From Waveform to Bedside: A Practical Approach to Mechanical Ventilation

The ventilator waveform is not just a tracing—it's a story about what's happening inside the patient's lungs. In a preview of his CHEST 2026 presentations, one intensivist walks through a case-based approach to understanding waveforms, desynchrony, and the specific challenges of ventilating status asthmaticus. The guiding philosophy, borrowed from the Vent Course's founder Bert Lee, is simple: "We're just trying to prevent death and torture." Everything else follows from that.

The Physics First, Then the Patterns

The approach rests on three foundational concepts. First is Ohm's law applied to ventilation: delta pressure equals flow times resistance. The driving pressure between the ventilator (airway pressure) and the alveolus (alveolar pressure) determines how much air moves. Second is the equation of motion: airway pressure equals flow times resistance plus volume over compliance plus total PEEP. This single equation explains nearly everything visible on a waveform. Third is the equation of natural decay, which gives us the time constant—the rate at which the lung empties during expiration.