Peters Jl

Monitoring body-core temperature from the trachea : Comparison between pulmonary artery, tympanic, esophageal, and rectal temperatures

Introduction. We designed an endotracheal tube (ETT) for acquiring body-tore temperature from the trachea. This ETT had two temperature sensors, one attached to the inside surface of the cuff, the other mounted on the ETT shaft underneath the cuff. The ETT was evaluatedin vitro and in dogs to determine: 1) optimal position of temperature sensors and 2) the responsiveness, accuracy, and resistance to ventilatory artifacts.Methods.In vitro. An artificial trachea assessed the response-time and accuracy of ETT temperature sensors to abrupt temperature changes and ventilatory flow-rates.In vivo. Body temperature in 5 dogs was lowered to approximately 26°C then elevated toward 39°C using a heat exchanger during carotid jugular bypass. ETT temperature measurements were compared simultaneously with those from the artificial trachea (in vitro) or from the pulmonary artery, tympanic cavity, esophagus, and rectum of dogs using dry and humidified gas.Results. Cuff temperature sensor responded quickly and accurately to temperature changes and was less prone than the tube sensor to ventilatory and humidity artifacts. During carotid-jugular bypass,in vivo tube and cuff mean temperatures averaged 1.4°C and 0.36°C lower, respectively, than pulmonary artery temperatures. There were no statistical differentes (P > 0.05) between cuff temperatures and those measured from the pulmonary artery, tympanic cavity, esophagus, and rectum. Heating and humidifying the inspiratory gas of dogs with a water-bath humidifer or heat moisture exchanger (HME) had minimal effects on the cuff temperature sensor. An in-line HME increasedin vivo tube temperature from baseline values by 1.13 ± 0.80 °C, while cuff temperature increased by 0.21 ±0.24°C.Conclusion. The cuff of the ETT is a reliable site for measuring body-tore temperature in intubated patients.

Comparative Evaluation of Artificial Ventricles in the United States

A cooperative, comparative evaluation of nine artificial ventricles was performed on two standardized mock circulations. The ventricles included five air-driven diaphragm types, three sack types and a mechanically driven type. The slopes of the ventricular output curves varied from 0.04 to 0.88 at 0 to 5 Torr filling pressure and the maximum ventricular output varied from 3.8 to 11.9 liters/min at 100 Torr outflow pressure. All ventricles had decreased output with increased outflow pressures (70 to 130 Torr). Hemolysis index ratio (HI test/HI std) for HI std equals 0.024 plus or minus .005 (plus or minus 1 SD) g/100 liters (N equals 12), was +21.5 and +6.9 for a Dacron cloth and fibril heart, respectively, +2.0 to +2.86 for three sack ventricles, and +3.2 for a smooth diaphragm ventricle. The mechanical ventricle with a sinusoidal driving waveform and smooth surface had the lowest hemolysis, HI equals 0.008 plus or minus 0.003 (plus or minus 1 SD) (N equals 6). Sack ventricles caused marked hemolysis if the walls touched during systole. Ventricular dimensions varied: weight 116 to 700 g, length 9.2 to 18.7 cm, and volume 235 to 430 ml. Performance data was returned to each individual laboratory which resulted in modification of ventricular design in at least three instances. Comparative, standardized testing of artificial ventricles may shorten development time and provide performance criteria for application in man.

Monitoring normal and aberrant electrocardiographic activity from an endotracheal tube: Comparison of the surface, esophageal, and tracheal electrocardiograms

Introduction. We designed an endotracheal (ET) tube with orthogonally spaced ECG cuff electrodes. This ET tube was evaluated in dogs and sheep to determine (1) whether ECGs recorded from our tube were sufficient to make accurate clinical decisions concerning heart rate and rhythm; and (2) whether metallic cuff electrodes in direct contact with the trachea could induce mucosal burn injury during episodes of defibrillation.Methods. Using experimental animals, we obtained ECGs from their tracheae and compared our findings with ECGs obtained from surface and esophageal electrodes. The electrical activity of the heart was modified by increasing the depth of anesthesia, occluding the left coronary artery, and administering beta-adrenergic drugs. Before the dogs were euthanized, they were subjected to episodes of transthoracic and intrathoracic defibrillation at energy levels of 200 to 400 J. A postmortem pathological examination of the trachea was performed to determine the incidence of mucosal burn injury.Results. Tracheal electrocardiography provided valid information on heart-rate monitoring and certain morphology profiles. The R-R, PR, QRS, and QT intervals measured from the trachea had a correlation of 1.0, 0.96, 0.83, and 0.98, respectively, when compared with the same intervals obtained from surface electrodes. Two tracheae subjected to intrathoracic defibrillation at >300 J revealed evidence of minor burn injury. Some localized epithelium loss was displayed in all tracheae; we attributed this to tracheal intubation.Conclusion. Tracheal electrocardiography may be useful in trauma patients who require intubation where injury precludes placement of chest ECG electrodes.AbstraktZiel. Wir entwarfen einen Endotrachealtubus (ET) mit rechtwinklig angeordneten EKG-Cuffelektroden. Dieser ET wurde bei Hunden und Schafen getestet, um zu bestimmen, Ob 1) die von unserem Tubus aufgenommenen EKG-Daten ausreichten, um exakte klinische Entscheidungen beziiglich Herzfrequenz und Rhythmus treffen zu konnen; 2) wahrend der Defibrillation metallische Cuffelektroden in direktem Kontakt mit der Trachea Verbrennungsschaden der Schleimhaut verursachen konnten.Methoden. Bei unseren Versuchstieren leiteten wir die EKGs von der Trachea ab und verglichen unsere Ergebnisse mit EKGs, die mit Oberflächen-und Ösophaguselektroden abgeleitet wurden. Wir modifizierten die elektrische Aktivitat des Herzens durch Narkosevertiefung, Verschluβ der linken Koronararterie und Gabe von etasympathomimetika. Vor ihrer Totung wurden die Hunde transthorakal und intrathorakal mit Energien von 200 bis 400 Joule defibrilliert. Postmortal untersuchten wir die Trachea histologisch, um die Inzidenz von Verbrennungsschaden der Schleimhaut zu bestimmen.Ergebnisse. Die tracheale Elektrokardiographie lieferte valide Informationen iiber die Herzfrequenz und gewisse morphologische Profile. Die RR-, PR-, QRS- und QT-Intervalle der Trachealableitung korrelierten mit den entsprechenden Intervallen der Oberflächenableitungen mit Koeffizienten von 1.0, 0.96, 0.83 und 0.98. Die Tracheae zweier Versuchstiere, die intrathorakaler Defibrillation mit >300 Joule unterworfen worden waren, zeigten geringe Verbrennungsschaden. Ortlich begrenzter Verlust von Trachealepithel trat in alien Tracheae auf; wir schrieben dies der Intubation zu.SchluBfolgerung. Die tracheale Elektrokardiographie konnte bei intubationspflichtigen Unfallpatienten, deren Verletzungen die Anlage von Brustelektroden ausschlieβen, nützlich sein.ResumenObjetivo. Disenamos un tubo endotraqueal (ET) con electrodos de ECG en manguito espaciados ortogonalmente. Este tubo ET fue evaluado en perros y ovejas para determinar (1) si los ECG obtenidos desde nuestro tubo eran suficientes para efectuar decisiones clinicas en relacion a la frecuencia y ritmo cardiacos; y (2) si los electrodos metalicos en manguito en contacto directo con la tràquea pudiesen inducir quemaduras de la mucosa durante episodios de defibrilacion.Mètodos. Usando animales experimentales, obtuvimos ECG a partir de sus tràqueas y los comparamos con ECG obtenidos desde electrodos de superficie y desde electrodos esofagicos. La actividad elèctrica cardiaca fue modificada cambiando la profundidad de la anestesia, ocluyendo la arteria coronaria izquierda, y administrando drogas betaadrenèrgicas. Antes de sacrificar los perros, ellos fueron objeto de episodios de defibrilacion transtroràcica e intratoracica con niveles de energia entre 200 y 400 joules. Se realizò examen patològico de la tràquea para determinar la incidencia de quemadura de la mucosa.Resultados. La electrocardiografia traqueal proporcionò informatiòn vàlida en relaciòn a monitorizaciòn de frecuencia cardiaca y algunos perfiles morfo`ogicos. Los intervalos R-R, PR, QRS, y QT medidos en la tràquea tuvieron correlaciones de 1.0, 0.96, 0.83, y 0.98, respectivamente, al ser comparados con los mismos intervalos medidos con electrodos de superficie. Dos traqueas sometidas a defibrilacion intratoracica con energia de 300 joules revelaron evidencia de quemaduras menores. Algun grado de `erdida localizada de epitelio fue observado en todas las traqueas; nosotros atribuimos esto a la intubatiòn traqueal.Conclusion. La electrocardiografia traqueal puede ser ùtil en pacientes traumatizados que requieran intubatiòn en quienes, debido a la injuria, sea poco factible la colocacion de electrodos de ECG en el tòrax.

The relationship between vascular expansion of the aorta and pulmonary artery and the genesis of the impedance cardiogram using the technique of sonomicrometry

Primary objective: This prospective animal study aims to evaluate the contribution of the pulmonary artery (PA) and aorta on the morphology of the impedance cardiogram using sonomicrometry. Methods: Impedance electrodes were placed around the thorax, aorta and in the oesophagus of five dogs. Sonomicrometry crystals were mounted on the PA and aorta for tracking vascular distension while a Doppler flow probe measured aortic blood flow. Results: No significant differences (p > 0.05) were recorded between the onset of aortic expansion, aortic blood flow and the start of the impedance dZ/dt signal. Significant differences (p > 0.001) were recorded between the onset of PA expansion and the dZ/dt signal. PA expansion began 41.6 ± 6.0 ms, 60.7 ± 7.2 ms and 42.2 ± 4.9 ms respectively, before surface, aortic and oesophageal impedance recordings. Conclusion: The genesis of the impedance cardiogram is attributed to volumetric expansion of the aorta.

Lack of CNS depression from large doses of trimethaphan in sheep.

It is not uncommon to observe prolonged CNS depression for several hours following controlled hypotension and halothane anesthesia for neurosurgery. The present study evaluates possible contribution of large doses of trimethaphan to CNS depression. Four adult sheep were placed on transapical left ventricular bypass (TALVB) withdrawing blood from the apex of the left ventricle through a roller pump, Pall Ultipor filter, and returning the blood to a carotid artery. In the awake and unanesthetized animals, 1 to 2 gm of trimethaphan were administered IV during each experiment while maintaining mean arterial pressure at 60 to 75 torr. Two sheep stood up and knelt down without obvious correlation with dose of trimethaphan administered at the time; two remained standing and continued eating during the trimethaphan infusion. Cardiovascular recovery from these large doses of trimethaphan was within 15 to 30 minutes after the conclusion of drug infusion. The data strongly suggest that large doses of trimethaphan have no significant CNS depression in the awake and unanesthetized sheep.