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Biomedical subjects

V Hoffstein

Publications and source records attributed to V Hoffstein.

At least 127 records · Page 7Linked to original sources
PubMed1986

Changes in tracheal cross-sectional area during Mueller and Valsalva maneuvers in humans.

Pressure-area behavior of the excised trachea is well documented, but little is known of tracheal compliance in vivo. Extratracheal tissue pressures are not directly measurable, but transmural pressure for the intrathoracic trachea is inferred from intra-airway and pleural pressure differences. Extramural pressure of the cervical trachea is assumed to be atmospheric. The difference in transmural pressure between the intra- and extrathoracic tracheal segments should be exaggerated during Mueller and Valsalva maneuvers. We used the acoustic reflection technique to measure tracheal areas above and below the thoracic inlet during these isovolume-pressure maneuvers. We found that 10 cmH2O positive pressure increased tracheal area in the extrathoracic segment by 34 +/- 16% (mean +/- SD) and in the intrathoracic segment by 35 +/- 15%. There was a reduction in area of 27 +/- 16 and 24 +/- 14%, respectively, for the extra- and intrathoracic segments with 10 cmH2O negative pressure. We conclude that the effective transmural pressure gradients do not vary significantly between intra- and extrathoracic tracheal segments.

Adult↗
PubMed1986

Pharyngeal cross-sectional area in normal men and women.

Pharyngeal size and the dynamic behavior of the upper airway may be important factors in modulating respiratory airflow. Patients with obstructive sleep apnea are known to have reduced pharyngeal cross-sectional area. However, no systematic measurements of pharyngeal area in healthy asymptomatic subjects are available, in part due to the lack of simple, rapid, and noninvasive measurement techniques. We utilized the acoustic reflection technique to measure pharyngeal cross-sectional area in 24 healthy volunteers (14 males, 10 females). Pharyngeal area was measured during a continuous slow expiration from total lung capacity (TLC) to residual volume (RV). We compared pharyngeal cross-sectional areas in males and females at three lung volumes: TLC, 50% of vital capacity (VC), and RV. In males, pharyngeal areas (means +/- SD) were 6.4 +/- 1.3 cm2 at TLC, 5.4 +/- 0.9 cm2 at 50% VC, and 4.1 +/- 0.8 cm2 at RV. In females, pharyngeal areas were 4.8 +/- 0.6 cm2 at TLC, 4.2 +/- 0.5 cm2 at 50% VC, and 3.7 +/- 0.6 cm2 at RV. The difference in area between males and females was statistically significant at TLC and 50% VC but not at RV. However, when the pharyngeal cross-sectional area was normalized for body surface area, this difference was not significant. In males there was a negative correlation of pharyngeal area with age. We conclude that sex differences in pharyngeal area are related to body size, pharyngeal area shows a similar variation with lung volumes in males and females, and in males pharyngeal area reduces with age.

Adult↗
PubMed1986

Sarcoidosis simulating pulmonary veno-occlusive disease.

We describe a young woman who presented with a 6-month history of progressive pulmonary hypertension. At autopsy she was found to have noncaseating granulomas obliterating pulmonary veins, without granulomatous involvement of pulmonary arteries. Noncaseating granulomas were also present in the liver and hilar lymph nodes, confirming the diagnosis of sarcoidosis. To our knowledge this is the first reported case of pulmonary hypertension caused by sarcoidosis simulating pulmonary veno-occlusive disease.

Adult↗
PubMed1986

Relationship between lung volume, maximal expiratory flow, forced expiratory volume in one second, and tracheal area in normal men and women.

Tracheal area at different lung volumes was measured using acoustic reflection technique, flow-volume curves, and lung volumes by body plethysmography in 24 healthy adults (14 men, 10 women) in order to study the relationship between tracheal area and lung volume, and between tracheal area and maximal expiratory flow rates. Each individual tracheal area was greatest at TLC and lowest at RV; this lung volume dependence was significantly greater in men than in women. When tracheal areas versus absolute lung volumes were plotted for the entire group and the linear regression analysis on the data was performed, no significant correlation between lung volume and tracheal area in men was found, but a highly significant correlation was found in women. Using the analysis proposed by Mead (Am Rev Respir Dis 1980; 121:339-42) in his assessment of dysanapsis, the ratio of tracheal area/lung volume versus lung volume was plotted and the slope was found to be negative (and close to -1) in men and positive in women. Therefore it was concluded that the relationship between tracheal area and lung volume is consistent with the hypothesis that in men and women lung parenchyma grows independently of the airways; furthermore, in women the airways grow faster than the lung parenchyma. In addition, in women there was good correlation between tracheal area and FEV1, as well as maximal expiratory flow rates at 50 and 25% of VC. For men, these correlations were less consistent and depended on the lung volume at which tracheal area was measured.

Adult↗
PubMed1986

Maximum flow ratios at mid-vital capacity in young healthy adults.

Upper airway obstruction is usually diagnosed by visual examination of maximum expiratory and inspiratory flow-volume curves and by calculating a ratio of expiratory to inspiratory flow at 50 percent of vital capacity (mid-vital capacity flow ratio); however, reference values of this ratio have not been well established, and considerable variability exists. The purpose of this study was to examine the range of mid-vital capacity flow ratios in a group of healthy subjects and to determine if some of the variability is accounted for by different maximum inspiratory pressures. We measured maximum expiratory and inspiratory flows at 50 percent of vital capacity from the flow-volume curves, and maximum inspiratory pressures in a group of 60 healthy nonsmokers (30 men and 30 women) whose ages ranged from 21 to 40 years. We found that mid-vital capacity flow ratio (mean +/- SD) was 0.72 +/- 0.19 in men and 0.77 +/- 0.18 in women. The coefficient of variation of the mid-vital capacity flow ratio was 28 percent for men and 23 percent for women. The 95 percent confidence limits for the mid-vital capacity flow ratio were 0.65 to 0.79 for men and 0.70 to 0.84 for women. Maximum inspiratory pressures (mean +/- SD) were 129 +/- 30 cm H2O in men and 91 +/- 16 cm H2O in women, not significantly different from previous studies. Normalizing maximum inspiratory flow for maximum inspiratory pressure did not reduce the coefficient of variation, which became 29 percent in men and 30 percent in women. We conclude that the range of mid-vital capacity flow ratios is wide, and it cannot be reduced by standardizing it for maximum inspiratory pressures.

Adult↗
PubMed1986

Reversible obstructive sleep apnea caused by occupational exposure to guar gum dust.

This report describes a case of reversible obstructive sleep apnea caused by occupational exposure to an inhaled allergen, guar gum powder. The patient, a pet food plant employee, also experienced severe cough, rhinitis, and conjunctivitis. Skin tests confirmed the specific guar allergy. Pharyngeal cross-sectional area was smaller than normal. Pulmonary function studies, histamine challenge tests, nasal air-flow resistance measurements, and nocturnal polysomnography were performed on 3 separate occasions: while the patient was working at his usual occupation, at the end of a 3-wk holiday, and after a guar dust challenge in an inhalation chamber. Pulmonary function and histamine challenge tests were consistently normal. At the time of the initial tests, nasal resistance was elevated, and nocturnal polysomnography revealed obstructive sleep apnea. After absence from work, obstructive sleep apnea resolved, and the nasal resistance returned to normal. After challenge with guar gum dust, the patient developed increased resistance to nasal air flow, and obstructive sleep apnea reappeared. This case demonstrates that allergy can cause reversible obstructive sleep apnea and that occupational exposure should be considered in the assessment of patients with this disease.

Adult↗
PubMed1985

Wall motion in expiratory flow limitation: choke and flutter.

Limitation of expiratory airflow from mammalian airways is currently understood to be due to choking at wave speed (S. V. Dawson and E. A. Elliott. J. Appl. Physiol. 43: 498-515, 1977). A critical weakness of the theory is the lack of a mechanism for the dissipation of energy when effort exceeds that needed for maximal flow. We have observed substantial wall motion with flow limitation in a physical model of a trachea. Therefore we have examined a simple two-dimensional mathematical model, designed to approximate the behavior of the physical model of the trachea, to try to identify a relationship between flow limitation and wall oscillation. The model matches wave-speed predictions when only long waves are considered. The model predicts that aerodynamic flutter will occur in the zone of supercritical flow described in wave-speed theory. Aerodynamic flutter in the zone of supercritical flow provides a potential mechanism for the energy dissipation necessary for transition from supercritical to subcritical flow and explains the high-frequency pure tone heard with flow limitation.

Airway Obstruction↗
PubMed1985

Lung volume dependence of esophageal pressure in the neck.

There is conflicting evidence in the literature regarding tissue pressure in the neck. We studied esophageal pressure along cervical and intrathoracic esophageal segments in six healthy men to determine extramural pressure for the cervical and intrathoracic airways. A balloon catheter system with a 1.5-cm-long balloon was used to measure intraesophageal pressures. It was positioned at 2-cm intervals, starting 10 cm above the cardiac sphincter and ending at the cricopharyngeal sphincter. We found that esophageal pressures became more negative as the balloon catheter moved from intrathoracic to cervical segments, until the level of the cricopharyngeal sphincter was reached. At total lung capacity, esophageal pressures were -10.5 +/- 2.9 (SE) cmH2O in the lower esophagus, -18.9 +/- 3.0 just within the thorax, and -21.3 +/- 2.73 within 2 cm of the cricopharyngeal sphincter. The variation in mouth minus esophageal pressure with lung volume was similar in cervical and thoracic segments. We conclude that the subatmospheric tissue pressure applied to the posterior membrane of the cervical trachea results in part from transmission of apical pleural pressure into the neck. Transmural pressure for cervical and thoracic tracheal segments is therefore similar.

Adult↗
PubMed1985

Pharyngeal compliance in snoring subjects with and without obstructive sleep apnea.

Recent studies have demonstrated a reduction in pharyngeal cross-sectional area and in upper airway muscle tone in patients with obstructive sleep apnea. These findings suggest that the pharynx in such patients may be more compliant than normal even in the awake state. We have tested this hypothesis by examining the pressure-area relationship of the pharynx in 13 patients and in 7 control subjects. Measurements were performed during wakefulness, with the subject seated, and at a constant lung volume near functional residual capacity. Pharyngeal area was measured by an acoustic reflection technique. Pharyngeal pressure was varied by having the subject perform gradual inspiratory and expiratory isovolume maneuvers against a distally occluded airway while mouth pressure was recorded. Specific compliance of the pharynx was calculated as the fractional change in pharyngeal area between a pressure of 0 and -10 cm H2O and and between 0 and 10 cm H2O. Specific pharyngeal compliance was 0.036 +/- 0.004 cm H2O-1 (mean +/- SE) in the control group and 0.094 +/- 0.012 cm H2O-1 in patients with OSA (p less than 0.01). These findings indicate that patients with obstructive sleep apnea have increased pharyngeal compliance. This abnormality predisposes to pharyngeal occlusion during sleep when negative transmural pressures are generated in the pharynx.

Acoustics↗
PubMed1985

Rapid development of obstructive sleep apnea following hemidiaphragmatic and unilateral vocal cord paralysis as a complication of mediastinal surgery.

We describe a patient with obstructive sleep apnea (OSA) who is unusual in two respects: 1) rapid development of severe OSA over a period of two to four months, and 2) direct temporal association between development of OSA and mediastinal surgery complicated by unilateral paralysis of the phrenic nerve and the recurrent laryngeal nerve.

Carcinoid Tumor↗
PubMed1984

Upper airway morphology in patients with idiopathic obstructive sleep apnea.

Fundamental to the pathogenesis of obstructive sleep apnea (OSA) is the interaction of physiologic and anatomic alterations of the upper airway. However, many patients with OSA have no identifiable abnormality of the upper airway, and they have been termed idiopathic. In an attempt to find a structural deviation in upper airway anatomy, we performed acoustic echography and cephalometric roentgenograms in 9 male patients with OSA and no clinical evidence of upper airway abnormality. Mean cross-sectional area of the pharynx by acoustic reflection was less in these patients (3.7 +/- 0.8 cm2) than in subjects in a control group (5.3 +/- 0.6 cm2) (p less than 0.001). Mean glottic cross-sectional area was less in the patient group (1.5 +/- 0.5 cm2) than in the control group (2.7 +/- 0.5) (p less than 0.001). There was a significant correlation between the number of apneas per sleep hour and pharyngeal cross-sectional area (r = 0.87, p less than 0.01). Cephalometric analysis indicated that the patients had smaller mandibles by a mean of 5.4 +/- 6.6 mm (p less than 0.05). The overall posterior displacement of the mandibular symphysis, which is representative of the skeletal support of the anterior pharyngeal wall and is dependent on both mandibular size and position, was highly significant (6.4 +/- 4.7 mm) (p less than 0.01). Furthermore, there was a significant correlation between the number of apnea episodes per sleep hour and the total posterior displacement (r = 0.67, p less than 0.05). This study indicates that patients with so-called idiopathic OSA may have an anatomic predisposition to the development of upper airway occlusion that may not be detectable on clinical examination.

Adult↗
PubMed1984

Lung volume dependence of pharyngeal cross-sectional area in patients with obstructive sleep apnea.

We examined the relationship between lung volume and pharyngeal cross-sectional area in 9 obese patients with obstructive sleep apnea and 10 age-matched, obese subjects without sleep apnea. Pharyngeal area was measured in the upright, seated posture using an acoustic reflection technique. Measurements were made at a rate of 5 per second during a slow exhalation from total lung capacity (TLC) to residual volume (RV). In the control subjects, the mean +/- SE pharyngeal area was 5.6 +/- 0.2 cm2 at TLC, and decreased by 30 +/- 5% over the vital capacity range to 3.9 +/- 0.3 cm2 at RV. In contrast to the control subjects, in patients with obstructive sleep apnea, pharyngeal area was 5.0 +/- 0.2 cm2 at TLC, and decreased by 54 +/- 6% over the vital capacity range to 2.3 +/- 0.3 cm2 at RV. The difference in pharyngeal area between the patients and control subjects was significant at all lung volumes below TLC, as was the difference in the magnitude of change in pharyngeal area with change in lung volume. The results indicate that in obese patients with obstructive sleep apnea, pharyngeal cross-sectional area is abnormally small, and varies considerably with changes in lung volume. The beneficial effects of weight reduction in such patients may relate to the coincident increase in functional residual capacity, causing an increase in upper airway size.

Adult↗
PubMed1984

Tracheal stenosis measured by the acoustic reflection technique.

We examined the usefulness of the acoustic reflection technique for measurement of airway area in 6 patients with tracheal stenosis. In each patient, we obtained airway area by acoustic reflections in the upright position, maximal expiratory and inspiratory flow-volume curve, and radiographs of the trachea. We identified acoustic and radiographic stenotic segments and compared their length, their distances from the glottis, and their cross-sectional areas. We found that (1) in all subjects except one, flow-volume curves did not suggest upper airway obstruction, (2) tracheal stenosis was confirmed by acoustic and radiographic measurements in all subjects, and (3) area of the stenotic segment showed less variation with lung volume than that of the nonstenotic segment. Length of the stenotic segment (mean +/- SE) was found to be 4.9 +/- 0.2 cm (acoustic versus 4.8 +/- 0.3 cm (radiographic); distance between the midglottis and maximal stenosis was 5.7 +/- 0.4 cm (acoustic) and 5.6 +/- 0.6 cm (radiographic); minimal acoustic cross-sectional area was 1.7 +/- 0.1 cm2 versus a radiographic circular cross-sectional area of 1.2 +/- 0.1 cm2. During slow expiration from total lung capacity to residual volume, average cross-sectional area of the stenotic segment decreased by 19.5 +/- 3.0% (mean +/- SE), whereas that of the distal nonstenotic segment decreased by 48.5 +/- 2.2% and that of the proximal nonstenotic segment by 43.6 +/- 5%. We conclude that the acoustic technique, which is rapid and noninvasive, is useful in confirming tracheal stenosis in patients with normal flow-volume curves, and in assessing elastic properties of the trachea.

Acoustics↗
PubMed1984

Estimation of changes in alveolar-arterial oxygen gradient induced by hypoxia.

The alveolar-arterial oxygen tension difference provides a useful clinical indication of ventilation-blood flow mismatching in the lungs. In some clinical situations involving alveolar hypoxia (e.g., patients with chronic obstructive lung disease flying in commercial aircraft or normal humans at high altitudes) it would be useful to know this tension difference to predict the likely arterial PO2 under such potentially stressful conditions. Such estimates would require multiple arterial punctures performed under a variety of trying circumstances, conditions usually far distant from a suitable analytic facility. Consequently, we induced controlled hypoxia in 23 healthy humans and calculated changes in the alveolar-arterial oxygen tension difference during the hypoxic challenge test. We plotted this difference as a function of the alveolar oxygen tension over a range from 35 to 110 mm Hg. In addition to a series of control studies in which multiple arterial blood samples were obtained, we calculated arterial PO2 by converting the arterial oxyhemoglobin saturation (measured with an ear oximeter) into partial pressure of oxygen. During hypoxic procedures in which levels of oxygenation fell on the steep section of the oxyhemoglobin dissociation curve, fixing PCO2 at constant predetermined levels allowed accurate predictions of arterial PO2. We were able to demonstrate that the alveolar-arterial oxygen tension difference narrowed with decreasing alveolar oxygen tension, and that measurement with an ear oximeter provided data that allowed a reasonable estimate of the tension difference during hypoxic conditions.

Adult↗