Automatic ventilation with the Ayre's T-piece. A modification of the Nuffield Series 200 ventilator for neonatal and paediatric use

The Newton valve revisited: an in-vitro study of ventilator circuit dead space

A laboratory study was conducted to investigate the volume (length) of the ventilator circuit dead space (VCD) tubing at which dilution of an inspired gas by ventilator driving gas first occurs using three lung models. Various lengths of two VCD tubing materials [Portex (Sims Portex Ltd, Kent, UK) 10 mm bore smooth-walled silicon and Intersurgical (Wokingham, Berks, UK) 22 mm corrugated plastic] were interposed between a T-piece circuit and Nuffield 200 ventilator (Penlon, Abingdon, Oxon, UK) with a Newton valve attached. Dilution of inspired gas by the ventilator driving gas was first detected during ventilation of infant and child lung models when the VCD was 7 ml (6 cm) and 77 ml (102 cm), respectively, using Portex tubing, and 24 ml (6.5 cm) and 105 ml (29 cm), respectively, using Intersurgical tubing. No dilution occurred using the neonatal model. Dilution of the inspired anaesthetic gases by ventilator driving gas may occur in paediatric practice if the VCD volume (length) is inadequate. This risk is greatest in the child.

A new critical incident monitor for use with the paediatric T-piece. In vitro evaluation and clinical experience with the Magtrak Infanta Electronic Respirometer

In vitro studies and clinical evaluation suggest that the Magtrak Infanta Electronic respirometer provides a useful additional critical incident monitor for use with the paediatric T-piece. During ventilation with the Nuffield 200 ventilator and Newton valve it provides early warning of leaks or disconnections in the breathing system, airway obstruction and reduction in fresh gas flow. Some of these events may not be detected by conventional monitors.

Magnetic resonance for the anaesthetist. Part II: Anaesthesia and monitoring in MR units

Anaesthetists are increasingly involved in patient care during magnetic resonance imaging and spectroscopy. This paper describes a system which has been developed for the management of critically ill patients and the conduct of anaesthesia in a magnetic resonance unit with a 1.6 tesla whole body magnet. Difficulties which arise from working in a confined space in a high magnetic field are highlighted. Different approaches to anaesthesia, sedation and the modification of equipment for use in this environment are reviewed. The problems associated with patient monitoring within a magnetic field are discussed and some solutions are suggested. A transport system for critically ill patients is described and a protocol for management is outlined.

A continuous high flow intermittent mandatory ventilation system incorporating a Downs venturi device and a modified Nuffield Series 200 ventilator

Systems for respiratory support are becoming increasingly expensive and complex. Many systems suffer inadequacies when used for spontaneous ventilation. Some modes on newer ventilators are rarely used because of the complex controls and settings. There is no truly universal ventilator that satisfies every intensivist's wishes. CPAP/IMV is becoming accepted as the standard management of many patients with acute respiratory failure and there would be few intensive care units where CPAP/IMV is not used for part of a patient's respiratory support. We describe a cost-effective system that may be used for respiratory support in the spontaneously breathing mode. This system combines a high flow venturi, an efficient humidifier and an inexpensive reliable ventilator that can be used for adult and paediatric patients. The system, primarily for use in patients breathing spontaneously, functions well in patients requiring full ventilation.

The measurement of tidal volumes in spontaneously breathing children during general anaesthesia using a Haloscale infant Wright respirometer

The accuracy of tidal volume measurements made with a Wright Haloscale infant respirometer in children breathing spontaneously during general anaesthesia was assessed by a bench test. The tidal volumes and peak flow rates of 20 spontaneously breathing, anaesthetised children were measured with a pneumotachograph before and during surgery, and similar volumes, at the same flow rates, were delivered by a calibrated syringe simultaneously to the respirometer and a pneumotachograph. The results reveal that the mean (+/- s.d.) peak gas flow rates of children aged 6 years and less, 7.5 (+/- 1.6) and 9.3 (+/- 0.1) l/min before surgery and during surgery respectively, are significantly less than the peak flow rates, 11.3 (+/- 1.0) and 11.9 (+/- 1.5) before and during surgery, respectively, of children aged more than 6 years; and that the respirometer underestimates tidal volume by 10% when the peak flow rate is 11 l/min, and the percentage error in tidal volume estimation by the respirometer increases as the peak gas flow declines below 10 l/min.