Early life indicators of first lactation milk yield and the effect of treatment for bovine respiratory disease on survivability and risk of pregnancy in Holstein dairy cattle.

The primary objective of this study was to evaluate the long-term effects of variables that could be measured early in life on first lactation milk production. The secondary objective was to evaluate the long-term effects of treatment for bovine respiratory disease (BRD), within the first 120 days of life, on survivability to 850 days and reproductive success. Data from Holstein heifer calves was collected from 1 October, 2015-31 January, 2020 and included milk consumption (MC; n = 10,431), bodyweight (BW; n = 9,825), average daily gain (ADG; n = 6,194), heifer conception age (n = 10,112), and 305-day first lactation milk production (305 M; n = 5,823), and treatment records for BRD (n = 12,485). Calves were fed pasteurized whole milk through an automated calf feeding system for 60 days (range, 48 - 126 days), with a 30% crude protein (CP) and 5% crude fat enhancer added at 20 g/L milk. Calves were weighed at birth, weaning, and several other times prior to 2 years of age. Daily BW were predicted for individual animals using a third order orthogonal polynomial to model individual BW regressions. Daily BW predictions were used to calculate ADG and BW predictions on specific days of interest. Season born, ADG (0-400 days), milk production potential, and heifer conception age had a significant impact on 305-day first lactation milk production (all P ≤ 0.05; r2 = 0.31). A retrospective cohort study was conducted utilizing data collected from a commercial farm with cohorts defined by BRD status. Calves treated for BRD from 61 to 120 days old had a significantly lower chance of survival to 850 days of age than animals not treated for BRD. Additionally, calves treated for BRD from 61 to 120 days old had reduced risk of pregnancy. The results show the impact of early life on future milk production, survivability, and pregnancy risk on a commercial dairy herd.

Methacholine challenge: test-shortening procedures.

STUDY OBJECTIVES: Validation of test-shortening procedures for the 2-min tidal breathing methacholine challenge method. DESIGN: Retrospective chart review. SETTING: Tertiary-care university clinical pulmonary function laboratory. PATIENTS: One thousand subjects aged 10 to 85 years (mean +/- SD, 44.5 +/- 16.0 years), 44.5% male, referred for methacholine challenge. INTERVENTION: Two-minute tidal breathing methacholine challenge was performed, with both physician and technician access to published test-shortening procedures. MEASUREMENTS AND RESULTS: There were 315 positive test results (provocative concentration of methacholine causing a 20% fall in FEV(1) [PC(20)] < or = 8 mg/mL) and 685 negative test results. The subjects with positive test results were less likely to be male (39.1 vs 47.5%; p < 0.02) and had lower FEV(1) (91.8 +/- 14.9% predicted vs 97.2 +/- 13.9% predicted; p < 0.001). The average starting PC(20) was between 0.5 mg/mL and 1.0 mg/mL; the most common PC(20) was 1 mg/mL (67%). There were 431 skipped concentrations in 380 subjects. The mean number of methacholine inhalations was 3.7 +/- 1.1 (3.9 +/- 0.1 for negative test results vs 3.3 +/- 1.2 for positive test results; p < 0.001). Eighteen subjects had a > or = 20% FEV(1) fall on the first inhalation, and 11 subjects had a > or = 20% FEV(1) fall after a skipped concentration. In only one case (0.1%) an FEV(1) fall > or = 40% on the first concentration was reported, compared with no cases after a skipped concentration and seven cases with a > or = 40% FEV(1) fall after a routine doubling dose step-up. CONCLUSIONS: The 2-min tidal breathing methacholine test in clinical practice can be safely shortened to an average of less than four inhalations using starting concentrations based on FEV(1), asthma medication, and clinical features, and by occasionally omitting concentrations.

Routine pulse oximetry during methacholine challenges is unnecessary for safety.

BACKGROUND: Methacholine-induced bronchoconstriction is associated with significant hypoxemia, which can be assessed noninvasively by transcutaneous oxygen tension and pulse oximetry. OBJECTIVES: To assess the value of the monitoring of finger pulse oximetry during routine methacholine challenges in a clinical pulmonary function laboratory with regard to both safety and the possibility that a significant fall in oxygen saturation as measured by pulse oximetry (SpO(2)) might be a useful surrogate for determining the response to methacholine. METHODS: Two hundred consecutive patients undergoing diagnostic methacholine challenges in the pulmonary function laboratory of a tertiary-care, university-based referral hospital were studied. Methacholine challenges were performed by the standardized 2-min tidal breathing technique, and the DeltaFEV(1) was calculated from the lowest postsaline solution inhalation to the lowest postmethacholine inhalation value. SpO(2) was measured immediately prior to each spirogram, and the DeltaSpO(2) was measured from the lowest postsaline solution inhalation value to the lowest postmethacholine inhalation value. We examined the data for safety (ie, any SpO(2) value < 90). Based on previous reports, we used a DeltaSpO(2) of > or = 3 as significant and looked at the sensitivity, specificity, and positive and negative predictive values for DeltaSpO(2) > or = 3 vis-à-vis a fall in FEV(1) of > or = 15%. RESULTS: There were 119 nonresponders (DeltaFEV(1), < 15%) and 81 responders. The baseline FEV(1) percent predicted was slightly but significantly lower in the responders (responders [+/- SD], 91.6 +/- 15%; nonresponders, 96.4 +/- 14%; p < 0.05). DeltaSpO(2) was 3.1 +/- 1.6 in the responders and 1.6 +/- 1.8 in the nonresponders (p < 0. 001). There was a single recording in one patient of SpO(2) < 90 (88). A DeltaSpO(2) > or = 3 had a sensitivity of 68%, a specificity of 73%, a positive predictive value of 63%, and negative predictive value of 77% for a fall in FEV(1) > or = 15%. CONCLUSIONS: Pulse oximetry is not routinely useful for safety monitoring during methacholine challenge. DeltaSpO(2) is not helpful in predicting a positive spirometric response to methacholine. However, the negative predictive value is adequate to allow the DeltaSpO(2) to be used as an adjunct in assessing a negative result of a methacholine test in patients who have difficulty performing spirometry.

Positive human health effects of wearing a respirator in a swine barn.

STUDY OBJECTIVES: A study was conducted to evaluate the acute health effects of wearing an N-95 disposable respirator in a swine confinement facility. DESIGN: A crossover trial design was used in the study. SETTING: The study was carried out at the research facilities of the Centre for Agricultural Medicine, the Royal University Hospital, and the Prairie Swine Centre Inc, Saskatoon, Saskatchewan, Canada. PARTICIPANTS: Twenty-one nonsmoking healthy male subjects with no previous swine barn exposure participated in the study. INTERVENTIONS: The subjects participated in a laboratory session (baseline day), a 4-h exposure in a traditional swine room wearing the respirator (intervention day), and a 4-hour exposure in a traditional swine room without a respirator (nonintervention day). MEASUREMENTS: Lung function, methacholine challenge tests, blood counts, nasal lavage, and cytokines in serum and nasal lavage fluid. RESULTS: Mean (+/- SE) shift change in FEV(1), from preexposure to postexposure, was highest on nonintervention day (-8.1+/-1.01%) and was significantly different from intervention day (0.32+/-0.62%; p<0.0001) and baseline day (1.57+/-0.51%; p<0.0001). Similar patterns were observed in the mean values of the provocative concentration of a substance (methacholine) causing a 20% fall in FEV(1) (nonintervention day, 130.4+/-36.9 mg/mL; intervention day, 242.0+/-38.0 mg/mL; and baseline day, 328.0 mg/mL +/-34.1 mg/mL). Significant increases in serum neutrophil levels and nasal cell counts were observed on the nonintervention day in comparison to the baseline and intervention days. Significant increases also were found in the levels of cytokines interleukin (IL)-6 and IL-8 in nasal lavage fluid and in the levels of IL-6 in serum for the nonintervention day in comparison to the other 2 days. CONCLUSIONS: The results demonstrate that an N-95 disposable respirator can help to significantly reduce acute negative health effects in subjects not previously exposed to a swine barn environment.

Systemic thermal injury in anesthetized rabbits causes early pulmonary vascular injury that is not ablated by lazaroids.

PURPOSE: To study the effects of a systemic thermal injury on the pulmonary vasculature with and without inhibitors of lipid peroxidation (U74389G). METHODS: In a prospective, placebo control, randomized, and blinded multi-group study, burn shock was induced by scalding thermal injury (65C) to 35% body surface area in rabbits (n = 28). Hemodynamics and gas exchange were followed for 240 min post burn in four groups: No Burn, Burn-Control, Burn-U74 (10 mg.Kg-1 U74389G), No Burn-U74 (10 mg.Kg-1 U74389G). RESULTS: Scald resulted in early pulmonary injury as measured by increased pulmonary vascular resistance in the pooled Burn group compared with the No Burn groups (942 +/- 358 vs 605 +/- 255 dynes.sec-1.cm-5 respectively, P < 0.05). These pulmonary changes were associated with alveolar sequestration of leukocytes (4.8 +/- 2.9 vs 17.7 +/- 6.0 cells x 10(9).L-1, P < 0.05) in the No Burn and Burn groups respectively. Histological evidence of decreased neutrophil sequestration after scald injury was present in U74 treated animals (3+ vs 2+, P < 0.05 in the Burn and No Burn groups respectively and 2+ vs 2+, P > 0.05 in the Burn-U74 and No Burn-U74 groups respectively) although bronchial alveolar lavage still demonstrated neutrophil sequestration (5.3 +/- 2.5 vs 12.2 +/- 3.3 cell 10(9).L-1, P < 0.05 in No Burn-U74 and Burn-U74 groups respectively). Similarly, circulating white blood cells were increased in the Burn group but not Burn-U74 group four hours post burn. The increase in pulmonary vascular resistance after burn was not altered by administration of U74. CONCLUSIONS: Systemic burn results in early pulmonary vascular changes associated with leukocyte sequestration. After scald injury administration of lazaroids (U744389G) did not lessen pulmonary vascular resistance changes but did reduce neutrophil sequestration.

Predictors of longitudinal changes in pulmonary function among swine confinement workers.

OBJECTIVE: To determine predictors of longitudinal changes in pulmonary function in swine confinement workers. DESIGN: Longitudinal study conducted from November 1989 to June 1991 and January 1994 to May 1995. SETTING: Swine confinement workers in Saskatchewan. PARTICIPANTS: Forty-two swine confinement workers who were studied in 1989/90 and studied again in 1994/95. RESULTS: Of 98 male swine confinement workers (mean age SD 36.3 11.1 years) studied at baseline, 42 were studied again five years following. Complete information on baseline across-shift pulmonary function (preshift forced expiratory volume in 1 s [FEV1], forced vital capacity [FVC], and every 2 h FEV1 and FVC during the shift), and five-year follow-up pulmonary function (with FEV1 and FVC) were available on all 42 subjects. Mean across-shift changes (preshift measurement to last measurement of the day) at baseline were -159. 8 61.7 mL in FEV1 and -35.3 65.6 mL in FVC. Mean annual rate change between baseline and follow-up for FEV1 was -53.9 61.7 mL/year and for FVC -48.9 71.6 mL/year. After adjusting for age, height, smoking and hours spent in the barn, the baseline across-shift change in FEV1 and FVC was a significant predictor of annual rate change in FEV1 (P=0.01) and FVC (P=0.02), respectively. To determine the effects of indoor air quality on longitudinal lung function decline, indoor air environmental measurements were analysed. Complete information on respiratory health and indoor air quality was available on 34 of the 42 subjects. Assessment of indoor environment of swine barns included a summer and winter measurement for airborne dust, gases and endotoxin levels. After adjusting for age, height, smoking, ammonia and hours spent in the barn, the endotoxin level (Eu/mg)was a significant predictor of annual rate change for FEV1 but not FVC. CONCLUSIONS: These results suggest that shift change is an important predictor of longitudinal changes in lung function in swine confinement workers and that endotoxin exposures may mediate annual decline in FEV1 in these workers.

The effects of U-74389G, a 21-aminosteroid, on pulmonary vascular resistance after a scald.

We tested U-74389G (C37H50N6O2-CH4O4), a 21-aminosteroid, to determine whether it ameliorates the pulmonary vascular effects of a surface scald. We studied 24-anesthetized rabbits mechanically ventilated with 100% and then 13% O2. Twelve rabbits received a scald (75 degrees C water applied to the shaved ventral surface for 90 seconds), and 12 served as control (20 degrees C water). Six control and six scalded animals additionally received U-74389G (5 mg/ kg intravenously). We measured hemodynamics and blood gases prescald, 30 minutes postscald, and 30 minutes after U-74389G or placebo administration. The strength of hypoxic pulmonary vasoconstriction (HPV) was assessed as the difference between pulmonary vascular resistance measured during 13% O2 ventilation and during 100% O2 ventilation. Hemodynamics and gas exchange were similar between groups. The strength of HPV was significantly diminished postscald, but U-74389G treatment restored HPV to baseline values. We conclude that a scald reduces the strength of HPV, and the response to U-74389G suggests this may be mediated by free radicals.

Positive human health effects of dust suppression with canola oil in swine barns.

A crossover trial was conducted to evaluate the acute human health effects of a dust control technology in a swine confinement facility. Twenty lifetime nonsmoking male subjects, with no evidence of allergy or asthma and no previous swine barn exposure, participated in the study, which included a laboratory session (baseline), 5-h exposure in a swine room sprinkled with canola oil (treatment) and 5-h exposure in a traditional swine room (control). Mean values of inhalable dust concentrations and endotoxin levels in the control room were significantly greater than those observed in the treatment room. Mean shift changes in FEV1 from preexposure to end of exposure were 1.1% (standard error, 0.63%) on baseline day, -1.9% (0.63%) on treatment day, and -9.9% (1.12%) on control day; the differences in the shift changes were statistically significant. Mean value of methacholine concentration that reduced the FEV1 by 20% (PC20) in bronchoprovocation tests on baseline day was significantly different from that on treatment day (p = 0.04) and that on control day (p < 0.001). Significant increases were also observed in white blood cell counts and nasal lavage cell counts on the control day in comparison with the other two days. Blood neutrophil counts after control room exposure were twice those observed on baseline and after exposure to the treatment room. Significant differences were also observed in IL-1 beta, IL-6, and IL-8 nasal lavage cytokines and in IL-6 serum cytokine. These results suggest that the canola oil dust control method is effective in improving indoor air quality in swine barns and reducing acute health effects in naive healthy subjects.

Accelerated lung function decline in swine confinement workers.

We conducted a longitudinal study to determine the annual rate decline in pulmonary function measurements in male swine confinement workers. For comparison, a grain farming group and a nonfarming rural-dwelling control group were also chosen for the longitudinal study. Two hundred seventeen swine confinement workers, 218 grain farmers, and 179 nonfarming control subjects had valid pulmonary function measurements at the baseline observation conducted in 1990 to 1991 and at the second observation conducted in 1994 to 1995. The swine confinement workers were younger (mean age=38.3+/-11.7 [SD] years) than the nonfarming control subjects (42.6+/-10.4 years) and the grain farmers (44.5+/-11.9 years). When stratified by age, nonfarming control subjects had the lowest mean annual rate decline in FEV1 and FVC in all age categories. The swine confinement workers had the largest annual rate decline in FEV1 and FVC, and this was most obvious in the middle age categories. After controlling for age, height, smoking, and baseline pulmonary function, swine confinement workers had excess annual decline of 26.1 mL in FEV1 (p=0.0005), 33.5 mL in FVC (p=0.0002), and 42.0 mL/s in forced expiratory flow between 25% and 75% of FVC (FEF[25-75%]) (p=0.02) over nonfarming control subjects. Grain farmers had excess annual decline of 16.4 mL in FEV1 (p=0.03), 26.7 mL in FVC (p=0.002), and 11.2 mL/s in FEF(25-75%) (p=0.38) over control subjects. These findings suggest that workers engaged in the swine industry and grain farmers appear prone to accelerated yearly losses in lung function and may therefore be at risk for the future development of chronic airflow limitation.

Controlled-release theophylline inhibits early morning airway obstruction and hyperresponsiveness in asthmatic subjects.

BACKGROUND: Nocturnal asthma reflects the severity of the disease, and thus its pharmacologic prevention represents one on the main goals of asthma management. SUBJECTS AND METHODS: To determine whether controlled-release theophylline inhibits the development of airway obstruction and/or airway hyperresponsiveness early in the morning, we examined 18 subjects reporting recurrent nocturnal asthma. In each subject, after five days' treatment with an 8 PM increasing dose of oral controlled-release theophylline, up to 10 +/- 1 mg/kg or placebo the night before the study day, we measured serum theophylline, FEV1 and PC20FEV1 at 6 AM, 2 PM and 10 PM. RESULTS: At 6 AM, both FEV1 and PC20FEV1 were significantly higher on theophylline than on placebo (3.52 +/- 0.22 versus 3.17 +/- 0.25 L; P < .005 and 2.76 divided by 3.61 versus 1.55 divided by 3.73 mg/mL; P < .05, respectively). At 2 PM and 10 PM FEV1, but not PC20FEV1, was higher on theophylline than on placebo (3.73 +/- 0.21 versus 3.54 +/- 0.25 L; P < .05 and 3.40 +/- 0.22 versus 3.24 +/- 0.24 L; P < .05). Serum theophylline was 12.8 +/- 1.1 micrograms/ml, 8.9 +/- 0.77 and 9.5 +/- 0.85 at 6 AM, 2 PM and 10 PM, respectively. CONCLUSIONS: We conclude that an evening dose of controlled-release theophyl line inhibits early morning airway obstruction and hyperresponsiveness, and that it may be helpful in the prevention of nocturnal asthma.

Lazaroids--not nitric oxide synthetase inhibitors--improve hemodynamics after thermal injury in anesthetized guinea pigs.

Our objective was to study the effects of a lipid peroxidation inhibitor (U74389G) and nitric oxide synthetase inhibitor (NG-methyl-L-arginine) on hemodynamic stability in burn shock. The design was a prospective, placebo control, randomized, and masked multigroup study in a research laboratory of a university hospital. We used 24 guinea pigs (N = 24), and induced burn shock by a scalding thermal injury (75 degrees C) to 35% of their body surface area. Hemodynamics and gas exchange were observed for 90 minutes after the burn injury in the four groups: no burn, burn-control, burn-U74 (10 mg/kg U74389G), and burn-LNMA (20 mg/Kg NG-methyl-L-arginine). The percentage of mean arterial pressure, normalized for the initial value at 30 minutes after the burn injury, decreased in all groups over time but was not significantly different in any group. The normalized percentage of flow also decreased over time in all groups with the slope of the linear regression significantly less in the burn-U74 group (-0.32 95% CI, -0.05, -0.15) and the no burn group (-0.37 95% CI, -0.48, -0.26), compared with the burn-control group (-0.66 95% CI, -0.77, -0.56) and the burn-LNMA group (-0.66 95% CI, -0.77, -0.56). The slope of the linear regression for the normalized percentage of systemic vascular resistance was significantly more marked in the burn-control group (2.45 95% CI, 1.35, 3.54) and the burn-LNMA group (1.22 95% CI, 0.89, 1.55) compared with the no burn group (0.16 95% CI, 0.11, 0.44) or the burn-U74 group (0.34 95% CI, 0.06, 0.74). The burn shock resulted in hemodynamic instability as measured with increased systemic vascular resistance, decreased cardiac output, and mean arterial pressure. Use of a lazaroid (U74389G), not a nitric oxide synthetase inhibitor (NG-methyl-L-arginine), altered the clinical course after thermal injury. These data suggest the importance of lipid peroxidation and free radicals as secondary mediators in the evolution of burn shock.

Pulmonary vascular effects of endotoxin in canine lobes pretreated with dapsone.

Endotoxin results in a granulocyte mediated loss of hypoxic pulmonary vasoconstriction (HPV). Dapsone blocks the granulocyte respiratory burst and might, therefore, preserve HPV following endotoxin. Isolated-perfused canine lobes (n = 6) were pretreated with 18 mg/kg dapsone (dapsone group), and compared to six lobes which did not receive dapsone (control group). Total pulmonary vascular resistance (Rtot) and arterial, middle (Rm), and venous segmental resistances were calculated by a vascular occlusion technique. We then administered endotoxin (2 mg/kg) and repeated measurements at 5, 30, and 90 min. The increase in Rm during 3% O2 compared to 35% O2 ventilation was used to define the presence of HPV. In the control group, following endotoxin, values of Rm did not change (P > 0.05) during 3% O2 ventilation (0.011 +/- 0.006 cm H2O/ml/min) compared with 35% O2 ventilation (0.014 +/- 0.005 cm H2O/ml/min). In the dapsone group, following endotoxin, values of Rm increased (P < 0.05) during 3% O2 ventilation (0.06 +/- 0.026 cm H2O/ml/min) compared with 35% O2 ventilation (0.03 +/- 0.015 cm H2O/ml/min). Changes in 6-keto PGF1 alpha or thromboxane B2 do not explain these observations. We conclude that in this experimental preparation, pretreatment with dapsone prevents the loss of HPV associated with endotoxin.

Respiratory health status in swine producers using respiratory protective devices.

A cross-sectional survey on respiratory health in swine producers showed that 30% of 301 examined men usually used a dust mask when working inside a barn. They did not differ significantly from dust mask nonusers in respect to respiratory symptoms and lung function. This analysis was undertaken to determine whether the respiratory health of dust mask users was associated with reasons why they had started individual respiratory protection. The subjects were recontacted in order to identify those who started using a mask to deliberately prevent symptoms (42 men) and those who started protection because of pre-existing respiratory symptoms (44 men). Not unexpectedly, between-group comparisons of respiratory symptoms and lung function suggest that swine producers who wear dust masks for preventive purposes have better respiratory health than those who wear dust masks because of symptoms or those who do not use individual respiratory protection. The individual reasons for starting dust mask usage should be examined among potential determinants of the outcomes of prospective studies which can then provide more valid assessment of the effect of individual respiratory protection.

Respiratory health of swine producers. Focus on young workers.

In this report, we compare the respiratory health of swine producers, grain farmers, and nonfarming control subjects, separately in all age groups and in young subjects. We examined 249 swine producers (age 37.7 years), 251 grain farmers (age 44.7 years), and 263 nonfarming subjects (age 40.7 years). Swine producers had significantly more symptoms of chronic bronchitis (15.3 percent) than did grain farmers (7.2 percent) or nonfarming men (5.7 percent). After controlling for age, height, and smoking, the functional indices of airflow (FEV1, FEV1/FVC, FEF25-75, Vmax50, and Vmax25) were slightly but significantly lower in swine producers than in grain farmers. In comparison with nonfarming subjects, swine producers also had significantly lower FEV1/FVC, FEF25-75, and Vmax50. Respiratory symptoms were associated with the number of hours of work per day. This indirect index of exposure was also inversely associated with FVC (p < 0.01) and FEV1 (p = 0.06), after adjustment for age, height, smoking, and dust mask usage. A relative excess of respiratory symptoms and lower lung function variables were found in swine producers aged 26 to 35 years. Also in this age group, a multivariate analysis revealed statistically significant effects of daily duration of work on FVC and FEV1. The results confirm that working in swine confinement units is a risk factor for chronic respiratory symptoms and minor lung function changes. An increased risk in young workers may reflect more intense occupational exposure in this subgroup of swine producers.

Changes in PETCO2 and pulmonary blood flow after bronchial occlusion in dogs.

The use of PETCO2 in detecting accidental bronchial intubation was investigated. The PETCO2 was measured in six mongrel dogs after occluding the left mainstem bronchus in three conditions; pentobarbital anaesthesia, 0.8% halothane insufflation together with pentobarbital anaesthesia, and simultaneous left pulmonary artery and bronchial airway occlusion with intravenous pentobarbital anaesthesia. An external flow probe measured left pulmonary artery blood flow. The PETCO2 decreased after bronchial occlusion during pentobarbital (35 +/- 3 vs 30 +/- 5 mmHg) and halothane-pentobarbital (30 +/- 6 vs 25 +/- 6 mmHg) conditions (P less than 0.05). However, within three minutes of bronchial occlusion, the values of PETCO2 had returned to their pre-occlusion values. After five minutes of bronchial occlusion pulmonary artery blood flow in the non-ventilated lung decreased (P less than 0.05) during pentobarbital (770 +/- 533 ml.min-1 vs 575 +/- 306 ml.min-1) and halothane-pentobarbital (495 +/- 127 ml.min-1 vs 387 +/- 178 ml.min-1) conditions. Simultaneous bronchial and pulmonary artery occlusion prevented any changes in PETCO2. It was concluded that accidental one-lung ventilation results in small and transient decreases in PETCO2. A redistribution of blood flow from the non-ventilated to ventilated lung occurs which restores PETCO2 to the original values observed with two-lung ventilation.

Right-sided aortic arch presenting as refractory intraoperative and postoperative wheezing.

A 29-year-old woman presented with severe refractory intraoperative wheezing and airflow limitation that resolved spontaneously. Contrast-enhanced computed tomographic (CT) scan of the thorax confirmed a right-sided aortic arch. Variable intrathoracic large airway obstruction that worsened markedly when the patient was in a supine position and slightly more following intravascular volume expansion was shown on flow-volume studies. We postulate the right-sided aortic arch caused airflow obstruction that worsened intraoperatively because of position and intravenous fluids.

Increased airways responsiveness in swine farmers.

A respiratory questionnaire, pulmonary function tests, and an examination of airways responsiveness were conducted on 20 swine farmers and 20 control subjects. The swine farmers represented almost the complete work force from 13 Hutterite colonies and had worked in confinement buildings with more than 2,000 swine (3,270 +/- 1,221 swine) for at least four hours (6.6 +/- 1.8 hours) per day for more than two years (10.5 +/- 7.5 years). The control subjects were randomly selected from outdoor city workers from the city of Saskatoon and were matched for gender, age (+/- 2 years), and smoking status. Eleven swine farmers (55 percent) had chronic cough, compared with three (15 percent) of the control subjects (p less than 0.01). Eight (40 percent) of the swine farmers had symptoms of wheezing, compared with three (15 percent) of the control subjects (p less than 0.05). The FEV1 was significantly lower in swine farmers (97.2 +/- 11.5 percent predicted) than in control subjects (106.0 +/- 12.0 percent of predicted) (p less than 0.05). Airways responsiveness was measured by methacholine challenge with doubling concentrations ranging from 0.25 to 256 mg/ml. The provocation concentrations resulting in a reduction of 10 percent (PC10) and 20 percent (PC20) in FEV1 were lower in swine farmers than in control subjects (PC10, 77.2 +/- 78.8 mg/ml vs 180.8 +/- 96.5 mg/ml; p less than 0.01; and PC20, 154.5 +/- 99.9 mg/ml vs 229.6 +/- 66.8 mg/ml; p less than 0.05). Twelve swine farmers (60 percent) had PC20 of less than 256 mg/ml, compared with three (15 percent) of the control workers (p less than 0.01). Fewer swine farmers demonstrated atopy as measured by skin prick tests than did control workers (21 percent vs 56 percent; p less than 0.05). These findings suggested that occupational exposure in swine confinement buildings is associated with mild increases of nonspecific, nonatopic airways responsiveness in swine farmers.

Effects of halothane on hypoxic pulmonary vasoconstriction in canine atelectasis.

We studied the interactions of atelectasis and halothane on hypoxic pulmonary vasoconstriction using an isolated canine lobe. We divided pulmonary vascular resistance into arterial, venous, and middle segmental resistances by a vascular occlusion technique. We found that middle segmental resistance significantly increased (P less than 0.05) from 0.016 +/- 0.007 cm H2O.mL-1.min-1 during normoxic ventilation to 0.06 +/- 0.007 cm H2O.mL-1.min-1 during hypoxic ventilation. We then produced sublobar atelectasis by introducing 4.5-mm steel ball bearings into the lobar bronchus, which resulted in a significant increase (P less than 0.05) of middle segmental resistance to 0.046 +/- 0.014 cm H2O.mL-1.min-1 during normoxic ventilation and a further significant increase (P less than 0.05) to 0.084 +/- 0.02 cm H2O.mL-1.min-1 during hypoxic ventilation. Ventilation with 2.0% halothane but not 0.5% halothane prevented the increases in middle segmental resistance observed with either atelectasis or hypoxic ventilation. Values of arterial and venous segmental resistances were not similarly affected. We conclude that sublobar atelectasis increases pulmonary vascular resistance by stimulating hypoxic pulmonary vasoconstriction. Both halothane and hypoxia primarily act upon the middle vascular segment, but their effects are in opposite directions and, in the former instance, are concentration-dependent.