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form of energy The amount of energy transferred by a force acting over a distance |
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| the work done by a force of 1 N acting over a distance of 1 meter |
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| work of a ventilator during inspiration |
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Definition
work is the product of the volume of gas moved and the pressure required |
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| mathematical formula for work by ventilator |
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Definition
work done = PA X V/A = PV this formula shows that the work done is the product of the volume of gas moved and the pressure required pressure must be in Pascals volume must be in cubic meters (1m3 = 103 liters) |
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| Pressure from the ventilator equals 0.6 kPa above ATM and remains steady at this value until the lungs are inflated with 0.5 L of air. Calculatethe work done by the ventilator in SI units. |
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Definition
work done = (0.6x103) Pa X (0.5x10-3) m3 = 0.3 Joules = 300 mJ of work required for inspiration |
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Definition
| cannot be lost BUT is converted from one form to another |
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| Mechanical Energy & Breathing |
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Definition
Half the mechanical energy used is stored as potential energy in the elastic tissues of the lungs and chest wall. This energy is subsequently used for the work of expiration. The remaining half of the mechanical energy of inspiration is used in overcoming airway resistance and in moving the air and tissues. |
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Definition
| The intrapleural space,a potential space, is found between the parietal pleura of the internal chest wall and the visceral pleura covering the lung. The intra-pleural pressure is negative (subatmospheric) because the lungs recoil inward and the chest wall recoils outward. The inward and outward forces are equal at FRC (functional residual capacity) (from Valley Review pg 399). |
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During inspiration intrapleural pressure becomes more negative (subatmospheric). Intrapulmonary pressure, which was zero(the same as atmospheric pressure) at end-expiration becomes negative (subatmospheric) at the start of inspiration. Air enters the lung because the intrapulmonary pressure is less than atmospheric. At end-inspiration, intrapulmonary pressure is zero (the same as atmospheric). During expiration, intrapleural pressure becomes less negative, and intrapulmonary pressure becomes positive (above atmospheric). Air is exhaled because intrapulmonary pressure exceeds atmospheric pressure during this time. Intrapulmonary pressure returns to zero (atmospheric pressure) at end-expiration. (from Valley Review page 399)
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Definition
(1) Intraplural pressure (pressure in the space between the inside of the chest wall in the lungs) is always negative during normal tidal breathing; (2) Intraplueral pressure becomes more negative during inspiration and less negative during expiration; (3) Intrapulmonary pressure is negative during inspiration and positive during expiration. (from Valley review page 399) |
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Term
| maneuvers to make intrapleural pressure positive |
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Definition
forced expiration or Valsalva's maneuver (from Valley Review page 399) |
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Term
| work of inspiration in spontaneous breathing |
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Definition
In inspiration, the pressure and the intraplural space is subatmospheric and decreases further due to contraction of the diaphragm (force). Chest expansion is from: (1) the diaphragm acting on the lower margin of the rib cage to raise it, (2) the intercostal muscles,especially the external intercostals, acting to raise the ribs, and (3) the scalene muscles raising the upper ribs of the thoracic cage. |
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Term
| energy changes during inspiration |
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Definition
| in the respiratory muscles,10% of the chemical energy is turned into mechanical energy and 90% into heat. |
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Term
| measuring the work of inspiration in a spontaneously breathing patient |
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Definition
total work is difficult to measure. Volumes inspired may be measured by a pneumotachograph but the pressures exerted by the respiratory muscles in the chest wall cannot be monitored directly. |
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| measuring work of inspiration with controlled ventilation |
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Definition
A pneumotachograph measures the volume inspired and intrapleural pressure changes with a balloon tip and a graph. |
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| calculating the power of the heart |
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Definition
If mean arterial pressure is 12kPa (90 mm Hg), pulmonary venous pressure is 0 kPa, and left CO is 5 liters/min, calculate power of left heart:
power L = 12 X103 Pa X (5 X 10-3/60 m3 s-1) = 1 W If the mean pulmonary artery pressure is 2.4 kPa (18 mm Hg) above the CVP, calculate power of right heart: power R = 2.4 X103 Pa X (5 X 10-3/60 m3 s-1)=0.2 W Total power of heart = 1.2 W |
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Term
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Definition
power is the rate of working and is measured in watts. 1 Watt is 1 Joule per second W = J s-1 |
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Term
| If the work of one inspiration is 300 mJ and the respiratory rate is 16 per minute, calculate the power of breathing? |
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Definition
| W = J s-1 300 mJ X 16/60 s-1 = 80 mW |
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| efficiency of respiratory muscles |
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Definition
Only 10% efficient in producing mechanical energy the rest is dissipated as heat. Actual energy requirements for 80 mW is actually 10 times greater, i.e., 800 mW |
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| effects of type of flow on the power of breathing |
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Definition
| pressure gradients are greater for turbulent flow than laminar flow |
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Term
| effects of hyperventilation |
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Definition
Quiet ventlation flow is laminar As ventilation increases, flow becomes turbulent Power of breathing increases rapidly: * High oxygen consumption by resp muscles * Oxygen requirements increase * Hypoxia may result in some with respiratory diseases. |
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Term
| work of myocardial contraction |
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Definition
| A graph can be used to measure the work of myocardial contraction by plotting changes in pressure and volume. The area of the loop is the work done. |
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Definition
| Product of pressure difference and fluid flow as applied to CO. E = P X V |
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Term
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Definition
pressure difference X flow can be calculated for the right or left side |
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Term
| effect of blood pressure and cardiac output on the work of the heart |
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Definition
the work of the heart is directly proportional to the mean blood pressure and cardiac output. Hypertension causes more energy, more work, and higher CO,which can lead to heart failure Hypotension decreases the energy and more provided that CO is not simultaneously raised. |
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Term
| Force/Distance R/T Inspiration |
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Definition
Work done = F X D In relation to inspiration F = Pressure and D=volume of gas moved Remember P=F/A (F = PA) Remember V = D/A (D=V/A) Therefore as above equation for work done Work done = PA x V/A = PV |
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Term
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Definition
energy which is possessed by an object due to its motion or due to its position An object which possesses mechanical energy is able to do work |
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| FORMS OF MECHANICAL ENERGY |
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Definition
can be either: * kinetic energy (energy of motion) or * potential energy (stored energy of position) |
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Definition
| Stored energy of position possessed by an object |
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| Two Forms of Potential Energy |
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Definition
Gravitational potential energy Elastic potential energy |
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Term
| GRAVITATIONAL POTENTIAL ENERGY |
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Definition
The energy stored in an object as the result of its vertical position or height The energy is stored as the result of the gravitational attraction of the Earth for the object |
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Definition
Energy stored in elastic materials as the result of their stretching or compressing Amount of elastic potential energy stored in such a device is related to the amount of stretch of the device - the more stretch, the more stored energy. |
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Definition
the energy of motion. An object which has motion - whether it be vertical or horizontal motion - has kinetic energy Many forms of kinetic energy – * vibration (the energy due to vibration motion) * rotational (the energy due to rotational motion)
* translational (the energy due to motion from one location to another |
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| TRANSLATIONAL KINETIC ENERGY |
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Definition
Kinetic energy will refer to translational energy depends upon two variables: the mass (m) of the object and the speed (v) of the object kinetic energy equals one half times the mass of the object times the square of the speed of the object E = (1/2)mv2 |
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| How much kinetic energy does an object have if its mass is 5.0 kg and it is moving at a speed of 4.0 m/s? |
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Definition
E = (1/2)mv2 E = (1/2)(5.0 kg)(4.0 m/s)2 EK = 40 J Kinetic Energy equals 40 J. |
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Term
| ENERGY CHANGES--INSPIRATION |
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Definition
Half mechanical energy is stored as potential energy in elastic tissue of the lungs and chest wall This potential energy is later used for expiration Remaining mechanical energy is used to overcome airway resistance and in moving air and tissue |
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Term
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Definition
Work is ½ PV as related to work of inspiration Energy used to overcome: * Tissue resistance in lungs * Chest wall compliance * Airway resistance |
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Term
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Definition
Respiratory muscle contraction during inhalation Work is accomplished in three phases: (1) Lung Compliance Work that is required to expand the LUNGS against its elastic forces (2) Tissue Resistance Work that is required to overcome the viscosity of the lung and chest wall structures (3) Airway Resistance Work that is required to overcome airway resistance during the movement of air into the lungs. |
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| EXPIRATION AND "WORK OF BREATHING" |
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Definition
"Work of Breathing" does not refer to expiration Entirely a passive process caused by elastic recoil of the lung and chest cage |
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Term
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Definition
80 W The energy requirements for breathing is 1% of the total metabolism. |
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| LAMINAR FLOW AND PRESSURE |
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Definition
Pressure is proportional to flow ↑ pressure ↑ flow |
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| Turbulent Flow and Pressure |
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Definition
Pressure is proportional to the square of flow In order to double flow pressure must be increased by a factor of four (Reynold's Number) |
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CALCULATE THE POWER OF THE LEFT HEART If MAP = 12kPa (90 mm Hg) (1 kPa = 7.5 mm Hg), Pulmonary Venous Pressure = 0 kPa CO = 5 L/min |
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Definition
12 x 103 Pa X 5 x 10-3 m3 s-1 = 1W 60 |
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CALCULATE THE POWER OF THE RIGHT HEART If Mean PAP is 2.4kPa (18 mm Hg) above the CVP (1 kPa = 7.5 mm Hg) and the CO = 5 L/min |
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Definition
2.4 x 103 Pa X 5 X 10m3 s-1 = 0.2W 60 |
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