Pulmonary function tests
Measurement of PEFR may occasionally provoke cardiorespiratory arrest in severe asthma. Indeed, in contrast with normal subjects, deep inspiration in sthmatics induces bronchoconstriction and may promote coughing. PEFR should not be measured in a patient experiencing severe asthma, i.e. unable to speak; it is below 100 l/min. However, repeated PEFR measurements are of value later, when major bronchial obstruction is relieved, to monitor response to therapy and stabilization. When PEFR values checked prior to hospital admission disclose unstable asthma with profound morning dips, sudden respiratory arrest is a real threat.
Chest radiographs show what is expected from clinical examination, i.e lung hyperinflation, sometimes associated with small heart size. They should be obtained to exclude pneumothorax, pneumomediastinum, pneumonia, or other diseases mimicking bronchial obstruction.
ECG abnormalities are common and non-specific. They reveal tachycardia, arrhythmias, and right ventricular strain (right QRS axis deviation, repolarization abnormalities, P pulmonale, and partial right bundle branch block).
Arterial blood gas monitoring is mandatory. Respiratory alkalosis with or without hypoxemia is expected first ( Table. ...1, stages I-II). Normocapnia with hypoxemia reflects hypoventilation (stage III) and should alert the physician. The extreme situation favors the development of hypercapnic and possibly metabolic acidosis (stage IV).
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If you suffer with asthma, you will no doubt be familiar with the uncomfortable sensations as your bronchial tubes begin to narrow and your muscles around them start to tighten. A sticky mucus known as phlegm begins to produce and increase within your bronchial tubes and you begin to wheeze, cough and struggle to breathe.