In a moderately severe asthma episode, the respiratory rate also is increased. Typically, accessory muscles of respiration are used. The heart rate is 100-120 beats/min. Loud expiratory wheezing can be heard, and pulsus paradoxus may be present (10-20 mm Hg). Oxyhemoglobin saturation with room air is 91%-95%. Patients experiencing a moderately severe episode are breathless while talking, and infants have feeding difficulties and a softer, shorter cry. In more severe cases, the patient assumes a sitting position.
In a severe asthma episode, patients are breathless during rest, are not interested in eating, sit upright, talk in words rather than sentences, and are usually agitated. In a severe episode, the respiratory rate is often > 30 breaths/min. Accessory muscles of respiration are usually used, and suprasternal retractions are commonly present. The heart rate is > 120 beats/min. Loud biphasic (expiratory and inspiratory) wheezing can be heard, and pulsus paradoxus is often present (20-40 mm Hg). Oxyhemoglobin saturation with room air is less than 91%. As the severity increases, the patient increasingly assumes a hunched-over sitting position with the hands supporting the torso, termed the "tripod position."
For more on the presentation of a severe asthma episode, read here.
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Cite this: Zab Mosenifar. Fast Five Quiz: Test Your Knowledge of Severe Asthma - Medscape - May 18, 2020.