Respiratory management

What is the difference between ventilation and respiration?

Ventilation is the movement of air in and out of the lungs; respiration is gas exchange (Movement of O2 and CO2 at a cell level)

What structures make up the thorax?

Thoracic cage, pleural space, muscles of ventilation, Lungs, mediastinum

how many lobes does each lung have?

Rt has 3 (upper, lower, middle) Lt has 2

contents of the mediastinum

• heart

• great vessels

• lymphatics

• esophagus

What is the difference between the visceral and parietal pleura?

Visceral pleura covers the lungs, parietal pleura lines the chest wall and mediastinum

what is the main muscle of inhalation

the diaphragm

Is inhalation or exhalation the active process?

Inhalation is an active process; exhalation is passive

what is the main contribution of the upper airway to ventilation?

conditioning air; warming, humidifying and cleansing it

What prevents the trachea from collapsing

16-20 C-shaped cartilage rings

Why does aspiration most often go to the Rt lower lobe?

the right mainstream bronchus is wider and angles only 20-30 degree from midline

What is the function of the conducting airways?

warm and humidify air, protect gas exchange areas and carry air in and out. No ACTUAL gas exchange

where does gas exchange take place?

the respiratory airways: respiratory bronchioles and alveoli (acini)

What do type I alveolar cells do?

they make up approximately 90% of the alveolar surface and maintain the gas-blood barrier; easily injured

Two functions of type II alveolar cells?

Produce, store, and secrete surfactant and divide to repair the alveolar wall after injury

What is the downside of collateral air passages?

they allow microorganisms to move through the lung tissue

where does pulmonary circulation begin and end

pulmonary artery from the right heart; returns to the left heart via pulmonary veins

what does the bronchial circulation supply

• lung tissue itself

• tracheobronchial tree

• visceral pleura

• connective tissue

• lymph nodes

• nerves

why is arterial saturation less than 100% on room air

bronchial venous blood drains into the left atrium (anatomic shunt) lowering it to 96-99%w

hy do lungs stay inflated?

Intrapleural pressure is always less than intrapulmonary pressure

why is intrapleural pressure negative

the parietal pleura is pulled outward by the chest wall and the visceral pleura inward by lung fibers

what is tidal volume

air inhaled and exhaled with each normal breath

What is inspiratory capacity?

tidal volume plus inspiratory reserve volume

what is vital capacity

Inspiratory Reserve volume+ Tidal volume + Expiratory Reserve Volume

What is residual volume

air left in the lungs after complete exhalation

What is functional residual capacity

residual volume plus expiratory reserve volume

What is total lung capacity

the sum of all four lung volumes

what three parts regulate ventilation

• Controller (CNS)

• Effectors (muscles of ventilation)

• Sensors (chemoreceptors and mechanoreceptors)

What is normal V/Q ratio?

0.8 (4L/Min ventilation to 5L/min perfusion)

what is alveolar dead space?

an alveolus that is ventilated but not perfused

what is intrapulmonary shunting

an alveolus that is perfused but not ventilated so blood isn’t oxygenated

Is a V/Q greater than 0.8 dead space or shunt producing

Dead space producing

Is a V/Q less than 0.8 dead space or shunt producing?

Shunt producing

what does a significant V/Q mismatch cause

hypoxemia

which part of the lung gets the most ventilation and perfusion?

the gravity-dependent areas (bases when upright, posterior supine)

how much more ventilation do the bases get than the apex when upright

approx 4 times more

Where is Zone 1 of the lung

the non-dependent apex, with the potential for no perfusion

Where is Zone 3 of the lung

the gravity-dependent area with constant blood flow

How should a patient with diffuse lung disease be positioned?

Right lung down, because it is larger and more vascular

what is acute lung failure

failure of the pulmonary system to maintain adequate gas exchange

most common type of organ failure in the ICU

acute lung failure (about 56% of patients)

what is the usual cause of acute lung failure

secondary to another disorder affecting the pulmonary system (COPD, pneumonia)

What is type I acute lung failure

hypoxemic normocapnic; low paO2, normal PaCO2

What is type II acute lung failure

hypodermic hypercapnia; low PaO2, PaCO2

What PaO2 indicated acute lung failure

<60mmHg

What PaCO2 indicated hypercapnia

>45 mmHg

What are the three main causes of impaired gas exchange in acute lung failure?

• alveolar hypoventialtion

• V/Q mismatch

• intrapulmonary shunting

what causes V/Q mismatching in acute lung failure

alveoli that are partially collapsed or partially filled with fluid

What is the best way to diagnose and follow acute lung failure

ABG analysis

What SaO2 is the usual target in acute lung failure

Greater than 90%

what can progressive intrapulmonary shunting lead to?

Impaired tissue perfusion, lactic acidosis and multiple organ dysfunction

when oxygen is ineffective in hunting what is added to the treatment?

PEEP to open alveoli

how is respiratory acidosis corrected in acute lung failure?

by adequately oxygenating and ventilating the patient

what is the goal of nutrition support in acute lung failure

to meet nutritional needs while avoiding overfeeding

what HOB elevation decreases aspiration risk?

30-45 degrees