Dual Intracordal Unilateral Vocal Fold Cysts: A Perplexing Diagnostic and Therapeutic Challenge

SUMMARY

A 52-year-old professional voice user, a director of international sales and marketing and sports coach, described a 40-year history of severe hoarseness, with recent progressive dysphonia. He could not be heard on a cell phone and was unable to raise the volume or intensity of his voice. Strobovideolaryngoscopy revealed a perplexing set of dual intracordal lesions in the left vocal fold and a posterior glottal gap. The amplitude and magnitude of the left vocal fold mucosal waves were barely perceptible and were severely decreased in the right. There was marked phase asymmetry and aperiodicity bilaterally. A computed tomography scan of the neck with contrast and multiplanar reformatted reconstructions and a magnetic resonance imaging (MRI) of the neck with and without contrast revealed the nodular appearing masses of the left vocal fold without any definite evidence of paraglottic or supraglottic extension and no cervical lymphadenopathy. He had a hyperfunctional larynx with laryngopharyngeal reflux and chronic reflux laryngitis. Voice restoration required antireflux therapy, voice therapy, and phonomicrosurgical excision of the lesions. One benign epidermoid malformation cyst was lined by squamous epithelium. The second was a retention cyst lined with cuboidal epithelium. Finally, after 40 years, he has a normal voice.

Inhaled Corticosteroids: Hazardous Effects on Voice—An Update

Inhaled corticosteroids (ICS) have become the prevalent treatment in asthmatics. Hazards to voice are under-recognized. A total of 38 patients with voice complaints associated with the use of ICS were assessed by 79 strobovideolaryngoscopy (SVL) examinations, 24 single and 14 multiple SVL. Hoarseness and dysphonia were the primary reasons for referral. The ICS initially used most frequently was Advair Diskus (fluticasone propionate and salmeterol-inhalation powder-[IP]) in 22 patients, followed by Flovent (fluticasone propionate inhalation aerosol-pressurized metered-dose inhaler-[PMDI]) in 11. Duration of ICS usage varied from 2 weeks to 4-5 years. Higher dosage and frequency of use exacerbated problems. Hazards to voice previously unrecognized by real-time indirect mirror or fiberoptic laryngoscopy were identified by meticulous attention to SVL abnormalities. There was essentially no difference in occurrence of abnormalities whether analyzed from the perspective of the initial 38 or all 79 examinations. These included abnormal mucosal wave symmetry/periodicity (76-63%), phase closure (74-63%), glottic closure (63-59%), mucosal wave amplitude/magnitude (50-35%), supraglottic hyperactivity (39-25%), mucosal quality (34-34%), and glottic plane (10-5%). Candidiasis of the larynx was infrequently observed. Fluticasone ICS were a cause of steroid inhaler laryngitis, and the best treatment was their avoidance or cessation. Further prospective studies ideally might include SVL documented as a pretherapy baseline and then repeated in each ICS patient who developed hoarseness/dysphonia.

Effect of burning on the numbers of questing ticks collected by dragging

Sixteen experimental burn plot replicates, in groups of four, in four landscape zones of the Kruger National Park, South Africa, and from which wildlife are not excluded, have been subjected to fixed, regular burning regimens since 1954. In 1999, a study to determine the effect of burning on ixodid ticks questing for hosts from the vegetation of the plots was initiated, and six sub-plots, with identical histories, within each of two of the burn plot replicates in Combretum collinum/Combretum zeyheyri woodland on granite, were selected. With few exceptions these 12 sub-plots, as well as unburned vegetation adjacent to each of the replicates, were sampled for ticks at monthly intervals for a period of 39 months by dragging with flannel strips. The existing regimen of burning during August or during October on individual sub-plots was continued during this time. A total of 14 tick species was recovered from the plots of which nine could be considered major species. Sufficient numbers for statistical analysis of only eight species were, however, collected. Burning appeared to have little short-term effect on the number of ticks recovered. In the longer term, the response varied from no change, an increase, or a decrease in the numbers of ticks collected each year after burning. Tick species, life cycle, seasonality, questing strategy, host preference and host utilization of the habitat were important determinants of the effect of burning.

Vocal Fold Polyp in a Professional Brass/Wind Instrumentalist and Singer

Wind instrumentalists, especially brass players, and singers share common factors, including vocal tract shape, function and pressure, vocal fold opening and closure, breath vector of force and air flow rates. To understand the mechanism and function of the vocal folds with a pathological lesion, it is necessary to visualize the differing interactions of the vocal tract during wind and brass instrument playing and in singing. A school band director, singer, wind and brass instrumentalist, was referred by musician colleagues with intermittent dysphonia, aphonia, and inability to sing high notes. Simultaneous videolaryngoscopy, with and without stroboscopy, and external video examination were documented. An hourglass glottis with a sessile, cystic polyp of the left vocal fold were recorded and studied during phonation and the playing of 3 instruments. The techniques of glottic opening, closure, configuration and function varied with the type of instrument and phonatory function. Singing was adversely affected by the vocal fold polyp but no harmful interaction occurred during wind/brass instrument playing. Down-stream loading in singers is at the laryngeal level and in wind/brass instrumentalists is at the embouchure. Preoperative voice therapy, phonomicrosurgery, and postoperative voice rest followed by voice therapy, succeeded in restoring her combined wind/brass instrumental and singing career.

Parasites of domestic and wild animals in South Africa. XLI. Arthropod parasites of impalas, Aepyceros melampus, in the Kruger National Park

Ectoparasites were collected from impalas, Aepyceros melampus, at four localities within the Kruger National Park, namely Skukuza, in the Biyamiti region, Crocodile Bridge and Pafuri. Animals were also examined at Skukuza during a severe drought and at Skukuza and Pafuri towards the end of a second drought. Parasite burdens were analysed in relation to locality, sex, age class, month and drought. The impalas were infested with 13 ixodid ticks species, including two that were identified only to genus level. Except for four animals at Pafuri, all were infested with Amblyomma hebraeum. The highest intensity of infestation with larvae of this tick occurred from April to June and during November and December at Skukuza and in the Biyamiti region. Infestation with nymphs was highest during late winter. All animals were infested with Boophilus decoloratus, and the intensity of infestation was highest during spring. The intensity of infestation with Rhipicephalus appendiculatus was highest at Crocodile Bridge and at Pafuri, and that of Rhipicephalus zambeziensis at Skukuza. With both the latter species the intensity of infestation of larvae was highest from April to August, of nymphs from July to September or October and of adults during February and March. Rhipicephalus kochi was present only at Pafuri. The impalas also harboured five louse species and two species of hippoboscid flies. The intensity of infestation with lice tended to be greater during late winter and spring than during other seasons and greater on lambs than on yearlings on which it was greater than on adult animals.

Bilateral vocal fold posterior glottic/subglottic stenotic web resected with contact tip Nd-YAG laser

The standard treatment for respiratory failure remains endotracheal intubation, with periods of 22 or more days being commonplace. Posterior glottic stenotic web formation, from scarring in the posterior interarytenoid area, may occur after endotracheal intubation, thermal, corrosive, or direct surgical injury. A commonly used classification system for posterior glottic stenosis divides the occurrence into four types. Type I involves an interarytenoid scar band between the vocal folds that is anterior and separate from the posterior interarytenoid mucosa. Type II stenosis involves scarring of the mucosa or musculature of the posterior interarytenoid area. Types III and IV involve unilateral and bilateral cricoarytenoid joint fixation, respectively. Strobovideolaryngoscopy (SVL), rigid and flexible fiberoptic bronchoscopy, electromyography (EMG), radiologic imaging of the neck, larynx, and trachea as well as pulmonary function tests, including flow volume loops, provide important objective measurements of upper airway obstruction. A representative case of a professional voice user who suffered a Type II posterior glottic stenosis is presented. The treatment utilized a specific contact-tip neodymium-yttrium aluminum garnet (Nd-YAG) laser delivery system to achieve precise cutting, vaporization, and coagulation simultaneously, returning tactile touch technique to the airway/voice surgeon. Completely successful restoration of voice and airway have been maintained for 2 1/2 years postoperatively.

Bilateral mixed laryngoceles: simultaneous strobovideolaryngoscopy and external video examination

A music medicine practice affords a unique opportunity to diagnose and treat laryngeal music performers. Strobovideolaryngoscopic (SVL) and external video examination of the voice professional or brass instrument player may focus on the vocal folds, yet abnormalities of the supraglottis, neck, and thorax should be appreciated and documented. Laryngoceles are uncommon laryngeal disorders but may occur in up to 5% of benign laryngeal lesions. While many laryngoceles are asymptomatic, they may cause a cough, hoarseness, stridor, sore throat, pain, snoring, or globus sensation. In particular, musicians who play brass instruments are at high risk for laryngocele development. We highlight two patients with symptomatic laryngoceles to present anatomical, historical, classification, epidemiological, diagnostic, and management considerations.

Pesticide risk reduction on crops in the Province of Ontario

We analyzed the changes in pesticide use and risk in the Province of Ontario, Canada, from 1973 to 1998 to monitor the success of Food Systems 2002, a program to reduce pesticide use by 50%. Pesticide risk was calculated by multiplying the amount of pesticide used (kilograms of active ingredient) by the Environmental Impact Quotient (EIQ), a score for the potential risk of pesticides to farmworkers, consumers, and the environment. Pesticide use increased by 46% from 1973 to 1983. From 1983, the baseline year for Food Systems 2002, to 1998, pesticide use decreased by 38.5% and risk declined 39.5%. The reductions in pesticide use and risk were primarily on corn (Zea mays L.) and tobacco (Nicotiana tabacum L.), the crops with the highest pesticide use in 1983. Total pesticide use on soybean [Glycine max (L.) Merr.] did not change, but the mean application rate (kg ha(-1)) decreased by 57%. Corn and soybean account for 65% of pesticide use, but have a relatively low pesticide use and risk per hectare and per tonne of production. Total pesticide use on tobacco, fruits, and vegetables was lower than on corn or soybean, but the pesticide use and risk per hectare were much higher. Small reductions in pesticide use on corn and soybean may allow a 50% reduction in pesticide use, but greater reductions in risk can be achieved by reducing the use of "high risk" pesticides on fruit and vegetables.

PVCM, PVCD, EPL, and irritable larynx syndrome: what are we talking about and how do we treat it?

Paroxysmal vocal cord movement/motion (PVCM), paroxysmal vocal cord dysfunction (PVCD), episodic paroxysmal laryngospasm (EPL), and irritable larynx syndrome (ILS) are terms used to describe laryngeal dysfunction masquerading as asthma, upper airway obstruction, or functional and organic voice disorders. The differential diagnosis of PVCM, PVCD, EPL, and ILS is critical to successful medical and behavioral management of the patient. During the past 10 years, 27 subjects, ages 15-79 years, were identified to have paroxysms of inspiratory stridor, acute respiratory distress, associated aphonia and dysphonia, resulting in misdiagnosis and unnecessary emergency treatments, including endotracheal intubation, cardiopulmonary resuscitation, massive pharmacotherapy, or tracheostomy. A multifactorial management program is proposed utilizing principles of motor learning, neurolinguistic programming model, respiratory and phonatory synchronization, relaxation techniques, concurrent monitoring of behavioral adjustments, and formal psychological counseling.

Serologic survey for antibodies to Borrelia burgdorferi in white-tailed deer in Ontario

Serum samples collected from 623 white-tailed deer (Odocoileus virginianus) in southern Ontario (Canada) from 1985 to 1989 were tested for antibodies to Borrelia burgdorferi using an indirect fluorescent antibody (IFA) staining method. Samples from 150 of the deer were also tested using an enzyme-linked immunosorbent assay (ELISA). At IFA titers of 1:64 and 1:128 deer with antibodies to B. burgdorferi appeared to be widespread throughout southern Ontario, with an apparent prevalence ranging from 3 to 47%. At IFA titres > or = 1:256 and ELISA titres > or = 1:160 deer with antibodies to B. burgdorferi were only present on Long Point which is the only known endemic focus of Ixodes scapularis, the primary vector for B. burgdorferi, in southern Ontario. At these titres the apparent prevalence of antibodies to B. burgdorferi on Long Point was only 5 to 7%, even though the mean intensity of infestation of adult I. scapularis on deer was > 180, and 60% of the adult ticks are infected with B. burgdorferi. Based on these results, white-tailed deer do not appear to be a good sentinel species for the distribution of B. burgdorferi.

Laser bronchoscopy with transglottic/supraglottic ventilation to relieve dysphonia and subglottic obstruction

Dysphonia after endotracheal intubation usually indicates a glottic lesion but it can also herald an obstructing subglottic airway mass. Outpatient strobovideolaryngoscopy may be anatomically extended by transglottic videotracheobronchoscopy to achieve a thorough examination of the proximal bronchi, trachea, subglottis, glottis, and supraglottis in selected cases. Combining these techniques with lateral soft tissue x-ray studies of the neck in two patients with dysphonia and stridor, nearly identical postendotracheal intubation subglottic severely obstructing granulation "tumors" were diagnosed. Operative subglottic resection with a rigid ventilating laser bronchoscope combined with transglottic/supraglottic anesthetic ventilation techniques and contact-tip Nd-YAG laser phototherapy relieved the dysphonia and airway obstruction simultaneously. Normal vocal quality and full anatomical airway patency were achieved in both cases. Follow-up postoperative vocal rehabilitation and medical therapy sustained the surgical results.

Evaluation of the efficacy of 3% citronella candles and 5% citronella incense for protection against field populations of Aedes mosquitoes

We assessed the efficacy of 3% citronella candles and 5% citronella incense in protecting subjects from bites of Aedes spp. under field conditions. The study was conducted in a deciduous woodlot in Guelph, Ontario, Canada from July 26 to August 10, 1995. Eight subjects, dressed identically, were assigned to one of 8 positions on a grid within the study area. Two citronella candles, 2 citronella incense, 2 plain unscented candles, or no candles (i.e., nontreated controls) were assigned to 2 positions on the grid each evening. Subjects conducted 5-min biting counts at each position and performed 16 biting counts per evening. On average, subjects received 6.2 +/- 0.4, 8.2 +/- 0.5, 8.2 +/- 0.4, and 10.8 +/- 0.5 bites/ 5 min at positions with citronella candles, citronella incense, plain candles, and no candles, respectively. Although significantly fewer bites were received by subjects at positions with citronella candles and incense than at nontreated locations, the overall reduction in bites provided by the citronella candles and incense was only 42.3 and 24.2%, respectively.

Episodic paroxysmal laryngospasm: voice and pulmonary function assessment and management

Episodic paroxysmal laryngospasm (EPL) is a sign of laryngeal dysfunction, often without a specific organic etiology, which can masquerade as asthma, vocal fold paralysis, or a functional voice disorder. The intermittent respiratory distress of EPL may precipitate an apparent upper airway obstructive emergency, resulting in unnecessary endotracheal intubation, cardiopulmonary resuscitation, or tracheostomy. During 27 months, seven women and three men, age 30-76 years, were assessed by a high diagnostic index of suspicion, an intensive history including psychosocial factors, physical examination of the airways, provocative asthma testing, and swallowing studies. Videolaryngoscopy, stroboscopy, and pulmonary flow-volume loop testing were definitive. The classic appearance was paradoxic inspiratory adduction of the anterior vocal folds with a posterior diamond-shaped glottic gap. During an attack of stridor or wheezing, attenuation of the inspiratory flow rate as depicted by the flow-volume loop suggested partial extrathoracic upper airway obstruction. Swallowing evaluation by videolaryngoscopy and videosophagography may uncover gastroesophageal reflux disease. Hallmarks of management include patient and family education by observation of laryngoscopic videos, a specific speech therapy program, psychotherapy, and medical treatment of associated disorders. Electromyography may become a valuable future adjunct. Unlike laryngeal dystonia, patients with EPL do not benefit from botulinum toxin type A.

Prevalence of hepatic helminths and associated pathology in impala (Aepyceros melampus) in Swaziland

The livers of impala (Aepyceros melampus) collected in the Mlawula-Mbuluzi-Simunye Nature Reserve and Protected Area complex in northeastern Swaziland from October 1985 to September 1986 were infected with three species of helminths: a nematode (Cooperioides hepaticae), a cestode (Stilesia hepatica), and a trematode (Fasciola gigantica). Cooperioides hepaticae caused a severe cholangitis. Lambs were infected at 1.5 to 2 mo of age, and the prevalence increased to 100% by 5 mo of age. The prevalence was 82% in yearlings and 44% in adults, with the highest prevalence and intensity of infection at the end of the dry season. Stilesia hepatica was found primarily in adults. Heavy infections caused a thickening and distension of the main bile ducts, but no changes were evident in the liver parenchyma. Fasciola gigantica, found only in one adult male, caused a thickening and distension of main bile duct. There was no apparent association between the helminth infections and body condition.

Laryngotracheal paratubal air envelope: a useful sign in voice and airway reconstructive surgery

Aphonia, dysphonia, and laryngotracheal stenosis with upper airway compromise are diagnosed with increasing frequency. Endoscopic surgical reconstructive techniques accompanied by tracheal T-tube stenting successfully restore voice, airway function, and structure. Timing of tracheal T-tube removal remains controversial, particularly when the tip of the upper arm of the optimally sized T-tube is placed in a critical supraglottic position. The appearance of an air envelope, manifested as linear air densities between the outside wall of the T tube and the inside wall of the larynx and trachea, has proven to be a useful and reliable indicator of laryngotracheal structural integrity and functional stability. The paratubal air envelope sign is demonstrated by soft-tissue neck radiographs and delta scan topograms. This objective sign, videolaryngoscopy/stroboscopy, and clinical judgment combine to determine optimal timing for tracheal T-tube removal.

Clinical, biochemical, and hematologic evaluation of normal dogs after administration of rabbit anti-dog thymocyte serum

Renal allografting is the only long-term alternative to euthanasia in dogs with end-stage kidney disease. The purpose of this study was to determine the clinical, biochemical, and hematologic effects of rabbit anti-dog thymocyte serum (RADTS) in normal dogs and to develop a safe and practical route of administration before its use in an allograft immunosuppressive protocol. Thirteen mongrel dogs were divided into three groups; each received RADTS subcutaneously, intramuscularly, or intravenously. The inflammation and pain associated with subcutaneous administration was unacceptable. A significant (p < or = .05) leukopenia and lymphopenia developed in all dogs, regardless of the route of administration of RADTS. Thrombocytopenia was a consistent finding after intravenous administration and with high doses given intramuscularly. Both the intravenous and intramuscular routes were well tolerated by all dogs with minimal or no discomfort. Serum creatinine was unchanged, whereas serum alanine aminotransferase activity increased in one dog. There were no histologic changes in any of the kidneys examined.

Sarcoidosis of the larynx: preserving and restoring airway and professional voice

Professional voice users may present with disastrous dysponia and life-threatening upper airway disturbances due to a rare condition. Two teachers demonstrated extrathoracic obstructive laryngeal lesions by videolaryngoscopy and pulmonary function flow-volume loops. A characteristic "honking" voice and edematous, pink, diffuse turban-like enlargement of the supraglottic structures are considered pathognomonic of laryngeal sarcoidosis. Diagnosis was confirmed by biopsies, and clinical and radiologic findings. Sarcoidosis is a variable, disseminated disease involving many body organs, self-limited or progressive, with frequent exacerbations and remissions, affecting the larynx in 0.5-1.4% of patients. Spinal cord involvement demonstrated by new magnetic resonance imaging techniques can be heralded by voice changes detected in professional voice users. Systemic corticosteroid therapy combined with intralesional steroid injections and microendoscopic surgery, with or without tracheostomy, preserved and restored both professional voice and airway.

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.

An evaluation of the multiple-breath nitrogen washout as a pulmonary function test in horses

Multiple-breath nitrogen washouts (MBNW) were performed with 29 light horses. Seven normal horses were used to examine the reproducibility, and 22, ranging from normal to severely diseased, were used to examine the changes in chronic obstructive pulmonary disease (COPD) and the effect of a bronchodilator, salbutamol, on the distribution of ventilation. The MBNW were analyzed using the functional residual capacity (FRC), end-tidal N2 concentration of the final breath of the MBNW (FETN2,fb), end-tidal N2 concentration when the cumulative expired volume was equal to body weight (FETN2,bw), lung clearance index (LCI), Becklake index (BI), mixing ratio (MR), index of distribution of inspiration (IDI), pulmonary N2 clearance delay (PCD) and ventilatory efficiency (EFF). The LCI, MR, IDI, PCD and EFF were calculated at end-tidal N2 concentrations (FETN2), equal to 3%, 2% and FETN2,fb. The EFF was also calculated at FETN2 = 8%, as was BI. The within day coefficient of variation for most indices of the MBNW was 10-15%. None of the indices varied significantly from day-to-day. The FETN2,fb, FETN2,bw, MR, IDI, PCD, and EFFfb, EFF3% and EFF2% differed between the horses with COPD and the normal horses, and all of the indices, except FRC, were correlated with a histopathological score of the small airways. The FETN2,bw appeared to be the most sensitive index in detecting the horses with COPD. In the horses with COPD, salbutamol caused a decrease in FRC and FETN2,fb indicating increased ventilation of the lung. However, LCI increased suggesting a less efficient distribution of ventilation.

Comparative ventilation and gas exchange in the horse and the cow

Ventilation and gas exchange were studied in healthy, adult horses and cows, two large species with different lung structures and different breathing patterns. The oxygen uptake (VO2), carbon dioxide output (VCO2), respiratory rate (fR), minute ventilation (VE), alveolar ventilation (VA), alveolar oxygen pressure (PAO2), and VE/VO2 ratio were higher in the cows, while the tidal volume (VT) and physiological dead space (VD) were larger in the horses. The arterial blood gases, alveolar-arterial oxygen pressure difference (PAO2-PaO2) and VD/VT ratio did not differ between the two species. The higher VO2 in the cows was most likely due to the energy cost of standing, and possibly to a higher cost of digestion. The higher VE, VA, VE/VO2 and PAO2 were most likely secondary to the increased VO2 and the slightly higher respiratory exchange ratio (R) in the cows. In contrast to hypotheses based on allometric equations, the PAO2 of horses and cows did not appear to differ from that of smaller mammals. The VD was larger than that predicted from allometric equations, and even though the VD/VT ratio (0.50) was lower than the previously reported values for horses and cows, it was significantly larger than the predicted weight-independent value of 0.36. Re-examination of the data used to derive the equation for VD raised questions as to the validity of this equation, and it is suggested that caution be exercised in the use of allometric equations for prediction.

Comparative pulmonary mechanics in the horse and the cow

Pulmonary mechanics and lung volumes were measured in horses and cows to determine if differences in breathing pattern between the two species were due to differences in the mechanical properties of the lungs. Tidal volume (VT) was larger in the horses, while the respiratory rate (fR) and minute ventilation (VE) were higher in the cows. The horses often had a double peak in airflow during inspiration and, or, expiration, while the cows had a single peak during expiration. Measured lung volumes were larger in the horses and they had a higher dynamic lung compliance (Cdyn,L), although the static compliance of the lung, chest wall and respiratory system (Cst,L,Cst,w and Cst,rs respectively) did not appear to differ between the two species. The cows had a greater change in maximum transpulmonary pressure (delta PLmax) and an increased nonelastic work of breathing (Wb). However, the pulmonary resistance (RL) did not differ between the two species, thus the higher delta PLmax and Wb in the cows were most likely a function of their higher flow rates. Calculations of the rate of work of breathing (W) indicate that both species breathed at an fR above the minimum W. The fR in the horses was close to the fR predicted for the average minimum muscle force, but the fR in the cows was higher. As the differences in the mechanical properties of the lung do not explain the differences in flow pattern, nor adequately account for the higher fR in the cows, it is suggested that the differences in breathing pattern between the two species is due to differences in the chest wall, particularly the size and shape of the abdomen.

Simple nonrebreathing valves for use with large mammals

Two simple nonrebreathing valves suitable for use with large mammals are described. These valves can be constructed in a reasonably well equipped workshop using materials that are readily available. The resistive pressure of both valves is less than 0.1 kPa at flow rates up to 15 L.s-1. Their main limitation is a relatively large dead space, although the dead space of valve B (290 mL) is less than the dead space of some commercially available valves. Healthy adult horses and cows compensate for the increased dead space by an increase in tidal volume.

An evaluation of the multiple-breath nitrogen washout as a pulmonary function test in dairy cattle

Multiple-breath nitrogen washouts (MBNW) were performed with 21 adult dairy cows (seven normal cows tested on two days each, four clinically normal cows tested on six days, and ten cows with respiratory disease tested on one day each). The functional residual capacity (FRC), lung clearance index (LCI), Becklake index (BI), mixing ratio (MR), pulmonary N2 clearance delay (PCD), index of distribution of inspiration (IDI) and ventilatory efficiency (EFF) were calculated for each MBNW. The LCI, MR, PCD, IDI and EFF were calculated at an end-tidal N2 concentration of 3% (FETN2,3%) and the end-tidal N2 concentration of the final breath of the MBNW (FETN2,fb), while BI was calculated and EFF was also calculated at FETN2 = 8% (i.e. after washout of 90% of the N2 in the lung). All of the MBNW were irregular due to breath-to-breath variability in the breathing pattern of cows and variability in FRC. The within day coefficients of variation for FRC, LCI, MR, IDI, EFF3% and EFFfb were less than 10%, but in the four cows tested on six days there was significant day-to-day variability for individuals for FRC, LCI, BI, MR, PCD and IDI. The shape of the MBNW curves differed between the normal cows and those with respiratory disease. The FRC, EFF3% and EFFfb were the most sensitive indices in detecting the cows with respiratory disease, and when EFF3%, EFFfb or FETN2fb, was used in conjunction with FRC it was possible to detect all of the cows with respiratory disease.

Observations on the lungworm, Pneumostrongylus calcaratus, in impala (Aepyceros melampus) from Swaziland

The lungworm, Pneumostrongylus calcaratus, was found in 85% (164 of 193) of impala (Aepyceros melampus) collected in Mlawula Nature Reserve in Swaziland. Infection was confirmed at 4.5 mo of age, and the prevalence increased to 100% at 11 mo, with a prevalence of 98% in animals greater than 1 yr of age. Pneumostrongylus calcaratus was usually found in firm, tangrey nodules along the lobar borders of the lungs, although an extensive granulomatous pneumonia with miliary caseous abscesses and calcified nodules was observed in some older animals. In the primary infection in lambs, adult parasites, larvae and eggs were observed in the alveoli and bronchioles within the nodule. There was peribronchial and perivascular mononuclear cuffing, with infiltration of mononuclear cells in the alveolar septum in the vicinity of worms. In lesions in older animals, there was local consolidation with macrophages and giant cells, and foci of parenchymal necrosis associated with degenerating eosinophils, which appeared to lead to the formation of eosinophilic granulomas. Resolving lesions caused interstitial fibrosis, with mineralized nodules. Pneumostrongylosis does not appear to pose a significant threat to the health of impala in Swaziland.

Reproducibility of pulmonary mechanics measurements in dairy cattle

The reproducibility of pulmonary mechanics measurements in dairy cattle was examined using two study designs. In design A measurements were made with six cows on two days, and in design B measurements were made with four cows on six days. The mean coefficients of variation for within-day measurements for individuals ranged from 9.2 to 25.9% indicating considerable within-day variability. In design A there were no significant differences between days (P less than 0.05) for any measured variable for the group, but there were often significant differences between the two days for individuals. In design B there were significant cow-day interactions for all variables, again indicating significant differences between days for individuals. There were significant differences between days for the group for respiratory rate, and duration of inspiration and expiration. Both the interactions and differences between days appeared to be random. The high variability and limited reproducibility of pulmonary mechanics measurements, particularly in individual animals, indicate the need for caution in the interpretation of pulmonary mechanics measurements in dairy cattle.

Heart rates and gas exchange in the Amazonian manatee (Trichechus inunguis) in relation to diving

Unrestrained Amazonian manatees (Trichechus inunguis) maintained a constant heart rate during diving and exhibited a slight tachycardia during breathing. 'Forcing' the manatees to dive caused a marked bradycardia. They exhibited a more pronounced tachycardia during breathing after 'forced' dives and hyperventilated during recovery dives. Manatees are capable of dives exceeding 10 min duration without having to resport to anaerobic metabolism, and even after 10 min dives recover within 3-4 short dives. The ability of manatees to make long dives, in spite of relatively poor O2 stores, is due to their low metabolic rate, while the rapid recovery is aided by their high CO2 stores which minimizes CO2 storage in the body. In manatees the changes in alveolar O2 and CO2 pressure (PAO2 and PACO2) in relation to dive time are slower and more variable than in other marine mammals. The lower rate of change is probably due to the manatees' reduced metabolic rate, while the greater variability is due to their breathing pattern, in which both ventilation and body gas stores influence alveolar gases.

Temperature regulation in freely diving harp seals (Phoca groenlandica)

Measurements were made of the relation between body temperature, respiration, diving pattern, and water temperature using three adult harp seals (Phoca groenlandica). Core temperature, ventilation, gas exchange, and diving pattern were not affected by water temperature ranging from 1.8 to 28.2 °C. The basal metabolic rate of the seals in this study was not significantly different than that predicted for terrestrial mammals of equivalent size. Expired heat loss and convective heat loss from the body accounted for 16% of the heat loss and were independent of water temperature. The remaining 84% of the heat was lost from the flippers which accounted for less than 14% of the surface area. Calculations of the ratio of convective heat transfer coefficients of the blubber layer indicate that internal conduction rather than external convection governed heat loss.