Pulmonary vascular resistance (PVR), when expressed in Woods items, offers a standardized measure of resistance to blood circulation inside the pulmonary vasculature. It’s derived by dividing the imply pulmonary artery stress (in mmHg) minus the imply pulmonary capillary wedge stress (additionally in mmHg) by the cardiac output (in liters per minute). The ensuing worth is often expressed as Woods items, the place 1 Woods unit is equal to roughly 80 dyns/cm5. For instance, if a affected person has a imply pulmonary artery stress of 20 mmHg, a imply pulmonary capillary wedge stress of 10 mmHg, and a cardiac output of 5 L/min, the calculated resistance can be (20-10)/5 = 2 Woods items.
Figuring out the stress gradient throughout the pulmonary circulation and normalizing it for cardiac output is essential in assessing pulmonary hypertension and proper ventricular operate. Elevated resistance might point out underlying pulmonary vascular illness, reminiscent of pulmonary arterial hypertension, persistent thromboembolic pulmonary hypertension, or left coronary heart failure. Traditionally, this metric has been instrumental in guiding medical selections associated to medical and surgical administration of those situations. The standardization afforded by Woods items permits for comparability of this resistance throughout totally different sufferers and establishments, bettering the reliability of medical decision-making.
