19.3-2 Breathing Mechanism Riley, Jacob, and Blake

Pre-Info Expiration is the release of air from the lungs through the nose or mouth. Inspiration is the drawing of air into the lungs through the nose or mouth.

Respiratory Air Volumes and Capacities

Intro To Respiratory Air Volumes Different volumes of air moving in or out of the lungs are called respiratory volumes. Measurement of these air volumes is done with a spirometer, this process is called spirometry. Three of the four respiratory volumes can be measured with a spirometer. (residual volume cannot)

Tidal Volume The total volume of air that travels throughout the airways and alveoli(tiny air sacs within the lungs) during a respiratory cycle. On a normal inspiration about 500 mL of air is taken in, roughly the same amount of air is expirated. 500 mL is the average resting tidal volume, or the normal tidal volume in the absence of exercise or other conditions.

Inspiratory Reserve Volume (complemental air) The maximum amount of extra air that can be purposefully be drawn into the lungs in addition to a normal inspiration. This totals to around 3000 mL of air, not including the tidal volume already taken in.

Expiratory Reserve Volume (supplemental air) The maximum amount of air that can be purposefully be exhaled from the lungs in addition to a normal expiration. This totals to around 1100 mL of air, not including the also released tidal volume.

Residual Volume Volume of air that remains within the lungs even after a maximum expiratory effort. This amounts to about 1200 mL. Residual volume cannot be measured with a spirometer because it remains still inside your lungs. Special gas dilution techniques must be used to measure residual volume. (Gas container test)

Intro To Air Capacities There are four respiratory capacities, these are calculated by adding two or more respiratory volumes together.

Vital Capacity The maximum volume of air one can exhale after the deepest breath possible. Inspiratory reserve volume, tidal volume, and expiratory reserve volume combined. 3000 mL + 500 mL + 1100 mL = Vital Capacity 4600 mL

Inspiratory Capacity The maximum volume of air a person can inhale after a resting expiration. Tidal volume and inspiratory reserve volume combined. 500 mL + 3000 mL = Inspiratory Capacity 3500 mL

Functional Residual Capacity Volume of air that remains in the lungs following a resting expiration. Expiratory reserve volume and residual volume combined. 1100 mL + 1200 mL = Functional Residual Capacity 2300 mL

Total Lung Capacity The total volume of air that the lungs can withhold. Vital capacity, and residual volume combined. 4600 mL + 1200 mL = Total Lung Capacity 5800 mL

Spirometry In Depth Can help to diagnose various lung conditions, most often chronic obstructive pulmonary disease (COPD) It does not always rule out some forms of lung disease, such as asthma Height and weight will be measured, then the patient will breathe into a spirometer (with the nose clipped), and then will exhale completely. Measures amount and speed of expiration.

Spirometry In Depth (Part 2) A normal, restrictive, or obstructive pattern is indicated through the test. Obstructive patterns normally indicate diseases that narrow airways such some types of asthma and COPD. Restrictive patterns often show that there is some sort of lung deformity or scarring.

Anatomic Dead Space Some of the air, entered through the respiratory tract, does not reach the alveoli. About 150 mL of air gets stuck in the trachea, bronchi, and bronchioles. Gases can not be exchanged through these walls and thus it is called the Anatomic Dead Space.

Alveolar Dead Space Sometimes, due to poor blood flow in adjacent capillaries, alveoli in some regions of the lungs do not function correctly. This creates Alveolar Dead Space. It represents space in the alveoli that does not participate in oxygen-carbon dioxide exchange.

Physiological Dead Space The Anatomic Dead Space and Alveolar Dead Space combined. Most commonly the Anatomic and Physiological Dead Spaces are the same in volume. (150 mL)

Alveolar Ventilation

Minute Ventilation Volume of air moved into respiratory passages each minute minute volume = tidal volume * breathing rate For Example: If the tidal volume is 500 mL and the breathing rate is 12 breaths per minute, the minute ventilation would be 6,000 mL per minute Much of the new air remains in the physiologic dead space

Alveolar Ventilation Rate Alveolar ventilation rate is the more important rate It affects the concentration of oxygen and carbon dioxide in the alveoli This concentration is also important for gas exchange with the blood

Alveolar Ventilation Rate Since all air doesn’t make it to the alveoli, the alveolar ventilation rate is calculated by subtracting the physiologic dead space by the tidal volume and then multiplying by the breathing rate. Example: 500 mL (tidal volume) - 150 mL (dead space) = 350 mL 350 mL * 12 breaths per minute = 4,200 mL per minute

Nonrespiratory Air Movements

Reflexes Reflexes are usually the cause for nonrespiratory air movements.

Coughing Mechanism: A deep breath is taken, glottis is closed, and air is forced against the closure; suddenly the glottis opens and sends the air bursting upward. Function: To clear the lower respiratory passages

Sneezing Mechanism: It’s the same as coughing, but when the air bursts upward, the uvula depresses causing the air to pass through the nasal cavity. Function: Clear the upper respiratory passages

Laughing Mechanism: Deep breath released in short expirations Function: Express happiness

Crying Mechanism: Same as laughing Function: Express sadness

Hiccuping Mechanism: Diaphragm contracts spasmodically while the glottis is closed Function: No known function

Yawning Mechanism: Deep breath in Function: There are some hypotheses but no function

Analogy: The Not-So-Average High School Parking Lot (Nonrespiratory Air Movements)

Maladies

COPD Chronic Obstructive Pulmonary Disease is a group of inflammatory diseases that cause obstructed airflow of the lungs. Two main types are chronic bronchitis and emphysema. Symptoms include breathing difficulty, coughing, mucus production and wheezing. Mostly caused by long-term exposure to gases, most commonly cigarette smoke.

Emphysema Progressive, degenerative disease Destroys alveolar walls Decreases total surface area of alveoli Alveolar walls lose elasticity Capillary networks of alveoli also diminish

Emphysema 3% of the 2 million people in the US inherit the condition Most have a defective enzyme Majority of cases are due to smoking or other respiratory irritants Type of chronic obstructive pulmonary disease (COPD)

Asthma Harder to force air out of lungs Narrowed air passageways Increase in asthma in US Due to a too-clean environment Children raised with cats or dogs have less of a chance to develop asthma Hygiene Hypothesis- association of a primed immune system with lower risk of developing asthma

Bronchial Asthma Allergic reaction to foreign antigens in the airways Pollen or material on dust mites Mucus normally will trap these allergens Allergens irritate smooth muscle causing bronchoconstriction Breathing becomes difficult

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