Vents/ards

What does ventilation refer to?

Movement of air in and out of the lungs, not gas exchange or oxygenation.

Primary parameter to assess ventilation?

$PaCO_2$ .

Effect of low $CO_2$ on cerebral vessels?

Causes vasoconstriction, may reduce ICP. and vasoconstriction

Risk of excessive hyperventilation?

Cerebral edema/ vasocontriction

What is respiration?

Exchange of $O_2$ and $CO_2$ at the alveolar level.

What determines oxygenation?

Molecular $O_2$ absorption; influenced by $FiO_2$, Hgb, and diffusion barriers.

Indications for mechanical ventilation?

Respiratory failure, fatigue, refractory hypoxia, ↑ WOB, neuromuscular weakness, trauma, need for PEEP.

Main function of HFNC?

Provides heated, humidified $O_2$ with mild PEEP and dead-space washout.

Typical starting flow and max tolerated flow?

Start 30–40 L/min, titrate up to 60 L/min.

Starting $FiO_2$ and $SpO_2$ goal?- all

Start 100%, titrate to maintain $SpO_2$ > 90–92%.

Best clinical use for HFNC?

Hypoxemic respiratory failure (pneumonia, COVID-19).

When to avoid HFNC?

Severe hypercapnia or altered mental status.

What does CPAP do?

Provides continuous pressure to keep alveoli open during inspiration and expiration.

What does BiPAP do?

Provides higher inspiratory and lower expiratory pressures to assist ventilation and oxygenation.

Indications for NIPPV?

Dyspnea, RR > 24, hypercapnia, hypoxemia, reversible failure (COPD, asthma, CHF, pneumonia, OSA, CF).

Contraindications for NIPPV?

Coma, arrest, shock, GI bleed, poor airway protection, secretion retention, AMS, anaphylaxis, obstruction.

Initial BiPAP settings for COPD/asthma?

10/5 → 15/8 → 18/8. longer inspitory time Want higher inspiratory pressures

Initial BiPAP settings for CHF?

10/5 → 15/10 → 18/15 (↑ EPAP offloads LV).

Normal tidal volume?

6 cc/kg ideal body weight.

Normal minute ventilation?

6–7 L/min.

How to prevent gastric distention on NIPPV?

Keep peak inspiratory pressure < 25 cm $H_2O$.

When to avoid BiPAP due to aspiration risk?

During active vomiting or GI bleeding.

Mucosal dryness management?

Provide humidification and daily oral care.

Meds to improve NIPPV tolerance?

IV Precedex, Haldol, Ketamine, Fentanyl, Benzos.

Assist-Control (AC) characteristics?

Delivers preset Vt at preset rate; patient-triggered breaths get full Vt.

SIMV characteristics?

Preset Vt + rate; allows spontaneous breaths without mandatory volume.

Ppressure support characteristics?

Provides preset inspiratory assist; patient controls Vt + RR.

Pressure-Control (PCV) characteristics?

Set inspiratory pressure; Vt varies; improves comfort and alveolar filling. Better for vent weaning

Example minute ventilation (0.5 L × 12)?

6 L/min.

Main goal in COPD vent management?

Allow long exhalation to prevent air trapping.

Typical Vt and rate in COPD?

8 mL/kg; RR $\approx$ 10 bpm.

I:E ratio for COPD vent?

1:4 – 1:5.

PEEP setting for COPD?

0 (ZEEP).

Permissive hypercapnia limit?

pH ≥ 7.1 acceptable.

Vent approach for asthma/copd

Same for both: low rate, long expiration, ZEEP, permissive hypercapnia.

Key vent strategy in DKA?

Match or exceed pre-intubation RR to maintain minute ventilation and prevent acidosis.Keep C02 Low (which is acidic), and keep it like that so the Bicarb will continue to raise, making the pH higher.

Why track $EtCO_2$ before intubation in DKA?

Use baseline value to guide post-intubation ventilation.

Common causes of ARDS?

Sepsis, aspiration, pneumonia, trauma, transfusion, overdose.

Berlin diagnostic criteria for ARDS?

Onset ≤ 1 wk, bilateral infiltrates, not cardiac, $PaO_2/FiO_2$ < 300.

Findings suggesting cardiogenic cause?

S3/S4, JVD, Kerley B lines, cardiomegaly, ↑ BNP, abnormal echo.—> not ards

Ventilation strategy for ARDS?

Low Vt (6 mL/kg), PEEP 5, $FiO_2$ 100% → titrate, open-lung approach.

Recruitment maneuver?

Sustained inspiration (~30 s) to reopen alveoli.

Supportive care in ARDS?

Sedation, paralysis, DVT/GI prophylaxis, nutrition, glucose and fluid control.

Effect of prone ventilation?

Improves oxygenation; no mortality benefit; ↑ risk of aspiration and pressure sores.

Inclusion criteria for ARDS protocol?

$PaO_2/FiO_2$ < 300, bilateral infiltrates, no LA HTN.

Starting tidal volume for ARDS?

8 mL/kg → reduce to 6 mL/kg.

Target pH range for ARDS?

7.30–7.45.

If pH < 7.15 in ARDS?

↑ Vt by 1 mL/kg (blow off co2) or give sodium bicarb to off set

If pH > 7.45 in ARDS?

Decrease RR.

I:E ratio goal in ARDS?

Inspiration ≤ expiration duration.