Diaphragmatic weakness

Atropine is an antidotal treatment. It is used to reverse the muscarinic signs, but it will not reverse the nicotinic effects (muscular weakness, diaphragmatic weakness, etc.). Atropine blocks the effects of accumulated acetylcholine (ACh) at the synapse and should be continued until the nerve agent is metabohzed (Midthng et al, 1985). Over-atropinization can cause hyperthermia, tachycardia, agitation, mydriasis, and ileus, which can be life threatening in the horse (Meerstadt, 1982). 

Figure 5 Transdiaphragmatic twitch pressure recorded in mechanically ventilated patients recovering from an episode of acute respiratory failure. Box represents range of transdiaphragmatic twitch pressures recorded in ambulatory patients with severe COPD. Most mechanically ventilated patients had evidence of diaphragmatic weakness [data from Ref. 62 (open circles), and from Ref 61 (closed circles)]. Abbreviation COPD, chronic obstructive pulmonary disease. Source From Refs. 44.

Lechtzin N, Wiener CM, Shade DM, et al. Spirometry in the supine position improves the detection of diaphragmatic weakness in patients with amyotrophic lateral sclerosis. Chest 2002 121 436-442. 

Skeletal muscle dysfunction can cause myalgia, bone pain, weakness, and potentially fatal rhabdomyolysis. Respiratory muscle weakness and diaphragmatic contractile dysfunction can cause acute respiratory failure. 

Botulinum toxins Toxin aerosolized or added to food or virater. Exposed to food orvirater. Exposed surfaces may be contaminated vifith toxin. Toxic dose 0.01 mcg/kg for Inhalation and 70 meg for Ingestion. Hours to a few days See p 136. Symmetric, descending flaccid paralysis with Initial bulbar palsies (ptosis, diplopia, dysarthria, dysphagia) progressing to diaphragmatic muscle weakness and respiratory arrest. Dry mouth and blurred vision due to toxin blockade of muscarinic receptors. Toxin cannot penetrate intact skin but is absorbed across mucous membranes or wounds. Treatment botulinum antitoxin (see p 420). 

Other metabolic factors contributing to PMV include hypophosphatemia and hypomagnesemia, both of which have been associated with diminished diaphragmatic function. Hypothyroidism is an uncommon cause of ventilator dependency (27), being associated with respiratory muscle weakness as well as altered ventilatory drive and upper airway obstruction. Hypothyroidism is a potentially treatable cause of failure to wean and it should be considered in patients with prolonged ventilator dependence. 

Abnormal gas exchange, malnutrition, and prolonged use of controlled ventilation, leading to selective diaphragmatic muscle atrophy, add to peripheral and respiratory muscle weakness (38). Many of the above reasons make it likely that patients will benefit from PT that targets respiratory and skeletal muscle function, although clearer evidence of positive outcomes is still required (53). Inspiratory muscle training has been shown to facilitate... 

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