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Biomedical subjects

M D Altose

Publications and source records attributed to M D Altose.

At least 55 records · Page 3Linked to original sources
PubMed1985

Assessment and management of breathlessness.

Breathlessness is a common symptom in patients with respiratory disorders and contributes significantly to functional disability. Recent studies of the psychophysics of respiratory sensation suggest that dyspnea is a function of the forces generated by the respiratory muscles during the act of breathing and may simply represent the intensity of the sense of effort arising from central respiratory motor command signals. It is important to recognize the multidimensional nature of respiratory sensations that include not only sensory aspects but also affective and cognitive components. At present there are no established satisfactory means of treating dyspnea. Efforts to minimize abnormalities in ventilatory system impedance are limited by the largely irreversible nature of most chronic lung diseases. Sedatives and narcotic agents have not proved to be effective in altering perceptual responses and may have an adverse effect, worsening respiratory failure. Physical measures to improve overall conditioning and respiratory muscle performance may be most effective in relieving breathlessness and improving exercise capacity in patients with chronic lung disease.

Carbon Dioxide↗
PubMed1984

Effects of expiratory threshold loading on thoracoabdominal motion in cats.

Expiratory muscle activity may alter rib cage and abdominal configuration at end-expiration and thereby affect the pattern of thoracoabdominal motion during subsequent inspiration. In this study, expiratory muscles were stimulated by the application of a series of expiratory threshold loads (ETL) (range: 0 to + 10 cm H2O) in 10 cats lightly anaesthetized with pentobarbitone. Thoracoabdominal motion was monitored by inductance plethysmography. Peak internal intercostal and abdominal muscle electrical activity increased proportionately with the magnitude of the ETL, suggesting comparable activation of both expiratory muscle groups. Increases in end-expiratory abdominal volume, however, were greater than increases in end-expiratory rib cage volume, during ETL. This resulted in a shift of the end-expiratory thoracoabdominal position to the right of the relaxation characteristic. During ETL, there was inward movement of the abdomen in early inspiration and this decrease in abdominal volume correlated closely with the change in end-expiratory abdominal volume and the magnitude of the ETL (mean r = 0.95, P less than 0.01). In three animals, sectioning the abdominal muscles resulted in a further increase in end-expiratory abdominal volume for a given ETL. Deepening anesthesia progressively reduced and eventually abolished expiratory muscle activation and under these conditions, ETL increased end-expiratory rib cage and abdominal volume along the thoracoabdominal relaxation characteristic. The results of this study indicate that while abdominal muscle activation acts to decrease abdominal volume at end-expiration, the action of the expiratory intercostal muscles predominates during ETL to produce a smaller rib cage volume at the expense of an enlargement of abdominal volume.

Abdomen↗
PubMed1984

Sensation of respiratory force following low cervical spinal cord transection.

The psychophysical technique of magnitude scaling was used to assess the sensation of respiratory muscle force in patients with low cervical spinal cord transection. The exponents of the power function relationship between load magnitude and sensation intensity during graded elastic and resistive ventilatory loading in the quadriplegic patients were 0.51 and 0.54, respectively. These values were significantly lower than those in normal subjects (P less than 0.05). This impairment in load sensation could not be attributed to differences in either the duration or magnitude of the forces generated by muscles of inspiration during loading, since the power function relationships between airway pressure and sensation intensity corrected for inspiratory duration were also significantly lower in the quadriplegic patients compared with the normal subjects. In contrast the perception of respiratory force during inspiratory maneuvers against a closed airway, as determined by both magnitude estimation and production tests, was the same in normal subjects and quadriplegics. These results suggest that afferent signals from rib cage receptors are important in shaping the intensity of the sensation during submaximal ventilatory loading. During maximal loading, i.e., airway occlusion, when respiratory muscle tension changes proportionally with the motor command, centrally generated efferent command signals may be employed to subserve the sensation of respiratory muscle force when inputs from rib cage muscle receptors are not available.

Adult↗
PubMed1984

Oxygen saturation during breath-holding and during apneas in sleep.

The rate of fall in oxygen saturation is said to be greater during obstructive apneas than during breath-holding in wakefulness. Using an ear oximeter, a face mask and flowmeter, and measurements of thoracoabdominal motion, we determined in six healthy subjects the rate of fall in arterial oxygen saturation (SaO2) during breath-holding which simulated obstructive and nonobstructive apneas. Breath-holding maneuvers were performed during progressive isocapnic hypoxia and were initiated at the same end-expiratory thoracoabdominal configuration. We found that at any given initial SaO2 the rate of fall in SaO2 was similar during simulated obstructive (y = 5.5-0.06 x; r = 0.83) and nonobstructive (y = 6.8-0.07 x; r = 0.92) apneas. In two healthy subjects and 13 patients with obstructive and nonobstructive apneas during sleep, the rate of fall in SaO2 at any initial SaO2 was similar to that found in healthy subjects during breath-holding in wakefulness. We conclude that during wakefulness the presence or absence of respiratory efforts does not affect the rate of fall in SaO2 during breath-holding and that the rate of fall of SaO2 during sleep apnea is largely dependent on the initial SaO2 at the onset of apnea.

Adult↗
PubMed1984

The flow-volume loop during glossopharyngeal breathing.

The flow-volume loops of three patients with chronic poliomyelitis were examined during glossopharyngeal breathing and compared with those during forced vital capacity maneuvers using only chest wall muscles. Peak expiratory flow rates and vital capacities were greater in all subjects after inspiration using glossopharyngeal breathing. During glossopharyngeal breathing, there was a progressive fall in the inspiratory flow rate and volume of each stroke as pulmonary volume increased.

Adult↗
PubMed1983

Effects of an increase in end-expiratory volume on the pattern of thoracoabdominal movement.

Changes in end-expiratory lung volume can alter the mechanical function of the muscles of inspiration and may affect the pattern of thoracoabdominal movements. The present study examined the effect of increasing end-expiratory lung volume on the motion of the rib cage and abdomen during inspiration. In six seated subjects, end-expiratory volume was increased by expiratory threshold loading. The end-expiratory thoracoabdominal configuration shifted to the left of the relaxation curve presumably as a result of the activation of the abdominal expiratory muscles. There was outward displacement of both the rib cage and the abdomen with inspiration at the elevated volume but the relative volumetric contribution of abdominal displacement to the inspired volume was significantly less than during breathing from FRC. When at an enlarged lung volume subjects were constrained to initiate inspiration from a point on the thoracoabdominal relaxation configuration, there was inward movement of the abdomen and a decrease in abdominal dimensions during inspiration. Inward abdominal movement occurred despite large increases in diaphragm electrical activity and was associated with an inspiratory fall in gastric pressure. These results suggest that at large lung volumes, the function of the diaphragm as an agonist is lost and its function as a fixator may be impaired unless there is an activation of the abdominal muscles and the diaphragm is appropriately lengthened.

Abdomen↗
PubMed1983

Effects of aging on sensation of respiratory force and displacement.

The psychophysical technique of magnitude production was used to evaluate the sensation of inspiratory force and inspired volume in young and older subjects. Inspiratory force was generated during a static inspiratory maneuver against a closed airway. The exponent of the power function relationship between airway pressure and sensation intensity during force scaling was not significantly different between young and older subjects. In contrast, the exponents for the magnitude production of inspired volume were significantly greater in the older compared with the young group. We also assessed the effects of age on the relative importance of force and displacement signals on the sensation of inspired volume. Subjects attempted to reproduce a control tidal volume while breathing against a series of inspiratory resistive and elastic loads. In both groups error in tidal volume reproduction increased progressively as the severity of the load increased. During moderate and severe loading the error in the older subjects was significantly greater than in the young group. Correspondingly, the peak inspiratory airway pressures at tidal volume reproduction against these loads were significantly smaller in the older compared with the young subjects. The results suggest that in older subjects cues related to respiratory muscle force are more important than volume in the sensation of lung volume changes. In young subjects the sensation of lung volume changes is based to a greater degree on signals of volume or displacement.

Adult↗
PubMed1983

Effect of histamine on respiratory chemosensitivity in conscious goats.

The effect of histamine on occlusion pressure and electrical activity of the diaphragm was studied in 5 conscious goats under conditions of changing respiratory drive by exposing the animals in separate trials to progressive hypercapnia produced by rebreathing technique. Both electrical activity of the diaphragm and occlusion pressure increased with hypercapnia. At any level of PCO2, occlusion pressure and diaphragm electrical activity were greater after histamine than in the control state at the same level of chemical stimulation. Both parameters changed proportionally, and a linear correlation was found between them (r greater than 0.9). These results in conscious unsedated animals indicate that (1) histamine causes an increase of inspiratory neuromuscular drive, and (2) occlusion pressure satisfactorily indicates changes in respiratory neuron motor output.

Animals↗
PubMed1983

Effect of respiratory loading on the relationship between occlusion pressure and diaphragm EMG during hypoxia and hypercapnia.

In 7 conscious, unsedated goats with chronically implanted diaphragm electrodes, the effect of respiratory loading on the relationship between occlusion pressure and diaphragm EMG was studied. Diaphragm electrical activity (ED) quantified by the moving average technique was measured in separate trials during progressive hyperoxic hypercapnia and progressive isocapnic hypoxia, both before and after inspiratory resistance had been increased by externally applied loads. Airway occlusion was performed during inspiration on random breaths at functional residual capacity, and the maximum negative pressure (Pmax) was measured. In all 7 goats, occlusion pressure was greater with external loads (EL) than control. The peak ED of unoccluded breaths was greater with EL than control in all animals during hypoxia but in only 3 of the animals during hypercapnia. In half of the trials, the ratio of Pmax to ED of occluded or unoccluded breaths was higher with EL than control. In the remaining studies, the ratio was the same. FRC was unaffected by EL. In the one goat in which it was measured, intercostal EMG was also greater during EL than control. These results suggest that the inspiratory muscles other than the diaphragm are recruited during EL causing the Pmax to ED ratio to rise even if neuromechanical coupling remains unchanged. It is speculated that in conscious, unsedated animals, acute increases in the resistance to air flow affect the distribution of respiratory motor activity.

Animals↗
PubMed1983

Physician knowledge in the use of canister nebulizers.

The knowledge and skills of physicians were evaluated regarding some practical details of the usage of bronchodilators administered by canister nebulizers to determine the need for specific physician instruction in the correct usage. Fifty-five house officers and nonpulmonary attending staff from the Department of Medicine were interviewed individually. Each physician was handed a placebo canister and asked a series of standard questions regarding the recognition, assembly, and correct inhalation technique of the device. Correct assembly of the device was performed by 68 percent and 36 percent of house officers and attending staff, respectively. Only 40 percent of the participants correctly performed more than four of the seven steps felt to constitute a correct inhalation maneuver. The results reveal inadequacies in physicians' knowledge of the correct technical usage of canister nebulizers and suggest that greater attention be paid to instructing physicians in the correct inhalation technique if their role in patient education is to be effectively realized.

Aerosols↗
PubMed1982

Upper airway and diaphragm muscle responses to chemical stimulation and loading.

Previous studies suggest that upper airway muscles in humans respond to changes in chemical respiratory drive in a fashion similar to the diaphragm. To test this hypothesis, in nine seated healthy subjects we monitored electromyographic (EMG) activity from the alae nasi (AN), genioglossus (GG), and diaphragm (DI) not only in response to progressive isocapnic hypoxia and hyperoxic hypercapnia but also to hyperoxic hypercapnia with and without an external inspiratory resistance (15 cmH2O X 1(-1) X s). There were linear increases in DI, GG, and AN in response to increasing chemical drive, but the AN in one subject and the GG in another subject did not respond to hypoxia or hypercapnia. In response to an inspiratory load, subjects decreased ventilation (P less than 0.01) and increased AN, GG, and DI EMG activity (P less than 0.05); however, one subject did not show an AN response to either increased chemical drive or ventilatory loading. We conclude that muscles of the upper airway and the diaphragm are generally activated in a parallel fashion as respiration is stimulated by hypoxia, hypercapnia, and increased inspiratory resistance.

Adult↗
PubMed1982

Sensation of inspired volume in normal subjects and quadriplegic patients.

To investigate the influence of respiratory muscle tension and feedback from rib cage receptors, the sensation of inspired volume was compared in normal subjects and quadriplegic patients during active breathing, with and without the addition of an inspiratory resistive load, and during passive ventilation produced by a tank respirator. In separate trials, volume sensation was assessed using tests of magnitude estimation and volume reproduction. The mean exponents and standard errors for the magnitude estimation of inspired volume in normal subjects were 1.32 +/- 0.08, 1.24 +/- 0.06, and 1.23 +/- 0.09 during passive, active, and loaded breathing, respectively. These values were not significantly different from one another, nor were there any differences between normal subjects and quadriplegics. During volume reproduction trials where the mechanical conditions were different between control and test breaths, the inspired volumes during active unloaded breathing were significantly smaller than during passive ventilation but greater than the inspired volumes during loaded breathing. Errors in volume reproduction were no different in normal subjects and quadriplegics, suggesting that inputs from rib cage receptors are not essential for the sensation of inspired volume. The sensation of inspired volume in both normal subjects and quadriplegics was found to be unaffected by inhalation of a 2% lidocaine solution. This suggests that upper airway receptors are also not essential for volume sensation. The intensity of the sensation of a given inspired volume may depend on the level of the central nervous system motor command and/or on the tension developed by the diaphragm.

Adult↗
PubMed1982

Effect of aging on the perception of resistive ventilatory loads.

We have shown previously, using the technique of magnitude estimation, that the change in sensation level for a given change in elastic loading is less in elderly than in young subjects. In the present study, we used the same technique to compare the perception of added inspiratory and expiratory resistive loads in 40 young (18 to 30 yr of age) and 19 elderly (60 yr of age and older) subjects. Two different ranges of loads were studied and the relation between load magnitude and sensation intensity (the exponent for magnitude estimation) was determined. The study showed that the exponent for both inspiratory and expiratory loads is less in the older group. Because peak airway pressure and the inspiratory and expiratory times while breathing against the added loads were the same in both age groups, the difference in exponents in the two groups was not caused by differences in the forces generated during breathing. Age-related changes in sensory perception may affect behavioral responses to impaired respiratory mechanics.

Adolescent↗
PubMed1982

The sensation of respiratory muscle force.

The sensation of respiratory muscle force was examined in 8 normal subjects using the direct scaling method of magnitude production. At the end of a normal expiration, at functional residual capacity (FRC), subjects generated an inspiratory effort against a closed airway to produce a force that correspond to specific numerical values for sensation magnitude. Thereafter, at lung volumes of 2 L above FRC and 1 L below FRC, subjects attempted to reproduce the same force as that previously generated at FRC. Diaphragm electromyographic activity, recorded with an esophageal electrode, was used as a measure of central respiratory motor output. The difference between the mouth pressure during relaxation against a closed shutter and the peak airway pressure during the static inspiratory maneuver (Pmus) was employed as an index of muscle tension. The exponent for the magnitude production of force during maneuvers at FRC, i.e., the slope of the line relating log airway pressure and log sensation magnitude was 1.60 +/- SE 0.15. The exponent for force scaling was 1.47 +/- SE 0.17 after correcting for differences in inspiratory duration during maneuvers of different force. During inspiratory maneuvers at FRC plus 2 L, diaphragm EMG was 441 +/- SE 70%, but Pmus was 111 +/- SE 11% of the respective values during subjectively equal efforts at FRC. During inspiratory maneuvers at FRC minus 1 L, diaphragm EMG was 54 +/- SE 5%, but Pmus was 94 +/- SE 4% of the respective values during efforts at FRC perceived to be of equal force. These results suggest that the sensation of respiratory muscle force depends primarily on signals related to the tension generated by the contracting muscles rather than on the sensation of innervation associated with the central nervous system motor command.

Adult↗
PubMed1981

Perception of changes in breathing in normal human subjects.

Respiratory sensation was evaluated in normal subjects from their ability to quantitate changes in tidal volume. Subjects attempted to duplicate or double tidal volumes of different sizes while breathing freely or against a resistive or elastic load. When the mechanical conditions during control and test breaths were constant, tidal volume duplication was accomplished with an error of approximately 100 ml, regardless of the control volume. The error in doubling, however, increased progressively with increasing control tidal volume. There was a greater error in both volume duplication and doubling when the mechanical conditions between control and test breaths were changed. When test breaths against a load followed unloaded control breaths, tidal volume failed to double, but intrathoracic pressure changes twice exceeded control values. Conversely, when unloaded test breaths followed loaded control breaths, pressure changes underwent less than a twofold increase while tidal volume more than doubled. The results indicate that tidal volume changes are normally sensed with considerable accuracy and suggest that both tidal volume per se, as well as the forces generated by the respiratory muscles, are used in the estimation of tidal volume changes.

Adult↗