Specialty versus generalist care of children with appendicitis: an outcome comparison.

BACKGROUND/PURPOSE: Some Health Maintenance Organizations (HMO) limit access of their members to specialists to lower costs. The purpose of this study is to determine whether this policy affects the outcome of children with appendicitis. METHODS: At a large academic medical center, children 17 years or younger with appendicitis were treated either by an HMO Adult General Surgical Service (group A) or a Pediatric Surgical Service (group B). Board certified pediatric surgeons were not available on the HMO surgical service. Anesthesia, surgical residents, nursing, and ancillary support services were identical in both groups. Study parameters included imaging tests performed, operation type, complications, readmissions, and length of stay. Results were analyzed using chi(2) and Fischer's Exact tests. RESULTS: One-hundred seventy-five consecutive children underwent appendectomy, 96 in group A and 79 in group B. In patients with simple acute appendicitis, there was no significant difference between group A and group B for complications, readmissions, second operation, or length of stay. In patients with gangrenous or perforated appendicitis there was a significant difference between group A and group B for type of operation (laparoscopic appendectomy, group A, 4 of 27 v. group B, 0 of 34; P =.04); complications (group A, 9 of 27 v. group B, 3 of 34; P =.025); readmissions (group A, 6 of 27 v. group B, 0 of 34; P =.001); second operation (group A, 6 of 27 v. group B, 2 of 34; P =.001); and mean total length of stay in days (group A, 8.6 of 27 v. group B, 5.4 of 34; P =.05). CONCLUSIONS: Children with significantly perforated appendicitis have lower complication rates and shorter lengths of hospital stay when treated by pediatric surgeons as compared with HMO adult general surgeons.

An electronic simulator for testing infant apnoea monitors that uses actual physiologic data.

An electronic simulator of physiologic signals used in infant monitoring has been designed, constructed and applied in the Collaborative Home Infant Monitor Evaluation (CHIME). A unique feature of the simulator is that it contains actual physiologic waveforms recorded from infants rather than artificial, idealized signals. The simulator stores breathing waveforms that can be used to test transthoracic-impedance- and inductance-plethysmography-based monitors, and heart rate channels are tested by playing a neonatal QRS complex at preset fixed rates or a variable rate as determined from infant recordings. The transfer characteristics of the simulator are constant over frequencies ranging from 0.5 to 8 Hz for the respiration channels. Data stored in memory are divided into 60 second epochs that can be presented to the monitor being tested in a programmable sequence. A group of 66 CHIME monitors was tested using a simulator programmed with 17 apnoea and bradycardia waveforms. The agreement between monitors as to the duration of detected apnoea decreases as the amount of artefact in the signal increases. Discrepancies between monitors in detecting apnoea duration were found to be similar to inconsistencies between CHIME investigators manually scoring similar waveforms.

Recurrent hypoxic exposure and reflex responses during development in the piglet.

The effects of recurrent hypoxia on cardiorespiratory reflexes were characterized in anesthetized piglets at 2-10 d (n=15), 2-3 weeks (n=11) and 8-10 weeks (n=8). Responses of phrenic and hypoglossal electroneurograms (ENG(phr) and ENG (hyp)) to hypoxia (8% 0(2), bal N(2), 5 min), hypercapnia (7% CO(2) bal O(2), 5 min) and intravenous capsaicin were tested before and after recurrent exposure to 11 episodes of hypoxia (8% O(2) bal N(2), 5 min). In piglets 2-10 d, ENG(phr) response to hypoxia declined in proportion to the number of hypoxic exposures; however, ENG (hyp) response to hypoxia was unchanged. In piglets at 2-10 d, intracisternal injection of bicuculline (GABA(A) receptor antagonist) reversed effects of recurrent hypoxia on ENG(phr) hypoxic response, eliminated apnea during hypoxia, as well as the delay in appearance of ENG(phr) after hypoxia. The ENG(phr) response to 7% CO(2) inhalation also decreased after recurrent hypoxia; however, the ENG(phr) response to C-fiber stimulation by capsaicin was unaltered. Piglets at 2-3 and 8-10 weeks were resistant to the depressive effects of recurrent hypoxia on respiratory reflex responses. We conclude that the response of the anesthetized newborn piglet to recurrent hypoxia is dominated by increasing inhibition of phrenic neuroelectrical output during successive hypoxic exposures. Central GABAergic inhibition may contribute significantly to the cumulative effects of repeated hypoxia in the newborn piglet experimental model.

Intussusception.

Intussusception is the invagination of one portion of the intestine into another and is the most common form of intestinal obstruction in infants. This report reviews the clinical presentation and diagnostic and treatment options available for intussusception. The etiologies of childhood intussusception are discussed. Details and literature review are provided on the advantages and disadvantages of ultrasonography, barium enema, air contrast enema, and surgery in the diagnosis and treatment of intussusception.

Impact of sonography on the diagnosis and treatment of acute lower abdominal pain in children and young adults.

OBJECTIVE: Our purpose was to evaluate the impact of sonographic data on clinical physicians' diagnostic confidence and their treatment of children and young adults with acute lower abdominal pain. SUBJECTS AND METHODS: Senior surgical and emergency department staff completed questionnaires before and after abdominal sonography was performed on 94 of 101 consecutive children and young adults with acute lower abdominal pain, pelvic pain, or both. Physicians who were unaware of sonographic data stated the most likely diagnosis and their level of confidence in their diagnosis and then formulated clinical plans. After they were given sonographic data, physicians again stated the most likely diagnosis, estimated their level of confidence, and formulated revised treatment plans. RESULTS: Sonographic data resulted in revised clinical diagnoses in 52% of the patients. Overall, the gain in diagnostic confidence for the entire study population was 33% (95% confidence interval [CI], 27-38%; p < .0001). The impact on the physicians' confidence was greater in those children and young adults whose diagnoses changed after sonography (mean increase in physicians' confidence, 48.3%; 95% CI, 47-75%). In patients whose diagnoses were not changed after sonography, the mean increase in physicians' confidence was 17.6% (95% CI, 11-24%; p < .0001 [analysis of variance]). Physicians used sonographic data to change initial treatment plans in 43 patients (46%). Of these 43 patients, a lower intensity of care was given to 30 patients (70%) and a higher intensity to 13 patients (30%). CONCLUSION: Sonographic data frequently changed initial clinical diagnoses, thus increasing diagnostic confidence and changing clinical treatment decisions in the setting of acute lower abdominal pain in children and young adults.

Insulin-like growth factor-I gene expression in three models of accelerated lung growth.

BACKGROUND/PURPOSE: We have learned previously that in utero tracheal ligation reverses the structural and physiological effects of surgically created congenital diaphragmatic hernia. In addition, we have discovered that postnatal lung growth similarly can be accelerated using liquid-based airway distension with perfluorocarbon. Another model of accelerated lung growth is that of compensatory growth seen after neonatal pneumonectomy. In all of these models, growth has occurred because of an increase in alveolar number rather than enlargement of preexisting alveoli. However, the molecular mechanisms underlying these processes remain unknown. The purpose of this study was to determine if gene expression could be altered by changes in physical forces in the prenatal and postnatal lung. METHODS: The three models of accelerated lung growth studied were the following: (1) The prenatal group, consisted of fetal lambs (n = 12) that underwent the surgical creation of a left diaphragmatic hernia at 90 days' gestation. Six of these animals also underwent simultaneous tracheal ligation. (2) The PFC group consisted of five neonatal animals that underwent isolation of the superior segment of the right upper lobe, with intrabronchial distension with perfluorocarbon to 7 to 10 mm Hg pressure for a 3-week period. (3) The postpneumonectomy group consisted of four neonatal animals that underwent left pneumonectomy. In the fetal study, lungs were retrieved at term (130 days), and in the postnatal study, lungs were retrieved 3 weeks after initial intervention. In all cases, RNA was extracted from snap-frozen lung samples and Northern blot analysis performed. RESULTS: Insulinlike growth factor-I, insulinlike growth factor-II, and vascular endothelial growth factor gene expression were analyzed by densitometry. Insulinlike growth factor-I gene expression was found to be decreased in association with experimental diaphragmatic hernia (P = .005), but restored to normal with tracheal ligation. Insulinlike growth factor-I gene expression was significantly increased in both postnatal models of accelerated lung growth (P = .022, P = .016). No significant differences were found in insulinlike growth factor-II or vascular endothelial growth factor gene expression. CONCLUSIONS: The authors conclude from these preliminary data that (1) insulin like growth factor-I gene expression is reduced in experimental fetal diaphragmatic hernia and restored to normal by tracheal ligation, and (2) insulinlike growth factor-I gene expression is increased in both the liquid-based airway distension and postpneumonectomy models of accelerated postnatal lung growth. The authors speculate that all of these manipulations exploit a natural pathway essential for normal lung growth.

Persistence of the biphasic ventilatory response to hypoxia in preterm infants.

OBJECTIVE: To characterize postnatal maturation of the biphasic ventilatory response to hypoxia in order to determine whether it persists beyond the first weeks of life in preterm infants, and the contributions of respiratory frequency and tidal volume to this response. METHODS: Stable preterm infants were studied at two postnatal ages, 2 to 3 weeks (n = 12) and 4 to 8 weeks (n = 12), before hospital discharge at 35 weeks (range, 33 to 38 weeks) of postconceptional age. Infants were exposed to 5 minutes of 15% (or 13%) inspired oxygen; ventilation, oxygen saturation, end-tidal partial pressure of carbon dioxide, and heart rate were simultaneously recorded. RESULTS: Minute ventilation exhibited a characteristic biphasic response to hypoxia at both postnatal ages, regardless of the development of periodic breathing. At both ages there was a transient increase in tidal volume, which peaked at 1 minute, accompanied by a sustained decrease in respiratory frequency as a result of significant prolongation of expiratory time. CONCLUSION: The characteristic biphasic ventilatory response to hypoxia persists into the second month of postnatal life in preterm infants. We speculate that this finding is consistent with the prolonged vulnerability of such infants to neonatal apnea.

Continuous intrapulmonary distension with perfluorocarbon accelerates neonatal (but not adult) lung growth.

BACKGROUND/PURPOSE: We have previously demonstrated that experimental fetal tracheal ligation reverses the structural and physiological effects of pulmonary hypoplasia associated with congenital diaphragmatic hernia. The purpose of this study was to determine if lung growth could be similarly accelerated postnatally by continuous liquid-based intrapulmonary distension. METHODS: Ten neonatal lambs were divided into two experimental groups. Five neonatal animals underwent a right thoracotomy with isolation of the anterior superior segment of the right upper lobe. A pressure monitoring catheter was introduced and perfluorocarbon (PFC) was instilled into the segment. Animals were subjected to a 21-day distention period with continuous maintenance of 7 to 10 mm Hg intrabronchial pressure. Five other neonatal animals used as age- and weight-matched controls were killed immediately after distension with PFC to 7 to 10 mm Hg. To evaluate the effect of age on postnatal growth, identical procedures were performed on seven mature sheep. Four adult animals underwent a 21-day distension with PFC, and three animals were killed immediately after PFC distension. RESULTS: Neonatal animals who underwent distension showed a significant acceleration of lung growth based on right upper lobe volume to body weight ratio (P = .0019), total alveolar number (P = .003), and total alveolar surface area (P = .006), when compared with controls. Alveolar growth was attributed to an increased alveolar number rather than increased alveolar size based on a normal histological appearance, normal airspace fraction (P = NS), and normal alveolar numerical density (P = NS). In contrast, no significant differences in lung growth or maturation indices were present in adult animals. CONCLUSIONS: From this preliminary data we conclude: (1) Liquid-based airway distension does accelerate postnatal lung growth, (2) lung architecture remains normal during this period of accelerated growth, (3) adult sheep do not respond to liquid-based airway distension with lung growth, and (4) prolonged exposure to intrapulmonary PFC appears to be safe. We speculate that stretch is the stimulus for lung growth because there are no known growth factors present in PFC.

Assessment of tidal volume over time in preterm infants using respiratory inductance plethysmography, The CHIME Study Group. Collaborative Home Infant Monitoring Evaluation.

Non-invasive techniques for monitoring ventilation in infants are widely used in short-term laboratory-studies but have not been evaluated in routine clinical settings. To determine whether respiratory inductance plethysmography (RIP) can provide reproducible measurements of tidal volume (VT) in premature infants over an extended period of time, we monitored respiration in eight healthy preterm infants over 4.9 +/- 1.0 hours (mean +/- SD). The algebraic sum (Sum) of rib cage (RC) and abdominal (AB) motion signals (obtained by RIP) was calculated and presented over the entire recording period as percent of an initial 5 minute calibration period. VT was simultaneously measured with a nasal mask pneumotachometer with infants in prone and supine positions during active and quiet sleep. Infants were studied in the morning (AM) and again in the afternoon (PM). Between these studies they were returned to the nursery wearing the RIP in a continuous record mode. For all patients there was a significant linear relationship between VT (in mL measured by pneumotachometer) and Sum (in % of calibration value, RIP). Neither the slope of the relationship (0.074 +/- 0.03 in AM vs. 0.071 +/- 0.02 in PM), nor its variability as measured by standard error of the estimate (SEE) (2.3 +/- 0.5 in AM vs. 2.5 +/- 0.8 in PM) changed significantly from AM to PM. The relationship between VT and Sum, as well as the variability of that relationship, was not altered by position, asynchrony of RC and AB, respiratory rate, or percent RC contribution to Sum. We conclude that RIP produces consistent measurements of respiratory effort over 5 hours in healthy preterm infants without need for recalibration and is not affected by routine care.

Vulnerability of respiratory control in healthy preterm infants placed supine.

OBJECTIVE: We tested the hypothesis that healthy preterm infants have attenuated ventilatory responses to hypercapnia, associated with a decreased rib cage contribution to ventilation, in the supine versus prone position. STUDY DESIGN: We elicited hypercapnic ventilatory responses from 19 healthy preterm infants (postconceptional age 35 +/- 1 weeks) who were being prepared for hospital discharge. The O2 saturation was continuously monitored. Before and during CO2 rebreathing, ventilation was measured with a nasal mask pneumotachygraph and was derived from chest wall motion as determined by respiratory inductance plethysmograph. This measuring method allowed us to compare both ventilation and the percentage rib cage contribution to ventilation between supine and prone positions. Statistical analysis employed analysis of variance with repeated measures. RESULTS: The supine position was associated with a higher respiratory rate (p < 0.02) and lower O2 saturation (p < 0.007) than the prone position. The increase in ventilation in response to hypercapnia was lower in the supine than in the prone position. This was statistically significant for the respiratory inductance plethysmograph (p < 0.008) but not the pneumotachygraph (p = 0.077), and was associated with a smaller rib cage contribution to ventilation in the supine than in the prone position (p < 0.0001). CONCLUSION: Respiratory control may be vulnerable when healthy preterm infants are placed supine. Widespread avoidance of the prone position may not be appropriate for such patients.

Experimental fetal tracheal ligation and congenital diaphragmatic hernia: a pulmonary vascular morphometric analysis.

The authors have previously shown that fetal tracheal ligation (TL) reverses the pulmonary hypoplasia in experimental diaphragmatic hernia (DH) by accelerating fetal alveolar growth. The purpose of this study was to determine if growth of the accompanying macroscopic and microscopic pulmonary vasculature is also accelerated. Eighteen fetal lambs were divided into three experimental groups: diaphragmatic hernia (DH), DH and simultaneous tracheal ligation (DH/TL), and sham-operated controls (C). Animals were delivered near term, the lungs retrieved, and pulmonary capillary growth (5 to 50 microns in diameter) evaluated by standard morphometric techniques. Capillary ultrastructure was evaluated by electron microscopy. Nine additional fetal lambs of the same gestational age were equally divided into the same three groups and their lungs analyzed by pulmonary arteriography for evaluation of large vessel growth (< 100-microns diameter). Computer digital analysis of angiogram lung slices showed that the total area of large vessels was increased in DH/TL lungs when compared with DH lungs and decreased in DH lungs when compared with C lungs (P = .003); however, the ratio of large vessel area per unit of lung area was similar in all groups. Microscopic morphometry of the capillary bed showed that the total number of capillaries was increased in DH/TL lungs over both DH and C lungs (P = .0001); however, the number of capillaries per alveolus (cap/alv) was similar in all groups. In DH/TL lungs, electron microscopy showed normal capillary wall structure and normal thickness of the capillary-alveolar interface, whereas in DH lungs, capillary structure was abnormal and the capillary-alveolar interface was thickened.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of swallowing during apnea and periodic breathing in premature infants.

Periodic breathing and apnea are two forms of ventilatory instability which are commonly observed in premature infants. This study was undertaken to characterize the pattern of swallowing during apnea and compare this pattern to that present during breathing. We assessed the frequency and distribution of swallows during the respiratory pauses of apnea and periodic breathing in 22 premature infants birth weight 1.2 +/- 0.2 kg, postconceptional age 34 +/- 2 wk. Twelve infants had apnea and 10 exhibited periodic breathing. During sleep the pharyngeal phase of swallowing was detected by a catheter in the pharynx and esophageal peristalsis by an esophageal pressure catheter. Nasal airflow was monitored by a pneumotachometer. During apnea, the frequency of swallows was significantly greater than during the respiratory pauses of periodic breathing (15.9 +/- 8.2 versus 0.72 +/- 0.73 swallows/min, respectively, p < 0.0001) and also much higher than the rate of spontaneous swallows during sleep in either group (0.66 +/- 0.66 and 0.58 +/- 1.08 swallows/min, respectively). We conclude that an increased rate of swallowing is characteristic of apnea in premature infants, and distinguishes apnea from the respiratory pauses of periodic breathing.

Nasogastric tube placement: effects on breathing and sucking in very-low-birth-weight infants.

Eighteen very-low-birth-weight (VLBW) infants who met study criteria were observed during routinely scheduled feedings, twice in one day, once with a nasogastric (NG) tube and once without, in random order. Breathing and sucking measurements were compared with and without NG tube placement. During the prefeed period, minute ventilation and tidal volume were significantly lower with an NG tube than without the tube. During the continuous sucking (CS) period after commencement of oral feeding, minute ventilation, tidal volume, pulse rate, and oxygen saturation were also lower with the tube. During both CS and subsequent intermittent sucking periods, infants sucked less forcefully and took less formula with the tube. Based on these findings, if VLBW infants have an NG tube in place, clinicians are urged to monitor for breathing compromise, oxygen desaturation, and bradycardia during oral feeding.

Lung development.

Human lung development is divided into five stages: embryonic, pseudoglandular, canalicular, saccular, and alveolar. The boundaries between these stages are not sharp; rather, overlap occurs between various gestational ages and individuals. The anatomic and morphological characteristics of each stage are described; general principles of lung development and cytodifferentiation of type I and type II pneumocytes are discussed. The complex phenomenon of lung development incorporates two processes--lung growth and lung maturation. Although these processes are developmentally related, they appear to be separately controlled. Lung growth seems to be influenced primarily by physical factors such as intrathoracic space, lung liquid volume and pressure, and amniotic fluid volume among others. Special attention is given to fetal lung liquid dynamics and the effects of its manipulation on lung growth, particularly by tracheal occlusion. Lung maturation has two components--structural and biochemical (ie, surfactant). Structural lung maturation appears to be regulated by physical factors. Physical factors that produce hypoplasia produce structurally immature lungs, whereas physical factors that produce hyperplasia produce structurally mature lungs. Biochemical maturation appears to be hormonally regulated by several endocrine organs (pituitary, adrenal, thyroid) and a host of endocrine factors including corticotropin, cortisol, thyroid hormones, and others.

Experimental fetal tracheal ligation reverses the structural and physiological effects of pulmonary hypoplasia in congenital diaphragmatic hernia.

Infants with congenital diaphragmatic hernia (DH) and profound pulmonary hypoplasia are currently unsalvageable. The authors previously demonstrated that tracheal ligation (TL) accelerates fetal lung growth and reverses the pulmonary hypoplasia of fetal nephrectomy. The purpose of this study was to determine if the pulmonary hypoplasia of experimental DH could be similarly reversed and, if so, whether the resulting lungs would show better function than those of their DH counterparts. Eighteen fetal lambs were divided into three experimental groups of six animals each. In group 1, DH was created at 90 days' gestation. In group 2, DH was created at 90 days' gestation and TL performed during the same operation. Group 3 consisted of sham-operated controls. These animals were delivered near full-term, and their lungs analyzed by standard morphometric techniques. Ten additional fetal lambs were divided into two experimental groups of five animals each. In group 4, DH was created at 90 days' gestation. In group 5, DH was created at 90 days' gestation and TL performed 20 days later, at 110 days' gestation. These animals were pressure-ventilated via tracheostomy over a 2-hour period in which PaO2, PaCO2, and compliance were measured. Intratracheal pressure (ITP) was measured at the time of delivery in all groups. Upon retrieval, DH animals had abdominal viscera in the chest and small lungs; in contrast, DH/TL animals had the herniated viscera reduced from the chest by enlarged lungs. DH/TL lungs showed markedly increased growth, with significant increases in lung volume:body weight ratio (LV:BW; P = .0001), alveolar surface area (ALV.SA; P = .0001), and alveolar number (ALV#) (P = .0001) when compared with those of the DH or control group. This growth was associated with a normal maturation pattern based on histological appearance, normal airspace fraction, and normal alveolar numerical density. ITP in the DH/TL group was increased when compared with that of DH and control animals (P = .0001). Total lung DNA and protein were both elevated in the DH/TL animals (P = .0001). However, the DNA:protein ratio remained normal, suggesting lung growth had occurred through cell proliferation, not by hypertrophy. When ventilated over a range of settings, DH/TL lungs were more compliant (P = .0001) and achieved higher PaO2s (P < .003) and lower PaCO2s (P = .0001) than their DH counterparts. From these data, the authors conclude: (1) Experimental fetal DH produces hypoplastic lungs that are not capable of adequate gas exchange with conventional ventilation.(ABSTRACT TRUNCATED AT 400 WORDS)

Experimental fetal tracheal ligation prevents the pulmonary hypoplasia associated with fetal nephrectomy: possible application for congenital diaphragmatic hernia.

Pulmonary hypoplasia has a definite clinical impact in a variety of congenital diseases such as renal dysplasia and congenital diaphragmatic hernia. These diseases have in common inadequate growth and development of fetal lungs. Previous reports have demonstrated increased lung growth with in utero tracheal ligation. The purpose of this study was to determine if lung growth can be accelerated in the setting of experimental pulmonary hypoplasia. Ninety-five-day gestation fetal sheep were divided into four experimental groups: nephrectomy, nephrectomy with tracheal ligation, tracheal ligation alone, and sham-operated control animals. Animals were delivered near term and their lungs inflation fixed at 25 cm H2O. Total alveolar number (Alv#), total alveolar surface area (AlvSA), and lung volume to body weight ratios (LV:BW) were determined for apical and basilar segments of each animal and then averaged. Total lung DNA and protein content were also analyzed. The nephrectomy group had smaller lungs than control animals with decreased Alv#, AlvSA, and LV:BW. In contrast, nephrectomy with tracheal ligation produced large lungs which had increased Alv#, AlvSA, and LV:BW when compared with both the nephrectomy and the control group (P < .01). Total lung DNA and protein concentrations were both markedly elevated in the tracheally obstructed groups. However, the DNA/protein ratios remained constant in all four groups, suggesting that lung growth had occurred through cell multiplication. Photomicrographs of the lung demonstrated a histologically immature appearance in the nephrectomy group and a histologically mature appearance in the tracheally obstructed groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in resistance and ventilatory timing that accompany apnea in premature infants.

To characterize the changes in respiratory mechanics and ventilatory timing that accompany apnea in premature infants, we evaluated 36 apneas in 13 premature infants (birth weight, 1,200 +/- 350 g, postconceptional age at study 34 +/- 3 wk). Apnea was defined as a ventilatory pause > or = 10s accompanied by a decrease in heart rate of 20 beats/min. Nasal airflow was recorded with a pneumotachometer, and esophageal, pharyngeal, and nasal mask pressures were continuously measured. Inspiratory time (TI), expiratory time (TE), tidal volume (VT), and VT/TI were determined over five breaths before and after apnea. In addition, total pulmonary resistance (RT) and supraglottic resistance (Rs) were measured over the same epochs in inspiration and expiration. Before apnea, TE and RT increased (P < 0.05 and < 0.01, respectively); however, Rs did not change. Immediately after apnea, prolongation of TI occurred and both RT and Rs were increased (P < 0.01), consistent with continued upper airway instability. However, within two breaths after resolution of the apnea, RT and Rs returned to normal, reflecting rapid recovery of upper airway and total pulmonary resistance. The ventilatory changes that precede and follow apnea closely resemble those occurring during periodic breathing.

Increased respiratory drive as an inhibitor of oral feeding of preterm infants.

This study was designed to determine whether increased respiratory drive induced by inhalation of carbon dioxide would alter the reflex and voluntary components of feeding. For 10 preterm infants (mean +/- SD: postconceptional age at study, 34 +/- 2 weeks; weight, 2.1 +/- 0.2 kg), four trials of nutritive feeding were offered: two while the infants were inhaling a gas mixture containing 40% oxygen and two while the infants were breathing 40% oxygen and 7% carbon dioxide. Nasal airflow was monitored with a pneumotachygraph. Pressure-sensitive catheters in the esophagus and in the feeding nipple were used to detect swallowing and sucking. Sucking frequency and pattern, rate of swallowing, end-tidal carbon dioxide, and minute ventilation were recorded for 30-second epochs during feeding. When the inhaled gas mixture was switched from 40% oxygen to 40% oxygen and 7% carbon dioxide, sucking frequency decreased from 53 +/- 10 to 48 +/- 12 and from 54 +/- 12 to 40 +/- 19 sucks/min, respectively (p < 0.005). Frequency of swallowing also fell during the two feeding epochs on 7% carbon dioxide, from 45 +/- 15 to 40 +/- 15 and from 43 +/- 14 to 31 +/- 16 swallows/min (p < 0.003). Thus acute hypercapnea was accompanied by a decrease in rate of both sucking and swallowing during nutritive feeding. Increased ventilatory drive may directly inhibit nutritive feeding behavior in premature infants.

Alae nasi activation in preterm infants during oral feeding.

Preterm infants may demonstrate impaired ventilation during oral feeding with resultant hypoxemia and hypercarbia. This study was designed to determine whether infants activate a representative upper airway muscle, the ala nasi, in response to these ventilatory changes. Ten preterm infants (postconceptional age at study 35 +/- 4 wk, weight 2.2 +/- 0.1 kg) were studied during a control period, continuous feeding, subsequent intermittent feeding, and a period of nonnutritive sucking. Nasal airflow was measured with a pneumotachometer to quantify minute ventilation. The alae nasi electromyogram (EMGAN) was recorded with surface electrodes, and sucking pressure was detected by a catheter in the feeding nipple. End-tidal CO2 and O2 saturation were also recorded during each period. The percentage of breaths associated with EMGAN activity increased from 41 +/- 13% during the control period to 95 +/- 5% and 93 +/- 7% during continuous and intermittent sucking, respectively (p < 0.05). Eighty-seven +/- 5% of EMGAN activity occurred during inspiration. During continuous and intermittent sucking, the amplitude of EMGAN activity also increased (6.8 +/- 5.2 and 6.7 +/- 4.0 arbitrary units/breath, respectively) compared with the control period (2.4 +/- 2.8 units/breath, p < 0.05). In association with the increase in EMGAN activity, O2 saturation fell from 98 +/- 1% in the control period to 95 +/- 1% during both continuous and intermittent feeding (p < 0.05), and minute ventilation fell from 274 +/- 80 mL/min/kg during the control period to 190 +/- 81 and 208 +/- 57 mL/min/kg during continuous and intermittent feeding, respectively (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)