![]() ![]() It was calculated that 30 l/min of NHF reduced the rebreathing of CO2 from anatomical dead space by 45%, which is equivalent to the 20% reduction in tidal volume that was observed. CO2 entrainment increased tidal volume close to baseline with 1% CO2 and greater than baseline with 3% CO2 by 155 ml, SD 79 ( P = 0.0004), without affecting the respiratory rate. NHF with room air reduced tidal volume by 81 ml, SD 25 ( P < 0.0001) from a baseline of 415 ml, SD 114, but did not change respiratory rate tissue CO2 and O2 remained stable, indicating that gas exchange had been maintained. Carbogen gas mixture was entrained into 30 l/min of NHF to obtain three levels of inspired CO2: 0.04% (room air), 1%, and 3%. In nine healthy males, ventilation was measured during sleep using calibrated respiratory inductance plethysmography (RIP). The authors hypothesized that the decrease in tidal volume during NHF is due to a reduction in carbon dioxide (CO2) rebreathing from dead space. It was previously observed that NHF reduces the tidal volume but does not affect the respiratory rate during sleep. Nasal high flow (NHF) is an emerging therapy for respiratory support, but knowledge of the mechanisms and applications is limited. Keywords: Physiological dead space, anatomical dead space, alveolar dead space, capnovolumetry, volumetric capnography. Determination of the volume of dead space is the significant criterion for diagnostic and predicting the outcome of a number of diseases. In pathology, the volume of the alveolar space and, consequently, physiological dead space can increase significantly. The volume of the alveolar dead space is the difference of volumes of the physiological and anatomical dead spaces. The volume of anatomical dead space can be determined using the equal area method proposed by W.S. The volume of physiological dead space is calculated using the C. ![]() The article describes methods for determining the volume of dead spaces using the capnovolumetry. The anatomical and alveolar dead spaces jointly together form the physiological dead space. ![]() The article provides information on the lung dead space – a part of the respiratory volume that does not participate in gas exchange. ![]()
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