L10: mechanical ventilation

what is IPPV?

airway pressure is maintained above atmospheric pressure during inspiration and then falls to

atmospheric pressure, allowing for passive expiration

what does IPPV stand for?

intermittent positive pressure ventilation

manual ventilation

closing the APL valve and squeezing the bag

spontaneous ventilation

the movement of gas in and out of the lungs produced by the individual using the diaphragm and intercostal muscles

describe inspiration

thoracic cavity volume increases → alveolar pressure decreases below atmospheric pressure → air flows into lungs

describe expiration

thoracic volume decreases → alveolar presssure increases above atmospheric pressure → air forced out

what are the clinical indications for IPPV?

1. inability to ventilate

2. decreased ventilatory drive

describe IPVV in anesthesia

1. limited period of time

2. used on healthy lungs

3. controlled ventilatory modes

describe IPPV in ICU

1. long term use

2. underlying disease that impairs ventilation

3. assisted ventilatory modes

when performing manual IPPV in a small animal, what value do you need to make sure the pressure does not go over?

10-20 cmH20

when performing manual IPVV in a small animal, how long do you squeeze the bag for?

no longer than 1 second

how to perform manual positive pressure ventilation in small animals?

1. close APL valve

2. squeeze reservoir bag for 1 sec

3. watch the pressure gauge

4. watch chest inflation

5. open the APL valve

what is tidal volume?

amount of air moved in and out of the lungs with each respiratory cycle

what is peak inspiratory pressure (PIP)?

the highest pressure measured during the respiratory cycle

what is inspiratory to expiratory ratio (I:E)?

ratio of the duration of inspiratory and expiratory phases

what is positive end expiratory pressure (PEEP)?

positive pressure that the ventilator maintains within the breathing system after the end of each expiratory phase between breaths

atelectasis

alveoli tend to close under anesthesia leading to hypoxemia and hypercapnia

what are the functions of PEEP?

1. keep alveoli open to prevent atelectasis

2. minimize damage to the lung during ventilation

what do high PEEP values mean?

collapse of capillaries in the lung → reduced cardiac output

In small animals, what value will we set PIP on the mechanical ventilator in a closed chest animal?

10-15 cmH20

what will we set the tidal volume on the mechanical ventilator in a small animal?

10-15 mL/kg

what will we set the PEEP value on the mechanical ventilator on a small animal?

0-4 cmH20

what will we set the respiratory rate on the mechanical ventilator in a small animal?

10-20 breaths/min

what will we set the PIP on the mechanical ventilator in a large animal?

less than 20 cmH20

what will we set the respiratory rate on the mechanical ventilator for large animals?

6-8 breaths/min

what will we set the tidal volume on the mechanical ventilator for a large animal?

10 mL/kg

what is the I:E ratio on the mechanical ventilator for both small and large animals?

1:2

what do we set the PEEP value on the mechanical ventilator in large animals?

0-4 cmH20

what are the types of Bellow ventilators referred to based on?

how the bellow is moved during expiration

ascending bellow

bellow moves upward during expiratory phase of breathing cycle

which bellow system is it easy to detect system leaks or disconnection?

ascending (standing) bellow

descending (hanging) bellow

bellow will descend towards the bottom during expiration

which bellow collects humidity within the bellow, adding weight to the system?

descending bellow

what type of bellow is shown?

descending bellow

what type of bellow is shown?

ascending bellow

what 4 mechanisms contribute to lung injury associated with mechanical ventilation?

1. volutrauma

2. barotrauma

3. atelectrauma

4. biotrauma

volutrauma

Excessive stretch from high tidal volumes

barotrauma

Pressure-related injury that generates overdistension of the alveoli

atelectrauma

high force exerted on alveoli → triggers a local inflammatory response→ alveolar-capillary membrane injured

biotrauma

Biological response that promotes injury even in lung areas not subjected to mechanical stress and in extrapulmonary organs

what is the consequence of IPPV on the cardiovascular system?

decrease in venous return and preload leading to hypotension

what worsens venous return when an animal is on IPPV?

1. low inspiratory times

2. high PIP

3. PEEP