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  Citation statistics : Table of Contents
   2013| September-October  | Volume 57 | Issue 5  
    Online since October 22, 2013

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Mapleson's breathing systems
Tej K Kaul, Geeta Mittal
September-October 2013, 57(5):507-515
DOI:10.4103/0019-5049.120148  PMID:24249884
Mapleson breathing systems are used for delivering oxygen and anaesthetic agents and to eliminate carbon dioxide during anaesthesia. They consist of different components: Fresh gas flow, reservoir bag, breathing tubes, expiratory valve, and patient connection. There are five basic types of Mapleson system: A, B, C, D and E depending upon the different arrangements of these components. Mapleson F was added later. For adults, Mapleson A is the circuit of choice for spontaneous respiration where as Mapleson D and its Bains modifications are best available circuits for controlled ventilation. For neonates and paediatric patients Mapleson E and F (Jackson Rees modification) are the best circuits. In this review article, we will discuss the structure of the circuits and functional analysis of various types of Mapleson systems and their advantages and disadvantages.
  4 28,884 8,346
Anaesthesia ventilators
Rajnish K Jain, Srinivasan Swaminathan
September-October 2013, 57(5):525-532
DOI:10.4103/0019-5049.120150  PMID:24249886
Anaesthesia ventilators are an integral part of all modern anaesthesia workstations. Automatic ventilators in the operating rooms, which were very simple with few modes of ventilation when introduced, have become very sophisticated with many advanced ventilation modes. Several systems of classification of anaesthesia ventilators exist based upon various parameters. Modern anaesthesia ventilators have either a double circuit, bellow design or a single circuit piston configuration. In the bellows ventilators, ascending bellows design is safer than descending bellows. Piston ventilators have the advantage of delivering accurate tidal volume. They work with electricity as their driving force and do not require a driving gas. To enable improved patient safety, several modifications were done in circle system with the different types of anaesthesia ventilators. Fresh gas decoupling is a modification done in piston ventilators and in descending bellows ventilator to reduce th incidence of ventilator induced volutrauma. In addition to the conventional volume control mode, modern anaesthesia ventilators also provide newer modes of ventilation such as synchronised intermittent mandatory ventilation, pressure-control ventilation and pressure-support ventilation (PSV). PSV mode is particularly useful for patients maintained on spontaneous respiration with laryngeal mask airway. Along with the innumerable benefits provided by these machines, there are various inherent hazards associated with the use of the ventilators in the operating room. To use these workstations safely, it is important for every Anaesthesiologist to have a basic understanding of the mechanics of these ventilators and breathing circuits.
  2 9,701 4,193
Anaesthesia machine: Checklist, hazards, scavenging
Umesh Goneppanavar, Manjunath Prabhu
September-October 2013, 57(5):533-540
DOI:10.4103/0019-5049.120151  PMID:24249887
From a simple pneumatic device of the early 20 th century, the anaesthesia machine has evolved to incorporate various mechanical, electrical and electronic components to be more appropriately called anaesthesia workstation. Modern machines have overcome many drawbacks associated with the older machines. However, addition of several mechanical, electronic and electric components has contributed to recurrence of some of the older problems such as leak or obstruction attributable to newer gadgets and development of newer problems. No single checklist can satisfactorily test the integrity and safety of all existing anaesthesia machines due to their complex nature as well as variations in design among manufacturers. Human factors have contributed to greater complications than machine faults. Therefore, better understanding of the basics of anaesthesia machine and checking each component of the machine for proper functioning prior to use is essential to minimise these hazards. Clear documentation of regular and appropriate servicing of the anaesthesia machine, its components and their satisfactory functioning following servicing and repair is also equally important. Trace anaesthetic gases polluting the theatre atmosphere can have several adverse effects on the health of theatre personnel. Therefore, safe disposal of these gases away from the workplace with efficiently functioning scavenging system is necessary. Other ways of minimising atmospheric pollution such as gas delivery equipment with negligible leaks, low flow anaesthesia, minimal leak around the airway equipment (facemask, tracheal tube, laryngeal mask airway, etc.) more than 15 air changes/hour and total intravenous anaesthesia should also be considered.
  2 21,689 5,303
The basic anaesthesia machine
CL Gurudatt
September-October 2013, 57(5):438-445
DOI:10.4103/0019-5049.120138  PMID:24249876
After WTG Morton's first public demonstration in 1846 of use of ether as an anaesthetic agent, for many years anaesthesiologists did not require a machine to deliver anaesthesia to the patients. After the introduction of oxygen and nitrous oxide in the form of compressed gases in cylinders, there was a necessity for mounting these cylinders on a metal frame. This stimulated many people to attempt to construct the anaesthesia machine. HEG Boyle in the year 1917 modified the Gwathmey's machine and this became popular as Boyle anaesthesia machine. Though a lot of changes have been made for the original Boyle machine still the basic structure remains the same. All the subsequent changes which have been brought are mainly to improve the safety of the patients. Knowing the details of the basic machine will make the trainee to understand the additional improvements. It is also important for every practicing anaesthesiologist to have a thorough knowledge of the basic anaesthesia machine for safe conduct of anaesthesia.
  2 27,081 12,098
Vapourisers: Physical principles and classification
Vithal Dhulkhed, Akshaya Shetti, Shraddha Naik, Pavan Dhulkhed
September-October 2013, 57(5):455-463
DOI:10.4103/0019-5049.120141  PMID:24249878
Vapourisers have evolved from rudimentary inhalers to the microprocessor controlled, temperature compensated and flow sensing devices, which are universal today. The improvements in the design was influenced by the development of potent inhalational anaesthetics, unique properties of some agents, a deeper understanding of their mechanism of action, inherent flaws in the older vapourisers, mechanical problems due to thymol deposition, factors influencing their output such as temperature and pressure variations. It is important to review the principles governing the design of the vapouriser to gain insight into their working. It is fascinating to know how some of the older vapourisers, popularly used in the past, functioned. The descendant of Oxford Miniature Vapourizer, the Triservice vapouriser is still a part of the military anaesthesia draw over equipment meant for field use whereas the Copper Kettle the first precision device is the fore-runner of the Tec 6 and Aladdin cassette vapouriser. Anaesthesia trainees if exposed to draw over techniques get a deeper understanding of equipment and improved skills for disaster situations. In the recent advanced versions of the vapouriser a central processing unit in the anaesthetic machine controls the operation by continuously monitoring and adjusting fresh gas flow through the vapouriser to maintain desired concentration of the vapour.
  1 10,619 5,176
Modern anaesthesia vapourisers
Sucharita Chakravarti, Srabani Basu
September-October 2013, 57(5):464-471
DOI:10.4103/0019-5049.120142  PMID:24249879
Inhalational anaesthetic agents are usually liquids at room temperature and barometric pressure and need to be converted to vapour before being used and this conversion is effected using a vapouriser. Vapourisers have evolved from very basic devices to more complicated ones. Anaesthetists should understand the basic principles of anaesthetic vapouriser, including the principles that affect vapouriser output and how they influence vapouriser design. Most of the modern vapourisers in use are designed to be used between the flow meter and the common gas outlet on the anaesthesia machine. Modern vapourisers are flow and temperature compensated, concentration calibrated, direct reading, dial controlled and are unaffected by positive-pressure ventilation. Safety features include an anti-spill and a select-a-tec mechanism and a specific vapouriser filling device. Desflurane has unique physical properties requiring the use of a specific desflurane vapouriser. The most recently designed vapourisers are controlled by a central processing unit in the anaesthetic machine. The concentration of vapour is continuously monitored and adjusted by altering fresh gas flow through the vapouriser. This article looks at the basic design and functioning of the modern vapourisers.
  1 12,312 4,922
Safety features in anaesthesia machine
M Subrahmanyam, S Mohan
September-October 2013, 57(5):472-480
DOI:10.4103/0019-5049.120143  PMID:24249880
Anaesthesia is one of the few sub-specialties of medicine, which has quickly adapted technology to improve patient safety. This application of technology can be seen in patient monitoring, advances in anaesthesia machines, intubating devices, ultrasound for visualisation of nerves and vessels, etc., Anaesthesia machines have come a long way in the last 100 years, the improvements being driven both by patient safety as well as functionality and economy of use. Incorporation of safety features in anaesthesia machines and ensuring that a proper check of the machine is done before use on a patient ensures patient safety. This review will trace all the present safety features in the machine and their evolution.
  1 38,147 8,548
Cleaning and sterilisation of anaesthetic equipment
Chitra Sanjeev Juwarkar
September-October 2013, 57(5):541-550
DOI:10.4103/0019-5049.120152  PMID:24249888
The main purpose of this review article is to bring up what has been known (practiced) about decontamination, disinfection, and sterilisation of anaesthetic equipment. It also discusses how this evidence-based information on infection prevention and control impacts care of patient in routine anaesthesia practice. This review underscores the role played by us, anaesthetists in formulating guidelines, implementing the same, monitoring the outcome and training post-graduate trainees and coworkers in this regard. The article re-emphasises that certain guidelines when followed strictly will go a long way in reducing transmission of hospital acquired infection between patient and anaesthetist or between patients. Anaesthetists do not restrict their work to operating room but are involved in disaster management, interventional radiological procedures and in trauma care. They should ensure that the patients are cared for in clean and safe environment so as to reduce healthcare associated infections (HCAIs) simultaneously taking preventive measures against the various health hazards associated with clinical practice. They should ensure that the coworkers too adopt all the preventive measures while delivering their duties. For this review, we conducted literature searches in Medline (PubMed) and also searched for relevant abstracts and full texts of related articles that we came across. There is much to be learned from the western world where, health care organisations now have legal responsibility to implement changes in accordance with the newer technology to reduce health care associated infection. There is a need to develop evidence-based infection prevention and control programs and set national guidelines for disinfection and sterilisation of anaesthesia equipment which all the institutions should comply with.
  1 21,302 4,669
Medical journal and IJA publication in India
S Bala Bhaskar
September-October 2013, 57(5):436-437
DOI:10.4103/0019-5049.120137  PMID:24249875
  - 3,168 703
Secretary's Message: Indian Journal of Anaesthesia (IJA) at 60 years
MV Bhimeshwar
September-October 2013, 57(5):435-435
  - 2,664 641
The modern integrated anaesthesia workstation
Vijaya P Patil, Madhavi G Shetmahajan, Jigeeshu V Divatia
September-October 2013, 57(5):446-454
DOI:10.4103/0019-5049.120139  PMID:24249877
Over the years, the conventional anaesthesia machine has evolved into an advanced carestation. 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. They offer integrated monitoring and recording facilities and seamless integration with anaesthesia information systems. It is possible to deliver tidal volumes accurately and eliminate several hazards associated with the low pressure system and oxygen flush. Appropriate use can result in enhanced safety and ergonomy of anaesthetic delivery and monitoring. However, these workstations have brought in a new set of limitations and potential drawbacks. There are differences in technology and operational principles amongst the new workstations. Understand the principles of operation of these workstations and have a thorough knowledge of the operating manual of the individual machines.
  - 15,443 4,787
Analysis of oxygen, anaesthesia agent and flows in anaesthesia machine
Rakesh Garg, Ramesh Chand Gupta
September-October 2013, 57(5):481-488
DOI:10.4103/0019-5049.120144  PMID:24249881
The technical advancement in the anaesthesia workstations has made the peri-operative anaesthesia more safer. Apart from other monitoring options, respiratory gas analysis has become an integral part of the modern anaesthesia workstations. Monitoring devices, such as an oxygen analyser with an audible alarm, carbon dioxide analyser, a vapour analyser, whenever a volatile anaesthetic is delivered have also been recommended by various anaesthesia societies. This review article discusses various techniques for analysis of flow, volumes and concentration of various anaesthetic agents including oxygen, nitrous oxide and volatile anaesthetic agents.
  - 6,974 3,028
The anaesthesia gas supply system
Sabyasachi Das, Subhrajyoti Chattopadhyay, Payel Bose
September-October 2013, 57(5):489-499
DOI:10.4103/0019-5049.120145  PMID:24249882
The anaesthesia gas supply system is designed to provide a safe, cost-effective and convenient system for the delivery of medical gases at the point of-use. The doctrine of the anaesthesia gas supply system is based on four essential principles: Identity, continuity, adequacy and quality. Knowledge about gas supply system is an integral component of safe anaesthetic practice. Mishaps involving the malfunction or misuse of medical gas supply to operating theatres have cost many lives. The medical gases used in anaesthesia and intensive care are oxygen, nitrous oxide, medical air, entonox, carbon dioxide and heliox. Oxygen is one of the most widely used gases for life-support and respiratory therapy besides anaesthetic procedures. In this article, an effort is made to describe the production, storage and delivery of anaesthetic gases. The design of anaesthesia equipment must take into account the local conditions such as climate, demand and power supply. The operational policy of the gas supply system should have a backup plan to cater to the emergency need of the hospital, in the event of the loss of the primary source of supply.
  - 34,356 4,097
Anaesthesia gas supply: Gas cylinders
Uma Srivastava
September-October 2013, 57(5):500-506
DOI:10.4103/0019-5049.120147  PMID:24249883
Invention of oxygen cylinder was one of the most important developments in the field of medical practice. Oxygen and other gases were compressed and stored at high pressure in seamless containers constructed from hand-forged steel in1880. Materials technology has continued to evolve and now medical gas cylinders are generally made of steel alloys or aluminum. The filling pressure as well as capacity has increased considerably while at the same time the weight of cylinders has reduced. Today oxygen cylinder of equivalent size holds a third more oxygen but weighs about 20 kg less. The cylinders are of varying sizes and are color coded. They are tested at regular intervals by the manufacturer using hydraulic, impact, and tensile tests. The top end of the cylinder is fitted with a valve with a variety of number and markings stamped on it. Common valve types include: Pin index valve, bull nose, hand wheel and integral valve. The type of valve varies with cylinder size. Small cylinders have a pin index valve while large have a bull nose type. Safety features in the cylinder are: Color coding, pin index, pressure relief device, Bodok seal, and label attached etc., Safety rules and guidelines must be followed during storage, installation and use of cylinders to ensure safety of patients, hospital personnel and the environment.
  - 16,077 3,883
The closed circuit and the low flow systems
S Parthasarathy
September-October 2013, 57(5):516-524
DOI:10.4103/0019-5049.120149  PMID:24249885
A breathing system is defined as an assembly of components, which delivers gases from the anesthesia machine to the patients' airways. When the components are arranged as a circle, it is termed a circle system. The flow of exhaled gases is unidirectional in the system. The system contains a component (absorber), which absorbs exhaled carbon dioxide and it is not necessary to give high fresh gas flows as in Mapleson systems. When the adjustable pressure limiting (APL) valve is closed and all the exhaled gases without carbon dioxide are returned to the patient, the system becomes a totally closed one. Such a circle system can be used with flows as low as 250 to 500 mL and clinically can be termed as low-flow systems. The components of the circle system can be arranged in different ways with adherence to basic rules: (1) Unidirectional valve must be present between the reservoir bag and the patient on both inspiratory and expiratory sides; (2) fresh gas must not enter the system between the expiratory unidirectional valve and the patient; and (3) the APL valve must not be placed between the patient and the inspiratory unidirectional valve. The functional analysis is explained in detail. During the function, the arrangement of components is significant only at higher fresh gas flows. With the introduction of low resistance valves, improved soda lime canisters and low dead space connectors, the use of less complicated pediatric circle systems is gaining popularity to anesthetize children. There are bidirectional flow systems with carbon dioxide absorption. The Waters to and fro system, a classic example of bidirectional flow systems with a canister to absorb carbon dioxide, is valveless and portable. It was widely used in the past and now is only of historical importance.
  - 15,688 5,174