes to psittacines. J. Appl. Anim. Res., 16: 59–64. An atraumatic technique for attaching electrocardiographic electrodes to psittacines was evaluated in 23 parrots. Technique of using paper clips in place of hypodermic needles as electrodes was found more useful.

Cardiac MR imaging: a guide for the beginner.

The complex motion of the heart during contraction is a serious challenge to the diagnostic radiologist and to the capabilities of the magnetic resonance (MR) imaging unit itself, but electrocardiographic (ECG) gating "stops" motion and thus allows acquisition of diagnostic-quality images. Attention to placement of chest-wall ECG electrodes and the course of ECG leads from the patient will maximize the quality of the gating signal and result in better-quality images. Before commencing the MR imaging examination, the clinical questions for the examination must be identified so that a clinical protocol can be applied to acquire relevant morphologic and physiologic data. In addition to the standard orthogonal views (axial, coronal, and sagittal), oblique and complex sections parallel and orthogonal to intrinsic cardiac axes may be necessary to portray the relevant anatomy to best advantage. Construction of these views requires an understanding of basic normal and pathologic cardiac anatomy. If care is taken in the planning and execution of the MR imaging examination, the radiologist will be able to exploit this exciting technology to its full noninvasive potential.

Electrogastrographic impact of multi-site functional gastric electrical stimulation

Microprocessor-controlled multi-site functional gastric electrical stimulation using synchronized higher frequency (above 25 Hz) bipolar voltages has been suggested as a possible new avenue towards efficient artificial control of gastric motility. However, the effect of this sequential stimulation on gastric electrical activity is unknown. Because of the substantial strength of the invoked sequential contractions, using implanted electrodes to assess gastric electrical activity (GEA) in experimental animals is difficult, if not impossible. Electrogastrography (EGG), the non-invasively obtained recording of GEA, provides an excellent opportunity to study the changes associated with the multi-site functional stimulation. In this study, we investigated 4 unconscious dogs with 4 circumferential sets of subserosally-implanted stimulating electrodes and 4 force transducers attached close to each stimulating electrode set at operation. The abdominal cavity of each dog was closed after the electrode implantations and 3 standard neonatal electrocardiographic electrodes were attached overlying the abdominal projection of the gastric axis. Twochannel EGG recordings were obtained for 1/2 h before any electrical stimulation and during 1/2 h of intensive sequential stimulation. Significant changes were observed in the EGG pattern during stimulation. These changes were quantified and compared to the basal recordings. Our findings indicate that the interrelation between spectral changes in cutaneous EGG and mechanical activity of the stomach could be far more complex than previously speculated.

Test for the Concentration of Electrolytes in Cystic Fibrosis of the Pancreas Utilizing Pilocarpine by Iontophoresis, by Lewis E. Gibson and Robert E. Cooke,Pediatrics; 1959;24:545–549

Aim. To develop a method for stimulating sweating that is rapid, painless, and avoids the risk of heat stress.Background. Since the discovery that there is a high concentration of sodium and chloride in the sweat of patients with cystic fibrosis of the pancreas in 1953, the sweat test has been performed by placing the patient's body in a plastic bag with or without hot water bottles to stimulate sweating. This method is unsatisfactory because of complications such as hyperpyrexia and heat stroke. Direct injection of a cholinergic agent intradermally is painful and therefore not practical.Methods. A rheostat with a milliampere meter was constructed at a cost of ∼$7 that allowed the iontophoresis of pilocarpine into the skin using negative and positive (2-cm diameter) electrocardiography electrodes. The positive electrode was placed on the flexor surface of the arm over a filter paper soaked in 0.2 mL of 0.2% pilocarpine nitrate. Current (0.2 mA) was applied for 5 minutes and then sweat was collected onto a preweighed filter paper for 30 minutes. Sweat chloride was determined by a polarographic method. Sweat tests were performed on 25 patients with cystic fibrosis (CF), 17 asymptomatic relatives and 27 control patients. Patients with CF had sweat chloride concentration &amp;gt;80 mEq/L; relatives, 32.5 mEq/L (highest 57 mEq/L); and control subjects, 21.1 mEq/L (highest 60 mEq/L).Conclusions. The iontophoresis of pilocarpine into the skin is a rapid, painless, safe, and reliable method for stimulating sweating and facilitating the determination of sweat chloride concentration.

Adaptation of extrapulmonary responses to ozone exposure in conscious rats.

The adaptation of cardiovascular and thermoregulatory responses to ozone (O3) was examined by repeated exposure of electrocardiographic (ECG) electrode- and thermistor sensor-implanted rats to O3 for 4 consecutive days (8 hrs/day). Circadian rhythms of heart rate (HR) and abdominal core temperature (Tco) were disrupted on the first and second O3 exposure days in a concentration dependent manner. The 8-hr and 12-hr averaged values of HR and Tco during the exposure period and the dark post-exposure period, respectively, decreased significantly on the first and second exposure days. The decreased HR and Tco recovered to respective control values after small but significant rebound increases on the third and fourth days of O3 exposure. The adaptation of the extrapulmonary responses to O3 exposure was discussed in light of the previously reported time periods required to abolish the spontaneous breathing, biochemical, cellular, and morphological responses to O3.

Body position effects on the ECG: Implication for ischemia monitoring

Rotation of the heart in relation to surface electrocardiographic (ECG) electrodes when a patient turns to one side has been reported to cause ST-segment shifts, triggering false alarms with continuous ST-segment monitoring. We prospectively analyzed ST-segment and QRS complex changes in both standard and derived ECGs in 40 subjects (18 with heart disease and 22 healthy) in supine, right- and left-lying positions. Of the 40 subjects, 6 (4 cardiac, 2 healthy) developed positional ST deviations of 1 mm or more on the standard ECG. In the derived method, five of the same six subjects showed ST-segment deviation of which most occurred in the left-lying position. Positional ST changes were most frequent for males and for cardiac patients (33%). Changes in QRS complex morphology were common on the standard (28 of 40, 70%) and less frequent on the derived ECGs (17 of 40, 43%), occurring in both healthy and cardiac subjects. QRS axis changes occurred only on the standard ECG. It was concluded that (1) right and left side-lying positions frequently induce clinically significant ECG changes; (2) positional ST-segment deviation is less frequent than previously reported and is most likely to occur in males with cardiac disease; and (3) the derived method is less prone to positional QRS changes than the standard ECG.

A home electrocardiography and blood pressure telemonitoring system.

A home electrocardiography (ECG) and blood pressure telemonitoring system for cardiac patients was installed in the Macau region. The monitoring centre was established in the emergency unit at the Government Hospital of Macau. The first users were 10 cardiovascular patients selected by a physician. The average age of these users was 61 years (range 30-78). The results of a three-month trial showed that the system was easy to operate and technically reliable. It was found to be helpful for cardiac patients. The most significant problem during the trial was electrical noise from the ECG electrodes.

Age-related changes in ventilatory and heart rate responses to acute ozone exposure in the conscious rat.

To evaluate the effect of age on toxicant-induced pulmonary and extrapulmonary changes, we examined the effect of inhalation exposure to oxone (O3) on the ventilatory and heart rate (HR) responses in 4-6 and 20-22-month-old male rats. The rats, chronically implanted with an electrocardiographic (ECG) electrodes, were placed in a head-out plethysmograph for continuous ventilatory measurements of tidal volume and breathing frequency. Simultaneous measurements of HR were also obtained. A 6-hr exposure of each rat to filtered air was followed 2 days later by a 5-hr exposure to 0.1 ppm O3, 5 days later by a 5-hr exposure to 0.3 ppm O3 and 10 days later by a 5-hr exposure to 0.5 ppm O3. Each of the O3 exposures was preceded by a 1-hr exposure to filtered air. Transient rapid shallow breathing with slightly increased HR appeared 1-2 min after the start of O3 exposure. It was suggested on the basis of the electroencephalographic (EEG) activity of the olfactory bulb that this transient response was mediated through olfactory sensation. Persistent rapid shallow breathing with a progressive decrease in HR occurred with a latent period of 1-2 hr. The last 90-min averaged values for relative minute ventilation tended to decrease with the increase in the level of exposure to O3 and these values for young rats were significantly lower than those for old rats. An exposure of young rats to 0.1 ppm O3 for shorter than 5 hr significantly decreased the tidal volume and HR and increased breathing frequency, but no significant changes were observed in old rats. There were no differences between young and old rats in non-observable-adverse-effect-levels (NOAELs) for the O3-induced persistent ventilatory and HR responses, when the NOAELs were determined by exposure to 0.3 and 0.5 ppm O3. The present results, as well as the reported decrease in body temperature and blood pressure, suggested that the age-related changes in patterns and magnitude of the persistent rapid shallow breathing with a progressive decrease in HR are mediated through some age-related defense mechanism acting against O3 inhalation. The validity of the occupational exposure limit for O3 in workplaces was discussed in the light of the present findings.

Effect of precordial electrocardiographic electrode placement on ST-segment measurement during exercise.

Research protocols often utilize serial exercise testing to examine the efficacy of anti-ischemic therapies. These tests, however, are prone to multiple sources of bias. This investigation sought to determine the influence of varying precordial electrocardiographic (ECG) electrode placement on the detection of exercise-induced ST-segment shifts. Fifteen coronary artery disease patients with abnormal exercise tests were studied. Based on the previous exercise test, the precordial electrode position exhibiting the greatest ST-segment shift was selected as the reference electrode. Four additional electrodes were placed around this reference electrode and exercise testing was performed. ECG strips were recorded every minute. The time-to-onset and -offset of ischemic-type ST-segment depression was recorded. ST-segment depression was recorded during exercise from the reference electrode in 12 of 15 patients. Ischemic-type ST-depression was also recorded in each of these 12 patients with the surrounding electrodes; however, the time-to-onset detected by all four surrounding electrodes concurred in only 5 of 12 (42%) patients. The time-to-offset of the ST-segment depression concurred in 9 of 12 (75%) patients. Serial ECGs recorded from similar but not exactly the same precordial ECG electrode position should yield similar results for the detection of ischemia, but time-to-onset or -offset of ischemia may differ by 60 s or more. Small changes in the time-to-onset and -offset of ischemia should not be considered reliable indicators of anti-ischemia efficacy.

Marihuana smoking increases plasma cocaine levels and subjective reports of euphoria in male volunteers

The reasons why individuals use this combination are not entirely clear, however, it has been speculated that marihuana may potentiate cocaine's subjective effects. Five male recreational drug users provided informed consent and volunteered to participate in this study. Each subject participated on 3 different days, separated by at least 1 week. Subjects sat in an isolated chamber and were prepared with electrocardiographic (ECG) electrodes for heart rate monitoring and an IV catheter for blood withdrawal. After adapting to the experimental chamber, they smoked a marihuana cigarette containing either 0.004% (placebo), 1.24%, or 2.64% Δ 9-tetrahydrocannabinol (THC). Thirty minutes later they received an intranasal dose of 0.9 mg/kg cocaine. On subsequent visits, the marihuana dose was varied on a random basis. Subjects continuously reported changes in their mood state via an instrumental joystick device and filled out visual analog scales. Marihuana-induced tachycardia was increased even more after cocaine. The duration of all marihuana- and cocaine-related positive subjective effects was unchanged when both drugs were given, but marihuana pretreatment significantly reduced the latency to cocaine effects, from 1.87 to 0.53 min, and decreased the duration of dysphoric or bad effects, from 2.1 to 0.5 min. Peak plasma cocaine levels were 122.8 ± 26.6 ng/ml after placebo marihuana, but pretreatment with the high-dose marihuana resulted in a significant increase in peak cocaine levels (233.8 ± 19.2 ng/ml) and the apparent bioavailability as determined by area under the curve (AUC) analysis. We conclude that marihuana-induced vasodilation of the nasal mucosa attenuates the vasoconstrictive effects of cocaine and thus increases its absorption.

Electrical stunning by direct brain stimulation in pigs

The effects of electrical stunning of slaughter pigs by electrodes shot into the brain, on sensibility and on the incidence of haemorrhages in the shoulder postmortem, were studied. To determine the efficiency of this method 37 slaughter pigs were equipped with EEG (electroencephalograph) and ECG (electrocardiograph) electrodes and stunned twice via the EEG electrodes. In the first experiment the pigs were stunned with 25 V and in the second with 25 V followed by a relaxation current. The day after slaughter the shoulders were scored for haemorrhages. Under more practical conditions three groups of 10 pigs each were electrically stunned via electrodes shot into the brain using 25, 50 or 75 V, followed by a relaxation current. The day after stunning the shoulders were scored for haemorrhages. The pigs did not react to shooting electrodes frontally into the head. After stunning all animals showed a general epileptiform seizure. However, after the second stun the tonic and clonic muscle cramps were impaired. The heart rate increased significantly ( P < 0·01) after stunning, and extra systolae and irregular heart rates were observed. In the shoulders of 27% of the carcasses no haemorrhages were found and in the remainder only minor haemorrhages were seen. Under practical conditions a voltage of 87(± 2) V and a current of 511(±20) mA seemed to be necessary for an effective stun. When lower voltages were applied fewer carcasses with shoulder haemorrhages were found. It may be concluded from these experiments that 25 V (∼134 mA; 150 Hz) is sufficient for effective stunning of slaughter pigs when electrodes are in direct contact with the brain. But as the optimum position of the electrodes may not be reached under practical conditions a voltage of approximately 90 V (∼550 mA; 150 Hz) is recommended. After this stunning method only a few haemorrhages were observed in the shoulders.

Anaesthesia: cheap at twice the price?

We questioned 50 anaesthetic staff about the costs of consumables used in routine anaesthetic practice. By means of a questionnaire staff were asked for estimates of the cost of 28 drugs, fluids and disposables. The responses were more accurate than in previous surveys; 47% of all the estimated costs were within 50% of the actual costs and 75% were within 100%. The costs of relatively expensive items such as blood, laryngeal mask airways, enflurane and isoflurane were consistently underestimated whereas cheaper items such as disposable syringes and electrocardiograph electrodes were consistently overestimated. Using 'state of the art' consumables, an hour-long anaesthetic in 1992 cost 14.02 pounds compared with 1.24 pounds in 1959. However, allowing for inflation, the cost today is actually equivalent to the cost in 1959. Since 1980 there has been no consistent pattern in drug prices, with some prices remaining the same, others falling and some increasing; all are, however, cheaper in real terms. It is possible to make substantial savings by using the more expensive drugs judiciously and by encouraging the use of low-flow, closed-circuit anaesthetic systems.