Surgery – Respiratory method or device – Means for supplying respiratory gas under positive pressure
Reexamination Certificate
1998-03-10
2001-03-06
Weiss, John G. (Department: 3761)
Surgery
Respiratory method or device
Means for supplying respiratory gas under positive pressure
C128S204180, C128S204210
Reexamination Certificate
active
06196222
ABSTRACT:
BACKGROUND OF THE INVENTION
In respiratory treatment, a patient is connected to a ventilator that controls and/or supports the patient's breathing. The ventilator typically includes a means of mixing and forming a breathing gas having a predetermined ratio of one or more gases, the pressurized sources of which are connected to the ventilator. The ventilator could also possibly include internal means to compress ambient air. The gas mixture from the ventilator must contain sufficient amounts of oxygen for the treatment of the patient. For this reason, one of the gases is always O
2
, or alternatively, in the extremely simplified case, the one single gas source is air. Other gases that are often mixed with O
2
are typically air (N
2
and O
2
), and sometimes also helium.
To perform the mixing function, each of the gas flow paths has a regulating means, typically a valve, to regulate the gas flow. In the current state of the art technology, these regulators are driven by microprocessor control units according to information received by the controller from various pressure, flow, temperature and/or position sensors. The microprocessor compares this received information from the various sensors to predetermined control parameters and drives the regulators via feedback control. Mechanical mixers using flow resistance ratios are also used in some simple applications to supply a single flow controlling valve.
The patient is connected to the ventilator through a breathing circuit that includes an inspiratory limb, an expiratory limb, and a patient limb. These three limbs of the breathing circuit are connected together at a Y-piece connector. Breathing circuits are generally classified as either an open circuit or as a rebreathing circuit. An open breathing circuit is most often used in intensive care applications, whereas a rebreathing circuit is typically found in anesthesia systems. In both types of breathing circuits, the inspiratory limb conducts the gas to be inspired from the ventilator to the Y-piece connector. The expiratory limb conducts the expired gas from the Y-piece connector back to the ventilator. In an open circuit, the expiratory limb is connected to an expiratory valve that functions to regulate the expiratory pressure and discharges the gases to atmosphere. In a rebreathing circuit, the expiratory limb is connected to the ventilator for CO
2
removal.
In each type of breathing circuit, the patient limb connects the patient to the Y-piece connector and conducts inspired gases into the lungs and the expired gases back to the Y-piece connector. The patient limb typically includes an endotracheal tube, which is inserted into the trachea through the nose or mouth of the patient. Functionally, other equipment such as sensors, heat and moisture exchangers, and sampling connectors can be positioned between the Y-piece connector and the endotracheal tube.
When the patient is inspiring, the expiratory limb is closed through valves or other flow directing means depending on the breathing circuit. During inspiration, the ventilator forces the inspired gas to fill the patient's airways and lungs through the inspiratory and patient limbs with overpressure. During patient expiration, which is driven by the passive recoil of the lungs caused by the lungs' elastic force, the breathing circuit is arranged to conduct the exhaled gas through the patient and expiratory limbs back to the ventilator.
Modern ventilators used in intensive care applications use a base flow, which is a flow of gas supplied by the inspiratory valve to the inspiratory limb during the expiratory phase of the breathing cycle. The rationale behind the use of a base flow is to make it possible for the ventilator to detect an inspiratory effort by the patient with a minimal addition of extra work for the patient. In ordinary anesthetic rebreathing systems, fresh gas is delivered into the breathing system continuously from a fresh gas inlet.
The volume of breathing gas injected into the lungs during the inspiratory phase, also called the tidal volume (V
t
), ranges from a few tens of milliliters for a newborn child up to more than one liter for a large adult. The rate at which the tidal volumes are delivered, called the respiration rate, varies from a few tens of breaths/min. down to a few breaths/min. depending on the patient size. The typical range of breathing gas volumes per minute varies according to body weight and condition, but typically ranges from less than 1 liter/min. up to more than 10 liters/min.
The inspiratory tidal volume (V
t
) is normally delivered during the first third of the breathing cycle. Thus, the peak inspiratory flow may easily exceed thirty liters/min. and may momentarily reach more than 100 liters/min. in inspiration based on the control of a pre-set inspiratory pressure.
The tidal volume (V
t
) that ventilates the patient's alveoli can be divided into two parts, an alveolar volume (V
A
) and a deadspace volume (V
D
). The alveolar volume (V
A
) is defined as the volume of fresh gas that reaches the gas exchanging part of the patient's lung. In the alveoli, the high partial pressure of oxygen compared to the pressure of the perfused pulmonary blood flow makes the oxygen diffuse through the alveolar membrane and into the blood, such that the blood can transport the oxygen to tissues having a demand for oxygen. In an opposite manner, the high partial pressure of carbon dioxide (CO
2
) in the perfused pulmonary blood flow, as compared to the low pressure of CO
2
in the fresh gas, makes the CO
2
diffuse through the alveolar membrane into the alveoli to be washed out in expiration.
The deadspace volume (V
D
) is defined as the volume of fresh gas remaining in the patient limb and the upper airways of the patient, i.e., the trachea and bronchi at the end of inspiration. The deadspace volume does not take part in the gas exchange since it never reaches the patient's lungs.
Typically, the deadspace gas volume of a healthy human is in the order of 30% of the resting tidal volume, such as approximately 150 ml of deadspace in a 70 kg adult. In a patient with lung disease, the deadspace volume (V
D
) can be significantly increased.
The composition of the tidal volume (V
t
) is clarified in
FIG. 1
, where
FIG. 1A
represents the tidal volume (V
t
) divided into the alveolar volume (V
A
)
1
and the deadspace volume (V
D
)
2
. Thus, the tidal volume is a simple sum of the alveolar
1
volume (V
A
)
1
and the deadspace volume (V
D
)
2
.
FIG. 1
b
diagrammatically represents the gas exchange situation within the lungs at the beginning of inspiration by the patient, after the exhalation flow has stopped. At this point in time, the upper airways and the patient limb forming a deadspace
4
are filled with exhaled gas
3
. As shown in
FIG. 1
b
, the gas volume remaining within the patient's lungs is represented by the reference numeral
5
.
FIG. 1
c
shows the situation at the end of the inspiration by the patient. The volume of exhaled gas
3
previously present in the deadspace
4
has been sucked back into the patient's lungs
5
, followed by the alveolar volume
1
of fresh inspiratory gas. The combination of the alveolar volume
1
and the exhaled gas
3
have increased the volume of the lungs by the amount designated by reference numeral
6
. The deadspace comprised of the patient limb and the upper airways is now filled with fresh gas, referred to as the deadspace volume
2
, which does not participate in the gas exchange within the lungs. Thus, the only volume participating in the gas exchange is the alveolar volume
1
. Since the increase in lung volume is equal to the tidal volume (V
t
), the volume of exhaled deadspace gas
3
is equal to the deadspace volume (V
D
)
2
.
The human body attempts to maintain a constant CO
2
partial pressure, P
ACO2
, in the blood. Thus, a requirement exists for a certain amount of alveolar ventilation, see equation
1
, which is determined by the patient's need for the CO
2
elimination necessary to maintai
Heinonen Erkki P. O.
Larsson Lars Å
Andrus Sceales Starke & Sawall LLP
Instrumentarium Corporation
Weiss John G.
Weiss, Jr. Joseph F.
LandOfFree
Tracheal gas insufflation delivery system for respiration... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Tracheal gas insufflation delivery system for respiration..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Tracheal gas insufflation delivery system for respiration... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2506044