Effects of mechanical ventilation with expiratory negative airway pressure on porcine pulmonary and systemic circulation: mechano-physiology and potential application

Abstract

We studied the impact of mechanically regulated, expiratory negative airway pressure (ENAP) ventilation on pulmonary and systemic circulation including its mechanisms and potential applications. Microminipigs weighing about 10 kg were anesthetized (n = 5). First, hemodynamic variables were evaluated without and with ENAP to approximately −16 cmH2O. ENAP significantly increased heart rate and cardiac output, but decreased right atrial, pulmonary arterial and pulmonary capillary wedge pressures. Second, the evaluation was repeated following pharmacological adrenergic blockade, modestly blunting ENAP effects. Third, fluvoxamine (10 mg/kg) was intravenously administered to intentionally induce cardiovascular collapse in the presence of adrenergic blockade. ENAP was started when systolic pressure was < 40 mmHg in the animals assigned to ENAP treatment-group. Fluvoxamine induced cardiovascular collapse within 4 out of 5 animals. ENAP increased systolic pressure to > 50 mmHg (n = 2): both animals fully recovered without neurological deficit, whereas without ENAP both animals died of cardiac arrest (n = 2). ENAP may become an innovative treatment for drug-induced cardiovascular collapse.

Analysis of cardiohemodynamic and electrophysiological effects of morphine along with its toxicokinetic profile using the halothane-anesthetized dogs

“…However, in the first experiment the high dose markedly decreased the systolic aortic blood pressure to <40 mmHg at 1.9 min after the start of infusion without showing marked electrocardiographic abnormality including ST-T morphological changes. To assist circulation of the animal, mechanically-regulated, expiratory negative airway pressure (ENAP) ventilation was started at 3 min, which has been shown to be efficacious for treating drug-induced cardiohemodynamic collapse (Hagiwara-Nagasawa et al, 2021;Goto et al, 2022). For this animal, the drug administration was continued thereafter and finished at 10 min as originally planned.…”

Magnitude of mitral valve closure plays a pivotal role in enhancing the forward blood flow during cardiac massage in dogs with ventricular fibrillation

“…The highest peak aortic pressure in other dogs was higher than 40 mmHg during both ACD-CM (44.5-91.8 mmHg) and S-CM (41.5-80.2 mmHg). Peak aortic pressure higher than 40 mmHg is considered critical for successful CPR [5,10]. The highest peak aortic pressure in these dogs was higher than the peak pulmonary capillary wedge pressure by 18.0±7.6 mmHg during ACD-CM, whereas the highest peak aortic pressure was lower than the highest peak pulmonary capillary wedge pressure by 8.1±7.8 mmHg during S-CM.…”