Capnographic parameters of the breathing pattern in healthy adults and patients with psychogenic dyspnea

Parameters of 5-min capnogram in 106 healthy humans (H group) were compared with those in 30 patients with psychogenic dyspnea (P group). Averaged values of end-tidal fractional concentration of carbon dioxide (FetCO₂) and respiration rate (f) were determined. The structure of the respiratory cycle was estimated by the ratio of the expiratory time to the total respiratory cycle time $\left( {R_{CO_2 } } \right)$ . The degree of breath arrhythmia was estimated using the coefficient of variation (CV) of $R_{CO_2 }$ , recorded during the 5-min capnography $\left( {R_{CO_2 } } \right)$ . The difference in the capnograms of H group and P group was reliable for all parameters, except for $R_{CO_2 }$ (structure of the respiratory cycle). For H group, FetCO₂ was 5.24 ± 0.36 vol %, and for P group, it was 4.07 ± 0.47 vol %. For H group, f was 14.3 ± 3.74 br./min; and for P group, it was 17.9 ± 4.50 br./min. For H group, $CVR_{CO_2 }$ was 8.91 ± 2.16%; and for P group, it was 12.7 ± 3.14%. The comprehensive parameter, which includes all three characteristics of the breathing pattern, such as a decrease in FetCO₂, an increase in f, and disorders of the breathing rhythm, appeared to be the most informative indicator of psychogenic dyspnea. It was shown that capnography with automatic processing of the breathing pattern is an objective method for studying the mechanisms of psychogenic dyspnea.