A modified MIE Superlite exhaust valve incorporating a positive pressure safety relief valve

Most scavenging systems incorporate safety devices to protect the patient against sudden positive and negative pressure surges. If full protection is to be guaranteed, positive pressure relief devices should be positioned as close as possible to the patient and, preferably, should form an integral part of the expiratory valves of anaesthetic systems and ventilators. One such safety device is described in this paper.