Mechanical Ventilation

Question 1

Mechanical Ventilation

Answer 1

The use of a machine or device to assist or replace ventilation

Ventilation = movement of air in & out of the lungs
Vs
Respiration = movement of gases across a membrane
ie. alveoli & capillaries

Question 2

Types of Ventilation

(2)

Answer 2

Negative Pressure (LOW)
- Inspiration drives negative pressure
- INC space in thoracic cavity = INC lung capacity (expanded) = pressure inside the lungs is now lower than the atmosphere
- EXPIRATION = high pressure in the lungs > wants to go out in the atmosphere

Positive Pressure:
- Air is getting forced in (compared to being sucked in)
- ie blowing up a balloon
Indication: mm of inspiration are insufficient

Question 3

Administration of Mechanical Ventilation

(2)

Answer 3

Invasive (intubation): passage of artifical airway into trachea
1. Endotracheal tube (ETT) - mouth/nose
2. Tracheostomy - incision into trachea (anterior neck) to get tube in

Non-invasive:
- Nasal mask
- Complete face mask

Question 4

Indications for MV

(4 - 6 + 4)

Answer 4

Severe hypoventilation, hypoxia, or hypoxemia
- Apnea - not breathing
- Acute hypercarbia (that is not quickly reversible) = elevated CO2 in blood
- PaO2 < 50 mmHg w/ supplemental O2
- Repiratory rate > 30 breaths/min (tachypenic)
- Vital capacity less than 10 L/min
- Inspiratory force <-25 cm H2O

Central Depression
- Decreased level of consciousness
- Anesthesia or deation
- Head injury
- Drug overdose

Decrease work of breathing & respiratory mm fatigue

Poor pulmonary hygiene (secretion clearance) - NOT effective of clearing airways

Question 5

Complications

(5)

Answer 5

1. Barotrauma: excessive pressure
   Can lead to pneumothorax
   WORSE complication
2. Volutrauma: excessive volume
   Alveolar overdistension
3. Ventilator Acquired Pneumonia (VAP)
   Micro-aspiration of gastric contents or oral secretions
4. Diaphragm atrophy: as a rsult of disuse
   Is not being used - mechanical ventilation is doing all the work
5. Hemodynamic compromise: flow of blood
   Overinflated lungs > compression of great vessels > DEC venous return > DEC cardiac output = less blood going out to the system

Question 6

Types of Mechanical Ventilation Breaths

(3)

Answer 6

Mandatory: Completely dependent
- Ventilation is initiated, controlled, and ended by the ventilator

Assisted
- Ventilation initiated by the patient but controlled & ended by the ventilator
- Ex. Bench press spotter - initated by the presser BUT struggles at the end & spotter steps in to help

Spontaneous
- Ventilation is initiated, controlled, and ended by the patient BUT the volume & pressure of the breath delivered by the ventilatory is based on patient demand

Question 7

Modes of Ventilation

(3)

Answer 7

Invasive
- Continuous Mandatory Ventilation (CMV)
- Assist Control ventilation (ACV)
- Syncronized Intermittent Mandatory Ventiliation (SIMV)

Non-Invasive
- Continuous Positive Airway Pressure (CPAP)

Continuous Mandatory Ventilation (CMV)
- Tidal volume & preset respiratory rate delivered by ventilator
- Ventilator provides total support (patient has no control) completely sedated ex. Sx or high level SCI

Question 8

Assist Control Ventilation (ACV)

3

Answer 8

Tidial volume & minimum number of mandatory breaths per minute (respiratory rate) delivered by the ventilator. This will deliver a minimum minute ventilation
- Minute ventilation = amount of air moving in/out per min > product of TV x RR

Patient able to initiate inspiration but sitll receives preset tidial volume
- If pt cannot make an adequate respiratory effort

If patient foes not initiate a breath within a specific time period, the ventilatory will deliver a breath to maintian the respiratory rate (preset)

Disadvantage:
- Higher RR than what is set by the machine - still receive a full TV = minute ventilation is INC > respiratory alkolosis OR become hyperinflated & distention/rupture of alveoli

Question 9

Synchronized Intermittent Mandatory Ventilation (SIMV)

(3)

Answer 9

1. Preset mandatory tidal volume & respiratory rate delivered by ventilator
2. Patient able to breath spontaneously between ventilator breaths
3. Spontaneous patient-initiated breaths are synchronized w/ ventilator breath
   ** IF the pt initates breath - ventilator will just adjust accordingly - this prevents STACKED breathing

Question 10

Continuous Positive Airway Pressure (CPAP)

(6)

Answer 10

1. Patient spontaneous breaths are augmented w/ a perdetermined level of (positive) pressure delivered throughout the entire respiratory cycle (inspiratory & expiratory phases)
2. Keeps airways open continuously in patients who can breathe spontaneously on their own but require assistance keeping airways unobstructed
3. Commonly used as a weaning mode for those who are intubated or an attempt to postone intubation
4. When used with a mask, it is considered noninvasive ventilation
5. Help prevent alveolar collapse, improve FRC, and enhance oxygenation
6. Used to patients with obstructive sleep apnea, adults with neuromuscular diseases, acute & chronic ventilatory failure & children w/ acute respiratory failure

Question 11

Ventilator Adjustments

(2)

Answer 11

1. Positive End Expiratory Presure (PEEP)
2. Pressure Support Ventilation (PSV)

Question 12

Positive End Expiratory Pressure (PEEP)

4

Answer 12

1. A positive pressure is applied to the lung at the end of the expiratory phase of ventilation
2. Helps keep alveoli open (preventing alveoli collapse) during expiration & reduces pulmonary shunting
   V/Q mismatch - good perfusion but issues w/ ventilation
3. High levels of PEEP can cause excessive alveolar distension (volutrauma) or pulmonary barotrauma (ie pneunothorax = worse complication)
4. Complications of PEEP may include:
   - INC physiological dead space
   Excess air (opposite of shunting) - inhaled a lot of air not participating in gas exchange
   - DEC CO
   - Ventilator-Associated Pneumonia (VAP)
   - Increased risk of barotrauma

Question 13

Pressure Support Ventilation (PSV)

(3)

Answer 13

1. Patient-initiated breaths are augmented by the ventilator to maintain a constant preset inspiratory pressure
2. Patient initiates all breath & controls the respiratory rate & inspiratory time
3. Helps to decrease work od breathing - INSPIRATION aspect

Augmented breath for assistance
No safety net in place for this type

Question 14

Communication

(2)

Answer 14

1. Decreased ability to communicate verbally when intubated or wearing mask
2. Alternative methods of communication:
   - Writing
   - Hand signals - common phrases ESP. yes/no - use close-end questions
   - Communication boards - point at pictures to explain what they want

Question 15

Weaning

(2)

Answer 15

1. The process of decreasing mechanical ventilation - ventilator INDEPENDENT
2. A spontaneous breathing trial while being closely monitored is typically performed to assess readiness to behin weaning process