The BiPAP S/T-D by Respironics, Inc. is a device used to provide non-invasive pressure support and CPAP via mask, usually nasal. BiPAP stands for Bi-level Positive Airway Pressure. The BiPAP aids oxygenation and ventilation in cases of sleep apnea or ventilatory muscle fatigue. It has also been applied to prevent the more invasive procedures of intubation or tracheostomy.

Pictured on the right, the top section contains the Control Unit which houses a blower, pressure controlling valve, and pneumotach. On the bottom left is a DCP or Detachable Control Panel. The identical controls are found behind a panel on the back of the Control Unit. The DCP is for monitoring the patient at a distance as in a sleep study. On the right is an Airway Pressure Monitor that has a High and Low Pressure alarm, Inadvertent OFF, Alarm Delay, and Low Disable or alarm silence.

The Control Unit delivers a continuous flow of gas to the patient, part of which leaks out around the mask. This leak is estimated by the pneumotach and compensated for by the pressure controlling valve. The unit senses changes in flow between the patient's inspiration and expiration and cycles between IPAP and EPAP accordingly.The minimum length of IPAP is 180 ms and the minimum length of EPAP is 500 ms. IPAP is triggered by the patient when the pneumotach measures an increase in flow of 40 mL/sec over the leak flow for 30 milliseconds. IPAP ends when the measured inspiratory flow equals the leak flow or after 3 seconds have elapsed (except in Timed Mode).

The detachable control panel (DCP) pictured on the right includes the following. The top left knob selects the display values. Estimated Exhaled Tidal Volume has been selected and reads 740 mL. The bottom left knob is the Mode selector. The remaining controls are for IPAP, EPAP, BPM, and % IPAP Time. Push the controls knobs in to turn.

Display values are IPAP (range 0 - 25 cm H20), EPAP (range 0 - 25 cm H20), Estimated Exhaled Tidal Volume (range 0 - 3999 mL), and Estimated Leak (range 0-60 L/min). Estimated Exhaled Tidal Volume is within +/ - 25% if the leak is stable. If the Estimated Exhaled Tidal Volume display flashes during cycling, the volume indicated is inaccurate due to a sudden increase in the leak by 15 LPM. If the system can compensate for the new degree of leak, the display will stop flashing. If flashing continues for 10 - 15 cycles, the system is unable to compensate for that degree of leak. If the unit is unable to detect the change in air flow from IPAP to EPAP, the Est Tidal Volume display may flash, display "OFL", or

display "000". "OFL" may also be displayed for the other selections if less than 1.0 cm H20 pressure is measured by the internal pressure transducer.

The modes available on the BiPAP are CPAP, Pressure Support and CPAP, and time triggered pressure controlled breaths with CPAP. Pressure support is called IPAP. CPAP is called EPAP. The 5 modes are IPAP, EPAP, Spontaneous, Spontaneous/Timed, and Timed. In either the IPAP or the EPAP mode, the patient receives CPAP. In Spontaneous mode, the patient triggers all inspirations which are pressure supported. EPAP determines the level of CPAP.

In Spontaneous/Timed (S/T) the BPM control is active and synchronized breaths are given. If the patient doesn't initiate a breath within the set BPM interval, a time triggered inspiration is given and the BPM indicator illuminates. In Timed Mode, the BPM and the % IPAP Time (to the right of BPM, see above) controls are both functional. The % IPAP Time determines what percent of the respiratory cycle is for inspiration.The BPM indicator is not active.

The Airway Pressure Monitor should be turned on whenever the BiPAP unit is in operation. An Inadvertent OFF alarm warns if the Monitor is not turned ON and the circuit pressure is above 5 cm H20. The High Pressure audiovisual alarm, range 2 - 50 cm H20, activates each time circuit pressure exceeds the high pressure alarm setting. Self-corrects if alarm condition resolved. The Low Pressure audiovisual alarm, range 2 - 25 cm H20, activates if the airway pressure does not rise above the Low Pressure setting for the time interval set on the Delay. The Delay interval is adjustable from 0.5 - 60 seconds.

The Low Pressure alarm may be silenced for 20 or 60 seconds by the Low Disable Control. An internal switch sets the interval at either 20 seconds or 60 seconds. The silence period may be extended by pressing the button again near the end of the delay interval. The Replace Battery Warning audiovisual alarm activates when the battery voltage is below 6.6 volts. Can only silence by replacing battery or turning airway pressure monitor OFF.

BiPAP applied using a nasal mask.
Monarch nasal mask
Full face mask with the "quick removal" strap
Adams head gear with nasal pillows and chin strap.
Nasal pillows
More nasal pillows.
Nasal masks, Gel Mask, and Monarch nasal mask.

For the latest ventilatory support devices from Respironics, check out their website.