This ISVRA field trial deals with a new entry in the veterinary field as far as monitoring is concerned: the Nellcor N5500 anaesthesia/ICU multiparametric monitor. With its compact look and reduced dimensions (5 kg), and its 6 colour 6.4 inch LCD display, this nice piece of equipment matches easy graphics with intuitive setting, which enables immediate usage even to those who are not very familiar with trends and waveforms. Equipped with a Ni-Mh battery which ensures an hour of monitoring, Nellcor N5500 may be connected with an integrated thermic printer (customarily supplied in NP5500) for printing of trends in tabular form, of numerical data, and of 2 waveforms in real time. An RS 232 output allows its connection with a PC for the transferring of stored data. Let’s now get into details of the monitored parameters, which are ECG, heart rate, non-invasive systolic, mean and diastolic arterial pressure (NIBP), arterial saturation of haemoglobin (SpO2), respiratory rate, and temperature.
The ECG trace can be visualized (and printed if printer is available) in the 3 typical leads of anaesthetic monitoring (I, II, III) if you use the three electrodes wire, or in the 7 leads (I, II, III, V, aVR, aVF, aVL) in the case of five electrodes wire. The wave scrolling speed may be set at 12.5, 25 or 50 mm per second and the wave width can be adjusted between 1.25 and 20 mm per mV, allowing the picking up of the weakest signals, regulating sensitivity. Wires can be equipped with clips or adhesive skin pads.
Heart rate may be detected through three parameters, at the operator’s choice: ECG, pletismographic wave, or NIBP measurement in case of absence of the first two ones. As most monitors created for the non-veterinary medical world, it shows frequencies ranging between 20 and 250 beats per minute, omitting numerical data for frequencies exceeding the mentioned range. This prevents the measuring heart rate during extreme tachycardia in small dog and cats, or in exotic species with very high heart rates.
NIBP (Non Invasive Blood Pressure) determines systolic, mean and diastolic pressure using an oscillometric method in three different ways: manual (the reading is taken only at the operator’s request), automatic (the monitor records readings at selected intervals between 1 and 90 minutes), or in the stat mode (on command, the monitor does the maximum number of readings in five minutes, leaving on the display the last measurement. The producer supplies a set of 5 cuffs (though you can also buy others, from the same company or from others) for measuring blood pressure in anatomical parts with a circumference between 5 and 33 cm. A neonatal tubing (which is suitable for most of our patients) and a paediatric/adult tubing (suitable for big dogs)are available. To this purpose, it is necessary to remember setting the monitor in neonatal mode when using the neonatal tubing and in paediatric mode when using the adult tubing, otherwise an error message will replace the measurement digits. This instrument deserves a positive opinion for its peculiar sensitivity in measuring such a difficult parameter as NIBP in veterinary medicine, particularly in very small dogs and cats with thick fur. For this kind of patients, the real problem is the oscillometric method, not very suitable for them, but from this point of view Nellcor N5500 shares the same drawback with other oscillometric monitors on the market.
The real pride of this instrument is with no doubt SpO2 monitoring. Equipped with the most recent Nellcor technology, which synchronizes ECG with plethysmographic wave to produce a reliable reading even if the patient moves or with poor peripheral perfusion, the N5500 visualizes (and can print) the plethysmographic wave track, showing the numerical value of saturated haemoglobin and the width of peripheral pulsations. Also, we would like to remark that Nellcor are the leading manufacturers of a wide range of quality sensors, both for “human” patients (adhesive and non-adhesive, in various shapes and sizes) and for the veterinary world (like the Vet-Sat series, for small and large animals), capable of satisfying the needs of the most demanding anaesthetist, dealing with “out of standard” patients or for special applications.
The monitoring of ventilation is done by measurement of trans-thoracic impedance through the ECG electrodes (RA and LA). The impedance wave and at the same time the respiratory rate are displayed, with respiratory rate interval ranging from 3 to120 breaths per minute.
Finally, N5500 is supplied with a probe for central temperature measurement (rectal or oesophageal), and can be supplied with a probe for peripheral temperature measurement as well. Central and peripheral temperature are displayed on the screen at the same time.
All monitored parameters have audible alarms with default and user’s limits with 3 priority levels. Error messages will lead the operator towards the resolution of main problems.
[Enrico Stefanelli, ISVRA tester]