We need to be aware of minute ventilation at the extremes because it can cause catastrophic problems in the peri- and postintubation period. Failure to ventilate enough, for instance, failure to maintain respiratory alkalosis in salicylate poisoning (should emergent dialysis not be available prior to intubation), causes worsening of acidosis and has been linked to sudden death. I know of several cases in severe diabetic ketoacidosis where induction and muscle relaxation precipitated death. In hindsight, I think the combination of severe fluid depletion and acute worsening of an already severe acidosis triggered these events. Maintaining a high minute ventilation may have helped the situation.
Explore This IssueACEP Now: Vol 34 – No 01– January 2015
Conversely, when extreme low minute ventilation is present, operators must be hypervigilant not to create auto-PEEP by breath stacking, which can lead to cardiovascular collapse or barotrauma, resulting in pneumothorax. COPD and asthma patients have as much as a 10 times greater risk of life-threatening hypotension with emergent intubation compared to other ED patients. This results from intubation and over-bagging in a patient with an impaired ability to expel air from the lungs. More volume goes in with each breath than comes out. Hyperinflation of the lungs increases intrathoracic pressure, collapsing the heart, and decreases venous return, leading to hypotension. If not recognized quickly, pulseless electrical activity arrest ensues. The first clue will be a falling pulse oximetry reading, which might be erroneously believed to be a tube problem or barotrauma. In COPD patients (all of whom are at risk of pneumonia), operators also frequently misinterpret postintubation hypotension as a consequence of sepsis instead of auto-PEEP.
Postintubation hypotension should immediately prompt concern for auto-PEEP in COPD and asthma. High plateau pressures will alarm on the vent, and high pressures are felt through the bag, but this may be dismissed as a marker of disease severity. Auto-PEEP is easily corrected by disconnecting the tube from the bag (or vent) and pressing on the chest (pushing air out and suspending ventilation for 30–60 seconds); blood pressure and pulse oximetry will improve quickly.
My goal with every intubation is to avoid a catastrophic event in the peri-intubation and immediate postintubation period. I obsess about oxygenation…I try to avoid regurgitation and emesis.
My goal with every intubation is to avoid a catastrophic event in the peri-intubation and immediate postintubation period. I obsess about oxygenation: preoxygenation with nasal cannulas and face mask or CPAP in the very ill, upright preoxygenation, and NO-DESAT nasal oxygen during all intubations. I try to avoid regurgitation and emesis by avoiding high-pressure face mask ventilation in a flat position, and always positioning the head higher than the stomach (ear-to-sternal notch, or tilting the cervical-spine patient feet down). I decompress the bowel obstructed and massive gastrointestinal bleeders before intubation.