Exam 1: Respiration and Ventilation, Oxygenation and Gas Exchange, Tidal Volume, Table 11-3

Ventilation

The process of air movement into and out of the lungs

Perfusion

The circulation of blood through the lung tissues (alveoli)

Diffusion

The process of gas exchange (carbon dioxide and oxygen)

Inspiration (inhalation)

active process that creates negative pressure

• Diaphragm contracts and moves downward

• Intercostal muscles contract

• Thoracic cavity expands

• Pressure inside lungs decreases

• Air flows into lungs

Expiration (exhalation)

passive process that generates positive pressure

• Diaphragm relaxes

• Thoracic cavity becomes smaller

• Pressure inside lungs increases

• Air leaves lungs

What controls breathing?

The respiratory center is housed in the brainstem, more specifically the medulla oblongata

Crackles (rales)

fine, bubbling sound heard on auscultation of the lung. Produced by air entering the distal airways and alveoli that contain serous secretions.

Rhonchi

abnormal, coarse, rattling respiratory sounds, usually caused by secretions in the bronchial airways.

Stridor

abnormal, high-pitched, musical sound caused by an upper airway obstruction (subglottic).

Wheezing

form of rhonchi, characterized by a high pitched, musical quality. Produced in the lower airways (bronchioles).

Eupnea

normal respirations

Tachypnea

increased (fast) respirations

Bradypnea

decreased (slow) respirations

Apnea

no respirations (not breathing)

Cheyne-Stokes

Pattern:

• Crescendo breathing

• Decrescendo breathing

• Apnea

Seen with:

• Stroke

• Severe head injury

Kussmaul Respirations

Characteristics:

• Deep

• Rapid

• Labored

Seen in:

• Diabetic ketoacidosis

• Metabolic acidosis

Ataxic Respirations

Completely irregular.

Indicates:

• Severe brain injury

Agonal Gasps

Not effective breathing.

Requires:

• Artificial ventilation

• CPR if pulseless

Signs of Inadequate Breathing

• Too fast or too slow

• Dyspnea

• Irregular rhythm

• Apnea

• Shallow respirations

• Reduced airflow

• Unequal chest expansion

• Accessory muscles

• Retractions

• Noisy breath sounds

• Tripod position

Signs of Adequate Breathing

• Normal respiratory rate

• Regular rhythm

• Equal chest rise

• Clear bilateral lung sounds

• Adequate tidal volume

Normal Respiratory Rates (Table 11-3)

Age	Respirations/min
Newborn	30–60
Infant	30–53
Toddler	22–37
Preschool	20–28
School-age	18–25
Adults & adolescents	12–20

Respiratory Arrest

No effective breathing.

May present as:

• Apnea

• Agonal gasps

Requires:

• Immediate ventilation

• CPR if pulseless

Respiratory Failure

Ventilation inadequate.

Results:

• Low oxygen

• High CO₂

Requires immediate intervention.

Respiratory Distress

Patient:

• Working hard to breathe

• Adequate oxygenation may still be present

Signs:

• Accessory muscles

• Tachypnea

• Retractions

• Tripod position

External Factors

• High altitude

• Carbon monoxide

• Toxic gases

• Confined spaces

Internal Factors

• Pneumonia

• Pulmonary edema

• Emphysema

• Pulmonary embolism

Intrinsic Airway Factors

• Tongue obstruction

• Allergic reactions

• Infection

• Swelling

Extrinsic Airway Factors

• Trauma

• Burns

• Foreign body

• Broken jaw

COPD

Patients may develop:

• Chronic high CO₂.

However:
Never withhold oxygen from a patient who needs it.

Regulation of Ventilation

Controlled by:

• Brainstem (medulla and pons)

Chemoreceptors monitor:

• CO₂

• Oxygen

• pH

High CO₂:

• Increases respiratory rate.

Physiology of Breathing

Diaphragm:

• Main muscle of breathing.

Phrenic nerve:

• Controls diaphragm.

Negative pressure:

• Pulls air into lungs.

Alveoli

Site of:

• Oxygen diffusion

• Carbon dioxide removal

Bronchioles

Contain smooth muscle.

Can:

• Constrict

• Dilate

Trachea

• Windpipe

• Supported by C-shaped cartilage

• Divides at the carina

Lower Airway

Includes:

• Trachea

• Main bronchi

• Bronchioles

• Alveoli

Larynx

Contains:

• Vocal cords

• Glottis

• Thyroid cartilage

• Cricoid cartilage

Functions:

• Protects airway

• Produces speech

Oropharynx

Posterior oral cavity.

Epiglottis prevents:

• Aspiration

Nasopharynx

Functions:

• Warms air

• Humidifies air

• Filters contaminants using cilia

Upper Airway

Includes:

• Nose

• Mouth

• Oral cavity

• Pharynx

• Larynx

Dead Space

Air that never reaches alveoli.

Does not participate in gas exchange.

Usually 150 mL in adults

Vital Capacity

Maximum amount of air expelled after deepest possible inhalation.

Minute Alveolar Ventilation

Amount of fresh air reaching alveoli each minute.

Formula:
(Tidal Volume − Dead Space) × Respiratory Rate

Minute Volume

Amount of air moved in one minute.

Formula:
Respiratory Rate × Tidal Volume

Alveolar Ventilation

Amount of air reaching alveoli.

Formula:
Tidal Volume − Dead Space

Residual Volume

Air remaining in lungs after maximal exhalation.

Tidal Volume (TV)

Amount of air moved in one breath.

500 mL average in adults

Reduced Tidal Volume

Means:

• Shallow breathing

Causes:

• Poor ventilation

• Inadequate oxygen delivery

Patients with shallow respirations may need:

• Assisted ventilations

Carbon Monoxide

Carbon monoxide:

• Binds hemoglobin 250 times stronger than oxygen.

Result:

• Oxygen cannot bind.

• Severe hypoxia develops.

Pulse oximeter:

• May still appear normal.

Signs of Hypoxia

Early

• Restlessness

• Anxiety

• Irritability

• Apprehension

• Tachycardia

Late

• Altered mental status

• Weak pulse

• Bradycardia (especially children)

• Cyanosis

Intrapulmonary Shunting

Blood passes alveoli:

• Without receiving oxygen.

Seen with:

• Pulmonary edema

• Pneumonia

• Drowning

V/Q Mismatch

Occurs when:

• Air reaches alveoli but blood does not
  OR

• Blood reaches alveoli but air does not

Causes:

• Pulmonary embolism

• Pneumonia

• Pulmonary edema

• Emphysema

Results:

• Poor oxygenation

• Poor CO₂ removal

Ventilation/Perfusion (V/Q)

Ventilation:

• Air reaches alveoli

Perfusion:

• Blood reaches alveoli

Normal respiration requires both.

Carbon Dioxide Transport

Produced by:

• Cellular metabolism

Transported:

• Back to lungs

Removed:

• During exhalation

Oxygen Transport

Most oxygen:

• Bound to hemoglobin (about 97%)

Small amount:

• Dissolved in plasma

Internal Gas Exchange

At tissues:

• Oxygen leaves blood.

• Carbon dioxide enters blood.

External Gas Exchange

At the alveoli:

• Oxygen diffuses into blood.

• Carbon dioxide diffuses into alveoli.

Gas Exchange

Occurs by diffusion.

Diffusion:

• Molecules move from an area of higher concentration to lower concentration.

Oxygenation

The process of:

• Loading oxygen onto hemoglobin in red blood cells.

Requires:

• Open airway

• Adequate ventilation

• Functional alveoli

• Adequate perfusion

External Respiration

Occurs:

• Between alveoli and pulmonary capillaries

Oxygen:

• Alveoli → Blood

Carbon dioxide:

• Blood → Alveoli

Internal Respiration

Occurs:

• Between systemic capillaries and body cells

Oxygen:

• Blood → Cells

Carbon dioxide:

• Cells → Blood

Cellular Respiration

Occurs inside cells.

Uses:

• Oxygen

• Glucose

Produces:

• ATP

• Carbon dioxide

• Water

Pediatric Airway Differences

Children:

• Prefer nose breathing (especially infants).

• Larger occiput.

• Larger tongue.

• Smaller mandible.

• Floppier epiglottis.

• Narrower airway.

• Narrowest point is the cricoid cartilage (under 8 years old).

• Chest wall is more flexible.

• Depend more on diaphragm ("belly breathers").

Positioning:

• Place a folded towel under the shoulders to maintain a neutral airway.