Clinical judgment: when the data disagree

Treat the patient the monitor is describing — if it is describing them

A pulse oximeter needs pulsatile flow. In hypotension, hypothermia, vasopressor use, or motion, the number degrades before the patient does. Correlate the plethysmograph waveform with the palpated pulse before you escalate oxygen for a saturation you do not believe.

Conversely, do not talk yourself out of a real finding. If the patient is mottled, cool, and confused while the numbers look tolerable, the numbers are the thing that is late.

End-tidal CO2 is a perfusion monitor too

A sudden drop in end-tidal CO2 with an unchanged ventilator means less CO2 is arriving at the lung: falling cardiac output, or pulmonary embolism. During CPR, a rise in end-tidal CO2 is the earliest sign of return of spontaneous circulation.

Two different questions

Readiness to wean asks whether the lungs can do the work: adequate oxygenation on modest support, resolving cause, hemodynamic stability, and an awake, cooperative patient. Readiness to extubate asks a separate question — whether the patient can protect and maintain the airway once the tube is gone.

A patient can pass a spontaneous breathing trial beautifully and still fail extubation on secretions, a weak cough, or airway edema. The cuff leak test and the strength of the cough matter as much as the gas.

Reading the trial honestly

The rapid shallow breathing index is rate divided by tidal volume in liters; under about 105 predicts success. But the index is a screen, not a verdict — a patient trending upward through the trial with rising rate and falling volumes is failing in front of you regardless of where the number started.

Name the endpoint first

Before a bronchodilator, decide what should change and by when: less wheeze, better air movement, a measurable rise in peak flow, a slower rate. If you cannot name the endpoint, you cannot tell whether the therapy worked, and you will keep delivering it out of habit.

Reassessment after therapy is the most commonly missed step both on the exam and on the unit. It is also the step that turns you from someone who performs treatments into someone who manages patients.