Association of expiratory airway dysfunction with marked obesity in healthy adult dogs

OBJECTIVE: To evaluate the effects of obesity on pulmonary function in healthy adult dogs. ANIMALS: 36 Retrievers without cardiopulmonary disease. PROCEDURES: Dogs were assigned to 1 of 3 groups on the basis of body condition score (1 through 9): nonobese (score, 4.5 to 5.5), moderately obese (score, 6.0 to 6.5), and markedly obese (score, 7.0 to 9.0). Pulmonary function tests performed in conscious dogs included spirometry and measurement of inspiratory and expiratory airway resistance (R(aw)) and specific R(aw) (sR(aw)) during normal breathing and during hyperpnea via head-out whole-body plethysmography. Functional residual capacity (FRC; measured by use of helium dilution), diffusion capacity of lungs for carbon monoxide (DLCO), and arterial blood gas variables (PaO(2), PaCO(2), and alveolar-arterial gradient) were assessed. RESULTS: During normal breathing, body condition score did not influence airway function, DLCO, or arterial blood gas variables. During hyperpnea, expiratory sR(aw) was significantly greater in markedly obese dogs than nonobese dogs and R(aw) was significantly greater in markedly obese dogs, compared with nonobese and moderately obese dogs. Although not significantly different, markedly obese dogs had a somewhat lower FRC, compared with other dogs. CONCLUSIONS AND CLINICAL RELEVANCE: In dogs, obesity appeared to cause airflow limitation during the expiratory phase of breathing, but this was only evident during hyperpnea. This suggests that flow limitation is dynamic and likely occurs in the distal (rather than proximal) portions of the airways. Further studies are warranted to localize the flow-limited segment and understand whether obesity is linked to exercise intolerance via airway dysfunction in dogs.     

Airway reactivity measured by barometric whole-body plethysmography in healthy cats

OBJECTIVE: To assess the validity of barometric whole-body plethysmography (BWBP) as a means of monitoring airway responses to induced bronchoconstriction in healthy cats. ANIMALS: 8 healthy cats without history of bronchopulmonary disease or exposure to indoor tobacco smoke. PROCEDURE: Cats were placed into a barometric plethysmograph with an internal volume of 38 L, and air flow was recorded at baseline and after carbachol (concentrations 0.005, 0.01, 0.02, 0.05, 0.1, and 0.2%) was introduced into the chamber. A dose-response curve was generated for several flow-derived measurements, and airway reactivity was determined by interpolation of the dose-response curve for enhanced pause. RESULTS: Peak inspiratory and expiratory flows increased significantly, but respiratory rate, inspiratory and expiratory times, relaxation time, and tidal volume did not differ significantly from baseline values. Flow-derived measurements (pause, enhanced pause, and end-expiratory pause) increased significantly at carbachol concentrations > 0.02%. Baseline measurements did not correlate with indices of airway reactivity. CONCLUSIONS AND CLINICAL RELEVANCE: Airway reactivity can be measured by use of BWBP, which is noninvasive. Airway reactivity was highly variable among cats and was not a function of baseline airway caliber, suggesting that other intrinsic mechanisms may be important.     

Airway responses to histamine aerosol in clinically normal foods.

OBJECTIVE: To describe the spectrum of nonspecific airway reactivity in a group of clinically normal foals. ANIMALS: 12 clinically normal mixed-breed foals, 48 to 92 days old, without history of clinical lung disease. PROCEDURE: Nonspecific airway reactivity was determined by measuring the extent of changes in dynamic compliance during nebulization of incrementally increasing concentrations of histamine aerosol. Degree of airway reactivity was expressed as the dose of histamine that evoked a decrease in dynamic compliance (Cdyn) to 65% of the after saline nebulization value (PC65Cdyn) or increase in pulmonary resistance (R(L)) to 135% of baseline (PC135R(L)). RESULTS: In all foals, it was possible to induce a decrease in Cdyn in dose-dependent manner to < or = 65% of baseline. Response of foals in terms of R(L) was more erratic, and, in 1 foal, R(L) decreased after histamine exposure. Mean+/-SD PC65Cdyn was 5.43+/-1.74 (range, 0.77 to 19.56) mg/ml, and mean PC135R(L) was 3.34+/-1.52 (range, -0.749 to 17.35) mg/ml. Body weight was not correlated to baseline Cdyn, R(L), PC65Cdyn, or PC135R(L). CONCLUSIONS AND CLINICAL RELEVANCE: Clinically normal foals had a wide range of airway reactivity, which may contribute to variation in clinical responses of foals to otherwise similar stimuli, such as infection, inflammation, and challenge exposure with environmental irritants.     

Evaluation of variables to describe the shape of volumetric capnography curves during bronchoconstriction in dogs

The aim of the study was to investigate changes in volumetric capnography (V(C)) variables during bronchoconstriction in dogs and compare it with total respiratory resistance (R(L)) measured with a Fleisch pneumotachograph. Six dogs were challenged with increasing concentrations of carbachol until obvious signs of bronchoconstriction were seen. All V(C) parameters were obtained before, directly after, 10 and 20 min after maximal bronchoconstriction. The slope of phase III (SIII) and airway and alveolar dead space parameters were significantly different from baseline directly after the challenge. The V(C) curve obtained a typical shape at the time of maximal bronchoconstriction and a trend to return to baseline shape was seen over time. A significant correlation was found for all aforementioned parameters with R(L). We conclude that the shape of the V(C) curve in combination with dead space calculation can be used to verify bronchoconstriction on a breath-to-breath basis.     

Monthly, daily, and circadian variations of measurements of pulmonary mechanics in horses with chronic obstructive pulmonary disease

OBJECTIVES: To determine temporal variations of pulmonary function in horses without respiratory tract disease (controls) and horses with chronic obstructive pulmonary disease (COPD) and determine whether reversibility of airway obstruction after environmental control can be predicted by response to atropine administration. ANIMALS: 7 COPD-affected and 5 control horses. PROCEDURES: Pulmonary function testing was performed monthly during 3 consecutive months, daily for 5 consecutive days, and at 6-hour intervals for 24 hours before and after administration of atropine (0.02 mg/kg of body weight, i.v.) and after 5 consecutive months at pasture. Respiratory rate, tidal volume (VT), minute ventilation (VE), maximal change in transpulmonary pressure (deltaP(L)), pulmonary resistance (R(L)), and pulmonary elastance (E(L)) were calculated. RESULTS: COPD-affected horses had a significantly higher expiratory to inspiratory time ratio (T(E)/T(I)) and deltaP(L), E(L), and R(L) than horses without respiratory tract diseases during all periods and higher V(E) during monthly and daily evaluations. Daily variation in VT and monthly and circadian variation in E(L) were significant in COPD-affected horses. In control horses, significant changes were apparent only in T(E)/T(I) during daily recordings. In COPD-affected horses, reduction in deltaP(L), R(L), and E(L) was significant after atropine administration and after maintenance on pasture. CONCLUSIONS AND CLINICAL RELEVANCE: Despite variations in measurements of respiratory mechanics in both groups of horses, values remained significantly different between groups over time. Despite individual variation, measurements were repeatable during short and long periods. Response to administration of atropine to COPD-affected horses underestimated improvement in respiratory tract function that resulted from maintenance on pasture.     

Benzimidazole-resistant beta-tubulin alleles in a population of parasitic nematodes (Cooperia oncophora) of cattle

Three anthelmintic classes with distinct mechanisms of action are commercially available. Selection of nematode populations resistant to all these drugs has occurred, particularly in trichostrongyloid parasites of sheep. Anthelmintic resistance in cattle parasites has only recently been recognized and appears to be less pronounced, even though very similar species infect both hosts. To understand the bases for differences in the rate of resistance development in sheep versus cattle parasites, it is important to first demonstrate that the same kinds of resistance alleles exist in both. The benzimidazoles (BZ), which have been used for more than 40 years, were chosen as an example. BZ-sensitive (BZ(S)) and BZ-resistant (BZ(R)) nematodes that parasitize sheep have been distinguished at the molecular level by a single nucleotide change in the codon for amino acid 200 of a beta-tubulin gene, a switch from TTC (phenylalanine) to TAC (tyrosine). PCR primers were designed to completely conserved regions of trichostrongyloid beta-tubulin genes and were used to amplify DNA fragments from Haemonchus contortus (cDNA from a BZ(S) and a BZ(R) library) as positive controls. The technique was then extended to the cattle parasites, Cooperia oncophora and Ostertagia ostertagi (from genomic DNA). Sequence analysis proved the presence of amplified BZ(S) alleles in all three species and BZ(R) alleles in the BZ(R) population of H. contortus. Based on these data, nested PCR primers using the diagnostic T or A as the most 3' nucleotide were designed for each species. Conditions for selective PCR were determined. To demonstrate feasibility, genomic DNA was recovered from individual H. contortus L(3) larvae from both BZ(S) and BZ(R) populations. Genomic DNA was also isolated from >70 individual adult male C. oncophora collected from a cattle farm in New Zealand with reported BZ resistance. Allele-specific PCR discriminated among heterozygotes and homozygotes in both species. This method could find utility in studying the molecular epidemiology of BZ resistance in cattle parasites and for defining the variables that limit the development and spread of anthelmintic resistance in this host.     

Relationship of age,sex, body weight,and hematologic and respiratory variables with airway reactivity in adult cats

OBJECTIVE: To evaluate the association between airway reactivity and age, sex, body weight, and radiographic findings in cats. ANIMALS: 32 mature cats that constituted 2 age groups (17 young cats that were 1 to 2 years old and 15 old cats that were 12 to 13 years old). PROCEDURE: Cats were placed in the chamber of a barometric whole-body plethysmograph (volume, 38 L), and box pressure was measured at baseline and after aerosol administration of increasing concentrations of carbachol. Airway reactivity was assessed by monitoring increases in enhanced pause (PENH), a unitless variable that measures bronchoconstriction as derived from dose-response curves. The endpoint chosen was the provocative concentration of carbachol that increased PENH to 300% of the baseline value (PCPENH300). RESULTS: We did not find a correlation between PCPENH300 and sex, body weight, number of eosinophils, PENH before bronchoconstriction, respiratory frequency, tidal volume, or minute ventilation. Airway reactivity was significantly less in the old cats (mean +/- SD PCPENH300, 0.578 +/- 0.051%), compared with the value for the young cats (0.053 +/- 0.006%). Radiographic patterns differed significantly between groups of cats; a greater proportion of old cats (12/15) had bronchointerstitial patterns, compared with the proportion of young cats (4/17). CONCLUSIONS AND CLINICAL RELEVANCE: These data support the notion that age exerts a strong influence on airway reactivity in adult cats, and radiographic differences suggest that structural changes in older cats may contribute to this effect. These findings have important implications for interpretation of results of airway reactivity tests in cats.     

Use of the impulse oscillometry system for testing pulmonary function during methacholine bronchoprovocation in horses

OBJECTIVE: To compare sensitivity of the impulse oscillometry system (IOS) with that of the conventional reference technique (CRT; ie, esophageal balloon method) for pulmonary function testing in horses. ANIMALS: 10 horses (4 healthy; 6 with recurrent airway obstruction [heaves] in remission). PROCEDURE: Healthy horses (group-A horses) and heaves-affected horses (group-B horses) were housed in a controlled environment. At each step of a methacholine bronchoprovocation test, threshold concentration (TC(2SD); results in a 2-fold increase in SD of a value) and sensitivity index (SI) were determined for respiratory tract system resistance (R(rs)) and respiratory tract system reactance (X(rs)) at 5 to 20 Hz by use of IOS and for total pulmonary resistance (RL) and dynamic lung compliance (C(dyn)), by use of CRT. RESULTS: Bronchoconstriction resulted in an increase in R(rs) at 5 Hz (R(5Hz)) and a decrease in X(rs) at all frequencies. Most sensitive parameters were X(rs) at 5 Hz (X(5Hz)), R(5Hz), and R(5Hz):R(10Hz) ratio; RL and the provocation concentration of methacholine resulting in a 35% decrease in dynamic compliance (PC(35)C(dyn)) were significantly less sensitive than these IOS parameters. The TC(2SD) for X(rs) at 5 and 10 Hz was significantly lower in group-B horses, compared with group-A horses. The lowest TC(2SD) was obtained for X(5Hz) in group-B horses and R(5Hz) in group-A horses. CONCLUSIONS AND CLINICAL RELEVANCE: In contrast to CRT parameters, IOS parameters were significantly more sensitive for testing pulmonary function.The IOS provides a practical and noninvasive pulmonary function test that may be useful in assessing subclinical changes in horses.     

Efficacy of a combined oral formulation of derquantel-abamectin against the adult and larval stages of nematodes in sheep, including anthelmintic-resistant strains

Derquantel (DQL), a semi-synthetic member of a novel anthelmintic class, the spiroindoles, in combination with abamectin (ABA) [as the combination product STARTECT(?)] is a new entry for the treatment and control of parasites in sheep. The 19 studies reported herein were conducted in Australia, New Zealand, South Africa and the United Kingdom to demonstrate the efficacy of derquantel-abamectin (DQL-ABA) against a broad spectrum of gastrointestinal and respiratory nematodes of sheep, and to support registration of the combination product. Eleven studies were conducted using natural or experimental parasite infections with unknown or unconfirmed resistance, while eight studies utilised isolates/strains with confirmed or well characterised resistance to one or more currently available anthelmintics, including macrocyclic lactones. All studies included DQL-ABA and negative control groups, and in selected studies one or more reference anthelmintic groups were included. In all studies the commercial formulation of DQL-ABA was administered orally at 2mg/kg DQL and 0.2mg/kg ABA; placebo was administered in the same volume as DQL-ABA; and reference anthelmintics were administered as per label recommendations, except in one instance where levamisole was administered at twice the label dose. Infection, necropsy, worm collection and worm counting procedures were performed using standard techniques. Efficacy was calculated based on the percentage reduction in geometric mean worm count relative to negative control for each nematode species and lifecycle stage targeted. Twenty-two isolates/strains used in the eight studies targeting resistant worms had proven resistance: three to one anthelmintic class, eleven to two classes and eight to three or more classes; of these resistant strains, 16 demonstrated resistance to a macrocyclic lactone anthelmintic. Regardless of resistance status in the 19 studies, DQL-ABA controlled a broad range of economically important gastrointestinal and respiratory nematode parasites of sheep, as follows: ≥ 98.9% efficacy against Haemonchus contortus (adult and L4); Teladorsagia circumcincta (adult, L4 and hypobiotic L4); Teladorsagia trifurcata (L4); Trichostrongylus axei (adult and L4); Trichostrongylus colubriformis (adult and L4); Trichostrongylus falculatus (adult); Trichostrongylus rugatus (adult); Trichostrongylus vitrinus (adult and L4); Cooperia curticei (adult and L4); Cooperia oncophora (adult and L4); Nematodirus spathiger (adult); Nematodirus battus (adult); Nematodirus spp. (hypobiotic L4); Strongyloides papillosus (adult); Strongyloides spp. (L4); Chabertia ovina (adult); Oesophagostomum venulosum (adult); Dictyocaulus filaria (adult); and Protostrongylus rufescens (adult); ≥ 97.0% efficacy against Trichuris ovis (adult); and ≥ 95.9% efficacy against T. trifurcata (adult). Derquantel-abamectin is a highly effective combination anthelmintic, which will provide an important new tool for controlling helminths of sheep when used in conjunction with sustainable drenching practices.     

Whole body barometric plethysmography: a screening method to investigate airway reactivity and acute lung injuries in freely moving pigs

The aim of this work was to investigate whether the Penh index, measured using whole body barometric plethysmography, can be used as a screening parameter to evaluate the airway reactivity and the intensity of the pulmonary response to endotoxins. Penh was firstly recorded in non-sedated freely moving piglets exposed (1) to a nebulized acetylcholine (Ach) pre-treated or not with clenbuterol, or (2) to endotoxin challenge. To measure Penh simultaneously with total pulmonary resistance (R(L)), dynamic compliance (C(dyn)) and intrapleural pressure changes (Max Delta Ppl), an oesophageal balloon catheter technique was used and the piglets were anaesthetised. The recordings were performed during (1) an intravenous metacholine (Mch) challenge and (2) in endotoxin-exposed animals. In freely moving animals, Ach induced a significant dose-dependent increase in Penh, which was significantly blocked by clenbuterol. Endotoxin instillation also resulted in a significant rise in Penh while the corresponding response measured under anaesthesia was significantly and positively correlated with R(L) and Max Delta Ppl. Similar results were obtained during Mch challenge but the Penh was negatively correlated with C(dyn). We conclude that Penh could be used in freely moving piglets as a screening index for airway reactivity and pulmonary functional changes in cholinergic and endotoxin challenges.     

Comparison of forced oscillation with the conventional method for histamine bronchoprovocation testing in horses

OBJECTIVE: To compare response of horses to histamine bronchoprovocation (HBP), using total respiratory resistance (Rrs) measured by forced oscillatory mechanics (FOM) with dynamic compliance (Cdyn) and pulmonary resistance (RL) measured by the esophageal balloon method. ANIMALS: 10 horses with various degrees of airway reactivity. PROCEDURE: The 2 methods for measuring airway responses to HBP were performed on separate days. Endpoints compared were increase of 150 or 200% of baseline Rrs (PC150Rrs, PC200Rrs) and to 150% of baseline RL (PC150RL) or decrease to 65% of baseline Cdyn (PC65Cdyn). Frequency dependence of respiratory mechanics, using FOM, was evaluated, using the slope of Rrs over 1 to 3 Hz and the ratios of Rrs at 1 Hz to Rrs at 2 and 3 Hz (Rrs1Hz/Rrs2Hz, Rrs1Hz/Rrs3Hz) and of Rrs at 2 Hz to Rrs at 3 Hz (Rrs2Hz/Rrs3Hz). Effect of histamine on frequency dependence was assessed. RESULTS: Correlation with PC65Cdyn was high for PC150Rrs (rs = 0.93) and PC200Rrs (rs = 0.96). Correlation between PC65Cdyn and PC150RL was weakly positive (rs = 0.61). The slope of Rrs over 1 to 3 Hz changed significantly between baseline (-0.07+/-0.09 cm H2O/L/s/Hz) and final histamine dose (-0.28+/-0.10 cm H2O/L/s/Hz). The Rrs1Hz/Rrs3Hz and Rrs2Hz/Rrs3Hz differed significantly (P < 0.05 between baseline [1.27+/-0.36 and 0.96+/-0.11, respectively] and final histamine dose [1.62+/-0.37 and 1.09+/-0.14, respectively]). CONCLUSIONS: Correlation between histamine-induced changes in respiratory mechanics, as measured by FOM and the pneumotachograph-esophageal balloon method, was good. The FOM results indicated frequency dependence of respiratory mechanics during HBP. CLINICAL RELEVANCE: A noninvasive method of measuring airway reactivity will facilitate routine evaluation of horses with suspected small airway disease and may be suitable for field studies.     

Influence of breathing pattern and lung inflation on impulse oscillometry measurements in horses

The objective of this paper was to determine if changes in ventilation patterns could influence the outcome of respiratory function measurements performed with our impulse oscillometry system (IOS) in horses. In a first study, IOS tests were performed in vitro on six isolated equine lungs. Lung inflation levels were controlled by modifying depressurisation inside an artificial thorax and different ventilation patterns were imposed. In a second in vivo study, transient variations in breathing pattern were evaluated both with the IOS and a current reference technique (CRT) in five healthy mature horses after an intravenous (i.v.) injection of lobeline hydrochloride. In both studies, respiratory rate (RR, range: 7-42 breaths/min.) and tidal volume (V(T), range: 0.4-25 L) had minor or no influence on IOS parameters. The influence of lung inflation, most marked for resistance at 5 Hz (R(5 Hz)), was limited for the considered physiological range. In vivo, statistical models indicated that maximal changes in pleural pressure (Max Delta Ppl) and peak flows were the main determinants of the variability of the resistance (R(rs)) and the reactance (X(rs)) of the respiratory system. The fourfold increase in baseline Max Delta Ppl and peak flows obtained during hyperpnoea caused a significant increase in R(rs) at 5 and 10 Hz and a decrease in X(rs) at all frequencies. We conclude that IOS parameters are not influenced by tachypnoea, but will reflect alterations in respiratory mechanics caused by hyperpnoeic breathing.     

Comparison of barometric whole body plethysmography and its derived parameter enhanced pause (PENH) with conventional respiratory mechanics in healthy Beagle dogs

The purpose of the study was to compare barometric whole body plethysmography (BWBP) and its derived parameter, enhanced pause (PENH), with conventional respiratory mechanics measurements. Resistance (RL), dynamic compliance (Cdyn) and pleural pressure changes were measured in six healthy anaesthetised Beagle dogs using a pneumotachograph and oesophageal balloon technique consecutive to BWBP-derived variables. Upper airway airflow limitation was established (1) by a filter or (2) by insertion of a narrow endotracheal tube. Bronchoconstriction was induced by nebulisation of carbachol at increasing concentrations until PENH exceeded 300% baseline. Upper airway narrowing significantly increased resistance (baseline RL 2.0+/-0.3, RL filter 11.8+/-3.2, RL luminal narrowing 21.1+/-2.3cm H(2)O/L/s; P <0.03), whereas PENH did not change significantly (baseline PENH 0.55+/-0.17, PENH filter 0.49+/-0.10; PENH luminal narrowing 0.50+/-0.18; P >0.05). Carbachol-induced bronchoconstriction caused a significant increase in PENH (baseline PENH 0.43+/-0.14, PENH carbachol 2.62+/-2.14; P <0.02) and resistance (baseline RL 2.1+/-0.3, RL carbachol 28.8+/-13.0 cm H2O/L/s; P <0.01), and a pronounced drop in compliance (baseline Cdyn 163.3+/-73.9, Cdyn carbachol 9.7+/-2.9mL/cmH2O; P <0.02). It was concluded that BWBP detects airflow limitation due to bronchoconstriction but not due to upper airway obstruction in healthy dogs. BWBP represents a valid, although not very sensitive screening tool for respiratory function testing.     

Serum antibody response of Castellana sheep to Haemonchus contortus infection and challenge: relationship to abomasal worm burdens

Primary and secondary serum antibody responses to Haemonchus contortus were studied in Castellana sheep. Ten-month-old sheep were infected (200 L3/kg live weight (lw)) and challenged (400 L3/kg lw) or uninfected and equally challenged with H. contortus. Primary infections induced a partially protective response upon challenge, characterized by higher serum protein levels, longer prepatent periods, lower fecal egg counts, and significant reduction in the establishment rate of the parasite and abomasal adult and L4 worm burdens. The resistant status of the infected and challenged sheep was not clearly related either to the serum specific antibody levels (IgG: IgG1, IgG2; IgM; IgA) estimated by ELISA or to immunodetection patterns in the Western blots.     

Evaluation of a combined transcutaneous carbon dioxide pressure and pulse oximetry sensor in adult sheep and dogs

OBJECTIVE: To evaluate a combined transcutaneous carbon dioxide pressure (tcPCO(2)) and pulse oximetry sensor in sheep and dogs. ANIMALS: 13 adult sheep and 11 adult dogs. PROCEDURES: During inhalation anesthesia, for the first 10 minutes following sensor placement, arterial blood gas was analyzed and tcPCO(2) was recorded every 2 minutes. Subsequently, the animals were hyper-, normo-, and hypoventilated. The simultaneously obtained tcPCO(2) and PaCO(2) values were analyzed by use of Bland-Altman statistical analysis. RESULTS: Mean +/- SD overall difference between tcPCO(2) and PaCO(2) 10 minutes after sensor application was 13.3 +/- 8.4 mm Hg in sheep and 8.9 +/- 12 mm Hg in dogs. During hyper-, normo-, and hypoventilation, mean difference (bias) and precision (limits of agreement [bias +/- 2 SD]) between tcPCO(2) and PaCO(2) values were 13.2 +/- 10.4 mm Hg (limits of agreement, -7.1 and 33.5 mm Hg) in sheep and 10.6 +/- 10.5 mm Hg (limits of agreement, -9.9 and 31.2 mm Hg) in dogs, respectively. Changes in PaCO(2) induced by different ventilation settings were detected by the tcPCO(2) sensor with a lag (response) time of 4.9 +/- 3.5 minutes for sheep and 6.2 +/- 3.6 minutes for dogs. CONCLUSIONS AND CLINICAL RELEVANCE: The tcPCO(2) sensor overestimated PaCO(2) in sheep and dogs and followed changes in PaCO(2) with a considerable lag time. The tcPCO(2) sensor might be useful for noninvasive monitoring of changes but cannot be used as a surrogate measure for PaCO(2).     

Pulmonary structure and function in adult dairy cows with an expanded lung field.

Pulmonary function tests were performed on seven adult dairy cows with an expanded lung field (ExLF) and the results were compared to the values from seven cows with normal lung fields. The cows with ExLF had an increased functional residual capacity (FRC) and end-tidal N2 concentration of the final breath of the multiple-breath N2 washout (FETN2,fb), and an abnormal distribution of ventilation. The measurements of ventilation and gas exchange and pulmonary mechanics did not differ between the two groups. Postmortem examination of the lungs of five of the cows in each group indicated the cows with ExLF had a bronchiolitis with varying degrees of goblet cell hyperplasia, epithelial cell hyperplasia and metaplasia, smooth muscle hypertrophy, inflammatory cell infiltrate, vascular thickening, peribronchiolar fibrosis, and a mild overinflation of the lung. A histopathological score, based on the preceding indices and bronchus-associated lymphoid tissue, was correlated with FRC, FETN2,fb, the lung clearance index and pulmonary resistance. There were no correlations between the histopathological score and any of the measures of ventilation and gas exchange.     

Bronchoconstrictive properties of inhaled 8-epi-PGF2alpha in healthy and heaves-susceptible horses

The 8-epi-PGF2alpha is a marker of oxidative stress which is increased in lungs of asthmatic humans and heaves-susceptible horses. 8-Epi-PGF2alpha has also been demonstrated to be an in vitro and in vivo bronchoconstrictor in humans and rodents. We hypothesised that inhaled 8-epi-PGF2alpha was a bronchoconstrictor in healthy and heaves-susceptible horses in clinical remission. The effect on ventilatory mechanics of nebulised 8-epi-PGF2alpha was compared to that of PGF2alpha and U46619, a thromboxane A2 agonist. Pulmonary resistance (R(L)) and dynamic compliance (Cdyn) were assessed in six healthy horses and in six heaves-susceptible horses in clinical remission before (baseline) and immediately after a single inhalation challenge of 1 mg 8-epi-PGF2alpha PGF2alpha, or U46619 and placebo. R(L) and Cdyn were unchanged after inhalation of 8-epi-PGF2alpha in healthy horses. In heaves-susceptible horses, 8-epi-PGF2alpha induced a significant increase of R(L) and a significant decrease of Cdyn when compared to baseline values. Differences between R(L) and Cdyn values after 8-epi-PGF2alpha inhalation and those of placebo inhalation were not significant. Differences with healthy horses were not significant. PGF2alpha and U46619 induced a significant bronchoconstriction in healthy (R(L) and Cdyn versus baseline) and heaves-susceptible horses (R(L) and Cdyn, versus baseline and placebo), the R(L) increase in heaves-susceptible horses after PGF2alpha inhalation was significantly higher than that in healthy horses. Our results suggest that 8-epi-PGF2alpha is not a bronchoconstrictor in healthy horses, and a bronchoconstrictor far less efficient than PGF2alpha and U46619 at the same dose in heaves-susceptible horses.     

Analysis of respiratory mechanics by impulse oscillometry in non-sedated and diazepam-sedated swine

Analysis of respiratory mechanics using impulse oscillometry is applicable to sedated, or non-sedated (trained) pigs when they are fixed in a sling. In this study, the influence of the following sources of variability on measurement results was examined: (i) sedation with diazepam; (ii) body weight of animals (ranging in age: 40 to 102 days); and (iii) time of the measurement (circadian influences). The following parameters were examined: respiratory rate (RR), tidal volume (v(t)), spectral resistance, reactance and coherence, each at 5, 10, 15 and 20 Hz (R5,...R20, X5,...X20, CO5...CO20, respectively), distal respiratory resistance (Rdist), and proximal airway resistance (Rprox). After sedation (using 1.5 mg diazepam per kg body weight), RR and v(t) decreased significantly. There was a significant improvement of CO5, CO10 and CO15. Increase in body weight was strongly correlated to v(t), furthermore to spectral resistance parameters. Impulse oscillometry system (IOS) parameters showed only slight non-significant alterations in dependency on the time of day. In consequence, different sources of variability must be taken into account when performing IOS measurements in swine.