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Biomedical subjects

V Hoffstein

Publications and source records attributed to V Hoffstein.

At least 73 records · Page 4Linked to original sources
PubMed1992

Differences in abdominal and neck circumferences in patients with and without obstructive sleep apnoea.

We have recently shown that patients with sleep apnoea have thicker necks than non-apnoeic snoring controls. However, it was not clear whether this difference simply reflects the fact that apnoeic patients are more obese than the non-apnoeic ones, or whether it represents a preferential distribution of fat over the neck region compared to the abnormal region. We therefore measured the neck and abdominal circumferences in a large group of 670 patients suspected of having sleep apnoea, all of whom had full nocturnal polysomnography, including measurement of snoring. We divided these patients into apnoeic and non-apnoeic groups based on the apnoea/hypopnoea index (AHI) of 10. Apnoeic patients had significantly higher body mass index (BMI), neck, and abdominal circumferences than non-apnoeic controls. We then matched apnoeic and non-apnoeic patients exactly, one-for-one for BMI and age; this procedure left us with 156 patients in each group. Abdominal circumferences were similar, but the neck circumference was significantly higher in apnoeic patients (41.2 +/- 3.5 cm vs 39.1 +/- 3.7 cm, p less than 0.0001). Multiple stepwise linear regression analysis revealed that neck circumference and BMI correlated significantly with apnoea (multiple R2 = 0.27, p less than 0.001) and snoring (multiple R2 = 0.19, p less than 0.001). We conclude that obese patients with sleep apnoea have fatter necks than equally obese non-apnoeic snorers, and that the neck circumference could be a significant determinant of apnoea and snoring.

Abdomen↗
PubMed1991

Are history and physical examination a good screening test for sleep apnea?

OBJECTIVE: To determine whether presenting clinical history, pharyngeal examination, and the overall subjective impression of the clinician could serve as a sensitive screening test for sleep apnea. DESIGN: Blinded comparison of history and physical examination with results of nocturnal polysomnography. SETTING: Sleep clinic of a tertiary referral center. PATIENTS: A total of 410 patients referred for suspected sleep apnea syndrome. Most patients reported snoring. MEASUREMENTS: All patients were asked standard questions and given an examination relevant to the diagnosis of the sleep apnea syndrome, and all had full nocturnal polysomnography. Patients with more than ten episodes of apnea or hypopnea per hour of sleep were classified as having sleep apnea. Stepwise linear logistic regression was used to develop two predictive models of sleep apnea: one based on the presence of characteristic clinical features, age, sex, and body mass index; and one based on subjective clinical impression. RESULTS: The prevalence of sleep apnea in our patients was 46%. Only age, body mass index, male sex, and snoring were found to be predictors of sleep apnea. The logistic rule discriminated between patients with and without sleep apnea (receiver operating characteristic [ROC] area, 0.77 [95% Cl, 0.73 to 0.82]). For patients with a predicted probability of apnea of less than 20%, the clinical model had 94% sensitivity and 28% specificity. Subjective impression alone identified correctly only 52% of patients with sleep apnea and had a specificity of 70%. CONCLUSIONS: In patients with a high predicted probability of the sleep apnea syndrome, subjective impression alone or any combination of clinical features cannot serve as a reliable screening test. However, in patients with a low predicted probability of sleep apnea, the model based on clinical data was sufficiently sensitive to permit about a 30% reduction in the number of unnecessary sleep studies.

Adult↗
PubMed1991

Sleep apnea and systemic hypertension: a causal association review.

OBJECTIVE: To critically examine the causal association between sleep apnea syndrome and hypertension. METHODS: A retrospective systematic critique of five epidemiologic studies published in the English literature during 1978 to 1989 identified on Medline and manual literature searches. The evidence was evaluated using the standard observational criteria for causation: strength of association, consistency, dose-response relationship, temporal sequence, specificity, and biologic plausibility. RESULTS: We found evidence to support a causal association between sleep apnea syndrome and hypertension in consistency and specificity and some evidence to suggest a dose-response relationship. Review of the data dealing with the mechanisms important in the pathogenesis of sleep apnea and hypertension allowed us to advance several theories to provide support for biologic plausibility. CONCLUSION: We concluded that there is a positive association--relative risk estimate between 1.3 and 40--for sleep apnea syndrome and hypertension, but the risk association is unstable. Thus, we believe that there is insufficient data to justify doing polysomnography as part of the routine diagnostic work-up for patients with hypertension.

Causality↗
PubMed1991

Evaluation of the upper airway in patients with obstructive sleep apnea.

Multiple methods have been used to study the structure and physiological behavior of the upper airway (UA) in patients with obstructive sleep apnea (OSA). Valuable information may be obtained from the physiologic measurement of pressure and resistance along the UA, as well as from imaging techniques that include: direct or fiberoptic visualization, cephalometric roentgenograms, fluoroscopy, acoustic reflection, computerized tomography, and magnetic resonance imaging. This review summarizes the information that each of these methods has contributed to our understanding of the UA. The results obtained with these different methodologies have generally been complementary with structural narrowing being identified in the majority of patients with OSA. This narrowing is usually focal and located in the velopharyngeal or retropalatal segment of the UA. This is also the predominant site of initial UA collapse. Although obesity with enlargement of soft tissue structures is considered the predominant mechanism leading to UA narrowing, abnormal craniofacial development on a genetic or developmental basis plays an important contributory role.

Airway Obstruction↗
PubMed1991

Snoring and sleep architecture.

The purpose of this study was to examine whether snoring adversely affects sleep architecture and sleep efficiency, and thus may account for the frequent complaints of daytime tiredness and fatigue expressed by heavy snorers. We recruited eight self-confessed heavy snorers and six self-confessed nonsnorers. All subjects had full nocturnal polysomnography, including continuous monitoring of snoring, which was quantified by counting the number of snores per hour of sleep (snoring index), the number of snores per minute of snoring time (snoring frequency), maximal and mean nocturnal sound intensity (dBmax and dBmean, respectively). We found that even the self-confessed nonsnorers snored lightly, with significantly smaller frequency and index than the heavy snorers. Sleep architecture was similar in both groups. Distribution of snoring among the sleep stages differed for light and heavy snorers: light snorers snored uniformly throughout all sleep stages, whereas heavy snorers tended to snore more during slow-wave and REM sleep. Snoring frequency and snoring index were similar during all sleep stages in light snorers, but they were higher during slow-wave sleep in heavy snorers. Wakefulness time after sleep onset and sleep efficiency correlated significantly with the snoring index. We conclude that although snoring does not affect sleep architecture in general, it influences sleep efficiency and wakefulness time after sleep onset; this may have an adverse effect on daytime function of heavy snorers.

Adult↗
PubMed1991

Aggressive cavitary pulmonary sarcoidosis.

Pulmonary sarcoidosis in a young patient is usually a relatively benign disease that either resolves spontaneously or remains quiescent for many years. Very rarely it pursues a more aggressive course leading to progressive lung destruction. We report a young patient who presented with Stage III sarcoidosis and over a period of 4 yr progressed to severe cavitary disease with frequent superinfections leading to bronchiectasis and chronic suppuration of the lung, eventually requiring a pneumonectomy.

Adult↗
PubMed1991

Pharyngeal function and snoring characteristics in apneic and nonapneic snorers.

Abnormalities in pharyngeal function, manifested even when the patients are awake, are thought to play an important role in the pathogenesis of sleep apnea. Tests of awake pharyngeal function continue to stimulate interest because it is hoped that they may allow physicians to distinguish patients with sleep apnea from those without it, and therefore reduce the number of unnecessary sleep studies. We elected to study two measures of pharyngeal function: changes in pharyngeal area with lung volume (PLVD) and changes in pharyngeal area in response to externally applied positive pressure, i.e., pharyngeal distensibility (Cph). Both measurements have been employed for assessment of pharyngeal function, and both are thought to reflect pharyngeal "floppiness." Measurement of PLVD is technically very simple, whereas the measurement of Cph is technically more complex. If the two measurements are highly correlated, it might be possible to replace the technically more difficult one by the simpler one. Consequently, the purpose of this study was two-fold: first, to examine the relationship between pharyngeal distensibility and lung volume dependence of pharyngeal area, and second, to compare these parameters in a large group of confirmed snorers with and without obstructive sleep apnea (OSA). We studied 75 unselected patients referred for the investigation of snoring and suspected sleep apnea. All patients had nocturnal polysomnography, pulmonary function tests, and measurement of pharyngeal areas at TLC, FRC, and residual volume (RV) employing the acoustic reflection technique. The area measurement at FRC was performed at zero and at 4.1 cm H2O positive airway pressure to calculate pharyngeal distensibility.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Site of airway obstruction in patients with obstructive sleep apnea before and after uvulopalatopharyngoplasty.

This study describes a simple method, based on a movable catheter technique, for use during routine polysomnography to identify the site of obstruction, and this has been applied to 51 patients with suspected sleep apnea. The obstruction was found to be retropalatal in 30, retrolingual in 7, and could not be determined in 14 patients (12 had no sleep apnea, 1 did not sleep, and 1 had central sleep apnea). Twelve of these patients had uvulopalatopharyngoplasty with preoperative and postoperative polysomnograms to determine the site of obstruction. The preoperative obstruction was retropalatal in nine and retrolingual in three. Postoperatively, four patients (one with retrolingual obstruction and three with retropalatal obstruction) no longer had sleep apnea. In the remaining eight patients, the site of obstruction was unchanged from the preoperative one. Several conclusions result: 1. the movable catheter technique offers a simple way to determine the site of obstruction in patients with significant obstructive sleep apnea, 2. most such patients obstruct in the retropalatal region, and 3. preoperative localization of the site of obstruction to the retropalatal region does not seem to improve the surgical outcome of uvulopalatopharyngoplasty.

Adult↗
PubMed1991

Roentgenographic dimensions of the upper airway in snoring patients with and without obstructive sleep apnea.

The purpose of this study was to examine whether a simple test, such as routine roentgenographic views of the upper airway, is useful in identifying anatomic narrowing of the airway in patients with sleep apnea. To accomplish this, we prospectively studied a group of 117 patients (95 male and 22 female subjects) referred for evaluation of heavy snoring and possible obstructive sleep apnea. All patients had full nocturnal polysomnography, including measurements of snoring. Lateral view of the airway obtained after swallowing contrast material was used to measure pharyngeal diameters at three sites along the airway. All measurements were performed with the patients standing and supine. We used three different definitions of sleep apnea (apnea/hypopnea index of 10, 20, and 40), and compared airway diameters between the apneic and nonapneic snorers. Only when sleep apnea was defined as greater than 40 apneas plus hypopneas per hour of sleep was there a significant difference in airway diameter at the tip of the palate and 1 cm distal to it between apneic and nonapneic snorers. Both groups of patients demonstrated a significant reduction in the retropalatal distance on assumption of the supine posture. Stepwise, forward, multiple linear regression analysis showed that the retropalatal distance and airway diameter at the tip of the palate and 1 cm distal to it were significant predictors of snoring, but not apnea. We conclude that (1) airway diameters account for some of the variability in snoring, and (2) they do not differentiate between apneic and nonapneic snorers.

Adult↗
PubMed1991

The acoustic reflection technique for non-invasive assessment of upper airway area.

Non-invasive assessment of upper airway area by acoustic reflections has been developed in the last 12 yrs. The technique is based on the analysis of sound waves reflected from the airways. Measurement of the amplitudes of the reflections and their times of arrival at the sensing microphone permits construction of a plot of airway area vs distance from the microphone. We describe the theoretical foundations of the method and review the underlying assumptions. This is followed by a summary of the results of in vitro and in vivo validation studies, with particular attention to the reproducibility, accuracy and variability of the technique. The description of clinical and physiological applications of this technique includes detection of tracheal stenosis, demonstration of structural and functional abnormalities of the pharynx and glottis in patients with sleep apnoea, dichotomous response of the airway area to exercise, and airway vs parenchymal hysteresis. Finally, we comment on the future directions that might be investigated using this technique.

Acoustics↗
PubMed1991

Resolution of obstructive sleep apnea following facial surgery.

Compared to uvulopalatopharyngoplasty (UPPP), maxillo-facial surgery is rarely performed in Canada for treatment of obstructive sleep apnea. However, in patients with retrolingual obstruction, UPPP cannot be expected to result in good surgical outcome. We describe a patient with retrognathia causing airway obstruction at the base of the tongue, in whom sagittal mandibular osteotomy with hyoid bone advancement resulted in resolution of snoring and sleep apnea.

Adult↗
PubMed1991

Snoring, apnea and nasal resistance in men and women.

To examine if gender and airway resistance (nasal and pulmonary) influence the loudness and intensity of snoring, we prospectively studied 370 unselected patients referred to our sleep clinic because of heavy snoring and a possibility of sleep apnea. All patients had full nocturnal polysomnography, including measurements of snoring using a calibrated microphone-sound meter system, and determination of pulmonary (Raw) and nasal resistance (Rna). Snoring was quantified by reporting the number of snores per hour of sleep (snoring index--SI) and the maximum nocturnal sound intensity (dBmax). The patient population comprised 77 females and 293 males, ranging in age from 12 to 80 years. Based on the apnea/hypopnea index (AHI) we separated all patients into the apneic and non-apneic groups. There were 201 non-apneic snorers (AHI less than or equal to 10) and 160 apneic snorers (AHI greater than 10). There was no significant difference in snoring frequency, maximum nocturnal sound intensity, nasal and pulmonary resistance between men and women or between apneic and non-apneic snorers. Stepwise, forward, multiple linear regression analysis showed that body mass index and nasal resistance correlate significantly with the snoring index (R2 = 0.29, p less than 0.005), while age and body mass index correlate only weakly, but significantly, with the maximum nocturnal sound intensity. We conclude that (1) men snore similarly to women, and (2) obesity and nasal resistance are important determinants of the frequency of snoring. It follows that measures taken to reduce weight and decrease nasal resistance may be of benefit in reducing snoring.

Adolescent↗
PubMed1990

Airflow limitation in morbidly obese, nonsmoking men.

STUDY OBJECTIVE: To determine the effect of obesity on pulmonary function. DESIGN: Case-control study, using nonobese, age- and height-matched [corrected] nonsmokers. SETTING: Metabolic and obesity clinics of two major teaching hospitals. PATIENTS: One hundred and three obese, lifelong nonsmokers without cardiopulmonary disease. CONTROLS: One hundred and ninety healthy, nonobese nonsmokers recruited from among hospital personnel. MEASUREMENTS AND MAIN RESULTS: Complete pulmonary function measurements in all patients and controls. These measurements included maximum expiratory flow-volume curve, lung volumes and airway resistance using body plethysmograph, single-breath diffusing capacity for carbon monoxide, and total lung capacity using the helium dilution technique. Obese persons were found to have lower functional residual capacity, expiratory reserve volume, and total lung capacity by helium dilution than nonobese controls. In addition, residual volume and diffusing capacity were higher in the obese group. Finally, we found that obese men, but not women, had reduced maximum expiratory flow rates at 50% and 75% of exhaled vital capacity. CONCLUSION: Obesity may contribute independently of smoking habits to chronic airflow limitation in men.

Adult↗
PubMed1990

Do patients with obstructive sleep apnea have thick necks?

During physical examination of patients with suspected obstructive sleep apnea (OSA), a comment is frequently made that they appear to have a short and fat neck. To confirm this subjective impression by objective measurements, we studied a group of 123 patients referred to us because of snoring and suspected OSA, all of whom had nocturnal polysomnography and measurements of external and internal neck circumference. The external neck circumference was measured at the level of the superior border of the cricothyroid cartilage. Internal neck circumferences were calculated from the measurements of pharyngeal, glottic, and tracheal areas obtained by the acoustic reflection technique. Internal pharyngeal circumference was further subdivided into the proximal, middle, and distal thirds. The acoustic technique also permitted us to measure the distance between the teeth and the glottic minimum, which reflects the length of the upper airway. Stepwise multiple linear regression analysis revealed that the apnea/hypopnea index (AHI) correlated only with the external neck circumference, the body mass index, and the internal circumference of the distal pharynx; these three variables accounted for 39% of the variability in AHI. We conclude that the external and internal neck circumferences and the degree of obesity are important predictors of sleep apnea; it is possible that obesity produces its effect via fat in the neck. We speculate that the static pharyngeal size modulated by the dynamic loading of the airway due to the weight of fatty tissue of the neck may contribute to the pathogenesis of OSA.

Adult↗
PubMed1990

An evaluation of flow-volume curves as a screening test for obstructive sleep apnea.

We examined flow-volume curves for their potential as screening tests for obstructive sleep apnea (OSA) in 401 patients referred for investigation of snoring. In all patients, we performed nocturnal polysomnography, maximum inspiratory and maximum expiratory flow-volume curves. The curves were examined for two features: 1) presence of flow oscillations (the "saw-tooth" sign), and 2) changes in their configuration that might suggest upper airway obstruction as documented by the expiratory/inspiratory flow ratios calculated at 50 and 75 percent of exhaled vital capacity (FR50 and FR25, respectively). Based on the results of nocturnal polysomnography, the patients were stratified according to severity into apnea groups, and the flow ratios and flow oscillations were compared among these groups. We found that neither the FR50 nor FR25 were significantly different among the groups. Inspiratory and expiratory flow oscillations were seen infrequently (32 patients) and tended to occur in patients with more severe sleep apnea. Neither the flow ratios nor the flow oscillations had good predictive values for snoring or sleep apnea. The sensitivity of the flow volume curve abnormalities ranged between 0 and 14 percent, but the specificity was high, ranging between 93 and 95 percent. We conclude that because of low sensitivity, flow-volume loops are not a useful screening test for the diagnosis of OSA in snoring patients.

Adult↗