Dyspnea: mechanisms, evaluation and treatment.
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Biomechanical Phenomena↗
Biomedical subjects
A Guz
Publications and source records attributed to A Guz.
Comparison of human lung surface protein profiles from the central and peripheral airways sampled using two regional lavage techniques.
This study describes two new techniques of lung lavage which selectively remove material from the central airways, or from the lung below the seventh generation. Bronchograms confirmed that discrete regions of the lung were washed by central lavage (CL; maximum airway diameter approximately 6.5 mm) and peripheral lavage (PL; maximum airway diameter approximately 1.3 mm), and that both could be clearly distinguished from conventional bronchoalveolar lavage (BAL). These techniques were used to establish whether or not large-airway proteins made a major contribution to the protein profile of BAL. Twenty consecutive patients undergoing routine fibreoptic bronchoscopy were investigated. More bronchial mucus proteinase inhibitor per unit albumin and per unit total measured antiproteinase was present in CL than PL or BAL. In contrast alpha 1-proteinase inhibitor per unit albumin and as a percentage of total measured antiproteinase was lower in CL than in other lavage types. There were no differences in elastase activity, irrespective of the way in which the data were expressed. As no differences were found between BAL and PL for any of the variables measured, it was concluded that in the subjects studied the contribution of CL proteins to BAL was minimal.
Adult↗
Airway anaesthesia and breathing pattern during exercise.
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Anesthesia, Local↗
The elastase: anti-elastase profile in lung lavage from sarcoidosis patients.
One feature of pulmonary sarcoidosis is an increase of lymphocyte numbers in bronchoalveolar lavage fluid (BALF). In some patients the number of polymorphonuclear neutrophils (PMN) also rises. It has been suggested that the prognosis for the latter subjects is likely to be worse than that for the former, but the damaging agent (or agents) released by the PMN have not yet been identified. Therefore, in the current study, the activity of one neutrophilic enzyme, elastase, which is known to damage the pulmonary interstitium, has been assessed in sarcoid BALF and compared to BALF from subjects matched for age, sex and smoking status. As BALF also contains locally-produced and serum-derived inhibitors of elastase, levels of which may change in subjects with sarcoidosis, the serine protease inhibitory capacity and the levels of three anti-elastases have been measured in the samples. Levels of the serum-derived antiproteases, alpha 1 proteinase inhibitor (alpha 1PI) and alpha 2 macroglobulin (alpha 2M) were found to be significantly increased. However, alpha 1PI/albumin and alpha 2M/albumin ratios were unchanged, suggesting that the increased levels were due to an increased permeability of the alveolar-capillary barrier. The total protease inhibitory capacity was elevated and this could be entirely explained by the raised levels of alpha 1PI and alpha 2M. Levels of the locally-produced inhibitor were unaltered. The elastolytic capacity of sarcoid BALF was unchanged. Thus, the elastase: anti-elastase balance was shifted against elastolytic activity.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Cough associated with captopril and enalapril.
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Captopril↗
Respiratory health workers visiting patients with chronic respiratory disability.
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Community Health Nursing↗
Controlled trial of respiratory health worker visiting patients with chronic respiratory disability.
Seventy five patients with chronic respiratory disability were randomised to a group visited by a respiratory health worker (42) or control group (33). The first group was visited monthly by a respiratory nurse, who gave education and support. The effect of the intervention was assessed in terms of quality of life (by questionnaires), the number and duration of admissions to hospital, and the number of deaths. The questionnaires on quality of life showed no changes in either group during the study, but nearly all of the group visited by a respiratory health worker said that they valued the visits and wished them to continue. Their knowledge about their condition also improved compared with that of the controls. The duration of stay in hospital for respiratory reasons in the group visited by a respiratory health worker was longer than that of control patients. This was explained by their being scored as more ill than the controls on admission. Fewer patients died in the group visited by a respiratory health worker than in the control group (p = 0.11). The patients in the group visited by respiratory health workers may have survived longer because they sought help rather than dying at home. If confirmed this could have implications for the cost of their care.
Aged↗
Blockade of 'alveolar' and airway reflexes by local anesthetic aerosol in dogs.
To determine whether local anesthetic aerosol could selectively block a reflex thought to originate from the alveoli, two small particle bupivacaine aerosols (mass median diameters 1.0 and 1.7 micron) were administered on separate occasions to spontaneously breathing anesthetized dogs. Both aerosols resulted in a small but statistically significant increase in VT and one produced an increase in f. The pulmonary chemoreflex to right heart injection of capsaicin, the cough reflex and the Hering-Breuer inflation reflex were unaffected. The ability of a large particle aerosol (mass median diameter 4.8 micron) to block these reflexes was also assessed. This aerosol produced a progressive slowing and deepening of breathing which was maximal after 20 min of aerosol inhalation. Ten min of this aerosol attenuated the pulmonary chemoreflex and abolished the cough and inflation reflexes; 20 min abolished all reflexes. These had recovered by about 1 h after aerosol. Intravenous bupivacaine had no effect on breathing or any reflex. We conclude that a local anesthetic aerosol can block reflexes arising from the alveoli, but not selectively.
Aerosols↗
Evidence for individuality of breathing patterns in resting healthy man.
This study attempts to answer the question of whether there is a characteristic individuality of breathing pattern in conscious man. Measurements of breathing pattern, electroencephalograms and electrooculograms were made on 41 healthy individuals under standardised conditions of relaxed wakefulness, with a minimum of visual, auditory, and tactile input. Noninvasive measurement techniques were utilised and the subjects did not know that their breathing was being monitored. Measurement periods of only 5 min were used in order to avoid sleep. To estimate reproducibility, subjects were studied four times over two days. A variety of statistical tests on respiratory and cardiovascular variables indicate that the differences between individuals are highly significantly greater than the differences within an individual on repeated measurements under these standardised conditions. There was a high degree of reproducibility of breathing pattern within a subject; respiratory frequency was the most reproducible variable.
Adult↗
The effect of visual and auditory stimuli upon resting ventilation in man.
We have quantified the effect of visual, and auditory stimulation upon the breathing pattern in resting healthy man. Only noninvasive instrumentation was used. For the visual experiment we studied 36 subjects in each of three conditions: relaxed wakefulness with eyes closed (EC); with eyes open and directed at a white screen (EO); and whilst reading a standardised text (R). For the auditory experiment we studied 18 subjects under three analogous situations: no auditory input (N); listening to white noise (W); and listening to a story (V). In each study, all subjects underwent four replications (over two days) of one of the six permutations of the three experimental conditions; each condition lasted 5 min. A balanced analysis of variance on 10,368 breaths showed that, from baseline EC, both EO and R significantly increased respiratory frequency and ventilation by approximately 6%. Using 5184 breaths in the auditory study the analysis showed qualitatively similar results between analogous situations. The results demonstrate the importance of defining the conditions under which resting VI is measured.
Acoustic Stimulation↗
Arterial oxygen saturation and breathlessness in patients with chronic obstructive airways disease.
Nine patients with chronic obstructive airways disease performed a 6 min self-paced walk (breathing air) on a treadmill and then identical (but operator-controlled) treadmill walks breathing either air or supplemental oxygen sufficient to just prevent arterial oxygen desaturation during the exercise. During the exercises, ventilation was recorded and patients recorded their sensation of breathlessness on a visual analogue scale (VAS) every 30 s. Breathing supplemental oxygen produced a small fall in mean exercise ventilation and a large and consistent reduction in mean exercise breathlessness. In seven patients the VAS scores were higher on air than with supplemental oxygen, at similar levels of ventilation. An analysis of covariance, to control for reduction in ventilation, showed a decrease in mean breathlessness when breathing supplemental oxygen, significant at the 8% level. The reduction in breathlessness produced by preventing exercise desaturation cannot be explained by the decrease in ventilation. This suggests that hypoxia may be a stimulus for breathlessness. The mechanism is unknown.
Aged↗
Breathlessness and respiratory mechanics during reflex or voluntary hyperventilation in patients with chronic airflow limitation.
1. Six patients with chronic airflow limitation rebreathed CO2. Subsequently they voluntarily copied their stimulated breathing pattern while normocapnia was maintained. On a separate occasion four of these patients performed progressively increasing exercise and later copied these breathing patterns. 2. During all experiments flow, ventilation and pleural pressures were recorded. In addition, breathlessness was measured on a visual analogue scale every 30 s. 3. In these patients voluntary copying of either form of stimulated breathing resulted in diminished breathlessness and in some cases in complete abolition of the sensation, despite similar levels and patterns of ventilation in the two situations. 4. No systematic or consistent differences in the mechanics of breathing between stimulated and voluntarily copied breathing were found. 5. There was no correlation found between breathlessness score and any mechanical variable measured. 6. These results show that despite similarity in mechanics between stimulated and voluntary hyperventilation, the sensation of breathlessness is much diminished during the latter in these patients. This suggests that the sensation of breathlessness is more dependent upon the awareness of central processing than upon input from peripheral mechanoreceptors.
Aged↗
Voluntary isocapnic hyperventilation and breathlessness during exercise in normal subjects.
1. Nine normal subjects performed 6 min, constant-workload, exercise tests on a bicycle ergometer at either a 'high workload' or at a 'low workload'. During the first 'high workload' test their spontaneous breathing pattern was recorded on to magnetic tape. During one subsequent 'high workload' test and one 'low workload' test they voluntarily copied their recorded breathing pattern. During a second 'low workload' test they breathed spontaneously. Isocapnia was maintained by the operator throughout both the copying tests. During the exercise tests ventilation was recorded and subjects indicated the level of their sensation of breathlessness every 30 s. 2. Subjects felt markedly less breathless when a proportion of their ventilation was produced by voluntary effort than when the same total level of ventilation was produced entirely by the stimulus of exercise. Furthermore, voluntary isocapnic hyperventilation during exercise did not increase breathlessness above that normally associated with that level of exercise. 3. These results suggest that it is reflexly driven ventilation, and not simply the level of ventilation itself, which relates to the level of breathlessness during exercise.
Adult↗
Is hypercapnia necessary for the ventilatory response to exercise in man?
1. Continuous recordings of arterial pH, ventilation, airway CO2 and heart rate were made during rest and during 3-4 min periods of rhythmic leg exercise in four renal patients with arteriovenous shunts. 2. The patients were anaemic (haemoglobin 6.5-9.0 g/dl) but had a normal ventilatory response to exercise as judged by the ratio of the change in ventilation to the change in CO2 production. 3. Breath-by-breath oscillations in arterial pH disappeared for the majority of the exercise period in each patient. 4. Changes in mean arterial pH and end-tidal CO2 tension with exercise were inconsistent between subjects but consistent within a given subject. On average, mean arterial pH rose by 0.011 pH unit. Changes in end-tidal CO2 tension reflected changes in mean pHa by falling on average by 1 mmHg (0.13 kPa). 5. Hypercapnia and acidaemia were not found to be necessary for the ventilatory response to moderate exercise.
Adult↗
Is low-level respiratory resistive loading during exercise perceived as breathlessness?
1. The effect of adding low-level (2.7 cmH2O 1(-1) s) external respiratory resistive loads on exercise-induced breathlessness has been examined in naive normal subjects; the intensity of this loading was chosen to simulate that confronting an asthmatic subject during exercise. 2. Each of 18 subjects performed two separate tests in which workload was oscillated while the respiratory loading was changed every minute between no loading, inspiratory loading only, and inspiratory plus expiratory loading. Each loading condition was given three times, and both these changes and those in workload were unpredictable as far as the subject was concerned. 3. The purpose was to 'confuse' subjects and obtain subjective estimates of their intensity of breathlessness independent of any expectation associated solely with the readily perceptible changes in external resistances to breathing. The study design was balanced for the group as a whole, both in terms of workload and respiratory loading condition. 4. The addition of these respiratory resistive loads during exercise did not result in a significant increase in the intensity of breathlessness. 5. Estimates of the rate of work of breathing revealed that this increased more with respiratory loading than it did as ventilation rose throughout the test; on the other hand, the intensity of breathlessness increased by a greater extent with continued exercise compared with the changes accompanying the addition of respiratory loads. 6. It is concluded that the intensity of the sensation of breathlessness experienced by normal subjects during exercise is not simple a reflection of an increased rate of work of breathing being performed by the respiratory muscles.(ABSTRACT TRUNCATED AT 250 WORDS)
Adolescent↗
Validation of beat by beat pulsed Doppler measurements of ascending aortic blood velocity in man.
The volume, velocity, and acceleration of ascending aortic blood were measured in man using a pulsed Doppler ultrasound instrument, with online spectral analysis and offline computer processing of velocity data. This system was firstly validated in a test rig capable of generating pulsatile flow of talc particles in water at physiological velocities and accelerations in a model aorta. Doppler measurements correlated well (r greater than or equal to 0.90) with simultaneous electromagnetic measurements of stroke volume, peak ejection velocity, and maximum acceleration in this rig. In vivo validation was performed firstly by comparing simultaneous Doppler and thermodilution cardiac output (Q) measurements; this yielded the following regression equation: Doppler Q = 0.90 X thermodilution Q + 0.03 litre.min-1, r = 0.92; n = 38. Beat by beat measurements were then validated against simultaneous invasive aortic blood velocity measurements made using a Mills electromagnetic cathetertip probe. When paced single beats of different size were compared within subjects the correlation coefficients between Doppler and electromagnetic measurements averaged 0.89 for stroke volume, 0.91 for peak ejection velocity, and 0.79 for maximum acceleration in five subjects. The absolute values for velocity and acceleration from the Doppler system differed significantly from the absolute values given by the electromagnetic system and this difference was not consistent between subjects. It is concluded that the Doppler system can non-invasively record relative changes in left ventricular ejection in man.
Aorta↗
The early circulatory and ventilatory response to voluntary and electrically induced exercise in man.
1. The ventilatory and circulatory responses to electrically induced leg exercise (EEL) were studied in seven normal subjects and compared with the responses to performing the same exercise voluntarily (EV). 2. EEL was produced by surface electrode stimulation of the quadriceps and hamstring muscle groups. This produced a push-relax pattern of exercise against a spring load and was free of any pain or discomfort. EV, at the same level, was achieved by subjects copying a display of timing and force information on a storage oscilloscope. 3. Cardiac output was estimated using validated Doppler ultrasound measurements of the velocity in the ascending aorta, combined with an estimate of aortic cross-sectional area using M-mode echocardiography. 4. Data from EV and EEL exercise runs were matched, within subjects, for the increase in oxygen consumption during the first 30 s of exercise; there were no significant differences between the resting states prior to either form of exercise. 5. The first ten beats of exercise were used to study the circulatory on-transient. The cardiac output responses to both EV and EEL were similar; however, in EV alone there was an initial significant drop in stroke volume and a slightly greater rise in heart rate. 6. The first five breaths of the response were used to study the ventilatory on-transient, and by measuring cardiac output, stroke volume and heart rate throughout each breath, the relationship between circulatory and ventilatory variables could be assessed. Ventilation showed a significantly greater rise at the onset of exercise during EV than during EEL; PET,CO2 (end-tidal CO2 pressure) showed small but significant falls for both EV and EEL. 7. The circulatory changes on a breath-by-breath basis are similar for EV and EEL although the ventilatory changes differ. In both EV and EEL the average increase in ventilation at the onset of exercise is proportionally greater than the average increases in cardiac output. Individual exercise runs show no particular relationship between circulatory and ventilatory change. 8. The results provide no support in man during mild leg exercise for a 'cardiodynamic' drive to breathing.
Adult↗