Dynamic pressure–volume curve showing “beaking”
What does pressure–volume (P–V) curve describe?
What is the goal of using P–V curves?
Does it improve outcome?
What are inflection points on the P–V curve?
How can one select appropriate PEEP?
What are the benefits of adequate PEEP?
Pressure–volume curves describe the mechanical behavior of the lungs and chest wall during inspiration and expiration, giving the clinician a sense of the patient’s lung and chest wall compliance (Fig. 73.1). It has been studied in many disease states but most extensively in patients with ARDS. Different than static pressure–volume curves, dynamic pressure–volume curves are obtained during actual gas flow through the respiratory cycle, and add the variable of airway resistance to the equation . Many ICU and OR ventilators currently come with the built-in capability to record constant flow dynamic pressure–volume curves.
The reason clinicians initiated the analysis of pressure–volume curves in different disease scenarios was to assess individual patient’s respiratory mechanics and possibly customize the ventilator settings according to their findings. Ultimately, the goal was to optimize the ventilator settings for each patient and improve compliance, thus protecting them from ventilator-induced lung injury.
Despite the initial enthusiasm and excitement that the use of P–V curves could improve morbidity and mortality, it has not been borne out in studies. Difficulties in measurements and improper use of the information may have been contributors to the lack of evidence and have raised questions about the clinical usefulness of this method. Since the development of new ventilators with the built-in capacity to measure dynamic pressure–volume curves, promising research has been ongoing and hopefully will result in the initially desired clinical outcomes.
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