Chapter 31: Ventilation and Failed Airway

IBSC domain: Airway Management
Estimated study time: 140–190 minutes
Difficulty: Advanced
Clinical review: July 2026

Educational use only. Follow local protocols, device instructions, scope of practice, transport policy, and medical direction.

Learning objectives

After completing this chapter, you should be able to:

1. Select pregnancy-aware oxygenation and ventilation goals after intubation.
2. Choose initial ventilator settings using predicted body weight and disease physiology.
3. Explain why a PaCO₂ that appears normal for a nonpregnant adult may represent relative hypoventilation in pregnancy.
4. Recognize ventilator dyssynchrony, auto-PEEP, high airway pressure, disconnection, tube obstruction, and pneumothorax.
5. Apply lung-protective ventilation to pulmonary edema and acute respiratory distress syndrome.
6. Modify ventilation for severe asthma and other obstructive disease.
7. Distinguish failed intubation from failed oxygenation and rapidly transition to rescue ventilation.
8. Prepare a transport ventilator, oxygen supply, manual backup, sedation, and failed-airway plan for the entire mission.

Opening transport scenario

A 34-week patient with severe preeclampsia and pulmonary edema is intubated before transfer. Initial settings are assist-control volume ventilation, tidal volume 500 mL, respiratory rate 10/min, PEEP 5 cm H₂O, and FiO₂ 1.0. Her height is 157 cm. Peak pressure rises to 42 cm H₂O, plateau pressure is 31 cm H₂O, SpO₂ is 92%, and EtCO₂ is 45 mm Hg. Fetal monitoring shows recurrent late decelerations.

The team must address several problems at once: the tidal volume may be excessive for predicted body weight, the carbon dioxide is high relative to normal pregnancy, oxygenation is inadequate, and the high plateau pressure suggests reduced respiratory-system compliance. The solution is not simply to increase every ventilator setting. The team must identify the mechanism, protect the lungs, preserve maternal hemodynamics, and reassess fetal response after maternal correction.

1. Pregnancy-aware ventilation goals

Oxygenation

Maternal oxygenation is fetal resuscitation. Use enough FiO₂ and PEEP to maintain adequate maternal oxygenation while avoiding unnecessary prolonged hyperoxia. A commonly used obstetric target is SpO₂ at least 95% when fetal oxygen delivery is a concern, but the target must be individualized to disease, baseline status, and local guidance.

Carbon dioxide and pH

Normal pregnancy increases minute ventilation and commonly lowers PaCO₂ into the high 20s to low 30s mm Hg. Therefore:

• PaCO₂ near 40 mm Hg can represent relative hypoventilation.
• Severe respiratory acidosis threatens maternal and fetal physiology.
• Deliberate profound hypocapnia can reduce uterine blood flow and cerebral perfusion.
• A transport target should consider pH, hemodynamics, intracranial pathology, obstructive disease, and lung-protective constraints rather than pursuing one rigid number.

Hemodynamics

Positive-pressure ventilation can reduce venous return and cardiac output. This matters in hemorrhage, sepsis, right-heart failure, pulmonary embolism, and aortocaval compression. Correct maternal position, assess preload and pump function, and use mechanism-directed blood, fluid, or vasopressor support.

2. Initial ventilator strategy

Tidal volume

Use predicted body weight, not actual pregnancy weight, to select tidal volume. A common initial range is approximately 6–8 mL/kg predicted body weight when lungs are not severely injured. In acute respiratory distress syndrome, lower tidal volumes near 6 mL/kg—and sometimes lower—may be required to limit plateau pressure.

Respiratory rate

Set the rate to support appropriate minute ventilation, then reassess EtCO₂, arterial or venous blood gas, pH, and auto-PEEP. Increasing rate can worsen air trapping in obstructive disease.

PEEP

PEEP can recruit alveoli and improve oxygenation, but excessive PEEP can reduce venous return, worsen hypotension, overdistend compliant lung regions, and increase right-ventricular afterload. Titrate to oxygenation, compliance, blood pressure, and disease mechanism.

FiO₂

Use high FiO₂ during immediate stabilization, then titrate once oxygenation is reliable. If oxygenation remains inadequate despite high FiO₂, investigate tube position, secretions, atelectasis, edema, pneumothorax, embolism, equipment malfunction, and need for additional PEEP or advanced rescue.

Pressure monitoring

• Peak inspiratory pressure reflects resistance plus compliance.
• Plateau pressure estimates alveolar pressure during an inspiratory hold and is strongly influenced by compliance.
• High peak with relatively normal plateau suggests increased resistance.
• High peak and high plateau suggest reduced compliance or excessive tidal volume.
• In ARDS, keep plateau pressure at or below approximately 30 cm H₂O when feasible.

3. Disease-specific patterns

Pulmonary edema and ARDS

Use lung-protective tidal volume, appropriate PEEP, conservative pressure limits, and treatment of the underlying cause. Severe preeclampsia may combine hydrostatic edema, endothelial dysfunction, fluid exposure, and cardiac impairment. Avoid reflexive large crystalloid boluses when the patient is already congested.

Severe asthma and obstructive disease

Priorities include adequate expiratory time, lower respiratory rate, high inspiratory flow, and avoidance of excessive tidal volume. Accepting a higher PaCO₂ may be safer than causing dangerous dynamic hyperinflation, but pregnancy, pH, and fetal status must be considered. Sudden hypotension after ventilation may reflect auto-PEEP; briefly disconnecting the circuit while providing other resuscitation can confirm and relieve severe air trapping.

Pulmonary embolism and right-heart strain

Avoid unnecessary high mean airway pressure. Excessive PEEP can increase pulmonary vascular resistance and worsen right-ventricular output. Oxygenate, support perfusion, and expedite definitive therapy.

Metabolic acidosis

A patient with diabetic ketoacidosis or sepsis may require very high minute ventilation before intubation. Immediately matching that compensatory ventilation after induction is critical; abrupt reduction can cause rapid acidemia and cardiovascular collapse.

4. Ventilator troubleshooting: use a disciplined sequence

When a ventilated patient deteriorates, disconnect from the ventilator and manually ventilate when necessary to separate patient problems from machine problems. A useful memory aid is DOPES:

5. Dyssynchrony, sedation, and neuromuscular blockade

Dyssynchrony can increase oxygen consumption, airway pressure, and risk of self-inflicted lung injury. Address pain, anxiety, inadequate flow, trigger sensitivity, mode mismatch, bronchospasm, and tube discomfort. Ensure continuous analgesia and sedation after RSI. Neuromuscular blockade may be appropriate in selected severe ARDS or impossible-to-control dyssynchrony, but it never substitutes for analgesia and sedation.

6. Failed intubation versus failed oxygenation

Failed intubation means the tube was not successfully placed. Failed oxygenation means the team cannot maintain adequate oxygenation using available noninvasive or supraglottic methods. The second is immediately life-threatening.

If the first attempt fails but oxygenation is adequate

1. Stop and announce the failed attempt.
2. Reoxygenate using two-person mask ventilation or a supraglottic airway.
3. Optimize position, suction, device, operator, bougie/stylet, and cricoid pressure.
4. Do not repeat the same failed technique without a meaningful change.
5. Decide whether waking the patient, continuing with a supraglottic airway, or another intubation attempt is safest.

Rescue oxygenation

• Use an oral airway and two-person bag-mask technique.
• Apply PEEP when appropriate.
• Insert a second-generation supraglottic airway early.
• Confirm ventilation with continuous waveform capnography.
• Release cricoid pressure if it interferes with mask or supraglottic ventilation.
• Suction aggressively when regurgitation or secretions are present.

Cannot intubate, cannot oxygenate

Declare the emergency early. Continue best possible oxygenation while preparing emergency front-of-neck access according to protocol and training. Do not persist with repeated laryngoscopy while saturation and perfusion collapse.

7. Transport ventilator and airway readiness

Before movement, verify:

• Tube depth, cuff pressure, bilateral sounds, and continuous waveform capnography
• Ventilator mode, rate, tidal volume or pressure, PEEP, FiO₂, alarms, and patient synchrony
• Oxygen duration for the planned route plus delay and diversion reserve
• Battery duration and external-power plan
• Tested BVM, PEEP valve, suction, oral airway, and backup oxygen source
• Supraglottic airway and emergency airway kit
• Adequate analgesia, sedation, vasopressor, and infusion volume
• Accessible circuit and tube during loading and movement
• A predefined stop-the-vehicle and diversion threshold

Manual ventilation during failure

Manual ventilation is a diagnostic and rescue skill, not merely a backup device. Use a manometer or careful observation when possible, avoid excessive rate and tidal volume, allow full exhalation in obstruction, and reassess capnography and compliance.

8. Evolving case study

Phase 1: Reassessment

The team recalculates predicted body weight and reduces tidal volume. PEEP is increased cautiously, respiratory rate is adjusted, and a repeat blood gas is obtained. Plateau pressure falls below 30 cm H₂O and oxygenation improves.

Phase 2: Sudden deterioration

During loading, SpO₂ falls, capnography disappears, and the ventilator alarms for low exhaled volume. The team stops movement, disconnects the ventilator, and manually ventilates. The bag is easy to compress, but no capnography is present. Tube depth has changed. The tube is treated as displaced and replaced with immediate waveform confirmation.

Phase 3: Transport

Continuous sedation, blood-pressure support, and maternal positioning are maintained. Fetal late decelerations improve after maternal oxygenation and perfusion are restored.

9. High-yield chapter summary

1. Use predicted body weight for tidal-volume selection.
2. Protect maternal oxygenation while avoiding unnecessary prolonged hyperoxia.
3. Interpret PaCO₂ in the context of normal pregnancy and pH.
4. High peak pressure alone suggests resistance; high peak plus high plateau suggests reduced compliance or excessive volume.
5. ARDS requires lung-protective ventilation and pressure limitation.
6. Obstruction requires long expiratory time and vigilance for auto-PEEP.
7. Use DOPES for sudden deterioration.
8. Failed intubation is not the same as failed oxygenation.
9. Supraglottic airway placement is a key rescue technique.
10. Maintain a tested manual-ventilation and oxygen backup throughout transport.

References

1. International Board of Specialty Certification. Maternal Fetal Transport Microcredential Candidate Handbook. Updated April 2026.
2. Obstetric Anaesthetists’ Association and Difficult Airway Society. Guidelines for the Management of Difficult and Failed Tracheal Intubation in Obstetrics. 2015.
3. Difficult Airway Society. Management of Unanticipated Difficult Tracheal Intubation in Adults. 2025.
4. American Society of Anesthesiologists. Practice Guidelines for Management of the Difficult Airway. 2022.
5. American Thoracic Society, European Society of Intensive Care Medicine, and Society of Critical Care Medicine. Mechanical Ventilation in Adult Patients with Acute Respiratory Distress Syndrome. 2017.