Influence Of Positive Pressure Ventilation Research Articles

Alternative ventilation strategies in cardiopulmonary resuscitation.

The introduction of the 2000 Guidelines for Cardiopulmonary Resuscitation emphasizes a new, evidence-based approach to the science of ventilation during cardiopulmonary resuscitation (CPR). New laboratory and clinical science underemphasizes the role of ventilation immediately after a dysrhythmic cardiac arrest (arrest primarily resulting from a cardiovascular event, such as ventricular defibrillation or asystole). However, the classic airway patency, breathing, and circulation (ABC) CPR sequence remains a fundamental factor for the immediate survival and neurologic outcome of patients after asphyxial cardiac arrest (cardiac arrest primarily resulting from respiratory arrest). The hidden danger of ventilation of the unprotected airway during cardiac arrest either by mouth-to-mouth or by mask can be minimized by applying ventilation techniques that decrease stomach gas insufflation. This goal can be achieved by decreasing peak inspiratory flow rate, increasing inspiratory time, and decreasing tidal volume to approximately 5 to 7 mL/kg, if oxygen is available. Laboratory and clinical evidence recently supported the important role of alternative airway devices to mask ventilation and endotracheal intubation in the chain of survival. In particular, the laryngeal mask airway and esophageal Combitube proved to be effective alternatives in providing oxygenation and ventilation to the patient in cardiac arrest in the prehospital arena in North America. Prompt recognition of supraglottic obstruction of the airway is fundamental for the management of patients in cardiac arrest when ventilation and oxygenation cannot be provided by conventional methods. "Minimally invasive" cricothyroidotomy devices are now available for the professional health care provider who is not proficient or comfortable with performing an emergency surgical tracheotomy or cricothyroidotomy. Finally, a recent device that affects the relative influence of positive pressure ventilation on the hemodynamics during cardiac arrest has been introduced, the inspiratory impedance threshold valve, with the goal of maximizing coronary and cerebral perfusion while performing CPR. Although the role of this alternative ventilatory methodology in CPR is rapidly being established, we cannot overemphasize the need for proper training to minimize complications and maximize the efficacy of these new devices.

Pulmonary blood flow regulation: Influence of positive pressure ventilation

Positive pressure ventilation with PEEP has been reported to reduce hypoxic pulmonary vasoconstriction (HPV) and thus increase venous admixture. This effect was investigated in six chronically instrumented unanesthetized healthy sheep. The change in left pulmonary arterial blood flow (Q̇lpa, ultrasonic transit time) in response to unilateral lung hypoxia (10 min of N 2 alternately to the left (LLH) and right lung (RLH)) was evaluated during mechanical ventilation with and without PEEP of 10 cm H 2O in comparison to spontaneous breathing. In the spontaneously breathing animal and during mechanical ventilation without PEEP, Q̇lpa decreased during LLH from 30% to 16% of cardiac index, during RLH it increased to 51%. With 10 cm H 2O of PEEP, Q̇lpa showed an identical reaction to hypoxia both in the left and right lung. It is concluded that mechanical ventilation and PEEP up to 10 cm H 2O does not interfere with pulmonary blood flow regulation to hypoxia.

The Influence of Positive-Pressure Ventilation on Cardiovascular Function in the Critically Ill

In this review, the various interactions between heart and lung that occur during positive-pressure ventilation are contrasted with spontaneous ventilation. Based on this analysis, appropriate ventilator management directed at optimizing oxygen delivery to the tissues can be employed in the treatment of the critically ill.

Pulmonary vein flow pattern in man during thoracotomy.

Pulmonary vein flow (PVF) pattern was traced with an electromagnetic flowmeter in 10 patients with normal hearts undergoing operations for pulmonary diseases. Instantaneous pulmonary artery flow, ECG, pulmonary artery pressure and left atrial pressure were recorded simultaneously. The pulsatile flow patterns obtained ocrresponded well to those previously found in dogs, and were remarkably similar to caval flow pattern. A constant and inverse relationship between the contour of the right atrial pressure andthe PVF pattern was found. In 3 patients, PVF was reversed by atrial systole; otherwise the flow was forward throughout the cardiac cycle. The influence of positive pressure ventilation was small, consisting of a slight initial inspiratory increase followed by a decrease during the latter half of inspiration.