NU263 Unit 3 Ventilated Severe Asthma Workup Example

Breaths Stacked on Breaths: A Respiratory Failure Workup Pairing Each Gas With the Ventilator Setting That Produced It for a Composite 28-Year-Old Woman Intubated for Severe Asthma, From Trapped Air and a Falling Pressure to a Slower Rate and an Accepted Carbon Dioxide

[Student Name]

Purdue University Global

NU263: Medical-Surgical Nursing III

Unit 3 Respiratory Failure Workup

[Instructor Name]

[Date]

The patient is composite; values and settings are bracketed where illustrative, and ventilator settings are ordered by the provider and managed with the respiratory therapist.

The Patient

[Ms. T.], composite, 28, with asthma since childhood, two prior admissions, none intubated. After three days of a cold she became severely breathless. In the emergency department she received repeated inhaled bronchodilators, IV steroids and magnesium, but tired, and her carbon dioxide rose. She was intubated at [0200].

Two Columns Read Together

Gas 1, at [0300]. Settings: volume control, tidal volume [450] mL, rate [20], PEEP [5]. Gas: pH [7.15], carbon dioxide [78] mm Hg, oxygen [88] mm Hg on [50] percent oxygen. Pressures: peak [48], plateau [32]. Blood pressure [84/50], down from [128/80] before intubation. Expiratory hold measured trapped air, called auto-PEEP, at [14] cm of water. Gas 2, at [0500], after the changes below. Settings: tidal volume [400] mL, rate [12], higher inspiratory flow so that each breath takes less time and leaves more time to breathe out, PEEP [5]. Gas: pH [7.21], carbon dioxide [70] mm Hg, oxygen [96] mm Hg on [40] percent. Pressures: peak [40], plateau [26]. Auto-PEEP [6]. Blood pressure [112/70].

Why the First Settings Failed

In severe asthma, narrowed airways slow the flow of air out of the lungs. If a new breath starts before the last one has fully left, air is trapped and builds up with every breath, a process called dynamic hyperinflation. The trapped pressure, auto-PEEP, presses on the heart and great veins, reducing the blood returning to the heart, which is why her blood pressure fell after intubation. A rate of [20] gave her too little time to breathe out (Leatherman, 2015).

Each breath the machine gave her arrived before the last one had left; the fix was to give her fewer breaths, not more.

Why a Slower Rate Helped

Lowering the rate and shortening each breath lengthened the time to breathe out. Trapped air fell from [14] to [6], plateau pressure fell below [30] and her blood pressure recovered. Carbon dioxide stayed high, [70], but the pH of [7.21] was accepted. This strategy, called permissive hypercapnia, tolerates a raised carbon dioxide and a moderately low pH to avoid the harm of hyperinflation, provided the patient has no condition, such as a brain injury, that makes high carbon dioxide dangerous (Laher & Buchanan, 2018).

Peak and Plateau Pressures

The peak pressure reflects both airway resistance and lung stiffness; the plateau pressure, measured during a short pause, reflects the pressure in the alveoli. In asthma, a high peak with a lower plateau points to resistance in the airways, which is expected. A rising plateau signals hyperinflation and the risk of lung injury or pneumothorax.

Nursing Watch

1. Blood pressure after any change in settings, and after each suction or bag-ventilation, since fast bagging can worsen trapped air.

2. Signs of pneumothorax: sudden rise in peak pressure, falling saturation, unequal chest movement or breath sounds. Report at once.

3. Sedation as ordered, enough to prevent breathing against the ventilator, with the level assessed and recorded.

4. Bronchodilators and steroids on schedule, coordinated with the respiratory therapist.

5. If the blood pressure suddenly falls with very high trapped air, the team may briefly disconnect the ventilator to let the trapped air escape; nurses should know this maneuver is directed by the provider or respiratory therapist (Harding et al., 2023).

What the Family Needed to Hear

Her mother arrived at [0400], frightened by the number of alarms and by being told her daughter's carbon dioxide was high. The nurse explained in plain words that her daughter's lungs were trapping air, that the machine had been slowed down on purpose to let the air out, and that a high carbon dioxide was being allowed for now because it was safer than forcing more breaths. She was told what would show improvement: fewer alarms, lower pressures and lighter sedation over the next day or two. Families of young adults on ventilators often assume the worst from a single number, and a short explanation of the plan helps them read the room.

Evaluation

By day two, her trapped air was [3], carbon dioxide [52] and pH [7.31] on the same settings, and she was breathing more easily on lighter sedation. She was extubated on day three.

Weaning Signs to Watch

As the airways open, the signs of readiness follow a pattern: trapped air falls toward zero, peak pressure drops, wheeze becomes softer and the patient breathes comfortably on lower sedation. The nurse tracks these together during the morning sedation pause, along with her ability to follow commands, so that the team can judge when she is ready for a breathing trial.

What the Workup Shows

Ventilator numbers mean little without the settings beside them. A carbon dioxide of [70] looks alarming on its own; beside a rate of [12], a plateau of [26] and trapped air of [6], it is the sign of a safer plan.

References

Harding, M. M., Kwong, J., Hagler, D., & Reinisch, C. (2023). Lewis's medical-surgical nursing: Assessment and management of clinical problems (12th ed.). Elsevier.

Laher, A. E., & Buchanan, S. K. (2018). Mechanically ventilating the severe asthmatic. Journal of Intensive Care Medicine, 33(9), 491-501. https://doi.org/10.1177/0885066617740079

Leatherman, J. (2015). Mechanical ventilation for severe asthma. Chest, 147(6), 1671-1680. https://doi.org/10.1378/chest.14-1733