Surgery – Respiratory method or device – Means for supplying respiratory gas under positive pressure
Reexamination Certificate
1999-08-18
2001-07-10
Dawson, Glenn K. (Department: 3761)
Surgery
Respiratory method or device
Means for supplying respiratory gas under positive pressure
C128S204230
Reexamination Certificate
active
06257234
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to a system and method for determining a respiratory condition of a patient and to a system and method for controlling a ventilation system based on the determined condition, and, in particular, to a system and method that non-invasively measures a patient's elastance and resistance and to a ventilator that employs such a method to measure elastance and resistance during ventilation so that the ventilatory assistance provided to the patient by the ventilator is automatically adjusted to suit the needs of the patient.
2. Description of Related Art
The related art will be described with reference to the following patents and other publications, the disclosures of which are hereby incorporated by reference in their entireties into the present disclosure. Throughout the description of the related art, these references will be cited by the first-named author and the year of publication, e.g., Jackson, 1974.
M. Franetzki et al, U.S. Pat. No. 4,051,843 (1977); U.S. Pat. No. 4,022,193 (1977); and U.S. Pat. No. 4,122,839 (1978).
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P. H. Vooren, U.S. Pat. No. 4,259,967 (1981).
Y. Yoshitsugu, European Published Patent Application 0 521 515 A1 (1993).
P. J. Chowiency, C. P. Lawsom, et al, U.S. Pat. No. 5,233,998 (1993).
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, Vol. 72, Iss. 1., pp. 46-52 (1992).
Bates, J. H. T., Decramer, M., Zin, W. A., Harf, A., “Respiratory Resistance with Histamine Challenge by Single-breath and Forced Oscillation Methods,”
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, Vol. 103, No. 4, pp. 605-9 (1990).
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Daroczy, B., Hantos, Z., “Generation of Optimum Pseudorandom Signals for Respiratory Impedance Measurements,”
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, Vol. 25, pp. 21-31 (1990).
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&
Biological Engineering
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Computing
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Gimeno, F., van der Weele, L. Th., “Variability of Forced Oscillation (Siemens Siregnost FD5) Measurements of Total Respiratory Resistance in Patients and Health Subjects,”
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, Vol. 71, pp. 56-60 (July, 1993).
Hantos, Z., Daroczy, B., Suki, B., “Forced Oscillatory Impedance of the Respiratory System at Low Frequencies,”
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Jackson, A. C., Milhom, H. T., and Norman, J. R., “A Reevaluation of the Interrupter Technique for Airway Resistance Measurement,”
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Lutchen, Kenneth., Kaczka, David W., Suki, Bela, “Low-frequency Respiratory Mechanics Using Ventilator-driven Forced Oscillations,”
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, E. Leslie Chusid, ed., Futura Publishing Co., New York (1983).
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To understand how a machine can be controlled to replace or supplement the natural function of breathing, it is necessary to understand the mechanical nature of the respiratory system. The study of the mechanical behavior of the respiratory system requires analyzing the elastance and resistance properties of the patient's pulmonary system, which includes the airways, lung and thoracic cage. In clinical practice, respiratory resistance R
rs
and elastance E
rs
are essential information necessary to describe the behavior of the lung and the chest wall in health and disease states, and, in particular, to describe characteristics of that behavior, such as inspiratory vital capacity (IVC) and the forced expiratory volume in one second (FEV1). Furthermore, the use of state-of-the-art mechanical ventilation techniques, such as proportional assist ventilation (PAV), which is disclosed in U.S. Pat. Nos. 5,107,830 and 5,044,362 both to Younes, the contents of which are also incorporated herein by reference, requires knowledge of the patient's respiratory resistance and elastance.
Measuring the respiratory resistance and elastance of a spontaneously breathing patient is not a simple task. Conventional techniques for measuring resistance and elastance are somewhat invasive in that they are performed in a clinical or hospital setting and require placing a device for measuring esophageal pressures, such as an esophageal balloon, within the patient. Therefore, R
rs
and E
rs
are typically not measured on a routine basis. In order to perform these measurements more routinely, there is a need for an efficient and reliable technique that is as non-invasive as possible and requires little or no patient cooperation for spontaneously obtaining R
rs
and E
rs
, especially inspiratory R
rs
and E
rs
.
Respiratory mechanics takes into consideration the forces, displacement, rate of change (first time derivative) of displacement, and acceleration (second time derivative) of displacement. In respiratory physiology, force is measured in terms of pressure P, displacement is measured as volume V, rate of change of displacement is measured as flow {dot over (V)} (first time derivative), and acceleration of displacement is measured as the
Dawson Glenn K.
Haas Michael W.
Mitchell Teena
Respironics Inc.
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