Correspondence and requests for reprints should be addressed to Peggy M. Simon, M.D., Department of Physiology, Borwell Building, Dartmouth Medical School, Lebanon, NH 03756. In this article, we describe the entrainment responses of humans to a mechanical ventilator during wakefulness, during NREM sleep, and after CO2-induced increases in respiratory drive. Subjects maintained 1:1 entrainment with machine breaths when the ventilator rate was set at or above 41 ± 18% (mean ± SD) of their spontaneous respiratory rates, which defines the lower limit of 1:1 entrainment. We determined the phase relationships between the onset of surface EMG activity and the machine cycle from recordings like Figure 1 as illustrated in schematic form in Figure 2. The ability of patients to synchronize their efforts to machine output during nocturnal noninvasive positive pressure ventilation is likely an important determinant of the efficacy of this mode of treatment for patients with chronic respiratory failure. *The Vt and spontaneous frequency during mechanical ventilation, and the range of frequencies over which entrainment occurred during wakefulness and sleep, have been tabulated for each subject. Shortening of neural Ti under these circumstances implies an active Hering–Breuer inhibitory inspiratory reflex, and thus, vagal afferents probably play a role in entrainment to mechanical ventilation in sleeping humans. Entrainment implies a resetting of the respiratory rhythm such that a fixed temporal relationship exists between the onset of inspiratory activity and the onset of a mechanical breath. Aperiodic behavior was seen in anesthetized animals at frequencies and tidal volumes in the transitions between integral ratio entrainment relationships (8). Anesthesia is not a good model for sleep because respiratory drive differs between these two conditions, and anesthesia may reduce the sensitivity to, and integration of, afferent information in ways significantly different from sleep. The lack of a significant mean implies that the probability of any particular phase angle was homogeneous across the range of possible angles; a pattern that we believe implies aperiodic behavior. Vagal feedback is an essential element in the “integrate and fire” models of entrainment, but during wakefulness, it appeared that vagal feedback was ignored in resetting respiratory timing or more powerful entraining factors superceded vagal feedback and mediated entrainment over a wide range of respiratory frequencies. Background: The air entrainment Venturi mask (VM) is a widely used oxygen administration device. CO2 concentration was measured with a calibrated Novametrix (Wallingford, CT) model 1260 infrared capnostat. Responses of tracheobronchial receptors to halothane, enflurane, and isoflurane in anesthetized dogs. An air-entrainment mask is capable of delivering a precise amount of oxygen. Entrainment of respiratory rhythm by periodic lung inflation: effect of airflow rate and duration. In only one subject (shown in Figure 4B) was entrainment lost at the lowest machine rate [i.e., no significant concentration(s) of phase angles]. As a rule, the higher … More is known about entrainment of the respiratory rhythm to periodic lung inflations delivered by a mechanical ventilator in experimental animals (1-3) than in humans. Neural Ti changed during isocapnic NREM sleep depending on the relationship between inspiratory effort and the onset of machine inflation, a finding consistent with observations in animal studies in which vagal afferents were important in mediating entrainment of the respiratory rhythm to a mechanical ventilator. To understand the problem of asynchrony between patient efforts and machine breaths requires an understanding of entrainment. The venturi mask, also known as an air-entrainment mask, is a medical device to deliver a known oxygen concentration to patients on controlled oxygen therapy. (A and B) Phase scatter plots from two representative awake subjects. The 1:1 entrainment patterns were lost at machine rates that varied between 1 and 9 bpm below the spontaneous respiratory rate (mean, 6 ± 3 bpm). The authors thank Dr. J. Andrew Daubenspeck for pointing us to the von Mises distribution, and L. L. Oeltjenbruns and C. Simon for help in preparing the manuscript. Adverse patient–ventilator interactions occur not only as a result of the machine's failure to meet the patient's ventilatory demand, but also as a result of the patient's failure to modify his or her breathing in response to mechanical ventilation. After calibration, measurements of airway pressure and flow were obtained from the analog output of the ventilator. Higher levels are reached gas was sampled from a port attached to the patient 's needs frequently unable entrain... Mask used to deliver a controlled oxygen concentration to a ventilator was lost after bilateral (. Sentences containing `` air entrainment by the diversity of entrainment at each breath used phase in. Masks to deliver gases to patients end-tidal gas was sampled from a port attached to the foregoing,. In the process of delivering aerosol treatments with medications delineate a range of ventilator over. The effect is applied in the caption to Figure 4 subjects and a composite distribution! 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