Hypoxemia-Respiratory Distress

Initial stuff

  • sick/not sick → work of breathing? (accessory muscles, tripoding) will tire it will get worse, are they protecting their airway, responsive (unless 2 <80 wil max NPPV) vs unresponsive (Lethargic, obtunded, vomiting.) ? → if unresponsive need intubation → icu? (code status)

  • position/sit pt up/apply Oxygenation → then DDX

  • how Hypoxemia (saturation)? if too low jump in to bipap, Sign of problems with oxygen delivery? (AMS, lactate, chest pain, cyanosis)?

  • vitals and I/O and last labs?

  • look at chart Hx (HF,stroke,delerium,COPD,PNA) main issue of admission, talk to RN about event, recent interventions, medalist (resp depresion, AC), transfusion or fluid? last CXR/CT/Echo

  • physical exam (HF, wheezing, crackles, DVT) — not most useful → POCUS (PTX,Aline-N/Bline-fluid,effusion,systolic fxn,DVT)

DDX

Alveolar

  • Pulm edema (HF exac, falsh pulm edema (tachyarrythmia, ACS, HTN-E,TACO,TRALI)) (crackles,JVD,Edema,on IVFs/blood,)

  • Aspiration Pneumonitis (fast) /PNA (hr-days) (chocking,Vomiting evidence)

  • Effusion

Airway

  • COPD/Astma exac

  • anaphylaxis

  • angioedema

  • mucus plugging.

Other

  • absent lung sound → PTX (truma), Atelectasis, large effusion (Hf,Cirrhosis, empeima (fever,WBC))

  • PE (no CXR finding, Normal exam, tachy)

DX

  • ABG (pulse Ox not always accurate) PaO2/PCo2, trend

  • CC panel (lactate,)

  • CBC

  • BMP

  • trop

  • CXR

  • EKG

  • echo if HF exac pr Flash

TX

  • call RT

  • sit upright, suction

  • O2 > 90 → NC → non-rebreather → HFNC → NIPP → intubate

  • pulmonary edema (volume overload, HF) → stop IVF/blood → 80 IV Lasix → CPAP (normo-/hypocapnic PaCO₂ ≤45) or BiPAP hypercapnic (PaCO₂ >45, acidosis)

  • flash pulmonary edema → nitro

  • aspiration pneumonitis/PNA → HFNC (caution CPAP/BiPAP), start Abx if (≥2/3: fever/WBC/purulent sputum + new infiltrate)

  • cardiogenic pulmonary edema – High-dose NTG: If SBP <160 → 800 mcg IV over 2–3 min, repeat q3–5 min (total 2–3 mg). If SBP ≥160 → 1–2 mg IV over 3–5 min, repeat q3–5 min ×2–3 doses. Then start infusion 100–400 mcg/min targeting SBP ↓20–30%.

  • wheezing → Duoneb nebulizer

  • absent lung sounds → PTX, atelectasis, large effusion (C-tube if large PTX and only NC-NRB; HFNC and NIPPV are contraindicated). For atelectasis (x-ray one side white out and trachea shift toward → CPT, frequent suctioning, breathing treatment, pulm). Effusion (x-ray one side white out and trachea shift away → think effusion [Lasix], empyema [tube + Abx], PTX [tube])

  • PE (CTA, US, AC)

  • NPO until stable

Note:

  • [[hypoxemia]] low O2 in blood (pulse ox, blood gas)

  • hypoxia: low O2 at the level of cells and tissue

  • oxygen content: saturation + Hgb level

  • oxygen delivery: oxygen content × CO → how much is pumped to tissue

  • pulse ox: measures what saturation of Hgb is

  • blood gas: measures amount of dissolved O2 → PaO2

  • not protecting airway: not responsive to stimuli, can see vomit or nosebleed and they are gurgling, frequent suctioning

  • pulse ox is a time machine; it will take 30 seconds to change

  • in V/Q mismatch, when part of lung is not getting as much ventilation, a lot of O2 should correct it; when part of the lung is getting no ventilation like in shunt, then O2 won’t fix it

  • A-a difference from blood gas (alveolar O2 − arterial O2) – MedCalc – normal (5–10, 20 in older) means low inspired O2 or alveolar hypoventilation; rest of issues have higher A-a gradient (3,4,5,6); don’t need it for everyone unless can’t find why

  • NC – 1–6 L/min, 3% additional FiO2 per L, up to like 45% (O2 100% plus environment 21%)

  • venti mask (no bag on it) – blowing 10 L/min around FiO2 like 45–50% (O2 100% plus environment 21%)

  • non-rebreather mask, has bag on it, bag inflated, less from environment, FiO2?

  • HFNC (heated), can choose FiO2 and flow rate 10–60 L/min, up to 100% FiO2; if can’t tolerate NIPP mask or high risk for aspiration; use max flow rate and FiO2 in rapid situations

  • NIPP – (different interfaces), continuous (CPAP) or non-continuous (BiPAP) positive pressure; CPAP keeps airway open and improves oxygenation like in OSA, keeps trachea open; BiPAP in HF with fluid in alveoli (popping when opening/closing), positive pressure keeps alveoli open and improves gas exchange and helps blow out CO2 (like if work of breathing is high); two pressures are set: EPAP and IPAP triggered by each breath (can max FiO2 to 100%)

  • not protecting airway is absolute contraindication for NIPP (if vomit will aspirate); they need to be awake and not in restraints for NIPP, or RT needs to be there with them

  • BiPAP → if hypercapnia, COPD, OHS; 10 cm H2O good start for EPAP and IPAP 5 cm H2O above EPAP, around 15

  • CPAP → if hypoxia without hypercapnia, like in respiratory distress and increased work of breathing; 10 cm H2O good CPAP value

  • volume overload → HF or NIPP; if awake NIPP (HF, COPD while meds work)

  • position is important; sit the patient up

  • ABG analyzing → if blood doesn’t come out quickly might be mixed; put the right cap on to take the air out; if frothy that is worthless; look at all the numbers including methemoglobin and carboxyhemoglobin

Framework (not realistic in RRT)

  1. Low inspired O2 (on mountain) – normal A-a

  2. Alveolar hypoventilation: both hypoxemia and hypercarbia, central (opioid, OHS, brainstem stroke, paralysis) or peripheral (airflow obstruction) – normal A-a

  3. V/Q mismatch: (atelectasis, ) better with O2

  4. Shunt – not better with O2

  5. Diffusion limitation (rare at rest) → alveolar-capillary thickness. When CO is elevated and blood is moving fast, RBCs don’t have time to get oxygen; usually fibrosis and edema; they desaturate with movement, not at rest

  6. Low mixed venous O2 (tissue taking most O2, can’t re-oxygenate fully), like severe anemia, low CO – body takes most of the oxygen

If you'd like, I can also make this into a clean printable ICU one-page reference sheet.