The first arterial blood gas for an asthma patient in the emergency department reveals: pH 7.49; PaCO2 30; PaO2 82; SaO2 95%; HCO3? 24 on a nasal cannula 3 L/min

The patient's peak expiratory flow rate was 165 L/min, respiratory rate was 16 breaths/min, and pulse 106 beats/min. After continuous aerosolized albuterol over the past hour, the patient's cur-rent ABG results are as follows: pH 7.34; PaCO2 45; PaO2 49; SaO2 79%; HCO3? 25 on a high flow nasal cannula 15 L/min. The patient's peak expiratory flow rate is 95 L/min, respiratory rate 35 breaths/min, pulse 128 beats/min, and the patient is diaphoretic. The respiratory therapist should suggest which of the following at this time?
a. Change to a nonrebreather mask.
b. Begin continuous positive airway pressure.
c. Intubate and initiate mechanical ventila-tion.
d. Initiate noninvasive positive pressure ven-tilation.

ANS: C
This patient's airway obstruction is worsening as evidenced by the deterioration in the patient's acid-base status, oxygenation status, and peak expiratory flow rate. The patient has also devel-oped tachycardia, tachypnea, and sweating. The critical values are partial pressure of oxygen in the arteries (PaO2), peak expiratory flow rate (PEFR), respiratory rate (RR), and pulse. This pa-tient is now in impending ventilatory failure and meets the standard criteria for instituting me-chanical ventilation (see Box 4-5). Changing oxygen delivery devices to a nonrebreather mask will not increase the fractional inspired oxygen (FIO2) delivered. Continuous positive airway pressure may address the patient's oxygenation problem; however, it will not help to improve the patient's increased work of breathing.