Impedance measurement of tidal volume and ventilation

Hamilton, Lyle H.; Beard, James D.; Kory, Ross C.

doi:10.1152/jappl.1965.20.3.565

Cited by 41 publications

(11 citation statements)

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“…Simultaneous recordings of the signals from the recorder and from the spirometer gave information about the correlation between A V and AlZl. We found a significant correlation between the peak values of AlZl and A V in agreement with other studies (Hamilton, Beard & Kory, 1965;Grenvik et al, 1972;Newton et al, 1983). However, during one respiratory cycle the relationship between AlZl and A V was not linear, and very different values of AlZl corresponded to the same A V during inspiration and expiration.…”

Section: Discussionsupporting

confidence: 93%

Impedance pneumography for long‐term monitoring of respiration during sleep in adult males

Larsen

Christensen

Oxhøj

et al. 1984

Clinical Physiology

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Impedance pneumography is based on the relationship between respired volume (delta V) and changes of transthoracic impedance (delta/Z/) during breathing. The impedance signal, the relationship between delta V and delta/Z/ and the success rate during long-term recording was studied in 11 healthy adult males, aged 21-46, by a portable tape recorder (Oxford Medilog 4-24). The signals from the tape recorder (delta/Z/), and from a spirometer (delta V) were recorded simultaneously on a mingograph during normal breathing, apnoea, deep sighs, and coughs. The relationship between delta V and delta/Z/ was also analysed on an X-Y recorder. Delta/Z/ was delayed in relation to delta V and during one respiratory cycle the relationship was not linear. The time constant of delta/Z/ was 6 s. A significant correlation was found between peak values of delta V and delta/Z/ for 0 less than delta V less than 2.5 litres. Long-term recording of delta/Z/ during one night's sleep resulted in a success rate of 63-100%, mean 90%. Invalidation of the impedance signal was caused by overloading (81%) and interference (19%). It is concluded that the Medilog respiratory recorder enables determination of respiratory frequency, periods of apnoea and a semiquantitative estimate of volume, but artifacts may invalidate the signal.

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Section: Discussionsupporting

confidence: 93%

Impedance pneumography for long‐term monitoring of respiration during sleep in adult males

Larsen

Christensen

Oxhøj

et al. 1984

Clinical Physiology

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“…diameter stainless steel tube soldered longitudinally to the centre of the strip to make a ridge. These are similar to the electrodes described by Hamilton, Beard, and Kory (1965). The position of the electrodes is important (Baker, Geddes, and Hoff, 1966), and the best position in each patient is found by experiment.…”

supporting

confidence: 54%

Impedance pneumograph studies in left ventricular failure

Tanser¹

1967

Thorax

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Tidal volume can be measured by recording the chang-in impedance of the thorax caused by breathing. Thus breathing can be recorded quantitatively from two electrodes placed on each side of the chest. The method is especially useful in breathless patients and studies of breathing patterns during sleep. A patient with a long circulation time due to left ventricular failure had periodic breathing both awake and asleep. When asleep the respiratory minute volume was considerably reduced, and there were long apnoeic periods. This was associated with a rise in mean right atrial pressure until the patient woke with an attack of paroxysmal dyspnoea. The right atrial pressure dropped to normal when the patient breathed more regularly. Anoxia probably caused the rise in right atrial pressure. Periodic breathing disappeared when the circulation time shortened after treatment of the heart failure. The possible mechanism of these changes is discussed.Until recently it has been difficult to study breathing quantitatively without influencing its pattern by the method of recording. Face The potential difference developed across the chest. measured at a second pair of electrodes, is amplified by a high frequency amplifier, and rectified and smoothed to give a direct voltage. This voltage is made equal to a reference voltage at the end of expiration. Inspiration increases the resistivity of the tissues, causing the direct voltage to exceed the reference voltage. This difference is amplified and displayed through the pen recorder, and is proportional to the inspired volume. The electrodes used were brass strips, 6-25 x 1-25 cm., with a 0-2 cm. diameter stainless steel tube soldered longitudinally to the centre of the strip to make a ridge. These are similar to the electrodes described by Hamilton, Beard, and Kory (1965). The position of the electrodes is important (Baker, Geddes, and Hoff, 1966), and the best position in each patient is found by experiment. In this patient, the two electrodes were placed longitudinally on either side of the mid-axillary line with the lower poles at the level of the ziphisternum. They were secured with adhesive plaster. The system is calibrated at the start and finish of each period of observation with a low resistance spirometer recording through a potentiometer mounted on the pulley. The calibration is affected by the position of the patient, which must remain the same during recording. The change in impedance is related in a curvilinear way to the tidal volume (Fig. 1). With optimum placing of the electrodes this curve approximates to a straight line. In this patient the correlation was approximately r= 0-97. 550

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“…Electrodes are attached to the chest wall in such a way that a rapidly oscillating electrical signal can be passed across the thorax from side-to-side and/or from front to back. The size of the signal decreases as impedance increases with inspiration and increased intrathoracic gas volume (Hamilton, Beard & Kory, 1965). Other factors such as pulmonary blood volume and lung water also affect thoracic impedance but these do not show regular oscillations in time with breathing and the ventilatory signal can be recognized easily.…”

Section: Theoretical Problemsmentioning

confidence: 99%

Ventilation.

Sterling¹

1979

Brit J Clinical Pharma

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Impedance measurement of tidal volume and ventilation

Cited by 41 publications

References 0 publications

Impedance pneumography for long‐term monitoring of respiration during sleep in adult males

Impedance pneumography for long‐term monitoring of respiration during sleep in adult males

Impedance pneumograph studies in left ventricular failure

Ventilation.

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