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12 Cards in this Set
- Front
- Back
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Books |
Egans and Pilbeams and whites equipment, wilkins clinical assessment |
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breakdown |
quizes 20, lab 10%, tests 20, 5 pps 5 final 45 |
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Assignment 1 |
Egan fundamentsl RC chapter 46 page 1016-1021 Egan workbook Chapter 46 page 329-330 |
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Pressures |
Pawo- mouth or airway opening pressure Palv- alveolar pressure Ppl- intrapeural pressure Pbs- Body surface pressure Paw- Airway pressure Pl or Ptp= transpulmonary pressure (Pl = Palv - Ppl)
Pw or Ptt = Transthoracic pressure (Pbs-Palv) Pta = transairway pressure (Paw- Palv) Ptr = transrespiratory pressure (Pawo - Pbs)
Pressures and pressure gradients in the lung. Airflow is a function of the transairway pressure (Pta), which is the pressure gradient between the airway (Paw) and the alveoli (Palv)
Transpulmonary pressure (PtP) maintains alveolar inflation, and transthoracic pressure (Ptt) is the pressure needed to expand the lungs and chest wall
Transpulmonary pressure is P sub TP = P sub A - P sub PL, so alveolar pressure minus Pleural pressure
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Compliance is Delta Volume over Delta Pressure |
Elastance = Transthoracic pressure over Volume
Resistance is Delta transairway pressure over Delta Flow
Formula which states Pvent + Pmuscles = elastance x volume + resistance x flow
Pressure, volume and flow are variables (functions of time) whereas resistance and elastance (or compliance) are constants |
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Changes in pressure, volume and flow during a single spontaneous breath at FRC, functional residual capacity |
Pressures 0, then with inspiration, pressure negative in the lungs, and so on a good V/Q is 80% so 400 to 500 for example
perfusion in excess of ventilation is a shunt
V(ventilation) greater than Q(perfusion) is deadspace, Increase PaCO2
Q greater than V is a shunt and thats decreased PaO2
Anatomical deadspace and alveolar deadspace is called physiological deadspace
Effect of spontaneous ventilation and PPV(positive pressure ventilation on gas distribution in a supine subject.
During spontaneous ventilation diaphragmatic action distributes most ventilation to the dependent zones of the lungs, where perfusion is greatest, however, next line...
PPV reverses this normal pattern of gas distribution, and most delivered volume is directed to the upper lung zones
PPV increases deadspace and shunting in some parts of the lung
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negative pressure ventalation is more physiologic |
negative pressure ventilation, in other words, Iron lung, decreases pressures outside the lung and pull the chest out.
Positive pressure ventilation increases ventilation in the upper airways, this leads to deadspace
Changes in pressure, volume and flow during a single decelerating flow, positive pressure breath.
Arrows into and out of the trachea represent airflow
Spontaneous ventilation and negative pressure ventilation are quite similar (physiologic) |
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Effects of mechanical ventilation |
Increase P sub TP so an increase in transpulmonary pressure P sup TP = P sub ALV - P sub PL. Transpulmonary pressure increases with mechanical ventilation
Also interpulmonary pressure is increased increase P sub IP
ALso it decreases venous return (preload) decreases Venous return
This decreases CO, known as starlings law, which states, the more a muscle is stretched, the more it will contract.
It also decreases Renal perfusion because cardiac output is decreased
This leads to an increase in ADH, which is anti diaretic hormone produced by the kidneys
This decreases urine output
this increases intercranial pressure
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Goals of mechanical ventilation |
Decrease the work of breathing IPPB, CPAP, BIPAP, flutter valve, thereapep, all reduce work of breathing thats all positive pressure ventilation :Pressure gradient change :Decrease respiratory muscle work Support of manipulate gas exchange :Vsup A(alveolar ventilation) :O2 delivery (DO2) - CaO2 x CO :this increases surface area and FRC Increase lung volumes as well:this increases surface area and FRC:Reverse/prevent atelectasis w/ PEEP:FRC :Reverse/prevent atelectasis w/ PEEP :FRC :Increase Lung Compliance PaCO2 is inversely related to alveolar ventilation |
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Increase ventilation to the upper lung zones where there is less perfusion, increases Vd(deadspace) |
Also, increase alveolar pressure in the better ventilation upper lung zones diverts blood flow away from these areas to those receiving the least ventilation leads to areas with decrease V/Q and Decrease oxygenation |
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Effects of positive pressure ventilation on lung mechanics |
Increasing FRC is a desired effect for us, this increases surface area. Effects are Delivered pressure :Peak inspiratory pressure (PiP) is the pressure necessary to overcome: ::Airway resistance (Raw) smaller airway, more pressure necessary to deliver gas ::Lung compliance (CL) Compliance is delta V over delta P ::Chest wall compliance :PsubPLAT is static pressure after breath has been delivered P (pressure)= 8nl over pie R to the forth ::Palv at full VT so alveolar pressure at full tidal volume Normal compliance is 50 to 70 on a ventilator patient, but normal is 100 for us |
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Resistive pressure |
Is the difference between the peak pressure and the plateau pressure Elastic pressure is the difference between the plateau pressure and the empty normal compliance is 100 ml Normal airway resistance is 0 to 2 cmH20 per liter per second |
