Beta-agonists and death from asthma.
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Adrenergic beta-Agonists↗
Biomedical subjects
B R Celli
Publications and source records attributed to B R Celli.
Respiratory input impedance from 4 to 256 Hz in normals and chronic airflow obstruction: comparisons and correlations with spirometry.
Measurement of respiratory system input impedance (Zrs) by forced oscillation (FO) has generally been limited to frequencies less than or equal to 50 Hz, and correlations with spirometry have been variable. Using FO from 4 to 256 Hz in normals, Jackson and colleagues recently described a first acoustic antiresonance frequency (Far,1) at approximately 170 Hz. Using the same frequency range, we compared several Zrs spectral characteristics with spirometry in 12 chronic airflow obstruction (CAO) patients (range FEV1 0.8 to 2.0 L) and 10 matched controls. Compared with controls, patients had a higher first resonance frequency (Fr,1) (mean +/- SD = 15 +/- 5 versus 10 +/- 2 Hz, p less than 0.02) and a higher Far,1 (196 +/- 11 versus 172 +/- 13 Hz, p less than 0.0002). Good correlations occurred between % predicted FVC and the Far,1 (r = -0.81, p less than 0.0000), between FEV1/FVC and the reactance at 20 Hz (r = -0.6, p less than 0.003), between FEV1 and Far,1 (r = -0.74, p less than 0.0001). Because Far,1 may be affected by airway wall mechanical properties, the shift in Far,1 seen in these patients may be due to airway wall properties in CAO. We conclude that measurement of Zrs up to 256 Hz requires little patient cooperation and may be clinically useful. It can differentiate CAO patients from controls and correlates well with spirometry. The first acoustic antiresonance frequency may reflect airway mechanical properties and provide information not available from Zrs measured at lower frequencies.
Airway Resistance↗
Improved diaphragmatic function after surgical plication for unilateral diaphragmatic paralysis.
We studied pulmonary function tests, maximal voluntary ventilation, arterial blood gases, and respiratory muscle strength and recruitment pattern in a 37-yr-old symptomatic man before and after surgical plication for a left unilateral diaphragmatic paralysis. After plication, FVC, FEV1, TLC and FRC increased, whereas residual volume remained unchanged. Arterial PO2 improved from 70 to 87 mm Hg. Diaphragmatic strength, as expressed by the maximal transdiaphragmatic pressure increased from 30 to 75 cm H2O, and maximal voluntary ventilation increased from 74 to 123 L/min. Ventilatory muscle recruitment also changed: there was a shift from a positive to a negative delta Pg/delta Ppl slope during tidal breathing. This indicates more effective diaphragmatic recruitment after the procedure. We conclude that surgical plication may be of benefit to patients with symptomatic unilateral diaphragmatic paralysis. The improvement is due to improved respiratory muscle function.
Adult↗
Respiratory response and ventilatory muscle recruitment during arm elevation in normal subjects.
Despite the fact that the arms are used extensively in daily life and that some of the muscles of the shoulder girdle share both a respiratory and a positional function for the arms, surprisingly little is known about the respiratory response to unsupported upper extremity activity. To determine the respiratory consequences of simple arm elevation during tidal breathing, we measured minute ventilation (VE), tidal volume (VT), respiratory rate (f), heart rate (HR), oxygen uptake (VO2), and carbon dioxide production (VCO2) in 22 normal subjects seated with arms elevated in front of them to shoulder level (AE) for 2 min and down at the sides (AD) for the same time period. The sequence was randomized. Compared with AD, during AE there were significant increases in VO2 (336 +/- 18 vs 289 +/- 14 ml/min, p less than 0.001), VCO2 (315 +/- 23 vs 245 +/- 16 ml/min, p less than 0.001), HR (84 +/- 6 vs 73 +/- 4 beats/min, p less than 0.05), VE (11.5 +/- 0.9 vs 9.3 +/- 0.6 L/min, p less than 0.001), and VT (868 +/- 66 vs 721 +/- 48 ml, p less than 0.001). In 11 subjects, breath-by-breath metabolic and ventilatory parameters were studied with AD for 2 min, AE for 2 min, and with AD for 3 min while also recording gastric (Pg), pleural (Ppl), and transdiaphragmatic pressures (Pdi). With AE, there was a significant increase in Pg at end inspiration (PgI, 15.4 +/- 3.2 vs 11.9 +/- 2.7 cm H2O, p less than 0.01) and in Pdi (26.5 +/- 3.4 vs 21.4 +/- 2.4 cm H2O, p less than 0.01) with no change in Pg at end expiration (PgE) or in Ppl. The increases in VO2, VCO2, VE, and VT during arm elevation persisted for 2 min after arm lowering, whereas Pgi and Pdi abruptly dropped as the arms were lowered. We conclude that simple arm elevation during tidal breathing results in significant increases in metabolic and ventilatory requirements. These increased demands are associated with higher PgI and Pdi suggesting an increased diaphragmatic contribution to the generation of ventilatory pressures. The sudden drop in Pg with arm lowering indicate a change in ventilatory muscle and or torso recruitment independent of the metabolic drive and ventilatory needs. These findings may help explain the limitation that has been reported in some normal subjects and in many patients with lung disease during unsupported upper extremity activity.
Adult↗
Respiratory response to arm elevation in patients with chronic airflow obstruction.
We have shown that patients with chronic airflow obstruction (CAO) complain of disabling dyspnea when performing seemingly trivial tasks with unsupported arms. Surprisingly little is known about the metabolic and ventilatory responses to unsupported upper extremity activity even though some of the muscles of the upper torso and shoulder girdle are used to perform simple and complex everyday tasks as well as partake in ventilation. To determine the effect of simple arm elevation in 20 patients with CAO we studied their lung function, VO2, VCO2, and VE, with arms down at the side (AD), during 2 min with arms extended forward up to shoulder level (AE), and during recovery. To determine the pattern of ventilatory muscle recruitment we also measured endoesophageal (Ppl), gastric (Pg), and transdiaphragmatic (Pdl) pressures. In five of the patients the electromyographic signal (EMG) of the sternocleidomastoid (Sm) muscle was recorded and analyzed in its time domain (amplitude) and power spectrum density (median frequency). Within 30 s of arm elevation VO2, VCO2, and VE rose and remained elevated for 1 min after the arms were lowered. The increase in VE resulted from increases in respiratory rate and minimal rise in tidal volume (VT). With AE, FEV1 decreased by 5% (p less than 0.02) but FRC increased by 2% (p less than 0.05). Peak inspiratory pressure (Pimax) dropped from 54 +/- 4 to 48 +/- 4 cm H2O (p less than 0.005); Pdimax remained unchanged. Immediately after raising the arms Pgi, inspiratory swing in Pdi (delta Pdi), end-expiratory Ppl, and end-expiratory Pg increased significantly.(ABSTRACT TRUNCATED AT 250 WORDS)
Aged↗
Factors influencing ventilatory muscle recruitment in patients with chronic airflow obstruction.
Patients with chronic airflow obstruction (CAO) frequently develop abnormal thoraco-abdominal excursion, but the patterns described are inconsistent and the factors that relate to their development remain unknown. We studied 45 stable patients with FEV1 ranging from 0.36 to 2.1 L. A pattern of ventilatory muscle recruitment (VMR) was established by simultaneously measuring gastric (Pg) and pleural (Ppl) pressures and rib cage (Vrc) and abdominal (Vab) volume displacement with inductance plethysmography. From these tracings, Pg-Ppl plots were constructed and the delta Pg/delta Ppl values were calculated. The delta Pg/delta Ppl was validated in 15 patients with simultaneous analysis of Vab-Pg plots. Pearson's test and multiple regression analyses were used to correlate delta Pg/delta Ppl to factors thought to influence respiratory muscle function such as age, sex, nutritional status (weight/height, albumin), hyperinflation, airflow obstruction, and arterial blood gases. We found a direct correlation between a more positive delta Pg/delta Ppl value and increasing hyperinflation (r = 0.69, p less than 0.0001), increasing airflow obstruction (r = -0.55, p less than 0.001), and decreasing diaphragmatic strength (r2 = 0.32, p less than 0.001). We also found that expiratory Ppl became more positive with decreasing FEV1 (r2 = 0.33, p less than 0.001). This change in VMR was independent of age, sex, nutritional status, and arterial blood gas determinations.(ABSTRACT TRUNCATED AT 250 WORDS)
Aged↗
Correlations between dyspnea, diaphragm and sternomastoid recruitment during inspiratory resistance breathing in normal subjects.
The purpose of this study was to determine the relationship between recruitment of the DI and SM muscles measured as EMG signal amplitudes, the pattern of respiratory muscle recruitment measured with inductive plethysmography, and the intensity of the sensation of dyspnea, measured with 100 mm VAS. Eighteen normal subjects between the ages of 33 and 47 breathed under two conditions: normal controlled breathing and breathing against an inspiratory resistance at 60 percent of their maximal inspiratory pressure (MIP). The PM, RR, duty cycle (TI/TTOT, and VT were held constant. During resistance breathing, VAS dyspnea was increased when EMG-DI decreased; EMG-SM increased in association with the sensation of dyspnea. During inspiratory resistance breathing, dyspnea markedly increased and rib cage and accessory muscle recruitment was the predominant pattern of breathing. These data suggest that dyspnea may be associated with the recruitment of the accessory respiratory muscles rather than the recruitment of the diaphragm.
Adult↗
Hypothyroidism. A reversible cause of diaphragmatic dysfunction.
The presence of a peripheral myopathy in hypothyroidism has been well recognized. Involvement of the diaphragm has been suggested recently but the clinical spectrum never clearly defined. We studied three patients with hypothyroidism presenting with fatigue, dyspnea, exercise limitation, and in two, chronic alveolar hypoventilation (PaCO2 of 51 and 75 mm Hg) before and after thyroid hormone replacement. In all patients diaphragmatic strength as determined by the maximal transdiaphragmatic pressure was low (2, 13, and 64 cm H2O) and improved with therapy (86, 84, and 90 cm H2O). Similarly, all patients manifested a fatiguing breathing pattern, as determined by the diaphragmatic tension time index. These values (0.22, 0.55, and 0.36) decreased after hormone replacement (0.16, 0.20, and 0.15). These changes were associated with the correction of hypercarbia in the two patients with hypoventilation and an improvement in lung volumes and exercise endurance in all patients. This study confirms that in patients with hypothyroidism diaphragmatic dysfunction occurs more frequently than has been suspected and might be of varying severity. This dysfunction reverses with adequate hormone replacement.
Diaphragm↗
Clinical and physiologic evaluation of respiratory muscle function.
The ventilatory muscles are of primary importance in the maintenance of ventilation. This rather complex system of muscles centers around the diaphragm. As diaphragmatic function becomes compromised with the progression of different lung diseases, the participation of other muscles becomes necessary. This is clinically manifested by the recruitment of many of these muscles even during quiet breathing. The use of simple questions during a medical history, determination of the respiratory rate, assessment of the pattern of breathing, and observation of thoracoabdominal movements are helpful in the initial evaluation. Measurement of the FVC, lung volumes, and tidal breathing help direct attention to more specific investigation of the ventilatory muscles. Decreased respiratory muscle strength can be confirmed by measurement of PImax and PEmax. Decreased respiratory muscle endurance can be readily ascertained by measuring the MVV. Use of these simple techniques, available in most laboratories, is appropriate for initial evaluation and establishing a diagnosis. The additional measurements of esophageal and gastric pressures have added a new dimension to the study of the diaphragm; these techniques, however, remain a research tool.
Humans↗
Effect of unsupported arm exercise on ventilatory muscle recruitment in patients with severe chronic airflow obstruction.
We have proposed that unsupported arm exercise alters ventilatory muscle recruitment and precipitates dyspnea in patients with severe chronic airflow obstruction (CAO). To test this hypothesis, we studied 11 patients with CAO during symptom-limited, unsupported arm exercise (UAE) and compared it with supported arm cycling (SAE). During each exercise period, we recorded endoesophageal (PpI), gastric (Pg), and transdiaphragmatic (Pdi) pressures along with heart rate, respiratory rate, and endurance time. Expired gas was collected to determine oxygen uptake (VO2) and minute ventilation (VE). Exercise endurance was shorter for UAE than for SAE (210 +/- 114 versus 270 +/- 120 s, p less than 0.05), even though peak exercise heart rate (113 +/- 5 versus 122 +/- 7 beats/min, p less than 0.05), VO2 (5.9 +/- 0.5 versus 7.1 +/- 0.8 ml/kg/min, p less than 0.05) and VE (16.5 +/- 1.2 versus 19.8 +/- 1.3 L/min, p less than 0.05) were lower for UAE. Mean (+/- SD) values for changes in pleural (delta PpI) and gastric (delta Pg) pressures during either type of arm exercise were significantly greater than at rest (p less than 0.02). In eight of 11 patients during UAE, the changes between end-inspiratory and end-expiratory transdiaphragmatic pressure (delta Pdi) were observed to develop in a similar pattern. In these patients, end-inspiratory Pg was more positive and end-inspiratory PpI was less negative during UAE than during SAE (p less than 0.02). In addition, PpI at end expiration was markedly positive when performing UAE (p less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Nosocomial pneumonia in intubated patients given sucralfate as compared with antacids or histamine type 2 blockers. The role of gastric colonization.
Gram-negative nosocomial pneumonia may result from retrograde colonization of the pharynx from the stomach, and this may be more likely when the gastric pH is relatively high. We studied the rate of nosocomial pneumonia among 130 patients given mechanical ventilation in an intensive care unit who were receiving as prophylaxis for stress ulcer either sucralfate (n = 61), which does not raise gastric pH, or conventional treatment with antacids, histamine type 2 (H2) blockers, or both (n = 69). At the time of randomization to treatment, the two groups were similar in age, underlying diseases, and severity of acute illness. Patients in the sucralfate group had a higher proportion of gastric aspirates with a pH less than or equal to 4 (P less than 0.001) and significantly lower concentrations of gram-negative bacilli (P less than 0.05) in gastric aspirates, pharyngeal swabs, and tracheal aspirates than did patients in the antacid-H2-blocker group. The rate of pneumonia was twice as high in the antacid-H2 group as in the sucralfate group (95 percent confidence interval, 0.89 to 4.58; P = 0.11). Gram-negative bacilli were isolated more frequently from the tracheal aspirates of patients with pneumonia who were receiving antacids or H2 blockers. Mortality rates were 1.6 times higher in the antacid-H2 group than in the sucralfate group (95 percent confidence interval, 0.99 to 2.50; P = 0.07). Although our results fell just short of statistical significance when they were analyzed according to intention to treat, they suggest that agents that elevate gastric pH increase the risk of nosocomial pneumonia in patients receiving ventilation by favoring gastric colonization with gram-negative bacilli. We conclude that in patients receiving mechanical ventilation, the use of a prophylactic agent against stress-ulcer bleeding that preserves the natural gastric acid barrier against bacterial overgrowth may be preferable to antacids and H2 blockers.
Antacids↗
Ventilatory muscle recruitment in exercise with O2 in obstructed patients with mild hypoxemia.
Respiratory muscle dysfunction limits exercise endurance in severe chronic airflow obstruction (CAO). To investigate whether inspiring O2 alters ventilatory muscle recruitment and improves exercise endurance, we recorded pleural (Ppl) and gastric (Pga) pressures while breathing air or 30% O2 during leg cycling in six patients with severe CAO, mild hypoxemia, and minimal arterial O2 desaturation with exercise. At rest, mean (+/- SD) transdiaphragmatic pressure (Pdi) was lower inspiring 30% O2 compared with air (23 +/- 4 vs. 26 +/- 7 cmH2O, P less than 0.05), but the pattern of Ppl and Pga contraction was identical while breathing either gas mixture. Maximal transdiaphragmatic pressure was similar breathing air or 30% O2 (84 +/- 30 vs. 77 +/- 30 cmH2O). During exercise, Pdi increased similarly while breathing air or 30% O2, but the latter was associated with a significant increase in peak inspiratory Pga and decreases in peak inspiratory Ppl and expiratory Pga. In five out of six patients, exercise endurance increased with O2 (671 +/- 365 vs. 362 +/- 227 s, P less than 0.05). We conclude that exercise with O2 alters ventilatory muscle recruitment and increases exercise endurance. During exercise inspiring O2, the diaphragm performs more ventilatory work which may prevent overloading the accessory muscles of respiration.
Aged↗
Ventilatory muscle dysfunction in patients with bilateral idiopathic diaphragmatic paralysis: reversal by intermittent external negative pressure ventilation.
Bilateral idiopathic diaphragmatic paralysis (BIDP) may result in progressive ventilatory failure. To test the hypothesis that this is in part due to dysfunction of overtaxed inspiratory muscles, we studied 3 patients with BIDP before and after 2, 5, and 18 wk of daily intermittent external surface negative pressure ventilation (ENPV). The patients were evaluated using a zero to 10 functional score (FS) that graded dyspnea, orthopnea, capacity to perform activities of daily living, and ability to work. Pleural (Ppl), abdominal (Pab), and transdiaphragmatic (Pdi) pressures were used as an index of respiratory muscle function. All patients improved their functional score (FS increased 2, 6, and 6, respectively) and their pressure generating ability (Pplmax increased -18, -37, and -46 cm H2O, respectively). Forced vital capacity and functional residual capacity increased in the 2 patients ventilated for longer than 2 wk. These results indicate that ventilatory muscle dysfunction may result from chronic increased work of the inspiratory muscles and that it may improve after periods of intermittent ENPV. This may occur as early as 2 wk after initiation of therapy.
Adult↗
Dyssynchronous breathing during arm but not leg exercise in patients with chronic airflow obstruction.
Some patients with chronic airflow obstruction experience dyspnea with mild arm exercise but not with more-intense leg exercise. To investigate why these patients have limited endurance during arm exertion, we studied ventilatory responses to exercise with unsupported arms in 12 patients with chronic airflow obstruction (mean [+/- SD] forced expiratory volume in one second, 0.68 +/- 0.28 liters). Unloaded leg cycling was also studied for comparison. In the five patients who had the most severe airflow obstruction, arm exercise was limited by dyspnea after 3.3 +/- 0.7 minutes, and dyssynchronous thoracoabdominal breathing developed. In the other seven patients, arm exercise was limited by the sensation of muscle fatigue after 6.1 +/- 2.0 minutes (P less than 0.05), and dyssynchronous breathing did not occur. None of the 12 patients had dyssynchronous breathing during unloaded leg cycling. Maximal transdiaphragmatic pressure, a measure of diaphragmatic fatigue, declined similarly after arm and leg exercise in both groups. During unsupported arm work, the accessory muscles of inspiration help position the torso and arms. We hypothesize that the extra demand placed on these muscles during arm exertion leads to early fatigue, an increased load on the diaphragm, and dyssynchronous thoracoabdominal inspirations. This sequence may contribute to dyspnea and limited endurance during upper-extremity exercise.
Adult↗
Respiratory muscle function.
The functional anatomy of the respiratory muscles has been reviewed. The diaphragm has been emphasized, since this is the most important inspiratory muscle, but the view has been presented that the intercostal, scaleni, and other accessory inspiratory muscles become increasingly important as airflow obstruction leads to hyperinflation. As work increases, the demand for energy and hence blood flow to those muscles has to increase. In spite of a large reserve there are situations in which demands may outstrip supply. This leads to local metabolic changes that result in muscle fatigue. We are now capable of detecting this change as alterations in EMG or in the ability to generate pressures. The latter leads to a decrease in the capacity of the respiratory pump to exchange gas, ultimately resulting in hypercapnia and hypoxemia. The true importance of respiratory muscle fatigue and its differentiation from weakness in patients with severe CAO requires more analysis. It is intuitively appropriate to address the overall decrement in the ability to maintain adequate ventilatory work at low energy cost with the different therapeutic modalities thought to be beneficial. A combination of a decrease in the load imposed on the respiratory muscles, an improvement in the contractility of those muscles, and, when there is absolute need, the resting of the fatigued muscles should result in a better chance to lead a meaningful life and perhaps to improve survival in these patients.
Diaphragm↗
Respiratory consequences of abdominal hernia in a patient with severe chronic obstructive pulmonary disease.
The diaphragm is the most important muscle of respiration. It is believed that the abdominal contents affect diaphragmatic contraction by helping determine its length tension state and by acting as a fulcrum for this muscle to lift the rib cage and thereby increase lung volume. In support of these concepts we describe a patient with severe chronic obstructive pulmonary disease and a large midline hernia of the abdomen who, when standing, had a gastric pressure (Pg) of 4 cm H2O and a maximal transdiaphragmatic pressure (Pdimax) of 14 cm H2O. This was associated with an O2 saturation of 82%, lower thoracic and upper abdominal paradoxical breathing, and severe dyspnea. Once the hernia was reduced there was a rise in Pg to 12 cm H2O, of Pdimax to 27 cm H2O, and of O2 saturation to 89%. There was normalization of the breathing pattern and a decrease in dyspnea. Reduction of this patient's abdominal hernia resulted in an increase in her exercise tolerance.
Abdomen↗