scholarly journals Respiratory variations of the heart rate - II—The central mechanism of the respiratory arrhythmia and the inter-relations between the central and the reflex mechanisms

1936 ◽  
Vol 119 (813) ◽  
pp. 218-230 ◽  
Keyword(s):  
Heart Rate ◽  
Respiratory Rhythm ◽  
Respiratory Muscles ◽  
Respiratory Arrest ◽  
Central Mechanism ◽  
Respiratory Arrhythmia ◽  
Reflex Mechanism ◽  
Long Time ◽  
Respiratory Centre ◽  
Respiratory Movements

It was first noticed by Traube (1865) that the respiratory cardiac arrhythmia persists after curarization and that it becomes more obvious when the curarized animal is subjected to asphyxiation. Since, in his experiments, the muscles were paralysed and with the consequence the lungs remained in a stationary position Traube concluded that the arrhythmia could not be explained otherwise than by a direct influence of the respiratory centre upon the centres regulating the heart rate. The fact that the respiratory activity continues after administration of curare and that it becomes greatly increased during asphyxia is beyond dispute. In Traube’s time this could only be conjectured, but now it can be proved by registering the electrical deflexions of the phrenic nerve or of any other inspiratory nerve. This we had occasion to verify in many experiments. The theory of Traube was for a time superseded by Hering’s theory of the reflex origin of the arrhythmia (1871). However, Frédéricq (1882), in a series of masterly experiments, advanced such indisputable proofs in favour of the central mechanism that most physiologists began to doubt even the existence of the reflex mechanism. The respiratory arrhythmia continues in an animal the chest of which is widely open so that the lungs are stationary. When the respiration stops, as a result of an over ventilation, the arrhythmia also disappears. Snyder (1915) confirmed the observations of Frédéricq and expanded them by showing that the arrhythmia can be noticed even in the absence of any visible respiratory movements, but that even under these conditions it is of a central origin and depends on the respiratory centre. He suggests that the respiratory discharges may be so insignificant that they do not lead to an effective expansion of the chest; in fact, not even to a noticeable contraction of respiratory muscles, but they, nevertheless, affect the vagus centre and cause an appreciable inhibition of it. This conclusion rests on the observation that the arrhythmia occurring in absence of any sign of respiration keeps the rhythm of the respiratory movements which had been present before and which become re-established after a period of a temporary respiratory arrest. J. F. Heymans and C. Heymans (1928, 1929) investigated this problem with the help of cross circulation. They definitely express themselves in favour of the central mechanism of the arrhythmia since it is synchronous with the respiration and not with the ventilation of the lungs and since it continued, in their experiments, after the denervation of the lungs. They also found that the changes in the heart rate are not caused by the alteration of the blood pressure which accompanies the respiratory act so that the arrhythmia could not be attributed to some vascular reflexes. Although these authors find the changes in the heart rate to be synchronous with the respiration, they do not regard them as due to an irradiation from the respiratory centre since they can be observed, as has been first stated by Snyder, in the absence of all respiratory movements. Heymans (1929) suggests that there is a common rhythm which governs the activity of the respiratory and of the vagus centres and that there is no need to suppose that the respiratory rhythm directly influences the rhythm of the vagus centre. No experimental evidence has been advanced in favour of this view. Lately Heymans, Samaan, and Bouckaert (1934) seem to have accepted the fact that the lungs also play a part in the arrhythmia. Our experiments upon the central mechanism of the respiratory arrhythmia have been carried out with the technique described in the previous paper. It is obvious that in order to study the central arrhythmia without the interfering influences arising from the pulmonary reflexes, these reflexes must be abolished. We know of three conditions in which the cardio-accelerator impulses of pulmonary origin are almost or completely stopped: during a maximal deflation of the lungs, during the “secondary slowing” occurring in protracted inflation of the lungs, and after section of the thoracic vagi just above the lungs. The last condition obviously presents greater advantages because it is inadvisable, even in the innervated heart lung preparation, to keep the lungs collapsed for a long time, and it is difficult to be sure that the secondary slowing will remain unchanged. Therefore, all our experiments were made after preliminary section of the vagi about a centimetre above the roots of the lungs.

scholarly journals Respiratory variations of the heart rate - I—The reflex mechanism of the respiratory arrhythmia

1936 ◽  
Vol 119 (813) ◽  
pp. 191-217 ◽  
Keyword(s):  
Heart Rate ◽  
Cardiac Arrhythmia ◽  
Point Of View ◽  
Central Mechanism ◽  
Respiratory Arrhythmia ◽  
Reflex Mechanism ◽  
Physiological Laboratory ◽  
Vagus Tone ◽  
The Subject ◽  
The Difference

The fact that under certain conditions in some animals and in man inspiration is accompanied by an acceleration of the heart rate has been demonstrated by many observers and can be considered as well established. Agreement has not yet been reached, however, about the mechanism underlying this respiratory cardiac arrhythmia. E. Hering (1871), H. E. Hering (1895), Nikiforovsky (1910), Blumenfeldt and Putzig (1914) regard the arrhythmia as caused by a reflex the stimulus for which originates within the lungs. Traube (1865), Frédéricq (1882), Foa (1913), Snyder (1915), and Heymans (1929) attribute it to a purely central influence; Bainbridge and Hilton (1918-19), and Bainbridge (1920) deny any direct influence of the respiratory act upon the heart rate and ascribe the arrhythmia to the rise in the intra-auricular blood pressure taking place during inspiration. Thus Bainbridge regards the respiratory changes of the heart rate as a reflex which accompanies respiration but is not directly caused by it. Recently H. E. Hering accepted this point of view (1933). The question whether inspiration provides the stimulus for the cardiac acceleration or whether the expiration provides the stimulus for the retardation or both is not yet settled. Neither is there an agreement about the efferent path through which the changes in the heart rate are produced, the effect being attributed by some authors to variations of the vagus tone and by others to variations of the accelerator tone. The present investigation was undertaken in order to obtain further information upon the subject and, if possible, to find the cause of the difference between the observations of the previous authors. The research was begun in 1929 in the Physiological Laboratory of Cambridge and continued up to the present in Cairo. Our preliminary experiments convinced us that there were at least two distinct mechanisms underlying the respiratory cardiac arrhythmia, a reflex and a central mechanism. It was also soon found that the result of action of these two mechanisms may be greatly changed or even reversed under different conditions. The reflex and the central mechanism may overlap or interfere with each other so that the study of one of them in the presence of the other is confusing and unreliable. Our investigation thus became naturally divided into three sections: ( a ) the study of the reflex mechanism in absence of the central mechanism, ( b ) the study of the central mechanism in absence of the reflex mechanism, and ( c ) the study of the interaction between the reflex and the central mechanisms. Only reaction ( a ) is considered in Part I; sections ( b ) and ( c ) are discussed in Part II.

scholarly journals Clinical-epidemiological aspects of whooping cough in children in conditions of mass vaccinoprophylactics

2019 ◽  
Vol 11 (2) ◽  
pp. 88-96 ◽  
Author(s):  
I. V. Babachenko ◽  
Yu. V. Nesterova ◽  
Yu. Yu. Chernyshova ◽  
V. V. Karasev ◽  
L. M. Pochinyaeva ◽  
...  
Keyword(s):  
Whooping Cough ◽  
Bacterial Load ◽  
Respiratory Rhythm ◽  
Respiratory Arrest ◽  
Hospitalized Children ◽  
Pertussis Infection ◽  
High Coverage ◽  
Causative Agents ◽  
Long Time

The aim of the study was to present clinical, epidemiological and laboratory characteristics of modern pertussis in hospitalized children, as well as to assess the frequency of pertussis infection as an etiological factor of long – term cough in children and adolescents.Materials and methods: medical records of 545 patients hospitalized in Children’s city clinical hospital №5 named after N.F. Filatov (Saint-Petersburg) in the period 2015–2017 were analyzed. Detailed clinical and laboratory analysis with subsequent follow-up of patients was carried out in 80 patients with pertussis aged 1 month to 18 years. The DNA of the causative agents of pertussis infection was identified by PCR using a commercial kit “AmpliSens Bordetella multi-FL” (Moscow); parallel was determined the bacterial load by quantitative PCRRT (real time) using test systems production, Gamaleya Research Institute of Epidemiology and Microbiology (Moscow), allowing to detect a single genome-equivalents (GE) of B. pertussis in smears from the nasopharynx. Pertussis convalescents were examined 1, 3 and 6 months after discharge.Results. Among hospitalized children dominated the first 2 years of life (70.8%), 78% were unvaccinated children. The sources of infection for children of the first two years of life were family members in 77% of cases, for preschoolers-in 67%, for schoolchildren-in 14%. Patients of moderate severity were 81.1%, severe – 10.3%; mild – 7%. Of the specific complications, respiratory rhythm disturbances were notedin 11.6%, including respiratory arrest-in 2.8%; pneumonia of mixed etiology was recorded in 6.2% of cases. Introduction of PCR method allows to increase laboratory confirmation up to 87.2%. In 63.6% of cases pertussis of pertussis were detected by PCR genome-equivalents of DNA in 6 months from hospital discharge. In patients with long – term cough, pertussis wand DNA was detected in preschool children in 11.14% of cases, in patients 7–12 years – in 25.93%, in adolescents-in 20% of cases.Conclusion. Whooping cough is a common infection among schoolchildren and adolescents, despite the high coverage of young children with preventive vaccinations. Pertussis convalescents can release the DNA of the pathogen for a long time, which may have epidemiological significance for unvaccinated and those children and adults, who have lost postvaccinal immunity, in the foci of infection.

N-acetylcysteine administration alters the response to inspiratory loading in oxygen-supplemented rats

1997 ◽  
Vol 82 (4) ◽  
pp. 1119-1125 ◽  
Author(s):  
G. S. Supinski ◽  
D. Stofan ◽  
R. Ciufo ◽  
A. Dimarco
Keyword(s):  
Free Radical ◽  
Respiratory Failure ◽  
Respiratory Muscles ◽  
Treated Group ◽  
Respiratory Arrest ◽  
Saline Group ◽  
Free Radical Scavenger ◽  
Radical Scavenger ◽  
Resistive Load ◽  
Loaded Breathing

Supinski, G. S., D. Stofan, R. Ciufo, and A. DiMarco. N-acetylcysteine administration alters the response to inspiratory loading in oxygen-supplemented rats. J. Appl. Physiol. 82(4): 1119–1125, 1997.—Based on recent studies, it has been suggested that free radicals are elaborated in the respiratory muscles during strenuous contractions and contribute to the development of muscle fatigue. If this theory is correct, then it should be possible to attenuate the development of diaphragm fatigue and/or delay the onset of respiratory failure during loaded breathing by administering a free radical scavenger. The purpose of the present experiment was, therefore, to examine the effect of N-acetylcysteine (NAC), a free radical scavenger and glutathione precursor, on the evolution of respiratory failure in decerebrate unanesthetized rats breathing against a large inspiratory resistive load. We compared the inspiratory volume and pressure generation over time in animals pretreated with either saline or NAC (150 mg/kg) and then loaded until respiratory arrest. After arrest, the diaphragm was excised, and samples were assayed for reduced (GSH) and oxidized glutathione. As a control, we also assessed respiratory function and glutathione concentrations in groups of nonloaded saline- and NAC-treated animals. We found that NAC-treated animals were able to tolerate loading better than the saline-treated group, maintaining higher inspiratory pressures and sustaining higher inspired volumes. Administration of NAC also increased the time that animals could tolerate loading before the development of respiratory arrest. In addition, although saline-treated loaded animals had significant reductions in diaphragmatic GSH levels compared with unloaded controls, the magnitude of this reduction was blunted by NAC administration (i.e., GSH averaged 965 ± 113, 568 ± 83, 907 ± 39, and 784 ± 61 nmol/g for unloaded-saline, loaded-saline, unloaded-NAC, and loaded-NAC groups, P< 0.05, with the value for the loaded-saline group lower than the values for the two unloaded groups; GSH for the loaded-NAC group was not different, however, from unloaded controls). These data demonstrate that administration of NAC, a free radical scavenger, slows the rate of development of respiratory failure during inspiratory resistive loading.

scholarly journals Nonlinearities of heart rate variability in animal models of impaired cardiac control: contribution of different time scales

2017 ◽  
Vol 123 (2) ◽  
pp. 344-351 ◽  
Author(s):  
Luiz Eduardo Virgilio Silva ◽  
Renata Maria Lataro ◽  
Jaci Airton Castania ◽  
Carlos Alberto Aguiar Silva ◽  
Helio Cesar Salgado ◽  
...  
Keyword(s):  
Nonlinear Dynamics ◽  
Heart Rate ◽  
Heart Rate Variability ◽  
Time Scales ◽  
Multiscale Entropy ◽  
Time Frequency ◽  
Cardiac Control ◽  
Long Time ◽  
Nonlinear Features ◽  
Short Time

Heart rate variability (HRV) has been extensively explored by traditional linear approaches (e.g., spectral analysis); however, several studies have pointed to the presence of nonlinear features in HRV, suggesting that linear tools might fail to account for the complexity of the HRV dynamics. Even though the prevalent notion is that HRV is nonlinear, the actual presence of nonlinear features is rarely verified. In this study, the presence of nonlinear dynamics was checked as a function of time scales in three experimental models of rats with different impairment of the cardiac control: namely, rats with heart failure (HF), spontaneously hypertensive rats (SHRs), and sinoaortic denervated (SAD) rats. Multiscale entropy (MSE) and refined MSE (RMSE) were chosen as the discriminating statistic for the surrogate test utilized to detect nonlinearity. Nonlinear dynamics is less present in HF animals at both short and long time scales compared with controls. A similar finding was found in SHR only at short time scales. SAD increased the presence of nonlinear dynamics exclusively at short time scales. Those findings suggest that a working baroreflex contributes to linearize HRV and to reduce the likelihood to observe nonlinear components of the cardiac control at short time scales. In addition, an increased sympathetic modulation seems to be a source of nonlinear dynamics at long time scales. Testing nonlinear dynamics as a function of the time scales can provide a characterization of the cardiac control complementary to more traditional markers in time, frequency, and information domains. NEW & NOTEWORTHY Although heart rate variability (HRV) dynamics is widely assumed to be nonlinear, nonlinearity tests are rarely used to check this hypothesis. By adopting multiscale entropy (MSE) and refined MSE (RMSE) as the discriminating statistic for the nonlinearity test, we show that nonlinear dynamics varies with time scale and the type of cardiac dysfunction. Moreover, as complexity metrics and nonlinearities provide complementary information, we strongly recommend using the test for nonlinearity as an additional index to characterize HRV.

scholarly journals FETAL TYPE CLASSIFICATION BASED ON FETAL ELECTROCARDIOGRAPH IN NON-STRESS TESTS

2021 ◽  
pp. 2140052
Author(s):  
JIANLI LIU ◽  
YIMIN YANG ◽  
SONG ZHANG ◽  
XUWEN LI ◽  
LIN YANG ◽  
...  
Keyword(s):  
Heart Rate ◽  
Fetal Heart Rate ◽  
Fetal Heart ◽  
Classification Model ◽  
Support Vector ◽  
Stress Tests ◽  
Nonlinear Parameters ◽  
Design Algorithm ◽  
Long Time

Electronic fetal heart rate (FHR) monitoring is a technical means to evaluate the state of the fetus in the uterus by monitoring FHR. The main purpose is to detect intrauterine hypoxia and take corresponding medical measures timely. Because the fetus sleeps quietly for up to 1 hour sometimes, ultrasound Doppler is not easy to continuously detect for a long time. The electronic fetal monitor obtains the fetal heart rate, which not only improves the accuracy and comfort, but also the convenient implementation of long-term monitoring. It is beneficial to reduce perinatal fetal morbidity and mortality. This study used maternal–fetal Holter monitor which is based on the technology of fetal electrocardiograph (FECG) to collect the FHR, and then design algorithm to extract the baseline FHR, acceleration, variation, sleep-wake cycle and nonlinear parameters. There were significant differences in the 22 parameters between the normal and the suspicious group. Using the 22 characteristic parameters, the support vector machine was used to classify the normal and the suspected group of fetuses. 80% of the data was used to train a classification model. The remaining 20% of the data was used as a test set and its accuracy reached 93.75%.

scholarly journals Heart rate variability changes in mild-symptomatic, physically fit male in 4-6 weeks from the end of SARS-Cov-2 infection

2021 ◽  
Author(s):  
Mateusz Soliński ◽  
Agnieszka Pawlak ◽  
Monika Petelczyc ◽  
Teodor Buchner ◽  
Joanna Aftyka ◽  
...  
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Nervous System ◽  
Autonomic Nervous System ◽  
Respiratory Rhythm ◽  
Frequency Component ◽  
Night Time ◽  
Control Male ◽  
Autonomic Nervous ◽  
Male Subjects

Abstract SARS-Cov-2 infection, due to inflammation processes, can affect autonomic nervous system and heart rate variability (HRV) even after disease. Previous studies showed significant changes in HRV parameters in severe (including fatal) infection of SARS-Cov-2. However, HRV analysis for the asymptomatic or mild-symptomatic Covid-19 patients have not been reported. In this study, we suggested that there is an influence of a SARS-Cov-2 infection on the HRV in such patients after weeks form disease.Sixty-five ECG Holter recordings from young (mean age 22.6 ± 3.4 years), physically fit male subjects after 4-6 weeks from the second negative test (considered to be the beginning of recovery) and twenty-six control male subjects (mean age 23.2 ± 2.9 years) were considered in the study. Night-time RR time series were extracted from ECG signals. Selected linear, frequency as well as nonlinear HRV parameters were calculated. We found significant differences in Porta’s symbolic analysis parameters V0 and V2 (p<0.001), α2 (p<0.001), very low frequency component (VLF; p=0.022), and respiratory peak (from PRSA method; p=0.012). These differences may be caused by the changes of the parasympathetic autonomic nervous system as well as by the coupling of respiratory rhythm with heart rate due to an increase in pulmonary arterial vascular resistance.The results suggest that the changes in the HRV, thus autonomic nervous system, are measurable after a few weeks from the beginning of the recovery even in the post-Covid group of young and physically active population. We indicated HRV sensitive markers which could be used in the long-term monitoring of recovered patients.

Time- and age-dependent effects of serotonin on gasping and autoresuscitation in neonatal mice

2013 ◽  
Vol 114 (12) ◽  
pp. 1668-1676 ◽  
Author(s):  
Jianping Chen ◽  
Jennifer Magnusson ◽  
Gerard Karsenty ◽  
Kevin J. Cummings
Keyword(s):  
Heart Rate ◽  
Tryptophan Hydroxylase ◽  
Single Injection ◽  
Heart Rate Recovery ◽  
Wild Type ◽  
Tryptophan Hydroxylase 2 ◽  
Age Dependent ◽  
Long Time ◽  
Time Required

The role of brain stem serotonin (5-hydroxytryptamine, 5-HT) in autoresuscitation in neonatal life is unclear. We hypothesized that a specific loss of 5-HT would compromise gasping and autoresuscitation mainly in the second postnatal week and that acute restoration of 5-HT would reverse the defects. We exposed postnatal day (P)4–5, P8–9, and P11–12 tryptophan-hydroxylase-2 knockout ( TPH2−/−) and wild-type littermates (WT) to 10 episodes of anoxia (97% N2, 3% CO2), measuring survival, gasp latency, gasp frequency ( fB), and the time required to restore eupnea and heart rate. We also tested P8–9 TPH2−/− mice after restoring 5-HT with a single injection of 5-hydroxytryptophan (5-HTP) 1–2 h before testing or with multiple injections beginning 24 h before testing. At P4–5 and P8–9, but not at P11–12, gasp latency and the recovery of eupnea were delayed ∼2- to 3-fold in TPH2−/− pups compared with WT ( P < 0.001). At all ages, TPH2−/− pups displayed reduced gasp fB (∼20–30%; P < 0.001) and delayed heart rate recovery (∼60%; P = 0.002) compared with WT littermates. TPH2−/− survival was reduced compared with WT ( P < 0.001), especially at P8–9 and P11–12 ( P = 0.004). Whereas 1–2 h of 5-HTP treatment improved the gasp latency and fB of P8–9 TPH2−/− pups, improved cardiorespiratory recovery and survival required 24 h of treatment. Our data suggest that 5-HT operates over a long time span (∼24 h) to improve survival during episodic severe hypoxia. Early in development (P4–9), 5-HT is critical for both respiratory and cardiovascular components of autoresuscitation; later (P11–12), it is critical mainly for cardiovascular components. Nevertheless, the effect of 5-HT deficiency on survival is most striking from P8 to P12.

Prostacyclin reduces "preload" in conscious dogs via a vagal reflex mechanism

1987 ◽  
Vol 253 (6) ◽  
pp. H1477-H1483
Author(s):  
D. M. Nganele ◽  
T. H. Hintze
Keyword(s):  
Heart Rate ◽  
Arterial Pressure ◽  
Left Ventricular ◽  
Vagal Afferents ◽  
Conscious Dogs ◽  
Reflex Mechanism ◽  
Capacitance Vessels ◽  
Preload Reduction ◽  
Cardiopulmonary Receptors ◽  
Electrical Pacing

The purpose of this study was to determine the effects of prostacyclin on left ventricular (LV) preload in conscious dogs. LV end-diastolic diameter (LV EDD) was used as an index of preload. Because prostacyclin reduces arterial pressure, data were sampled when mean arterial pressure, heart rate, and first derivative of LV pressure (dP/dt) had returned to control levels. There was no dose-response relationship in the preload reduction to prostacyclin, the threshold dose being 0.1 microgram/kg. Intravenous prostacyclin (2.0 micrograms/kg) reduced LV EDD 2.9 +/- 0.5% from 36 +/- 2.2 mm, (P less than 0.01). With heart rate held constant (146 +/- 2.5 beats/min) by electrical pacing, prostacyclin still reduced LV EDD by 4.0 +/- 1.0% from 32 +/- 2.5 mm (P less than 0.05). Intravenous administration of arachidonic acid (500 micrograms/kg) gave similar results. The magnitude of the preload response to prostacyclin was similar to that of nitroglycerin (25 micrograms/kg). Prazosin (1 mg/kg) or bilateral cervical vagal section completely abolished the preload response to prostacyclin but not to nitroglycerin. We, therefore, propose a mechanism where prostacyclin activates cardiopulmonary receptors with vagal afferents that results in a withdrawal of peripheral sympathetic tone to capacitance vessels to reduce preload, in contrast to nitroglycerin, whose mechanism of action is most probably a direct effect on capacitance vessels.

Modification of mastication and respiration during swallowing in the adult human

1995 ◽  
Vol 74 (4) ◽  
pp. 1509-1517 ◽  
Author(s):  
D. H. McFarland ◽  
J. P. Lund
Keyword(s):  
Respiratory Rhythm ◽  
Phase Relationship ◽  
Head Movements ◽  
Rib Cage ◽  
Jaw Opening ◽  
Prolonged Apnea ◽  
Pattern Generators ◽  
Analysis System ◽  
Respiratory Movements ◽  
Opening Phase

1. The normal interactions between respiration, mastication, and swallowing were studied in seated adult humans. Respiratory movements and movements of the larynx were recorded with mercury-elastic strain gauges placed around the rib cage and neck. A rigid body containing infrared-emitting diodes (IREDs) was attached to the forehead, and a single IRED was applied to the chin. Jaw and head movements were transduced using the OPTOTRAK spatial motion analysis system. Recordings were made before, during, and after the mastication of pieces of carrot. 2. Movements of the larynx were used as a marker for swallowing. Measurements were made of the duration of masticatory and respiratory cycles, and the phase relationship between the two rhythms was determined. Deviations in masticatory and respiratory movements during swallowing were detected; the phases of the masticatory and respiratory cycles in which the deviations occurred were determined, and the interval between each deviation and the swallowing marker was calculated. 3. Three characteristic swallowing patterns were observed: interposed, terminal, and spontaneous. Interposed swallows occurred within a masticatory sequence, terminal swallows ended the sequence, and spontaneous swallows occurred sporadically between masticatory sequences. 4. Results revealed that mastication could have a profound effect on the respiratory rhythm in some subjects. One subject, whose data were excluded from further analyses, became apneic for a long period, followed by short and shallow breaths near the end of the masticatory sequence. In most subjects, respiratory rate increased during mastication and then dropped below baseline as soon as mastication ended. The end-inspiration diameter of the rib cage tended to decrease in the preswallow period and increase postmastication relative to baseline. 5. There was a weak but significant tendency for inspiration to begin during the jaw opening phase of mastication, but phase coupling did not become stronger as swallowing was approached. 6. Deviations in respiration during swallowing occurred during the late expiratory phase of the breathing cycle. Swallows within a masticatory sequence occurred most frequently during the early opening phase of the masticatory cycle, and terminal swallows occurred after the end of the sequence with the mandible in the resting, postural position. Swallowing temporarily reset both the masticatory and respiratory rhythms. Most swallows prolonged the duration of one or two respiratory cycles, however; swallows were often repetitive, and in some subjects two or three swallows fell within a single respiratory cycle, prolonging it for several seconds. 7. A tight temporal relationship was observed between deviations in respiration and the swallowing marker: all deviations occurred before or coincident with the marker. The time of deviations in mastication relative to the swallowing marker depended on swallow type. There was no link between the start of pauses in the two rhythms, suggesting that the commands from the swallowing central pattern generator to the other two pattern generators are independent. 8. We suggest that disordered coordination of mastication and swallowing with respiration may cause prolonged apnea in susceptible individuals.

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