Abstract—Capnography refers to the continuous and noninvasive measurement of carbon dioxide (CO2) concentration in respiratory gases and it provides a real-time assessment of ventilatory status. The aim of this paper is to demarcate the inspiratory and expiratory segments of a time capnogram using data from respiratory flow rate waveforms. The measurements were obtained from 38 infants under mechanical ventilation in intensive care unit. A comparison was made between CO2 and respiratory flow waveforms to determine the inspiratory segment (phase 0) and the expiratory segment and its subdivisions (phases I, II, and III). The coefficients of determination were 0.83 (p < 0.001) for end-tidal CO2 pressure and inspiratory flow during rebreathing; and 0.97 (p < 0.001) during the weaning process. The end of expiration almost coincides with the downslope of the CO2 waveform in the capnograms when there is no rebreathing, during the weaning process. However, in the presence of rebreathing, the alveolar plateau is prolonged and includes a part of inspiration, in addition to the expiratory alveolar plateau.

Index Terms—Capnogram, invasive mechanical ventilation, monitoring device, respiratory flow rate.

The authors are with the Biomedical Engineering Programme, Parana Federal University of Technology (UTFPR), and the Pediatric Intensive Care Unit of Pequeno Principe Hospital, Parana, Brazil (e-mail: carmen_enge@yahoo.com.br, gewehrs@utfpr.edu.br).

 

Cite:C. C. Rasera and P. M. Gewehr, "Association between Capnogram and Respiratory Flow Rate Waveforms during Invasive Mechanical Ventilation," International Journal of Bioscience, Biochemistry and Bioinformatics vol. 3, no. 2, pp. 80-84, 2013.