Robert Moorman

Low-flow endobronchial insufflation with air for 2 hours of apnea provides ventilation adequate for survival.

We tested the efficacy of low-flow endobronchial insufflation (EI) with air, as it may be useful in emergency situations in which positive-pressure mechanical ventilation is not possible. The only equipment required is a source of compressed air with flow controller and a specially designed insufflation catheter. The insufflation catheter has forked ends that can be positioned blindly in the mainstem bronchi. In six anesthetized, apneic dogs averaging 9.6 kg, we determined that the average air flow needed to maintain PaO2 above 45 mm Hg and PaCO2 below 65 mm Hg after 30 min was 2.5 L/min. At these flow rates, all dogs survived 2 h of endobronchial insufflation with no neurologic dysfunction. The small internal diameters (0.8 mm) of the catheter ends increase gas exit velocity and allow for adequate oxygenation and CO2 removal at low flow rates. Endobronchial insufflation could also be employed with cricothyroidotomy and a compressor for emergency situations in the field involving mass casualties, where oxygen supplies and equipment are limited.

Collateral ventilation of obstructed lung during high-frequency oscillation in dogs and pigs

To determine if collateral ventilation (CV) occurs in pigs and dogs during intermittent positive-pressure ventilation (IPPV) and high-frequency oscillation (HFO), seven pigs and seven dogs were studied by measuring Xenon 133 washout (XeW) from an occluded subsegmental bronchus. The rate constant/min (K) for Xe blood uptake (KXeb) was derived, and when subtracted from K for XeW (KXeW) gave K for removal of Xe by CV (KXecv). Pig XeW were single exponentials with mean KXew = 0.25/min during IPPV and 0.12/min with HFO. In pigs, mean K of XeW was no different from KXeb so that all XeW occurred by blood uptake and none by CV. XeW in dogs had two exponentials. Dogs had over 11 times greater mean KXeW than pigs during IPPV and over 24 times greater during HFO. In dogs, on average, 79% (IPPV) and 87% (HFO) of XeW occurred by CV. CV is a means of gas exchange during HFO and IPPV in dogs but not in pigs.