Apparatus for monitoring clinically significant surface movements in living organisms

Claim 2

Apparatus for detecting movement in an external or internal surface portion of a living organism for measuring a parameter of said living organism related to said movement, comprising: a conductive loop dimensioned and adapted for disposition on said external or internal surface portion; and means connected to said loop for generating a signal indicative of the inductance of said loop, changes in said signal being indicative of the extent of movement of said surface portion.

Claim 3

Apparatus as claimed in Claim 1, in which said signal generating means comprises a variable frequency LC oscillator wherein said loop comprises the inductive element, said oscillator converting changes in said inductance to corresponding changes in the frequency of the oscillator output.

Claim 4

Apparatus as claimed in Claim 2, further comprising means for converting changes in the frequency of said oscillator output signal to corresponding changes in signal amplitude.

Claim 5

Apparatus as claimed in any preceding claim, adapted for use on a human subject, in which said loop is dimensioned for disposition on the skin surface of the subject's suprasternal fossa, said signal thereby being indicative of said subject's intrapleural pressure.

Claim 6

Apparatus as claimed in Claim 4, in which the remainder of said loop is disposed on the manubrium of said subject's sternum.

Claim 7

Apparatus as claimed in Claim 4 or Claim 5, in which said loop has a circumference of the order of about twelve centimetres.

Claim 8

Apparatus as claimed in any one of Claims 4 to 6, in which said loop is approximately elliptically shaped, the major axis of said ellipse being approximately six centimetres, and the minor axis being approximately one and a half centimetres.

Claim 9

Appatatus as claimed in any one of Claims 4 to 7, further comprising means for calibrating said signal to provide acutal intrapleural pressure.

Claim 10

Apparatus as claimed in Claim 8, further comprising means for comparing said signal with intrapleural pressure as measured with an esophageal ballon catheter at zeron flow, and means for adjusting said signal to equal said intrapleural pressure as measured with said esophageal balloon catheter.

Claim 11

Apparatus as claimed in any preceding claim, further comprising means for recording the value of said signal at end expiration, means for incorporating said subject's respiratory tract in a closed system prior to expiration, means for monitoring during expiration the airway pressure of said subject required to return said signal to said end expiration value, said required airway pressure equalling actual intrapleural pressure, and optionally means for adjusting said signal to equal said required airway pressure.

Claim 12

Apparatus as claimed in Claim 10, in which said means for monitoring airway pressure comprises means for monitoring mouth pressure.

Claim 13

Apparatus as claimed in Claim 8, further comprising means for monitoring said subject's tidal volume at zero flow, means for simultaneously monitoring said subject's actual intrapleural pressure, and means for dividing tidal volume by the corresponding intrapleural pressure at zero flow at a plurality of respiration rates whereby to obtain dynamic lung compliance.

Claim 14

Apparatus as claimed in any one of Claims 4 to 7, further comprising means for monitoring said subject's tidal volume at zero flow for increasing tidal volumes, means for recording the value of said signal at end expiration, means for incorporating said subject's respiratory tract in a closed system prior to expiration, and means for monitoring during expiration the airway pressure of said subject required to return said signal to said end expiration value, said required airway pressure equalling actual intrapleural pressure, and means for dividing tidal volume at zero flow by the corresponding actual intrapleural pressure for increasing tidal volumes whereby to obtain static lung compliance.

Claim 15

Apparatus as claimed in any one of Claims 1 to 3, adapted for use on a human subject, in which said loop part is dimensioned for disposition on the skin surface over the sternomastoid muscle, said signal thereby being indicative of the activity of the accessory muscles of respiration.

Claim 16

Apparatus for measuring intrapleural pressure comprising means for measuring movement of the skin surface of the suprasternal fossa at zero flow, the extent of said movement being proportional to intrapleural pressure.

Claim 17

Apparatus for measuring intrapleural pressure comprising means for measuring movement of the skin surface of the suprasternal fossa at zero flow, the extent of said movement being proportional to intrapleural pressure.

Claim 18

Apparatus as claimed in Claim 15, further comprising means for providing a signal indicative of said measured movement, and means for calibrating said signal by comparison with an alternative technique for measuring intrapleural pressure.