Anesthesia work station

The modern anaesthesia workstation is designed to be a complete anaesthesia and respiratory gas delivery and monitoring system. The new machines use advanced electronics, software and technology to offer extensive capabilities for ventilation, monitoring, inhaled agent delivery, low-flow anaesthesia and closed-loop anaesthesia.

Example: Draeger Primus

The components of the workstation are:

1. The gas delivery and scavenging system. 
2. The vapourisers. 
3. Electronic flow meters. 
4. The ventilator. 
5. The monitors. 

Electronic flow meters:

These are more accurate and do not have the disadvantages of having multiple mechanical parts which are prone to leaks and breakages. The flow can be displayed electronically by a numerical display or ‘virtual flow tubes’à easy identification of gas flows in a darkened theatre and the export of electronic data to an information system.

In some machines mechanical flow meters are provided to deliver oxygen in absence of electrical power.

Circle systemModern anaesthesia machines are primarily designed to use a circle system equipped with features for low flow anaesthesia. The circuits are made compact to reduce circuit volumes to enable rapid changes in gas composition at low flows. Also the manifold may be heated to reduce condensation of water vapour. Built in water traps in the circuit to collect the precipitation. Vertically mounted unidirectional valves to decrease resistance to flow.

Carbon dioxide (CO₂) absorbers are also now available as disposable units for ease of replacement 

VENTILATOR
Machines are equipped with technology and features present in advanced intensive care unit ventilators. Ventilation modes such as pressure support ventilation (PSV) and volume assist ventilation have been introduced to support ventilation in patients maintained on spontaneous breathing through a LMA. In addition, synchronized intermittent mandatory ventilation (SIMV) breaths can be added to both pressure and volume controlled ventilation.

They have the ability to deliver very low tidal volumes accurately.

Respiratory monitors

1. Spirometry
   
2. Waveformsàpressure time and volume time waveform plus some also show flow time & flow volume waveforms for ventilating diseased lung.

Target Controlled Anaesthesia (TCA)à anaesthetists simply set their targets (end tidal agent concentration), allowing the machine to calculate reasonable and efficient way of delivery.
(help protect against over-delivery and under-delivery of agent and hypoxia. This provides cost-effective anaesthesia by keeping gas consumption to an absolute minimum.)

TIVAà  they have syringe pumps with integrated drug database actively linked to a software system which automatically sets default values and dosages boundaries for various drugs

Automatic machine check (self-test)à Most modern anaesthesia delivery systems perform the self-test and have ability to detect and report the faults

Monitoring stationà

Touch screen operations with drop down menu allow access to many functions through simple commands.
Flexible screen configurations that can be configured according to need, with extensive clinical measurements menu that include haemodyanamic, respiration and ventilation monitoring, temperature, anaesthesia depth monitoring and anaesthesia gas monitoring.

·        Certain monitors also provide monitoring of muscle relaxation.

Limitations

1. Continued movement of a descending bellows despite a leak or disconnection. 
2. A small amount of PEEP transmitted to the patient during ventilation with an ascending bellows system. 
3. Augmentation of tidal volume when the oxygen flush is activated in the inspiratory phase of ventilator delivered breath in machines without FGD. 
4. Dependence on electricity. 
5. Inability to detect CO production 
6. human error due to ignorance or lack of understanding or training.