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Biomedical subjects

A Baydur

Publications and source records attributed to A Baydur.

46 records · Page 3Linked to original sources
PubMed1983

Active inspiratory impedance in halothane-anesthetized humans.

We have used the method of Siafakas et al. (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 51: 109-121, 1981) to determine active elastance (E'rs) and flow resistance (R'rs) of the respiratory system in eight spontaneously breathing humans anesthetized with halothane. From measurements of flow (V) and volume (V) during unoccluded inspirations and of tracheal pressure (P0tr) during subsequent inspirations with the airways occluded at end expiration, we were able to compute E'rs and R'rs as slopes and intercepts of the following function: -P0tr/V = R'rs + E'rsV/V. These measurements were repeated during inspirations loaded with a series of linear flow resistances (delta R). Neither E'rs nor R'rs was significantly affected by delta R. On the average E'rs and R'rs were, respectively, 34.4 and 16.7% higher than the corresponding passive elastance and flow resistance of the respiratory system, indicating that during active breathing the internal impedance of the respiratory system increases. This provides an internal mechanism by which passive loads are compensated.

Adult↗
PubMed1983

Respiratory mechanics during halothane anesthesia and anesthesia-paralysis in humans.

In six spontaneously breathing anesthetized subjects [halothane approximately 1 maximum anesthetic concentration (MAC), 70% N2O-30% O2], we measured flow (V), volume (V), and tracheal pressure (Ptr). With airway occluded at end-inspiration tidal volume (VT), we measured Ptr when the subjects relaxed the respiratory muscles. Dividing relaxed Ptr by VT, total respiratory system elastance (Ers) was obtained. With the subject still relaxed, the occlusion was released to obtain the V-V relationship during the ensuing relaxed expiration. Under these conditions, the expiratory driving pressure is V X Ers, and thus the pressure-flow relationship of the system can be obtained. By subtracting the flow resistance of equipment, the intrinsic respiratory flow resistance (Rrs) is obtained. Similar measurements were repeated during anesthesia-paralysis (succinylcholine). Ers averaged 23.9 +/- 4 (+/- SD) during anesthesia and 21 +/- 1.8 cmH2O X 1(-1) during anesthesia-paralysis. The corresponding values of intrinsic Rrs were 1.6 +/- 0.7 and 1.9 +/- 0.9 cmH2O X 1(-1) X s, respectively. These results indicate that Ers increases substantially during anesthesia, whereas Rrs remains within the normal limits. Muscle paralysis has no significant effect on Ers and Rrs. We also provide the first measurements of inspiratory muscle activity and related negative work during spontaneous expiration in anesthetized humans. These show that 36-74% of the elastic energy stored during inspiration is wasted in terms of negative inspiratory muscle work.

Adult↗
PubMed1983

Lung mechanics in sitting and horizontal body positions.

We measured lung compliance, pulmonary flow-resistance, and expiratory reserve volume (ERV) in ten healthy young adults in sitting, supine, and lateral positions. Average lung compliance was 0.21 in sitting, 0.19 in lateral and 0.16 L.cm H2O-1 in supine positions. The change was significant (p less than 0.01) between sitting and supine position. Flow-resistance increased from 1.78 in sitting to 2.5 cm H2O.L-1.s (p less than 0.001) in lateral positions, and did not increase further in the supine posture in spite of a 35 percent decrease in ERV (p less than 0.001). Since it is known that lower airways resistance increases with decreasing lung volume, the lack of change in flow-resistance when shifting from lateral to supine posture suggests that upper airways flow-resistance (larynx and oropharynx) is greater in the lateral decubitus than in the supine positions. The decrease of lung compliance in horizontal postures probably reflects increased pulmonary blood volume and small airways closure.

Adult↗
PubMed1982

A simple method for assessing the validity of the esophageal balloon technique.

The validity of the conventional esophageal balloon technique as a measure of pleural pressure was tested in 10 subjects in sitting, supine, and lateral positions by occluding the airways at end-expiration and measuring the ratio of changes in esophageal (delta Pes) and mouth pressure (delta Pm) during the ensuing spontaneous occluded inspiratory efforts. Similar measurements were also made during static Mueller maneuvers. In both tests, delta Pes/delta Pm values were close to unity in sitting and lateral positions, whereas in the supine position, substantial deviations from unity were found in some instances. However, by repositioning the balloon to different levels in the esophagus, even in these instances a locus could be found where the delta Pes/delta Pm ratio was close to unity. No appreciable phase difference between delta Pes and delta Pm was found. We conclude that by positioning the balloon according to the "occlusion test" procedure, valid measurements of pleural pressure can be obtained in all the tested body positions.

Adult↗
PubMed1979

Acute respiratory failure and pulmonary arteritis without parenchymal involvement: demonstration in a patient with rheumatoid arthritis.

A 28-year-old woman with a eight-year history of rheumatoid arthritis presented with a three-day history of dyspnea. Physical and electrocardiographic findings were consistent with pulmonary hypertension. Arterial blood gases revealed a ventilation-perfusion mismatch. Chest roentgenogram was normal. After transient improvement, she suddenly deteriorated and died. At autopsy, a necrotizing pulmonary panarteritis was found without parenchymal involvement by rheumatoid disease. The pulmonary arteries were the only vessels affected. Immunofluorescent staining revealed immunoproteins scattered throughout the vessel walls without localization to the basement membrane. The unique features of the case are discussed in relation to pulmonary hypertension and rheumatoid lung disease in which vascular lesions are usually associated with honeycomb lung. The association between the rheumatoid arthritis and pulmonary vasculitis was probably coincidental.

Acute Disease↗
PubMed1977

The spectrum of extrapulmonary tuberculosis.

The incidence of new cases of extrapulmonary tuberculosis has remained constant, despite the decline in new cases of active pulmonary tuberculosis. This might be due to a delay in recognition, and particularly a lack of consideration of tuberculosis when the presenting symptoms are other than respiratory. Extrapulmonary tuberculosis should be considered in the differential diagnosis of bone, joint, genitourinary tract and central nervous system (CNS) diseases. To determine factors that might delay recognition and identification, 62 patients having extrapulmonary tuberculosis during 1969-1972 at the Los Angeles County-University of Southern California Medical Center were studied.Three quarters of these patients had had CNS, skeletal or genitourinary tuberculosis in equal distribution or 25 percent each. CNS involvement was seen frequently in the disseminated form. Presenting symptoms were protean and not specific, such as fever, anorexia, weight loss, cough, lymphadenopathy and neurologic abnormalities. Roentgenograms of the chest were abnormal in most. When a roentgenogram of the chest suggests pulmonary tuberculosis, signs and symptoms in other body systems should suggest extrapulmonary tuberculosis. If no abnormalities are seen on a roentgenogram of the chest, however, this does not preclude the diagnosis of extrapulmonary tuberculosis. Neither does a negative tuberculin skin test exclude the condition. Abnormal laboratory findings are common, especially in disseminated tuberculosis. These include various anemias, bone marrow disorders, hyponatremia due to inappropriate antidiuretic hormone syndrome. Analyses of pleural, peritoneal, pericardial and joint fluid usually show an exudate high in lymphocytes and occasionally low in glucose. Similar findings are seen in spinal fluid. The histological features of caseous or noncaseous granulomas are suggestive of but not specific for tuberculosis. Only culture of mycobacteria from sputum, urine, spinal fluid, pleural and other effusions and tissue biopsy specimens will yield a definitive diagnosis. Physicians must have a high index of suspicion to diagnose extrapulmonary tuberculosis, as it can resemble any disease in any organ system. Immediate therapy in the disseminated variety, sometimes even before a definite diagnosis can be made, may be lifesaving.

Adolescent↗
PubMed1975

Adenoid cystic carcinoma (cylindroma) of the trachea masquerading as asthma.

A 40-year-old woman was admitted with upper airway obstruction; chest roentgenogram with tomograms, laryngoscopy, and bronchoscopy verified the presence of a subglottic tumor. Spirometry disclosed a maximum inspiratory flow rate more reduced than in the maximum expiratory flow rate, suggestive of upper airway obstruction. The pathologic conditions were consistent with cystic adenoid carcinoma (cylindroma) of the trachea. The patient underwent tracheostomy and total laryngectomy with an uneventful recovery. No evidence of local extension or distant metastases were evident at time of surgery.

Adult↗