A prospective study of infections with atypical pneumonia organisms in acute exacerbations of chronic bronchitis.

The objective of this paper was to study the incidence of 6 atypical pneumonia pathogens or atypical organisms in local patients admitted for acute exacerbation of chronic bronchitis. This is a prospective observational study. Over a period of 3 years (1995 to 1997), 90 patients admitted to a large general hospital in Singapore for acute exacerbation of chronic bronchitis were tested for the following infections: Legionella, Mycoplasma, Chlamydia, influenza A, influenza B and parainfluenza viruses, using paired serological examination. The antibiotic prescribing pattern by the attending physicians in these cases were also examined. Positive serologies were found in 31 patients (34%), of whom 26 patients (28%) had viral infections. The most common organism was influenza A with 18 positive serologies (20%). Five patients were tested positive for Legionella. There was no evidence of acute infections by Mycoplasma pneumoniae or chlamydia using serological tests.

The obstructive sleep apnoea syndrome--experience of a referral centre.

OBJECTIVE: The aims of this study were: (i) to document the presence and severity of obstructive sleep apnoea (OSA) in patients who complained of heavy snoring and other symptoms suggestive of the OSA syndrome; (ii) to examine the correlation between the clinical and polygraphic findings, and (iii) to document the efficacy and compliance of nasal continuous positive airway pressure (CPAP) among these Asian snorers with OSA. METHODS: We analysed our clinical and nocturnal polysomnographic data between January 1986 and December 1995 for physician-referred patients who had complained of snoring and other symptoms suggestive of OSA. RESULTS: A total of 277 diagnostic studies were performed of which 145 (52%) were positive to OSA. For studies performed in the last 2 years (n = 125), 72 of the 125 were positive for OSA. Anthropometric data was not discriminative between the OSA positive snorers and the OSA negative snorers. We found that hypertension and choking were the most significantly related to OSA, conferring a 7 and 4 times relative risk respectively. Nasal CPAP eliminated snoring, apnoeas and oxygen desaturations completely in almost all cases and there were only minor mask-related side effects. CONCLUSION: OSA may not be uncommon among Asian snorers. Of the major traits for OSA risk among our local population, a history of hypertension and reports of nocturnal choking were the most significantly related. We have also shown that nasal CPAP is safe and effective among our local snorers and should be considered a first-line treatment for OSA.

Transdiaphragmatic pressure in young adult Singaporean subjects--normal values and a comparison between different respiratory manoeuvres.

BACKGROUND: Most published normal values for transdiaphragmatic pressure (Pdi) have been from Caucasian subjects and there is no universal agreement regarding the most appropriate manoeuvre for assessing Pdi. AIMS: The aims of our study were to obtain normal values and to compare the different manoeuvres used to assess Pdi in normal young Singaporean adults. METHODS: Twenty-four normal subjects (23 Chinese, one Indian) were studied by measuring Pdi during maximal sniffs from functional residual capacity (sniff Pdi), maximal inspiration to total lung capacity (Pdi TLC) and maximal static inspiratory efforts from residual volume (Pdi PImax). RESULTS: Mean values +/- SD for sniff Pdi, Pdi TLC and Pdi PImax were 101.8 +/- 31.7, 46.8 +/- 26.4 and 83.5 +/- 35.5 cm H2O respectively. Sniff Pdi was significantly higher than Pdi TLC (p < 0.001) and Pdi PImax (p = 0.005). Pdi PImax was significantly higher than Pdi TLC (p < 0.001). Males had significantly higher values for sniff Pdi (p = 0.026) and Pdi PImax (p = 0.022) than females. There was a significant correlation between the different methods of recording Pdi. Sniff Pdi had the highest values, least between- and within-subject variation and most consistent pattern of respiratory muscle recruitment with the lowest proportion of negative gastric pressure (Pg) values (p < 0.001). CONCLUSIONS: Therefore, sniff Pdi may be better than Pdi TLC and Pdi PImax in assessing diaphragm function. Also, our subjects seemed to have lower sniff Pdi and Pdi PImax, and higher Pdi TLC compared with Caucasian subjects.

Lung elastic recoil in normal young adult Chinese compared with Caucasians.

Chinese people have smaller total lung capacity (TLC) compared with Caucasians of similar age, sex and height. One possible reason would be a higher lung elastic recoil in Chinese. Most published values for lung elastic recoil viz static lung compliance (CLst), shape constant K, and maximal static transpulmonary pressure (PLmax) have been from Caucasian subjects. The aim of our study was to obtain values for lung elastic recoil in normal young adult Chinese subjects. Static expiratory pressure-volume (P-V) curves were studied in 22 healthy Chinese subjects (12 males and 10 females). The P-V curve was fitted using an iterative least mean squares regression on a computer, according to an exponential equation: V = A-Be-KP, where V is lung volume, P is transpulmonary pressure, and A, B and K are constants. Mean values +/- SD for K, CLst and PLmax were 0.12 +/- 0.04, 230 +/- 103 ml.cmH2O-1 and 27.5 +/- 7.5 cmH2O, respectively. The values of CLst and K were similar to that of normal Caucasian subjects, whereas values of PLmax were lower. We attributed the lower PLmax partly to weaker inspiratory muscles in Chinese compared with Caucasians. We conclude that lung elastic recoil in normal young adult Chinese is similar to that of healthy young adult Caucasians. Hence, lung elasticity is unlikely to explain the racial differences in static lung volumes.

Asthma in chemical workers exposed to aliphatic polyamines.

Following the identification of an index case of occupational asthma, we assessed the respiratory morbidity in 12 workers exposed to aliphatic polyamines in a chemical factory and in 60 unexposed workers in three other workplaces. Many amine workers reported symptoms of chronic cough (7/12), chronic phlegm (9/12), wheezing (4/12) and exertional breathlessness (3/12). These were significantly more frequent in exposed than in unexposed workers (P < 0.01). They also had significantly greater diurnal variation in peak expiratory flow rates (DV-PEFR) than the unexposed workers (P < 0.01). All four amine workers with wheezing reported onset of symptoms after employment at the factory, and all had DV-PEFR greater than 15%, compared to only one control worker (P < 0.01). A second case of occupational asthma was confirmed by bronchial challenge test. The study indicated a very high risk of asthma and chronic airways disease and a need for stringent measures to protect the health of industrial workers exposed to aliphatic amines in Singapore.

Case of occupational asthma due to glue containing cyanoacrylate.

Cyanoacrylates are a rare cause of occupational asthma, there being only six cases reported previously. High humidity has been implicated to be protective in the pathogenesis of the asthma. This is a case report of occupational asthma due to cyanoacrylate glue after working three years in a factory manufacturing doors. Diagnosis was made by history, serial peak flow measurements on and off work and specific inhalation challenge which elicited a delayed bronchoconstrictive response. An unusual feature of this case was the positive reaction to cyanoacrylate despite the high ambient humidity in Singapore.

Mechanisms of apnea termination in obstructive sleep apnea. Role of chemoreceptor and mechanoreceptor stimuli.

Previous work from our laboratory has indicated that mechanoreceptor feedback from the respiratory muscles may play an important role in arousal and apnea termination in obstructive sleep apnea (OSA). Other studies have pointed to a prominent role for chemoreceptor stimuli. We postulated that mechanoreceptor stimuli from the respiratory system are the primary determinant of apnea termination, and that chemoreceptor stimuli exert their effect indirectly through stimulation of ventilation and thus proprioceptive feedback. To test this, we measured the diaphragmatic tension-time index (TTdi) during obstructive sleep apneas in seven male subjects with severe untreated OSA. We compared the maximal TTdi values at end-apnea during administration of air, O2, and CO2. We reasoned that if mechanoreceptor stimuli mediate apnea termination, changing the degree of chemoreceptor stimulation during apneas should not alter the level of respiratory effort at end-apnea. O2 administration produced a significant increase in end-apneic arterial oxygen saturation (SaO2) and increased apnea duration. CO2 administration led to an increase in pre- and postapneic end-tidal carbon dioxide pressure (PETCO2), and tended to shorten apneas. However, the mean value for maximal end-apneic TTdi was 0.12 +/- 0.01 (SEM) during room air breathing and was unaltered by O2 (0.12 +/- 0.01) or CO2 (0.11 +/- 0.01) administration. The consistency of end-apneic TTdi values despite the varying chemical drive supports the hypothesis that apnea termination in OSA is mediated by mechanoreceptor feedback from the respiratory system, most likely from the respiratory muscles. The influence of chemoreceptor information may be mediated indirectly through an effect on ventilatory effort.

Burnisher's asthma--a case due to ammonia from silverware polishing.

A 39-year-old man with no past or family history of asthma developed asthmatic symptoms five months after working as a burnisher in a hotel. He polished brass or silverware using "brasso" or "silvo" respectively. He noticed symptoms only when using "silvo". Specific bronchial provocation testing (BPT) to "brasso" was negative. Specific BPT to "silvo" produced a dual asthmatic reaction. Ammonia was present in both polishes. The ammonia-in-air levels during polishing was 8-15 ppm with "silvo" and less than 1 ppm with "brasso". A specific BPT to 12 ppm of ammonia produced an immediate asthmatic reaction. Our opinion is that he had occupational asthma from the ammonia liberated while polishing silverware with "silvo". Ammonia has been reported to cause asthma. However, there have been no previous reports of occupational asthma among burnishers doing silver polishing.

The effect of oral midazolam and diazepam on respiration in normal subjects.

Benzodiazepine have been shown to suppress ventilatory responses to hyperoxic hypercapnia (HCVR) and isocapnic HVR when taken parenterally. Most patients would, however, prefer to take an oral rather than parenteral preparation but the effect of oral benzodiazepine on these ventilatory responses has not been well studied. We therefore studied the effect of oral midazolam (7.5 mg) and diazepam (5 mg) both given orally on resting ventilation and respiratory drive, as assessed by HCVR and HVR. Flumazenil, a specific benzodiazepine antagonist, was administered intravenously to reverse the effect. A mental alertness-drowsiness index in five grades, from 1 (awake and alert) to 5 (asleep), was used to assess the sedation effect. Six normal male subjects, (aged 31 +/- 1.6 yrs) (mean +/- SD), participated in the study. Mean resting ventilation, and ventilatory response to HCVR and HVR were not significantly altered by these drugs when taken orally. Flumazenil also had not significant effect on HCVR and HVR. However the mental alertness-drowsiness index rose from 1 to 2.83 with oral midazolam and reversed to 1.25 with flumazenil. Similarly, this index increased from 1 to 2.25 after oral diazepam and reversed to 1.42 after flumazenil. In conclusion, we found that even though oral midazolam and diazepam produced a significant sedation effect, which was reversed with flumazenil, the drugs had no effect on ventilation at rest and the ventilatory responses to hypoxia and hypercapnia.

Occupational asthma in Singapore--a review of cases from 1983 to 1990.

One of the newer occupational diseases in Singapore is occupational asthma. As on 31 December 1990 there were 35 confirmed cases of occupational asthma in the official statistics on occupational disease. We report in this paper our observations and experience based on these cases. The problem of under-reporting and the importance of early diagnosis are discussed.

Pulmonary denervation in humans. Effects on dyspnea and ventilatory pattern during exercise.

The role of the pulmonary autonomic nerves in the mediation of respiratory sensation is unclear. Pulmonary neurogenic mechanisms may contribute to dyspnea either directly or indirectly via an influence on the pattern of ventilation. Using human heart-lung transplantation as a model of pulmonary denervation, we studied the ventilatory response, respiratory drive (P0.1), and sensation of breathlessness (modified Borg scale) during maximal incremental bicycle exercise. The subjects were four female heart-lung transplant recipients 3 to 9 months post-transplant and 10 age-matched control subjects. The ventilatory response to increasing CO2 output (VCO2) was higher (p less than 0.001) in transplant recipients than in control subjects, such that ventilation at peak exercise was similar in the two groups despite a lower peak VCO2 in transplant recipients. The ratio of tidal volume to inspiratory capacity increased with increasing ventilation in a similar fashion in both groups. Although the respiratory rate increased more quickly in transplant recipients, it was similar at peak ventilation in the two groups. Ventilatory timing and duty cycle at half-peak and peak ventilation were similar in transplant recipients and control subjects. Dyspnea ratings were not different between the two groups at similar levels of ventilation. Dyspnea as a function of P0.1 was also similar in transplant and control groups. These results indicate that pulmonary neurogenic mechanisms play a role in determining the level, but not the pattern, of ventilation during exercise. Furthermore, these pathways do not appear to contribute significantly to the perception of breathlessness in normal humans.

Sleep apnoea syndrome--a report of 14 cases.

Patients with sleep apnoea syndrome suffer considerable morbidity and an increased mortality. We reviewed the characteristics of 14 patients with sleep apnoea syndrome (11 males and 3 females) who were studied since 1986. All were less than or equal to 60 years of age with the majority in their 4th and 5th decade. Obesity was present in 8 patients (57%) and hypertension in 6 (43%). Overnight sleep studies showed that 11 patients had obstructive sleep apnoea, 2 had central and one had predominantly mixed sleep apnoea. Ten patients (71%) had some form of nose and/or throat pathology. Tonsillectomy seemed an effective therapeutic procedure in those with upper airway obstruction due to enlarged tonsils. Four out of 5 patients had significant symptomatic improvement post-tonsillectomy. Nasal continuous positive airway pressure was also effective in alleviating apnoeas and relieving symptoms in 4 other patients who had no obvious upper airway obstruction. A high proportion of our patients had obstructive sleep apnoea due to enlarged tonsils. Tonsillectomy offered a simple and effective therapy for such patients. Nasal continuous positive airway pressure was also effective in the treatment of obstructive sleep apnoea.

Cardiac arrhythmias during exercise in severe chronic obstructive pulmonary disease.

We studied the effect of maximal exercise on the prevalence of arrhythmias in 122 subjects with severe COPD. At rest, ten subjects had supraventricular arrhythmias while 13 had unifocal VPB greater than or equal to 6/min or ventricular bigeminy. At peak exercise, six subjects had supraventricular arrhythmias while 24 had VAs. Univariate and multivariate analysis with logistic regression did not show relationships between exercise-related cardiac arrhythmias and the severity of pulmonary disease, oxyhemoglobin desaturation or ECG evidence of chronic lung disease. Exercise-related arrhythmias were significantly associated with the presence of arrhythmias at rest and 87 percent of subjects who had no arrhythmias at rest did not have any during exercise. In patients with COPD, the development of potentially serious arrhythmias during exercise is uncommon without clinically apparent CAD or arrhythmias at rest. However, routine cardiac monitoring during exercise testing should not be abandoned in this population since VAs can occur despite their absence at rest.

Carcinoma of the lung with metastases to skeletal muscles.

A prominent feature of the natural history of carcinoma of the lung is that it invariably metastasizes to other organs. The well-known sites include lymph nodes, liver, adrenals, bones and brain. Spread is mainly by lymphatic and haematogenous routes, or by direct extension. However, like many other primary malignancies, the spread of carcinoma of the lung to skeletal muscles is rare. This is despite its bulk and abundant blood supply. Why this is so is unknown. A search of the literature revealed only 3 published case reports of carcinoma of the lung spreading to skeletal muscles. In this paper, we report a case of squamous cell carcinoma of the lung with multiple metastases to skeletal muscles.

Aeromonas endocarditis in a patient with chronic hepatitis-B infection.

Aeromonas, a genus of gram-negative bacteria normally found in water and soil, is well established as a pathogen in the animal kingdom. Often considered as a pathogen of low virulence, its role in human infections has recently been recognised. Aeromonas infections in humans range from cellulitis to septicaemia. Endocarditis is rare. We describe here a patient with a chronic liver disease with aeromonas bacteremia and endocarditis.