BCRT: British Columbia Respiratory Therapy

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The routine management of mechanical ventilation in the ICU includes monitoring of peak airway pressures, plateau pressures and determining airway resistance.
When volume or pressure is pushed through an airway, a peak pressure is generated. This peak pressure is the sum of the amount of pressure necessary to get through the airways, inflate the alveoli and displace the chest wall and diaphragm. An inspiratory hold is performed on the ventilator to measure how much this pressure (plateau pressure) is actually being sensed in the alveoli once the lungs are inflated. By subtracting the plateau pressure from the peak pressure, we can calculate the resistance from the airways.
In managing mechanical ventilation, we routinely look at the plateau pressure to determine the limits to which we can increase our ventilating volumes. For the majority of patients, the chest wall and diaphragm are relatively compliant so are not a major factor in ability to ventilate patients. In cases of stiff chest wall or distended abdomens, the plateau pressure may be misleading as the pressure sensed within the alveoli is in part due to the pressures from the stiff chest wall or diaphragm.
Recently, esophageal catheters have been used to help optimize ventilation of patients with concerns re. stiff chest walls or diaphragms (distended abdomens). A catheter inserted in the esophagus is in close proximity to the pleural space. Esophageal pressures can be used as a surrogate to pleural pressures. Use of esophageal pressure monitoring can then help to differentiate between:

o pressure in the pleural space, attributable to chest wall and diaphragm and
o pressure distending the lungs (transpulmonary pressure) which might result in barotrauma

Ptpt (transpulmonary) = Paw (plateau) – Pes (esophageal)

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New Ventilation Modes

•Dual Control

Within-a-breath switches from PC to VC during the breath

• VAPS and pressure augmentation

Breath-to-Breath

– Pressure-Limited, Flow-Cycled Ventilation

• Volume support ventilation VSV Siemens 300

• Variable-pressure-support Cardiopulmonary

corporation Venturi,

– Pressure-Limited, Time-Cycled Ventilation

• Pressure-regulated volume-control PRVC Siemens 300

• Adaptive pressure ventilation APV Hamilton Galileo

• Auto-flow Draeger Evita 4

• Volume-control Puritan Bennett 840

• Variable pressure control Cardiopulmonary

corporation Venturi

•Proportional-Assist Ventilation

•Adaptive Support Ventilation

•Automatic Tube Compensation

•Airway Pressure-Release Ventilation

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1.1 To ensure ventilation and management of a status asthmaticus patient is initiated and maintained according to standard.

Definitions:

• Permissive hypercapnia or controlled hypoventilation:

A strategy for management of patients requiring mechanical ventilation whereby priority is given to the prevention or limitation of severe pulmonary hyperinflation over the maintenance of normal alveolar ventilation.  This involves allowing arterial CO₂ to be as high as 90mmHg, with no particular emphasis on acidosis correction.

• Effective tidal volume (VTeff):

The exhaled tidal volume minus volume lost to tubing compliance.

• Minimum alveolar concentration (MAC):

The concentration of an agent in alveolar gas necessary to prevent reflex movement in 50% of patients when a standard surgical incision is made.

• VILI:

Ventilator induced lung injury.

• Heliox:

A colorless, odourless, and tasteless inert gas.  It has a lower density and Reynold’s number than Nitrogen, the normal balance gas in air.  The lower Reynold’s number allows it to remain in a state of laminar flow even in very small airways, where air normally tends to switch to turbulent flow.  The laminar flow pattern improves alveolar emptying, and ventilation.

• Isoflurane:

A volatile agent that is used for general anesthesia but has been shown to dilate the airway through B-adrenergic receptor stimulation.  It has minimal cardiovascular side effects however it can decrease systemic vascular resistance and may cause cerebral vasodilation, with increases in ICP seen in concentrations of > 1.1%.

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Status Asthmaticus Ventilation and Management 2.3.4-51

Medical News Today News Article: ”

Clearance Received By Covidien For Its Puritan Bennett 840 Ventilator System

08 Aug 2009

Covidien (NYSE: COV), a leading global healthcare products company and recognized innovator in mechanical ventilation and respiratory care devices, announced it has received 510(k) clearance from the U.S. Food and Drug Administration (FDA) to market its Leak Compensation software feature for the Puritan Bennett 840™ ventilator system. This option provides continuous levels of mechanical ventilation to patients requiring respiratory support, regardless of the level of gas leakage that might occur in the circuit or past a patient interface device in the clinical setting.

During either invasive or noninvasive ventilation, air leaks past a mask, nasal prongs, nasal pillow, supraglottic airway, endotracheal tube or tracheostomy tube can result in loss of gas volume, potentially causing subsequent dysynchrony between a patient’s spontaneous breathing efforts and the ventilator’s response.

The ”

(Via Medical News Today News Article

.)