The applied physiology of cough.

The cough reflex is such an important defense mechanism of the respiratory tract that a thorough knowledge of its applied physiology in respiratory disease is essential for clinicians. It is a well-integrated reflex, which has afferent limb consisting of receptors and afferent nerves, the central cough center in the brainstem and the efferent limb consisting of motor nerves supplying the muscles of coughing. The cough process consists of inspiratory phase, compressive phase and expiratory phase. Stimuli that can initiate the cough process can be central or peripheral in the lungs or outside the lungs. The important function of the cough reflex is to maintain the airways and alveoli clear and healthy. The mechanisms by which it achieves this are (i) high velocity of expiratory gas flows produced in the expiratory phase (ii) the compression of the lungs and airways by high positive pleural pressure generated in the compressive phase. Cough threshold can be determined by giving acetic acid, citric acid or capsaicin inhalation challenge test. This has practical application in clinical research. The pathophysiological basis of different types of cough encountered in clinical practice is discussed.

Childhood asthma--office management.

Childhood asthma is a major problem in office practice. For an acute life threatening attack (which is indicated by presence of severe distress, pulsus paradoxus, oxygen saturation less than 93%, cyanosis, peak expiratory flow rate of less than 50% of predicted) child should be directly admitted in intensive care unit. If it is a non life threatening attack the child can be managed in the office. Initially, the child should be given b2 agonists by inhalation route with either metered dose inhaler (MDI), MDI with spacer or nebuliser. It there is severe bronchospasm or inhalation therapy is not possible then epinephrine of b2 agonists may be given subcutaneously. The medications can be repeated 2-3 times. If response is adequate the child may be sent home on b2 agonist by oral or inhalation route at an interval of 406 hours. In case of inadequate response the child is started on oral or parenteral corticosteroids. Even after steroids if inadequate response the child is started on intravenous theophylline. Once the acute exacerbation is controlled the child is assessed for starting maintenance therapy. For this purpose his illness is graded from stage I to V depending on the severity. For stage I and II b2 agonists are prescribed as and when required. For stage III sodium cromoglycate by inhalation should be prescribed. For stage IV inhalation steroids in usual doses and for stage V inhalation steroids in higher doses are prescribed along with a minimum dose of oral steroids is added. For symptomatic control slow release theophylline or long acting b2 agonists may be added along with maintenance therapy as and when required. Apart from medications a proper education of parents and patients is necessary to improve the outcome of asthma by increasing the compliance and better control of environment.

Malignant hypertension due to reflux nephropathy in an adolescent (a case report).

Malignant hypertension in an adolescent due to reflux nephropathy (RN) is rare. Here we are presenting such a case unassociated with the usual symptoms of hypertension. The problems of diagnosis, management, prognosis and prevention of RN are discussed with a review of relevant literature.

Congenital intermittent atrio-ventricular dissociation in tetralogy of Fallot (a case report).

A case of tetralogy of fallot with congenital intermittent atrioventricular dissociation is reported. A review of standard postgraduate books of cardiology fails to describe this condition, thus showing its extreme rarity. The therapeutic dilemma in treating such a case is also discussed.

Congenital lipodystrophy with defective leucocyte function (a case report).

A 6 1/2 year old female child with congenital lipodystrophy is being presented. The noteworthy feature in this case was the defective leucocyte function and its association with tuberculous pericardial effusion.

Late hemorrhagic disease of infancy.

Over a period of 1 1/2 years, 9 infants ages ranging between 3 weeks and 7 months presented with the syndrome of late hemorrhagic disease related to vitamin K deficiency. All were exclusively breast fed and had not received vitamin K at birth. Four of these had acute intracranial hemorrhage, of which 2 expired and the surviving 2 have residual neurologic handicap. Of the remaining 5 who had skin and mucosal bleeds, all recovered on administration of vitamin K.