“Open channel” in BIPAP refers to the ventilator’s ability to keep its valves responsive enough that a patient can breathe freely at any point during the machine’s breathing cycle. Unlike older ventilation modes where the machine locks the patient into a rigid inhale-exhale pattern, an open channel system lets spontaneous breaths happen on top of the mechanical support, without the patient fighting against the ventilator.
How the Open System Works
BIPAP (biphasic positive airway pressure) is a pressure-controlled ventilation mode that switches between two pressure levels on a timed cycle: a higher pressure and a lower pressure. The “open channel” or “open system” concept is about what happens between those switches. In a conventional pressure-controlled mode, the ventilator’s expiratory valve essentially locks shut during the high-pressure phase, preventing any spontaneous breathing effort from getting through. The patient has to wait for the machine.
In an open system, the expiratory valve is controlled with fine precision rather than slamming fully open or fully closed. Dräger, the ventilator manufacturer that pioneered this approach in their Evita line, compared it to carefully regulating water flow through a hose rather than just turning a spigot on and off. This sensitive valve control means air can flow in and out in response to the patient’s own breathing efforts at any moment, whether the ventilator is in its high-pressure phase or its low-pressure phase.
The result is that spontaneous breathing can be superimposed on top of the mechanical ventilation cycle without any confrontation between patient and machine. The ventilator maintains its two pressure levels, but the patient’s diaphragm is free to do additional work within that framework.
BIPAP vs. Conventional Pressure Control
When a patient on BIPAP stops breathing spontaneously (under deep sedation, for example), the mode looks identical to conventional pressure-controlled, time-cycled ventilation. Both deliver the same pressure waveform. The difference only becomes apparent when the patient has any respiratory drive at all. In conventional pressure control, those breathing efforts can meet resistance from closed valves, creating discomfort and poor synchrony. In BIPAP’s open system, those efforts pass through freely.
This distinction matters clinically. BIPAP allows unrestricted spontaneous breathing in any phase of the mechanical ventilator cycle, which means the transition from full ventilator support to partial support to independent breathing can happen more gradually. The patient doesn’t need to be switched to a completely different mode just because they’re starting to breathe on their own.
A Note on Terminology
BIPAP (biphasic positive airway pressure) is not the same thing as BiPAP (bilevel positive airway pressure), even though they sound identical. BiPAP is a trademarked name for a noninvasive machine commonly used for sleep apnea and home respiratory support. It delivers one pressure when you inhale and a lower pressure when you exhale, but it doesn’t involve the open channel concept.
The “open channel” terminology applies specifically to BIPAP as a ventilation mode found on ICU ventilators, particularly Dräger machines. When you see “open channel for BIP” on a ventilator screen or in documentation, it’s referring to this biphasic mode with its open valve system, not the home breathing machine.
Why Open Channel Ventilation Matters
Allowing spontaneous breathing throughout the ventilation cycle produces several measurable benefits. Studies comparing BIPAP to other ICU ventilation modes in patients with acute respiratory distress syndrome (ARDS) have found that BIPAP can improve oxygenation, support better cardiovascular function, and improve lung mechanics. Patients on BIPAP also tend to require fewer days of sedation and shorter overall durations of mechanical ventilation compared to other pressure-controlled modes.
The sedation reduction is a direct consequence of the open system. When a patient can breathe spontaneously without fighting the ventilator, there’s less need to sedate them into compliance with the machine’s rhythm. Less sedation means more wakefulness, earlier participation in recovery, and a shorter path to getting off the ventilator entirely. The open channel, in other words, isn’t just an engineering detail. It changes the trajectory of a patient’s ICU stay.
Spontaneous breathing also keeps the diaphragm active. During conventional mechanical ventilation where the machine does all the work, the diaphragm can weaken rapidly from disuse. By preserving some level of spontaneous effort, BIPAP’s open system helps maintain diaphragm function, which is critical for eventually breathing independently again.
What “Open” Looks Like in Practice
On a Dräger ventilator, activating BIPAP mode with the open channel means the clinician sets two pressure levels (often labeled P-high and P-low) along with the time spent at each level. The ventilator cycles between these pressures automatically. But unlike a closed system, the patient’s own breaths are visible on the pressure and flow waveforms as small fluctuations layered on top of the machine’s pattern. These fluctuations confirm that the open channel is doing its job: the patient is breathing freely within the mechanical framework.
If the patient’s spontaneous breathing disappears (say, due to deeper sedation or a change in neurological status), the waveform smooths out and the mode functions as straightforward pressure-controlled ventilation. No settings need to change. The system simply adapts to whatever the patient is contributing at any given moment.