Biomedical subjects

V Hoffstein

Publications and source records attributed to V Hoffstein.

At least 37 records · Page 2Linked to original sources

PubMed1996

Tracheobronchial constriction in asthmatics induced by isocapnic hyperventilation with dry cold air.

Although it is well known that isocapnic hyperventilation (IHV) with dry cold air produces airway constriction in asthmatic subjects, the site of airway narrowing is nuclear. To address this issue, we have quantified the tracheal and bronchial response to IHV with dry cold air in 15 patients with mild asthma and 7 healthy control subjects. We employed the acoustic reflection technique to evaluate changes in airway cross-sectional areas caused by IHV with dry cold air. Airway areas were measured during tidal breathing before and 5 to 10, 30, 60, and 90 min following cold air challenge. For analysis purposes, airway areas were divided into three anatomic segments: extrathoracic tracheal segment, intrathoracic tracheal segment, and main bronchial segment. These segments were assessed at a fixed volume below total lung capacity. Maximal and partial expiratory flow-volume curves were also obtained before each set of area measurements. In normal subjects, IHV with dry cold air caused no significant changes in FEV1, flow at 30% of the vital capacity in the partial curve (V30p), or airway areas. In asthmatics, at 5 to 10 min after challenge, we found that FEV1 decreased by 22 +/- 5% (mean +/- SEM) (p < 0.0001), V30p by 33 +/- 8% (p < 0.003), intrathoracic tracheal area by 10.7% +/- 2% (p < 0.03), and main bronchial area by 14 +/- 3% (p < 0.003). At 30 min, tracheal and main bronchial areas were returned to baseline levels; however, FEV1 and V30p were still significantly decreased, by 13 +/- 3% and 16 +/- 4%, respectively. We conclude that in asthmatics, IHV with dry cold air causes both tracheal and bronchial constriction, and that recovery seems to occur first in the central airways.

Acoustics↗

PubMed1996

Is snoring dangerous to your health?

The purpose of this commentary is to review the evidence linking simple snoring with hypertension and cardiovascular and cerebrovascular disease. This has been a topic of numerous investigations with seemingly divergent results, mainly because of the differences in methodology employed in various studies, such as inclusion of confounding factors, type of population examined, methods of measurements and analysis, etc. Nevertheless, despite these limitations, a review of 19 studies examining the association between snoring and hypertension clearly shows that in the majority of them (14 studies) snoring was not found to be an independent risk factor. An association between snoring and cardiovascular and cerebrovascular disease is somewhat more difficult to assess. Analysis of 15 recent studies dealing with this issue shows that 9 of them concluded that snoring is a risk factor for vascular disease, whereas 6 studies reached the opposite conclusion. However, a detailed review of the studies showing positive association between snoring and vascular disease indicates that in some of them unsuspected sleep apnea may have accounted for this increased risk. In addition, these studies exhibit a number of inconsistencies that raise doubts as to the true validity of association between snoring and vascular disease. Finally, it does not seem biologically plausible that snoring should be a risk factor for cardiovascular and cerebrovascular disease without also being a risk factor for hypertension. Consequently, based on the available information, one cannot conclude that snoring is an independent risk factor for such adverse vascular complications as hypertension and cardiovascular and cerebrovascular disease.

Cardiovascular Diseases↗

PubMed1996

Comparing perceptions and measurements of snoring.

The difficulty in measuring and quantifying snoring using objective criteria is that snoring is first and foremost of a subjective perception by a listener. To test the subjective perception of snoring and to compare it with objective measurements, we studied 25 patients referred to our laboratory because of snoring. All had full nocturnal polysomnography including measurements of snoring. Snoring sounds were recorded on paper and simultaneously stored on audiotape. The technologist scoring the polysomnogram counted the number of snores during a 20-minute segment. Two other technologists, unaware of the objective snoring count, listened to the audiotape and also counted the number of events that they perceived as snores. In 11 of 25 patients there was good agreement (within 25%) between the two listeners and the objective snore count. In another 7 of 25 patients there was good agreement between the listeners, but the objective snore count differed > 25%. In the last group of seven of 25 patients the difference in subjective snore counts perceived by both listeners was > 25%. The agreement between both listeners in judging snoring severity was moderate (weighted Cohen's kappa (w) = 0.49). We conclude that perception of snoring is highly subjective. We speculate that investigations studying consequences and treatment of snoring must employ either more sophisticated properly validated methods to measure snoring or alternatively resort to measurements of the underlying physiological abnormalities responsible for snoring, such as elevations in upper airway resistance.

Adult↗

PubMed1995

Snoring and arousals: a retrospective analysis.

The purpose of this retrospective analysis was to search for possible associations between snoring and arousals. We searched our data base containing more than 2,000 records and selected only patients who 1) had objective measurements of snoring, 2) were not taking sedating medication, 3) did not have sleep apnea (apnea/ hypopnea index < 10) and 4) did not have periodic leg movements (myoclonus index < 5). This procedure left 367 patients available for analysis. We hypothesized that arousals observed in these patients were associated with snoring, and we performed univariate and multivariate regression analysis with arousals as the dependent variable, and age, body mass index, snoring, maximum nocturnal sound intensity and nocturnal oxygen saturation as the independent variables. The results showed that only snoring and mean nocturnal oxygen saturation were significant (p < 0.05) but weak determinants of arousals, accounting for only 7% of their variance. To examine whether snorers have more arousals than non-snorers, we compared a control group of non-snorers (< 50 snores/hour of sleep), with a group of heavy snorers (> 400 snores/hour of sleep). We found that the arousal index was significantly but weakly higher in snorers than non-snorers [mean +/- standard deviation (SD) = 14 +/- 8 vs. 10 +/- 6, p < 0.002]. Conversely, patients within the highest arousal quartile snored significantly more than those within the lowest quartile (snoring index 293 +/- 292 vs. 179 +/- 282, p < 0.008, respectively). We conclude that despite the limitations of this retrospective analysis, there appears to be an association between snoring and arousals, warranting further, properly designed prospective studies.

Adolescent↗

PubMed1995

Diagnosis of obstructive sleep apnea using a portable transducer catheter.

As an initial step in simplifying the diagnosis of sleep apnea with a view toward using portable equipment in the home setting, we examined the efficacy of a portable transducer catheter that measures intrathoracic pressure. This catheter, connected to a miniature data-logger, can be introduced nasally into the airway, and the data so collected can be acquired, stored, and analyzed off-line. We tested this catheter against standard nocturnal polysomnography in 10 patients suffering from obstructive sleep apnea. We found that by using a combination of the raw pressure signal and an envelope pressure signal, we accurately identified apneas and hypopneas, and classified them as obstructive, central, and mixed. For the 10 subjects studied, the polysomnographic apnea/hypopnea index was 34 + 30, versus 32 + 28 obtained by analysis of the pressure tracings. Analysis of 200 respiratory events identified one-by-one from polysomnograms and pressure tracings revealed close correspondence between the two methods. The average duration of apneas was 22.1 + 6.7 s as measured by polysomnography, versus 21.9 + 6.6 s as measured from pressure tracings. Furthermore, there was excellent agreement between the two methods (kappa = 0.89, 95% confidence limits = 0.84 to 0.94). We conclude that our technique for identifying apnea based on measurements of intrathoracic pressure using a thin, portable transducer catheter is a promising method for simplifying the diagnosis of this disorder.

Adult↗

PubMed1995

Acoustic rhinometry in the evaluation of nasal obstruction.

Acoustic rhinometry (AR) is a recently developed objective technique for assessment of geometry of the nasal cavity. The technique is based on the analysis of sound waves reflected from the nasal cavities. It measures cross-sectional areas and nasal volume (NV). To obtain dependable assessments of nasal resistance by rhinomanometry or cross-sectional area measurements by AR, it is essential that the structural relations of the compliant vestibular region remain undisturbed by the measuring apparatus. The use of nozzles in making these measurements carries a great risk of direct distortion of the nasal valve. We used a nasal adapter that does not invade the nasal cavity and a chin support that stabilizes the head. In 51 healthy nasal cavities, the average minimum cross-sectional area (MCA) was 0.62 cm2 at 2.35 cm from the nostril and 0.67 cm2 at 2 cm from the nostril, respectively, before and after topical decongestion of the nasal mucosa. The MCA and NV findings in this group were significantly higher than MCA and NV (P < 0.001) in people with structural or mucosal abnormalities before mucosal decongestion. After mucosal decongestion, the MCA and NV were significantly higher in healthy nasal cavities than in nasal cavities with structural abnormalities (P < 0.001) but were not higher than nasal cavities with mucosal abnormalities (MCA, P = 0.05; NV, P = 0.06). A nozzle was applied in 20 healthy nasal cavities after mucosal decongestion, and a significantly higher MCA was found compared to measurements made with the nasal adapter (P = 0.02). We conclude that the nasal adapter, which does not invade the nasal cavities, avoids the distortion of the nasal valve and gives more accurate results.

Acoustics↗

PubMed1995

Snoring and nocturnal oxygenation. Is there a relationship?

OBJECTIVE: To test the hypothesis that snoring, independently of sleep apnea, is a significant determinant of nocturnal oxygen saturation. DESIGN: Prospective study. SETTING: Sleep disorders clinic, university teaching hospital. PATIENTS: Six hundred twenty-five nonapneic snorers referred to the clinic. METHODS: Nocturnal polysomnography, which included objective and simultaneous measurement of snoring and oxygen saturation, was performed in all patients. Pulmonary function tests and smoking history were also obtained. RESULTS: Multiple stepwise linear regression analysis demonstrated that age, body mass index, and pulmonary function were the most important determinants of nocturnal oxygen saturation, accounting for 20 to 30% of its variability. Snoring was a significant, although weak (partial r2 = 0.073, p < 0.001) determinant of lowest, but not mean, nocturnal oxygen saturation. When mild snorers were matched one-for-one for body mass index to a group of severe snorers, only the lowest, not the mean, nocturnal oxygen saturation was significantly different between the groups. CONCLUSIONS: Snoring is not associated with sustained nocturnal hypoxemia, but it is weakly related to lowest nocturnal oxygen saturation.

Adult↗

PubMed1995

Pharyngeal airflow during sleep.

This study was conducted to investigate the effects of sleep and nasal resistance on pharyngeal airflow in a group of healthy male adults without complaint of habitual snoring. Twelve subjects aged 21 to 60 years were studied in a sleep laboratory during exclusive nasal breathing. Nasal and pharyngeal airflow variables were measured concomitantly at different stages of sleep. Awake pharyngeal resistance averaged 0.02-0.03 Pa/cm3/s in recumbency. In stage 2 sleep and quiet breathing resistance increased by a factor of 3-4 and by a factor of 7-8 during snoring. Increased nasal loading did not increase pharyngeal resistance further or induce snoring. Mostly, increased pharyngeal resistances were of similar magnitude in both phases of respiration, but in a few instances inspiratory resistance exceeded that in expiration, and in a similar number the reverse was found. Overall, compliance of the pharyngeal airway was not a prominent feature in this group of subjects. The relationship between transpharyngeal pressure and resistance should be studied further in order to simplify future studies of airflow during sleep.

Adult↗

PubMed1995

Diagnostic airway pressure recording in sleep apnea syndrome.

A comparison was made between polysomnographic recordings and recordings of airflow pressures in the pharynx and respiratory pressures in the esophagus of 10 adult sleeping subjects with differing degrees of apnea. Pressure measurements were obtained by microsensors mounted on a 7F gauge flexible catheter which sited them in the epi-, meso- and hypopharynx and the esophagus. Digitized overnight pressure data were stored on a PC memory card and subsequently displayed for analysis by means of a notebook computer. In 2 patients examination of 200 obstructive, mixed and central apneic events showed no significant differences in recordings of their incidence, duration of classification between polysomnographic and either pharyngeal or esophageal pressure techniques. Onset of apnea was demonstrated with particular clarity by computer integration of the pressure tracings. The multiple pressure sensor method offered a further important advantage in detecting the caudal limits of pharyngeal obstructions by steep elevation of the pressure gradient in the pharyngeal segment between adjacent sensors in which the caudal limit of the obstruction was sited. The multiple pressure sensor technique provided reliable and comprehensive diagnostic information of breathing disorders in sleeping subjects and together with its miniaturized recording equipment the method commends itself as suitable for home monitoring.

Adult↗

PubMed1994

Blood pressure, snoring, obesity, and nocturnal hypoxaemia.

The association between snoring and blood pressure is still a matter for debate, partly because of uncertainty about the definition of snoring and partly because confounding factors may affect systemic blood pressure such as obesity, sleep apnoea, and nocturnal hypoxaemia. To isolate the contribution of each of these factors, 1415 patients (389 females, 1026 males) referred to a sleep disorders centre were studied. A full history was obtained with particular attention to cardiovascular disease and medications. The patients had nocturnal polysomnography including objective measurement of snoring, and blood pressure was measured in the morning. 18% of non-snores had hypertension as did 20% of heavy snores (not significantly different). Multivariate linear regression analysis showed that snoring was not a significant determinant of blood pressure. Only age, male sex, apnoea/hypopnoea index, and body mass index contributed significantly to the variability of blood pressure. We conclude that snoring in the absence of sleep apnoea is not associated with raised blood pressure.

Adolescent↗

PubMed1994

Snoring: is it in the ear of the beholder?

Complaint of snoring, which is usually voiced by a patient's bedpartner, frequently leads to investigations in the sleep laboratory that are designed to assess snoring objectively and determine whether it is a symptom of sleep apnea. How well this subjective complaint of the listener is confirmed by the objective measurement of snoring is not known. Consequently, we designed a study i) to test the validity of self-perception of snoring and ii) to compare subjective perception of snoring by the sleep technologist with objective measurement of its frequency and loudness. We studied 613 unselected patients referred to our sleep clinic because of snoring and suspicion of sleep apnea. They all had nocturnal polysomnography that included measurements of snoring, expressed as the number of snores per hour of sleep [snoring index (SI)] and mean (dBmean) and maximum (dBmax) nocturnal sound intensity. Following the sleep study, the technologist (and patient) independently rated a patient's snoring as none, mild, moderate or severe. Kruskall-Wallis test, Spearman rank correlations and Cohen's kappa statistics were used to compare the groups, examine the correlations between subjective and objective measurements, and check the agreement between them.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1994

Changes in pulmonary function and cross-sectional area of trachea and bronchi in asthmatics following inhalation of procaterol hydrochloride and ipratropium bromide.

To determine the sites of action of inhaled adrenergic and anticholinergic bronchodilators, we used the acoustic reflection technique to measure airway area before and after administration of beta 2-selective adrenoreceptor agonist (procaterol hydrochloride) and quaternary anticholinergic agent (ipratropium bromide). Eight stable individuals with asthma (five men and three women; mean age, 34 +/- 12.7 yr) were studied on 2 days in single-blind randomized crossover fashion when they self-administered (using metered-dose inhaler) two puffs of either procaterol hydrochloride hemihydrate (10 micrograms/puff) or ipratropium bromide (20 micrograms/puff). Maximal expiratory flow-volume curve, specific airway resistance, and cross-sectional areas of three airway segments (extrathoracic tracheal, intrathoracic tracheal, and bronchial) were recorded at baseline and 15, 30, 60, and 120 min after drug administration. Both agents produced significant improvements in FEV1, FVC and forced expiratory flow at 50% of vital capacity (V50), and specific airway resistance (SRaw) as early as 15 min after drug administration. These effects were sustained for the 120 min monitoring period. However, all improvements were significantly greater for procaterol than for ipratropium. By contrast, there was no significant difference between drugs in the increased production in the cross-sectional areas of the three airway segments although there was a nonsignificant trend toward greater increases in tracheal area produced by the anticholinergic agent.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustics↗

PubMed1994

Predicting nasal continuous positive airway pressure.

We recently proposed an equation predicting the optimal level of continuous positive airway pressure (CPAP) that abolishes sleep apnea from three simple and easily available parameters: body mass index (BMI), neck circumference, and apnea/hypopnea index (AHI). The present study was designed to validate this equation in a prospective group of patients with sleep apnea returning to the sleep laboratory for CPAP titration study. We studied 26 patients and found that the optimal CPAP was equal to the predicted value in 10 of 26 patients, within +/- 1 cm H2O of the predicted value in another 10 of 26 patients, within +/- 2 cm H2O in four of 26 patients, and outside +/- 4 cm H2O in the remaining two patients. We conclude that (1) optimal CPAP can be predicted to within +/- 2 cm H2O from a few simple measurements, and (2) using predicted CPAP as a starting pressure for CPAP titration, it may be possible to optimize and/or shorten the titration study--a fact with significant implications for reducing the cost of "diagnosis-to-treatment" polysomnography.

Anthropometry↗

PubMed1994

Subjective and objective assessment of uvulopalatopharyngoplasty for treatment of snoring and obstructive sleep apnea.

This study was designed to assess the subjective and objective effects of uvulopalatopharyngoplasty (UPPP) for treatment of snoring. We mailed a questionnaire dealing with snoring, quality of sleep, and interference with bed-partner's sleep to 100 unselected patients who were referred because of snoring. Replies were received from 69 patients. The answers were analyzed, and the subjective impressions were compared with preoperative and postoperative objective measurements of snoring and apnea. The average (+/- SD) length of follow-up was 45 +/- 20 mo. We found no significant differences in the apnea/hypopnea index, snoring index, and mean and maximal nocturnal sound intensity before and after surgery in this group. However, despite this lack of objective improvement. 78% of patients reported reduction in snoring, and 79% reported improvement in the quality of sleep; 18 of 69 bed partners no longer complained of interference with their sleep compared with only one preoperatively. We conclude that if the purpose of UPPP is to reduce the reported health hazards associated with snoring, then comparison between objective preoperative and postoperative measurements of snoring does not indicate success; if, on the other hand, the purpose of surgery is to alleviate the social hazard, then UPPP partially achieves this goal.

Adolescent↗

PubMed1994

Sleep and posture.

Computer-assisted open catheter studies of 10 healthy, nose-breathing men in dorsal and in lateral recumbent sleep demonstrated stable intrasubject transpharyngeal differential pressures and airflow resistances. They averaged 19.6 Pa (+/- standard deviation [SD] 11.9) and 0.103 Pa/cm3 per second (+/- SD 0.065) in the dorsal posture and stage II sleep during quiet breathing and were not significantly different in the lateral posture or in stage I sleep. Five subjects were snorers, and their pharyngeal airflow pressures and resistances increased substantially during quiet breathing on assumption of recumbency and much more in sleep. In the 5 subjects who were nonsnorers, postural changes were not significant and sleep increases were moderate. During snoring, transpharyngeal pressures and resistances increased even further, averaging 188 Pa and 1.02 Pa/cm3 per second for the whole group. Transpharyngeal differential pressures and hypopharyngeal transmural pressures frequently exceeded 300 Pa in inspiration and in expiration during periods of snoring. Yet, transpharyngeal differential pressures and resistances did not reveal appreciable differences between phases that would indicate compliant change of pharyngeal cross section. Breathing frequency was unchanged, but ventilation was significantly diminished at elevated upper airway resistances (P < .01). Transpharyngeal resistances and differential pressures varied independently from widely differing nasal resistances. As with our earlier studies, pressure measurements alone clearly demonstrated breathing patterns and events.

Adult↗

PubMed1994

Hemothorax following uncomplicated sclerotherapy for esophageal varices.

Although pleural effusion as a complication of esophageal manipulation is well described in the literature, the fluid is usually nonhemorrhagic. We describe the first patient who had uncomplicated sclerotherapy with ethanolamine for esophageal varices, and on two occasions this patient developed left-sided bloody pleural effusion within 12-72 h after sclerotherapy. The effusion resolved spontaneously within 4 weeks. This case illustrates that hemothorax should be included in the pulmonary complications of sclerotherapy for esophageal varices.

Adult↗

PubMed1994

Cardiac arrhythmias, snoring, and sleep apnea.

We investigated the frequency of cardiac arrhythmias in patients suspected of having sleep apnea, and related them to the severity of apnea, snoring, and nocturnal hypoxemia. We prospectively studied 458 patients who had nocturnal polysomnography which included objective measurement of snoring (quantified by the number of snores per hour of sleep [snoring index (SI)] and maximum nocturnal sound intensity [(dBmax)], as well as examination of the electrocardiogram (modified lead 2). We found 58 percent prevalence of arrhythmias in patients with sleep apnea (apnea/hypopnea index = AHI > 10), vs 42 percent in nonapneic controls (chi 2 = 16.7, p < 0.0001). Patients with arrhythmias had more severe apnea and nocturnal hypoxemia, but not snoring, than patients without arrhythmias. To examine separately the relationship between the prevalence of arrhythmias and snoring, nocturnal oxygenation, and apnea--we selected subgroups of patients "at the opposite ends of the spectrum" with respect to the severity of snoring, hypoxemia, and apnea. We found that 38 percent of light snorers had arrhythmias vs 39 percent of heavy snorers, 82 percent of patients with mean nocturnal oxygen saturation < 90 percent had arrhythmias vs 40 percent of patients with mean nocturnal oxygen saturation > 90 percent (chi 2 = 7.4, p = 0.006), and 70 percent of patients with AHI > or = 40 had arrhythmias vs 42 percent with AHI < or = (chi 2 = 9.2, p = 0.002). We conclude that patients with sleep apnea as a group have higher prevalence of cardiac arrhythmias than nonapneic patients and that snoring alone, without concomitant sleep apnea, is not associated with increased frequency of cardiac arrhythmias.

Adolescent↗

PubMed1994

Hematocrit levels in sleep apnea.

This study addresses the hypothesis that patients with obstructive sleep apnea, who exhibit recurrent episodes of oxygen desaturation at night, have higher hematocrit levels than nonapneic control subjects. We prospectively studied 624 patients referred to the sleep disorders center at St. Michael's Hospital because of suspicion of sleep apnea. All patients had nocturnal polysomnography and measurements of hematocrit level, hemoglobin value, WBC count, and platelet count. Smoking history and awake oxygen saturation (SaO2) was recorded in all of them. Nocturnal oxygenation was assessed using three indices: lowest nocturnal SaO2 (LoSaO2), mean nocturnal SaO2 (MnSaO2) and percent of total sleep time spent at SaO2 lower than 85 percent (TST85%). Patients with TST85% in the lowest quartile (TST85% = 0) had minimally lower hematocrit levels than patients with TST85% in the highest quartile (8 < or = TST85% < or = 90): 0.41 +/- 0.03 vs 0.40 +/- 0.02 in female subjects and 0.45 +/- 0.05 vs 0.43 +/- 0.05 in male subjects, respectively (p < 0.05). Multiple linear regression analysis revealed that MnSaO2, age, and pack-years of smoking were significant predictors of hematocrit level, but they accounted for only 9 percent of the variability in hematocrit level (multiple R2 = 0.087; p < 0.05). We conclude that intermittent nocturnal hypoxemia during episodes of apnea does not lead to clinical polycythemia, but is associated with minor elevations in hematocrit value. These small elevations are unlikely to be useful as markers of hypoxic stress associated with sleep apnea.

Adult↗