Gas Exchange & Oxygenation

Upper airway components and primary function

Composed of the pharynx (throat) and larynx (voice box) ;

responsible for warming air, filtering foreign particles , and humidifying air.

Cardiopulmonary Function

how well the heart and lungs work together to deliver oxygen to the body and remove carbon dioxide.

pharynx subdivisions

-nasopharynx

-oropharynx

-laryngopharynx or hypopharynx

Larynx (voice box)

Structure located at the top of the trachea that houses the vocal cords.

Lower airway structures

Includes the trachea, bronchi, bronchioles, and alveoli of the lungs

Alveoli

Structures at the end of the bronchioles where actual gas exchange occurs.

Lobar differences between right and left lungs

Right = three lobes
Left lung = two lobes.


(think same as av valves. tricuspid 3 right, bicuspid 2 left)

Neural control of bronchial diameter

The parasympathetic and sympathetic nervous systems regulate bronchoconstriction and bronchodilation.

Pleural cavity and fluid function

Located within the visceral and parietal pleural membrane layers; produces fluid that allows the lungs to expand and contract smoothly.

bronchi vs bronchioles

Bronchi are larger main airway passages extending from the trachea, while bronchioles are smaller branches leading directly to the alveoli

Mechanics of inhalation

Diaphragm and intercostal muscles contract, expanding the thorax and creating negative pressure inside the lungs to draw air in.

Mechanics of exhalation

Diaphragm and intercostal muscles relax, decreasing thoracic size and expelling gas from the lungs.

Diaphragm

Muscle separating the chest (thoracic) cavity from the abdominal cavity, controlled by the autonomic nervous system, that contracts during inhalation.

Surfactant

Lubricant produced in the lungs that keeps the alveoli from collapsing during exhalation.

Atelectasis

Collapse of alveoli or areas of lung tissue, resulting in reduced lung volume and impaired ventilation. It commonly occurs after surgery due to general anesthesia, opioids, or shallow breathing.

Primary structures involved in gas exchange

Bronchioles and alveoli, which deliver gas to the pulmonary capillaries via diffusion.

Ventilation

The flow of air into and out of the alveoli, transporting oxygen into the lungs and carbon dioxide out.

Perfusion

The flow of blood driven by the cardiopulmonary system into alveolar capillaries to exchange deoxygenated blood for oxygenated blood.

Pulmonary capillaries

Blood vessels located in the walls of the alveoli where diffusion and gas exchange occur.

Role of the brainstem in respiratory regulation

Monitors the body's oxygen demand and carbon dioxide levels, signaling the respiratory system to respond to excesses or undersupplies.

Effect of fever or exercise on respiration

Increases the rate and depth of respirations, causing more carbon dioxide to be exhaled and more oxygen to be inhaled.

Respirations

The number of breaths taken per minute. (12-20 on a normal adult)

Peripheral chemoreceptors location

Located in the aortic arch and carotid arteries; they sense changes in blood $CO_2$ and $O_2$ levels.

Central chemoreceptors location

Located in the medulla oblongata within the brainstem.

Role of chemoreceptors in respiration control

Peripheral chemoreceptors detect changes in blood $CO_2$ and $O_2$, signaling central chemoreceptors to adjust the rate and depth of respirations.

Emphysema

A type of COPD where the alveoli are damaged and lose their elasticity, causing air to become trapped in the lungs and making it difficult to exhale.

• The alveoli walls are damaged/destroyed

• The alveoli become larger, floppy, and less elastic (less recoil)

• Air still enters, but it has trouble getting back out

• This causes air trapping

Lung compliance

The ability of the lungs to expand (stretch) in response to pressure inside the alveoli.

Think:
Higher compliance = lungs expand more easily
Lower compliance = lungs are harder to expand

For example:

• Emphysema → ↑ compliance (lungs are overly stretchy → easy to expand, hard to empty)

• Pulmonary fibrosis → ↓ compliance (lungs are stiff)

Airway resistance

The pressure or opposition of the tissues in the airway to the flow of air.

Inspiratory reserve volume (IRV)

The additional amount of air that can breathed in after a normal inspiration.

Think of it as:

1. Take a normal breath in → this is tidal volume (TV).

2. Keep inhaling beyond that normal breath → that extra air is inspiratory reserve volume (IRV).

3. One full forced deep breath is TV + IRV

Expiratory reserve volume (ERV)

The additional amount of air expelled after a typical normal breath.

Think of it as:

1. Take a normal breath out → this is tidal volume (TV).

2. Keep exhaling beyond that normal breath → that extra air is expiratory reserve volume (ERV).
   
   

3. One forced deep exhale is TV + ERV

Tidal volume

The amount/volume of air inspired or expired with each normal unforced breath.

Residual volume

The amount of air remaining in the alveoli after expiration.

Think of the sequence:

1. Normal breath in → Tidal Volume (TV)

2. Normal breath out → TV

3. Force yourself to exhale MORE → Expiratory Reserve Volume (ERV)

4. After you have exhaled as much as physically possible, air STILL remains → Residual Volume (RV)

So:

• ERV = air you CAN get out after normal exhale

• RV = air you CANNOT get out even after forceful exhale

Forced vital capacity (FVC)

(WHAT ATI SAYS)
The amount of air that can be expelled from the lungs in $1\,s$ during forced expiration.

What it should say:

• Forced Vital Capacity (FVC) → how much air comes out during the entire forced exhalation.

• Forced Expiratory Volume in 1 Second (FEV₁) → how much air comes out during the first 1 second.

Tidal volume (TV) + Expiratory Reserve Volume (ERV) = Forced Vital Capacity (FVC).

Vital capacity (VC)

The maximum amount of air that is expelled after maximal inspiration.

• Maximal inspiration → take the biggest breath possible.

• Then exhale as much as possible.

• The total amount you exhale = Vital Capacity (VC).
  
  Tidal Volume (TV) + Inspiratory Reserve Volume (IRV) + Expiratory Reserve Volume (ERV) = Vital Capacity (VC)

Total lung capacity

The amount of air remaining in the lungs after maximal (forced) inspiration.

Think of it as:

1. Take the biggest breath possible → your lungs are filled with the maximum amount of air.

2. That maximum amount of air in your lungs = Total Lung Capacity (TLC).

3. This includes all the air in your lungs, even the air that cannot be exhaled (Residual Volume RV).

Formula:

Total Lung Capacity (TLC) = Vital Capacity (VC) + Residual Volume (RV)

Myocardial blood flow function

Supplies oxygen and essential nutrients to the heart muscle, enabling proper functioning of both pulmonary and systemic circulation.

Valvular state during diastole

Mitral and tricuspid valves are open to allow ventricular filling from the atria, while aortic and pulmonic valves remain closed.

Valvular state during systole

Mitral and tricuspid valves close, and the aortic and pulmonic valves open to permit blood ejection from the ventricles.

First heart sound ($S_1$)

A sound produced at the onset of systole by the closure of the mitral and tricuspid valves.

Second heart sound ($S_2$)

A sound produced at the end of systole when ventricular pressure drops, causing closure of the aortic and pulmonic valves.

Cardiac murmur cause

A blowing or whooshing sound caused by turbulent backflow of blood through incompetent heart valves.

Cardiac output (CO)

The volume of blood ejected by the left ventricle in one minute, typically ranging from $3$ to $6\,L/min$ in a healthy resting adult.

$CO = HR \times SV$ ,
cardiac output x heart rate = stroke volume.

Stroke volume (SV)

The volume of blood ejected from the left ventricle with each individual contraction or cardiac cycle.

Factors influencing stroke volume

Preload, afterload, and contractility.

Preload (End-Diastolic Volume)

The volume of blood in the left ventricle at the end of diastole, immediately prior to the next contraction.

Frank-Starling mechanism

The physiological principle stating that increased ventricular stretching from higher end-diastolic volume produces a stronger contraction and greater stroke volume.

Afterload

The amount of resistance or force the left ventricle must overcome to eject blood into circulation during contraction.

Front: What is the effect of athletic training on cardiac output?

Athletes develop an increased resting Stroke Volume (SV). This allows them to maintain a normal resting Cardiac Output (CO) with a lower resting Heart Rate (HR).

During exercise, athletes can achieve a much higher maximal Cardiac Output (CO).

Stroke volume seen in athletes

xtreme athletes can have a cardiac output of up to 35 L/min during exercise.

Cardiac Conduction Electrical Pathway

the electrical signal traveling through the heart responsible for the normal sinus rhythm—the expected heart rhythm for adults

1. SA node (pacemaker) → starts the electrical impulse

2. AV node → briefly delays the impulse

3. Bundle of His → carries the impulse into the ventricles

4. Right & left bundle branches → carry it down the septum

5. Purkinje fibers → spread the impulse through the ventricles → ventricles contract

Ambient room air oxygen fraction

Contains $21\%$ oxygen.

Target oxygen saturation ($SpO_2$) ranges

$95\%$ to $100\%$ for healthy individuals, and $88\%$ to $92\%$ for clients with specific respiratory illnesses.

Complications of unhumidified nasal cannula therapy

Drying of nasal mucous membranes and skin breakdown from friction and mucosal dryness.

Clinical benefits of humidified oxygen

Prevents mucosal desiccation and keeps respiratory secretions moist, making them easier for the client to expectorate.

WHO $SpO_2$ threshold for pediatric oxygen delivery

Oxygen delivery is recommended when $SpO_2 < 90\%$ in children displaying signs of respiratory distress.

Target $SpO_2$ range per American Heart Association AHA pediatric guidelines

Oxygen should be administered and titrated to achieve an $SpO_2$ between $94\%$ and $99\%$.

Preferred oxygen delivery method for infants with moderate to severe bronchiolitis

High-flow nasal cannula (HFNC) therapy, which is safer and more effective than low-flow nasal cannula therapy.

Recommendation on low-flow oxygen humidification in pediatric care

The use of heated or unheated humidification with low-flow oxygen delivery is not supported

Gastric distension in oxygen delivery

The swelling of the stomach with air or gas when supplemental oxygen or artificial ventilation is forced into the body, which can compress the diaphragm, impair lung expansion, and decrease ventilation and oxygenation.

Standard nasal cannula advantages and disadvantages

Advantages: Safe, simple, inexpensive, comfortable, decreases claustrophobia risk, allows eating and drinking, avoids rebreathing $CO_2$, and delivers $24\%$ to $44\%$ oxygen at lower flow rates ($1$ to $6\,L/min$).

Disadvantages: Causes dermatitis and nasal irritation, causes headaches and dry mucous membranes at flows above $4\,L/min$, unsuitable for nasal obstructions (polyps, mucosal edema), and delivers less accurate oxygen percentage dependent on respiratory pattern.

High-flow nasal cannula (HFNC) advantages and disadvantages

Advantages: Simple to use, provides good humidification, carries minimal risk of gastric distention, and may help avoid intubation.

Disadvantages: More expensive than low-flow nasal cannula and requires a specialized flowmeter.

Simple face mask advantages and disadvantages

Advantages: Inexpensive and usable on mouth breathers.

Disadvantages: May cause claustrophobia, interferes with eating/drinking (critical in neonates, infants, and children), requires monitoring for nausea or vomiting, and retains $CO_2$ (not recommended for clients at risk for $CO_2$ retention).
and requires regular skin care during long-term use due to risk of skin breakdown.

Simple face mask flow rate and oxygen concentration

Delivers a medium concentration of 35%35% to 60%60% oxygen at a flow rate of 55 to 10 L/min10L/min.

Partial and nonrebreather masks advantages and disadvantages

Advantages: Recommended for short-term use in acute illness and trauma, delivering high oxygen concentrations ($60\%$ to $90\%$) at flow rates of $10$ to $15\,L/min$ for clients with hypoxia.

Disadvantages: Cannot be used with humidification, requires a good facial seal, requires high flow rates to keep reservoir bag inflated, and carries risks of atelectasis and oxygen toxicity.

Venturi mask advantages and disadvantages

Advantages: Provides precise oxygen concentration independent of client breathing factors or flow rate, uses exchangeable Venturi barrels to deliver various concentrations, and reduces rebreathing of exhaled air.

Disadvantages: Can be noisy, can feel claustrophobic, and interferes with eating and drinking.