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Biomedical subjects

W N Gardner

Publications and source records attributed to W N Gardner.

At least 37 records · Page 2Linked to original sources
PubMed1989

Hyperventilation clinical practice.

There is uncertainty about the diagnosis and definition of the hyperventilation syndrome. We prefer to regard hyperventilation (or hypocapnia with which it is synonymous) as a physiological response to abnormally increased respiratory "drive", which can be caused by a wide range of organic, psychiatric and physiological disorders, or a combination of these. This review outlines a clinical scheme for the diagnosis and assessment of hyperventilation and its causes.

Adult↗
PubMed1988

Value of measuring end tidal partial pressure of carbon dioxide as an adjunct to treadmill exercise testing.

The end tidal partial pressure of carbon dioxide (PCO2) was measured during treadmill exercise in 30 normal controls and 113 patients referred for assessment of chest pain. Among the 92 patients without significant ST depression hypocapnia occurred more often in those reporting "typical" than "atypical" chest pain (17 of 22 patients compared with 29 of 70; p less than 0.01). Hypocapnia was uncommon in patients with significant ST depression whether reporting typical or atypical chest pain (one of 10 patients and two of 11, respectively). Hypocapnia at rest (PCO2 less than 4 kPa) occurred in 16 (14%) patients but in only one control. Hypocapnia occurred during or after exercise in only one control and three of the 21 patients with significant ST depression on exercise (group 1). The remaining 92 patients were divided into those with a history suggestive of hyperventilation (group 2; n = 30) and those without (group 3; n = 62). Hypocapnia developed significantly more often in both these groups (21 and 25 patients respectively) than in controls or patients with significant ST depression. An abnormal response of the PCO2 to exercise provided objective data to support a clinical suspicion of chest pain induced by hyperventilation in 24 cases, suggested a cause for equivocal ST depression other than coronary stenosis in five patients, and led to the diagnosis of previously unsuspected respiratory disease in 14 patients. Measurement of end tidal PCO2 gives additional valuable diagnostic information during the conventional treadmill exercise test in patients with both typical and atypical chest pain.

Carbon Dioxide↗
PubMed1988

Panic anxiety and hyperventilation in patients with chest pain: a controlled study.

We studied the relation between mood disorder and hyperventilation (hypocapnia) before and during exercise treadmill testing in 113 chest pain patients attending a cardiac clinic and 30 healthy controls. In most patients end-tidal PCO2 (PCO2) rose in the normal way on exercise but in a subset of 24 (21 per cent) there was no rise: these patients with initial hyperventilation had significantly higher anxiety scores than those with a normal exercise-induced rise in PCO2. Two of the 24 had ischaemic heart disease and 10 (42 per cent) complained of recent panic anxiety compared with 12 (13 per cent) of the 89 with normal rise in PCO2 (p less than 0.05). Rates of psychiatric morbidity were similar in patients with 'typical' and 'atypical' chest pain. Resting hypocapnia occurred more often in patients with panic anxiety than in either anxious or non-anxious patients without panic. Panic patients also reported more symptoms of breathlessness and hyperventilation-related complaints than those without panic. Our findings confirm the important association between panic and hyperventilation in patients with chest pain. Furthermore, patients with exercise-induced hyperventilation are more likely to have a psychiatric than a cardiac disorder. Early detection and treatment of these patients may reduce the potential morbidity associated with unnecessary invasive investigations.

Adult↗
PubMed1987

Laser photodynamic therapy for inoperable bronchogenic squamous carcinoma.

Fifteen consecutive patients with advanced squamous bronchogenic carcinoma, most of whom had had radiotherapy, were given palliative photodynamic therapy, using either haematoporphyrin derivative or dihaematoporphyrin ether to light sensitize their tumour. All tumours responded to treatment by subsequent light at 630 nm and in the 12 patients where adequate tumour illumination was achieved there was complete clearing of the bronchus in three and partial (more than 50 per cent clearing) in the remaining nine, with relief of haemoptysis and/or breathing obstruction. One patient with recurrent tumour in a pneumonectomy stump after radiotherapy has remained disease-free for over two years since photodynamic therapy. The main complications were temporary skin light sensitization reaction in three, infection after reaeration of lung tissue in two, and transient but severe worsening of breathing obstruction in two.

Aged↗
PubMed1986

Controlled study of respiratory responses during prolonged measurement in patients with chronic hyperventilation.

The respiratory responses of 17 patients with chronic hyperventilation but without demonstrable organic disease (group H) to various manoeuvres were compared with those of 21 healthy controls (group C). The responses were tested according to a 60 min protocol in which periods of rest were replaced by exercise, voluntary hyperventilation (VHV), reading, and CO2 inhalation. 5 patients with severe resting hypocapnia were investigated overnight during sleep. Chronic hyperventilation was of two types--persistent or provoked by exercise or VHV. It was due to modest increases in tidal volume and respiratory frequency but was generally not conspicuous. End-tidal PCO2 levels were gradually corrected to near normal during sleep but not by inhalation of CO2.

Adult↗
PubMed1985

Respiratory and psychiatric abnormalities in chronic symptomatic hyperventilation.

Many physicians believe that the hyperventilation syndrome is invariably associated with anxiety or undiagnosed organic disease such as asthma and pulmonary embolus, or both. Twenty one patients referred by specialist physicians with unexplained somatic symptoms and unequivocal chronic hypocapnia (resting end tidal Pco2 less than or equal to 4 kPa (30 mm Hg) on repeated occasions during prolonged measurement) were investigated. All but one complained of inability to take a satisfying breath. Standard lung function test results and chest radiographs were normal in all patients, but histamine challenge showed bronchial hyper-reactivity in two of 20 patients tested, and skin tests to common allergens were positive in three of 18. Ventilation-perfusion scanning was abnormal in a further three of 15 patients studied, with unmatched perfusion defects in two and isolated ventilation defects in one. None of the 21 had thyrotoxicosis, severe coronary heart disease, or other relevant cardiovascular abnormalities. Ten of the 21 patients were neurotic and suffered from chronic psychiatric disturbance characterised by anxiety, panic, and phobic symptoms. The remainder had no detectable psychiatric disorders but reported proportionately more somatic than anxiety symptoms. Severe hyperventilation can occur in the absence of formal psychiatric or detectable respiratory or other organic abnormalities. Asthma and pulmonary embolus must be specifically excluded.

Adult↗
PubMed1983

Unexplained breathlessness and psychiatric morbidity in patients with normal and abnormal coronary arteries.

Of 99 patients with chest pain undergoing coronary arteriography, 31 had normal coronary arteries, 15 slight disease, and 53 significant coronary obstruction. 28 (61%) of the 46 with haemodynamically insignificant disease and 12 (23%) of the 53 with significant obstruction had psychiatric morbidity, assessed by standard interview. 37 patients had several respiratory symptoms and signs not attributable to organic disease, designated unexplained breathing disorder (UBD). UBD was found in 65% of the patients without and 13% of those with significant coronary disease; it was associated with psychiatric morbidity in the former but not in the latter group. Spirographic measurements of tidal volume and frequency were not helpful in detecting UBD but an end-tidal pCO2 below 30 mm Hg was highly suggestive. In the absence of significant coronary disease the associations of chest pain with psychiatric morbidity and UBD are striking. However, coronary disease and UBD are not mutually exclusive, and diagnostic difficulties can occur when they coexist.

Angina Pectoris↗
PubMed1983

Breathing in fetal lambs: the effect of brain stem section.

The effects of section of the brain stem caudally (through the upper pons or mid-collicular) or rostrally (through the caudal hypothalamus or anterior commissure-suprachiasmatic nucleus) were studied in fetal lambs from 118 days gestation, after recovery in utero. In lambs sectioned caudally, breathing movements and electrocortical activity were dissociated. After some days recovery breathing tended to become continuous, with an abnormal prolongation of inspiratory time. Isocapnic hypoxia caused an increase in the rate and amplitude of breathing. After carotid denervation hypoxia still caused an increase in the amplitude of breathing. In lambs sectioned rostrally, there was also dissociation between breathing movements and electrocortical activity. Breathing remained episodic, with an incidence similar to that of intact fetal lambs. In two lambs after 10 days of recovery the breathing and electrocortical rhythms returned, from time to time, to their normal phasic relationship. Isocapnic hypoxia caused a diminution or arrest of breathing, as in intact lambs. The cardiovascular effects of transection were examined. Baroreflex sensitivity was normal in those lambs sectioned caudally and enhanced in those sectioned rostrally. It is concluded first that as a result of rostral section, independent episodic rhythms of fetal breathing and electrocortical activity can be dissociated. Secondly, moderate isocapnic hypoxia causes arrest of fetal breathing indirectly, requiring the integrity of a suprapontine mechanism. And thirdly, after caudal section of the brain stem, hypoxia causes enhancement of fetal breathing efforts, independently of the carotid chemoreceptors. Possible mechanisms are discussed.

Animals↗
PubMed1983

Role of the larynx in control of pattern of breathing during CO2 inhalation in humans.

To determine whether change of laryngeal resistance causes shortening of expiratory time (TE) and hence increase of respiratory frequency with CO2 inhalation in conscious humans, 11 fit male subjects with permanent tracheostomies after laryngectomy for cancer (L group) and 8 matched control subjects (C group) inhaled CO2 in mild hyperoxia to produce various levels of steady-state hyperpnea within "nonvagal" range 1. Breathing pattern was averaged at the end of each steady state and behaved similarly in both groups. As end-tidal PCO2 (PACO2) increased, TE significantly shortened in both groups, whereas inspiratory time (TI) remained roughly constant (slightly increasing in the L group), suggesting that the larynx, at least in range 1, has no major role in determining this pattern. Quantitative comparison between the two groups showed that in the L group TE was significantly longer, whereas expiratory flow peaked and declined significantly earlier, resulting in a greater tendency to form end-expiratory pauses. All differences were greatest in eucapnia and decreased as PACO2 increased. Despite matched mean PACO2 values, mean tidal volume (VT) ventilation and mean inspiratory flow (VT/TI) were significantly less in the L group, and the slope of VT/TI vs. PACO2 was significantly depressed.

Adult↗
PubMed1982

Effects of hypercapnia on tracheal pressure, diaphragm and intercostal electromyograms in unanaesthetized fetal lambs.

1. The electromyographic (e.m.g.) activity of the diaphragm and intercostal muscles has been recorded during breathing movements of unanaesthetized lambs in utero (109-135 days), and compared with the changes of tracheal pressure.2. The diaphragm e.m.g. was irregular in size, shape and timing, with a variable rate of rise during inspiration, often with a flattening of integrated activity before the end of a breath and with little or no post-inspiratory activity.3. The diaphragm e.m.g. gave the most reliable measurements of breath interval and incidence: in eucapnia mean T(I) was 0.45+/-0.02 (S.E. of mean) and T(E) was 0.74+/-0.05 sec, and 58-100% of the diaphragm bursts were associated with identifiable and appropriate changes of tracheal pressure.4. During fetal hypercapnia, produced by increasing the maternal inspired CO(2) in a single change or series of step changes, tracheal pressure amplitude and its rate of change during inspiration increased progressively over the P(a, CO2) range of 37-87 mmHg.5. In eucapnia the area, amplitude and inspiratory slope of the integrated diaphragm e.m.g. were not always correlated with tracheal pressure amplitude, and in hypercapnia they increased only in the lower part of the P(a, CO2) range. Inspiratory intercostal activity increased progressively as the P(a, CO2) was raised.6. The frequency histograms of variables derived from the tracheal pressure, diaphragm and intercostal e.m.g.s were skewed to the left in eucapnia but became normalized during hypercapnia. The rate and depth of breathing became regular.7. The response to mild asphyxia was a combination of the responses to hypercapnia and hypoxia.8. The interpretation of the tracheal pressure and diaphragm e.m.g. as measures of the ;depth' of breathing and respiratory ;drive' in the fetal lamb is discussed.

Animals↗
PubMed1982

Quantitative analysis of effect of neodymium-YAG laser on transplanted mouse carcinomas.

Intradermally transplanted non-immunogenic murine carcinomas measuring 3-6 mm in diameter were exposed to a neodymium-YAG laser beam (1060 nm) over a range of exposure times (0.5-6 seconds) and energy densities (expressed as watts/mm2 exposure field). Subsequent growth of the irradiated tumours was compared with that of untreated tumours. A clear dose-response relationship dependent only on power delivered per unit area was found. Below a given dose threshold (about 2 joules/mm2) the tumours continued to grow at the same rate as the control tumours although an effect of irradiation could be seen histologically. Above this threshold the tumours completely disappeared but by 10-14 days started to regrow at a rate slightly greater than in the control mice; the reason for this increased rate remains to be determined. At the highest doses (above about 5.5 joules/mm2) there was complete regression and skin healing, with no evidence of local recurrence in seven animals and with no evidence of distant metastases in six out of seven up to 12 months later, a result not previously achieved by surgical excision. The laser provides a controlled and simply applied method of tumour eradication. This animal model gives a quantitative basis for further studies of the effects of laser irradiation on tumour growth.

Adenocarcinoma↗
PubMed1980

The pattern of breathing following step changes of alveolar partial pressures of carbon dioxide and oxygen in man.

1. The pattern of breathing during the approach to the steady state following step changes of end-tidal P(CO2) and P(O2) has been determined in normal conscious human subjects. Three types of step were studied: (a) steps of P(A, CO2) against a constant background of hyperoxia (P(A, O2) approximately 200), an almost pure intracranial chemoreceptor stimulus, (b) steps of P(A, O2) between approximately 50 and 80 torr against a background of constant mild hypercapnia, an arterial chemoreceptor stimulus, and (c) steps of P(A, CO2) against a background of constant hypoxia (P(A, O2) approximately 50), a mixed stimulus. Steps were small and the responses barely detectable by the subjects.2. Steps of CO(2) in hyperoxia produced the slowest approach to the steady state. A single exponential fitted the ventilation response up to about 4 min (mean half time 83 sec for the ;up' and 69 sec for the ;down' transients). During the transient the pattern of change of tidal volume (V(T)) and expiratory time (T(E)) was the same as in the steady state. Inspiratory time (T(I)), however, in the early part of the transient, changed in the opposite direction to T(E), returning to its steady value only after 1(1/2)-3 min. This effect occurred in both ;up' and ;down' transients and resulted in a smaller change of respiratory frequency than would have been predicted from the steady-state response.3. Hypoxic steps produced the fastest approach to the steady state with mean half-times for ventilation of 10.9 sec for the ;up' transients and 6.6 sec for the ;down'. T(I) followed the same pattern during the transient as in the steady state, whereas T(E), following the step out of hypoxia, lengthened to far beyond its final steady value within five breaths of the step, only returning to its steady-state value 3-4 min after the step. This resulted in an exaggerated change of frequency during the early part of the transient.4. Steps of CO(2) in hypoxia, a mixed peripheral and central chemoreceptor stimulus, showed a ventilation response which was best fitted by two exponentials, the half-times of which were consistent with those obtained for the separate responses. The patterning was also consistent with a mixed response, more so for T(I) than for T(E).5. The steady-state pattern derived from the pre-switch means was consistent with the pattern previously described.6. Possible mechanisms are discussed. It is suggested that these results could explain the different patterns seen in the past by those using re-breathing and steady-state techniques.7. The validity of using one or two breath oxygen or nitrogen tests (or other similar tests) as a quantitative measure of the hypoxic response in man is questioned.

Adult↗