4. Ventilation Flashcards

1
Q

Minute ventilation

A

Volume of air expired in 1 minute or per minute

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2
Q

Respiratory rate

A

Frequency of breathing per minute

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3
Q

Alveolar ventilation

A

Volume of air reaching the respiratory zone per minute

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4
Q

Respiration

A

Process of generating ATP

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5
Q

Anatomical dead space

A

Capacity of airways incapable of undertaking gas exchange

Includes entirety of conducting airways and upper respiratory tract

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6
Q

Alveolar dead space

A

Capacity of airways that should be able to undertake gas exchange but can’t (usually due to absent/ inadequate blood flow)
e.g. hypoperfused alveoli

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7
Q

Physiological dead space

A

Sum of alveolar + anatomical dead space

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8
Q

Hypoventilation

A

Deficient ventilation of the lungs; unable to meet metabolic demand
(results in increased PO2 – acidosis)

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9
Q

Hyperventilation

A

Excessive ventilation of the lungs atop of metabolic demand

results in reduced PCO2 - alkalosis

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10
Q

Hyperpnoea

A

Increased depth of breathing (to meet metabolic demand)

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11
Q

Hypopnoea

A

Decreased depth of breathing (inadequate to meet metabolic demand)

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12
Q

Apnoea

A

Cessation of breathing

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13
Q

Dyspnoea

A

Difficulty breathing

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14
Q

Bradypnoea

A

Abnormally slow breathing rate

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15
Q

Tachypnoea

A

Abnormally fast breathing rate

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16
Q

Orthopnoea

A

Positional difficulty in breathing

e.g. when lying down

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17
Q

Tidal volume (TV or VT)

A

Volume of air inspired and expired during regular breathing (not necessarily at rest)
~500mL at rest

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18
Q

Inspiratory reserve volume (IRV)

A

Volume of air that can be inspired after a tidal inspiration

2.7 L at rest

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19
Q

Expiratory reserve volume (ERV)

A

Volume of air that can be expired after a tidal expiration.

~1.3 L at rest

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20
Q

Residual volume (RV)

A

Volume of air that cannot be emptied from the lungs, no matter how hard you expire. This is fixed because of the lung-chest wall interface.
~1.2 L

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21
Q

Equation for total lung capacity (TLC)

A

TLC = RV + IRV + TV + ERV

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22
Q

Define total lung capacity

A

Maximum capacity of the lungs

~6L

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23
Q

Functional residual capacity (FRC) equation

A

FRC= RV + ERV

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24
Q

Define functional residual capacity

A

Volume of air in the lungs following a tidal expiration at rest.
Represents the “default” volume of the lungs, when the lung recoil (inwards) and chest recoil (outwards) are in equilibrium

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25
Inspiratory capacity (IC) equation
IC = TV + IRV
26
Define inspiratory capacity
Maximum volume of air the lungs can draw in from the equilibrium FRC point
27
Vital capacity (VC) equations
``` VC= TLC - RV VC= TV + IRV + ERV ```
28
Define Vital capacity
volume of air between the maximum and minimum achievable volumes "how much useful air you can get in that you can influence"
29
What 5 factors affect lung volumes and capacities?
``` Body size (height, shape: Taller= Bigger lungs) Sex (Males usually= Bigger lungs) Disease (pulmonary, neurological) Age (chronological, physical) Fitness (innate, training) ```
30
Dead space (VD)
Parts of the airways that don't participate in gas exchange
31
How is anatomical dead space measured?
Not with spirometry | Requires dilution test
32
Describe the dilution test used to measure anatomical dead space
Known volume of inert gas (e.g. helium) is inspired and expired into a closed circuit. After enough breathing to equilibrate it with the air already in the airway a sample of the original volume is measured for concentration of inert gas. The ratio of that to the original concentration, and spirometry data are used to calculate VD. Remember: tubing connected to the airway increases the volume of anatomical dead space.
33
What reversible procedures could be performed to increase dead space?
Anaesthetic circuit | Snorkelling
34
What reversible procedures could be performed to decrease dead space?
Tracheostomy | Cricothyrocotomy
35
What is the volume of alveolar dead space in a healthy human?
Effectively 0
36
Alveolar ventilation during tidal breathing (subconscious) equation
Valv = VT - VD | Difference between tidal volume and dead space
37
Volume of pleural fluid
Very small (few ml)
38
Intrapleural cavity pressure (PpI) in healthy individuals
-5 cmH2O Always negative due to natural recoil of chest wall and lungs
39
Atmospheric pressure in cmH2O
0 cmH2O
40
Tendency of chest wall and lung
Chest wall: Spring outwards Lung: Recoil inwards Forces in equilibrium at end-tidal expiration (FRC); neutral position
41
If inspiratory muscle effort + chest recoil > lung recoil
Results in inspiration
42
If chest recoil < lung recoil + expiratory muscle effort
Results in expiration
43
What is the pleural cavity?
Gap between pleural membranes Fixed volume Contains protein rich pleural fluid
44
What is the consequence of breaching the pleural cavity?
Bad | Lung relies on the pleural fluid to operate normal lung mechanics
45
Haemothorax
Accumulation of blood in pleural cavity Impedes lung function Compresses the lung- less space to expand and fill with air Harder to breath
46
Pneumothorax
Puncture allows air into pleural cavity Interrupts ability of lung to work as a single unit Dissipation of 'tension' causes lung to recoil and chest wall to expand
47
Describe how the pleural cavity allows the chest wall and the lungs to move in unison
Pleural cavity has a fixed volume and is at negative pressure. "Partial vacuum" So when the chest wall expands, the lung gets pulled with it.
48
What is needed to generate airflow?
A pressure gradient | Air flows from high to low pressure
49
What type of pressure breathing is normal?
Negative pressure breathing | Palv is reduced below Patm
50
3 Examples of positive pressure breathing
Mechanical ventilation CPR Fighter pilots
51
What are the pressures in positive pressure breathing?
Patm is increased above Palv
52
At FRC mechanical forces of the lung are in equilibrium...
Needs to be imbalanced to generate airflow and stimulate ventilation Achieved by increasing atm or intrapulmonary pressure(+) Or by decreasing intrapleural pressure (-)
53
How does the respiartory musculature decrease intrathoracic pressure?
By creating a partial vacuum Diaphragm contracts down and external intercostals pull ribs up and out Lung is elastic, expandable tissue that stretches to fill the space (maintaining intrapleural volume)
54
Atmospheric pressure (Patm)
Always 0 cmH2O | Unless having CPR/ Ventilator
55
Intrapleural pressure (Ppl or Plp)
-5 cmH2O at rest | Not equal along length of lung
56
Intraalveolar pressure (Palv)
0 cmH2O at rest
57
Transmural pressures (PTP)
Pressure inside relative to pressure outside | P inside - P outside
58
Transmural pressure in lung (PTP)
Palv - Ppl | Difference in pressure between alveolar sacs and pleural cavity
59
Transthoracic pressure in lung (PTT)
Ppl - Patm | Difference in pressure between pleural cavity and atmosphere
60
Transrespiratory system pressure (PRS)
Palv - Patm | Difference in pressure between alveolar sacs and atmosphere
61
Importance of transrespiratory pressure and transmural pressure
Dictates airflow Negative PRS leads to inspiration Positive PTP leads to expiration
62
Describe the mechanical effect of the diaphragm
Pulling force in 1 direction | Like a syringe
63
Describe the mechanical effect of other respiratory muscles
Upwards and outwards swinging force (inspiration) | Like a bucket handle
64
Describe the chest wall relationship pressure-volume graph shape of a healthy lung
Sigmoid In middle volume: volume that changes per unit pressure is significant (less effort to change pressure) At extremities of volume: same unit of pressure has a less significant effect on volume
65
What occurs at volume plateaus on chest wall relationship graph?
Changes in pressure no longer generate changes in airflow
66
FVC
Forced vital capacity
67
FEV1
Forced expiratory volume in 1 second
68
FET
Forced expiratory time
69
FEV1 / FVC ratio
Compares how much air comes out in 1 second
70
FEV1 / FVC ratio in normal, restrictive and obstructive individuals
Normal: 73% Restrictive: 97% Obstructive: 53%
71
Restrictive lung disease
Restricts capacity of lungs to fill | "bear hug" disease: bear hugs you and you try to breath
72
Obstructive disease
Obstruction to airflow in the lungs | "Someone partly covers your mouth and you try to breath in"
73
PEF
Peak expiratory flow
74
How would you use serial PEF measurements to discriminate between asthma and COPD?
COPD: Stable PEF Asthma: Variable PEF
75
Flow volume loops: | Mild obstructive disease
Displaced to the left | Indented exhalation curve
76
Flow volume loops: | Severe obstructive disease
Shorter curve Displaced to the left Indented exhalation curve
77
Flow volume loops: | Restrictive disease
Displaced to the right | Narrower curve
78
Flow volume loops: | Variable extrathoracic obstruction
Blunted inspiratory curve | Otherwise normal
79
Flow volume loops: | Variable intrathoracic obstruction
Blunted expiratory curve | Otherwise normal
80
Flow volume loops: | Fixed airway obstruction
Blunted inspiratory curve Blunted expiratory curve Otherwise normal