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Biomedical subjects

S W Porges

Publications and source records attributed to S W Porges.

At least 19 recordsLinked to original sources
PubMed1992

Effects of alprazolam and imipramine on parasympathetic cardiac control in patients with generalized anxiety disorder.

A noninvasive measure was used to assess the effects of alprazolam, imipramine and placebo on parasympathetic (vagal) cardiac control following 6-weeks of medication in patients with generalized anxiety disorder. Flexible dosage at therapeutic levels resulted in increased heart rate and blood pressure and in decreased cardiac vagal control in patients receiving imipramine but not alprazolam or placebo. About 50% of the variance in heart rate changes and changes in mean arterial blood pressure following treatment with imipramine could be accounted for by changes in cardiac vagal control. Decreased cardiac vagal control can now be added to the list of cardiovascular changes seen following several weeks of treatment with imipramine.

Adult↗
PubMed1992

Research methods for measurement of heart rate and respiration.

Strategies for heart rate and respiration quantification are dependent upon a knowledge of physiology and statistics. To develop appropriate and sensitive psychophysiological measures, it is necessary to understand the neural control of the autonomic nervous system and the statistical characteristics of physiological data. Moreover, it is proposed that inferences derived from physiological measures are dependent upon a statistical interaction between the characteristics of the physiological data and the measurement techniques. The steps required to analyze heart rate and respiration data are presented, ranging from data acquisition and editing to data analysis and physiological inference. A variety of techniques are described and contrasted with recommendations for future research.

Arousal↗
PubMed1992

Cardiac vagal tone predicts outcome in neurosurgical patients.

OBJECTIVE: To evaluate the relationship between presurgical levels of cardiac vagal tone and outcome in neurosurgical patients. DESIGN: Prospective series. SETTING: Respiratory ICU in a university hospital. PATIENTS: Fifty-one adults admitted to the respiratory ICU between 1982 and 1985. Forty-two patients were scheduled for elective neurosurgery, and nine patients suffered from head trauma. INTERVENTIONS: Ten minutes of electrocardiographic (EKG) data were recorded before medical intervention. Neurosurgical patients scheduled for surgery had EKG data recorded 24 hrs before their operation. Trauma patients had EKG data recorded immediately after arrival in the respiratory ICU. MEASUREMENTS AND MAIN RESULTS: Cardiac vagal tone was evaluated using a vagal tone index, quantified from the EKG. Cardiac vagal tone monitored before surgical intervention significantly distinguished between the outcome groups only for the elective neurosurgical patients. Age, gender, heart rate, Glasgow Coma Scale scores, and tumor location, size, and malignancy were not related to outcome in the elective neurosurgery group. However, within the trauma group, low Glasgow Coma Scale scores were significantly related to poor outcome. CONCLUSIONS: Cardiac vagal tone may offer important predictive value by alerting the physician to the functional consequence of head injury. Information relating to autonomic nervous system functioning, such as the vagal tone index used in this study, may provide additional information that will complement the computed tomography scan results. This study demonstrates that the vagal tone index is a predictive factor that may be efficiently extracted from the heart rate pattern routinely monitored in ICUs.

Adolescent↗
PubMed1992

Frequency-specific amplification of heart rate rhythms using oscillatory tilt.

Heart rate rhythms have been demonstrated to parallel specific psychological processes. Efficient experimental control of the amplitude of these rhythms would allow evaluation of bidirectional psychophysiological hypotheses. This experiment was performed to examine the specificity of the heart rate rhythm response to oscillatory head-up tilt. Seventy-one adults (36 male, 35 female) aged 18-30 were positioned on a tilt-table and oscillated at 0.08 Hz with a maximum tilt angle of +21 degrees for a 10-min period. Heart period, heart period variability at 0.08 Hz (i.e., Traube-Hering-Mayer (THM) variance), and respiratory sinus arrhythmia (quantified using vagal tone, V) were measured. For a subset of 21 subjects, continuous measures were derived to examine the response to onset of oscillatory tilt. Respiratory activity was also measured in these subjects. There was a significant increase in the amplitude of the THM variance during tilt stimulation. Tilt did not significantly change heart period, V, or respiration frequency. Following cessation of tilt, THM variance returned to baseline levels, heart period lengthened for males, and V increased for both sexes. Subjects with higher amplitude baseline V were characterized by more rapid THM variance response to tilt. Results suggest that parasympathetic tone moderates the THM variance increase elicited by low-frequency oscillatory tilt.

Adolescent↗
PubMed1992

Vagal tone: a physiologic marker of stress vulnerability.

Vagal tone is proposed as a novel index of stress vulnerability and reactivity with applications in all branches of medicine, and with particular value in pediatrics. The paper proposes a model emphasizing the role of the parasympathetic nervous system and particularly the vagus nerve in mediating homeostasis and defining stress. Measurement of cardiac vagal tone is proposed as a method to assess on an individual basis both the stress response and the vulnerability to stress. The method monitors the neural control of the heart via the vagus (ie, vagal tone) as an index of homeostasis. The method provides a standard instrument with statistical parameters that are comparable between patients and throughout the life span. This noninvasive method will allow the assessment of the stressful impact of various clinical treatments on the young infant and permit the identification of individuals with vulnerabilities to stress.

Autonomic Nervous System↗
PubMed1991

Vagal responsiveness to gavage feeding as an index of preterm status.

Vagal responsivity to orogastric stimulation is necessary for gastrointestinal function and may reflect autonomic regulation. Our study evaluated vagal responsivity during gavage feeding as an index of preterm clinical status. Vagal and behavioral responsivity of 26 preterm infants during gavage feeding was measured. Vagal tone was quantified with a noninvasive measure (vagal tone index) developed by Porges (Porges SW: U.S. patent 4,510.944, 1985), which extracts a valid measure of cardiac vagal tone from the ECG. The study investigated whether vagal tone changed during gavage feeding and whether individual differences in the vagal tone response pattern were related to clinical outcome. Infants who demonstrated an increase in vagal tone during feeding and a decrease after feeding had significantly shorter hospitalizations. This effect was independent of weight gain trajectories. Baseline levels of vagal tone were positively associated with subsequent weight gain. Traditional risk measures did not predict length of hospitalization independently of gestational age. This study represents the first documentation that small changes in cardiac vagal tone during gavage feeding, previously imperceptible to clinicians and researchers, may be quantitatively extracted from the ECG and provide an important index of clinical status.

Heart Rate↗
PubMed1990

Vagal mediation of the effect of alcohol on heart rate.

Alcohol (0.5 g/kg bodyweight) was administered in two sessions and placebo in a third session to normal, healthy social drinkers. A control group was administered a mixer (i.e., no alcohol) for each of the three sessions. The heart rate and vagal tone index (V) response patterns were different to alcohol than to the mixer or placebo. The treatments did not differentially influence pulse transit time. The results indicated that the acute effect of a moderate dose of alcohol on the heart is parasympathetically (i.e., vagally) mediated and has no significant direct sympathetic component.

Adult↗
PubMed1989

Lactate and hyperventilation substantially attenuate vagal tone in normal volunteers. A possible mechanism of panic provocation?

Many aspects of panic attacks, eg, palpitations, tremor, sweating, and an emotional sense of "fear," have been theorized to arise from sympathetic nervous system activation. However, most studies have not demonstrated clearly increased levels of catecholamines during an attack, which is contrary to this hypothesis. To explore another possible cause for the physiological changes known to occur during a panic attack, we assessed parasympathetic nervous system activity by measuring vagal tone during treatments known to produce panic symptoms: sodium lactate administration and hyperventilation. Our findings showed a marked reduction in vagal tone during both procedures. We postulate that withdrawal of parasympathetic activity may explain some of the physiological changes occurring in panic attacks and be contributing to the origin of panic.

Adult↗
PubMed1988

Effects of soft tissue mobilization (Rolfing pelvic lift) on parasympathetic tone in two age groups.

The effects of a soft tissue mobilization procedure, the Rolfing pelvic lift, on parasympathetic tone was studied in healthy adult men. Parasympathetic tone was assessed 1) by quantifying the amplitude of the respiratory sinus arrhythmia from the heart rate pattern and 2) by measuring heart rate. Heart rate patterns were assessed during the pelvic lift and during the durational touch and baseline control conditions. Two groups of healthy subjects were tested: Group 1 contained 20 subjects aged 26 to 41 years, and Group 2 contained 10 subjects aged 55 to 68 years. In Group 1, the pelvic lift elicited a somatovisceral-parasympathetic reflex characterized by a significant increase in parasympathetic tone relative to durational touch and baseline conditions. Group 2 did not exhibit a parasympathetic change during the pelvic lift. The results of this study contribute to our understanding of pelvic mobilization techniques and may help to explain why these techniques have been clinically successful in treating myofascial pain syndromes and other musculoskeletal dysfunctions characterized by reduced parasympathetic tone and excessive sympathetic activity.

Adult↗
PubMed1988

Shifts in pelvic inclination angle and parasympathetic tone produced by Rolfing soft tissue manipulation.

The effects of soft tissue manipulation (Rolfing method) were evaluated on young healthy men using two dependent variables: 1) angle of pelvic inclination and 2) parasympathetic activity. Pelvic inclination was assessed by determining the angle of standing pelvic tilt (SPT) with an inclinometer. Autonomic tone was assessed by a measure of cardiac vagal tone (amplitude of respiratory sinus arrhythmia) derived from monitoring heart rate. Thirty-two subjects, preselected for exhibiting an anteriorly tilted pelvis, were randomly assigned to either an Experimental Group (n = 16) that received a 45-minute Rolfing pelvic mobilization session or a Control Group (n = 16) that received a 45-minute control session without manipulation. Dependent variables were assessed before the 45-minute session, immediately after the session, and 24 hours later. Comparing pretest to posttest assessments, the Experimental Group demonstrated a significant decrease in SPT angle and a significant increase in vagal tone. The Control Group did not show significant pretest or posttest differences. The results provide theoretical support for the reported clinical uses of soft tissue pelvic manipulation for 1) certain types of low back dysfunction and 2) musculoskeletal disorders associated with autonomic stress.

Adult↗
PubMed1988

Newborn pain cries and vagal tone: parallel changes in response to circumcision.

Clinical studies have demonstrated that the cries of chronically stressed, medically compromised infants are characteristically higher and more variable in pitch than those of healthy infants. Other studies have indicated that the vagal tone of chronically stressed infants is significantly reduced in comparison to that of normal infants. A neural model of cry production has been proposed which suggests that decreased vagal tone among infants at risk may, in fact, be related to these increases in cry pitch. Using routine, unanesthetized circumcision as a model of stress, we were able to examine the relation between cry acoustics and vagal tone in normal, healthy newborns undergoing an acutely stressful event. Vocalizations, heart, and respiratory waveforms were continuously recorded from 49 (32 experimental; 17 control) 1-2-day-old, full-term infants during preoperative, surgical, and postoperative periods. Vagal tone, as measured by the amplitude of respiratory sinus arrhythmia extracted from heart period data, was significantly reduced during the severe stress of circumcision, and these reductions were paralleled by significant increases in the pitch of the infants' cries. In addition, individual differences in vagal tone measured prior to circumcision surgery were predictive of physiological and acoustic reactivity to subsequent stress. These results emphasize the potential role of vagal control of the autonomic nervous system during stress.

Acoustics↗
PubMed1987

Atropine sulfate effects on aviator performance and on respiratory-heart period interactions.

In this study, 20 human volunteers received a placebo and atropine doses of 0.5, 1.0, 2.0, and 4.0 mg X 75 kg-1 in a Latin Square double blind design, and effects were monitored for 3 h postinjection. The 2.0 mg and the 4.0 mg doses resulted in significant flight simulator performance decrements beginning at 1 h postinjection with only minimal recovery by 3 h postinjection. Electrocardiogram data were used to estimate the amplitude of respiratory sinus arrhythmia (RSA) which was more sensitive than mean heart period or mean heart period variance to the effects of atropine. These parasympathetic effects were relatively rapid in onset and peaked within the first 40-min period for the 2.0 and 4.0 mg doses. The onset of performance effects were delayed 1 h 40 min for the 2.0 mg and 1 h 00 min for the 4.0 mg treatment.

Adult↗
PubMed1985

The relation between neonatal heart period patterns and developmental outcome.

Developmental psychophysiologists have long been interested in a means for evaluating infants at risk for cognitive disabilities. The current research addressed the utility of a noninvasive measure of cardiac vagal tone in predicting developmental outcome. At 40 weeks conceptional age, 3 min of resting EKG were recorded from 80 infants. Four groups of infants were evaluated: prematures who had no medical complications in the postnatal period; prematures who experienced respiratory distress syndrome during the postnatal period; term infants who experienced birth asphyxia during labor and/or postdelivery; and healthy term infants. The mental scale of the Bayley Scales of Mental Development was administered at 8 and 12 months conceptional age. Heart period data were analyzed to derive mean heart period, heart period variability, and estimates of vagal tone for each subject. Analyses of the relationship between the heart period variables and 8- and 12-month outcome (i.e., Bayley Scales) indicated that infants with high vagal tone at 40 weeks conceptional age always had positive developmental outcome at both eight and 12 months of age. Infants with low vagal tone had varied outcomes. Measures of medical complications and other measures of heart period variability were not related to developmental outcome. The results suggest that measurement of cardiac vagal tone may provide an important means for assessing risk in birth stressed populations.

Asphyxia Neonatorum↗