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Biomedical subjects

S Permutt

Publications and source records attributed to S Permutt.

At least 127 records · Page 7Linked to original sources
PubMed1977

Aspiration pneumonia: beneficial and harmful effects of positive end-expiratory pressure.

With an ex vivo, isolated, ventilated, perfused canine pulmonary lobe, the effects of various levels of positive end-expiratory pressure (PEEP) were evaluated following acid injury. Following intrabronchial instillation of hydrochloric acid, eight lobes were ventilated with 5 cm of H2O of PEEP, 12 lobes with 10 cm of PEEP, and eight lobes with 15 cm of PEEP during a 4 hour perfusion period. Blood flow was kept constant in all preparations. Lobes with 5 cm of PEEP developed a 39% intrapulmonary shunt and increased their weight by 220%. When PEEP was increased to 10 cm, weight gain was similar (184%), but shunting decreased markedly, to 7%. When PEEP was increased further to 15 cm, shunting remained low (13%), but weight gain increased markedly, to 411% of the initial lobe weight. This study demonstrates the beneficial effects of PEEP in aspiration pneumonia, but it also points out that increasing levels of PEEP can magnify acid-pulmonary injury by causing a further increase in interstitial and intralveolar edema.

Animals↗
PubMed1976

Aspiration pneumonia: experimental evaluation of albumin and steroid therapy.

An experimental model using an ex vivo perfused ventilated canine pulmonary lobe was used to study aspiration pneumonia. After intrabronchial acid instillation, the lobe weight tripled, air way pressure and pulmonary artery pressure doubled, and intrapulmonary shunting increased from 5.5% to 53.4%. If large quantities of albumin were added to the lobe perfusate 5 minutes after intrabronchial acid instillation, weight gain, air way and pulmonary artery pressure, and intrapulmonary shunting were unchanged from control levels. If large quantities of steroid were added to the lobe perfusate 5 minutes after intrabronchial acid instillation, the lobe weight doubled but air way pressure and pulmonary artery pressure, and intrapulmonary shunting were not significantly different from control values. It is surmised that intrapulmonary acid aspiration causes an immediate and marked changed in pulmonary capillary permeability. Albumin administration by counteracting this permeability change, and steroid administration by modifying the permeability change, are both beneficial following acid aspiration.

Albumins↗
PubMed1976

Airway responses to methacholine in allergic and nonallergic subjects.

After inhalation challenge with methacholine, bronchoconstrictor responses were produced in allergic subjects with asthma and hay fever as well as nonallergic subjects. Our results indicate that allergic persons possess a greater pulmonary responsiveness to inhalation of this parasympathomimetic agent than nonallergic subjects; however, patterns of response were different in the 2 types of allergic subjects, those with asthma and those with hay fever. Whereas both types of allergic subjects responded with changes in specific airway conductance when nonallergic subjects did not, only asthmatic subjects differed from nonallergic subjects when comparisons of spirometry were made. These data suggest that there is hypersensitivity of both central and peripheral airways in asthmatics and in the larger central airways of nonasthmatic allergic subjects.

Adult↗
PubMed1976

Lung volumes and compliance in myasthenia gravis and reversible airway obstruction.

A patient with myasthenia gravis, reversible airway obstruction, and a vertical chest wall pressure-volume curve was shown to inflate his lungs to 12 liter during the night. During the day, either spontaneously or after isoproterenol, his functional residual capacity decreased by more than 2 liter. The large lung volume changes occurred without a change in slope of the static pressure-volume curve of the lung above functional residual capacity. The changes in the position of this curve might be due to the the very slow filling and emptying of bullae or to unexplained alterations in the length-tension characteristics of the alveoli. The vertical pressure-volume curve of the chest wall suggested that, unlike other patients who have normal or decreased chest wall compliance, this patient's chest wal was not a factor that limited ventilation at high lung volumes.

Airway Obstruction↗
PubMed1976

A comparison of pulmonary function in male smokers and nonsmokers.

Results of certain tests of pulmonary function, including a questionnaire, single-breath N2 test of closing capacity, forced expiration, and diffusing capacity were significantly different in groups of male smokers and nonsmokers. The influence of age on these smoking-related changes of pulmonary function was evaluated. The analyses indicated that (1) some tests including number of symptoms; closing capacity, i.e., closing volume plus residual volume as a percentage of total lung capacity; residual volume as a percentage of total lung capacity; Phase III of the single-breath N2 test, and steady-state diffusing capacity (ml of CO/mm Hg - min) revealed significant differences between adjusted mean smoker and nonsmoker values but did not reveal differences associated with age. (2) Tests of forced expiration (1-sec forced expiratory volume/vital capapity, reciprocal of the maximal mid-expiratory flow, maximal flow at 50 per cent of vital capacity; and moments) however, revealed differences between smoker and nonsmoker means )adjusted and unadjusted), as well as increasing smoker-nonsmoker differences with increasing age. It is suggested that the first group of tests probably measured an all-or-none response that occurred with the onset of smoking and was not affected by duration of smoking. The second group of tests probably measured the effects of continued smoking and indicated increasing abnormality associated with longer exposure (years of smoking). Test showing age-related differences between smokers and nonsmokers may reflect cummulative, irreversible changes in pulmonary function to a greater extent than test that do not.

Adolescent↗
PubMed1976

Clinical, epidemiologic, and pulmonary function studies in alpha,-antitrypsin-deficient subjects of Pi Z type.

The results of pulmonary function testing and systematic medical history and epidemiologic data collection are reported for 20 persons with alpha 1-antitrypsin deficiency of Pi Z phenotype. The most common symptom, reported in 19 subjects (95 per cent), was dyspnea on exertion; 16 subjects (80 per cent) gave a history of wheezing, and 8 (40 percent) reported chronic cough and sputum production. The 8 women who had been pregnant reported a miscarriage rate of 29 per cent for all pregnancies. Respiratory symptoms and disease were commonly reported in the children of study subjects. Pulmonary function testing revealed abnormalities for 18 of 20 subjects, all of those 26 or more years of age. The test that was most frequently abnormal was the 1-sec forced expiratory volume expressed as a per cent of the forced vital capacity. All pulmonary function studies demonstrated a trend toward increased impairment with increased age, which was evident by the fourth decade. Within this group of persons having severe alpha1-antitrypsin deficiency, there was no correlation between serum concentrations of antitrypsin and subjective or objective indices of pulmonary disease. A group of 7 subjects who were incidentally found to have Pi Z alpha1-antitrypsin deficiency exhibited symptoms and pulmonary function abnormalities comparable to those of 13 subjects who were originally referred for known or suspected pulmonary disease. These data suggest that if interventions such as smoking cessation and occupational counseling are to be effective, they should be initiated before the fourth decade of life.

Adult↗
PubMed1976

Tissue pressures and fluid dynamics of the lungs.

A pressure more negative than pleural surface pressure has to be applied to water on the pleural surface to keep it from being absorbed; yet, there is a thin layer of liquid in the pleural space under normal physiological conditions. How is the pressure of the liquid related to the pressure on the surface of the pleural membranes? There is evidence that the liquid pressure might be less than the surface pressure, and the balance is achieved by points of contact between the pleural membranes with tissue deformation forces. If it is possible for liquid and surface pressure to be different in the intrapleural space, the same mechanisms might be active within the lung tissue. Information about the tissue pressures can be estimated by determining the pressures acting on the outer surfaces of intrapulmonary vessels. There is evidence that some vessels of the lungs have a surface pressure close to alveolar pressure (alveolar vessels) and others have a surface pressure that falls relative to pleural pressure as alveolar pressure is increased relative to pleural pressure (extra-alveolar vessels). There appears to be a complete dissociation between the surface pressures and the liquid pressure surrounding the pulmonary blood vessels. These observations provide strong support for the concept that the pressure of liquid within tissue need not be the same as the tissue pressure.

Blood Pressure↗
PubMed1975

Cardiovascular changes in conscious dogs during spontaneous deep breaths.

Cardiovascular functions were evaluated beat by beat during 29 spontaneous deep breaths in three conscious dogs. When pleural pressure was significantly lower than during quiet breathing, stroke volume was reduced, heart rate elevated, as well as transmural pressure in the pulmonary artery (PPA-Ppl) and in the thoracic aorta (PAO-Ppl); the left ventricular filling pressure (LVEDP-Ppl) did not decrease. The authors suggest that these findings are not consistent with the classical hypothesis which explains the decrease in left ventricular output primarily by a reduction in the venous return to the left heart. The results indicate that the decrease in pleural pressure is responsible for an increase in the afterload on the left heart and suggest that this is the predominate factor in the reduction of the stroke volume without decrease in left ventricular filling pressure.

Animals↗
PubMed1975

Effect of intrathoracic pressure on pressure-volume characteristics of the lung in man.

Quasi-static pressure-volume (P-V) curves in normal seated human subjects were determined with pressure at the airway opening (Pa0) set below (negative pressure), above (positive pressure), or equal to ambient pressure. Dynamic compliance (Cdyn) during controlled continuous negative pressure breathing (CNPB) was also studied. Quasi-static P-V curves at negative pressure were decreased in slope, reflected a decrease in total lung capacity, and intersected the P-V curve obtained at ambient Pa0. At positive pressure the P-V curves showed an increase in slope and an increase in total lung capacity. During CNPB a fall in Cdyn was found. The fall in Cdyn was rapid and persisted for the duration of CNPB. Cdyn promptly returned to control levels when Pa0 was adjusted to ambient pressure.

Adult↗
PubMed1975

Effects of hypoxic and CO hypoxia on isolated hearts.

Isolated perfused dog hearts were made hypoxic by respiring the support dog with low oxygen (hypoxic hypoxia) or with carbon monoxide (CO hypoxia). Each heart was exposed to both types of hypoxia, separately. Effects on coronary flow (Qt), coronary vascular resistance, cardiac oxygen consumption (Vo2), and contractility (%deltadP/dt) were studied. Two series of experiments were done. Series I: At constant perfusion pressure. As oxygen content (Cao2) was lowered from 20 to 5 vol%, Qt doubled with hypoxic hypoxia and almost tripled with CO hypoxia (P less than 0.01). Vo2 and contractility increased with both types of hypoxia. Beta-adrenergic blockade eliminated the increase in VO2 and contractility but not the difference in Qt increase between hypoxic and CO hypoxia. Series II: At constant Qt (with beta-blockade), vascular resistance decreased more with CO than hypoxic hypoxia. Finally, alpha-blockade eliminated the difference in vascular resistance and thus with complete (alpha and beta) blockade, the two types of hypoxia have the same effect and are indistinguishable.

Animals↗
PubMed1975

A genetic-epidemiologic study of chronic obstructive pulmonary disease. I. Study design and preliminary observations.

Although certain environmental agents (e.g., cigarette smoking) are known to be causally related to chronic obstructive pulmonary disease (COPD), differential response to their deleterious effects suggests the importance of constitutional (host) factors. The voluminous literature on the familial occurrence of COPD as well as the association between genetically determined serum alpha 1-antitrypsin (alpha 1-at) deficiency and COPD, however, reveals many aspects yet to be clarified. Studies of alpha 1-at indicate that neither its nature nor its relationship to COPD is simple. Moreover, other familial factors are likely involved. To obtain a better understanding of the etiology and pathogenesis of COPD, both genetic and environmental factors are being examined in a multifaceted investigation. The preliminary observations are summarized. COPD patients have a higher frequency of Pi variant phenotypes than those without lung disease. Among other subjects, both cigarette smoking and Pi variant phenotypes are associated with increased pulmonary function abnormality. Finally, there is familial aggregation of pulmonary impairment that cannot be explained entirely by Pi type or smoking.

ABO Blood-Group System↗
PubMed1975

Mechanisms of enhancement of cardiac output during paced tachycardia in conscious dogs.

The mechanisms of enhancement of cardiac output of unanesthetized dogs from 2.7 to 3.6 l min-1 during paced heart rate increase from 92 to 178 beats min-1 were studied in 92 trials with 5 dogs. This enhancement of cardiac output was accompanied by a 0.6 mm Hg fall in right atrial pressure and a 3.3 mm Hg fall in left ventricular end-diastolic pressure. The results are compatible with the hypothesis that an isolated rise in cardiac function shifts blood from the heart and lungs into the systemic circulation which increases the degree of filling of the peripheral vessels and hence increases mean systemic pressure. We postulate that decompression of both atria reflexly raises the tone of the peripheral vessels while the increase in arterial blood pressure reflexly lowers the tone. Apparently a balance is achieved that results in an elevated mean systemic pressure, displacement of the venous return curve to the right, and an increase in the amount of venous return that matches the enhanced cardiac output.

Animals↗