An implantable impedance pneumograph monitor for detection of diaphragm contraction and airway obstruction during diaphragm pacing

• Published in: Medical & biological engineering & computing Vol. 37; no. 2; pp. 162 - 168
• Main Authors: SCHMIT, B. D, KAYYALI, H, MAKOVOS, B, MORTIMER, J. T
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer 01.03.1999; Springer Nature B.V
• Subjects: Airway management; Airway Obstruction - diagnosis; Animals; Bioelectric potentials; Biological and medical sciences; Biomedical equipment; Diaphragm - physiopathology; Diaphragms; Dogs; Electric Impedance; Electric Stimulation; Electric variables measurement; Electrodes; Electrodes, Implanted; Implants (surgical); Investigative techniques, diagnostic techniques (general aspects); Medical sciences; Monitoring, Physiologic - instrumentation; Muscle Contraction; Pathology. Cytology. Biochemistry. Spectrometry. Miscellaneous investigative techniques; Respiratory system; Spurious signal noise; Fissipedia; Carnivora; Impedancemeter; Implant; Electrical properties; Respiratory disease; Lung; Respiratory system; Muscle contraction; Obstruction; Respiratory tract; Vertebrata; Mammalia; Animal; Surgery; Diagnosis; Diaphragm; Dog; Monitoring
• ISSN: 0140-0118; 1741-0444
• DOI: 10.1007/BF02513283

Impedance pneumography signals were characterised during diaphragm pacing using stimulating and recording electrodes placed on the abdominal surface of the diaphragm. These measurements were useful for the detection of muscle contraction without confounding effects from stimulus artifacts. Impedance pneumography signals were measured using 23 epimysial electrodes implanted in seven dogs with 1-5 experiments on each electrode. The polarity of the change in impedance associated with diaphragm pacing differed for each recording electrode and its configuration. Thirty-four of 57 cases produced increased impedance, 11 produced decreased impedance and the remaining 12 depended on the level of diaphragm activation. Impedance pneumography signals were useful for detecting complete airway obstruction. The mean difference between the impedance measured during open and obstructed airway conditions was 80% of the open airway impedance signal. The difference between open and obstructed airway impedance measurements was a mean of 2.3 times larger with a recording electrode on the same hemidiaphragm as the stimulating electrode, compared to an electrode placed on the opposite hemidiaphragm (p < 0.05, paired t test, four dogs). In addition, the differences between open and completely obstructed airways were a mean of 2.8 times larger when the second recording electrode was placed on the thorax at the fifth intercostal space, compared to the ninth intercostal space (p < 0.05, two-factor ANOVA, one dog, two replicates). It was concluded that impedance pneumograph circuitry could be incorporated into an existing diaphragm pacer using electrodes placed on the diaphragm to provide valuable measurements of the function of the device.