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Biomedical subjects

M Lopata

Publications and source records attributed to M Lopata.

At least 55 records · Page 3Linked to original sources
PubMed1982

Periodic breathing and the pathogenesis of occlusive sleep apneas.

In order to study the relationship between sleep-induced periodic breathing and the development of occlusive sleep apneas, 6 patients with hypersomnia-sleep apnea syndrome were studied during nocturnal sleep before and approximately 1 month after therapeutic tracheostomy. Post-tracheostomy studies were performed in open and closed tracheostomy states. Sleep-induced periodic breathing resembling the pattern of Cheyne-Stokes breathing was observed in all patients before and after tracheostomy, even when tracheostomy was left open. When tracheostomy was closed all patients developed periodic hypopneas with significant oxygen desaturation, and 4 patients developed occlusive apneas at the nadir of the periodic changes. However, apnea and desaturation indexes during closed tracheostomy were significantly lower than their respective pretracheostomy values. These results indicate that sleep-induced periodic breathing, which represents an instability of respiratory control, is primary to the development of occlusive apneas, and the periodically observed is exaggerated by hypoxemia. Comparison of pre- and post-tracheostomy studies indicate a significant improvement in the underlying disorder most likely caused by the elimination of nocturnal hypoxemia and sleep fragmentation.

Cheyne-Stokes Respiration↗
PubMed1981

Diaphragmatic and genioglossal electromyogram responses to CO2 rebreathing in humans.

To assess the relationship between central control of upper airway and respiratory muscle, simultaneously recorded diaphragmatic electromyogram (EMGdi) and genioglossal EMG (EMG ge) responses to CO2 rebreathing were compared in five supine volunteers. Both EMGs were quantitated in terms of inspiratory peak moving time-average activity. In all subjects both EMGdi and EMGge increased linearly with increasing alveolar CO2 pressure (r = 0.93 +/- 0.04 and 0.87 +/- 0.07, respectively), resulting in a significantly linear EMGge vs. EMGdi relationship (r = 0.91 +/- 0.04). CO2 response slopes of both EMGs were similar and linearly related (r = 0.96, P less than 0.001) such that subjects with low EMGdi response also had a low EMGge response and vice versa. Although the onset of EMGge activity preceded that of EMGdi, and the pattern of both EMGs were different, inspiration duration of both EMGs were similar. These data indicate that in humans both diaphragm and genioglossus muscle share similar control mechanisms and suggest that upper airway function is intimately related to the regulation of breathing.

Adult↗
PubMed1981

Diaphragmatic and genioglossal electromyogram responses to isocapnic hypoxia in humans.

In order to define the relationship between central control of upper airway and respiratory muscle function, diaphragmatic electromyogram (EMGdi) and genioglossal EMG (EMGge) responses to isocapnic hypoxia were studied in 6 awake supine volunteers. Both EMGs were processed and quantitated as moving time average activity. In all subjects, EMGge showed phasic inspiratory activity synchronous with EMGdi. Increases seen in EMGdi and EMGge were linearly related to the decrease in oxygen saturation (r = 0.89 +/- 0.08 and 0.89 +/- 0.08, respectively). There was also a linear relationship between the relative responses of both EMGs to hypoxia such that a low EMGdi response was associated with a low EMGge response and vice versa (r = 0.92, p less than 0.001). These results indicated that the genioglossus muscle behaves like a respiratory muscle and suggested that central control of upper airway and respiratory muscles in humans are intimately related.

Carbon Dioxide↗
PubMed1981

Diaphragmatic EMG and transdiaphragmatic pressure measurements with a single catheter.

A single gastroesophageal catheter was used for simultaneous measurements of diaphragmatic electromyogram (EMGdi), esophageal, and gastric pressures in 10 normal volunteers. The catheter consisted of 2 polyethylene tubes, each with an outer diameter of 1.70 mm and an inner diameter of 1.19 mm, 2 platinum wire coils, and esophageal and gastric latex balloons. In all subjects studied, the increase in EMGdi, quantified as the average rate of rise of inspiratory moving average activity, and transdiaphragmatic pressure (Pdi) were linearly related to the increase in end-tidal PCO2 during CO2 rebreathing (range of r, 0.88 to 0.99 and 0.85 to 0.99, respectively). The relation between changes in EMGdi and that of Pdi, mean inspiratory flow, and occlusion pressure were also linear (range of r, 0.83-0.99, 0.73-0.99, and 0.84-0.99, respectively), indicating reliable recordings of EMGdi and Pdi during CO2 rebreathing in upright normal humans.

Carbon Dioxide↗
PubMed1980

Respiratory neuromuscular response to CO2 rebreathing with inspiratory flow resistance in humans.

The effects of inspiratory flow resistance on mouth occlusion pressure (P0.15) and diaphragmatic EMG (EMGdi) responses to CO2 rebreathing were studied in normal subjects. Occlusion pressures were measured 150 msec after onset of an inspiratory effect; EMGdi was analyzed as a moving time average and quantified in terms of peak activity and rate of rise of activity. After a control CO2 response was obtained in each subject, rebreathing was repeated 30 min later with either of two inspiratory flow resistive loads, 5 cm H2O/L/sec (IR5) and 14 cm H2O/L/sec (IR14). With IR5 (6 subjects), the P0.15 response was decreased in two subjects, unchanged in two, and increased in two; peak EMGdi was unchanged in all, while rate of rise of EMGdi response decreased in 4 of the 6 subjects. With IR14 (6 subjects, 9 runs), the P0.15 response was not decreased in any subject, remained unchanged in 4, and increased in 5; peak EMGdi response to rebreathing in all runs was, again, unchanged by this load, but rate of rise of EMGdi was decreased in 3 and unchanged in 6. The inspiratory off-switch threshold as reflected by peak diaphragmatic activity was not changed by inspiratory flow resistance, whereas inspiratory neural drive as reflected by the the rate of rise of activity was decreased in some subjects. The decrease in inspiratory drive without change in inspiratory off-switch threshold resulted in prolongation of inspiration in an attempt to effect efficient lung expansion. However, the defense of ventilation during rebreathing with both resistances appeared to mainly depend on the response of inspiratory muscle force (P0.15), since in 7 of the 7 runs in which the P0.15 response was significantly increased from control, the ventilatory response was not decreased.

Carbon Dioxide↗
PubMed1980

Diaphragmatic EMG and occlusion pressure response to elastic loading during CO2 rebreathing in humans.

The effects of external elastic loading (EL) (19 cmH2O/l), applied continuously (C) and intermittently (I) during CO2 rebreathing, on diaphragmatic electromyogram (EMGdi), mouth occlusion pressure (P0.15), and ventilation (VI) were studied in normal subjects. EMGdi was analyzed as moving time average and quantitated in terms of peak (mean p) and average rate of rise of inspiratory activity (mean p/TI). CEL resulted in an increased mean p/TI response to CO2 in all subjects with P0.15 increasing in proportion to EMGdi. Tidal volume (VT) during rebreathing was decreased in all cases with VI being preserved in four of six runs due to increased breathing frequency (f). Although mean p was increased for a given end-tidal CO2 (PACO2) level during CEL, for a given rate of rise of inspiratory activity mean p was decreased in three of five subjects, indicating a diminished threshold for inspiratory "off-switch." CEL results in an augmented inspiratory drive that serves to increase muscle output and stabilize VT; the increased drive and decrease inspiratory off-switch threshold shorten TI mediating the compensatory increase in f. The first breath IEL resulted in decreased VT and mean p without change in mean p/TI, and all increased with subsequent loaded breaths independent of changes in PCO2. Load compensation for externally applied EL is mediated by neural mechanisms independent of chemical drive.

Adult↗
PubMed1980

Respiratory failure due to Strongyloides stercoralis in a patient with a renal transplant.

We report a case of respiratory failure caused by Strongyloides stercoralis in a patient with a renal transplant; the respiratory failure showed dramatic response to therapy with thiabendazole. The clinical aspects of infestation with S stercoralis in the immunocompromised host are discussed, and features are demonstrated which may have significant implications concerning primary treatment and prophylaxis.

Humans↗
PubMed1979

Effects of electrode position on esophageal diaphragmatic EMG in humans.

The effects of electrode position and gastric-balloon anchoring on esophageal diaphragmatic EMG (EMGdi) responses to CO2 rebreathing were studied in seven normal sitting humans using an esophageal catheter that consisted of four platinum wire coils enabling simultaneous recording of three EMGdi signals from three different sites in the esophagus. A gastric balloon attached to the distal end of the catheter allowed anchoring of the catheter. EMGdi signals were quantitated as a moving time average. Two rebreathing experiments were performed with and without balloon anchoring on the same day. Changes in electrode position of at least 2 cm above the site of maximum EMGdi activity caused minimal changes in the moving average EMGdi and did not significantly effect the quantitated EMGdi response to CO2 rebreathing. The maximum EMGdi activity was approximately 2 cm above the gastroesophageal junction in sitting humans. Stabilization of the catheter with an inflated gastric balloon did not improve the reproducibility of the EMGdi data. Finally, the EMGdi response to two CO2 rebreathing runs done at the same sitting showed intraindividual reproducibility.

Carbon Dioxide↗
PubMed1978

Diaphragmatic EMG response to isocapnic hypoxia and hyperoxic hypercapnia in humans.

The EMGdi response to both isocapnic hypoxia and hyperoxic hypercapnia was studied in the same sitting in six normal subjects. Rebreathing methods achieving "open loop" conditions were used. EMGdi was quantified as a moving time average. In almost all subjects, during hypoxia changes in EMGdi were inversely and hyperbolically related to changes in PAO2. When EMGdi was plotted against extrapolated O2 saturation, the relationship was linear in all subjects. The EMGdi response to hypoxia was qualitatively similar to the concurrent responses VI and P.15. EMGdi was linearly related to PACO2 during CO2 rebreathing. The slopes of the EMGdi response to decreasing O2 saturation were positively correlated to the slopes of the EMGdi response to PACO2, so that subjects with a low hypoxic response also had a low CO2 response and vice versa. The couplings of neural to muscular and muscular to ventilatory events as assessed by the ratio of the slopes of EMGdi to P.15 and P.15 to VI, respectively, were similar for all subjects and were not related to the degree or type of chemostimulation. The following were our conclusions. (1) EMGdi can be used as an index of respiratory motoneuron drive during hypoxic or hypercapnic breathing in normal humans. (2) The relative degree of responsiveness to hypoxic and hypercapnia stimuli (chemosensitivity) appears to be similar in any given individual. (3) In normal subjects, changes in inspiratory muscle pressure and ventilation are proportionate to changes in inspiratory neural drive as assessed by EMGdi.

Adult↗
PubMed1977

Quantification of diaphragmatic EMG response to CO2 rebreathing in humans.

To determine a reliable quantitative method of measuring diaphragmatic EMG (EMGdi), electrical activity of the diaphragm was obtained via an esophageal electrode during CO2 rebreathing in 6 normal males and processed three different ways: 1) integration (area), 2) as a moving time average, and 3) as a moving time variance. Integrated activity was quantified in terms of total activity and inspiratory activity. In addition, average total activity and average inspiratory activity were calculated. Moving average and moving variance were analyzed in terms of rate of rise (slope) and peak activities. All integration parameters, except average inspiratory activity, were poorly correlated to changes in PCO2, minute ventilation, and inspiratory muscle force, during rebreathing. Moving average and variance responses to rebreathing were linear with high correlation coefficients, with the slope measures showing the overall best correlations. There was no significant difference between average and variance EMGdi parameters in their responses to rebreathing. Time-related quantification of EMGdi, including average inspiratory activity, and particularly moving average and moving variance, appear to be reliable methods for quantitating neural drive to the respiratory muscles during CO2 rebreathing.

Carbon Dioxide↗
PubMed1977

Effects of flow-resistive loading on mouth occlusion pressure during CO2 rebreathing.

To evaluate mouth occlusion pressure as an index of neural drive to the respiratory muscles that is independent of lung mechanics, the occlusion pressure response to rebreathing was studied in 7 normal subjects under control conditions and during flow-resistive loading. Inspiratory, expiratory, and combined inspiratory-expiratory flow resistances of 5 and 17 cm H2O per liter per sec were studied in 7 normal subjects. Pressure at the mouth was measured 150 msec after the onset of inspiration against the occluded airway. In all subjects, the ventilatory response to CO2 rebreathing was consistenly decreased by the 3 types of resistive loads, and this decrease was often greater with the higher load. In contrast, the occlusion pressure response was usually increased with inspiratory and inspiratory-expiratory resistance, indicating increased inspiratory muscle output due to these loads. With expiratory resistance, the occlusion pressure response was decreased in most of the subjects, suggesting a decrease in muscular output with expiratory loading. The inspiratory muscle pressure response to resistive loading could have been mediated by neural reflex and/or intrinsic muscle mechanisms. Occlusion pressure, therefore, appears to reflect over-all inspiratory neuromuscular output of the respiratory system during CO2 rebreathing, even with the addition of flow-resistive loads. Measures of mouth occlusion pressure provide a distinct advantage over ventilatory parameters in studies of respiratory control mechanisms during mechanical loading.

Adult↗
PubMed1977

Relationship between mouth occlusion pressure and electrical activity of the diaphragm: effects of flow-resistive loading.

We determined the relationship between mouth occlusion pressure and diaphragmatic electromyography during CO2 rebreathing with and without inspiratory flow resistance. Diaphragmatic electromyography was measured as a moving time average; occlusion pressures were measured 150 msec after onset of an inspiratory effort against a closed airway (P.15). P.15 versus diaphragmatic electromyographic plots during CO2 rebreathing with and without inspiratory flow resistance were linear. In 3 subjects the slope of P.15 versus diaphragmatic electromyography was unchanged with inspiratory flow resistance whereas in 3 others the slope increased, indicating greater inspiratory force for a given degree of diaphragmatic activity. We concluded that under unloaded conditions P.15 is a reliable index of respiratory neural output but may no longer reflect only inspiratory motoneuron drive during mechanical loading.

Carbon Dioxide↗
PubMed1977

Nodular pulmonary sarcoidosis. Clinical, roentgenographic, and physiologic course in five patients.

Five cases of nodular pulmonary sarcoidosis are presented. That nodular infiltration represents a reversible stage of sarcoidosis is suggested by the fact that all patients demonstrated roentgenographic resolution of these infiltrates. In four of the five subjects, tests of pulmonary function showed restrictive disease which remained unchanged or worsened despite radiologic clearing, suggesting persistence of active disease or development of residual pulmonary fibrosis. Evidence of obstruction of airways that was unexplained by a history of smoking was present in all of the five subjects.

Adult↗