@Copyright 1/24/96 IPPA - La Paz, Bolivia
HIGH ALTITUDE PATHOLOGY INSTITUTE (IPPA). La Paz, Bolivia
A glass chamber with a plastic covered wooden floor (2.75 m long, 1.45 m wide and
2.0 m high) was constructed in our laboratory in June 1992 (3510 m; barometric pressure = 494
mmHg), in which subjects can be comfortable for many hours while breathing different
oxygen mixtures simulating different altitudes within the range of the earth's atmosphere.
The side door has a lock (0.88 m long x 0.62 m wide and 2.0 m high), which
enables the entrance or exit during operation, without significant variation of the oxygen
concentration inside the chamber. Hence, arterial blood samples can be drawn, or any
other medical assistance, can be granted.
The temperature and humidity are kept constant by an air conditioning unit and heater.
Carbon dioxide (CO2) can be removed by recirculating the internal air through a soda lime
absorber. Oxygen (O2), nitrogen (N) and/or carbon dioxide (CO2) can be injected as
required, in order to simulate different altitudes and gas tensions. Oxygen concentrations
are monitored by an oxygen analyzer. A polyethylene tube 3 mm in diameter is also
available to take air samples in order to measure inspired gas tensions, as a double check.
Finger pulse oximetry is connected via serial port to a personal computer, for sampling
every 5 seconds and averaging every 5 minutes. A one-way valve is connected by a
mouthpiece to the outside, where a pneumotachograph, analogically connected to a
computer records expiratory ventilation along with electrocardiogram. Douglas bags
recollect the expired gas for CO2 and O2 analyses in a radiometer blood gas analyzer. All
data is registered in a central computer for future analysis. Inside, a sitting down subject,
can read, listen to a radio, watch television or talk on the phone. This multi-purpose
chamber permits environmentally controlled studies and treatment of patients with acute
and chronic hypoxia at high altitude in an accurate and homelike way.