Respiratory System Response to Exercise - Breathing

Pulmonary Ventilation

• air in the atmosphere

• air containing O2 enters the lungs → during inspiration

• air containing CO2 is breathed out → during expiration

Alveolar Gas Exchange

• O2 moves into blood from alveoli

• CO2 moves into alveoli from blood

Gas Transport

• blood transports O2 from lungs to body tissues

• blood transports CO2 from tissues back to lungs

Systemic Gas Exchange

• O2 moves into systemic cells from blood

• CO2 moves into blood from cells

Diaphragm

muscle responsible for inspiration (at rest)

• expands lungs

• changes volume and pressure

Respiratory Zone

rapid gas exchange

Respiratory Zone Contains

• approximately 300 million alveoli

• huge surface area (60-80 m2)

Each Alveolus Is

only 1 layer thick

Respiratory Membrane

• very thin → enhances exchange

• huge surface area for exchange

• possible barrier for gas exchange

Alveoli Are

very close to blood

How Does the Lung Change Volume

inspiratory muscles contract → expands lungs

Breathing is A

active process

• muscle contraction → expanding lungs

Air Flow Due To

pressure gradients

• similar to BF

Inspiratory Muscles Act as A

“pump”

• lungs to expand

• due to pleural fluid

Expiration at Rest

is passive (air moves out)

Expiration During Exercise

is active

Muscles of Respiration During Exercise

• internal abdominal oblique

• transversus abdominis

• rectus abdominis

Boyle’s Law

pressure of a gas is inversely proportional to the volume of it container

• increase volume, decrease pressure

• decrease volume, increase presure

Airway Resistance - Airflow Depends On

• pressure difference between two ends

• resistance within airways

Airflow Formula

airflow = P1 - P2/resistance

Airways Resistance Depends On

diameter

• smaller diameter → greater resistance

• larger diameter → lower resistance

Pulmonary Ventilation

amount of air lungs move per min (V)

Pulmonary Ventilation Determined By

1. tidal volume (VT)

2. breathing frequency (f)

Tidal Volume (VT)

amount of air moved per breath

Breathing Frequency (f)

number of breaths per minute

Pulmonary Ventilation Formula

V = VT x f

Alveolar Ventilation (VA)

volume of air that reaches the respiratory zone

• “fresh air flow per min”

Alveolar Ventilation Formula

VA = (VT - VD) x f

Dead-Space Ventilation (VD)

volume of air remaining in conducting airways

Total Minute Ventilation Formula

V = VA + VD

Minute Ventilation (VE)

air flow each minute

• how much air per breath and how many breaths per min

Minute Ventilation Formula

VE = VT x f

Resting Tidal Volume (VT)

volume of a normal breath (500 mL)

Expiratory Reserve Volume (ERV)

maximum air expired at the end of a normal expiration

Inspiratory Reserve Volume (IRV)

maximum air inspired at the end of a normal inspiration

Residual Volume (RV)

air left in the lungs after a maximal exhalation

Dynamic Ventilation Depends On

1. maximum “stroke volume” of the lungs

2. speed of moving a volume of air (breathing rate)

Maximum “Stroke Volume” of the Lungs

forced vital capacity (FVC)

• how much air we can move per breath

Speed of Moving a Volume of Air

determined by lung compliance or resistance of the respiratory passages to air and the “stiffness” imposed by the chest and lungs

Forced Expiratory Volume (FEV1)

amount of air exhaled in the first sec after max inspiration

• measured over 1 sec

FEV1 Divided by FVC Indicates

pulmonary airflow capacity

FEV1 In Healthy Individuals

equals 85%

Delineation Point for Airway Obstruction

<70%

Women Have Decreased

• lung size

• airway diameter

• diffusion surface

• static and dynamic lung function measures

What Leads to Expiratory Flow Limitations

• increased work for respiratory muscles

• increased use of ventilatory reserve during maximal exercise

• decrease lung volume and increase expiratory flow rate in TR women

• increase demand on the maximum flow-volume envelope the airways