Constricted airways

Histamine, whose release in the body triggers nasal secretions and constricted airways, has three nitrogen atoms. List them in order of increasing basicity, and explain your ordering. 

Airway obstruction manifests itself as symptoms such as chest tightness, cough, and wheezing. Airway obstruction can be caused by multiple factors including airway smooth muscle constriction, airway edema, mucus hypersecretion, and airway remodeling. Airway smooth muscle tone is maintained by an interaction between sympathetic, parasympathetic, and non-adrenergic mechanisms. Acute bronchoconstriction usually... 

Adrenaline, which turns on both receptors, increases heart rate via the beta-1 receptor and dilates airways by the beta-2 receptors. Propranolol, which is a nonspecihc blocker of both beta-1 and beta-2 receptors, decreases heart rate and lowers blood pressure, beta-1 receptor action, but can constrict airways in the lung, beta-2 receptor action, and that is not so good. 

The fourth sentence of the second paragraph explains that during an attack the person afflicted with asthma will compensate for constricted airways by breathing a greater volume of air. 

C. Glaucoma as a preexisting condition does not contraindicate an AChE inhibitor. The other preexisting conditions preclude the administration of AChE inhibitors. Potentiation of parasympathetic stimulation can constrict airway smooth muscle and aggravate asthma, further weaken A-V conduction, and risk perforation of the bowel if an obstruction is present. 

For inhalational induction of anaesthesia in children, 6% sevoflurane in 50% nitrous oxide and oxygen is probably optimal. However, some anaesthetists consider it to be inferior to halothane for the management of the irritable or constricted airway and for anaesthesia for bronchoscopy. Sevoflurane is preferred for dental procedures as there is a lower risk of cardiac arrhythmias than with halothane, especially in children. In children with congenital heart disease, whereas the cardiac index is reduced by halothane it is preserved with sevoflurane. In adults, 8% sevoflurane is well tolerated and, provides rapid induction of anaesthesia without adversely affecting haemodynamic stability. 

As noted previously, the airways are richly supplied with afferent and efferent vagal nerves. The cholinergic motor fibers are clearly responsible in some patients for a portion of the bronchoconstriction characteristic of acute asthma. Such fibers innervate M3 receptors on the smooth muscle and contain modulatory M2 receptors on the nerve terminals. Selective inhibition of M2 receptors can increase bronchoconstrictor responses to a variety of stimuli, while M3 inhibitors can produce dilation of constricted airways. 

Respiratory Difficult breathing, constricted airways Normal, then progressive paralysis Nonproductive cough In severe cases chest pain, difficult breathing... 

Ramchandani RP, Shen X, Gunst SJ, Tepper RS. Comparison of inner wall areas of non-constricted airways from immature and mature rabbits. Am J Respir Crit Care Med 1999 159 A406. 

In diseased lungs, the airways are often more constricted relative to healthy lungs, so one might expect significant differences in lung deposition fraction and deposition pattern (101). The impact of constriction on aerosol deposition is discussed below. We present deposition data based on models of constricted airways as well as experimentally derived data, taken from healthy subjects in which constriction was induced by methacholine provocation, and from patients who are constricted in their baseline state. 

Anderson et al. asked five asthmatic volunteers (mean FEVj 40% of predicted) to inhale NaCl particles ranging from 0.02-0.24 pm. Total deposition of these particles was measured as the difference between the inhaled fraction and the exhaled fraction. When they compared total deposition fraction in the asthma patients to that observed in a group of normal subjects, they found that the deposition fraction was higher in the patients with asthma Anderson concluded that this was partly due to the patients constricted airways, bnt it may also have been due to a longer residence time for particles in the asthmatic airways, since the asthmatic volunteers breathed more slowly than the healthy volunteers (6). 

The impact of constricted airways on aerosol deposition appears to be as follows ... 

The known and potential health risks from inhaled chemicals are nearly as diverse as the chemicals themselves. Effects in the respiratory tract may inclnde irritation, airway constriction, airway sensitization, impairment of clearance, inflammation, tissue destruction, edema, pneumoconiosis, fibrosis, emphysema, and cancer. For soluble chemicals, the respiratory tract may serve primarily as a portal of entry, and the toxic effects may be manifested elsewhere. In such instances, there may be little difference in effect between irrhalation and other routes of exposure except for effects that might occur in the respiratory tract as the chemicals pass through it. Inhaled chemicals may also be metabolized in the respiratory tract, giving rise to toxic metabolites that manifest their effects either in the respiratory tract or elsewhere. 

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