Apparatus and method for penetration with shaft having a sensor for sensing penetration depth

An apparatus having a shaft for penetration into tissue which has impedance that varies according to the depth of tissue penetrated comprising:

• (a) a shaft having a size of that of a hypodermic needle, with a sharp tip for penetration;
• (b) An impedance sensor connected to the shaft and including:
• first and second conductors proximate to the sharp tip such that a change of impedance of material of the tissue between the first and second conductors can be sensed to provide information on the depth of penetration;
• electronics for determining said change in impedance;
• first and second lines extending along the shaft to connect the conductors to the electronics;
• and an electrical insulator interposing between the first conductor and the second conductor;
• and
• (c) mechanical driver operatively contacting the shaft for incrementally driving the shaft, the driving action being affected by said change of impedance.

A method for inserting a needle-sized shaft through the skin and underlying tissue comprising:

• (a) driving a needle-sized shaft to penetrate into said tissue through the skin;
• (b) electrically sensing the electrical impedance of said tissue from an electronic circuit to determine whether desired penetration depth has been achieved;
• and
• (c) automatically stopping the advance of the needle-sized shaft when the desired depth has been achieved based on an electrical signal provided to an electrically controlled driver by said electronic circuit.

An apparatus having a shaft for penetrating into tissue which has impedance that varies according to the depth of tissue penetrated comprising:

• a shaft comprising:
• (i) a shaft body with a tip for penetration;
• and
• (ii) first and second conductors proximate to the tip such that a change of impedance of material of the tissue between the first and second conductors can be sensed to provide information on the depth of penetration;
• and
• a mechanical driver associated with the shaft for driving the shaft into the body by incremental steps.

A method for driving a shaft into ti'sue, comprising:

• (a) driving a shaft having a tip to penetrate into tissue having a fluid therein;
• (b) sensing the impedance of the material in the tissue proximate the tip of the shaft during penetration to determine whether desired depth has been achieved and automatically modifying the driving action based on the impedance sensed by an electronic circuit, said electronic circuit providing an electrical signal to modify said driving action;
• and
• allowing fluid to flow from the tissue through a channel in the shaft to sample the fluid.