Browsing by Subject "respiratory system function"

Now showing 1 - 3 of 3
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    A Closed-Loop Model of the Respiratory System: Focus on Hypercapnia and Active Expiration
    (2014-10) Molkov, Yaroslav I; Shevtsova, Natalia A; Park, Choongseok; Ben-Tal, Alona; Smith, Jeffrey C; Rubin, Jonathan E; Rybak, Ilya A
    Breathing is a vital process providing the exchange of gases between the lungs and atmosphere. During quiet breathing, pumping air from the lungs is mostly performed by contraction of the diaphragm during inspiration, and muscle contraction during expiration does not play a significant role in ventilation. In contrast, during intense exercise or severe hypercapnia forced or active expiration occurs in which the abdominal “expiratory” muscles become actively involved in breathing. The mechanisms of this transition remain unknown. To study these mechanisms, we developed a computational model of the closed-loop respiratory system that describes the brainstem respiratory network controlling the pulmonary subsystem representing lung biomechanics and gas (O2 and CO2) exchange and transport. The lung subsystem provides two types of feedback to the neural subsystem: a mechanical one from pulmonary stretch receptors and a chemical one from central chemoreceptors. The neural component of the model simulates the respiratory network that includes several interacting respiratory neuron types within the Bötzinger and pre-Bötzinger complexes, as well as the retrotrapezoid nucleus/parafacial respiratory group (RTN/pFRG) representing the central chemoreception module targeted by chemical feedback. The RTN/pFRG compartment contains an independent neural generator that is activated at an increased CO2 level and controls the abdominal motor output. The lung volume is controlled by two pumps, a major one driven by the diaphragm and an additional one activated by abdominal muscles and involved in active expiration. The model represents the first attempt to model the transition from quiet breathing to breathing with active expiration. The model suggests that the closed-loop respiratory control system switches to active expiration via a quantal acceleration of expiratory activity, when increases in breathing rate and phrenic amplitude no longer provide sufficient ventilation. The model can be used for simulation of closed-loop control of breathing under different conditions including respiratory disorders.
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    NON-INVASIVE DEVICE AND METHOD FOR MEASURING THE CARDIAC OUTPUT OF A PATIENT
    (2008-03-18) Kline, Jeffrey A.
    A method and system for detecting the presence of restriction to expired airflow in humans or animals by analyzing the expired capnogram and oxygram, as well as the geometric analysis of the real-time plot of the waveform that depicts the instantaneous ratio of CO2 to O2 (the carboxygram ratio). Airway obstructions causes an increase in the Q-angle between the slope of phase 11 and slope of phase III in the expired carboxygram. The diagnostic accuracy of the detection of airways obstruction is further enhanced by measuring the ratio of time spent in exhalation (Te) versus inhalation (Ti). The system uses the combination of an increased carboxygram Q-angle, and a prolonged Te/Ti to detect presence of airways obstruction.
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    NON-INVASIVE DEVICE AND METHOD FOR THE DIAGNOSIS OF PULMONARY VASCULAR OCCLUSIONS
    (2005-04-19) Kline, Jeffrey A.
    The invention involves a device and method for ascertaining the functioning of the respiratory system and determining whether a pulmonary embolism is present. The device comprises an apparatus containing sensors which measure the amount of a particular gas expired from a patient's lungs, including a non-ambient gas which is previously provided to the patent. From this data, a processor computes the concentration of expired gas as a function of expired volume and displays the results on a screen. By comparing the results to predetermined values from afflicted and healthy patient populations, an accurate determination can be made regarding the presence of a pulmonary embolism.