Hoffman A M, Kupcinskas R L, Paradis M R
Department of Medicine, School of Veterinary Medicine, Tufts University, North Grafton, MA 01536, USA.
Am J Vet Res. 1997 Dec;58(12):1463-7.
To compare the efficacy of positive pressure ventilation applied through a mask versus an endotracheal tube, using anesthetized/paralyzed foals as a model for foals with hypoventilation.
Six 1-month-old foals.
A crossover design was used to compare the physiologic response of foals to 2 ventilatory techniques, noninvasive mask mechanical ventilation (NIMV) versus endotracheal mechanical ventilation (ETMV), during a single period of anesthesia and paralysis. Arterial pH, PaO2, PaCO2, oxygen saturation, end-tidal CO2 tension, airway pressures, total respiratory system resistance, resistance across the upper airways (proximal to the midtracheal region), and positive end-expiratory pressures (PEEP) were measured. Only tidal volume (VT; 10, 12.5, and 15 ml/kg of body weight) or PEEP (7 cm of H2O) varied.
Compared with ETMV, use of NIMV at equivalent VT resulted in PaCO2 and pH values that were significantly higher, but PaO2 was only slightly lower. Between the 2 methods, peak airway pressure was similar, but peak expiratory flow was significantly lower and total respiratory resistance higher at each VT for NIMV. Delivery of PEEP (7 cm of H2O) was slightly better for ETMV (7.1 +/- 1.3 cm of H2O) than for NIMV (5.6 +/- 0.6 cm of H2O).
These data suggest that use of NIMV induces similar physiologic effects as ETMV, but the nasal cavities and mask contribute greater dead space, manifesting in hypercapnia. Increasing the VT used on a per kilogram of body weight basis, or the use of pressure-cycled ventilation might reduce hypercapnia during NIMV.
Use of NIMV might be applicable in selected foals, such as those with hypoventilation and minimal changes in lung compliance, during weaning from endotracheal mechanical ventilation, or for short-term ventilation in weak foals.
以麻醉/麻痹的幼驹作为通气不足幼驹的模型，比较经面罩与经气管插管进行正压通气的效果。
6匹1月龄幼驹。
采用交叉设计，在单个麻醉和麻痹期内比较幼驹对两种通气技术的生理反应，即无创面罩机械通气（NIMV）与气管内机械通气（ETMV）。测量动脉pH值、动脉血氧分压（PaO₂）、动脉血二氧化碳分压（PaCO₂）、血氧饱和度、呼气末二氧化碳分压、气道压力、总呼吸系统阻力、上呼吸道（气管中段近端）阻力以及呼气末正压（PEEP）。仅潮气量（VT；10、12.5和15 ml/kg体重）或PEEP（7 cmH₂O）有所变化。
与ETMV相比，在相同VT下使用NIMV时，PaCO₂和pH值显著更高，但PaO₂仅略低。两种方法之间，气道峰值压力相似，但在每个VT下，NIMV的呼气峰值流速显著更低，总呼吸阻力更高。ETMV（7.1±1.3 cmH₂O）输送PEEP（7 cmH₂O）的效果略优于NIMV（5.6±0.6 cmH₂O）。
这些数据表明，使用NIMV诱导的生理效应与ETMV相似，但鼻腔和面罩产生的死腔更大，表现为高碳酸血症。按每千克体重增加使用的VT或采用压力控制通气可能会减少NIMV期间的高碳酸血症。
NIMV的使用可能适用于特定的幼驹，例如那些在从气管内机械通气断奶期间通气不足且肺顺应性变化最小的幼驹，或用于体弱幼驹的短期通气。
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