A comparison of respiratory function in Afro-Caribbean and Caucasian infants

Race is recognized as an important determinant of lung function in children and adults, but limited data exist for infants. Accurate interpretation of lung function tests during the neonatal period may depend on appropriate values for predicting normality. The aim of this study was to compare tidal breathing parameters, Hering-Breuer reflex (HBR) activity, and total respiratory compliance (Crs) in healthy newborn caucasian (white) and Afro-Caribbean (black) infants, to determine whether separate reference values were required for these two ethnic groups. Respiratory function was measured in 33 healthy black infants, 18 of whom were premature, and 33 healthy white infants matched for sex, gestational age, weight, postnatal age, and maternal smoking during pregnancy. There were no significant paired differences between black and white infants with respect to minute ventilation, respiratory frequency, the ratio of time to reach peak expiatory flow to total expiratory time, or HBR activity. Values of Crs were similar in black and white full-term infants (37.5 (SD 9.0) versus 35.0 (6.3) ml.kPa-1, respectively) suggesting that, in the immediate newborn period, separate reference values are not necessary for these parameters. However, Crs was somewhat lower in black than white preterm infants (26.0(5.2) ml.kPa-1, this difference reaching statistical significance if results were expressed in relation to body weight (95 percent confidence interval of within-pair differences -4.0 to -0.02 ml.kPa-1 x Kg-1; p< 0.05). We conclude that no separate reference values for tidal breathing, Herin-Breuer reflex activity or total respiratory compliance are required for white and black babies in the immediate newborn period. (AU Truncated at 250 words)

Cocaine and ventral brainstem neurotoxicity

One of the complications of cocaine abuse is central cardiorespiratory failure. However, the site and mechanism of cocaine are unknown. The present study evaluates the effect of cocaine applied topically to the caudal and intermediate areas on the ventrolateral surface of the brainstem. These areas are known to be involved in the CO2 /pH chemosensory drive to respiration and in vasomotor control. Cats were anesthetized with urethane (2.0 g/kg), the trachea cannulated and the ventro-lateral surface of medulla oblongata (VMS) exposed. Cocaine prepared in mock CSF pH 7.4 was applied bilaterally to chemosensitive zones using pledgets. The effect of procaine was also tested. Tidal volume (Vt), respiratory frequency (f), arterial blood pressure (BP) and heart rate (HR) were monitored. Cocaine (62.5 ug/site) produced a significant decrease in minute ventilation (Ve) and blood pressure (BP) (p<0.05); the cuadal area was more sentive. In equimolar doses to cocaine, procaine (50 ug/site) produced small but significant effects on BP with no changes in Ve however, twice the equimolar dose(100 ug/site), produced respiratory responses similar to that of cocaine. Alpha and beta adrenoceptor antagonists prazosin (10 ug.site) and propranolol (16.7 ug/site) respectively, failed to alter the hypotensive or respiratory depressant effect of cocaine. Only animals that were hypotensive before or during physostigmine pretreatment (5 ug.site) experienced cardiorespiratory failure upon administration of cocaine. Carbachol (2.5 ug/site) had no effect on the cocaine induced cardiorespiratory responses. The present data suggest that (1) central cocaine neurotoxicity may result from interaction of cocaine with VMS sites; (2) the mechanism of action of cocaine at these sites is similar to that of procaine and does not appear to involve adrenergic receptors; and (3) pretreatment with the involve adrenergic receptors; and (3) pretreatment with the cholinomimetic physostigmine was effective in protecting animals from cocaine induced respiratory failure, its efficacy being limited to those animals that were not hypotensive during pretreatment. (AU)

Ethnic variation in respiratory function in young children

The effect of ethnic origin on respiratory function was assessed in 57 young children aged between 4.9 and 8 years. Functional residual capacity (FRC) and peak expiratory flow rate (PEFR) were measured and related to sitting and standing height in Caucasian and Afro-Caribbean children. No significant differences were found between the two groups in PEFR when related to either standing or sitting height. FRC, when related to standing but not sitting height, was greater in Caucasian children (P<0.01). Sitting height related to standing height was lower in children of Afro-Caribbean decent (P<0.01), suggesting that anthromorphic differences may explain the apparent influence of ethnic origin on respiratory function in young children. (AU)

A pharmacological study of the hypotensive and anticurare effect of Anacardium occidentale

The bark of the cashew tree, Anacardium occidentale, is known to exert various therapeutic effects in the folklore medicine. However, there is little exiperimental evidence to substantiate these claims. West, Garvey and Ling in 1973 reported hypotensive action. Present investigations were carried out to find the possible mode of its hypotensive and anticurare effects. It is now well known that most of the clinically used antihypertensive drugs exert their pharmacotherapeutic effect via a common mode of action in spite of their different origins. Bhargava proposed that the central adrenergic, dopaminergic, cholinergic and tryptaminergic mechanisms in the central nervous system regulate the cardiovascular system, but the existence of such a central mechanism does not rule out the possibility of a peripheral component in the antihypertensive action of the drugs. The pathways followed by the central adrenergic and serotonergic nerves in the central nervous sytem are well suited for the regulation of the blood pressure. Most animals which received Anacardium occindentale showed an initial hypotensive response following the administration. This was marked and was not influenced by several experimental procedure or the drug pretreatments. The delayed hypotensive response occurred in most of the animals between 60 to 120 min after its administration and once set, remained below the basal level all throughout the duration of the experiment. The experimental manoeuvres and drug designs did not influence the delayed hypotensive response. The hypotensive action occurred in rats, cats and dogs and did not show any initial rise in blood pressure. (au)

Cigarette smoking and irreversible airways obstruction in the West Indies

Two communities, one in Jamaica and one in Guyana, have been surveyed in order to investigate the relationships between cigarette smoking and respiratory symptoms, and lung function in the West Indies. Cigarette consumption was less than that reported in the United Kingdom, particularly among women. Smoking was associated with cough, phleghm, increases in total lung capacity and residual volume, and reductions in FEV percent, transfer coeffecient (Kco), and aveolar capillary blood volume (Vc). Vital capacity (VC) and the diffusion capacity of the alveolar membranes (Dm) were normal. After allowing for differences in age and tobacco consumption, less cough, phleghm and airways obstruction occurred in the West Indies than has been reported in the United Kingdom. Forty-seven patients in Jamaica with chronic obstructive lung disease were followed for three years. All except six female asthmatics were either current smokers or ex-smokers. Smoking in patients was associated with a similiar but more severe pattern of lung disease to that found in survey subjects with, in addition, reductions in VC, and Dm. In the non-smoking asthmatics Kco, Dm, and Vc were normal. The lung function of these 47 patients was similiar to that reported for UK patients even though both chronic bronchitis and hypercapnia were considerably less common in Jamaica. Emphysema was present in all six patients who died and came to necropsy. It is suggested that in the West Indies emphysema contributes more than bronchitis to airways obstruction in smokers. There was also evidence that subjects of African origin were less susceptible to the emphysema-producing effect of cigarettes than were other ethnic groups (AU)

Cardio-pulmonary responses and gas exchange during exercise in adults with homozygous sickle-cell disease (sickle-cell anaemia)

Cardio-pulmonary responses and gas exchange during progressive exercise, the ventilatory response to hypercapnia and anthropometric indices were measured in twenty-two Jamiacan adults with homozygous sickle-cell disease. Their anthropometric indices and exercise performances were compared with those observed in healthy but sedentary adults in the Caribbean. The patients had long lower limbs for their height; their body fat, proportion of lean body mass as muscle and vital capacity reduced. Haemoglobin concentration ranged from 4 to 10g/100ml. Heart rate and ventilation were normal at rest. During exercise in the male patients haemoglobin concentrations below about 8g/100ml were associated with an increased demand for anaerobic metabolism. This resulted in excessive lac ticacidaemia and increased ventilation at standard oxygen uptake (hyperpnoea). The ventilation-tidal volume relationship was normal. When allowance was made for differences in body muscle, anaemia did not appear to affect the heart-rate response to exercise. Hyperventilation with respect to carbon dioxide output, increased alveolar-arterial oxygen-tension gradients and abnormal deadspace ventilation during exercise indicated a pulmonary perfusion disturbance with mixed venous shunting. The most likely basis for this disorder was considered to be the sickling phenomenon. Arterial hypoxaemia produced by the pulmonary shunt probably accounted for some of the exercise hyperpnoea, partly by increasing the chemoreceptor drive and partly by encouraging lacticacidaemia. Reduced arterial carbon dioxide tensions and bicarbonate concentrations had lowered the threshold and increased the sensitivity of the ventilatory response to carbon dioxide as measured by rebreathing. Increased chemosensitivity was not thought to have contributed towards the exercise hyperpnoea since arterial carbon dioxide tensions were below the threshold value for ventilatory drive. Exertional dyspnoea in sickle-cell disease was attributed to the combination of hyperpnoea and reduced maximum breathing capacity (MBC) owing to small lung volumes. The fraction of (MBC) used at standard work was therfore abnormally large, and the increased ventilatory effort produced a sensation of breathlessness in some patients (Summary)

The response of malnourished babies to cold

Twelve malnourished Jamaican children, aged 4-6 months, were studied before and after treatment, to see whether malnutrition impared their response to cold. When they were studied in the post-absorptive state and in a neutral thermal environment, they had a lower rate of oxygen consumption per kg body weight, a slower pulse rate, lower body temperatures, lower R.Q., and evidence of a smaller peripheral blood flow on admission to hospital than they did after recovery. The malnourished children failed to increase their heat production above resting levels at 25§ C, and their rectal temperature fell at a rate of 1§ C/hr in spite of a further decrease in peripheral circulation. When they had recovered they maintained their body temperature within the normal range on exposure to this temperature, while increasing their heat production by 20 percent. The thermogenesis was apparently of the non-shivering type. There was evidence of increased metabolic activity in the interscapular brown fat pad at 25§ C both on admission and before discharge. In the malnourished children this activity was not sufficient to produce a measurable increase in total oxygen consumption. Interscapular brown fat was examined at autopsy in thirteen malnourished and fifteen well nourished children aged 1-24 months. Lipid depletion was found in this tissue in the former but not in the latter. This may explain the impared response of the malnourished child to cold. (AU)

The influence of malnutrition on the postprandial metabolic rate and respiratory quotient

Pre- and post-prandial metabolic rates were measured in twelve malnourished Jamaican infants. On admission to hospital, minimal increases in postprandial metabolic rate were found, whereas during the recovery phase when growth was rapid, increases in postprandial metabolic rate of up to 38 percent occurred. After recovery only the five children who were still gaining weight at a rate of more than 4 g/kg body-weight.d continued to show a substantial increase in postprandial metabolism. A highly significant correlation was found between growth rate and the increase in postprandial metabolic rate. Marked differences existed in the respiratory quotient measured 4h after the last meal, the values being low on admission and high during the phase of rapid growth. After a test meal, the respiratory quotient rose sharply both in newly admitted and in recovered children, but fell slightly when the children were studied during the phase of rapid growth. (AU)

Water content level in inspired air on specific airway resistence in rats

The effect of increasing water content in inspired air on specific airway resistence in rats was assessed. The results show that specific airway resistances were significantly related to the water content of the inspired air, above 15.02 mg/m3, the duration of water content exposure and to the type of water nebulized. It is suggested that the increase is composed of a local and neural element caused by accumulation of mucus or mucosal swelling and changes in the composition and consistency of the mucus lining layer, respectively (AU)

Variation in forced expiratory volume curves of asthmatic patients with increased water content

An experiment was designed to provide information on the "safe" level of humidifiction of inspired air in asthmatic patients. It was found that air at 25 degrees celcius and 70 percent relative humidity (RH) (16.11 gm/cu m WC) and 35 degrees celcius, 40 percent RH (17.80 gm/cu m) had no significant effect on forced expiratiory volume parameters. At 25 degrees celcius, 95 percent RH (21.88 gm/cu m WC) and above changes in VC/PVC, FEV 1 and FEV 3, MMF and MBC were significantly affected (P < 0.01). Approximately 21.88 gm/cu m Water content is considered the point at which humidification of inspired air ceases to be therapeutically useful.(AU)

Changes in specific airway conductance in healthy volunteers following nasal and oral inhalation of SO2

Specific airway conductance (sGaw) was measured using a body plethysmograph in 49 healthy volunteers exposed by nose and mouth to sulphur dioxide (SO2) below and above the maximum allowable daily concentration of 5 p.p.m., for periods of up to 1 hour. SO2 caused a decrease in sGaw with both nose and mouth breathing at low concentrations. The decrease in sGaw was greater with mouth breathing. At high concentrations (above 5 p.p.m.) however, there was no significant difference between nose and mouth breathing. In subjects exposed to 5 p.p.m. SO2 for up to 1 hour, there was no further significant decrease in sGaw after 5 minutes. These results suggest that changes in sGaw following SO2 inhalation are related to stimulation of tracheobronchial receptors and that after a period acclimatization occurs (AU)