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Query: UMLS:C0020440 (hypercapnia)
 7,939 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Six young male patients with grade I (mild) myotonic dystrophy and a complaint of excessive daytime sleepiness were studied during wakefulness and sleep. Pulmonary function tests during wakefulness showed evidence of mild abnormality related to respiratory muscle weakness. During sleep, some patients developed a sleep apnea syndrome with high sleep Apnea Indices. There was no relation between hypoxic and hypercapnic ventilatory responses during wakefulness and sleep Apnea Indices. But hypoxemia and hypercapnia worsened considerably during REM sleep. Myotonic dystrophy patients with sleep apnea presented increased pulmonary and systemic arterial pressures during sleep. It was also during sleep that arrhythmias were observed.
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PMID:Respiratory and hemodynamic study during wakefulness and sleep in myotonic dystrophy. 22 21

Patients with myotonic dystrophy often develop respiratory failure caused by alveolar hypoventilation. Abnormalities in the ventilatory response to hypoxia and hypercapnia may explain this phenomenon. Accordingly, hypoxic and hypercapnic responses were measured in seven patients with myotonic dystrophy who had only mild respiratory muscle weakness. Hypoxic response was significantly reduced, while hypercapnic response was affected more irregularly. It is possible that the high incidence of respiratory failure in such patients is related to decreased hypoxic ventilatory response, occurring because of an underlying neurogenic deficit.
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PMID:Ventilatory response in myotonic dystrophy. 56 10

Although central nervous system (CNS) involvement, such as intellectual impairment simulating dementia, in myotonic dystrophy (MyD) has been well documented, the cause of this condition remains unclear. In has been reported that the progressive cases of MyD are often accompanied with respiratory disturbance and sleep apnea syndrome (SAS). We studied the relation between CNS involvement and respiratory disorders in 15 MyD patients. They consisted of 10 males and 5 females with ages ranging from 21 to 58 years (average 46 +/- 8.4 years old). Arterial blood gas (ABG) analysis, respiratory function test, and monitoring of arterial oxygen saturation (SaO2) during sleep were carried out. In some cases abnormal respiration during sleep was analyzed with polysomnography. For an assessment of CNS involvement the following examinations were performed; intelligence quotient (WAIS-IQ); electroencephalography (EEG); brain computed tomography (CT); and cerebrospinal fluid (CSF) levels of neuron-specific enolase (NSE), S-100b and creatine kinase BB isoenzyme (CK-BB) which were estimated by using enzyme immunoassay. ABG analysis demonstrated the presence of hypercapnia (PaCO2 > 45 torr) during wakefulness in MyD patients. During sleep 14 of the 15 patients showed frequent desaturation phenomenon (SaO2 < 90%), indicating the episodic hypoxemia. Polysomnographic study revealed the occurrence of SAS of both obstructive and central types in all the cases examined. IQ test disclosed intellectual impairment in 80% of the 15 patients, and EEG showed slowing of basic rhythm in the majority of the cases. On brain CT both enlarged ventricles and dilated sulci were commonly observed.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Central nervous system disorders in patients with myotonic dystrophy--in relation to respiratory dysfunction]. 142 35

A 36-year-old woman with myotonic dystrophy presented with generalized weakness and daytime somnolence. Arterial blood gas analysis revealed significant hypoxemia and hypercapnia, and a polysomnogram revealed additional oxygen desaturation during sleep. For nocturnal ventilatory assistance, the patient received positive-pressure ventilation via a nasal mask. This mode of ventilation produced marked improvement in the patient's nocturnal hypoxemia.
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PMID:The use of mechanical ventilation via a nasal mask in myotonic dystrophy. 155 16

We have previously shown that the chemosensitivity of the respiratory centers is well preserved in myotonic dystrophy but that the ventilatory output is reduced. The present study was designed to determine at which degree of ventilatory performance weakness and fatigability of the respiratory muscles are interfering with ventilation and which mechanical factors contribute to the tachypnea of patients with myotonic dystrophy at rest and during low ventilatory output. We studied 10 patients with the disease and 10 normal control subjects. The strength of respiratory muscles was assessed by measurements of maximal pressure-volume diagrams generated against airway occlusion. Performance was evaluated during 1-min maximal voluntary ventilation (1-min MVV) test, during 7-min 7% CO2 breathing and during quiet breathing. Occlusion pressure (P0.1) in patients at rest was slightly higher than in control subjects, and during CO2 breathing, it was similar to that of control subjects. Maximal static pressure was reduced in patients to an average of 35% of that of control subjects. During the 1-min MVV test, there was a 50% reduction in esophageal and transdiaphragmatic pressure output (Pes, Pdi) in patients, resulting in similar reduction in ventilation (VE) and patients had rapid cycles of alternating dominant thoracic and abdominal volume displacements (Vrc/Vabd) suggesting respiratory muscle fatigue. During the 3- to 4-fold increase in breathing drive induced by hypercapnia, pressure output and the Vrc/Vabd were identical in both groups. However, ventilation was reduced in patients who had tachypneic respiration. In patients, tachypnea was also observed during quiet breathing. This tachypnea was associated with higher impedance of the respiratory system (Zrs) in patients and identical impedance of the lung (ZL) in both groups. In addition, Pdi during tidal volume was significantly higher in patients. These data demonstrate that the ventilatory output in out patients was altered predominantly by weakness and fatigability of the respiratory muscles during high ventilatory performance and by increased impedance of the respiratory system at lower degrees of ventilation.
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PMID:Pathogenesis of respiratory insufficiency in myotonic dystrophy: the mechanical factors. 680 50

Respiratory impairment in patients with Steinert's muscular dystrophy is known to lead to respiratory failure. Both the blunted chemical drive of breathing and the respiratory muscle weakness have been cited in the pathophysiology of premature death in these patients. To further assess the chemical control of breathing in these patients, we measured their respiratory responses to hypoxia (Weil's method), hyperoxia (Dejours' method), and hypercapnia (Read's method). In response to the stimuli from these respiratory centers, minute ventilation (VE), tidal volume (VT), respiratory frequency (F), mean inspiratory flow rate (VT/Ti), and occlusion pressure (P0.1) were measured in 12 patients and in 12 normal persons matched to the patients on the basis of age, sex, and arm span. The patients were similar to the control subjects in occlusion pressure results. However, they differed significantly (P less than 0.01) in ventilatory responses by a lower VE, lower VT, higher F, and lower VT/Ti in response to the hypercapnia and hypoxia tests. The responses of patients and control subjects were similar during the hyperoxia tests. Our study, therefore, established that the chemosensitivity of the respiratory centers, as measured by P0.1, is well preserved in Steinert's myotonic dystrophy, but the output to breathing (VE, VT, F, VT/Ti) is modulated by the impaired respiratory mechanics causing a tachypneic breathing pattern, even in the absence of restricted lung volume.
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PMID:Control and modulation of respiration in Steinert's myotonic dystrophy. 736 35

We reported a 39-year-old man with myotonic dystrophy. He suffered from morning headache. Respiratory function tests showed restrictive pattern and arterial gas analysis showed hypoxia and hypercapnia with respiratory acidosis (PaCO2 50.8 mmHg, PaO2 63.8mmHg, pH 7.317, SaO2 89.8%). Polysomnograph showed central apneas exclusively in light sleep (stage 1 and 2). O2 saturation fell at most to as low as 50% during the apneas. We conclude that sleep apnea should be consider in patients with myotonic dystrophy associated with morning headache.
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PMID:[A case of myotonic dystrophy with morning headache following sleep apnea syndrome]. 766 17

Serial assessments of respiratory function were performed over 1 to 8 years in 12 patients with myotonic dystrophy. Respiratory parameters included vital capacity (percentage of predicted value; %VC) and one-second forced expiratory volume (percentage of predicted value; FEV1.0%) on spirogram and arterial blood gases at rest. The patients who had no primary respiratory disease were ranged in age from 31 to 61 years, with an average age of 47 years, and their mean duration of illness was 20 years. All the subjects were severely disabled; only two patients were able to walk with assistance, but other ten patients were confined to a wheelchair. During the observation period, five patients died; 4 due to respiratory failure and one cardiac and respiratory failure. The following results were obtained: (1) almost all the patients showed a reduction in %VC, the severity of which was gradually progressed with advancing age. A significant negative correlation was observed between %VC and duration of illness. (2) PaCO2 was negatively correlated with %VC, while the relationship between PaO2 and %VC appeared to be a significant positive correlation. Chronic alveolar hypoventilation (hypercapnia and hypoxemia) was particularly likely when vital capacity (VC) was less than 40% of the predicted value in the patients. This study indicates that a reduction of VC plays an important role in development of respiratory failure in myotonic dystrophy and serial measurements of VC and arterial blood gases are useful in the detection of it.
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PMID:[Serial observations of respiratory function in disabled patients with myotonic dystrophy]. 826 95

We studied 134 patients with Steinert's myotonic dystrophy (MD) in order to determine the prevalence of chronic hypercapnia, the level of muscle weakness and forced expiratory volume at which hypercapnic respiratory failure is likely to occur, and how clinical assessment might help predict hypercapnic respiratory failure. Subjects were divided into five classes with a muscular disability rating scale (MDRS): 0 = no clinical impairment (n = 9), I = minimal signs of impairment (n = 11), II = distal weakness (n = 41), III = moderate proximal weakness (n = 62), and IV = nonambulatory (n = 11). The prevalence of hypercapnia (PaCO2 > or = 43 mm Hg) was found to be 0%, 27%, 29%, 45% and 55% for MDRS 0 to 4, respectively (p = 0.03). A multiple regression analysis limited to clinical data showed that daytime hypersomnolence was a significant cofactor with the MDRS (p = 0.01) in predicting PaCO2 (r = 0.40). Among respiratory parameters, FVC, respiratory muscle strength (RMS), and maximal inspiratory pressure against occluded airways (PImax) were found to be predictors of nearly equal strength, explaining 16%, 15%, and 14% of the PaCO2 variance, respectively. In multiple regression analysis, sex, daytime sleepiness, and the expected/observed FVC ratio for a given RMS were found to be significant cofactors with PImax in predicting PaCO2 (r = 0.51). It is concluded that respiratory insufficiency should be suspected in MD patients with proximal weakness or daytime sleepiness. The likelihood of hypercapnia also increases with volume restriction and respiratory muscle weakness. Our study suggests that the combination of inspiratory muscle weakness and loading plays a predominant role in the pathogenesis of chronic alveolar hypoventilation in MD patients. The occurrence of daytime hypersomnolence suggests that other factors, such as low central ventilatory drive or sleep apnea, might play an additional role.
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PMID:Relationship between chronic hypercapnia and inspiratory-muscle weakness in myotonic dystrophy. 923 Jul 37

Involvement of respiratory muscles is a nearly constant feature of neuromuscular disorders, leading to respiratory failure. A careful respiratory follow up adapted to the variable time course of each disease is therefore mandatory. As the first step, a systematic clinical evaluation is essential to detect the subtle respiratory symptoms and signs related to respiratory muscle failure. Dyspnea and orthopnea are often late findings in patients with a usually severe functional impairment due to peripheral muscle weakness. Nocturnal respiratory events (obstructive sleep apnea syndrome and hypoventilation) are strongly suggested by daytime hypersomnolence and frequent morning headaches. Physical evaluation is essential to detect accessory muscle recruitment, supine abdominal paradox, and encumbrance of upper or lower airways. Vital capacity (VC) is the most classical lung function test. The major limitation of spirometry is its poor sensitivity to detect a moderate inspiratory muscle weakness. Supine VC may improve the detection of diaphragmatic involvement. Peak expiratory flow during cough (cough PEF) gives an overall evaluation of cough efficiency, values below 160 to 270 L/min suggesting poor airway clearance. Arterial blood gases are performed in case of clinical signs, significant deterioration of lung function tests, or sleep desaturations. Hypercapnia is weakly related to lung function results in patients with Steinert dystrophy and those with bulbar involvement. A specific evaluation of respiratory muscle strength is mandatory, as these tests are both sensitive and highly prognostic. Possible discrepancies (particularly in bulbar patients) between maximal inspiratory pressure (PImax) and sniff nasal inspiratory pressure (SNIP) justify to perform both measurements and to select the highest pressure. A maximal expiratory pressure (PEmax) below 45 cm H2O may indicate a compromised cough efficiency but the correlation with cough PEF may be poor. A screening nocturnal oxymetry is useful to detect sleep apneas and hypoventilation. Criteria defining significant desaturations remain however controversial. Suspicion of obstructive sleep apnea syndrome on clinical grounds or oxymetry findings should be confirmed by a conventional polysomnography.
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PMID:[Neuromuscular disorders - assessment of the respiratory muscles]. 1658 4


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