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The term amyotrophic lateral sclerosis (ALS) comprises a group of motor neuron diseases which are characterized by rapid disease progression and poor prognosis which is mostly due to severe respiratory muscle weakness and its sequelae. Since causative treatment options are limited it is crucial to offer comprehensive symptomatic therapies to affect patients. Symptoms of respiratory muscle weakness, sleep-disordered breathing and, subsequently, chronic hypercapnic respiratory failure are known to severely affect health-related quality of life and social functioning of patients with ALS. This review article delineates the clinical presentation of respiratory muscle weakness, diagnostic procedures to assess diaphragmatic function, and practical aspects of both mechanical ventilation and cough assistance, respectively. Various technical and electrophysiological methods allow for detection of diaphragmatic weakness and nocturnal hypoventilation. These include spiro-manometric tests of respiratory muscle strength, cardiorespiratory polygraphy and polysomnography, transcutaneous capnography, and blood gas analysis. Once the diagnosis of respiratory muscle weakness is established, non-invasive ventilation, tracheostomy-invasive ventilation (if the patient agrees to it), and management of secretions all become increasingly important in the course of the disease., (© Georg Thieme Verlag KG Stuttgart · New York.)

Background: Chronic respiratory failure is caused by insufficiency of the inspiratory muscles, i.e. mainly the diaphragm, which represents the so-called "respiratory pump". Insufficiency of the respiratory pump causes hypercapnia., Therapeutic Intervention: Diseases with chronic hypercapnia are characterized by reduced survival. Mechanical ventilation-mostly applied as noninvasive mechanical ventilation (NIV)-improves ventilation and unloads the inspiratory muscles., Indication: Strong evidence supports the use of domiciliary NIV already in mild degrees of chronic respiratory failure caused by neuromuscular diseases, thoracic restrictions and obesity hypoventilation. In these diseases long-term NIV improves both physiological parameters (such as blood gases) and clinical outcome, e.g. exercise capacity, right heart dysfunction, sleep quality, disease-specific aspects of health-related quality of life (HRQL) and survival rate. In contrast, its influence on long-term survival in chronic obstructive pulmonary disease (COPD) patients is not clearly proven. Prescription of home NIV in COPD should therefore be restricted to severe degrees of chronic respiratory failure. Finally, there is an indication for domiciliary NIV in patients after prolonged weaning from mechanical ventilation. This paper elaborates underlying pathophysiology, diseases and how NIV works in chronic hypercapnic respiratory failure.

Based on the tremendous impact of impaired respiratory muscle function, tests on their function play a significant role in respiratory and intensive care medicine. Besides differential diagnosing e.g. during prolonged weaning and quantification of impaired respiratory muscle function, e.g. in COPD, neuro-muscular diseases or ventilator-induced diaphragmatic dysfunction, those tests qualify for follow-up assessment, e.g. phrenic nerve lesions or specific respiratory muscle training. In general, (simple) volitional and (complex) non-volitional tests are available. Volitional tests aim at screening for potential respiratory muscle impairment, while non-volitional tests - including ultrasound application - are used to further specify low values assessed by volitional tests and to assess complex clinical conditions (e.g. intubated, sedated patients). Several tests are complementary or additive to each other. Complete assessment for respiratory muscle function, therefore, frequently requires the combination of different test regimes. The current recommendations include in-depth description and practical guidelines for the different tests and approaches to assess respiratory muscle function., (© Georg Thieme Verlag KG Stuttgart · New York.)

Approximately 10% of patients with mechanical ventilation experience prolonged weaning and also have an increased morbidity and mortality. Once spontaneous breathing trials have failed the organ systems responsible should be identified. This can be accomplished during the spontaneous breathing trial using clinical examination, measurement of blood gases, echocardiography and imaging techniques. Specific patterns allow the diagnosis of pathological respiratory mechanisms, weak ventilatory muscles, heart failure, myocardial ischemia and psychiatric problems. Respiratory and cardiac limitations of weaning can be overcome by reducing the ventilatory load, training of the ventilatory muscles and reducing cardiac workload. A cooperative sedation strategy as well as an early start of weaning and rehabilitation can prevent prolonged weaning in critically ill patients.

Since valosin-containing protein mutations were reported as a cause of hereditary inclusion body myositis associated with Paget's disease of the bone and frontotemporal dementia, many new mutations have been described in the last decade. We report on a 46-year-old German male with a progressive tetraparesis and autosomal dominant inheritance pattern. Echocardiography revealed a beginning dilated cardiomyopathy and laboratory analyses showed increased alkaline phosphatase. Decreased verbal memory and an impairment of concept building were observed on neuropsychological examination. Muscle biopsy demonstrated a myopathic pattern, rimmed vacuoles, CD8+ T-cell infiltrates and positive MHC1-muscle fibres. We found a heterozygote mutation in exon 5 of the valosin-containing protein gene (c.464G > T p.Arg155Leu), which until now has been described only in an Australian family. We describe here the first German case with the above-mentioned mutation causing inclusion-body myositis associated with Paget's disease of the bone and fronto-temporal dementia. Here, we recommend regular controls of cardiac and respiratory functions., (© Georg Thieme Verlag KG Stuttgart · New York.)

Obstructive sleep apnea (OSA) is caused by repetitive collapse of a narrow upper airway during sleep with the main risk factor being obesity. Apneas are followed by hypoxia, sympathetic activation, intrathoracic pressure swings and arousals. In most animal studies, only the cyclical pattern of hypoxia characteristic of OSA is simulated, however, more complex models have also been developed which additionally reflect the other pathophysiological changes associated with sleep-disordered breathing. These models have contributed to a deeper understanding of the cardiovascular and metabolic consequences of OSA. From other experiments the concept of the pharynx behaving like a collapsible tube, i. e. a Starling resistor, has emerged. Finally, the neurotransmitter modulation of upper airway muscle tone has been elucidated by using IN VIVO microdialysis of the caudal medulla of rats. It is hoped that findings from animal studies will in the future impact on the management of patients with OSA, in particular if they are non-compliant with CPAP therapy., (Copyright Georg Thieme Verlag KG Stuttgart . New York.)

Heart failure is an established diagnosis. Respiratory muscle or ventilatory pump failure, however, is less well known. The latter becomes obvious through hypercapnia, caused by hypoventilation. The respiratory centre tunes into hypercapnea in order to prevent the danger of respiratory muscle overload (hypercapnic ventilatory failure). Hypoventilation will consecutively cause hypoxemia but this will not be responsible for performance limitation. One therefore has to distinguish primary hypoxemia evolving from diseases in the lung parenchyma. Here hypoxemia is the key feature and compensatory hyperventilation usually decreases PaCO2 levels. The cardiac as well as the respiratory pump adapt to an inevitable burden caused by chronic disease. In either case organ muscle mass will increase. If the burden exceeds the range of possible physiological adaptation, compensatory mechanisms will set in that are similar in both instances. During periods of overload either muscle system is mainly fueled by muscular glycogen. In the recovery phase (e. g. during sleep) stores are replenished, which can be recognized by down-regulation of the blood pressure in case of the cardiac pumb or by augmentation of hypercapnia through hypoventilation in case of the respiratory pump. The main function of cardiac and respiratory pump is maintenance of oxygen transport. The human body has developed certain compensatory mechanisms to adapt to insufficient oxygen supply especially during periods of overload. These mechanisms include shift of the oxygen binding curve, expression of respiratory chain isoenzymes capable of producing ATP at lower partial pressures of oxygen and the development of polyglobulia. Medically or pharmacologically the cardiac pump can be unloaded with beta blockers, the respiratory pump by application of inspired oxygen. Newer forms of therapy augment the process of recovery. The heart can be supported through bypass surgery or intravascular pump systems, while respiratory muscles may be supported through elective ventilatory support (mainly non-invasive) in the patient's home. The latter treatment in particular will increase patient endurance and quality of life and decrease mortality. Heart and respiratory pump failure share many common features. Since both take care of oxygen supply to the body, their function and compensatory mechanisms are closely related and linked.

Non-invasive ventilation has not yet been established in prehospital emergency medicine. This most likely due to missing technical prerequisites. Meanwhile emergency ventilators feasible for prehospital NIV are available. Recognizing the pathophysiology of acute respiratory insufficiency, treatment with NIV is superior in comparison to treatment with oxygen and medication only. The advantages of NIV may lead to reduced morbidity and mortality as long as attention is paid to possible contraindications.

The respiratory system consists of two parts which can be impaired independently from each other, the lungs and the respiratory pump. The latter is a complex system covering different anatomic structures: the breathing centre, the peripheral nervous system, the respiratory muscles, and the thorax. According to this complexity several underlying conditions can cause insufficiency of the respiratory pump, i. e. ventilatory failure. Disturbances of the breathing centre, different neuromuscular disorders, impairments of the mechanics, such as thoracic deformities or hyperinflation, and airway obstruction are example conditions responsible for ventilatory failure. Main characteristic of ventilatory failure is the occurrence of hypercapnia which is in contrast to pulmonary failure where diffusion disturbances typically not cause hypercapnia. Both acute and chronic ventilatory failure presenting with hypercapnia can develop. In acute ventilatory failure respiratory acidosis develops, but in chronic respiratory failure pH is normalized as a consequence of metabolic retention of bicarbonate. However, acute on chronic ventilatory failure can present with a combined picture, i. e. elevated bicarbonate levels, acidosis, and often severe hypercapnia. Clinical signs such as tachypnea, features of the underlying disease or hypercapnia are important diagnostic tools in addition to the measurement of pressures generated by the respiratory muscles. Non-invasive and widely available techniques, such as the assessment of the maximal ins- and expiratory mouth pressures (PImax, PEmax), should be used as screening instruments, but the reliability of these measurements is reduced due to the volitional character of the tests and due to the impossibility to define normal values. Inspiratory pressures can be assessed more accurately and independently from the patients' effort: with or without the insertion of oesophageal and gastric balloon catheters. However, this technique is more invasive and very complex. It is therefore restricted to centres with scientific aims.

A 40-year-old roofer called the medical emergency team because of sudden dyspnea and chest constriction. He was suffering from bronchial asthma that exacerbated probably due to the inhalation of a solvent while at work. Because of status asthmaticus he was intubated immediately after arrival in the hospital and breathing had to be assisted artificially for ten hours. After extubation he complained of chest pain. In view of an elevated creatinkinase of 4368 U/1 this was interpreted as rhabdomyolysis of the respiratory muscles due to the status asthmaticus. As a cause of chest pain and elevation of creatinkinase after severe respiratory work under hypoxic conditions rhabdomyolysis of the involved musculature has to be considered.

Non-invasive ventilation is a technique to ventilate patients without endotracheal intubation and analgosedation. Pressure tight masks allow the ventilation of patients with severe respiratory or ventilatory insufficiency. Non-invasive ventilation may be used as short-term treatment for patients with acute ventilatory decompensation, as well as for long-term therapy at home for patients with chronic respiratory diseases. The typical indications are hypoxaemic respiratory failure in pneumonia or cardiogenic pulmonary edema, and hypercapnic ventilatory insufficiency in severe chronic obstructive pulmonary disease, neuromuscular disorders, or advanced kyphoscoliosis. The physiological background, technical aspects of performing non-invasive ventilation, and typical indications are discussed.

Breathing discomfort is one of the most common and distressing symptoms experienced by patients. Various pathophysiologic mechanisms underlie the symptom of dyspnea, and multiple mechanisms may be present in a given patient. The evaluation of the dyspneic patient must begin with a thorough history examining the key characteristics of the symptom, including quality, intensity, duration, frequency, and distress. The words utilized by patients to describe their breathing discomfort may provide insights into the underlying pathophysiology of their disease. Treatment for dyspnea should be selected based on the pathophysiologic mechanisms involved and not only according to the specific disease. Attempts are made to reduce mechanical impedance (by reducing lung hyperinflation by bronchodilators or surgical volume reduction), to reduce ventilatory demand (by exercise training), to improve inspiratory muscle function (by inspiratory muscle training), to alter breathing patterns, to begin supplemental oxygen therapy and to reduce central perception. It is often necessary to combine several treatment modalities in order to achieve a significant reduction in dyspnea.

Unlabelled: Sleep-disordered breathing is common in neuromuscular diseases but remains poorly defined in its relationship to daytime respiratory function., Methods: We prospectively compared supine lung and respiratory muscle function with results of polysomnography/capnometry in 35 patients with progressive myopathies (age 32.5 +/- 15 years)., Results: 32/35 patients had restrictive ventilatory defect, 9/32 had hypercapnic respiratory failure by day (PaCO(2) 66.0 +/- 15.7 mm Hg). Supine inspiratory vital capacity (IVC(S)) correlated with maximal inspiratory muscle pressure (R = 0.75), respiratory muscle strain (P0.1/PImax, R = - 0.68), and daytime blood gases (p < 0.005 for all). SDB in the way of REM-sleep hypopneas, circumscribed hypoventilation episodes and sleep-stage independent continuous hypoventilation (PtcCO(2) > 50 mmHg > 50% of sleep time) was common at IVC(S)< 60% pred, and preceded daytime hypercapnia. IVC(S) correlated with nocturnal SaO(2) (R = 0.64), PtcCO(2) (R = - 0.87), percent light sleep (R = 0.67) and deep sleep (R = - 0.76). IVC(S) correlated only marginally with respiratory disturbance index (total sleep, R = - 0.45; REM-sleep, R = - 0.44). IVC(S) < 60% was 96% sensitive, 78% specific for presence of SDB. IVC(S) < 20 % was 89% sensitive, 96% specific for daytime hypercapnia., Conclusions: IVC(S) correlates with respiratory muscle function, daytime and nocturnal blood gases, and is highly predictive of SDB and daytime hypercapnia.

About 80,000 polio survivors are still living 40 years after the last polio epidemics in Germany. Of these 40-70% have developed the so called post-polio syndrome (PPS) decades after the infection. The main symptoms of PPS are decreasing strength in voluntary muscles, pain and fatigue which occur spontaneously but may also be induced by physical stress and general illness. We report the case of a 79-year-old male who developed hypercapnia due to ventilatory failure which necessitated reintubation several times after cholecystectomy. The medical history revealed that he had had poliomyelitis at the age of 8 years. There was only a slight residual handicap from this infection which included mild pareses of the left limbs but had remained stable for about 70 years. Electromyography revealed signs of chronic neurogenic changes in muscles of the left upper limb as well as in the pectoralis major. The diagnostic criteria of a post-polio syndrome were fulfilled and other neuromuscular diseases were excluded. The patient could be discharged from intensive care only after treatment by intermittent positive pressure ventilation via a facial mask. This case report shows that even patients who have a mild handicap after poliomyelitis can develop weaning problems. A PPS can exacerbate with inclusion of respiratory muscles in critically ill patients.

During the last years our knowledge about the malnutrition of patients with COPD has grown. Weight loss is a problem of some patients with COPD, but, as we know today by techniques of body composition measurement much more patients have reduced muscle mass. The reason for this is complex and involves many body systems. Nutritional intervention alone is not successful in many patients. We have to accept that COPD is a kind of systemic disease which does not only involve the lung. Thus, future therapies have to include not only treatment of the bronchial system.

Background: Noninvasive pressure support ventilation (NPSV) demands triggering with each breath. This study investigates the effects of NPSV via face mask on breathing pattern, ventilation and respiratory muscle loading in patients with hypercapnic stable COPD., Methods: 7 patients (age 66 +/- 9 years; FEV1 43 +/- 13% predicted; PaO2 52 +/- 19 mmHg; PaCO2 58 +/- 12 mmHg) were included. The physiologic variables were evaluated during spontaneous breathing and at the end of a 60 minutes period with NPSV. Inspiratory positive airway pressure (IPAP) and expiratory positive airway pressure (EPAP) were adjusted to 12-14 cm H2O and 3 cm H2O, respectively. Respiratory muscle activity was measured as esophageal and transdiaphragmatic pressure time product (PTPes and PTPdi)., Results: Non-triggering was observed only occasionally. Compared to unsupported spontaneous breathing NPSV improved ventilation: PaCO2 was reduced from 58 +/- 11 mmHg to 50 +/- 14 mmHg (p +/- 0.05). Respiratory muscles were unloaded by 30% (p +/- 0.05). Breathing frequency and breathing pattern did not change., Conclusions: In patients with hypercapnic stable COPD NPSV effectively recognizes and supports breathing efforts. As a result ventilation is improved and respiratory muscles are unloaded.

The aim of this retrospective study was to investigate the mouth-occlusion-pressure under CO2-stimulation in five patients (3 women, 2 men) suffering from kyphoscoliosis of different aetiology whilst being under noninvasive ventilation for respiratory muscle fatigue. Ten months after initiation of noninvasive ventilation we could demonstrate a marginal improvement of respiratory muscle strength but the P0.1 CO2-decreased slightly. We conclude that this decrease might be due to an increase in tidal volume allowing for a reduction in respiratory rate.

Methods: Five patients with chronic ventilatory failure demonstrated by arterial hyperkapnia and overloaded respiratory muscles under spontaneous ventilation (P01/P01 max) were adapted to passive noninvasive ventilation (ISB). Three of them suffered from severe COPD (FEV1 < 50%), two patients from severe restriction (VC < 30%). These patients had to undergo a bicycle ergometer exercise with and without nasal ventilation until they reached physical exhaustion with standardised incremental increase in external workload., Results: In both settings all patients were able to manage exercise up to their physical exhaustion. The anaerobic limit was exceeded each time. The total ventilation volume had to be increased two- to threefold during exercise with nasal ventilation to maintain the passive ventilation. The reduced load on the respiratory muscles was generally proven by lower pCO2 and higher pH levels. Without ventilation discontinuation of the exercise was caused by dyspnoea, whereas this was due to weakness in the legs under ventilation. In all five cases the achieved level of external workload was higher when supporting the respiratory muscles (43 watts vs. 36 watts) at lower lactate levels., Conclusion: On a bicycle ergometer the respiratory muscles can be sufficiently relieved using noninvasive nasal ventilation. A higher level of workload, longer duration and a higher quality of exercise can be achieved thereby. The fact that patients without relief of load of the respiratory muscles complained of dyspnoea, whereas the fact that patients with ventilation complained of weakness in their legs indicates the high efficiency of this method, although the tested patients are severely handicapped individuals who usually do not undergo comparable physical exercise in their daily activities.

Respiratory muscle weakness may be the sole cause of dyspnea or may aggravate dyspnea due to another respiratory disease, and is often difficult to recognise clinically. The assessment of respiratory muscles should follow a graded approach using tests of increasing complexity. Clinical examination should look for dyspnea, orthopnea, morning headache, daytime somnolence, fatigability, tachypnea, abdominal, or rib cage paradox, and amyotrophy. Imaging is useful in diagnosing diaphragmatic paralysis using chest radiograph, fluoroscopy or ultrasound. In cases of moderate to severe respiratory muscle weakness, lung volumes show reduced vital capacity and total lung capacity. Measuring the change in vital capacity from sitting to supine position is useful since it shows a 25-50% fall in cases of diaphragmatic paralysis. The specific and classical tests of respiratory muscle strength are maximum inspiratory and expiratory pressures (MIP and MEP) sustained during one second against near complete occlusion. Sniff nasal inspiratory pressure (SNIP) is a new and easier test of inspiratory muscle strength. Normal values obtained with these simple tests rule out clinically significant respiratory muscle weakness. In case of doubt, more complex and invasive tests can be used such as transdiaphragmatic pressure and magnetic stimulation of the phrenic nerves.

History and Clinical Finding: A 73-year-old man developed progressive respiratory failure within 24 hours, requiring emergency admission for mechanical ventilation. The cause of the dyspnoea and tachypnoea could not be ascertained by routine medical and neurological examination. Neuromuscular disease or a cerebral lesion was considered in the differential diagnosis, together with a cardiovascular cause., Investigations: Neither laboratory tests nor additional investigations (chest radiogram, echocardiography) gave a diagnosis. Magnetic resonance imaging and computed tomography excluded a focal cerebral or spinal lesion or a space-occupying lesion in the region of the phrenic nerve. An electrophysiological tests (EPT) failed to establish a neuromuscular disease. However, when signs of upper motor neurone irritation appeared, more detailed EPTs, also of the muscles of breathing, provided the diagnosis of amyotrophic lateral sclerosis (ALS)., Treatment and Course: Symptomatic treatment with pyridostigmine made it possible gradually to wean the patients off the ventilator so that he could be sent home on intermittent mechanical ventilation., Conclusion: In case of acute respiratory failure without cardiopulmonary cause motoneurone disease with initial involvement of respiratory musculature should be considered, even in the absence of clinical signs, and special electrophysiological tests may be necessary to recognize the underlying disease.

Impaired pulmonary gas exchange can result from lung parenchymal failure inducing oxygenation deficiency and fatigue of the respiratory muscles, which is characterized by hypercapnia or a combination of both mechanisms. Contractility of and coordination between the diaphragm and the thoracoabdominal respiratory muscles predominantly determine the efficiency of spontaneous breathing. Sepsis, cardiac failure, malnutrition or acute changes of the load conditions may induce fatigue of the respiratory muscles. Augmentation of spontaneous breathing is not only achieved by the application of different technical principles or devices; it also has to improve perfusion, metabolism, load conditions and contractility of the respiratory muscles. Intermittent mandatory ventilation (IMV) allows spontaneous breathing of the patient and augments alveolar ventilation by periodically applying positive airway pressure tidal volumes, which are generated by the respirator. Potential advantages include lower mean airway pressure (PAW), as compared with controlled mechanical ventilation, and improved haemodynamics. Suboptimal IMV systems may impose increased work and oxygen cost of breathing, fatigue of the respiratory muscles and CO2 retention. During pressure support ventilation (PSV), inspiratory alterations of PAW or gas flow (trigger) are detected by the respirator, which delivers a gas flow to maintain PAW at a fixed value (usually 5-20 cm H2O) during inspiration. PSV may be combined with other modalities of respiratory therapy such as IMV or CPAP. Claimed advantages of PSV include decreased effort of breathing, reduced systemic and respiratory muscle consumption of oxygen, prophylaxis of diaphragmatic fatigue and an improved extubation rate after prolonged periods of mechanical ventilation. Minimum alveolar ventilation is not guaranteed during PSV; thus, close observation of the patient is mandatory to avoid serious respiratory complications. Continuous positive airway pressure breathing (CPAP) maintains PAW above atmospheric pressure throughout the respiratory cycle, which may increase functional residual capacity and decrease the effort of breathing. CPAP has been conceptually designed for the augmentation of spontaneous breathing and requires the intact central and peripheral regulation of the respiratory system. Airway pressure release ventilation (APRV) improves alveolar ventilation by intermittent release of PAW, which is kept above atmospheric pressure by means of a high-flow CPAP system. The opening of an expiratory valve for 1-2 s induces a decreased PAW and lung volume, which increases rapidly to pre-exhalation values after closure of the valve due to the high gas flow within the circuit (90-100 1/min). APRV may improve haemodynamics and VA/Q distribution as compared with conventional mechanical ventilation. Biphasic positive airway pressure (BIPAP) is characterized by the combination of spontaneous breathing and time-regulated, pressure-controlled mechanical ventilation. During the respiratory cycle the ventilator generates two alternating CPAP levels, which can be modified with regard to time and pressure. As with APRV, alveolar ventilation is maintained even if the spontaneous breathing efforts of the patient cease, which improves the safety of both modes of respiratory therapy. The contribution of spontaneous breathing to total minute ventilation may be important, since a decreased shunt and improved VA/Q relationship have been observed in experimental non-cardiogenic lung oedema. These data give support to the concept that spontaneous breathing should be maintained and augmented in the setting of acute respiratory failure.

Thyroid hormones exercise a direct influence on the lung and myocardium. It has been found that at the heart of patients suffering from hyperthyroidism there is an increased production of contractile proteins and a redistribution of myosin Isoenzymes. Reduced efficiency results from the increased oxygen consumption and insufficient adaptation of the heartbeat to stress. Thyroid hormones are responsible for reducing arterial resistance; a higher incidence of supraventricular arrhythmias has been observed. In contrast, the cardiac changes in hypothyroidism are associated with an enhanced deposition of glycosaminoglycan in the myocardium. Besides bradycardia and low voltage there is an increased incidence of pericardial, pleural and peritoneal effusions with high protein content. Patients suffering from hypothyroidism have a higher incidence of atherosclerotic changes. Hypothyroidism is associated with a reduction of the beta-adrenergic receptors, and hence disturbances of rhythm are rare and do not increase even under substitution therapy. Pulmonary involvement in hyperthyroidism is evident from an enhanced respiratory minute volume, a reduced vital capacity, and dyspnoea at rest. In patients suffering from hypothyroidism, hypoventilation reduces the efficiency. Over and above this, myopathic changes of the respiratory muscles have been described. Involvement of thyroid hormones in the maturing of type II pneumocytes and of the surfactant factor has also been under discussion.

Between September 1994 and August 1996 Lung Volume Reduction Surgery (LVRS) was performed through median sternotomy, videoendoscopically or by thoracotomy in 60 patients (age 33 to 80 years, mean 56.7 years). All these patients had severe emphysema despite maximal conservative and physical therapy. The areas with the most destroyed lung parenchyma were resected by means of linear stapling devices, 3 patients (20%) out of 15 who were operated via sternotomy died postoperatively due to aspiration pneumonia, multiorgan failure and acute hepatic failure. In the videoendoscopic group with 45 patients, 2 patients (4.4%) died due to multiorgan failure and cardiorespiratory failure. 72.7% of the remaining patients showed a significant functional improvement (postoperative FEV1 > 130% of the preoperative value) with a marked decrease of dyspnea. There was no significant improvement in 23.7% of the patients (postoperative FEV1 = 90 to 110% of the preoperative value) and 3.6% of the patients had a functional deterioration. Residual volume decreased from 317.0 +/- 12.4% of predicted (%p) preoperatively to 226.2 +/- 8.8 %p within the first month (p = 0.0001). FEV1 significantly increased from 23.7 +/- 1.3 %p preoperatively to 36.6 +/- 4.1 %p during the first 6 months postoperatively (p = 0.0016). Radiological signs of hyperinflation and distention of the thorax preoperatively improved to narrowed intercostal spaces and a more shaped diaphragm. These morphological changes resulted in better ventilatory muscle function. The intrinsic PEEP significantly decreased from 5.92 +/- 0.64 cm H2O preoperatively to 1.70 +/- 0.25 cm H2O postoperatively (p = 0.0001). The work of breathing decreased from 1.58 +/- 0.09 J/l preoperatively to 0.99 +/- 0.07 J/l postoperatively (p = 0.0001). In conclusion, LVRS is an excellent therapeutic option for patients with severe emphysema and additional signs of severe hyperinflation with significant postoperative functional improvement and marked increase in quality of life.

The increased airway resistance and hyperinflation characteristic of chronic obstructive pulmonary disease (COPD) affect respiratory muscle function, particularly that of the diaphragm. The compensatory changes of the breathing pattern due to expiratory flow limitation lead to a further increase of the mechanical load on the ventilatory muscles during forced ventilation. Therapeutic strategies which reduce hyperinflation and the increased airway obstruction, improve the neuromechanical efficiency of the inspiratory muscles.

Long-term mechanical ventilation implies a significant number of weaning failures. The basis of this unweanability is chronic fatigue of the inspiratory muscles which is due to depletion of energy store (e.g. glycogen). Considering this pathophysiological principle, the decisive therapeutic option during weaning from long-term mechanical ventilation consists of resting the respiratory muscles. The commonly used assisted ventilation modes only partially relieve the respiratory muscles because the work of breathing is done both during the trigger phase and during the inspiratory cycle. The essential characteristic of our weaning concept includes the repeated determination of the spontaneous breathing frequency in awake patients, which is followed by controlled intermittent positive pressure ventilation with a slightly higher respiratory rate. Ideally, this results in total suppression of the activity of the breathing centre, and in subsequent relief and recovery of the respiratory muscles by replenishing the energy stores. The close succession of relief and training periods avoids inactivity-induced atrophy of the respiratory muscles and permits regeneration. Additionally, our weaning concept avoids increases in inspiratory work during the phases of spontaneous breathing. This means that high-resistance small-caliber endotracheal tubes have to be replaced by large tubes. Moreover, transtracheal oxygen insufflation during spontaneous breathing decreases anatomic dead space. This reduces minute ventilation and, therefore, the work of breathing. In patients still exhibiting chronic fatigue of the respiratory muscle pump after successful weaning, intermittent home ventilation is initiated via a breathing mask. Apart from the concept described above, successful weaning from the respirator after long-term ventilation is based upon dedicated patient care and depends on the architectural characteristics of the intensive care unit.

Background: Chronic hypercapnia seems to preserve the overloaded respiratory pump from manifest muscle failure. In order to get information about the regulation of the ventilation under exercise we investigated clinical stable hypercapnic patients., Patients and Methods: Twenty-one patients (20 males, 53.7 +/- 13.2 years) with obesity-hypoventilation syndrome (8), chronic obstructive lung disease (4), scoliosis (3), myopathy (2) and post-Tbc (2) were examined. Ventilation parameters (fb, Vt, VO2), respiratory muscle strength (PImax, PEmax), arterial blood gases (pO2, pCO2), respiratory quotient (RQ) and lactate were measured at rest and at the end of 5 minutes of maximal bicycle exercise. The control group consisted of 10 healthy persons., Results and Conclusions: A significant augmentation of the pre-existing hypercapnia under exercise (reflecting hypoventilation in relation to the predicted value) was observed in all patients with chronically overloaded respiratory muscles. This mechanism seems to be wise because it protects the respiratory pump from failure.

Background: A chronic hypercapnic ventilatory failure appears in patients with restrictive chest wall disorders, chronic obstructive pulmonary disease (COPD) or obstructive sleep apnea (OSA), but it can also appear in patients with a disorder of the central respiratory drive., Patients and Method: We studied the lung function, the respiratory muscle function and the PCO2 recruitment threshold (pCO2RT) during nasal intermittent positive pressure ventilation (IPPV) in 16 chronic hypercapnic patients (scoliosis = 8, COPD = 4, OSA = 4)., Results: The pCO2RT decreased from 61 +/- 6 mm Hg to 48 +/- 4 mm Hg (p < 0.0001) during intermittent IPPV, while spontaneous pCO2 decreased from 55 +/- 6 mm Hg to 42 +/- 5 mm Hg (p < 0.0001). The load of the respiratory pump decreased (P0.1/P0.1 max:0.27 +/- 0.18 before, 0.15 +/- 0.08 after intermittent IPPV; p < 0.04)., Conclusion: We conclude, that the pCO2RT can be normalized by intermittent nasal IPPV as well as the pCO2 under spontaneous breathing. The load of the respiratory pump decreases due to an increase of the inspiratory muscle strength.

The vital function respiration is kept up by the modifiable basal activity of the thin muscles of the abdominal cavity. The diaphragm is an important part of the respiratory muscular system. The muscular system of the 'splanchnocranium' exhibits a normal spontaneous activity, which is mostly open in the laryngeal region and mostly closed in the anorectal continence organ. In animals missing an abdomen, e.g. turtles, we find that the complete abdominal muscle system is connected to the lungs functioning as respiratory muscles. The most powerful lungs that exist are found in birds. Their lungs, which are situated in a stiff thorax are only ventilated through the air compartments, mostly by the abdominal muscles. By this, the role of abdominal muscles for respiratory function is shown. We studied intensive care patients requiring ventilatory support and found that the electromyogram of the external abdominal oblique muscle can be impaired or extinguished. In some cases the cause is a polyneuropathy, which can be reversible. In consequence, positioning measures, as prone positioning are capable of preventing progressive deterioration of ventilation/perfusion relationship.

Resistive loading associated with breathing through a face mask (surgeons' paper mask) increases work of breathing significantly after a prolonged period of wearing. The additional resistive breathing due to a face mask may be intolerable for patients with preexisting overloaded respiratory muscle pump and contribute to inspiratory muscle fatigue.

There is no comprehensive theory for the various reasons for dyspnea. It is proposed to regard the disproportion between "input" and "output" as the common cause of the various forms. This disproportion may be located between psychological drive and neural response or between neural excitation and muscular response or between muscular activity and ventilatory effect. Thus insufficient perfusion of respiratory muscles--as in cardiac failure--may cause dyspnea. Arterial oxygen pressure as the criterion of sufficient ventilation is misleading in anemia and CO-poisoning, so that there is no dyspnea despite of insufficient O2-transport.

In end stage neuromuscular disease respiratory muscle fatigue can lead to respiratory failure. There is no close correlation between the degree of peripheral muscle weakness and the weakness of the respiratory muscles. Early in the disease the maximum in- and expiratory pressures can be abnormal even though the results of spirometry are normal. Progressive weakness of the respiratory muscles results in a decrease in vital capacity and eventually in alveolar hypoventilation, especially during sleep. General muscle weakness and fatigue may be the reasons why sleep hypoventilation is often overlooked in its early stages. Dyspnea may be a early symptom but it is not unusual that alveolar hypoventilation remains undetected until complications ensue (Cor pulmonale, polycythemia, altered alertness).