There are literature about acute, but what about chronic (long term)
Good question, We need to define what long term means here ? There is little data on hemodynamic parameters in long term ventilated patients for many reasons -1. the intensity and invasiveness of monitoring usually diminishes in long term ventilated patients 2. Acute phase of illness is more dynamic and there is ussually a problem if a long term ventilated patient requires extraordinary monitoring and the usefulness of ongoing support will have to re-looked based on individual patient situation. 3. Equally long term ventilated patients may have neuromuscular disorder/s which can themselves often involve the cardiovascular system 4. patients may have preexisting cardiovascular issues and we often don't have premorbid data for many of these long term ventilated patients
Having said that , long term ventilation can significantly impact the pulmonary vasculature and the right ventricle and consequently systemic hemodynamics. The effects of long ventilation primarily on systemic circulation and the left heart are unclear and prospective studies are worth it but tricky to do as there are not many patients who get ventilated for months to years. POSITIVE PRESSURE VENTILATION IS NON-PHYSIOLOGICAL AND IMPACTS EVERY ORGAN SYSTEM INCLUDING CARDIOVASCULAR AND WHEN IT COMES TO VENTILATION "SHORTER IT LASTS, THE BETTER"
In most cases long term mechanical ventilation is being applied as noninvasive ventilation (NIV). The only paper I am aware of studying pulmonary hemodynamics in the long term is the one from Schönhofer et al. Thorax 2001. The authors found a reduction of PA pressure and PVRI over a period of one year NIV use in patients with restrictive ventilatory disorders (not in COPD patients).
Regarding the acute setting I would recommend the paper from Thorens et al. ERJ 1997. They found an improved RV function with accompanying decrements in PA pressure.
Keeping these results in mind, recommendation "the shorter, the better" can not be applied to population of patients with chronic ventilatory insufficiency.
However, it is of course true, that mechanical ventilation always needs to be kept to the shortest time possible.
Agree for ventilator dependent patients -there are not many options and we need to wear the risks of PPV..
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