Basics of Mechanical Ventilation

Mechanical Ventilation:  Respiratory failure is caused by failure to oxygenate (Type I respiratory failure), with resultant decreae in PO2 or failure to ventilate (Type II respiratory failure), with a resultant increase in PCO2.     Breathing Pattern consists of a Control variable, Breath sequence and a targeting scheme.    Ventilator can control only one variable at a time.     Equation of Motion: … Read more

Intubation and Airway Management

Airway Management:  Emergency airway management is associated with a high complication rate. Evaluating the patient prior to airway management is important to identify patients with increased risk of failed airways. Induction agents are often required, but most induction agents are associated with hypotension during emergency intubation. Use of muscle relaxants is controversial for emergency intubation, … Read more

Capnography

Capnography:    Capnogram is a plot of PCO2 vs. time or volume.     Physiology:  In expired respiratory gases, capnography directly reflects the elimination of CO2 by the lungs to the anesthesia device. Indirectly, it reflects the production of CO2 by tissues and the circulatory transport of CO2 from tissues to the lungs. Thus capnography is an important non-invasive technique that provides information … Read more

Proportional Assist Ventilation

 Proportional Assist Ventilation    PAV is a spontaneous breathing mode that offers assistance to the patient in proportion to the patient’s effort. It can be considered as adaptive pressure support. In pressure support, the support is a fixed driving pressure. In PAV, the support is adaptive to keep work of breathing constant.  In this mode, the magnitude of ventilator … Read more

APRV

Airway Pressure Release Ventilation    Airway pressure release ventilation (APRV) mode of mechanical ventilation is an elevated CPAP level with timed pressure releases. This short release for brief periods along with spontaneous breathing promotes CO2 elimination. Release time is short enough to prevent peak expiratory flow from returning to a zero baseline.  The other advantage of … Read more