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Biomedical subjects

C F Ryan

Publications and source records attributed to C F Ryan.

At least 37 records · Page 2Linked to original sources
PubMed1996

Mechanical properties of the velopharynx in obese patients with obstructive sleep apnea.

Epidemiologic data indicate that the relationship between obesity and obstructive sleep apnea (OSA) is largely explained by variation in neck size. Fat deposits in the neck may predispose to upper airway (UA) occlusion during sleep by altering the mechanical properties of the UA, particularly at the level of the velopharynx (VP). To determine whether effective compliance (CEFF) of the VP is related to obesity in the neck, we have performed anthropometrics, polysomnography, and dynamic UA videoendoscopy in 18 patients with OSA and eight nonapneic control subjects. Following topical anesthesia (cocaine 4%) to one nasal passage, subjects were examined with a thin fiberscope (outer diameter [OD] 3.8 mm) while awake, supine, breathing exclusively through the nose, during a maximal vital capacity (VC) maneuver against an unoccluded airway. UA cross-sectional area (CSA), anteroposterior (AP) and lateral (L) diameters were measured from stored images. CEFF was expressed as the ratio of CSAVP in expiration (E) to inspiration (I) during the maximal VC maneuver (expiratory CSAMAX/inspiratory CSAMIN), and airway shape as AP/L diameter. The OSA patients were divided into two groups based on median neck circumference (NC). CEFF of the VP was greater in OSA patients compared with control subjects (CEFF 2.0 +/- 0.8 versus 1.1 +/- 0.5; p < 0.001). CEFF was greater in the large NC group compared with both the small NC group (p < 0.05) and control subjects (p < 0.01), but the difference between the small NC group and control subjects was not significant. CEFF was related to NC (r = 0.63; p = 0.001; n = 26), body mass index (r = 0.54; p < 0.01, n = 26), and apnea-hypopnea index (r = 0.43; p < 0.05; n = 23). The change in CSAVP during the maximal VC maneuver was mainly due to inspiratory narrowing. Obese patients with large necks have a more collapsible velopharynx during wakefulness, which may predispose to upper airway obstruction during sleep.

Adult↗
PubMed1995

Cephalometric and computed tomographic predictors of obstructive sleep apnea severity.

The interaction between craniofacial structure assessed by lateral cephalometry, and tongue, soft palate, and upper airway size determined from computed tomography (CT) scans was examined in 25 control subjects and 80 patients with obstructive sleep apnea (OSA). On the basis of the cephalometric analyses, the patients with OSA had retruded mandibles with larger ANB angle differences, elongated maxillary and mandibular incisors and mandibular molars, and high total upper and lower face heights The computed tomographic evaluations revealed that patients with OSA also had larger tongue, soft palate, and upper airway volumes. Men with OSA and skeletal Class I malocclusions had significantly larger soft palates than comparable controls. Both tongue and soft palate volumes were positively correlated with body mass index. A principal component analysis reduced the database, and one significant correlation was identified. Subjects with high total, upper and lower face heights, elongated maxillary and mandibular teeth, and proclined lower incisors were observed to have large tongue, soft palate, and upper airway volumes, to have a higher apnea index and to be obese. Linear regression analysis indicated that a high apnea index was seen in association with large tongue and soft palate volumes, a retrognathic mandible, an anteroposterior discrepancy between the maxilla and mandible, an open bite tendency between the incisors, and obesity.

Adult↗
PubMed1995

Energy expenditure in obstructive sleep apnea.

Patients with obstructive sleep apnea (OSA) are often obese and, in common with obese patients generally, find it difficult to lose weight. Obstructive sleep apnea may be associated with changes in total daily energy expenditure that could contribute to obesity and complicate its management. To determine whether resting metabolic rate and the thermogenic effect of food are reduced in OSA, we have compared postabsorptive resting energy expenditure (REE) and dietary thermogenesis (DT) in 14 patients with moderate to severe symptomatic OSA and 14 control subjects matched for obesity. Anthropometrics, body composition analysis using bioelectrical impedance and indirect calorimetry using a metabolic cart and canopy system were performed in all subjects. Dietary thermogenesis after a liquid meal equivalent to 35% of REE was measured in 13 patients and 8 control subjects. Measurements were repeated after chronic (mean +/- SD 12 +/- 5 weeks) nasal continuous positive airway pressure (CPAP) therapy in 10 patients with OSA. Energy expenditure was expressed in terms of metabolic body size. The patients with OSA were heavier and had larger necks and a larger lean body mass (LBM) than controls, but the two groups were well matched for body mass index (BMI) and percent body fat. REE was greater in OSA patients than controls, but when corrected for LBM there was no difference between the two groups (27 +/- 3 vs. 28 +/- 4 kcal/kg). DT was similar in patients and controls (17 +/- 6 vs. 15 +/- 10%). REE/LBM was quite consistent among patients with OSA, regardless of body weight. REE and DT did not change following chronic nasal CPAP therapy. (ABSTRACT TRUNCATED AT 250 WORDS)

Anthropometry↗
PubMed1995

Ventilatory muscle strength and endurance in myasthenia gravis.

Patients with generalized myasthenia gravis (MG) often have associated ventilatory muscle involvement. It is not known whether patients with isolated ocular muscle involvement have identifiable involvement of their ventilatory muscles. Most studies have assessed muscle involvement by measuring muscle strength; however, we hypothesized that measures of ventilatory muscle endurance may be more sensitive tests of ventilatory muscle involvement in myasthenia gravis. We studied 17 patients with myasthenia gravis (four with ocular involvement alone and 13 with varying degrees of generalized myasthenia gravis). Spirometry, ventilatory muscle strength (maximum inspiratory and expiratory pressures (MIP and MEP)) and endurance (2 min incremental threshold loading test) were measured before and 20 min after i.m. neostigmine. We compared the results with those of 10 normal controls. We found no difference between patients with isolated ocular involvement and controls. Ocular myasthenia gravis patients did not improve after neostigmine. The patients with generalized myasthenia gravis had reduced baseline ventilatory muscle strength (MIP 67 cmH2O (70% of predicted), MEP 86 cmH2O (50% of pred) and endurance (mean maximal load achieved = 246 g, mean pressure at highest load (P) = 19.4 cmH2O) compared with controls. After neostigmine, there was a significant increase in MIP in patients with generalized myasthenia gravis and a trend towards an increased MEP. As a group, the patients with generalized myasthenia gravis did not demonstrate a change in their ventilatory muscle endurance after neostigmine; however, there was considerable interpatient variability in response. We conclude that patients with isolated ocular MG have normal ventilatory muscle strength when tested conventionally.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

The relationship between obesity and craniofacial structure in obstructive sleep apnea.

STUDY OBJECTIVE: To evaluate the interaction between craniofacial structure and obesity in male patients with obstructive sleep apnea (OSA). DESIGN: Retrospective analysis of a cohort of OSA patients. The relationships between neck circumference (NC), body mass index, apnea severity, and craniofacial and upper airway soft-tissue measurements from upright lateral cephalometry were examined. Patients were divided into groups; small to normal NC (group A), intermediate NC (group B), or large NC (group C). SETTING: A university teaching hospital and tertiary sleep referral center. PATIENTS: A consecutive series of patients with OSA who underwent polysomnography and lateral cephalometry. MEASUREMENTS AND RESULTS: Group A patients were less obese and had more craniofacial abnormalities such as a smaller mandible and maxilla and a more retrognathic mandible. Group B patients had both upper airway soft-tissue and craniofacial abnormalities. Group C patients were more obese with larger tongues and soft palates, and an inferiorly placed hyoid. Group C patients also had fewer craniofacial abnormalities than group A or B patients. There was no difference in airway size among the three groups. CONCLUSIONS: We conclude that there is a spectrum of upper airway soft-tissue and craniofacial abnormalities among OSA patients: obese patients with increased upper airway soft-tissue structures, nonobese patients with abnormal craniofacial structure, and an intermediate group of patients with abnormalities in both craniofacial structure and upper airway soft-tissue structures.

Adult↗
PubMed1994

Long-term survival of patients with obstructive sleep apnea treated by uvulopalatopharyngoplasty or nasal CPAP.

Patients with obstructive sleep apnea (OSA) have decreased long-term survival. Treatment of OSA with either nasal continuous positive airway pressure (CPAP) or tracheostomy improves survival, but the effect of uvulopalatopharyngoplasty (UPPP) on survival is unclear. We attempted to contact all patients with OSA treated with either UPPP or nasal CPAP over a 6-year period to compare long-term survival between these two treatments. One hundred fifty-four patients had a UPPP during this period. Five of these patients were later treated with nasal CPAP and were excluded from the analysis. Twelve of the remaining 149 were unavailable for follow-up but were included in the analysis. Follow-up polysomnography was performed on 140 (94 percent) of these patients; 114 (81 percent) had either a postoperative apnea index < 5/h or > 50 percent reduction in apnea index. Two hundred eight patients were started on a regimen of nasal CPAP during the same period. Eighty-two patients discontinued nasal CPAP therapy and were excluded from analysis. Nine of the remaining 126 were unavailable for follow-up but were included in the analysis. Six patients treated with UPPP died. Three of these six patients had a 3-month follow-up polysomnogram that revealed apnea indices of 1/h, 5/h, and 23/h. Three patients treated with nasal CPAP died. There was no difference in the long-term survival between the two treatment groups. We conclude that there may be no difference in the long-term survival of patients with OSA between those treated with UPPP and those treated with nasal CPAP. This study emphasizes the importance of follow-up polysomnography in all patients after UPPP.

Adult↗
PubMed1993

Genioglossus muscle activity and inspiratory timing in obstructive sleep apnea.

Atypical tongue muscle activity during sleep may contribute to the development of obstructive sleep apnea (OSA). Inspiratory genioglossus (GG) muscle activity was investigated in 10 OSA adults and 4 symptom-free controls. On the basis of overnight monitoring during nonREM sleep, the duration of the inspiratory GG activity and the total GG activity cycle is shorter in patients with OSA. The duration of inspiration and the duration of one total respiratory cycle is also shorter in patients with OSA. The commencement time lag between inspiratory GG activity and the onset of inspiration is shorter in patients with OSA during nonapneic breathing which indicates that inspiratory GG activity is activated relatively later in these patients. Furthermore, the inspiratory GG activity occurs after inspiration during an apnea, but the timing of GG activity onset progressively advances during the apnea. Earlier GG reactivation occurs before inspiration during the first nonoccluded breath at the end of an apnea. During subsequent tidal breathing, the timing of the GG onset progressively decreases after the onset of inspiration until the next obstructive apnea occurs. This observation suggests that the timing relationship between GG inspiratory activity and inspiratory effort is of physiologic importance in the pathogenesis of OSA. Furthermore, it may explain why dental appliances, such as the tongue retaining device, are highly effective in the resolution of OSA in selected patients.

Adult↗
PubMed1993

The predictive accuracy of home oximetry in patients with suspected obstructive sleep apnea.

To evaluate the predictive accuracy of home oximetry, we have performed a questionnaire, physical examination and home oximetry on 96 patients with suspected obstructive sleep apnea (OSA) within 2 weeks of laboratory polysomnography. We have developed a predictive equation that includes questionnaire, anthropometric and home oximetry data to diagnose OSA. We could confidently diagnose OSA in 20% of patients and exclude OSA in 5% of patients based on this prediction model and the population distribution.

Adult↗
PubMed1993

Energy balance in stable malnourished patients with chronic obstructive pulmonary disease.

We have measured caloric intake, energy expenditure, and the thermogenic effect of food in ten patients with stable COPD who had a history of involuntary weight loss over several years and were malnourished (< 85 percent ideal body weight). Each patient completed a 7-day food record. Indirect calorimetry was performed in the resting postabsorptive state. After placement of a nasoenteric tube, patients were randomly assigned to be refed or sham-fed (mean +/- SD, 16 +/- 3 days), following which, metabolic measurements were repeated. Indirect calorimetry was also performed before and after a large meal in each patient. Home caloric intake was 135 +/- 23 percent of resting energy expenditure. Resting energy expenditure was 94 +/- 16 percent of that predicted by the Harris-Benedict equation and did not change significantly during inpatient refeeding. Refeeding resulted in weight gain (2.4 +/- 1.9 kg, p < 0.02). A large meal caused substantial increases in energy expenditure (24 +/- 18 percent), carbon dioxide production (39 +/- 18 percent), and oxygen consumption (23 +/- 16 percent). We conclude that stable malnourished COPD patients consume adequate calories to meet average energy requirements and are not hypermetabolic. Inpatient refeeding by nocturnal nasoenteric infusion is well tolerated and results in weight gain, but the thermogenic effect of a large meal poses a considerable metabolic and ventilatory load that could precipitate acute respiratory failure.

Aged↗
PubMed1992

Ventilatory dysfunction in severe anorexia nervosa.

A 25-year-old woman suffering from chronic anorexia nervosa lost more than 50 percent of her body weight and presented with generalized muscle weakness. Pulmonary function tests showed a severe restrictive defect, and she had marked impairment of respiratory muscle strength and endurance, peripheral muscle function, and hypercapnic ventilatory responses, all of which improved following refeeding. The interaction and response to treatment of these effects on respiratory function are discussed.

Adult↗
PubMed1991

Three-dimensional upper airway computed tomography in obstructive sleep apnea. A prospective study in patients treated by uvulopalatopharyngoplasty.

The success of uvulopalatopharyngoplasty in treating obstructive sleep apnea varies considerably. Some of this variability may be accounted for by differences in the site of upper airway narrowing. To determine whether preoperative awake upper airway and soft tissue volumes predict the response to uvulopalatopharyngoplasty, preoperative awake computed tomograms (CT) of the upper airway were performed on 60 consecutive patients with symptomatic obstructive sleep apnea. Tracings were made from the CT scans of upper airway, tongue, and soft palate. Computer software was used to determine the cross-sectional area and volume of the upper airway, tongue, and soft palate. Patients underwent overnight polysomnograms before and 3 months after uvulopalatopharyngoplasty. Tongue volume was larger (p less than 0.02) and both upper airway to tongue volume (p less than 0.0005) and oropharynx to soft palate volume ratios (p less than 0.01) were smaller in obese patients. A good response to uvulopalatopharyngoplasty as defined by a postoperative apnea index of less than 5 apneas/h or a reduction in apnea index greater than or equal to 50% was seen in 50 patients (83%). Patients who had a good response had a smaller oropharyngeal cross-sectional area (p less than 0.01), a smaller upper airway volume (p less than 0.05), a smaller upper airway to tongue volume ratio (p less than 0.01), and a smaller oropharynx to soft palate volume ratio (p less than 0.05). Obese patients with obstructive sleep apnea have larger tongues and smaller upper airways relative to tongue and soft palate size. Patients with smaller upper airways, particularly relative to tongue and soft palate size, have a good response to uvulopalatopharyngoplasty.

Computer Graphics↗
PubMed1991

Magnetic resonance imaging of the upper airway in obstructive sleep apnea before and after chronic nasal continuous positive airway pressure therapy.

Magnetic resonance imaging (MRI) provides high-resolution images of the upper airway and is useful for assessing conditions associated with increased tissue water content. To determine whether nasal continuous positive airway pressure (CPAP) changes awake upper airway morphology in obstructive sleep apnea (OSA), we performed awake upper airway MRI scans on five male patients with moderate to severe OSA before and after 4 to 6 wk of nasal CPAP therapy. MRI scans were performed using spin echo pulse sequences to examine detailed anatomy and inversion recovery sequences to assess mucosal water content. Patients did not have nasal CPAP applied during the MRI scans. Axial and sagittal images were obtained, and tracings were made of the upper airway, tongue, and soft palate. Utilizing computer graphics, cross-sectional areas and volumes were calculated for each anatomic structure. A subjective grading system was used to assess upper airway mucosal water content. Pharyngeal volume and minimum pharyngeal cross-sectional area increased (p less than 0.05) and tongue volume decreased (p less than 0.01) following chronic nasal CPAP therapy. The increase in pharyngeal volume occurred mainly in the oropharynx (p less than 0.01). Upper airway mucosal water content decreased in the oropharynx (p less than 0.05). We conclude that chronic nasal CPAP therapy during sleep in patients with OSA produces changes in awake upper airway morphology. These changes may be due to resolution of upper airway edema. The upper airway of patients with OSA can be accurately and repeatedly assessed using MRI.

Adult↗
PubMed1990

The effects of refeeding on peripheral and respiratory muscle function in malnourished chronic obstructive pulmonary disease patients.

We carried out a prospective randomized controlled trial to investigate the effects of short-term refeeding (16 days) in 10 malnourished inpatients with chronic obstructive pulmonary disease (COPD). Six patients were randomized to receive sufficient nasoenterically administered calories to provide a total caloric intake equal to 1,000 kcal above their usual intake. The other four patients were sham fed, receiving only 100 kcal more. Measurements of nutritional status, respiratory muscle strength and endurance, adductor pollicis function, and pulmonary function were performed initially and at study end. The refed group gained significantly more weight and showed significant increases in maximal expiratory pressure and mean sustained inspiratory pressure. There were no significant changes in the maximal inspiratory pressure or in adductor pollicis function. In malnourished inpatients with COPD, short-term refeeding leads to improvement in respiratory muscle endurance and in some parameters of respiratory muscle strength in the absence of demonstrable changes in peripheral muscle function.

Aged↗
PubMed1990

Nasal continuous positive airway pressure (CPAP) therapy for obstructive sleep apnea in Hallermann-Streiff syndrome.

An 8-year-old girl with Hallermann-Streiff syndrome (oculomandibulofacial syndrome) was examined. She had a history of severe snoring, reported nocturnal apnea, excessive daytime hypersomnolence, nocturnal enuresis, and failure to thrive. Overnight polysomnography confirmed severe obstructive sleep apnea. Long-term nasal continuous positive airway pressure (CPAP) therapy completely relieved the obstructive sleep apnea and was associated with improved weight gain and growth.

Child↗
PubMed1990

Upper airway measurements predict response to uvulopalatopharyngoplasty in obstructive sleep apnea.

Although uvulopalatopharyngoplasty relieves obstructive sleep apnea in the majority of patients, the factors that determine a successful response are not well defined. To determine whether preoperative awake upper airway measurements predict the response to uvulopalatopharyngoplasty, presurgical lateral cephalometric radiographs were evaluated on 60 consecutive patients with symptomatic obstructive sleep apnea. Patients underwent overnight polysomnograms before uvulopalatopharyngoplasty and 3 months afterwards. Forty-eight (80%) patients had a good response as defined by a postoperative apnea index of less than or equal to 4 apneas/hour or a reduction in apnea index of greater than or equal to 60%. Responders had a significantly narrower inferior airway space (P less than .0005) and a smaller ratio of inferior airway space to tongue length (P less than .001). Improvement in apnea severity following uvulopalatopharyngoplasty was related to the degree of airway narrowing (r = 0.36; P less than .01). This study shows that upper airway measurements help predict response to uvulopalatopharyngoplasty in patients with obstructive sleep apnea. Patients with a narrow airway, particularly relative to tongue size, have good responses to uvulopalatopharyngoplasty.

Adolescent↗
PubMed1988

Relative and absolute bioavailability of prednisone and prednisolone after separate oral and intravenous doses.

A randomized, four-way cross-over study was conducted in eight healthy male volunteers to determine the relative and absolute bioavailability of prednisone (PN) and prednisolone (PL). PN and PL were administered as single, oral 10-mg tablet doses and as 10-mg zero-order 0.5-hour intravenous infusions. Comparable mean PN and PL maximum plasma concentrations (Cmax), times for Cmax, areas under the plasma concentration-time curves (AUC), and apparent elimination rate constants between tablet treatments demonstrated that PN and PL tablets were bioequivalent. Absolute bioavailability (F) determinations based on plasma PL concentrations were independent of which IV treatment was used as reference and indicated complete systemic availability of PL from both PN and PL tablets. However, F based on plasma PN data was contradictory. Using IV PN as reference, approximately 70% systemic availability was observed from both tablets, whereas using IV PL as reference, systemic availability was greater than unity. PN and PL are model compounds that exemplify the difficulties involved in accurately determining the relative and absolute bioavailability of substances that undergo reversible metabolism.

Administration, Oral↗