Volumetric capnography (VC) provides valuable insights into lung collapse-recruitment physiology in a noninvasive and real-time manner, and thus lends itself to monitoring cyclic recruitment maneuvers at the bedside. Lung recruitment is a pressure-dependent phenomenon. Positive end-expiratory pressure (PEEP) needed to prevent the lung from recollapse after the recruitment maneuver is higher in patients with pulmonary diseases. Lung recruitment improves CO2 elimination by increasing the area of the alveolar-capillary membrane available for gas exchange. Lung recruitment affects the last two processes, mainly as a consequence of opening previously collapsed pulmonary capillaries and alveoli. Data from VC during lung recruitment can be grouped and analyzed in four principal ways according to CO2 kinetics: lung perfusion; gas exchange; lung ventilation; and gas transport within the airways. The sensitivity and specificity of non-invasive VC can be enhanced by supplemental invasive measurements of gas exchange.