Expiratory mechanics before and after uncomplicated heart surgery.

In 12 mechanically ventilated anesthetized paralyzed patients undergoing cardiac surgery for either coronary bypass or for correcting valvular dysfunction volume, airflow, tracheal, esophageal, and transpulmonary pressures were measured. Respiratory system elastance and resistance were partitioned into their lung and chest wall components throughout tidal relaxed expiration. Measurements were performed prior to thoracotomy and just after rib cage closure. Before surgery, patients with valvular disease had significantly higher respiratory system and lung elastances and resistances than those with ischemic heart disease. After surgery, patients with valvular disease showed a decrease in respiratory system and lung resistances. Surgery strikingly modified chest wall resistive properties in both groups. Postoperatively, the mechanical properties of the respiratory system were very similar in valvular and ischemic patients.

Vagal influences on respiratory mechanics, pressures, and control in rats.

In eight spontaneously breathing anesthetized rats airflow, volume, and tracheal pressure were measured. The passive and active mechanical properties of the respiratory system, the shape of the tracheal occlusion pressure wave (Potr), the decay of inspiratory muscle pressure during expiration, and parameters related to the control of breathing were computed both before and after bilateral cervical vagotomy. Pre- and post-vagotomy values of passive elastance, resistance, and time constant were similar. Active mechanics disclosed an increase of elastance and a decrease in resistance and in the time constant after vagotomy. The time course of Potr showed a downward concavity and was not modified by vagotomy in the range of control inspiratory times, whereas the shape of inspiratory muscle pressure decay during expiration was changed. The present data help to explain why after vagotomy the load-compensatory mechanisms are less effective.

Respiratory mechanics in the aging rat.

1. Mechanical behavior of the respiratory system and pulmonary histopathology were investigated in young (8 months) and old (18 months) adult Wistar rats. 2. Respiratory mechanics were studied under static conditions and during both relaxed and forced expiration. Morphological studies consisted of descriptive light microscopy analysis of intratracheally-fixed, paraffin-embedded pulmonary tissue. 3. Old animals exhibited morphological emphysema and chronic bronchitis, decreased respiratory system (2.40 vs 3.42 cm H2O/ml) and lung (1.32 vs 2.30 cm H2O/ml) elastances, forced vital capacity (13.00 vs 14.32 ml), forced expiratory mean flows between 50 and 75% (35.67 vs 60.50 ml/s) and 75 and 100% (6.67 vs 17.67 ml/s) of forced vital capacity, and an increased respiratory system time constant (0.114 vs 0.082 s) in relation to young rats. 4. These results indicate that old animals suffer from a chronic obstructive pulmonary disease that resembles human pulmonary emphysema.

Respiratory system, lung, and chest wall mechanics in guinea pigs.

1. Volume, airflow, tracheal, esophageal and transpulmonary pressures were measured in 6 mechanically ventilated, anesthetized and paralyzed guinea pigs. 2. The elastic and resistive properties of the respiratory system were partitioned into their lung and chest wall components a) following end-inflation occlusion of the airways subsequent to constant flow inspirations, and b) during relaxed expirations following release of occlusion. The values obtained by both methods were similar. 3. Mean respiratory system, lung and chest wall elastances were 3.518, 2.671, and 0.847 cm H2O/ml, respectively. 4. Mean respiratory system, pulmonary and chest wall resistances (at flows of 4.3 ml/s) were 0.302, 0.184, and 0.118 cm H2O ml-1 s, respectively. 5. Respiratory system, lung and chest wall resistances were partitioned into two components: 1) a homogeneous one whose values corresponded to 0.171, 0.095, and 0.076 cm H2O ml-1 s, for respiratory system, lung and chest wall, respectively, and 2) a component due to Pendelluft and stress relaxation and corresponding to 0.131, 0.089, and 0.042 cm H2O ml-1 s, respectively. 6. Resistive pressure vs flow relationships for the respiratory system, lung and chest wall were also determined during the entire tidal expiration. 7. We conclude that the chest wall participates significantly in respiratory system unevenness.

Respiratory mechanics in the aging rat

1. Mechanical behavior of the respiratory system and pulmonary histopathology were investigated in young (8 months) and old (18 months) adult Wistar rats. 2. Respiratory mechanics were under static conditions and during both relaxed and forced expiration. Morphological studies consisted of descriptive light microscopy analysis of intratracheally-fixed, paraffin-embedded pulmonary tissue. 3. Old animals exhibited morphological emphysema and chronic bronchitis, decreased respiratory system (2.40 vs 3.42 cm H2O/ml) and lung (1.32 vs 2.30 cm H2O/ml) elastances, forced vital capacity (13.00 vs 14.32 ml), forced expiratory mean flows between 50 and 75% (35.67 vs 60.50 ml/s) and 75 and 100% (6.67 vs 17.67 ml/s) of forced vital capacity, and an increased respiratory system time constant (0.114 vs 0.082 s) in relation to young rats. 4. These results indicate that old animals suffer from a chronic obstructive pulmonary disease that resembles human pulmonary emphysema

Pre- and postoperative inspiratory mechanics in ischemic and valvular heart disease.

In 12 mechanically-ventilated, anesthetized, paralyzed patients undergoing cardiac surgery for either coronary bypass (six subjects) or to correct valvular disfunctions, volume, airflow, tracheal, esophageal, and transpulmonary pressures were measured. Respiratory system elastance and resistance were partitioned into lung and chest wall components. Resistances were further split into homogeneous and uneven elements. Measurements were performed prior to thoracotomy and just after rib cage closure. Before surgery, valvular patients had significantly higher elastances and uneven resistances of the respiratory system and lung than those with ischemic heart disease. Postoperatively, the patients presented with an increase in respiratory system and lung elastances, a decrease in pulmonary resistance, and a rise in chest wall resistance. Surgically induced mechanical changes were similar in ischemic and valvular patients.

Mechanics in rats by end-inflation occlusion and single-breath methods.

In six mechanically ventilated anesthetized (pentobarbital sodium, 30 mg/kg) paralyzed rats (187-253 g body wt) volume, airflow, and tracheal, esophageal, and transpulmonary pressures were measured. Respiratory system elastic and resistive properties were partitioned into their lung and chest wall components after end-inflation occlusion of the airways subsequent to constant-flow inspirations and during relaxed expiration ensuing release of occlusion. The values provided by both methods were similar. Mean respiratory system, lung, and chest wall elastances amounted to, respectively, 5.536, 3.440, and 2.097 cmH2O.ml-1. Mean values of intrinsic respiratory system, pulmonary, and chest wall resistances (at flows of 3.5 ml.s-1) were 0.235, 0.144, and 0.091 cmH2O.ml-1.s, respectively. Resistive pressure-flow relationships for the respiratory system, lung, and chest wall were also determined during the entire tidal expiration. A linear relationship was found for the former, whereas power functions best described the others: the pulmonary pressure-flow relationship exhibited an upward concavity and that for the chest wall presented an upward convexity.

Toxicity of prolonged exposure to ethanol and gasoline autoengine exhaust gases.

A comparative chronic inhalation exposure study was performed to investigate the potential health effects of gasoline and ethanol engine exhaust fumes. Test atmospheres of gasoline and ethanol exhaust were given to Wistar rats and Balb C mice housed in inhalation chambers for a period of 5 weeks. Gas concentration and physical parameters were continually monitored during the exposure period. Several biological parameters were assessed after the exposure including pulmonary function, mutagenicity, and hematological, biochemical, and morphological examinations. The results demonstrated that the chronic toxicity of the gasoline-fueled engine is significantly higher than that of the ethanol engine.

Effects of formaldehyde and acetaldehyde inhalation on rat pulmonary mechanics.

Two groups of 12 male Wistar rats received either 243 ppm of acetaldehyde or 5.7 ppm of formaldehyde for 8 h a day, 5 days a week during 5 weeks. These levels represent three times the threshold limit values (TLV) for these substances in Brazilian legislation. The animals were evaluated by pulmonary function tests before and after exposure to the pollutants. The data obtained from these rats were compared with those of 12 controls, housed in identical conditions for the same length of time but breathing normal air. The results showed an increase of the functional residual capacity, residual volume, total lung capacity and respiratory frequency in the rats exposed to acetaldehyde atmosphere. The animals exposed to formaldehyde did not present pulmonary function alterations when compared with the controls. The damage caused by acetaldehyde to the peripheral regions of the lung parenchyma, affecting small airways or altering pulmonary elastic properties, is discussed. It is suggested that the Brazilian TLV for acetaldehyde (78 ppm) is not as safe as that for formaldehyde (1.6 ppm).

Pulmonary function of rats exposed to ethanol and gasoline fumes.

This paper describes the effects of repeated exposure to gasoline and ethanol exhaust fumes on the pulmonary mechanics of rats assessed by whole-body plethysmography. Two groups of 12 male Wistar albino rats each were tested before and after exposure to diluted gasoline or ethanol exhaust gases for 5 weeks, 8 h per day and 5 days per week. An additional group of 12 rats were exposed to clean air under the same experimental conditions. The variations of the functional parameters observed in the three groups before and after exposure were compared. Peak Expiratory Flow and Forced Expiratory Mean Flows in the ranges 0-25%, 25-50% and 50-75% of Forced Vital Capacity were significantly reduced in animals exposed to gasoline exhaust fumes, whereas the group exposed to ethanol exhaust fumes did not differ from the control group. This respiratory impairment is probably due to the presence of SO2 and the quality of the hydrocarbons in gasoline exhaust gases.

The study of mechanical properties of rats lungs by whole body plethysmography.

A simple technic for studying the pulmonary mechanics of rats by whole body plethysmography is presented. The parameters measured were: Tidal Volume (TV); Respiratory Frequency (RF); Transpulmonary Basal Pressure (TBP); Dynamic Compliance (Cdyn); Functional Residual Capacity (FRC); Transpulmonary Pressure/Volume curve (TP/V); Forced Expiratory Volume of 1/4 second (FEV 1/4); Expiratory Reserve Volume (ERV); Inspiratory Capacity (IC); Inspiratory Reserve Volume (IRV); Forced Vital Capacity (FVC); Residual Volume (RV); Forced Expiratory Mean Flow between 100-50% (FEMF 100-50), 50-25% (FEMF 50-25) and 25-0% (FEMF 25-0) of the FVC, and Total Lung Capacity (TLC). In order to verify the accuracy of the technic, common male adult Wistar rats, in which pulmonary obstructive disease is normally expected, were first submitted to these functional tests and then to pathological examination. According to the intensity of the morphological pulmonary lesion, the rats were divided in two groups: with and without suppurative pneumopathy. The analysis of the pulmonary function data showed significant decrease of the FEV 1/4 and FEMF 50-25 and increase of the FRC and RV in the groups with pulmonary suppuration. Thus, a discriminant function could be established to characterize the two groups with 100% efficiency. It was concluded that these pulmonary function tests are a valuable and reliable tool to detect lung diseases in rats.

The study of mechanical properties of rats lungs by whole body plethysmography.

A simple technic for studying the pulmonary mechanics of rats by whole body plethysmography is presented. The parameters measured were: Tidal Volume (TV); Respiratory Frequency (RF); Transpulmonary Basal Pressure (TBP); Dynamic Compliance (Cdyn); Functional Residual Capacity (FRC); Transpulmonary Pressure/Volume curve (TP/V); Forced Expiratory Volume of 1/4 second (FEV 1/4); Expiratory Reserve Volume (ERV); Inspiratory Capacity (IC); Inspiratory Reserve Volume (IRV); Forced Vital Capacity (FVC); Residual Volume (RV); Forced Expiratory Mean Flow between 100-50

(FEMF 100-50), 50-25

(FEMF 50-25) and 25-0

(FEMF 25-0) of the FVC, and Total Lung Capacity (TLC). In order to verify the accuracy of the technic, common male adult Wistar rats, in which pulmonary obstructive disease is normally expected, were first submitted to these functional tests and then to pathological examination. According to the intensity of the morphological pulmonary lesion, the rats were divided in two groups: with and without suppurative pneumopathy. The analysis of the pulmonary function data showed significant decrease of the FEV 1/4 and FEMF 50-25 and increase of the FRC and RV in the groups with pulmonary suppuration. Thus, a discriminant function could be established to characterize the two groups with 100

efficiency. It was concluded that these pulmonary function tests are a valuable and reliable tool to detect lung diseases in rats.