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Biomedical subjects

R T Brouillette

Publications and source records attributed to R T Brouillette.

82 records · Page 5Linked to original sources
PubMed1981

Coordination of breathing and swallowing in human infants.

Spontaneous nonfeeding swallows taken during wakefulness and sleep were identified in nine preterm infants by characteristic patterns in pharyngeal pressure, submental electromyogram, and respiratory airflow. Two hundred and seventeen swallows during ongoing respiration interrupted either inspiratory or expiratory airflow with airway closure for approximately 1 s. The duration of airway closure was independent of respiratory rate. A brief "swallow-breath" was associated with swallow onset in most instances. The respiratory nature of this movement was confirmed by simultaneous recording of a fall in pharyngeal or esophageal pressure and outward movement of the abdomen. Prolongation of the respiratory cycle was generally observed when a swallow interrupted ventilation at higher lung volumes, i.e., in late inspiration or early expiration. When the swallow interrupted ventilation at lower lung volume, i.e, in late expiration or early inspiration, the subsequent inspiratory effort was usually obstructed as it preceded airway opening at the end of the swallow synergism.

Deglutition↗
PubMed1981

Diminished hypoxic ventilatory responses in near-miss sudden infant death syndrome.

The ventilatory response to hypoxia and to hypercarbia was assessed in 36 near-miss sudden infant death syndrome (N.M SIDS) and 23 control infants. Base-line measurements during non-REM sleep documented no significant difference in respiratory frequency, alveolar CO2 and O2 partial pressure (PAco2 and PAo2) or tidal volume between the N-M SIDS and control infants. In the N.M SIDS group, mean inspiratory flow and minute ventilation (VI) were significantly lower than in the control group (p less than 0.001 and p less than 0.01, respectively), and the slope of the ventilatory response to hypercarbia ((delta VI/Torr Paco2) was only 21 +/- 1.9 (SE) ml.kg-1 min-1 Torr PAco2 compared with 62 +/- 3.5 in controls (p less than 0.001). For both groups, the increase in ventilation with hypoxia appeared linear within the PAo2 range assessed (65-115 Torr) and was therefore expressed as the slope of the delta VI/PAo2 plot (ml.kg-1 min-1 per Torr PAo2). The slope of the hypoxic ventilatory response was significantly less in the N-M SIDS than in the control group, -8.3 +/- 1.0 VS. -19.9 +/- 1.5, respectively (p less than 0.001). In summary, in comparison to control infants, N-M SIDS infants as a group have a significantly smaller increase in VI in response to hypoxia as well as to hypercarbia.

Arousal↗
PubMed1981

Evaluation of response time of a transcutaneous oxygen tension electrode.

Response characteristics of a transcutaneous PO2 electrode to step changes in PaO2 were determined. In vitro lag time and 95% response time of a transcutaneous PO2 monitor were compared to in vivo response. Release of arterial occlusion was used to produce rapid local PaO2 changes in human infants and adults. In vitro lag time and 95% response time varied according to whether an increment or decrement in PO2 was produced. In vivo 95% response time of this electrode was two to six times slower than previous estimates, and it varied significantly with the magnitude of the step change, subject age, anatomic location, and local hemodynamic factors. Also, we found that in vivo lag time is two to three times faster than previously reported.

Adult↗
PubMed1980

Hiccups in infants: characteristics and effects on ventilation.

Twenty-seven polygraphic recordings of respiration were obtained on 20 infants, providing data on the frequency, distinguishing features, and medical significance of hiccupping episodes. Eight hiccupping episodes were recorded in seven subjects. The mean duration of the spells was 8.4 +/- 4.2 (SD) minutes. Unintubated subjects, not selected because they were hiccupping, hiccupped 2.5% of the time that they were monitored. Each hiccup was a brief, powerful inspiratory muscle contraction. In unintubated subjects, hiccups were marked by upper airway obstruction, whereas in intubated patients, hiccups were unobstructed inspirations. In unintubated subjects, hiccups were associated with an increase in obstructed eupneic breaths and with decreases in respiratory frequency and minute ventilation; in three subjects hiccups precipitated episodes of mixed apnea. In intubated patients, hiccupping spells were characterized by hyperventilation and respiratory alkalosis. Two types of ECG artifacts were seen with hiccups: high-frequency spikes, mimicking abnormal QRS complexes, and low-frequency waves. From these studies, it appears that hiccups occur frequently in young infants and may affect breathing in clinically significant ways.

Alkalosis, Respiratory↗
PubMed1980

Upper airway patency in the human infant: influence of airway pressure and posture.

We have determined the influence of transmural pressure and neck posture on upper airway patency in infants after death. In natural resting postures, the airway was closed at transmural pressures not exceeding those normally seen during peak inspiratory airflow in the living infant, implying that a neuromuscular mechanism is necessary to maintain airway patency during life. Neck flexion raised closing pressure, making the airway more susceptible to collapse, whereas neck extension lowered closing pressure, making the airway more resistant to collapse. When the angle of flexion was kept constant, closing pressure was not significantly altered by turning the head or positioning the infant prone. Pressures above the corresponding closing pressure were required to reopen the closed airway, suggesting that the walls of the closed airway tended to adhere and implying that surface forces can impose an added load to airway-maintaining musculature during obstructive apnea in the living infant.

Humans↗
PubMed1980

A self-retaining nasal flowmeter for preterm infants.

A nasal flowmeter suitable for preterm infants is described. It is made from a commercially available nasal cannula and 400-mesh stainless steel screen. Low dead space (0.35 ml) and low resistance (1.3 cmH2O . 100 ml-1 . s) are advantages. Light weight and compact design have eliminated the need for extensive restraint of the subject. Also, the investigator need not hold the flowmeter in place. These features make accurate measurement of respiratory airflow and tidal volume possible during polygraphic monitoring studies lasting several hours.

Humans↗
PubMed1980

Control of genioglossus muscle inspiratory activity.

Tonic and phasic inspiratory genioglossus (GG) electromyographic activity (EMG) was recorded from 13 anesthetized rabbits during unstimulated breathing. Integrated GG EMG peaked earlier in inspiration and presented a more rounded contour than integrated diaphragmatic (DIA) EMG. Spontaneous augmented deep inspirations (sighs) showed a biphasic pattern in both GG and DIA EMGs. Hyperventilation abolished phasic inspiratory activity in the GG before the DIA, suggesting that the GG has a higher CO2 apneic point. Hypercapnia increased both EMGs; however, GG EMG increased more, as a percent of base line, than did DIA EMG. Oxygen breathing decreased GG more than DIA EMG; sodium cyanide injection and brief nitrogen breathing increased GG more than DIA EMG; carotid body denervation abolished these responses. Vagotomy abolished the Hering-Breuer inflation-inhibition reflex in both muscles, and tactile, visual, and auditory stimulation increased GG more than DIA EMG. Thus, the GG responses to chemoreceptor input and to nonspecific respiratory stimuli are qualitatively similar but quantitatively different from DIA responses. The relevance to mixed and obstructive apnea is discussed.

Acoustic Stimulation↗
PubMed1979

A neuromuscular mechanism maintaining extrathoracic airway patency.

The ability of the extrathoracic airway (ETA) to remain open when exposed to negative pressure was investigated in rabbits. Postmortem, the ETA collapsed at -6.3 +/- 0.6 cmH2O whereas, during airway occlusion maneuvers in lightly anesthetized animals, it remained patent at pressures as low as -80 cmH2O. This discrepancy suggested that a neuromuscular mechanism maintains ETA patency. Four findings indicated that the genioglossus and geniohyoid muscles, which pull the tongue and hyoid bone anteriorly, help maintain ETA patency: 1) anterior movement of the hyoid bone increased the negative pressure at which the ETA collapsed postmortem, 2) ETA closure during occluded inspirations occurred after 12th nerve section abolished electromyographic activity in these muscles and 3) after deep anesthesia depressed such activity, and 4) closing pressure was linearly related to peak integrated electromyograms of the two muscles. After 12th nerve section, ETA closing pressure became more negative with progressive asphyxia greatly exceeding postmortem closing pressure, which suggests that other muscles also help maintain ETA patency. Blood gas tensions, respiratory system mechanoreceptors, and depth of anesthesia appear to influence genioglossus and geniohyoid activity.

Anesthesia↗
PubMedDate not supplied

Stimulus parameters for phrenic nerve pacing in infants and children.

Phrenic nerve pacing has been used since 1966 to support breathing in quadriplegics and patients with central hypoventilation syndrome (CHS). Recently, using low-frequency, long-inspiratory-time (Ti) stimulation, phrenic nerve pacing has been used successfully to support breathing 24 hours per day in adults and older children. However, no similar experience exists for infants and young children. Therefore, in 27 studies in 14 infants and children we determined the effects of changing Ti and interpulse interval (the inverse of stimulus frequency) on ventilation. Diaphragmatic action potentials, airflow, tidal volume, PACO2 and SaO2 were measured during sleep. Phrenic nerve pacing proved useful in 13 of 14 patients to support breathing either during wakefulness (n = 7) or during sleep (n = 6). We found that adequate ventilation could be achieved at significantly longer interpulse intervals, 95 +/- 25 (mean +/- SD) ms, and shorter Ti, 580 +/- 80 ms, than previously reported. At an average respiratory rate of 21 +/- 8 breaths/min it was thus possible to maintain adequate ventilation despite a marked reduction in the number of phrenic nerve stimuli. Theoretically, these reductions in phrenic nerve stimulation should minimize the chance of pacing-induced diaphragmatic damage. These results suggest that 24 hour per day phrenic nerve pacing may be a realistic goal in selected infants and children.

Diaphragm↗