Perfusion of lung periphery: effects of local exposures to ozone and pressure.

Following ozone (O3) exposure, airways reactivity increases. We investigated the possibility that exposure to O3 causes a decrease in pulmonary perfusion, and that this decrease is associated with the increase in reactivity. Perfusion was measured with radiolabeled microspheres.

Interstitial fibrosis and collateral ventilation.

Interstitial fibrosis may increase resistance to collateral flow (Rcoll) because of decreased lung volume and destruction of collateral channels or it may decrease Rcoll because of emphysematous changes around fibrotic regions. In addition, if interstitial fibrosis involves a small region of lung periphery, interdependence from surrounding unaffected lung should produce relatively large changes in volume of the fibrotic region during lung inflation. We studied the effects of interstitial fibrosis on collateral airflow by measuring Rcoll at functional residual capacity (FRC) in nine mongrel dogs before and 28 days after the local instillation of bleomycin into selected lung segments.

Bronchial blood flow affects recovery from constriction in dog lung periphery.

We investigated the effect of eliminating the bronchial circulation on recovery time from intravenous histamine challenge in canine lung periphery. Results from animals with intact bronchial circulations were compared with a second group in which the left lower lobe was isolated in situ. The pulmonary artery to this lobe was perfused and a bronchoscope was wedged in a small airway, which provided an index of resistance to airflow through the collateral system.

Pulmonary blood flow affects recovery from constriction in dog lung periphery.

The influence of blood flow through the pulmonary circulation on the time course of recovery of the lung periphery from challenge with three bronchoconstrictive agents was studied in dogs. The rate of perfusion of the left lower lobe was varied between 0 and 300 ml/min. A fiber-optic bronchoscope (OD = 5.

Dry air-induced constriction in lung periphery: a canine model of exercise-induced asthma.

We studied the effects of the flow of dry air on collateral tone in the lung periphery. A bronchoscope was wedged in sublobar segments of anesthetized dogs, and measurements of collateral resistance (Rcs) were recorded before and after flow was increased from 200 to 2,000 ml/min for a 5-min period. Five minutes after exposure was completed, Rcs increased by an average of 117 +/- 25.

Effects of changes in abdominal pressure on left ventricular performance and regional blood flow.

Many clinical conditions are associated with an increase in abdominal pressure. While the effects on venous return have been studied in the past, little attention has been given to the effect of abdominal pressure on left-sided hemodynamic events. The effects of acute changes in abdominal pressure (Pab) on left ventricular (LV) hemodynamics and outflow distribution were evaluated in ten open-chest dogs, which had undergone right heart bypass to eliminate the influence of changes in Pab on systemic venous return.

Tonic beta-sympathetic activity in the lung periphery in anesthetized dogs.

The present study was undertaken to determine whether beta-adrenoceptors could be physiologically detected in the lung periphery and whether they were under tonic stimulation in the resting state in anesthetized dogs. A fiberoptic bronchoscope was wedged in a sublobar segment of lung in anesthetized male mongrel dogs for measurement of resistance through the collateral system (Rcs). beta-Agents were delivered locally as aerosols through the bronchoscope, and the response was evaluated by changes in Rcs.

Effect of lung inflation on lung blood volume and pulmonary venous flow.

Phasic changes in lung blood volume (LBV) during the respiratory cycle may play an important role in the genesis of the respiratory wave in arterial pressure, or pulsus paradoxus. To better understand the effects of lung inflation on LBV, we studied the effect of changes in transpulmonary pressure (delta Ptp) on pulmonary venous flow (Qv) in eight isolated canine lungs with constant inflow. Inflation when the zone 2 condition was predominant resulted in transient decreases in Qv associated with increases in LBV.

Local vagal responses in the lung periphery.

In previous work we studied responses to ozone (O3) in the lung periphery of anesthetized male mongrel dogs. O3 (0.1 ppm) delivered locally to the lung periphery through a bronchoscope wedged in a segmental airway increased collateral resistance (Rcs) 31.

Maintenance of muscarinic tone after vagotomy in the lung periphery.

We developed a method for maintaining muscarinic tone in a small region of the lung periphery after vagotomy. A fiber-optic bronchoscope was wedged in a segmental airway of anesthetized male mongrel dogs and was used to deliver aerosols of distilled water (0.1 ml), neostigmine (0.

A re-evaluation of the hemodynamic consequences of intermittent positive pressure ventilation.

The hemodynamic effects of intermittent positive pressure ventilation (IPPV) have generally been considered straightforward, being dominated by the inspiratory reduction in systemic venous return. Paradoxically, there is considerable debate regarding the effects of PEEP. We have studied both right ventricular (RV) and left ventricular (LV) performance during a single IPPV respiratory cycle in dogs with intact circulatory systems or the right heart bypassed in open and closed chest conditions.

Effects of ozone on peripheral lung reactivity.

In previous studies, we demonstrated that local exposures to the lung periphery to 0.1 ppm ozone (O3) produce increases in resistance to flow through the collateral system (Rcs) which are prevented by vagotomy, and the local exposures to 1.0 ppm O3 produces increases in Rcs which are only partially mediated by the parasympathetic system.

Responses of the lung periphery to 1.0 ppm ozone.

We studied responses of the lung periphery to short-term exposures of 1.0 ppm ozone (O3). A fiber-optic bronchoscope was wedged in a segmental airway of anesthetized male mongrel dogs and was used to deliver O3 to a small portion of lung.

Augmentation of cardiac function by elevation of intrathoracic pressure.

We studied the cardiovascular effects of increasing intrathoracic pressure in an acute pentobarbital-anesthetized canine model of acute ventricular failure induced by large doses of propranolol. Left ventricular (LV) function curves were generated by volume loading from LV filling pressures of 5-20 Torr. The animals were ventilated by using intermittent positive-pressure ventilation with large tidal volumes (30 ml/kg).

Responses of the lung periphery to ozone and histamine.

We studied the effects of ozone (O3) and histamine on the lung periphery. A fiber-optic bronchoscope was wedged in a segmental airway of anesthetized male mongrel dogs. Measurements of collateral resistance (Rcoll) were used to monitor responses to O3 and to histamine.

Airway reactivity in the periphery of the lung in mongrel dogs. Male and female differences.

The present study was designed to compare acute responses of the lung periphery to locally administered histamine in male and female dogs. A fiberoptic bronchoscope was wedged in peripheral airways of anesthetized dogs. Increasing doses of histamine were directed through the bronchoscope.

Effects of antihistamines and indomethacin on hyperosmolar-induced vasodilation.

The circulatory effects of iv injections of hyperosmolar solutions were studied both in intact dogs with aortic flow probes and in dogs using a standard right heart-bypass preparation. Serial iv injections of 20 ml of 10% NaCl or 50 ml of 25% mannitol produced reproducible episodic vasodilation characterized by falls in mean aortic pressure from 99 +/- 10 (SE) to 61 +/- 6 Torr and increases in aortic flow from 2.20 +/- 0.

Effect of PEEP on left ventricular function in right-heart-bypassed dogs.

Positive-pressure ventilation with positive end-expiratory pressure (PEEP) has been associated with elevation of left ventricular filling pressure for a stable or reduced cardiac output. To exclude the possibility that right ventricular distension due to increased pulmonary vascular resistance decreases left ventricular compliance (ventricular interdependence), we studied the effect of PEEP on left ventricular function in open-chest right-heart-bypassed dogs. A rightward shift of the left ventricular function curve was caused by 15 cmH2O PEEP without a change in the aortic pressure-flow relationship.

Mechanical effects of inspiration on heart functions: a review.

Left ventricular stroke volume decreases during inspiratory efforts whether lung volume is actually increasing as in normal inspiration or whether it remains constant as in a Mueller Maneuver (M.M.).

The effects of positive end-expiratory pressure on right and left ventricular performance.

The cardiovascular effects of positive end-expiratory pressure (PEEP) were studied in mechanically ventilated, vagotomized, Beta-blocked, anesthetized dogs. To compensate for the effect of PEEP on decreasing systemic venous return, acute plasma volume expansion was accomplished returning stroke volume and cardiac output to control values. Left and right ventricular filling pressures (LVFP and RVFP) and aortic pressure were measured relative to pressure (transmural pressure).

Left ventricular hemodynamics during respiration.

We have investigated the mechanisms involved in the inspiratory fall in left ventricular stroke volume (LVSV), utilizing a spontaneously breathing dog on right-heart bypass (RHBP). We have been able to control lung volume, pulmonary artery inflow, and right-heart volume (RHV). During Mueller maneuvers in one series, RHV was allowed to increase as pleural pressure (Ppl) fell; in a second series, changes in RHV were excluded.

Effects of spontaneous respiration on canine left ventricular function.

The purpose of this study was to determine the mechanism of the decrease in left ventricular stroke volume during spontaneous inspiration. We determined the transmural pressures of the left heart by measuring left atrial and diastolic left ventricular pressures relative to esophageal pressure. We estimated the directional changes in end-systolic and end-diastolic volumes of the left ventricle by determining the transit time of sound transmission between two ultrasonic crystals facing each other across the minor axis of the left ventricle.

Monitoring exposure of brewery workers to CO2: a study of cellar workers and controls.

Carbon dioxide exposure of nineteen cellar workers and twenty nonexposed controls in a medium size brewery was assessed by determining base excess and standard bicarbonate of the plasma before work on Monday and after work on Monday and Friday. Standard bicarbonate averaged 0.6mEq/L higher in the cellar workers than the controls when samples taken at the same time were compared.

Hypotension and respiratory distress caused by rapid infusion of mannitol or hypertonic saline.

Following a case of mannitol-induced respiratory and circulatory collapse, the effects of hyperosmolar injections on pulmonary arterial pressure, systemic blood pressure, and cardiac output were studied in dogs. The injection of 20 ml of 10% NaCl into the pulmonary artery increased pulmonary arterial pressure and decreased systemic blood pressure by approximately 50% of control values. Injections of solutions of equal hyperosmolar strength, 50 ml of 25% mannitol or 50 ml of 4% NaCl into the pulmonary artery produced no significant elevation of pulmonary arterial pressure, but were associated with comparable decreases in systemic blood pressure.