plethysmografie

Plethysmography is a family of noninvasive techniques used to measure changes in volume within an organ or region of the body. The methods detect small shifts in volume that accompany blood flow, air movement, or tissue expansion, by observing changes in electrical impedance, light absorption, or displaced air. Plethysmography is used in clinical physiology, respiratory medicine, and vascular assessment.

Common modalities include impedance plethysmography, air or volume plethysmography, and optoelectronic or photoplethysmography. Impedance plethysmography uses electrical impedance to infer limb volume changes associated with arterial pulsations and is employed to study venous insufficiency and hemodynamic changes. Air or volume plethysmography measures displacement of air within a sealed chamber and underpins whole-body plethysmography for lung function and air displacement plethysmography for body composition, as in devices like the Bod Pod. Photoplethysmography uses light to detect changes in microvascular blood volume and is widely used in pulse oximetry and wearable heart-rate monitors. Optoelectronic plethysmography can map chest wall movements to estimate thoracoabdominal volumes.

Applications in respiratory medicine include measurement of lung volumes, airway resistance, and assessment of hyperinflation in obstructive diseases. Body plethysmography (the body box) provides accurate thoracic gas volume and total lung capacity, aiding differentiation of obstructive and restrictive patterns. In vascular and lymphatic medicine, plethysmography assists evaluation of limb perfusion, venous outflow, and edema; impedance and photoplethysmography are used in monitoring and research contexts.

Advantages of plethysmography include noninvasiveness and versatility across settings. Limitations involve sensitivity to movement, the need for proper calibration, and device-specific variability in measurements.