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PubMed1995

Metabolic responses of rat respiratory muscles to voluntary exercise training.

Voluntary wheel running for 4 or 8 wk was used to assess whether a volitional training stimulus would induce adaptations in the oxidative capacity [citrate synthase activity (CS)], glucose phosphorylation capacity [hexokinase activity (HK)], and glucose transporter protein level (GLUT-4) of rat respiratory muscles. Running distances averaged approximately 10-13 km/day over the final 5 wk of training. Peak oxygen consumption by the trained animals was 17% greater (P < 0.05) than by age-matched sedentary control animals after 8 wk. CS, HK, and GLUT-4 in soleus and plantaris muscles all increased because of exercise training. CS increased in the rectus abdominis (+17%), external oblique (+28%), and internal oblique (+17%) but not in the costal or crural diaphragm after 4 wk of training. However, after 8 wk, CS in the costal diaphragm was 39% greater than control but was unchanged in the crural diaphragm. Whereas HK was significantly greater than control in the costal diaphragm (+18%) and rectus abdominis (+54%) after 4 wk, 8 wk of running were required for increases in HK in the external oblique (+17%) and internal oblique (+14%). HK in the crural diaphragm was not significantly altered by the exercise training. GLUT-4 did not change significantly in any of the respiratory muscles studied. These results indicate that significant adaptations in the glucose phosphorylation capacity and oxidative capacity of both inspiratory and expiratory muscles can take place in response to voluntary exercise. However, this same stimulus is not sufficient to cause an adaptive response in GLUT-4 protein level in these respiratory muscles.

Animals↗
PubMed1997

Influence of the perfusate temperature on lung preservation: is there an optimum?

The optimal temperature of the pulmonary flush perfusate is still a matter of controversy. At present, a temperature of 10 degrees C is favored. This study deals with the structural and functional impact of different perfusate temperatures on lung preservation. In an extracorporeal rat heart-lung model lungs were preserved with Perfadex solution of 4, 15 and 25 degrees C and submitted to 2 h ischemia. Heart-lung blocks harvested from male rats were perfused with Krebs-Henseleit solution and ventilated with room air. Lungs were perfused with deoxygenated perfusate via the working right ventricle while the coronary arteries were retrogradely perfused with oxygenated perfusate. Oxygenation capacity (dPO2), peak inspiratory pressure (PIP) and pulmonary vascular resistance were measured. After establishment of baseline functional parameters hearts were arrested with 10 ml St. Thomas cardioplegia and lungs were flushed with 20 ml Perfadex solution. The heart-lung block was then stored for 2 h at 10 degrees C. Reperfusion was performed thereafter under the same conditions. At the end of the trial the lung tissue water was measured by the wet/dry ratio. The perfusion time of the groups flushed with 15 or 25 degrees C perfusate was significantly lower than that of the 4 degrees C group. After 20 min reperfusion dPO2 of the groups flushed with 15 or 25 degrees C was superior to those submitted to a 4 degrees C flush perfusion. PIP was significantly lower in the 15 degrees C group than in the 4 and 25 degrees C groups. The wet/dry ratio revealed the smallest water content in the 15 degrees C group. We conclude that the post-ischemic lung function is dependent on the temperature of the flush perfusate. Among the tested temperatures, perfusion at 15 degrees C showed the best results. The optimum may therefore lie in this range.

Animals↗
PubMed1986

Independent influence of reversibility of air-flow obstruction and nonspecific hyperreactivity on the long-term course of lung function in chronic air-flow obstruction.

We evaluated factors that might influence the course of lung function after 2 to 21 yr of follow-up in 81 nonallergic patients with chronic air-flow obstruction (CAO) and considerable lung function impairment (initial forced expiratory volume in one second as a percentage of inspiratory slow vital capacity (FEV1 % VC) ranging from 40 to 55% and increasing less than 15% after the administration of the anticholinergic bronchodilator thiazinamium). A more favorable rate of change in FEV1 was associated with less pack-years of smoking, less nonspecific hyperreactivity, and a higher degree of reversibility of air-flow obstruction, when expressed as the increase in FEV1 as a percentage of the predicted minus prebronchodilator FEV1 value. Nonspecific hyperreactivity and reversibility of air-flow obstruction appeared to influence the decline in FEV1 independently of baseline value of FEV1, both in smokers and ex-smokers. The hypothesis is put forward that regular bronchodilating therapy may be able to prevent deterioration of lung function. However, the possibility that interval therapy may ultimately produce the same results cannot be excluded. It seems to be important to stop smoking, both for the sake of its negative influence on the course of FEV1 and for the fact that a beneficial influence of bronchodilating therapy may become even more apparent.

Adult↗
PubMed2006

Preliminary results: Effect of whole-body cooling in patients with myasthenia gravis.

INTRODUCTION: Local muscle cooling has been shown to reduce symptoms in some neuromuscular diseases. PURPOSE: To determine whether lowering body temperature using a cooling vest would result in improvement in muscle strength, subjective perceptions of weakness and fatigue, and pulmonary function in patients with generalized myasthenia gravis (MG). METHODS: Patients (five female, one male) with generalized MG, aged 29-58 yr, were studied when mean body temperature was lowered (34.9 +/- 0.62 degrees C) using a cooling vest (CT) and at normal body temperature (35.8 +/- 0.58 degrees C) (NT). Isokinetic and isometric muscle strength and isokinetic endurance were measured using upper body muscle groups. The myasthenic muscle score (MMS) was performed to assess muscle impairment specific to MG patients. Pulmonary function measurements included forced vital capacity (FVC), maximal inspiratory pressure (MIP), and maximal expiratory pressure (MEP). The fatigue impact scale (FIS) was used to track subjective perceptions of fatigue. Core body and skin temperatures were measured throughout each NT and CT trial. RESULTS: Mean body temperature (0.65(core) + 0.35(skin)) was reduced significantly following 30-45 min of cooling (NT = 35.76 +/- 0.58, CT = 34.96 +/- 0.62 degrees C). The MMS and MIP increased significantly (NT = 91.9 vs CT = 96.3; and NT = 69.3 vs CT = 79.5 cm/H2O) with cooling. Although all other variables were not statistically different between temperature conditions, individual results for grip strength of the right hand, fatigue ratio for wrist extensors and shoulder internal and external rotators, FVC, and MEP showed improvement for the majority of the subjects. CONCLUSION: Cooling in patients with MG shows promise to decrease symptoms of weakness and fatigue, thus allowing increased muscle strength and endurance in some patients.

Adult↗
PubMed1993

The lack of effect of routine magnesium administration on respiratory function in mechanically ventilated patients.

STUDY OBJECTIVE: We wished to determine if magnesium infusion would improve respiratory muscle function in long-term ventilated patients even in the absence of hypomagnesemia. DESIGN: Prospective study of mechanically ventilated patients using a double-blind crossover design. SETTING: A combined medical-surgical ICU of a university teaching hospital. PATIENTS: Twenty-one separate admissions to the ICU in 20 patients were studied. Patients who were selected had been intubated and mechanically ventilated for at least 6 days with the admitting diagnosis of respiratory failure. INTERVENTIONS: Twelve patients received 6 g MgSO4 intravenous (i.v.) infusion over 16 h on day 1 followed by placebo infusion on day 2. Nine patients received placebo on day 1 followed by MgSO4 (6 g i.v.) on day 2. MEASUREMENTS AND MAIN RESULTS: We measured vital capacity (VC), maximal inspiratory pressure (Pmax) and maximal expiratory pressure (Pemax) in all patients. There were no significant differences in Pimax (37 +/- 14 vs 42 +/- 20 cm H2O), Pemax (59 +/- 32 vs 61 +/- 38 cm H2O), and VC (850 +/- 460 vs 960 +/- 490 ml) comparing values before and after magnesium infusion. We could not find a subgroup of patients with a marked improvement in Pimax or Pemax. CONCLUSIONS: In patients requiring mechanical ventilation for respiratory failure, magnesium infusion is not associated with increased respiratory muscle strength. Although a trial of MgSO4 administration may be considered for patients with difficulty weaning from mechanical ventilation, it is unlikely to result in clinical improvement.

Adult↗
PubMed1988

Discontinuation of mechanical ventilation.

The vast majority of patients who undergo mechanical ventilation are able to discontinue ventilatory assistance within a few days. Typically, patients who require only short-term mechanical ventilation do not have severe underlying lung disease, and the problem for which they require ventilatory support is most commonly rapidly reversible. In these patients on short-term ventilatory support, parameters of spontaneous ventilatory requirements and respiratory muscle strength, including minute ventilation, maximal voluntary ventilation, vital capacity, and maximal inspiratory pressure, are useful in predicting the success of discontinuation of mechanical ventilation. Ventilatory support can generally be discontinued by a variety of techniques in these patients without the need for weaning from the ventilator per se. The smaller group of patients in whom it is not possible to discontinue mechanical ventilation within less than 7 days comprises individuals who frequently have severe acute or chronic lung disease, multisystem extrapulmonary disease, or neuromuscular disease. After a period of prolonged mechanical ventilatory support, these complicated patients require a process of progressive weaning in which they gradually become able to support spontaneous ventilation. Spontaneous ventilatory parameters do not correlate well with weaning ability in patients on long-term ventilatory support. A systematic and comprehensive approach in which attention is focused on optimizing pulmonary and nonpulmonary factors that affect the weaning process provides the best chance for successful withdrawal of ventilatory support after long-term mechanical ventilation. Inadequate ventilatory drive, respiratory muscle weakness and fatigue, increased work of breathing, excessive CO2 production, and cardiac failure are potential mechanisms that may play a role in inhibiting successful weaning. Adverse factors relevant to each of these mechanisms must be addressed and corrected to whatever extent possible. Studies have not demonstrated the superiority of either classic T-piece weaning or IMV weaning methods in difficult-to-wean patients on long-term ventilatory support. Both techniques may be used successfully as long as all patient variables that may adversely affect weaning ability are corrected or optimized and close care and attention to the details of the weaning process itself are provided.(ABSTRACT TRUNCATED AT 400 WORDS)

Heart Failure↗
PubMed1987

Continuous epidural fentanyl analgesia: ventilatory function improvement with routine use in treatment of blunt chest injury.

The safety and effectiveness of continuous epidural fentanyl analgesia (CEFA) in the treatment of blunt chest injury was evaluated by reviewing its use in 40 patients with multiple rib fractures or flail chest. Ventilatory function tests were performed before and after the institution of CEFA and mean changes calculated. The use of CEFA was associated with significant improvement in vital capacity and maximum inspiratory pressure (p less than 0.05). Minute ventilatory volumes and tidal volumes also showed slight improvement. There was no significant change in arterial CO2 tension with the institution of CEFA, and 85% of patients had good pain relief with CEFA. None of these patients required any other narcotic administration. Documented complications associated with CEFA included pruritus, urinary retention, and transient hypotension. There were no major associated complications. The results suggest that CEFA is a safe, effective method of pain control that acts to improve ventilatory function in patients with blunt chest trauma.

Adult↗
PubMedDate not supplied

Postoperative pulmonary complications and serial pulmonary functions and arterial blood gases in patients undergoing oesophagectomy with or without a thoracotomy.

Transthoracic (TT) (n = 12) and transhiatal oesophagectomy (THE) (n = 14) were performed in 26 patients (19 males and 7 females) suffering from benign or malignant strictures of oesophagus. Nine of these patients were smokers. Preoperatively, various parameters of pulmonary functions did not differ significantly in two groups of patients. Forced vital capacity (FVC), forced expiratory volume in 1 second FEV1 (L) and forced expiratory flow between 25-75% of vital capacity (FEF 25-75%) showed a decline at second/third, seventh and 6 weeks in the postoperative period compared to preoperative values. Decrease in FVC was significant at all times. The change in FEV1 and FEF25-75% was not statistically significant at 6 weeks. The decrease in arterial oxygen tension (PaO2), maximal breathing capacity (MBC), maximal inspiratory (PImax) and expiratory (PEmax) pressures in the postoperative period was significant at second/third and seventh postoperative days. Three of 26 patients died. Of these two had TT while the third one had THE procedure. Twenty-one patients developed postoperative pulmonary complications (PPCs). Patients who developed PPCs had significantly different MBC, FEF25-75%, PEmax and FEV1 compared to those who did not have PPCs. Long-term studies involving a larger number of patients are required to document changes occurring in pulmonary functions, arterial blood gases and nutritional status of these patients.

Adult↗
PubMedDate not supplied

4-Aminopyridine improves pulmonary function in quadriplegic humans with longstanding spinal cord injury.

STUDY OBJECTIVE: To test the hypothesis that 4-aminopyridine (4-AP) might cause clinically evident improvement in pulmonary function in humans with chronic spinal cord injury (chronic SCI). DESIGN: Balanced, open-label study with subjects consecutively enrolled. SETTING: Spinal Cord Injury Service, university-affiliated tertiary level care Department of Veterans Affairs Medical Center. PATIENTS: Seventeen healthy men and women suffering from traumatic SCI (11 quadriplegic, 6 paraplegic patients) for more than 1 year. INTERVENTIONS: Each subject was given a single dose of 4-AP 10 mg orally in an immediate-release formulation. MEASUREMENTS AND MAIN RESULTS: Significant increases in mean values of forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), maximal inspiratory pressure (MIP), and maximal expiratory pressure (MEP) that persisted for at least 12 hours were demonstrated in quadriplegic patients beginning 6 hours after 4-AP administration. Tests of pulmonary function that demonstrated statistically significant increases at any time were also numerically, if not statistically, increased at 24 hours compared with pretreatment values obtained in 4-AP-naive subjects. CONCLUSIONS: The administration of a single dose of an immediate-release formulation of 4-AP to humans with longstanding, traumatic quadriplegia is associated with sustained, clinically meaningful, and statistically significant improvements in pulmonary function. We suggest that the administration of 4-AP may have a salutary effect in patients suffering from SCI and appears to be associated with potentially clinically significant reductions in the pathophysiologic pulmonary sequelae of SCI.

4-Aminopyridine↗
PubMed1991

Respiratory muscle function in asthma.

Asthma increases the load on the ventilatory pump by causing simultaneous increases in airway resistance, lung volume, and minute ventilation. The inspiratory muscles bear the majority of this load, whereas expiratory muscle recruitment is relatively minor. Respiratory muscle strength and endurance appear to be normal in stable asthmatics. During acute attacks, airway closure and expiratory airflow limitation result in a dynamic increase in end-expiratory lung volume. In turn, hyperinflation compromises the function of inspiratory muscles, especially that of the diaphragm, by reducing their force-generating capacity (muscle shortening) and impairing their mechanical advantage on the chest wall. Thus, exacerbations of asthma cause an acute increase in mechanical load together with decreased ventilatory capacity, thereby predisposing to inspiratory muscle fatigue and precipitating hypercapnic respiratory failure in severe cases. Management of ventilatory failure in asthma consists of mechanical unloading of the inspiratory muscles by positive pressure ventilation together with pharmacotherapy (anti-inflammatory and bronchodilating agents) to improve airway function. The strategy of mechanical ventilation is aimed at minimizing dynamic hyperinflation, which increases inspiratory muscle load as well as promotes barotrauma.

Adrenal Cortex Hormones↗
PubMed2006

Length and curvature of the dog diaphragm.

Transdiaphragmatic pressure is a result of both tension in the muscles of the diaphragm and curvature of the muscles. As lung volume increases, the pressure-generating capability of the diaphragm decreases. Whether decrease in curvature contributes to the loss in transdiaphragmatic pressure and, if so, under what conditions it contributes are unknown. Here we report data on muscle length and curvature in the supine dog. Radiopaque markers were attached along muscle bundles in the midcostal region of the diaphragm in six beagle dogs of approximately 8 kg, and marker locations were obtained from biplanar images at functional residual capacity (FRC), during spontaneous inspiratory efforts against a closed airway at lung volumes from FRC to total lung capacity, and during bilateral maximal phrenic nerve stimulation at the same lung volumes. Muscle length and curvature were obtained from these data. During spontaneous inspiratory efforts, muscle shortened by 15-40% of length at FRC, but curvature remained unchanged. During phrenic nerve stimulation, muscle shortened by 30 to nearly 50%, and, for shortening exceeding 52%, curvature appeared to decrease sharply. We conclude that diaphragm curvature is nearly constant during spontaneous breathing maneuvers in normal animals. However, we speculate that it is possible, if lung compliance were increased and the chest wall and the diameter of the diaphragm ring of insertion were enlarged, as in the case of chronic obstructive pulmonary disease, that decrease in diaphragm curvature could contribute to loss of diaphragm function.

Animals↗
PubMed1976

An analysis of potential physiological predictors of respiratory adequacy following cardiac surgery.

More than 50 potential physiological and clinical predictors of postoperative respiratory adequacy were examined in an attempt to identify those few variables which, singly or in combination, best predicted the outcome of the first trial of spontaneous respiration following cardiac surgery. This trial was initiated when patients seemed hemodynamically stable and relatively alert following surgery. Analysis of data from 124 patients identified the following useful predictors: forced vital capacity, total lung capacity, and maximal mid-expiratory flow rate from preoperative pulmonary function tests; resting cardiac index from preoperative cardiac catheterization; postoperative compliance and resistance measured by a computer-based monitoring system; postoperative vital capacity per kilogram, and maximum inspiratory force, measured at the bedside prior to the weaning trial. Stepwise linear discriminant analysis indicated that vital capacity per kilogram and maximum inspiratory force were the most useful predictors, the dividing line between successes and failures being represented by a vital capacity per kilogram of 15 ml. and a maximum inspiratory force of 28 cm. H2O. Mean values of successes were 18.3 +/- 7 ml. per kilogram and 30.7 +/- 9 cm. H2O and, for failures, 11.9 +/- 4 ml. per kilogram and 24.3 +/- 8.4 cm H2O. These physiological variables assess patient effort acting upon an abnormal pulmonary system. Measurements of passive pulmonary mechanics, cardiac function, and the measurement of arterial blood gases were suprisingly poor predictors.

Airway Resistance↗
PubMed1985

[Physical signs reflecting mechanical changes in the respiratory system in chronic obstructive pneumopathy].

During the course of chronic airflow obstruction the effect of the pathological process and compensatory mechanisms that take place in the lungs to limit these effects express themselves by easily indentifiable clinical signs. The limitations of expiratory flow is responsible for the prolongation of the duration of maximal expiration: Pursed lipped breathing is probably the method used by certain patients to limit airway collapse; the increase in the residual volume and functional residual capacity results in distortion of the thorax and a change in the configuration of the inspiratory muscles, reducing their capacity to generate pressures (Hoover's sign: respiratory pulse, hypertrophy of the accessory respiratory muscles, thoraco-abdominal asynchrony); the considerable increase in the inspiratory thoracic depression accounts for the inspiratory descent of the trachea and the sub-sternal "tug". Finally the ventilatory pattern is different, ventilation being rapid and superficial, probably in order to adapt to the constraints imposed by the pathological process.

Abdominal Muscles↗
PubMed1980

Non-organic acute upper airway obstruction: description and a diagnostic approach.

We describe 3 cases of upper airway obstruction in which no organic cause could be identified. All 3 patients presented with severe dyspnea and stridor. Direct laryngoscopy and bronchoscopy failed to demonstrate any lesion. Flow-volume loops showed a pattern of severe variable extrathoracic airway obstruction with a decreased peak inspiratory flow and an increased ratio of the forced expiratory flow at 50% vital capacity to the forced inspiratory flow at the same lung volume. Plethysmographically measured airway resistance was normal in the 2 patients for whom it was obtained. We believe a functional etiology should be added to the possible causes of acute upper airway obstruction. This entity can readily be identified by the marked discrepancy between inspiratory flow limitation and airway resistance.

Adult↗
PubMed1988

Accelerated decay of inspiratory pressure during hypercapnic endurance trials in humans.

Seven normal human subjects inspired a CO2-O2 mixture from a constant-flow generator while performing maximal inspiratory maneuvers from functional residual capacity. End-tidal CO2 (ETCO2) was maintained at either 5.5 (normocapnia), 3.5 (hypocapnia), or 7% (hypercapnia) on separate testing days. Subjects attained maximal mouth pressure (Pm) while breathing at either 1.25 or 1 l/s, utilizing a fixed breathing pattern (duty cycle 0.43) with an inspiratory time of 1.5 s. Maximal Pm was measured at rest and then during a 10-min endurance trial in which subjects repeated maximal voluntary inspirations with constant flow and breathing pattern. The endurance Pm data were fit to nonlinear exponential regression. The results indicated that 1) maximal Pm at rest was unaffected by changing ETCO2; 2) the rate of Pm decay over time was accelerated by hypercapnia, whereas hypocapnia showed no consistent effects; and 3) "sustainable" Pm, attained toward the end of the endurance trial, was not decreased; therefore sustainable force output was preserved in response to changing ETCO2.

Carbon Dioxide↗
PubMed1996

[Specific inspiratory muscle training in chronic hemodialysis].

Chronic renal failure can result in a variety of conditions leading to muscle weakness. We investigated inspiratory muscle (IM) performance and functional capacity in chronic renal failure before and after specific inspiratory muscle training (SIMT). 9 men and 1 woman, ranging in age from 22-78 years, while on chronic hemodialysis received SIMT 3 times a week, for 3 months, while 10 others received sham training. Static inspiratory pressures, IM endurance and functional capacity were reduced in most subjects. Following SIMT, IM performance improved significantly and was associated with improved functional capacity, but not in the control group. We conclude that patients with chronic renal failure undergoing maintenance hemodialysis have reduced IM performance, and SIMT improves functional capacity.

Adult↗
PubMed1988

Drive and timing components of respiration in young children following induction of anaesthesia with halothane or ketamine.

Timing and drive components of respiration were studied in 18 young children following induction of anaesthesia with ketamine and were compared with results from ten children following induction of anaesthesia with halothane. During one minute of quiet breathing, signals from a pneumotachograph attached to the anaesthetic mask were analysed for tidal volume (Vt), respiratory frequency (f), minute volume (Ve), inspiratory and expiratory times (Ti, Te) and flow pattern. Following induction of anaesthesia with ketamine, children breathed more slowly and deeply than children receiving halothane, but there was no significant difference in Ve or in Vt/Ti, suggesting that respiratory drive was similar in the two groups of children. In the children receiving ketamine, Ti was more than twice as long, and thus the ratio Ti/Te was significantly increased, in comparison with the group receiving halothane. In addition to the prolonged Ti in the children induced with ketamine, there was a more rapid increase in volume in early inspiration than in late inspiration, which is an apneustic breathing pattern. There was a slower decrease in volume in early expiration, with occasional early expiratory breath holding lasting up to three seconds, in the ketamine-induced children. The unique breathing pattern demonstrated with ketamine, consisting of large Vt, increased Ti/Te ratio, apneustic inspiratory pattern, and expiratory braking, contributed to an increased mean lung volume above functional residual capacity, of 2.40 ml.kg-1 body weight, in comparison to 1.27 ml.kg-1 in the children receiving halothane.

Anesthesia, Inhalation↗
PubMed1994

Effects of combined inspiratory muscle and cycle ergometer training on exercise performance in patients with COPD.

Cycle ergometer training plays an important role in the rehabilitation of patients with chronic obstructive pulmonary disease (COPD), but the usefulness of specific inspiratory muscle training as part of pulmonary rehabilitation remains uncertain. To determine whether inspiratory muscle training could intensify the known beneficial effects of cycle ergometer training on exercise performance in these patients, we compared the effect of an 8 week inspiratory muscle training combined with cycle ergometer training with that of an 8 week cycle ergometer training alone on inspiratory muscle performance and general exercise capacity. Patients were randomly assigned to the two training groups; 21 patients received additional inspiratory muscle training (Group 1) and 21 did not (Group 2). Maximal sniff assessed oesophageal and transdiaphragmatic pressures served as parameters for global inspiratory muscle strength and diaphragmatic strength, respectively. The duration for which the patient could breathe against a constant inspiratory pressure load was used as an index of inspiratory muscle endurance. Exercise capacity was determined by an incremental symptom-limited cycle ergometer test. After the training period, inspiratory muscle performance improved significantly in the patients with inspiratory muscle training, but not in those without. Both training regimens increased maximal power output and oxygen uptake, but this improvement was significantly greater in the patients with inspiratory muscle training than in those without.(ABSTRACT TRUNCATED AT 250 WORDS)

Breathing Exercises↗