PubMed Health⌕ Search

Biomedical subjects

S M Scharf

Publications and source records attributed to S M Scharf.

At least 91 records · Page 5Linked to original sources
PubMed1984

Function of canine diaphragm with hypovolemic shock and beta-adrenergic blockade.

In anesthetized mongrel dogs we investigated the effects of hypovolemia and beta-adrenergic stimulation on the decrease in force generation by the diaphragm [transdiaphragmatic pressure (Pdi)] during electrical stimulation of the phrenic nerves for 1 h. In seven normovolemic dogs with arterial pressure (Pa) of approximately 125 Torr, Pdi fell approximately 48% from an initial value of 35 +/- 4.8 Torr. In dogs made moderately hypovolemic, Pdi was actually higher than with normovolemia (P less than 0.01). In dogs made severely hypovolemic, Pa approximately 50 Torr, Pdi at the start of pacing was less than with normovolemia (25 +/- 1.5 Torr) and remained so during phrenic nerve stimulation. When beta-adrenergic blockade with propranolol was added to moderate hypovolemia, the values of Pdi became similar to those of severe hypovolemia. Analysis of the relative contributions of gastric pressure and pleural pressure revealed that the factor responsible for maintaining Pdi with moderate hypovolemia was pleural pressure. Changes in thoracic gas volume and chest wall configuration did not explain the changes we saw in diaphragm function. Analysis of the relationship between rib cage motion and pleural pressure confirmed our finding of the greater pleural pressure generation with sympathetic stimulation that accompanies hypovolemia. These studies demonstrated that 1) severe hypovolemia impaired diaphragm function, 2) diaphragm function was maintained with moderate hypovolemia by beta-adrenergic stimulation, and 3) with hypovolemia-associated sympathetic stimulation there was an increase in force generation by the intercostal muscles.

Adrenergic beta-Antagonists↗
PubMed1984

Chest wall movements during inspiratory loading in dogs.

In 12 anesthetized mongrel dogs the changes in movements of the rib cage (RC) and abdomen (ABD) were studied during inspiratory loading for 15 min. Tracheal (Pm) and transdiaphragmatic (Pdi) pressures increased to 60-65% of their maxima and were maintained for the 15-min period of loading. Analysis of the EMGs of the diaphragm and intercostals revealed approximately equal recruitment of both these muscle groups. Two types of breathing patterns were observed: (1) abdominal, or normal (9/12 dogs), in which the ABD moved outward during inspiration, and (2) rib cage (3/12 dogs) in which the RC moved outward and the ABD inward during inspiration. The latter were those in whom the ratio of RC width to length was the greatest, and the RC was, presumably, able to resist deformation during inspiration. In most of the abdominal (normal) breathers two phases of RC motion could be seen an initial phase which was either outward or inward, and a final, early expiratory, phase of outward motion. The data indicate that the initial phase of RC motion is influenced by the relative compliance of the RC and ABD, while the final phase relates to the respiratory system rebounding to its relaxation configuration at the onset of respiration.

Abdominal Muscles↗
PubMed1984

Pulmonary edema following relief of upper airway obstruction.

In six pediatric patients, pulmonary edema (PE) appeared on chest x-ray film following intubation for upper airway obstruction (UAO). In spite of the x-ray appearance of PE, there was generally no concomitant physiologic or clinical decline. Only one of the patients required positive airway pressure following intubation. We conclude that PE on chest x-ray film following intubation for UAO is not uncommon, and may not be a harbinger of clinical and/or physiologic deterioration.

Airway Obstruction↗
PubMed1984

"Second wind" during inspiratory loading.

Five human volunteers breathed through an inspiratory register to achieve a transdiaphragmatic pressure (Pdi) of 42-45% of the maximum, until fatigue. During the period of resistive breathing all subjects experienced at least one episode of a sudden feeling of relaxation and relief from dyspnea, i.e., "second wind." These episodes were accompanied by a sudden decrease in the neural stimulation to the diaphragm as reflected in the electromyogram (EMG). Changes in lung volume or chest configuration were eliminated as was recruitment of accessory muscles of inspiration during the "second wind"; thus, there appeared to be a change in the contractile function of the diaphragm such that the same force (Pdi) was achieved with less neural input. These results indicate that the phenomenon of "second wind" has physiologic correlates and may be subject to experimental verification and manipulation.

Adult↗
PubMed1983

Sleep apnea syndrome treated by repair of deviated nasal septum.

Sleep apnea syndrome (SAS) often presents a difficult therapeutic problem to the clinician since many of the accepted modes of therapy are associated with only partial success or with a number of long-term complications. We present three patients with obstructive SAS in whom dramatic clinical improvement occurred following repair of a deviated nasal septum. The subjective improvement was associated with a diminution in the number and duration of obstructive apnea episodes as observed during a standard sleep study. Because of its simplicity and low rate of complication, we propose that repair of a deviated nasal septum be further evaluated as a mode of therapy for this condition.

Adult↗
PubMed1983

Effects of positive and negative pressure ventilation on cardiac performance.

We have critically reviewed our present understanding of the complex hemodynamic events occurring during spontaneous and mechanical ventilation. It is clear that the physiologic events occurring during normal conditions are present but may be relatively less important under pathophysiologic conditions. Furthermore, since spontaneous ventilation and mechanical ventilation are not simply opposites, evaluation of one ventilatory mode aids in understanding the hemodynamic events in the other. While we have not discussed the hemodynamic events during high frequency oscillation, only with a full understanding of both spontaneous respiration and conventional IPPV can the full implications of this new mode of ventilation be appreciated. It seems a reasonable assumption that in the critically ill patient with cardiopulmonary dysfunction, one mode of ventilation will be optimal and another either less so or even detrimental. Only with an understanding of the hemodynamic effects of respiration can the optimal therapeutic modality be tailored to each patient.

Abdomen↗
PubMed1982

Influence of the right ventricle on canine left ventricular function with PEEP.

In anesthetized dogs we evaluated the influence of increased right ventricular (RV) pressures on left ventricular (LV) function by comparing the hemodynamic effects of increases in RV afterload (pulmonary arterial pressure) produced by positive end-expiratory pressure (PEEP) with those due to pulmonary arterial occlusion (PAO). Left atrial (Pla) and right atrial (Pra) pressures increased with PEEP and PAO [for Pla: 3.1 +/- 0.7 Torr (PEEP), 2.4 +/- 0.9 Torr (PAO); for Pra: 2.9 +/- 0.4 Torr (PEEP), 3.1 +/- 1.2 Torr (PAO)]. RV septal-free wall dimension (RVD) increased, and LV septal-posterolateral dimension (L2) decreased with both conditions [increases in RVD: 1.9 +/- 0.3 mm (PEEP), 2.2 +/- 0.5 mm (PAO); decrease in L2: 1.1 +/- 0.4 mm (PEEP), 0.9 +/- 0.3 mm (PAO)]. Extracorporeal bypass of the great veins did not alter these findings. LV function curves showed less stroke work at any Pla during PEEP, this being unaffected by vagotomy. When the RV was bypassed, there were no PEEP or PAO related changes in Pla or LV function. Thus diminished LV function with PEEP is probably due to the influence on the LV of a stressed RV in this situation.

Animals↗
PubMed1982

Effect of interstitial fluid (kerosene) on pressure-volume characteristics of rat lung.

Although pulmonary interstitial edema has been estimated to decrease pulmonary compliance (CL), it has been experimentally difficult to demonstrate whether the observed changes in CL are directly due to the presence of interstitial fluid or if they result instead from concomitant pulmonary vascular engorgement and/or alveolar edema. Since kerosene-inflated lungs do not leak, we were able to use kerosene to measure the effect on CL of the accumulation of interstitial fluid (kerosene) in the postmortem rat lung. Pressure-volume (PV) studies of the lung were done during the progressive increase in interstitial fluid (kerosene). Analysis of the deflation limbs of the quasistatic PV curves obtained following serial inflations with kerosene indicated that the maximal volume of kerosene [MV35, equal to the maximum tissue plus airway volume at a transpulmonary pressure (Ptp) of 35 cmH2O] was 3.8 +/- 1.2 ml (31.0 +/- 11.8%) greater than TLC35 [air volume at Ptp of 35 cmH2O prior to kerosene inflation]. The increases in interstitial kerosene volume had no effect on kerosene PV characteristics, as was demonstrated by superimposing lung PV curves obtained at various states of interstitial filling. We conclude that the interstitial compartment is large and very compliant and that the presence of even great amounts of fluid limited to this compartment does not restrict lung expansion.

Animals↗
PubMed1982

Nonhomogeneous alveolar pressure swings: effect of different respiratory muscles.

We tested the hypothesis in dogs that during isovolumic inspiratory efforts the degree of nonhomogeneity of alveolar pressure changes is influenced by regional differences in respiratory muscle activity. Pressure distal to an occluded right lower lobe bronchus (PRLL) was compared with pressure in the occluded airway opening (PaO) during spontaneous inspiratory efforts (S), during right (RP), left (LP), and bilateral (BP) phrenic nerve stimulation, and during spontaneous inspiratory efforts after cutting both phrenic nerves (SCP), Upper and lower rib cage and abdominal dimensional changes were monitored by magnetometers. PRLL was greater than Pao during S and the difference was greater during BP and greater during RP, whereas with LP and SCP Pao exceeded PRLL. Compared with S, during RP, LP, and BP there was greater upper rib cage inward motion relative to abdominal outward motion. SCP resulted in opposite upper rib cage-abdomen relative motions. Thus activities of various muscle groups produced different regional pressures and deformations of rib cage and abdomen. These results may relate to potential errors in plethysmographic determination of thoracic gas volume in the presence of airway closure.

Abdominal Muscles↗
PubMed1982

Pulmonary mechanics in dogs given different doses of kerosene intratracheally.

Kerosene was instilled intratracheally into mongrel dogs of either sex weighing 10 to 15 kg and anesthetized intravenously with sodium pentobarbital (25 mg/kg). Two different doses were used: 0.3 and 0.06 ml/kg. Pulmonary mechanics, including pressure-volume (P-V) curve, thoracic gas volume (Vtg), total lung capacity (TLC), total pulmonary resistance (RL), and chord compliance (CL) were measured by using a whole body plethysmograph, before and at various time intervals during the 2 wk after instillation. Histologic studies were also performed. In the high-dose (0.3 ml/kg) kerosene experiments there were significant decreases in Vtg, TLC, and CL values by 24 h, which returned to control values at 1 wk after kerosene instillation. The RL and CL normalized for TLC did not change. In contrast, in the dogs receiving the low dose (0.06 ml/kg), there was no significant change in any of these parameters at 24 h. Histologic examination revealed an early exudative phase consisting of exudation of macrophages, red cells, and edema (at 1 and at 24 h), and a later phase consisting of proliferative bronchiolitis (at 1 and at 2 wk). Animals receiving the low dose revealed the same pattern as those receiving the high dose at 24 h, but changes were less extensive. We conclude (1) that kerosene-induced lung injury causes loss of terminal air spaces at both low and high doses, and (2) that the shift in the P-V curve is dose dependent. We hypothesize that kerosene causes two types of physiologic lesions. In areas in which terminal air spaces remained open, an increase in compliance occurred, whereas in areas in which intraalveolar exudation occurred there was "drop-out" of lung units. The final P-V curve was determined by the relative proportions of these two types of areas.

Animals↗
PubMed1981

Progesterone administration and progressive sleep apneas.

Nine adult patients with obstructive sleep apnea syndrome were administered medroxyprogesterone acetate, 60 to 120 mg/day, and the effect of medroxyprogesterone on clinical symptoms and obstructive apneas during sleep was assessed. Four patients responded with resolution of daytime sleepiness, disappearance of pedal edema, and a decrease in the number of obstructive apneas during sleep. Cessation of therapy led to a return of daytime sleepiness in three and an increase in obstructive apneas in all four subjects. Two responders experienced side effects of alopecia or decreased libido. Before medroxyprogesterone therapy, responders were distinguished from nonresponders only by the presence of a significantly lower resting arterial oxygen tension during wakefulness. We characterize a subgroup of patients who benefit from medroxyprogesterone therapy by reducing obstructive apneas during sleep.

Adult↗
PubMed1981

The effects of large negative intrathoracic pressure on left ventricular function in patients with coronary artery disease.

Using first-pass radionuclide ventriculography, we evaluated the effects of decreases in intrathoracic pressure (Mueller maneuver [M] to -20 to -30 cm H2O) in 14 patients with five patients without coronary artery disease (CAD) and in 12 normal control subjects. In the patients with CAD, control ejection fraction was 0.53 +/- 0.06 (SEM) and control heart rate was 83 +/- 6 beats/min. These did not change during M. In the patients with CAD, control ejection fraction was 0.37 +/- 0.03 and heart rate was 82 +/- 7 beats/min. During M, heart rate did not change, but ejection fraction decreased to 0.33 +/- 0.33 (p less than 0.01). Examination of regional wall motion abnormalities showed akinesis of at least one myocardial segment in nine of 14 patients with CAD, but in none of the patients without CAD, nor in any of the 12 previously studied normal subjects (retrospectively analyzed). These data are consistent with the hypothesis that the Mueller maneuver acts to increase afterload placed on the left ventricle. Furthermore, in patients with CAD, the Mueller maneuver may have induced localized myocardial ischemia or unmasked areas of preexisting marginal function.

Aged↗
PubMed1981

Pathologic and physiologic effects of aspiration of hydrocarbons in the rat.

In a series of laboratory rats, pathologic and physiologic changes of the lungs were studied for 2 wk after intratracheal instillation of kerosene. The ratio of lung weight to body weight increased, indicating pulmonary congestion. Pathologically, 2 types of changes were seen: a generalized hyperemia and a focal bronchopneumonia. Physiologically there was an upward shift to the left of the static pressure-volume curve, with increases in total lung capacity of 35 to 40%. This was true whether air or saline was used as the inflating medium. All the changes described were maximal by 24 h after kerosene instillation and tended to return to baseline within 2 wk. Although static compliance of the lung increased, when normalized for total lung capacity there was no change, indicating that the shift was functionally equivalent to opening new lung units. We speculate that the leftward shift in the pressure-volume curve was due either to a reversible effect on lung elastin, or to changes in contractile elements located in lung parenchyma.

Animals↗
PubMed1980

Hemodynamic effects of positive-pressure inflation.

In 14 anesthetized mongrel dogs, we studied the factors that influenced aortic systolic pressure (PaO) and peak aortic systolic flow (Qao) during positive-pressure inflations at three respiratory rates: 8, 14, and 24 breaths/min. At all three respiratory rates, pulmonary arterial flow fell by 15% of the preinspiratory value by end inhalation. Qao also fell at all three respiratory rates, reaching a nadir close to end exhalation (EE). Qao fell less (7% of the base line) at the fast respiratory rate than at the medium and slow respiratory rates (15% of the base line). Pao rose more during the early part of inflation at the medium and fast rates (5 +/- 0.9 Torr) than at the slow rate (3 +/- 0.7 Torr); then Pao fell to a nadir near EE at the slow (-5.6 +/- 1.6 Torr) and at the medium (-2.3 +/- 1 Torr) respiratory rates. At the fast rate it fell to a value not different from control (0.1 +/- 0.5 Torr). The ratio of peak arterial pressure to peak arterial flow increased throughout inflation reaching a peak at EE. A model was developed that predicted the major qualitative features of the changes in Qao seen in these studies. Changes in Pao resulted from the interaction between decreases in Qao and transmitted increases in pleural pressure, and are modified by changes in systemic impedance.

Animals↗