Respiratory 1 Flashcards
1
Q
Increasing O2 uptake during exercise depends on …
A
Controlled increase in ventilation
- QO2 - oxygen uptake in the cell
- Oxygen to the blood and removing carbon dioxide
- Systems work together (muscle, circulation & ventilation)
2
Q
Functions of the lungs
A
- Gas exchange achieved by ventilating alveoli (oxygen & carbon dioxide via ventilation)
- Immune function - epithelial secretions, filters air, coughing, sneezing.
- Metabolic/hormonal functions.
- Speech
3
Q
Respiratory Airway
A
- Conducting airway
- Trachea -> Bronchi -> Bronchioles (nonrespiratory) - Terminal respiratory units
- Bronchioles (respiratory) -> Alveolar ducts
4
Q
Alveoli and blood-gas barrier
A
- 200 million to 600 million alveoli in the lungs
- Covered in pulmonary capillaries where gas exchange occurs
- Draining arterial blood from the alveoli are the pulmonary arterial vessels and draining oxygenated blood would be the pulmonary venous vessels
5
Q
Gas diffusion at the air-blood interface
A
- Lungs bring air to alveoli (ventilation) while pulmonary arteries bring blood to capillaries (perfusion).
- Gas diffusion occurs at the alveolar-capillary interface (~70 % of total alveolar surface).
- Total area and thickness of this ‘interface’ affect the rate of gas diffusion
6
Q
Gas exchange, ventilation and perfusion
- partial pressure
A
- Oxygen will move into the blood because the partial pressure in the lungs is higher than in the blood
- Carbon dioxide will move into the lungs because the partial pressure in the lungs in lower than in the blood
- Perfusion involves blood moving from the right side of the heart to the left side
7
Q
Ventilation during graded exercise
A
- Minute ventilation’ is the volume of air inspired or expired in one minute.
- Minute ventilation at rest is ~8-10 L/min.
- Ventilation increases in proportion to O2 uptake at lower intensities and disproportionately more as maximum VO2 is approached.
- Training – from ‘A’ to ‘C’ - increases the ‘ventilatory threshold’ (“Owles Point”) and the maximum ventilation. (REFER TO LECTURE)
- Owles point = describes the oxygen uptake (or intensity) beyond which ventilation increases much more than at lower workloads
- Maximum rates of ventilation can exceed 200 L/min in large endurance athletes.
- Alveolar ventilation and perfusion (i.e. cardiac output) rise during exercise.
8
Q
How do we breath at rest?
A
- Breathing in occurs because the diaphragm goes down (contracts) and opens up the volume inside the rib cage
- When the diaphragm relaxes we breath out
- Intercostals are also involves in breathing at rest
9
Q
The pleural cavity and breathing
- Boyles law
A
- Boyle’s Law - the pressure in an enclosed container is inversely proportional to the volume
- Expansion of thoracic or ‘chest’ volume increases the volume of the pleural cavity and reduces its pressure.
- This allows the lungs to expand and decrease lung pressure.
- Since lung pressure is now less than atmospheric pressure, air rushes into the lungs and results in inspiration.
- The opposite occurs during expiration.
- Pleural cavity - between the ribs and the soft tissue of the lungs. It is a lubricating fluid that prevents friction between the ribs and lungs
10
Q
How do we breath during exercise
A
- Inspiration: active and also involves ‘accessory’ muscles which increase the strength of inspiration.
- Expiration: becomes active and involves internal intercostals and, particularly, abdominal muscles.
11
Q
Lung volumes during rest and exercise
A
- Tidal volume is the volume of a breath (inspired or expired). Rest: 500ml, exercise: 2-4L
- Anatomic dead space is the volume of air which does not reach the respiratory zone. (stays in the conducting zone) 150 ml
- Alveolar volume is the total volume of air in all alveoli. 3L
- Pulmonary capillary volume is the total volume of blood in all pulmonary capillaries. Rest: 100ml, exercise: 130ml
12
Q
Volumes and flows during rest
A
- Flow is a volume per unit time.
- Minute ventilation = TV × fb. (7500ml/min)
- ml/min = ml/breath × breath/min.]
- Breathing frequency: 15 b/min
- Alveolar ventilation = (TV– dead space) × fb . (5250ml/min)
- Alveolar ventilation and pulmonary blood (5L/min) flows are very similar: 1 to 1 matching.
13
Q
Breath volumes during rest and exercise
A
During exercise there is an increase in tidal volume (2-4L)
14
Q
Ventilation, tidal volume and breathing frequency
A
During graded exercise, your minute ventilation increases and increases because your tidal volume and breathing frequency increase
- Tidal volume increases much more abruptly early on and then tends to plateau
- Breathing frequency increases more regularly and then takes off
- There is a disproportionate increase in breathing frequency at higher intensity
15
Q
Spirometric volumes and flows at rest
A
The women - asked to take a deep breath and forcefully expire the air
- FEV1 - forces expiratory volume in one second
- Someone with asthma would have a lower FEV1
- FVC (forced vital capacity) - the difference between the maximum air inhaled and what’s left after exhalation
(REFER TO LECTURE FOR GRAPH)
16
Q
Training
- swim training & CF
A
- Swim training increases many of the lung volumes by ~10 -30 % * and some dynamic respiratory measures (e.g., FEV 1: Arthur et al. 1993 Eur Resp J. 6: 237 -247).
- Cystic fibrosis (CF) reduces airway function (i.e. decreased lung volumes and dynamic breathing function).
- Inspiratory muscle training in CF - several weeks of high -intensity breathing training – results in increased diaphragm thickness and contraction thickening, maximum inspiratory mouth pressures, vital capacity, total lung capacity and exercise tolerance (Enright et al. 2004 Chest 126: 405 -411).
(GRAPH)
17
Q
Respiratory volumes during exercise
- Operating ranges
A
- During normal breathing at rest, lung volumes vary within a small operating range between the end-inspiratory lung volume and end-expiratory lung volume.
- During exercise, this operating range increases – because tidal volume increases – both towards the inspiratory limit (“IC”) and expiratory limit (residual volume).
- The widening of this operating range of lung volume stops at higher intensities.
- This is a ‘normal’ response.
- Under many circumstances an abnormal response is observed and might restrict breathing, increase the work of breathing and limit exercise tolerance
18
Q
Hyperinflated lungs
- In some cardiopulmonary diseases…
A
- In some cardiopulmonary diseases (e.g., COPD, PH), the operating range of lung volume is shifted up at rest and/or during exercise and is referred to as ‘hyperinflation’.
- Dynamic hyperinflation (DH) refers to an increase in the lung volume at the end of expiration (“EELV”) during exercise.
- Dynamic hyperinflation, as well as hyperinflation at rest, are thought to contribute to the sensation of breathlessness and might limit exercise tolerance in some cardiopulmonary diseases.
19
Q
Fit women work harder to breath
A
- Women have smaller lungs and airways relative to body size.
- Figure (2nd grapth) based on Guenette et al. (2007) J Physiology 581.3: 1309-1322.
• Fit men (V̇O2max = 70 ml/min/kg) and women (V̇O2max = 60 ml/min/kg). - Orange line is women.
- At higher intensities, women experience greater limitation in expiration and more closely approach the inspiratory limit.
At a given minute ventilation, the work of breathing is higher (see below).
20
Q
Oxygen cost of breathing
A
- Breathing muscles consume oxygen at a rate proportional to their work output.
- The O2 cost of breathing increases exponentially at higher ventilations.
- In normal individuals, breathing muscles can consume ~15 % of the total V̇O2 at V̇O2max.
- This percentage is much higher in lung disease (e.g, emphysema), such that most of the oxygen consumed is used by breathing muscles…and at rest!
