Respiratory muscles

Assess the patient s general appearance, use of accessory muscles, respiratory rate, heart rate, lung sounds, pulsus paradoxus, PEF, and oxygen saturation. 

Blood Skeletal muscle Respiratory volume activity activity... 

The diagnosis of GBS is primarily clinical. In the AIDP variant the majority of cases have some sensory symptoms or paresthesias at the onset of the disease however, abnormalities on sensory examination are less frequent. Pain, particularly low back, buttock, or thigh pain, is an early symptom in approximately 50% of patients. Subsequently the clinical picture is dominated by weakness often progressing to paralysis. Muscle weakness may begin in the low er limbs and ascend upw ards, characteristically involving both proximal and distal muscles. Respiratory muscles can be involved in up to one-third of the hospitalized patients. Complete or partial loss of reflexes is seen in almost all patients. Cranial nerve involvement is seen... 

In order to maximise the toxic potential of their venoms, many snakes have several toxins in their venoms which act by different biochemical mechanisms. This is an ingenious ploy which means that more than one of the bod/s vital systems is hit by the venom so making death more certain than if only one were hit. The Black Mamba is an excellent example of a snake with multiple toxic components in its venom. In addition to the fasciculins. Mamba venom has dendrotoxins which inhibit neurotransmission by blocking the exchange of + and - ions across the neuronal membrane. This prevents passage of the nerve impulse. If the impulse is en route to the big toe the toe will be paralysed — this is certainly not life-threatening. However, if the impulse is to the pulmonary muscles, respiratory failure and death will result. The dendrotoxins from the Black Mamba are very much less toxic than the fasciculins (it would take 1.6 g to kill a person), however the combined effect of the two toxins is far more toxic than the toxicities of the individual components (this is termed synergy) which is why the Black Mamba is lethal to humans. 

BIOLOGICAL ACTIONS Gastrointestinal smooth muscle Reproductive smooth muscle Respiratory smooth muscle Cardiovascular system Blood platelet aggregation Metabolic effects... 

From the nutritional point of view, haem pigments are of considerable importance in the supply of iron to the human organism. The so-caUed haem iron, which includes iron bound in myoglobin and haemoglobin and iron bound in muscle respiratory enzymes, is absorbed in the body at a level of 10-30%, whQe non-haem iron from only 1-5%. 

Patients with neuromuscular disorders (NMD) develop ventilatory failure because of a combination of dysfunctions of the inspiratoiy, expiratory, and bulbar-innervated muscles. Respiratory failure and the need for a tracheostomy are avoidable in most cases, using the approaches and interventions presented in this chapter. 

In conclusion, NPPV is increasingly used in children and infants. This expanding use contrasts with the limited proven benefits. Pediatricians, physiologists, nurses, physiotherapists, and technicians should combine their efforts to determine more accurately the physiological effects of NPPV, especially on the respiratory muscles, respiratory compliance and growth, central drive and psychoneurological development, so that it may be introduced at a time least likely to be harmfiil and most likely to be of benefit in improving respiratory function and health-related quality of life. 

Repeated exposures of animals to high (near-lethal) concentrations of vapors result in inflammation of the respiratory tract, as weU as degenerative changes in the Hver, kidneys, and heart muscle. These effects arise at concentrations far above those causing irritation. Such effects have not been reported in humans. The low odor threshold and irritating properties of acrylates cause humans to leave a contaminated area rather than tolerate the irritation. 

Ca " concentration, termed hypocalcemia, excitabihty increases. If this condition is not corrected, the symptoms of tetany, ie, muscular spasm, tremor, and even convulsions, can appear. Too great an increase in Ca " concentration, hypercalcemia, may impair muscle function to such an extent that respiratory or cardiac failure may occur. 

Isoflurane is a respiratory depressant (71). At concentrations which are associated with surgical levels of anesthesia, there is Htde or no depression of myocardial function. In experimental animals, isoflurane is the safest of the oral clinical agents (72). Cardiac output is maintained despite a decrease in stroke volume. This is usually because of an increase in heart rate. The decrease in blood pressure can be used to produce "deHberate hypotension" necessary for some intracranial procedures (73). This agent produces less sensitization of the human heart to epinephrine relative to the other inhaled anesthetics. Isoflurane potentiates the action of neuromuscular blockers and when used alone can produce sufficient muscle relaxation (74). Of all the inhaled agents currently in use, isoflurane is metabolized to the least extent (75). Unlike halothane, isoflurane does not appear to produce Hver injury and unlike methoxyflurane, isoflurane is not associated with renal toxicity. 

Desflurane is less potent than the other fluorinated anesthetics having MAC values of 5.7 to 8.9% in animals (76,85), and 6% to 7.25% in surgical patients. The respiratory effects are similar to isoflurane. Heart rate is somewhat increased and blood pressure decreased with increasing concentrations. Cardiac output remains fairly stable. Desflurane does not sensitize the myocardium to epinephrine relative to isoflurane (86). EEG effects are similar to isoflurane and muscle relaxation is satisfactory (87). Desflurane is not metabolized to any significant extent (88,89) as levels of fluoride ion in the semm and urine are not increased even after prolonged exposure. Desflurane appears to offer advantages over sevoflurane and other inhaled anesthetics because of its limited solubiHty in blood and other tissues. It is the least metabolized of current agents. 

Morphine has certain undesirable side effects. Among these are respiratory depression, nausea, and vomiting, depression of the cough reflex, cardiovascular depression and hypotension, smooth muscle contraction (constipation), and histamine release (93). Morphine s onset of action, duration, and low therapeutic indices have prompted a search for a more effective opiate iv anesthetic. Extreme simplification of the complex morphine molecule has resulted in anilido —piperidines, the fentanyl class of extremely potent opiate iv anesthetics (118,119). 

Airway cross-sections have the nominal anatomy shown in Fig. 5.16. Airway surface liquid (AST), primarily composed of mucus gel and water, surrounds the airway lumen with a thickness thought to vary from 5 to 10 mm. AST lies on the apical surface of airway epithelial cells (mostly columnar ciliated epithelium). This layer of cells, roughly two to three cells thick in proximal airways and eventually thinning to a single cell thickness in distal airways, rests along a basement membrane on its basal surface. Connective tissue (collagen fibers, basement membranes, elastin, and water) lies between the basement membrane and airway smooth muscle. Edema occurs when the volume of water within the connective tissue increases considerably. Interspersed within the smooth muscle are respiratory supply vessels (capillaries, arteriovenous anastomoses), nerves, and lymphatic vessels. 

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