Acoustic tool to test status of respiratory ventilation function

Diving renders negative influence on human respiratory system especially when oxygen breathing apparatus aimed for military divers is used. Spirometry indexes have poor sensitivity to toxic effect of hyperbaric hyperoxia. Objective is to develop new acoustic instrumentation for revealing minimum impairments of lung function in oxygen divers. The apparatus has been designed which is based on analysis of forced expiratory tracheal noise duration (FETND). This apparatus contains acoustic sensor, input device, portable personal computer and specially designed software. 48 divers before and after single shallow water dive in oxygen closed-type breathing apparatus were tested by means of this acoustic tool. After dive a significant drop of spirometric indexes forced vital capacity (FVC), forced expiratory volume in 1 sec (FEV1) over the group as a whole was found. The significant increase of individual FETND, exceeding the natural variability limit, was found in 10 subjects (20.8%). Three of them during dive had respiratory symptoms characteristic for initial manifestations of pulmonary oxygen poisoning. Two of them had essential drop of FEV1. The asymptomatic reversible increase of FETND in the rest 7 divers was interpreted as a sign of obstructive impairments caused by hidden phase of hyperbaric hyperoxia effect. Thus developed acoustic tool is useful to monitor ventilation function of lungs in military/civil divers and other persons working in harmful gas media such as firefighters, astronauts and so on.