Measuring the mechanical input impedance of the respiratory system with breath-driven flow oscillations

The technique of oscillometry for measuring the mechanical input impedance of the respiratory system is gaining traction as a clinical diagnostic tool, but the portability of existing commercially available devices is limited by the size and weight of oscillator motors and power supplies. We show that impedance can be measured by oscillations in mouth pressure and flow generated by mucus-clearing devices that are powered by the subject’s own respiratory flow. This principle might thus be employed in lightweight ambulatory oscillometry devices.

Download Full-text

A modified measurement of respiratory resistance by forced oscillation during normal breathing

Journal of Applied Physiology ◽

10.1152/jappl.1975.39.2.305 ◽

1975 ◽

Vol 39 (2) ◽

pp. 305-311 ◽

Cited By ~ 16

Author(s):

D. C. Stanescu ◽

R. Fesler ◽

C. Veriter ◽

A. Fans ◽

L. Brasseur

Keyword(s):

Flow Rate ◽

Respiratory System ◽

Obstructive Lung Disease ◽

Forced Oscillation ◽

Forced Oscillation Technique ◽

Good Reproducibility ◽

Respiratory Resistance ◽

Normal Breathing ◽

Respiratory Flow ◽

Mouth Pressure

We have modified the measurements of the resistance of the respiratory system, Rrs, by the forced oscillation technique and we have developed equipment to automatically compute Rrs. Flow rate and mouth pressure are treated by selective averaging filters that remove the interference of the subject's respiratory flow on the imposed oscillations. The filtered mean Rrs represents a weighted ensemble average computer over both inspiration and expiration. This method avoids aberrant Rrs values, decreases the variability, and yields an unbiased mean Rrs. Rrs may be measured during slow or rapid spontaneous breathing, in normals and in obstructive patients, over a range of 3–9 Hz. A good reproducibility of Rrs at several days' interval was demonstrated. Frequency dependence of Rrs was found in patients with obstructive lung disease but not in healthy nonsmokers.

Download Full-text

Diagnosis of TIA (DOT) score – design and validation of a new clinical diagnostic tool for transient ischaemic attack

BMC Neurology ◽

10.1186/s12883-016-0535-1 ◽

2016 ◽

Vol 16 (1) ◽

Cited By ~ 12

Author(s):

Dipankar Dutta

Keyword(s):

Diagnostic Tool ◽

Transient Ischaemic Attack ◽

Clinical Diagnostic ◽

Ischaemic Attack

Download Full-text

Diurnal variations of respiratory system resistance and compliance derived from input impedance in asthmatic children

Respiration Physiology ◽

10.1016/s0034-5687(00)00171-7 ◽

2000 ◽

Vol 123 (1-2) ◽

pp. 101-108 ◽

Cited By ~ 9

Author(s):

W Tomalak ◽

A Elbousefi ◽

R Kurzawa ◽

Z Doniec

Keyword(s):

Respiratory System ◽

Input Impedance ◽

Diurnal Variations ◽

Asthmatic Children ◽

Respiratory System Resistance

Download Full-text

In-phase rejection requirements for measuring respiratory input impedance

Journal of Applied Physiology ◽

10.1152/jappl.1984.56.3.804 ◽

1984 ◽

Vol 56 (3) ◽

pp. 804-809 ◽

Cited By ~ 23

Author(s):

R. Peslin ◽

P. Jardin ◽

C. Duvivier ◽

P. Begin

Keyword(s):

Pressure Difference ◽

Input Impedance ◽

Pressure Transducer ◽

Absolute Pressure ◽

Impedance Measurements ◽

Differential Pressure Transducer ◽

Rejection Ratio ◽

Respiratory Flow ◽

In Series ◽

The Subject

Respiratory flow is commonly obtained by measuring the pressure difference across a pneumotachograph. When respiratory input impedance is studied, that pressure difference may be very small with respect to the absolute pressure swings inside the pneumotachograph. Then the in-phase rejection of the differential pressure transducer is expected to markedly influence the accuracy of the data. The problem was investigated by computer simulation and by measurements on a mechanical analog of the respiratory system made of a resistance, an inertance, and a compliance arranged in series. Both studies demonstrated that comparatively small differences in the volumes of the chambers or in the lengths or diameters of the connecting tubes led to artifactual frequency dependence of resistance and serious misestimation of compliance and inertance. Errors were larger when the resistance of the pneumotachograph was smaller and the impedance of the subject larger. In practice, with usual pneumotachographs accurate impedance measurements require using the most symmetrical transducers presently available (common-mode rejection ratio of about 70 dB at 30 Hz).

Download Full-text