The KTR-4 is used for ventilating the most frequently used animals in the laboratory, from rodent to rabbit. It employs electronic control. This permits flexible adaptation of the ventilation parameters to the most diverse experimental conditions. The functional sequence is signaled by suitably marked signal LEDs. The ventilation sequence can also be influenced by external signals.

Unlike a STARLING piston pump, use of the KTR-4 avoids the danger of excessively extending and damaging the lung of the ventilated animal through incorrect setting of the stroke volume. The electronic control of the KTR-4 also permits free selection of the ventilation timing over a wide range in order to adapt it to the requirements of your experiment. Due to the basic design of a STARLING pump, it is impossible to vary the ratio of inspiration to expiration, for example.

The KTR-4 operates on the principle of intermittent positive pressure ventilation. A continuously adjustable air (gas) stream is passed by solenoid valves either to the animal or to an overflow outlet. The effective pressure in the ventilation cannula is measured and indicated. By suitable settings on the unit it is possible to utilize the measuring circuit to terminate the inspiration process when a given adjustable ventilation pressure has been reached (EIP LIMIT: 0–29 cmH20). This effectively protects the animal against excessive pressure rise in the lung.

Through the “Plateau” function, the end-inspiratory pressure can be maintained constant over an adjustable period of time. This function permits direct control of the inspired air retention. Measurements can also be performed in the inspired condition.
The air flow to the ventilated animal is adjusted by means of a built-in needle valve. The set air flow is indicated on a float flowmeter (rotameter).

The connection to the tracheal cannula is made through a specially formed Y-shaped ventilation cannula. It carries the following tubing on its three ends: inspiration (4 mm dia.), expiration (6 mm dia.) and pressure measurement (4 mm dia.).
The ventilation air required is normally supplied by a built-in pump. There is also a provision for introducing ventilation gas from outside (max. pressure: 0.5 bar). A special version has the internal pump replaced by a precision pressure regulator; in this case the supply has to be provided by an external pressure source (pressure range: 2 - 8 bar).

Adjustable ventilation parameters:
• Ventilation rate: 1–199 bpm (breaths per minute), digital setting.
• Ratio of inspiration to expiration period: 1–99%, digital setting.
• Plateau duration: 0–99% (of total cycle time); measurements can be performed in the inspired condition.
• Adjustable continuous air flow: 4 l/min max.
• Minute volume range: up to 2000 ml/min (“INSPIR” = 50%).

Pressure measurement and selected digital display (range: 29.9 cmH20)
• EIP (end-inspiratory pressure).
• EEP (end-expiratory pressure).
• LIMIT display of set pressure limit EIP LIMIT (0 - 29 cmH20).
• LEAK AL. Display of alarm setting for pressure drop.

Electrical outputs:
• Recording output for ventilation pressure: 0.1 V/cmH20
• Trigger output (TTL) to synchronize external equipment.

Other functions:
• Alarm function: audible/visual on pressure drop, alarm level adjustable.
• Indication of function sequence by LEDs.

External control facilities (TTL level, active low):
• Stop Cycle: the cyclic sequence is stopped immediately.
• Trigger one cycle (in TRIG.EXT. mode).
• Stop after expiration.
• Stop after inspiration.
• Close expiration valve (in TRIG.EXT. mode).
• Open inspiration valve (in TRIG.EXT. mode).

Air/gas connections:
• Outlet for expiration air/gas (EXHAUST EXPIR), immersion tube for PEEP adjustment is connected here, gas is sampled here for analysis of expired gas.
• Outlet for unused air or gas (EXHAUST OVERFLOW).
• Connections for Halothane vaporizer (FROM/TO HALOTHANE VAPORIZER).

The ventilator is delivered with the tracheal cannula adapter (73-2943) and two cannulae with 2.5mm (73-2725) and 3.0mm (73-2724) OD. All cannulae with Luer connector for tracheotomy or intubation can be connected to this adapter.

For larger animals like rabbits or small cats, special cannulae with 4.0mm (73-2938), 5.0mm (73-2939) or 6.0mm (73-2940) are available.