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Brischetto MJ, Millman RP, Peterson DD, Silage DA, Pack AI. Effect of aging on ventilatory response to exercise and CO2. JOURNAL OF APPLIED PHYSIOLOGY: RESPIRATORY, ENVIRONMENTAL AND EXERCISE PHYSIOLOGY 1984; 56:1143-50. [PMID: 6427148 DOI: 10.1152/jappl.1984.56.5.1143] [Citation(s) in RCA: 85] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Studies were performed to determine the effects of aging on the ventilatory responsiveness to two known respiratory stimulants, inhaled CO2 and exercise. Although explanation of the physiological mechanisms underlying development of exercise hyperpnea remains elusive, there is much circumstantial evidence that during exercise, however mediated, ventilation is coupled to CO2 production. Thus matched groups of young and elderly subjects were studied to determine the relationship between increasing ventilation and increasing CO2 production (VCO2) during steady-state exercise and the change in their minute ventilation in response to progressive hypercapnia during CO2 rebreathing. We found that the slope of the ventilatory response to hypercapnia was depressed in elderly subjects when compared with the younger control group (delta VE/delta PCO2 = 1.64 +/- 0.21 vs. 2.44 +/- 0.40 l X min-1 X mmHg-1, means +/- SE, respectively). In contrast, the slope of the relationship between ventilation and CO2 production during exercise in the elderly was greater than that of younger subjects (delta VE/delta VCO2 = 29.7 +/- 1.19 vs. 25.3 +/- 1.54, means +/- SE, respectively), as was minute ventilation at a single work load (50 W) (32.4 +/- 2.3 vs. 25.7 +/- 1.54 l/min, means +/- SE, respectively). This increased ventilation during exercise in the elderly was not produced by arterial O2 desaturation, and increased anaerobiasis did not play a role. Instead, the increased ventilation during exercise seems to compensate for increased inefficiency of gas exchange such that exercise remains essentially isocapnic. In conclusion, in the elderly the ventilatory response to hypercapnia is less than in young subjects, whereas the ventilatory response to exercise is greater.
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Ledlie JF, Pack AI, Fishman AP. Effects of hypercapnia and hypoxia on abdominal expiratory nerve activity. JOURNAL OF APPLIED PHYSIOLOGY: RESPIRATORY, ENVIRONMENTAL AND EXERCISE PHYSIOLOGY 1983; 55:1614-22. [PMID: 6643196 DOI: 10.1152/jappl.1983.55.5.1614] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
We examined the effects of progressive hypercapnia and hypoxia on the efferent neural activity in a whole abdominal expiratory nerve (medial branch of the cranial iliohypogastric nerve (L1) in anesthetized, paralyzed dogs. To eliminate effects of phasic lung and chest-wall movements on expiratory activity, studies were performed in the absence of breathing movements. Progressive hyperoxic hypercapnia and isocapnic hypoxia were produced in the paralyzed animals by allowing 3-5 min of apnea to follow mechanical ventilation with 100% O2 or 35% O2 in N2, respectively; during hypoxia, isocapnia was maintained by intravenous infusion of tris(hydroxymethyl)aminomethane buffer at a predetermined rate. To quantify abdominal expiratory activity, mean abdominal nerve activity in a nerve burst was computed by integrating the abdominal neurogram and dividing by the duration of the nerve burst. Hypercapnia and hypoxia both increased mean abdominal nerve activity and decreased expiratory duration. In contrast to the ramplike phrenic neurogram, the abdominal neurogram consisted of three phases: an initial rising phase, a plateau phase in which abdominal nerve activity was approximately constant, and a terminal declining phase in which the activity returned to the base-line level. The height of this plateau phase and the rates of rise and decline of abdominal nerve activity all increased with increasing hypercapnia and hypoxia. We conclude that, with proprioceptive inputs constant, both hypercapnia and hypoxia are excitatory to abdominal expiratory neural activity.
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Pack AI, DeLaney RG. Response of pulmonary rapidly adapting receptors during lung inflation. JOURNAL OF APPLIED PHYSIOLOGY: RESPIRATORY, ENVIRONMENTAL AND EXERCISE PHYSIOLOGY 1983; 55:955-63. [PMID: 6629929 DOI: 10.1152/jappl.1983.55.3.955] [Citation(s) in RCA: 38] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Studies were conducted to establish the factors that determine the response of canine pulmonary rapidly adapting receptors (RAR) during lung inflation. Inflations of the lung were performed at several constant rates during which the activity of individual RAR was counted. At each rate of inflation tested multiple identical tests were performed. The volume of each test inflation was controlled. Data obtained in all tests at each flow rate were averaged to give the mean response of the receptor at that rate of inflation. These studies indicate the major response characteristics of RAR during lung inflation in conditions of relatively constant lung mechanics. First, at a constant rate of inflation, the activity of RAR augments increasingly as the lung is expanded. Second, their activity is influenced markedly by the rate of inflation. However, this sensitivity is nonlinear. Specifically, at low rates of inflation increases in flow rate produce more marked augmentation of RAR firing than do identical increases in flow at higher rates of inflation. The major difference between receptors is in their threshold; however, this too is a function of flow rate. With increasing flow rate the threshold, whether measured as the inflation volume or transpulmonary pressure at which receptors begin to fire, declines. The response of receptors, however, with thresholds over the entire range show the major features discussed above. The present results provide quantitative information which are necessary to begin to eludicate the transduction properties of this receptor type.
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Millman RP, Bevilacqua J, Peterson DD, Pack AI. Central sleep apnea in hypothyroidism. THE AMERICAN REVIEW OF RESPIRATORY DISEASE 1983; 127:504-7. [PMID: 6838058 DOI: 10.1164/arrd.1983.127.4.504] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
This is a report of a 45-yr-old male patient who developed central sleep apnea syndrome because of hypothyroidism. In response to L-thyroxine therapy, the patient became euthyroid, and the apneic phenomenon disappeared. Previous reports have suggested that hypothyroidism can produce obstructive sleep apnea from either narrowing of the upper airway secondary to deposition of mucopolysaccharides and protein extravasation into the tissues or from abnormalities in ventilatory control. The present patient did demonstrate evidence of profound dysfunction of his respiratory control center: before therapy, the patient manifested blunted ventilatory and occlusion pressure responses to hypoxia and normal responsiveness to hypercapnia; after therapy, hypoxic responsiveness was restored and the ventilatory response to hypercapnia doubled. Hypothyroidism should be included in the differential diagnosis of central sleep apnea.
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DeLaney RG, Laurent P, Galante R, Pack AI, Fishman AP. Pulmonary mechanoreceptors in the dipnoi lungfish Protopterus and Lepidosiren. THE AMERICAN JOURNAL OF PHYSIOLOGY 1983; 244:R418-28. [PMID: 6402942 DOI: 10.1152/ajpregu.1983.244.3.r418] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Pulmonary mechanoreceptors in the dipnoi lungfish Protopterus aethiopicus and Lepidosiren paradoxa were identified and characterized both in vivo and in vitro. Both slowly adapting receptors (SAR) and rapidly adapting receptors (RAR) were found, with the majority of receptors being of the slowly adapting type. The SAR discharged during inflation once their threshold volume was exceeded, and this activity persisted during prolonged lung inflation. For most of the SAR, interaction between the rate of inflation and lung volume was involved in setting the firing rate of the receptor. Increase in intrapulmonary carbon dioxide partial pressure decreased the activity of the SAR during sustained inflation at a constant intrapulmonary pressure. The RAR also discharged during inflation once the threshold volume was exceeded. However, in contrast to the SAR, the RAR became silent within 1.5 - 15 s after the end of inflation. The activity of these receptors during inflation was influenced predominantly by the rate and influenced little by the volume of inflation. According to these observations, the behavior of lungfish pulmonary mechanoreceptors closely resembles that of pulmonary mechanoreceptors in amphibians but differs from that of mechanoreceptors in the swim bladder of teleosts.
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Pack AI, Ogilvie M, DeLaney RG, Murray-Smith DJ. Action of positive feedback related to lung inflation in the control of ventilation. COMPUTERS AND BIOMEDICAL RESEARCH, AN INTERNATIONAL JOURNAL 1982; 15:503-18. [PMID: 7160166 DOI: 10.1016/0010-4809(82)90013-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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132
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Millman RP, Silage DA, Peterson DD, Pack AI. Effect of aerosolized histamine on occlusion pressure and ventilation in humans. JOURNAL OF APPLIED PHYSIOLOGY: RESPIRATORY, ENVIRONMENTAL AND EXERCISE PHYSIOLOGY 1982; 53:690-7. [PMID: 7129991 DOI: 10.1152/jappl.1982.53.3.690] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
To define further the mechanism by which inspiratory neural activity is increased in asthma, we studied the effect of aerosolized histamine on occlusion pressure (P100) and ventilation in conscious humans while end-tidal CO2 partial pressure was maintained at a constant, slightly hypercapnic level. The dose of histamine we employed varied from subject to subject but was such that it produced a 70% reduction in specific airway conductance in each subject. In 9 of the 13 subjects tested, inhaled histamine significantly increased P100. This increase was not due to changes in functional residual capacity, which was not affected by aerosolized histamine. Inhalation of isoproterenol abolished the effects of histamine on specific airway conductance and P100. Anesthesia of the airways by lidocaine eliminated the effect of histamine on P100 but did not alter the magnitude of the change in specific airway conductance produced by histamine. We conclude that the increase in occlusion pressure seen after the inhalation of histamine in humans depends on both contraction of bronchial smooth muscle and stimulation of airway receptors.
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Nixon W, Pack AI. Effect of gaseous interaction between lung units on the expired concentration of nitrogen. JOURNAL OF APPLIED PHYSIOLOGY: RESPIRATORY, ENVIRONMENTAL AND EXERCISE PHYSIOLOGY 1982; 53:496-504. [PMID: 7118669 DOI: 10.1152/jappl.1982.53.2.496] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
There is debate over the mechanisms that produce the alveolar slope, with theories relating to both series and parallel inhomogeneity being proposed. We use a mathematical model of pulmonary gas transport, which incorporates both series and parallel effects, to investigate the relevance of each in the production of this alveolar slope. Interaction between lung units is specifically studied by simulating mixing at both proximal- and distal-branch points in the bronchial tree. During expiration mixing of the gas from inhomogeneous parallel lung units leads to concentration gradients within each unit. The resultant effect on the concentration of the expirate depends on the position in the bronchial tree at which this mixing takes place; proximal interaction alters the initial phase of the expired concentration profile, whereas distal interaction changes the magnitude of the alveolar slope. The net effect of distal interaction is to produce a greater alveolar slope for gases with low molecular diffusivity. These effects are present even in the absence of asynchronous emptying of lung units but may be enhanced by it. These results help to clarify controversies about the mechanisms underlying production of the alveolar slope.
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Pack AI, Hertz BC, Ledlie JF, Fishman AP. Reflex effects of aerosolized histamine on phrenic nerve activity. J Clin Invest 1982; 70:424-32. [PMID: 7096572 PMCID: PMC371251 DOI: 10.1172/jci110632] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Studies were conducted in anesthetized, paralyzed dogs on the effect of aerosolized histamine on phrenic nerve activity. The paralyzed dogs were ventilated in phase with their recorded phrenic nerve activity at a constant inspiratory flow-rate, using a cycle-triggered ventilator. Phrenic nerve activity was measured before and during administration of aerosolized histamine while the inspiratory flow-rate and arterial blood gases were kept constant. In addition, before and after histamine, phrenic nerve activity was recorded for single bursts during which the ventilator was switched off. The effects of histamine on respiratory resistance were prevented by prior administration of isoproterenol and atropine. Although no changes occurred in respiratory resistance, histamine increased the instantaneous magnitude of phrenic nerve activity. The effect was evident early in the inspiratory period and was found even when the lungs were not inflated. Inflation of the lungs excited phrenic nerve activity; this effect increased after histamine. All of these actions of histamine were abolished by vagotomy. We conclude that histamine increased phrenic nerve activity during inspiration by a vagal reflex.
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Peterson DD, Pack AI, Silage DA, Fishman AP. Effects of aging on ventilatory and occlusion pressure responses to hypoxia and hypercapnia. THE AMERICAN REVIEW OF RESPIRATORY DISEASE 1981; 124:387-91. [PMID: 7294501 DOI: 10.1164/arrd.1981.124.4.387] [Citation(s) in RCA: 37] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Studies were performed to examine the decrease in ventilatory response to hypoxia and hypercapnia in the elderly and to explore its etiology. For this purpose, matched groups of normal elderly (65 to 79 yr of age) and young subjects were used. Standard pulmonary function tests were supplemented in both groups by determination of total respiratory compliance and the ventilatory responses to hyperoxic hypercapnia and isocapnic hypoxia using rebreathing methods. While testing the ventilatory responses, we recorded minute ventilation and its components, as well as mouth occlusion pressures, and rib cage and abdominal-diaphragmatic compartmental ventilation (magnetometry). We found that ventilatory responses to both hypercapnia and hypoxia were reduced in the elderly by approximately 50%. These reductions were not related to any change in control of respiratory timing, but to a large reduction in mean inspiratory airflow. The reduced airflow could not be attributed to alterations in pulmonary mechanics since the differences in mechanics between the groups were small. Instead, since the occlusion pressure responses to hypercapnia and hypoxia were reduced in the elderly proportionately to the ventilatory responses, reduction in neuromuscular inspiratory output was likely to be the major factor.
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137
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Marino PL, Davies RO, Pack AI. The responses of I beta cells to increases in the rate of lung inflation. Brain Res 1981; 219:289-305. [PMID: 7260634 DOI: 10.1016/0006-8993(81)90292-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The activity of inspiratory cells in the region of the nucleus of the tractus solitarius (NTS) was recorded extracellularly in paralyzed, artificially ventilated cats either during chloralose-urethane anesthesia or following midcollicular decerebration. Twenty-three of the 68 inspiratory cells recorded in the region of the NTS were classified as I beta cells on the basis of their response to withholding lung inflation. The dynamic sensitivity of I beta cells was determined by studying their response to increases in the rate of lung inflation at constant peak volume. The I beta cells in this study showed 3 distinct patterns of response to increases in the rate of inflation. Five cells showed no change in firing pattern (fixed firing pattern). Ten cells showed an increase in the rate of rise of cell activity but no change in peak frequency (low dynamic sensitivity). Eight cells showed increases in both the rate of rise of cell activity and peak frequency (high dynamic sensitivity). It was concluded that I beta cells are not a functionally homogeneous population, at least in terms of their dynamic sensitivity. Cells showing fixed firing patterns have the characteristics of off-switch neurons. Cells with low levels of dynamic sensitivity may receive afferents from pulmonary stretch receptors. Cells showing a high degree of dynamic sensitivity may receive afferents from rapidly adapting receptors. The fact that I beta cells are not a functionally homogeneous population may explain the many divergent observations reported from studies of these cells.
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Pack AI, DeLaney RG, Fishman AP. Augmentation of phrenic neural activity by increased rates of lung inflation. JOURNAL OF APPLIED PHYSIOLOGY: RESPIRATORY, ENVIRONMENTAL AND EXERCISE PHYSIOLOGY 1981; 50:149-61. [PMID: 7009523 DOI: 10.1152/jappl.1981.50.1.149] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Studies were conducted in anesthetized paralyzed dogs using a cycle-triggered constant-flow ventilator, which ventilated the animal in phase with the recorded phrenic neural activity. Intermittently tests were performed in which the animal was ventilated with a different airflow for a single breath. Increased airflows, within the range generated during spontaneous breathing, caused an increased rate of rise of the moving average phrenic neurogram and a shortening of the duration of the nerve burst. The magnitude of the increase in the rate of rise of the neurogram was related to the level of inspiratory airflow. Tests with brief pulses of airflow showed that an increase in the rate of rise of the phrenic neurogram could be produced without inflating the lung above the resting tidal volume of the animal. Similar results were obtained with negative-pressure ventilation and the effects were abolished by vagotomy. This vagally mediated augmentation of phrenic neural output may accelerate the inspiratory volume change in the lung during spontaneous breathing at hyperpneic levels.
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139
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Murphy D, Pack AI, Imrie CW. The mechanism of arterial hypoxia occurring in acute pancreatitis. THE QUARTERLY JOURNAL OF MEDICINE 1980; 49:151-163. [PMID: 7433633] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Respiratory Function has been measured in 14 patients with acute pancreatitis, none of whom has a previous history of cardiac or respiratory disease. Their mean age was 40 years, mean PaO2 on admission, 11 kPa, and all had normal chest radiographs at that time. Arterial hypoxia was a common development and the mean PaO2 at the time of most severe hypoxia was 8.6 kPa with the lowest individual recording 4.9 kPa. In addition to daily arterial blood gas monitoring, dynamic ventilatory tests and measurements of lung volume, transfer factor, closing volume, right to left shunts and studies of gas exchange were performed. Gas exchange and shunt measurements indicated that the major abnormality responsible for arterial hypoxia was right to left shunting. Seven patients developed radiological abnormalities, five of whom has pleural effusions. Five patients showed a mild restriction in lung volume but there were no major consistent abnormalities of dynamic ventilatory tests, transfer factor, or closing volumes. Thus small airway closure, in dependent parts of the lung and less certainly loss of surfactant are unlikely to be major factors in the aetiology of arterial hypoxia in patients with acute pancreatitis. All measurements were repeated at least three months after the acute illness. The respiratory insufficiency which occurs in this disease is possibly another variant of the adult respiratory distress syndrome.
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140
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Milne JA, Howie AD, Pack AI. Dyspnoea during normal pregnancy. BRITISH JOURNAL OF OBSTETRICS AND GYNAECOLOGY 1978; 85:260-3. [PMID: 638094 DOI: 10.1111/j.1471-0528.1978.tb10497.x] [Citation(s) in RCA: 83] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The incidence, severity and time-course of dyspnoea were assessed in 62 women on eight occasions throughout a normal pregnancy. Fifteen per cent of subjects noticed an increase in dyspnoea in the first trimester compared with the nonpregnant state and in almost half of them dyspnoea was experienced before 19 weeks gestation; 76% complained of this symptom by 31 weeks gestation. After this time, few subjects noticed any increase in their symptoms.
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141
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Boddy K, Davies DL, Howie AD, Madkour MM, Mahaffy ME, Pack AI. Total body and exchangeable potassium in chronic airways obstruction: a controversial area? Thorax 1978; 33:62-6. [PMID: 417419 PMCID: PMC470847 DOI: 10.1136/thx.33.1.62] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Potassium deficiency is an important complication in the treatment of heart disease. However, there is a serious dichotomy in the literature. Severe potassium depletion has been reported in this condition when exchangeable potassium was measured whereas normal levels or marginal depletion were found in measurements of total body potassium. To clarify this situation, simultaneous measurements of total body potassium by whole-body counting, and of exchangeable potassium by isotope dilution using 43K, were made in 10 male subjects with established airways obstruction. Sequential determinations showed that exchangeable potassium increased up to 68 hours after administration, and values obtained at only 24 hours would have been a substantial underestimate. In this group of subjects neither total body nor exchangeable potassium at 48 hours was significantly different from the expected normal value.
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Milne JA, Pack AI, Coutts JR. Gas exchange and acid-base status during the normal human menstrual cycle and in subjects taking oral contraceptives [proceedings]. J Endocrinol 1977; 75:17P-18P. [PMID: 591821] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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143
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Pack AI. A criticism of the organisation of the National Health Service. Scott Med J 1977; 22:267-76. [PMID: 929170 DOI: 10.1177/003693307702200407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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144
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Milne JA, Mills RJ, Coutts JR, Macnaughton MC, Moran F, Pack AI. The effect of human pregnancy on the pulmonary transfer factor for carbon monoxide as measured by the single-breath method. CLINICAL SCIENCE AND MOLECULAR MEDICINE 1977; 53:271-6. [PMID: 913050 DOI: 10.1042/cs0530271] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
1. The pulmonary transfer factor for carbon monoxide was measured by the single-breath method in 21 pregnant women with no previous history of cardiac or respiratory disease. Measurements were made at monthly intervals throughout pregnancy and once post partum. 2. The transfer factor was higher in the first trimester of pregnancy than in the non-pregnant state. There was a fall in the transfer factor during pregnancy until 26 weeks gestation, after which no further decrease was observed. 3. The changes in transfer factor were not explained by alterations in haemoglobin concentration or alveolar volume. 4. Simultaneous serial estimation of plasma 17beta-oestradiol were performed in all the subjects. There was no obvious direct relation between changes in the concentration of this hormone and transfer factor measurements.
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145
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Milne JA, Mills RJ, Howie AD, Pack AI. Large airways function during normal pregnancy. BRITISH JOURNAL OF OBSTETRICS AND GYNAECOLOGY 1977; 84:448-51. [PMID: 889740 DOI: 10.1111/j.1471-0528.1977.tb12621.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Specific airways conductance and forced expiratory volume in one second were measured monthly from the first trimester until term in 30 subjects in the course of a normal pregnancy. Measurements were also made in the postpartum period. There was no significant change in these measurements either throughout pregnancy or compared with postpartum values. Our results suggested that the function of the larger pulmonary airways was not altered in pregnancy.
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146
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Pack AI, McCusker R, Moran F. A computer system for processing data from routine pulmonary function tests. Thorax 1977; 32:333-41. [PMID: 329462 PMCID: PMC470612 DOI: 10.1136/thx.32.3.333] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
In larger pulmonary function laboratories there is a need for computerised techniques of data processing. A flexible computer system, which is used routinely, is described. The system processes data from a relatively large range of tests. Two types of output are produced--one for laboratory purposes, and one for return to the referring physician. The system adds an automatic interpretative report for each set of results. In developing the interpretative system it has been necessary to utilise a number of arbitrary definitions. The present terminology for reporting pulmonary function tests has limitations. The computer interpretation system affords the opportunity to take account of known interaction between measurements of function and different pathological states.
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147
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Milne JA, Pack AI, Mills RJ, Howie AD, Macnaughton MC. LARGE AIRWAYS FUNCTION DURING NORMAL PREGNANCY. BJOG 1977. [DOI: 10.1111/j.1471-0528.1977.tb12566.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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148
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Milne JA, Pack AI, Macnaughton MC, Moran F. THE EFFECT OF PREGNANCY ON THE PULMONARY TRANSFER FACTOR (DIFFUSING CAPACITY) FOR CARBON MONOXIDE AS MEASURED BY THE SINGLE-BREATH METHOD. BJOG 1977. [DOI: 10.1111/j.1471-0528.1977.tb12477.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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149
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Abstract
Total body potassium was measured in 12 patients with cor pulmonale, by determination of potassium-40, a naturally occurring radioisotope. In all subjects the observed value of total body potassium showed no significant depletion when compared with that predicted from height and age. All previous studies in similar groups of patients have been confined to the estimation of exchangeable potassium by the technique of isotope dilution. Results using the latter technique have shown gross potassium depletion. It is suggested that the apparent disparity between total body potassium and exchangeable potassium could be explained by the requirement for a longer equilibration period when using isotope dilution techniques in patients who are in chronic hypoxaemic state.
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150
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Murray-Smith DJ, Pack AI. Proceedings: Dynamic modelling of respiratory gas exchange for clinical applications. CLINICAL SCIENCE AND MOLECULAR MEDICINE 1974; 46:26P-27P. [PMID: 4853808 DOI: 10.1042/cs046026pa] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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