Monitorización del nervio laríngeo recurrente mediante tubo orotraqueal electromiográfico en cirugía de tiroides y paratiroides. Consideraciones anestésicas / Monitoring of recurrent laryngeal nerve injury using an electromyographic endotracheal tube in thyroid and parathyroid surgery. Anesthetic aspects

La lesión del nervio laríngeo recurrente es una de las principales complicaciones de la cirugía de tiroides y paratiroides. Cuando esta lesión es bilateral, se produce una obstrucción aguda de la vía aérea con compromiso vital para el paciente. Con la identificación visual intraoperatoria se consigue preservar la integridad nerviosa más frecuentemente que si no se identifica el nervio. Para ayudar a identificarlo, se puede monitorizar el nervio laríngeo recurrente utilizando un tubo endotraqueal electromiográfico. En estos casos resulta fundamental el papel del anestesiólogo, colocando correctamente el tubo endotraqueal electromiográfico, de manera que los electrodos hagan contacto con las cuerdas vocales durante toda la intervención. Además, los resultados de la electromiografía se ven afectados por los bloqueantes neuromusculares, por lo que debemos adecuar la elección y dosis garantizando una profundidad anestésica adecuada. La realización de un protocolo conjunto con el resto de especialistas resulta muy útil (AU)

Recurrent laryngeal nerve injury remains one of the main complications in thyroid and parathyroid surgery. When this injury is bilateral, an acute upper airway obstruction may occur, leading to a potentially life-threatening situation for the patient. The visual identification of the nerve during surgery is the best way to preserve its integrity. However identification of the nerves by means of electromyographic stimuli through electrodes attached to endotracheal tubes could help in decreasing nerve injury. In these cases the experience and role of the anesthetist is essential to correctly place the electromyographic endotracheal tube and ensure that the electrodes are in touch with the vocal cords during the surgery. Moreover, the results of the electromyography can be affected by the neuromuscular blocking agents. Therefore, the choice and dose must be adapted, in order to ensure a suitable anesthetic depth, and adequate response (AU)

[Monitoring of recurrent laryngeal nerve injury using an electromyographic endotracheal tube in thyroid and parathyroid surgery. Anesthetic aspects]. / Monitorización del nervio laríngeo recurrente mediante tubo orotraqueal electromiográfico en cirugía de tiroides y paratiroides. Consideraciones anestésicas.

Recurrent laryngeal nerve injury remains one of the main complications in thyroid and parathyroid surgery. When this injury is bilateral, an acute upper airway obstruction may occur, leading to a potentially life-threatening situation for the patient. The visual identification of the nerve during surgery is the best way to preserve its integrity. However identification of the nerves by means of electromyographic stimuli through electrodes attached to endotracheal tubes could help in decreasing nerve injury. In these cases the experience and role of the anesthetist is essential to correctly place the electromyographic endotracheal tube and ensure that the electrodes are in touch with the vocal cords during the surgery. Moreover, the results of the electromyography can be affected by the neuromuscular blocking agents. Therefore, the choice and dose must be adapted, in order to ensure a suitable anesthetic depth, and adequate response.

El hallazgo de glucosa en el fluido obtenido por el catéter epidural después de su inserción durante la anestesia combinada intradural-epidural realizada con bupivacaína hiperbara es un suceso habitual / The finding of glucose in the fluid obtained by epidural catheter after its insertion during combined intradural-epidural anaesthesia with hyperbaric bupivacaine is a usual occurrence

Objetivos. Evaluar si la aparición de glucosa en el fluido obtenido espontáneamente del catéter epidural tras su inserción, durante la anestesia combinada intradural-epidural realizada con bupivacaína hiperbara, es un suceso habitual. Pacientes y métodos. Estudio observacional prospectivo en 34 pacientes con anestesia combinada intradural-epidural a los que después de localizar el espacio epidural con solución salina, insertar la aguja espinal e inyectar bupivacaína hiperbara, se les introdujo un catéter epidural. Tras observar si goteaba espontáneamente algún fluido por él, se determinó si este contenía glucosa. Retirada la aguja epidural y lavada su luz con solución salina, se comprobó si en el lavado existía glucosa. Las muestras se analizaron con un glucómetro. Cuando desapareció el bloqueo motor se administró una dosis de anestésico local por el catéter epidural. Se valoró la asociación de los parámetros demográficos con el goteo espontáneo por el catéter epidural. Resultados. En 22 pacientes se produjo goteo espontáneo por el catéter epidural tras su inserción. Todas las muestras obtenidas contenían glucosa. En 9 de 34 muestras del lavado de aguja epidural existía glucosa. Ningún paciente sufrió bloqueo sensitivomotor excesivo. Se encontró asociación estadísticamente significativa (p<0,05) de la edad con el goteo espontáneo por el catéter (a más edad, más goteo). Conclusión. El hallazgo de glucosa en el fluido obtenido por el catéter epidural es un suceso frecuente y sin significación clínica. Proponemos que pudo deberse a fuga de líquido cefalorraquídeo por el agujero de punción dural durante o después de la administración de la bupivacaína hiperbara y al derrame de esta en el espacio epidural(AU)

Objectives. To determine whether the appearance of glucose in the fluid spontaneously obtained by the epidural catheter after its insertion during combined intradural-epidural anaesthesia with hyperbaric bupivacaine is a usual occurrence. Patients and methods. A prospective, observational study was conducted on 34 patients with combined intradural-epidural anaesthesia in whom an epidural catheter was introduced, after locating the epidural space with a saline solution, inserting a spinal needle and injecting hyperbaric bupivacaine. After observing whether any fluid was spontaneously dripping from it, it was determined if this contained glucose. Withdrawal of the needle and washing its lumen with saline solution, it was checked whether there was glucose in washout. The samples were analysed using a glucose meter. When the motor block disappeared a dose of local anaesthetic was administered through the epidural catheter. The relationship of the demographic parameters with the spontaneous dripping of the epidural catheter was evaluated. Results. Spontaneous dripping by the epidural catheter after its insertion was observed in 22 patients. All the samples obtained contained glucose. There was glucose in 9 out of 34 epidural needle wash samples. None of the patients suffered from excessive motor-sensory block. There was a statistically significant relationship between patient age (P<.05) and spontaneous dripping by the catheter (the higher the age, more dripping). Conclusion. The finding of glucose in the fluid obtained by the epidural catheter is a frequent occurrence and is of no clinical significance. We propose that it could be due to a leak of cerebrospinal fluid by the dural puncture needle during or after the administering of the hyperbaric bupivacaine and the spillage of this into the epidural space(AU)

[The finding of glucose in the fluid obtained by epidural catheter after its insertion during combined intradural-epidural anaesthesia with hyperbaric bupivacaine is a usual occurrence]. / El hallazgo de glucosa en el fluido obtenido por el catéter epidural después de su inserción durante la anestesia combinada intradural-epidural realizada con bupivacaína hiperbara es un suceso habitual.

OBJECTIVES: To determine whether the appearance of glucose in the fluid spontaneously obtained by the epidural catheter after its insertion during combined intradural-epidural anaesthesia with hyperbaric bupivacaine is a usual occurrence. PATIENTS AND METHODS: A prospective, observational study was conducted on 34 patients with combined intradural-epidural anaesthesia in whom an epidural catheter was introduced, after locating the epidural space with a saline solution, inserting a spinal needle and injecting hyperbaric bupivacaine. After observing whether any fluid was spontaneously dripping from it, it was determined if this contained glucose. Withdrawal of the needle and washing its lumen with saline solution, it was checked whether there was glucose in washout. The samples were analysed using a glucose meter. When the motor block disappeared a dose of local anaesthetic was administered through the epidural catheter. The relationship of the demographic parameters with the spontaneous dripping of the epidural catheter was evaluated. RESULTS: Spontaneous dripping by the epidural catheter after its insertion was observed in 22 patients. All the samples obtained contained glucose. There was glucose in 9 out of 34 epidural needle wash samples. None of the patients suffered from excessive motor-sensory block. There was a statistically significant relationship between patient age (P<.05) and spontaneous dripping by the catheter (the higher the age, more dripping). CONCLUSION: The finding of glucose in the fluid obtained by the epidural catheter is a frequent occurrence and is of no clinical significance. We propose that it could be due to a leak of cerebrospinal fluid by the dural puncture needle during or after the administering of the hyperbaric bupivacaine and the spillage of this into the epidural space.

Dudas y dificultades observadas al seguir las 'Recomendaciones de prevención y tratamiento de las naúseas y vómitos postoperatorios y/o asociados a las infusiones de opioides' / Doubts and difficulties observed on following the 'Recommendations for the Prevention and Treatment of Postoperative Nausea and Vomiting Associated With Opioid Infusions'

No disponible

Evaluación de la eficacia de la imagen en telefonía móvil paracirugía ambulatoria / No disponible

Introducción: Tras el alta se necesita mejorar la comunicación entre la unidad de cirugía sin ingreso y el domicilio de los pacientes para ofrecer la misma calidad asistencial y los mismos cuidados que en la cirugía con ingreso. El objetivo principal del presente estudio es validar el impacto clínico, asistencial y de gestión del sistema de m-Salud de control domiciliario telefónico asistido con imágenes de telefonía móvil y pulsioximetría en el periodo postoperatorio tras intervenciones de cirugía ambulatoria. Material y métodos: Este trabajo presenta los resultados de un estudio prospectivo randomizado de un sistema móvil-health para la monitorización postoperatoria de pacientes en los primeros días del postoperatorio en el domicilio. Se seleccionaron de forma aleatoria 310 pacientes intervenidos de cirugía ambulatoria comparables en complejidad quirúrgica. Evaluamos dos grupos: el grupo piloto (llevaba móvil con transmisión de imágenes del postoperatorio)y el grupo control (sin móvil).Resultados: Los resultados muestran que el control telefónico protocolizado por sí mismo (con o sin imágenes de telefonía móvil) es eficiente en términos de calidad de la información recibida así como en la resolución de complicaciones menores domiciliarias. El grupo piloto requirió mayor tiempo de atención que el grupo control. Conclusiones: Aunque no hayamos observado diferencias entre los dos grupos estudiados consideramos que harían falta estudios posteriores para determinar con mayor exactitud el tipo de paciente idóneo para el control mediante la imagen y pulsioximetría (..) (AU)

Introduction: The rationale behind the need to improve the communication between the ambulatory surgery unit and the patients at home after discharge from ambulatory surgery is to offer a healthcare quality at home comparable to hospital care. Nowadays this improvement is needed, taking into account that more complex operations and patients with higher co morbidity are being included in these programs. The main objective of the study is to validate the clinical impact and management system of a domiciliary control m-health device assisted by mobile phone images and pulsioximetry after ambulatory surgery. Material and methods: This paper presents the results of a randomized prospective study of an m-Health system for post-operative monitoring of patients in the early ambulatory surgery home postoperative process. About 310 patients, with surgeries comparable in complexity, were randomly selected and included in either the intervention or the control group. Results: The results shows that the phone control protocol at home in postoperative process is very efficient in terms of the quality of information received and also in the resolution of late minor complications even compared with the most traditional ways of care. The timing of control of intervention group was longer than the control group. Conclusions: Although we have not observed differences between the two groups studied believe that further studies would be needed to determine more precisely the type of patient suitable for mobile image control and pulsioximetry. In this study is considered necessary to explain clearly instructions and household tips by the relevant personnel before discharge. In the other hand the patients they should known the help paths (direct phone number) in case of necessity (..) (AU)

[Use of a rigid laryngoscope and a flexible nasal fiberoptic scope to assess the difficult airway: description of 3 cases]. / Utilización del laringoscopio rígido y el nasofibroscopio flexible en la valoración de la vía aérea difícil: descripción de 3 casos.

Indirect inspection of the airway using a 70 degrees rigid laryngoscope plus a flexible nasal fiberoptic scope can provide additional information when the anesthesiologist foresees that airway management will be difficult. These devices are useful for detecting structural abnormalities, they can be attached to the same visualization system, and they do not require topical anesthesia or sedation of the patient. We report on 3 patients diagnosed with difficult airway. Inspection with a rigid laryngoscope during the preanesthetic assessment visit revealed abnormalities that prevented visualization of the glottis. In the first case, the epiglottis was absent, as it had been removed with a surrounding tumor; in the second and third cases, an epiglottic deformity and hypertrophy of the base of the tongue were found. A flexible nasal fiberoptic scope gave an unobstructed view of the glottis in these cases, making it easier to choose an intubation method.

Utilización del laringoscopio rígido y el nasofibroscopio flexible en la valoración de la vía aérea difícil: descripción de 3 casos / Use of a rigid laryngoscope and a flexible nasal fiberoptic scope to assess the difficult airway: description of 3 cases

La exploración de los pacientes con criterios de dificultaden el manejo de la vía aérea puede ser ampliadacon la realización de una laringoscopia indirecta utilizandoel laringoscopio rígido de 70º y el nasofibroscopioflexible. Son útiles para detectar anomalías estructurales,se acoplan al mismo sistema de visualización y noprecisan anestesia tópica ni sedación de los pacientes.Presentamos 3 pacientes diagnosticados de vía aéreadifícil, a los que se les realizó en la consulta de valoraciónpreanestésica una laringoscopia con el laringoscopiorígido. Se observó en el primero la falta de epiglotis,en el segundo una deformidad epiglótica y en el tercerouna hipertrofia de la base de la lengua, anormalidadesque impedían la visión de la glotis. Se les practicó unalaringoscopia con el nasofibroscopio flexible que permitióobservar la glotis sin obstáculos. La visión completade la vía aérea facilitó la elección del método de intubación(AU)

Indirect inspection of the airway using a 70° rigidlaryngoscope plus a flexible nasal fiberoptic scope canprovide additional information when the anesthesiologistforesees that airway management will be difficult. Thesedevices are useful for detecting structural abnormalities,they can be attached to the same visualization system, andthey do not require topical anesthesia or sedation of thepatient. We report on 3 patients diagnosed with difficultairway. Inspection with a rigid laryngoscope during thepreanesthetic assessment visit revealed abnormalities thatprevented visualization of the glottis. In the first case, theepiglottis was absent, as it had been removed with asurrounding tumor; in the second and third cases, anepiglottic deformity and hypertrophy of the base of thetongue were found. A flexible nasal fiberoptic scope gavean unobstructed view of the glottis in these cases, makingit easier to choose an intubation method(AU)

Bispectral index changes in carotid surgery.

BACKGROUND: Intraoperative monitoring of cerebral ischemia with shunting during carotid endarterectomy (CEA) remains controversial. Our objective was to evaluate the sensitivity and specificity of BIS changes during carotid clamping in relation to shunted patients in awake CEA. METHODS: Eighty CEAs under cervical block were included. There were two patient groups: with clinical signs of cerebral ischemia (shunted patients) and without signs of cerebral ischemia (nonshunted patients). Data were based on bispectral index (BIS) values and neurological monitoring at different surgery time points, with special attention paid during carotid clamping. BIS values were compared between shunted and nonshunted patients. Sensitivity and specificity, along with positive and negative predictive values of a percentage BIS value decrease during carotid clamping from baseline BIS values, were calculated in both patient groups. RESULTS: Shunting was performed in 11 patients with cerebral ischemia at carotid clamping. Mean BIS values were 82.82+/-11.98 in shunted patients and 92.31+/-5.42 in nonshunted patients at carotid clamping (p<0.001). Relative decreased BIS values in relation to basal BIS values were 13.57% in shunted patients and 3.68% in nonshunted patients (p<0.05). The percentage decrease in BIS was 14%, sensitivity was 81.8% (95% CI 49.9-96.8), and specificity was 89.7% (95% CI 79.3-95.4). CONCLUSION: BIS monitoring during carotid clamping is an easy, noninvasive method which correlates with cerebral ischemia in patients undergoing CEA. A decrease>or=14% from the basal BIS value presents a high negative predictive value, and ischemia is unlikely without a decrease. Nonetheless, a decrease may not always indicate cerebral ischemia with a low positive predictive value.

[Quantitative test to distinguish spinal fluid from saline solution in combined spinal-epidural anesthesia]. / Método cuantitativo para distinguir el líquido cefalorraquídeo de la solución salina en la anestesia combinada intradural-epidural.

OBJECTIVES: To validate the use of a digital blood glucose meter for detecting the presence of spinal fluid during combined spinal-epidural anesthesia in terms of specificity, positive and negative predictive values, and likelihood ratios. PATIENTS AND METHODS: Validation was studied in 30 patients scheduled for surgery under combined spinal-epidural anesthesia. A positive finding, defined as detection of spinal fluid return or aspiration by the epidural or spinal needle, was compared with results of standard reference tests (the pattern of sensory or motor block after administration of the local anesthetic). After locating the epidural space with saline solution, the test was performed and 3 mL of local anesthetic was administered. If no sensory or motor blockade was evident, the test was considered a true negative. Spinal puncture was then performed, the test was repeated, and 2 to 3 mL of local anesthetic was injected. The test was considered a true positive if sensory or motor blockade was evident. These findings entered into the validation analyses. RESULTS: Sensitivity was 100%, specificity 94%, positive predictive value 93%, negative predictive value 100%, the positive likelihood ratio 15.5, and negative likelihood 0. CONCLUSION: Blood glucose meter readings provide a valid quantitative measure for distinguishing spinal fluid from saline solution during combined spinal-epidural anesthesia. The method, which uses a readily available device, is easy to use to rule out the presence of spinal fluid.

Método cuantitativo para distinguir el líquido cefalorraquídeo de la solución salina en la anestesia combinada intradural-epidural / Quantitative test to distinguish spinal fluid from saline solution in combined spinalepidural anesthesia

OBJETIVOS: Proponer la utilización de un glucómetrodigital como método cuantitativo sencillo para detectarlíquido cefalorraquídeo durante la técnica de anestesiacombinada epidural-intradural y determinar su validez,a través de la sensibilidad, especificidad, valores predictivosy cocientes de probabilidad.PACIENTES Y MÉTODOS: Se realizó el estudio de validezdel test en 30 pacientes programados para cirugía conanestesia combinada intradural-epidural. Se consideróun resultado positivo si había glucosa en el líquido querefluía o se aspiraba a través de la aguja epidural eintradural, y se contrastaba con un patrón de referencia(las características del bloqueo sensitivo o motor tras laadministración de anestésico local). Tras localizar elespacio epidural con solución salina, se realizaba el testy se administraban 3 mL de anestésico local. Si no habíabloqueo sensitivo o motor, el test se consideraba verdaderonegativo. Se realizaba la punción dural, se realizabael test y se administraban 2-3 mL de anestésico local.En este caso si había bloqueo sensitivo o motor el test seconsideraba verdadero positivo. Con todo ello se realizóel análisis de validez.RESULTADOS: La sensibilidad del test fue del 100%, suespecificidad del 94%, el valor predictivo positivo de93%, y el valor predictivo negativo de 100%, la razón deprobabilidad positiva de 15,5 y la negativa de 0.CONCLUSIÓN: El glucómetro utilizado es un métodocuantitativo válido para diferenciar líquido cefalorraquídeode solución salina durante la anestesia combinada,de uso sencillo y fácilmente disponible, con una granutilidad para confirmar o descartar la presencia delíquido cefalorraquídeo(AU)

OBJECTIVES: To validate the use of a digital bloodglucose meter for detecting the presence of spinal fluidduring combined spinal-epidural anesthesia in terms ofspecificity, positive and negative predictive values, andlikelihood ratios.PATIENTS AND METHODS: Validation was studied in 30patients scheduled for surgery under combined spinalepiduralanesthesia. A positive finding, defined asdetection of spinal fluid return or aspiration by theepidural or spinal needle, was compared with results ofstandard reference tests (the pattern of sensory or motorblock after administration of the local anesthetic). Afterlocating the epidural space with saline solution, the testwas performed and 3 mL of local anesthetic wasadministered. If no sensory or motor blockade wasevident, the test was considered a true negative. Spinalpuncture was then performed, the test was repeated, and2 to 3 mL of local anesthetic was injected. The test wasconsidered a true positive if sensory or motor blockadewas evident. These findings entered into the validationanalyses.RESULTS: Sensitivity was 100%, specificity 94%,positive predictive value 93%, negative predictive value100%, the positive likelihood ratio 15.5, and negativelikelihood 0.CONCLUSION: Blood glucose meter readings provide avalid quantitative measure for distinguishing spinal fluidfrom saline solution during combined spinal-epiduralanesthesia. The method, which uses a readily availabledevice, is easy to use to rule out the presence of spinalfluid(AU)

Utilización del BIS como predictor de la amnesia anterógradaproducida por el midazolam intranasal administradocomo premedicación / The bispectral index as a predictor of anterograde amnesia caused by premedication with intranasal midazolam

OBJETIVOS: Determinar la capacidad del índice biespectral(BIS) como predictor de amnesia anterógrada para loseventos que ocurren desde la llegada a quirófano de lospacientes hasta la inducción anestésica, después de premedicarloscon 10 mg de midazolam intranasal.PACIENTES Y MÉTODOS: Pacientes intervenidos paracualquier intervención quirúrgica programada con anestesiageneral, después de monitorizarlos con el índice biespectraly administrarles 10 mg de midazolam por víaintranasal. Se observó el BIS hasta que empezó a bajar demanera continua y mantenida por debajo del valor de 90,se anotó el tiempo transcurrido y se les trasladó a quirófano.Todos los pacientes fueron sometidos a seis maniobrasrutinarias antes de la inducción. Finalizada la intervenciónse les interrogó sobre los recuerdos de las maniobras realizadas.Se estudiaron los valores de sensibilidad, especificidady valores predictivos; para obtener la cifra de BISque presenta una mejor combinación de sensibilidad yespecificidad, se trazó una curva ROC.RESULTADOS: Incluímos 55 pacientes, el tiempo mediotranscurrido en descender el valor de BIS fue 5,93 ± 2,93minutos. La sensibilidad total de la prueba es de 0,96 y laespecificidad de 0,60, el valor predictivo positivo de 0,91 yel valor predictivo negativo de 0,75. El valor global de laprueba es del 89,1%. El mejor valor de corte de la curvaROC es 83.CONCLUSIONES: La disminución del BIS por debajo delvalor de 90 se puede usar como predictor de amnesia anterógradatras la administración de 10 mg de midazolamintranasal (AU)

OBJETIVE: To determine the ability of the bispectralindex (BIS) to predict anterograde amnesia for eventsoccurring between the arrival of patients in the operatingtheater and anesthetic induction, following premedicationwith 10 mg of intranasal midazolam.PATIENTS AND METHODS: We enrolled patients scheduledfor any type of surgery under general anesthesia. Patientswere first monitored using the BIS and administered 10mg of intranasal midazolam. The BIS was monitored untilit began to fall steadily and remained below a value of 90;the elapsed time was recorded and the patient was takento the theater. All patients underwent 6 routine maneuversbefore induction. After surgery, patients were asked abouttheir memory of the maneuvers performed. Sensitivity,specificity, and predictive values were studied to obtain theBIS value that provided the best combination of sensitivityand specificity, and a receiver operating characteristic(ROC) curve was drawn.RESULTS: We enrolled 55 patients. The mean (SD) timetaken for the BIS value to fall was 5.93 (2.93) minutes. Thesensitivity of the test was 0.96 and specificity was 0.60. Thepositive predictive value was 0.91 and the negativepredictive value was 0.75. The test classified 89.1% of thepatients correctly. The ROC curve showed the best cutoffto be 83.CONCLUSIONS: A fall in the BIS to below 90 can be usedas a predictor for anterograde amnesia followingadministration of 10 mg of intranasal midazolam (AU)

[Comparison of 2 devices to measure spinal fluid glucose concentration in hyperbaric spinal anesthesia]. / Comparación de dos sistemas de medida de las concentraciones de glucosa en líquido cefalorraquídeo en la anestesia intradural hiperbara.

OBJECTIVES: To compare spinal fluid glucose measurements recorded by the laboratory analyzer Synchron LX20 Pro and the glucometer Ascensia Elite XL during continuous spinal anesthesia after injection of 10 mg of hyperbaric bupivacaine, in order to assess the reliability and speed of the 2 devices for monitoring changes in glucose concentration. PATIENTS AND METHODS: Prospective study of 34 patients under continuous spinal anesthesia administered through a 22-gauge catheter; 9 samples of spinal fluid were extracted from each patient for glucose level measurement. The first extraction was before administration of the anesthetic and the remaining ones were during spinal anesthesia until the end of complete motor block. Correlation was assessed with the Pearson test and agreement with the Bland-Altman method. RESULTS: A total of 241 pairs of measurements were obtained. The correlation was r = 0.96 (P < .01). The mean (SD) difference in measurements from the 2 devices was -1.06 (34.82 mg x dL(-1)). The percentage of variation (systematic error) was -1.9% (11.8%), placing the 95% confidence interval between -25% and 21.2%. CONCLUSIONS: Measurements from the 2 devices are highly correlated. The absolute and percentage systematic error (bias) is negligible. Finding that 95% of measurements are within 23% of the mean seems a fair percentage of error to us. We therefore believe the percentage variation, or systematic error, is clinically acceptable and that either device can be used.