Mechanical Ventilation Flashcards by Corinne Perra

How does anesthesia affect ventilation?

Respiratory depression -> alter sensitivity to CO2

Relaxes respiratory muscles

Atelectasis develops

Impairs V/Q matching -> inhibits hypoxic pulmonary vasoconstriction

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How can ventilation status affect anesthesia?

Uptake of inhalational anesthetics depending of ventilation

Controlled ventilation facilitates reliable uptake and smooth plane of anesthesia

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How is ventilation monitored?

Arterial blood gas (PaCO2)

Capnograph

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What values define oxygenation? How is it measured?

PaO2 or SpO2

Arterial blood gas or pulse oximetry

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When breathing 100% O2, can oxygenation be improved more by ventilation?

Nope

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How is resistance calculated?

Pressure difference/flow

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How is compliance calculated?

Volume/pressure

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__________ limits flow

Resistance

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_____________ limits volume

Compliance

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What are the stages of the respiratory cycle?

Inspiration

inspiration flow
inspiratory pause

Expiration

expiratory flow
expiratory pause

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What is mechanical ventilation?

Artificial ventilation where mechanical means are used to assist/replace spontaneous breathing

Can be provided by ventilator or person

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What is spontaneous ventilation?

Patient determines when and how

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What is assisted ventilation?

Patient determines when and ventilator determines how

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What is mandatory ventilation

Ventilator determines when and how

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What is IPPV?

Intermittent positive pressure ventilation

-> positive pressure is maintained ONLY during inspiration

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What is IMV?

Intermittent mandatory ventilation

Operator sets a predetermined number of positive breaths but patient can also breath freely between mechanical breaths

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What is the highest pressure during inspiration called?

Peak inspiratory pressure (PIP)

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What can occur at the PIP?

Pressure will inflate alveoli, opens atelectasis, or cause barotrauma

What is the PEEP?

Positive end expiratory pressure

-positive pressure that is maintained during expiration (keeps alveoli open)

What are indications for PEEP?

Open throax
Lung parenchymal disease
Following alveolar recruitment maneuver (ARM)

For intubated patients that breathing 100% O2 the main indication to ventilate is to ??

Decrease PaCO2

For patients that breathe air what are the indications for mechanical ventilation?

Hypoxemia
Decrease PaCO2
Decrease work of breathing

What are side effects of mechanical ventilation?

Hypotension (esp in hypovolemic patients)

What is the treatment of hypotension caused by MV?

Volume loading
Switch off ventilator
Decrease airway pressure
Inotropic drugs

What are the direct effects of hypercapnia?

Peripheral vasodilation Decreased myocardial contractility Bradycardia Increased ICP

What are the indirect effects of hypercapnia?

Duct to catecholamine release - tachycardia - increased myocardial contractility - increased BP

What is the respiratory rate for healthy lungs?

10-15 breath/min

Tidal volume of healthy lungs ?

10-15 ml/kg

When ventilating, PIP should be how much if BW <10kgs?

10 cmH2O

When ventilating, PIP should be how much if BW > 10kg?

20 cmH20

What should PEEP be when ventilating healthy lungs?

0-2 cmH2O

How is ventilation performed?

Close pop-off Squeeze reservoir bag to desired pressure Release bag so patient can passively expire Open pop-off Repeat 10times/min

What is the volume control ventilation mode?

Device sets tidal volume, pressure is a deepest variable If compliance is decreased —> pressure would increase Difficult to control tidal vol in small patients

What is pressure controlled ventilation mode?

Device sets the airway pressure -> tidal volume is dependent variable Resistance increase ->volume decreases Works regardless of body size

When is a volume controlled MV indicated?

When there are transpulmonary pressure changes

When is pressure controlled ventilation MV indicated?

When lung volume changes (eg thoracic surgery)

How do pneumatic ventilators work?

Consist of compressible bellows in a container Pressurized drive gas in cylinder can compress bellows causing inspiration When pressure is released, expiration happens spontaneously An automatic pop-off valve in ventilator is controlled by the drive gas pressure

What is er variable for a pressure mode MV?

Negative pressure generative by patients breath ->> tiggers assisted breath

What is the trigger variable for a flow controlled MV?

Inspiratory flow generated by patients breath

What is a limit variable for MV?

Stops inspiration when value is reached | Eg volume or pressure limit

What are common causes of patient-ventilator asynchrony during anesthesia ?

Inadequate anesthetic depth Inadequate lung volume or tidal volume

How are normal healthy patients weaned from the ventilator after anesthesia?

Decrease ventilator setting and cause hypercapnia to stimulate breathing Or continue ventilating until fully awake

What is cyclic recruitment?

Alveoli open and collapse with each breath (purposed mechanism of ventilator induced lung injury )

How do you ventilate an atelectasis lung?

Requires a recruitment maneuver Increase alveolar minute ventilation —> removes more CO2