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Biomedical subjects

D W Warren

Publications and source records attributed to D W Warren.

At least 127 records · Page 7Linked to original sources
PubMed1987

The relationship between nasal airway cross-sectional area and nasal resistance.

Mouth breathing in response to an impaired nasal airway is thought to have clinical consequences. Physiologically, mouth breathing occurs whenever the body senses that nasal resistance is inappropriately high. In physical terms mouth breathing is a response that enlarges the upper airway and, by doing so, reduces airway resistance. In the past measurements of nasal resistance have been used as an index of airway impairment. Recently, we introduced a technique that estimates cross-sectional size of the airway, a variable that directly determines the magnitude of airway resistance. The purpose of the present study was to determine the precise effects of nasal airway size on nasal airway resistance so that the relationship between the two could be described in mathematic terms. There were two phases to the study--one involving a model and simulated breathing, and the other involving 100 subjects demonstrating normal and impaired nasal airways. The pressure-flow technique for estimation of nasal airway size and nasal airway resistance was used. The following equation was generated from the data: Resistance = 1.9 + (Formula: see text). The relationship between the two variables is nonlinear--that is, size of the airway has its greatest effect on resistance when the airway is less than 0.4 cm2 and a much lesser effect at larger airway sizes. The study also showed that nasal airway resistance generally does not fall very much below 1.9 cm H2O/L/S during breathing even when the airway is very large. This probably relates to the need to maintain an adequate level of airway resistance for alveolar gas exchange.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

The relationship between nasal cross-sectional area and nasal air volume in normal and nasally impaired adults.

The controversy concerning the effects of nasal airway impairment on facial growth has stimulated renewed interest in upper airway respiratory function. The subjective manner in which airway impairment and mouth breathing have been assessed is, in our opinion, responsible for the differences observed among investigators and for their conclusions. We have been involved in a series of studies dealing with airway impairment and have report modifications of two techniques for objectively assessing respiration. The purpose of the present study was to examine a large population of adults, with and without nasal airway impairment, and assess the relationship between nasal cross-sectional area and nasal air volume to determine at what point airway size controls the passage of air during breathing. Statistical analysis of the data demonstrates that airway size alters air volume when nasal cross-sectional area is less than 0.4 cm2. The relationship between area and volume is very linear below 0.4 cm2, with air volume decreasing with decreased size. Although the data do indicate some influence over volume at sizes greater than 0.4 cm2, the effect is very slight. These findings support the prediction that upper airway impairment is present at nasal airways less than 0.4 cm2 in adults.

Adolescent↗
PubMed1987

The nasal airway following maxillary expansion.

There have been suggestions that maxillary expansion may be justified on the basis of airway considerations alone. The present study assessed the effects of rapid maxillary expansion and surgical expansion on nasal airway size to determine how useful these techniques are for breathing purposes. The results demonstrate that both procedures generally improve the nasal airway. However, approximately one third of the subjects in both groups did not achieve enough improvement to eliminate the probability of obligatory mouth breathing. These findings suggest that maxillary expansion for airway purposes alone is not justified.

Adolescent↗
PubMed1987

Regulation of LH receptors and steroidogenesis in the foetal rat testis in vivo.

Foetal rats were injected with high doses of hCG or ovine LH (oLH) to determine if LH receptors were down-regulated and steroidogenesis impaired as is seen in the adult animal. Foetuses injected in utero with 52 micrograms/kg hCG had a prompt increase in intratesticular testosterone, demonstrating that the injected substance reached the foetal testis. Pregnant mothers were laparotomized and each foetus in one uterine horn injected with 52 micrograms/kg hCG. Twenty-four hours later, the foetal testes from both uterine horns were collected and free LH receptor content measured. In foetuses injected with hCG, free LH receptors were significantly reduced. LH receptors in foetal testes from the contralateral horn were not significantly different from those in controls. Foetuses injected with 52 micrograms/kg hCG at 17.5 days of gestation showed a delayed response in LH receptor up-regulation when compared with neonatal rats injected with comparable doses of hCG. Injection of foetal and neonatal rats with 400 micrograms/kg oLH showed no evidence of down-regulation, as is seen in the adult. Testes from foetuses injected with 52 micrograms/kg hCG 3 days earlier showed an increase in both basal and hCG-stimulated testosterone production during 3 h of incubation when compared with controls. These results show that the rat foetal testis in vivo does not demonstrate down-regulation of LH receptors or steroidogenic lesions of the testosterone synthetic pathway when exposed to high levels of hCG as does the adult rat testis. These results from the foetal testis in vivo are in agreement with results obtained from the foetal testis in vitro and the neonatal testis in vivo.

Animals↗
PubMed1987

Inspiratory and expiratory effects of nasal breathing.

The purpose of the present study was to assess quantitatively the nasal valve area during normal inspiratory and expiratory maneuvers. The pressure-flow technique of Warren was used to estimate nasal size in 15 adult subjects who had no previous history of nasal surgery or abnormality. Cross-sectional size of the nasal airway was also assessed (1) after insertion of tubing to eliminate alar effects, (2) after administration of 0.1% Otrivin decongestant to eliminate mucosal effects, and (3) by blocking each nostril individually. Mean areas of 0.63 cm2 +/- 0.17 during inspiration and 0.56 cm2 +/- 0.14 during expiration. This difference is statistically significant (less than 0.01) and the effect was maintained under conditions of occlusion of either nostril, insertion of tubing, and administration of Otrivin. These findings suggest that the nasal valve acts as a respiratory brake during expiration possibly to allow adequate time for gas exchange at the alveoli.

Adult↗
PubMed1986

Measurement of nasal and oral respiration using inductive plethysmography.

The role of nasal respiratory function in oral and facial development remains unclear in spite of the long-standing interest of clinicians. Much of the current controversy stems from our inability to define mouth breathing in objective terms and evaluate nasal airway impairment quantitatively. Recent advances in respiratory monitoring technology provide new opportunities to assess upper airway breathing more objectively. The purpose of this study was to describe a new approach for measuring oral and nasal respiration and to test its reliability. The technique involves inductive plethysmography and the data provide an assessment of respiratory mode without the need to enclose the subject's head in an airtight box. The data were compared to pneumotachography and the results demonstrate the reliability of the technique.

Abdomen↗
PubMed1986

Upper airway pressures during breathing: a comparison of normal and nasally incompetent subjects with modeling studies.

Although there has been considerable interest in the effects of nasal airway impairment on facial growth, the relationship is still unclear. This study examined the effect of nasal airway size on upper airway pressures during breathing. Three phases of data collection were involved. The first phase used a model to describe pressures during simulated normal and impaired respirations. The second phase involved subjects with normal airways, and the third used persons who were judged by an otolaryngologist to be nasally impaired. Aerodynamic assessment techniques were used to measure airway pressures during breathing and to assess nasal airway size. Results of the modeling study suggest that when nasal cross-sectional area is greater than 0.1 cm2, pressures associated with breathing are not excessive. These findings also suggest that slight lip opening (2 to 3 mm) would significantly reduce airway pressures. In addition, pressure magnitudes of the normal and nasally impaired groups were similar to the modeling data, and no significant difference in pressures was observed between the two groups. Accordingly, the assumptions that nasally impaired persons generate abnormal breathing pressures and that these pressures directly influence facial growth are questionable.

Air Pressure↗
PubMed1986

Compensatory speech behaviors in individuals with cleft palate: a regulation/control phenomenon?

The articulation errors associated with velopharyngeal incompetence are of particular interest to clinicians and researchers because the problems they pose usually remain after surgical repair and the reasons they appear may have important implications for speech-motor control. The intriguing question of why individuals develop and maintain such detrimental behaviors has been the focus of our laboratory's attention over the past 25 years. The purpose of this paper is to present a hypothesis dealing with compensatory speech behaviors in cleft palate, provide some data in support of this hypothesis, and project future directions for research. The hypothesis, that speech aerodynamics conform to patterns characteristic of a regulating system, proposes that compensatory behaviors in cleft palate are manifestations of regulation and control strategies.

Airway Resistance↗
PubMed1986

Comparison of Tonar II, pressure-flow, and listener judgments of hypernasality in the assessment of velopharyngeal function.

The purpose of the present investigation was to study the interrelationships among Tonar II, pressure-flow, and listener judgments of hypernasality in a consecutive series of patients. The subjects employed were 124 children and adults seen for evaluation at the University of North Carolina Oral-Facial and Communicative Disorders Program. The results indicated that nasalance scores and clinical ratings of hypernasality change systematically among patients as a function of their pressure-flow categorization. A discussion is presented concerning the impact that differential use of information from these assessment techniques can have upon patient management.

Adolescent↗
PubMed1985

Regulation of infant and developing rat testicular gonadotropin and prolactin receptors and steroidogenesis by treatments with human chorionic gonadotropin, gonadotropin-releasing hormone analogs, bromocriptine, prolactin, and estrogen.

Infant (5-day-old) male rats were treated with hormonal regimens to alter their exposure to gonadotropins, prolactin (Prl), and estrogen, and the response of testicular endocrine functions was measured. Human chorionic gonadotropin (hCG) or a potent gonadotropin-releasing hormone agonist analog (GnRH-A) resulted in a short-lived decrease of testicular receptors (R) for luteinizing hormone (LH), but no deleterious effects were found on testicular capacity to produce testosterone (T), which is a typical response of the adult testis. Only GnRH-A, through probable direct testicular action, induced a relative blockade of C21 steroid side-chain cleavage that was observed in vitro upon hCG stimulation. Human chorionic gonadotropin treatment, but not GnRH-A treatment, increased testicular Prl-R. GnRH antagonist analog (GnRH-Ant) treatment did not affect testicular LH-R, but decreased Prl-R and testicular T production. Decrease of serum Prl by bromocriptine had no effect on testicular LH-R or Prl-R, but slightly decreased T production in vitro. Ovine Prl increased binding sites for LH/hCG. The postnatal rats were insensitive to negative effects of diethylstilbestrol when monitored by testis weight, T, and LH-R. In conclusion, the responses to changes in the hormonal environment differed greatly between infant and adult testes. Mainly positive effects of elevated gonadotropin and Prl levels were seen on infant rat Leydig cell functions. Likewise, decreased tropic hormone levels, and exposure to estrogen, were ineffective in bringing about the inhibitory actions seen in the adult.

Animals↗
PubMed1985

A pressure-flow technique for quantifying temporal patterns of palatopharyngeal closure.

The purpose of this study was to demonstrate a new application of the pressure-flow technique and to determine whether the temporal characteristics of aerodynamic data associated with single-word utterances could reliably differentiate speakers with adequate palatopharyngeal closure from those with inadequacy. The groups included 10 normals, 20 patients with cleft palate who had adequate closure (0.0-0.09 cm2), 20 patients who had borderline closure (0.10-0.19 cm2), and 20 patients who had inadequate closure (greater than 0.19 cm2). The test sound was the nasal-plosive blend /mp/ in the word hamper. The data were processed by a PDP 11/34 computer. The results demonstrate the utility of the pressure-flow technique for studying timing parameters associated with speech and reveal that patients with adequacy of closure can be differentiated from those with inadequacy using timing criteria. Additionally, the data suggest that the perception of nasal resonance in the group with borderline closure appears to be influenced by the timing of closure.

Cleft Palate↗
PubMed1985

The diagnosis of velopharyngeal inadequacy.

At present, there are a number of instrumental devices that can be used to supplement information obtained by the experienced clinician. Although each has its proponents, there continue to be distinct disadvantages associated with all of them. From a clinician's standpoint, the most frustrating limitation is that instruments with demonstrated reliability and validity typically cannot be used comfortably with pre-school children (Table 1). This is extremely unfortunate because those teams wishing to normalize a youngster's velopharyngeal mechanism prior to school enrollment still must rely almost exclusively upon the ear of the clinician for assessment. It is hoped that future research will address this important issue.

Child↗
PubMed1984

Receptors and inhibitory actions of gonadotropin-releasing hormone in the fetal Leydig cell.

The receptors and actions of gonadotropin-releasing hormone (GnRH) were analyzed in cultured testicular cells from 20.5-day fetal rats, in which treatment with luteinizing hormone (LH) maintained Leydig cell steroidogenesis and gonadotropic responses for up to 2 weeks. Testicular GnRH receptors were present on the 5th postnatal day, but were not demonstrable in fetal testes or 2-day cultures thereof. However, GnRH receptors were readily detectable in 4-day cultured fetal testes and were increased by exposure to GnRH agonists. In LH-treated cultures, GnRH sites were reduced by about 50% and did not increase during incubation with GnRH agonists. In such cultures, GnRH agonists inhibited LH-dependent steroid production and abolished the acute testosterone response to human chorionic gonadotropin. The half-maximal inhibitory concentration of [D-Ala6]des-Gly10-GnRH-N-ethylamide (3 X 10(-10)M) was commensurate with its binding affinity for testis receptors (Kd = 1.4 X 10(-10)M). In contrast, GnRH agonists had no inhibitory effects in 2-day cultures prior to the detection of GnRH receptors. The expression of functional GnRH receptors during culture in the absence of gonadotropin and their suppression in LH-treated cultures suggest that pituitary gonadotropins exert a tonic inhibitory effect upon testicular GnRH receptors. The demonstrated inhibitory actions of GnRH on steroidogenesis, with the expression of GnRH receptors in cultured fetal testes and 5-day postnatal testes, indicate that GnRH agonists could influence the actions of gonadotropins upon Leydig cell function in the neonatal testis.

Animals↗
PubMed1984

Alterations in nasal airway resistance following superior repositioning of the maxilla.

Superior repositioning of the maxilla is a contemporary surgical procedure used to correct a variety of dentofacial deformities, including vertical maxillary excess. Concern for the effect of this procedure on nasal respiration is warranted, since superior repositioning of the maxilla may decrease the volume of the nasal cavity. In this study pre- and postoperative nasal-resistance values were obtained for 52 patients who underwent superior repositioning of the maxilla by the LeFort I downfracture procedure. Of these 52 patients, 24 underwent segmental osteotomies and 28 underwent one-piece superior repositioning. Results indicate that the long-faced persons for whom superior repositioning of the maxilla is recommended usually have pretreatment nasal-resistance values within previously reported normal ranges. Superior repositioning of the maxilla, with or without involvement of the nasal floor, usually results in decreased nasal resistance.

Adolescent↗
PubMed1984

A quantitative technique for assessing nasal airway impairment.

The controversy concerning the effects of impaired nasal respiration on dentofacial development stems largely from the lack of a reliable method to assess airway impairment. The purpose of this study was to develop and validate a quantitative technique to estimate nasal airway dimensions so that normal and impaired nasorespiratory function could be defined. The method involves a modification of the theoretical hydraulic principle and utilizes the following equation to estimate cross-sectional area of the nose (NA): NA = V/K [2(delta P)/d] 1/2 (where d = density of air). Pressure drop (delta P) across the nose is measured simultaneously with airflow (V) through the nose during breathing, using appropriate transducers and a PDP 11/34 computer. An analog model of the upper airway was used to determine the discharge coefficient (k) and estimate measurement error. Model studies demonstrate a measurement error of less than 5% for nasal cross-sectional areas of 0.02 to 1.2 cm2. Studies involving eighteen adult subjects and twenty-six children 8 to 11 years of age revealed mean smallest cross-sectional nasal areas of 0.62 cm2 +/- 0.17 and 0.43 cm2 +/- 0.076, respectively. The results indicate that the technique should enable clinicians to (1) estimate size of the airway during breathing, (2) distinguish between normal and impaired nasal respiratory function, and (3) determine quantitatively the effects of surgical and/or orthodontic treatment for improving nasal respiration.

Adolescent↗
PubMed1984

Analysis of simulated upper airway breathing.

There is substantial disagreement among clinicians concerning the etiologic significance of impaired nasal respiration. Conflicting views concerning the effects of breathing on facial growth suggest the need for a more quantitative approach to this important question. This investigation is the first in a series of studies representing a new direction for objectively assessing airway breathing. A model of the upper airway was used to study air movement under controlled conditions. The specific objectives were to determine the effects of airway size and shape on the aerodynamics of simulated breathing and develop a theoretical basis for predicting when breathing mode will change from nasal to predominantly oral. The following theoretical predictions are made on the basis of data generated from the model: A nasal airway cross-sectional area of less than 0.4 cm2 may represent an inadequate airway in adults and some mouth breathing would be expected. The amount of adenoid obstruction must be very large to affect airway resistance. However, if airway resistance in the nose is high, large adenoids would present a serious airway problem and cause predominantly mouth breathing. When nasal airway resistance is high, the mouth will open approximately 0.4 to 0.6 cm2. This shifts a significant amount of air orally and reduces airway resistance to a normal level. If morphologic changes are caused by airway impairment, other factors such as a large tongue, large tonsils, or a long, draping velum are probably significant contributing factors.

Airway Resistance↗