You pick up the morning ward round notes and one patient is on day four of ventilation with numbers that are not moving. Oxygenation is marginal, the lung compliance has not improved, and the team is starting to repeat the same management from the day before. This is a situation I see regularly in our ICU, and the instinct to simply wait and continue is often the wrong one.
The ventilator settings are the first place I look, because they are the most immediately actionable. Here is the order in which I think through them.
PEEP is usually the first thing I re-examine
In a patient with ARDS or significant atelectasis, PEEP is the most powerful tool you have for improving oxygenation, and it is also the most commonly under-titrated setting. Many patients arrive on a PEEP of 5 that was set on the night shift and never revisited. The question I ask is: has the PEEP been titrated to this patient, or just left at a standard starting value?
A simple recruitment manoeuvre followed by a decremental PEEP trial gives you real information about where the optimal PEEP is for that patient on that day. It takes time, but it is more useful than incrementally increasing the FiO2 and hoping. I also look at the driving pressure. If the driving pressure is high, something is wrong with the relationship between PEEP, tidal volume, and lung compliance, and simply adding more PEEP without thinking about it can make things worse.
Tidal volume and plateau pressure come next
Lung-protective ventilation has been standard for long enough that everyone knows the 6 mL/kg IBW figure. But in practice, I still see patients receiving 8 or even 9 mL/kg because the body weight used was actual rather than ideal, or because nobody recalculated it after the patient was intubated on a busy night. I always verify the tidal volume against the correct IBW.
Plateau pressure above 30 cmH2O tells me the lung is being stressed. That is the first thing to bring down. Driving pressure above 15 is similarly concerning. If both are elevated and the patient is not improving, I start asking whether lung-protective ventilation is actually being delivered, or just ordered.
I-E ratio and flow settings are often overlooked
For a patient with obstructive physiology, whether from COPD or severe asthma, the I-E ratio matters enormously. An insufficient expiratory time leads to dynamic hyperinflation and breath stacking, which can be subtle on the monitor but catastrophic in terms of haemodynamics and work of breathing. If the patient looks like they are fighting the ventilator, or if there is unexplained hypotension in a ventilated patient, this is one of the first things I check.
The fix is usually straightforward: reduce the respiratory rate, increase the I-E ratio to allow more expiratory time, and look at the flow-time waveform to confirm that expiration is completing before the next breath triggers.
Mode of ventilation and patient-ventilator synchrony
A patient who is not improving sometimes needs a different ventilator mode, not just adjusted settings within the current one. If the patient is making significant spontaneous efforts and is on volume-control, consider whether pressure support or SIMV would better match their respiratory pattern. Asynchrony between the patient and the ventilator increases work of breathing, causes patient distress, and can cause ventilator-induced lung injury in its own right.
I look at the waveforms. A double-triggered breath, a flow mismatch, or an inspiratory effort that fails to trigger the ventilator each tells a different story and points to a different adjustment. This takes a few minutes to do properly and saves a great deal of time in the days that follow.
What I tell residents about ventilator management
The ventilator is not a background task. It requires the same active thinking as the drug chart or the fluid balance. A patient on day four with unchanged settings is not being managed, they are being observed. Titrate to the patient’s current physiology, look at the waveforms properly at least once a day, and always ask whether the numbers you are seeing are the ones you are actually aiming for.