Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0020440 (hypercapnia)
 7,939 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Intermittent mechanical ventilation via nasal CPAP mask was provided to 13 patients admitted to this institution for exacerbation of chronic respiratory failure. Ten suffered from COPD, two suffered from obesity hypoventilation syndrome (OHS), and one from severe hypothyroidism. All except one presented with dyspnea and hypercapnia due solely to progression of their underlying disease processes. Six of the patients with COPD and the patient with hypothyroidism responded to positive pressure ventilation by mask with improvements in blood gas values and clinical status. The remaining two patients with COPD and the two patients with OHS were unable to use the system. Four of the patients with COPD and chronic respiratory failure have been subsequently maintained on daily volume ventilation via nasal mask for about 20 months with persistent clinical and physiologic improvements. Application of volume ventilation through the nasal CPAP mask is a feasible strategy for providing long-term mechanical ventilation to selected patients with COPD and respiratory failure.
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PMID:Intermittent volume cycled mechanical ventilation via nasal mask in patients with respiratory failure due to COPD. 155 51

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.
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PMID:Hypothyroidism. A reversible cause of diaphragmatic dysfunction. 280 37

To define the prevalence of impaired ventilatory responses in hypothyroidism, clinical and chemical parameters predicting their presence, and the potential for their acute reversal, ventilatory responses to hypercapnia and hypoxia were studied in 38 hypothyroid patients before treatment, and after short-term (seven days) and long-term (12 to 24 weeks) thyroid hormone therapy. Before treatment, hypercapnic ventilatory responses were blunted in 10 of 29 patients (34 percent), whereas hypoxic ventilatory responses were abnormal in eight of 30 patients (27 percent). Hypothyroid women and patients with marked pretreatment elevation of the serum thyrotropin concentration (greater than 90 mU/liter) were significantly more likely to have impaired ventilatory responses. In patients with an abnormal pretreatment response, parenteral thyroid hormone therapy (25 to 50 micrograms of L-triiodothyronine or 100 micrograms of L-thyroxine per day for seven days) significantly enhanced hypercapnic (0.75 +/- 0.06 to 1.19 +/- 0.16 liters/minute/mm Hg, p less than 0.05) and hypoxic (93 +/- 12 to 176 +/- 31 liters.mm Hg/minute, p less than 0.05) ventilatory responsiveness acutely. In seven of nine patients with abnormal pretreatment hypercapnic responses, and six of eight patients with abnormal hypoxic responses, normal ventilatory responsiveness was restored after one week of therapy. It is concluded that: (1) a subset of hypothyroid patients have blunted ventilatory responses to hypercapnia and/or hypoxia; (2) hypothyroid women and patients with a serum thyrotropin greater than 90 mU/liter more often manifest this abnormality; and (3) thyroid hormone therapy for one week reverses impaired ventilatory responses in hypothyroidism.
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PMID:Prediction and reversal of blunted ventilatory responsiveness in patients with hypothyroidism. 336 47

Physiological studies performed 1 week after initiation of thyroid replacement showed persistence of significant respiratory muscle weakness in a patient presenting with hypothyroidism and hypercapnia. Repeat studies 12 months later demonstrated return of respiratory muscle strength to normal. Earlier reports on respiratory failure in hypothyroidism had postulated a critical role for respiratory muscle weakness in the genesis of hypercapnia. Since hypercapnia was rapidly reversed despite the persistence of severe respiratory muscle weakness, this explanation may not be always correct. It appears than in our patient thyroid replacement had its primary effect on the respiratory control system.
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PMID:Reversible respiratory muscle weakness in hypothyroidism. 362 Mar 25

Alveolar hypoventilation is known to occur in myxedema. Reduction of hypercapnic ventilatory drive has not been reported, up to now, in patients with short-term hypothyroidism. Eleven patients with short-term hypothyroidism, before and after L-triiodothyronine (L-T3) replacement therapy, and 10 normal controls were studied. Hypercapnic ventilatory drive was assessed by the evaluation of the relation between the response of ventilation and mean expiratory flow to CO2 rebreathing and by the evaluation of ventilation and mean expiratory flow at a fixed level of carbon dioxide. In patients with short-term hypothyroidism these parameters were reduced as compared with normal controls and returned to normal after L-T3 replacement. We conclude that hypercapnic ventilatory drive is blunted by short-term hypothyroidism and normalizes following replacement therapy.
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PMID:Impaired ventilatory drive in short-term primary hypothyroidism and its reversal by L-triiodothyronine. 383 97

This is a report of a 45-yr-old male patient who developed central sleep apnea syndrome because of hypothyroidism. In response to L-thyroxine therapy, the patient became euthyroid, and the apneic phenomenon disappeared. Previous reports have suggested that hypothyroidism can produce obstructive sleep apnea from either narrowing of the upper airway secondary to deposition of mucopolysaccharides and protein extravasation into the tissues or from abnormalities in ventilatory control. The present patient did demonstrate evidence of profound dysfunction of his respiratory control center: before therapy, the patient manifested blunted ventilatory and occlusion pressure responses to hypoxia and normal responsiveness to hypercapnia; after therapy, hypoxic responsiveness was restored and the ventilatory response to hypercapnia doubled. Hypothyroidism should be included in the differential diagnosis of central sleep apnea.
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PMID:Central sleep apnea in hypothyroidism. 683 58

A review of the relevant literature was stimulated by recent publications urging extensive laboratory assessment of elderly patients presenting with intellectual impairment. Published data regarding reversible causes of impairment are limited and exist only for hospitalized patients, with rare exceptions. The frequencies of azotemia, hyponatremia, volume depletion, hypoglycemia, cardiac arrhythmia, cerebrovascular disease, sensory impairment, hypercarbia, congestive heart failure, infections, subdural hematoma, and chemical intoxications as causes of the intellectual impairment are entirely unknown. It is reported that 8 per cent of patients hospitalized for dementia are depressed; alcoholism is causative in 8 to 13 per cent of patients with mental impairment; normal pressure hydrocephalus is reported in 7 to 12 per cent. The frequency of the latter conditions in outpatients is not known. While estimates exist for the frequencies of hypothyroidism, hyperparathyroidism, neurosyphilis, and vitamin B12 and folate deficiencies among the elderly, no prevalence data exist for these disorders among the intellectually impaired.
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PMID:Reversible intellectual impairment: an internist's perspective. 711 32

Three consecutive cases of myxedema coma treated successfully with either nasogastric or intravenous route of administration of I-triiodothyronine, followed by oral thyroxine, are described. All were hypothermic, had biochemical evidence of advanced hypothyroidism (T4 less than 1.0 micrograms/dl, T3 less than 20 ng/dl and TSH greater than 150 microU/ml), severe hypoxemia, respiratory acidosis, hypercarbia and temporary depression of respiratory center responsiveness. In only one patient it was found significant hyponatremia (Na = 127 mEq/l). Two patients were successfully treated with the nasogastric route of administration of T3 (12.5 micrograms/6h) but in a female patient with intestinal atony (ileus) there was no absorption of the orally administered T3. Intravenously administered T3 promptly corrected the hypometabolic state in this patient. It was confirmed that T4 therapy, although promptly correcting low serum T4 concentration, failed to rise serum T3 levels due to lack of peripheral T4 5'-monodeiodination to T3 in these critically ill patients.
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PMID:Management of myxedema coma: report on three successfully treated cases with nasogastric or intravenous administration of triiodothyronine. 715 77

The purpose of this study was to investigate the role of peripheral chemoreceptor activity on the hypoxic and hypercapnic ventilatory drives in rabbits with induced hypothyroidism. Experiments were carried out in control and hypothyroid rabbits. Hypothyroidism was induced by an administration of an iodide-blocker, methimazole in food (75 mg/100 g food) for ten weeks. At the end of the tenth week, triiodothyronine (T3) and thyroxine (T4) levels significantly decreased (P<0.001) while thyroid stimulating hormone (TSH) increased (P<0.001). Tidal volume (VT), respiratory frequency (f/min), ventilation minute volume (VE) and systemic arterial blood pressure (BP) were recorded during the breathing of the normoxic, hypoxic (8% O2-92% N2) and hypercapnic (6% CO2-Air) gas mixtures, in the anaesthetised rabbits of both groups. At the end of each experimental phase, PaO2, PaCO2, and pHa were measured. The same experimental procedure was repeated after peripheral chemoreceptor denervation in both groups. VT significantly decreased in some of the rabbits with hypothyroidism during the breathing of the hypoxic gas mixture (nonresponsive subgroup) (P<0.05). After chemodenervation, a decrease in VT was observed in this nonresponsive subgroup during normoxia (P<0.05). The percent decrease in VT in nonresponsive subgroup of hypothyroid rabbits after chemodenervation was lower than that of the chemodenervated control animals (P<0.01). When these rabbits with hypothyroidism were allowed to breath the hypercapnic gas mixtures, increases in VT and VE were not significant. In conclusion, although there is a decrease in peripheral chemoreceptor activity in hypothyroidism, it does not seem to be the only cause of decrease in ventilatory drive during hypoxia and hypercapnia.
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PMID:The role of peripheral chemoreceptor activity on the respiratory responses to hypoxia and hypercapnia in anaesthetised rabbits with induced hypothyroidism. 1561 33

Myxedema coma is the term given to the most severe presentation of profound hypothyroidism and is often fatal in spite of therapy. Decompensation of the hypothyroid patient into a coma may be precipitated by a number of drugs, systemic illnesses (eg, pneumonia), and other causes. It typically presents in older women in the winter months and is associated with signs of hypothyroidism, hypothermia, hyponatremia, hypercarbia, and hypoxemia. Treatment must be initiated promptly in an intensive care unit setting. Although thyroid hormone therapy is critical to survival, it remains uncertain whether it should be administered as thyroxine, triiodothyronine, or both. Adjunctive measures, such as ventilation, warming, fluids, antibiotics, pressors, and corticosteroids, may be essential for survival.
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PMID:Myxedema coma. 1712 41


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