Acta anaesthesiologica Scandinavica. Supplementum
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Acta Anaesthesiol Scand Suppl · Jan 1977
Physiologic evaluation of the HFPPV pneumatic valve principle and PEEP. An experimental study.
In experiments in dogs the ventilatory and circulatory conditions prevailing with the ventilatory pattern in high-frequency positive-pressure ventilation (HFPPV) were investigated with use of a pneumatic valve principle and a ventilator system of an "open" character. Keeping the gas input constant the importance of insufflation frequency and insufflation time and the reactions to various levels of positive end-expiratory pressure (PEEP) were investigated in terms of changes in arterial pH, Pco2 and Po2. ⋯ Including the associated effects on cardiac output and venous admixture, the cardio-pulmonary and circulatory parameters studied did not show any substantial changes with PEEP levels below 7.5--10 cm H2O. Thus the level of PEEP, which often is part of the ventilatory pattern in HFPPV, does not seem to have any untoward influence on the circulation (stroke volume, cardiac output, total peripheral vascular resistance) and oxygen transport (arterial oxygen content and oxygen flux) in normovolaemic dogs.
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Acta Anaesthesiol Scand Suppl · Jan 1977
Clinical TrialClinical evaluation of high-frequency positive-pressure ventilation (HFPPV) in laryngoscoy under general anaesthesia.
A technique for automatic ventilation during laryngoscopy under general anaesthesia was evaluated in a lung model and in 5 patients (3--57 y) submitted for routine laryngoscopy. this technique has been given the name laryngoscopic HFPPV and utilizes an insufflation frequency (f) of 60 per min and a relative insufflation time (t%) of 22%. Ventilation is given via a nasotracheal insufflation catheter. Laryngoscopic HFPPV permits laryngeal surgery with a virtually unobstructed surgical field under complete muscular relaxation. ⋯ A simple ventilation nomogram for clinical use is proposed. Adequately used, this nomogram guarantees safe ventilation during laryngoscopic HFPPV. An Fio2 of 0.3--0.4 gives adequate arterial oxygenation.
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Acta Anaesthesiol Scand Suppl · Jan 1977
Phrenic and vagal nerve activities during spontaneous respiration and positive-pressure ventilation.
Afferent vagal nerve activity from stretch-receptors in the lung and efferent phrenic nerve activity were recorded during spontaneous respiration and during positive-pressure ventilation with three different types of ventilators. During spontaneous respiration the efferent phrenic nerve activity slightly preceded the afferent vagal nerve activity. Volume-controlled ventilation did not alter the phrenic nerve activity when the ventilation was set at a rate equal to that during spontaneous respiration, but afferent vagal volleys increased in duration. ⋯ High-frequency positive-pressure ventilation (HFPPV) gave rise to basal, non-grouped activity in vagal afferents, causing inhibition of inspiration. During HFPPV, spontaneous respiration can take place on activation of other afferents to the respiratory centre. Clinical aspects of respirator treatment from a neurophysiological standpoint are discussed.