Test 4 mech. vent. -Ch13

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When would you want to change Vt and rate?

to correct resp. alkalosis or acidosis

To correct resp. acidosis you could do what to the Va?

increase it

Causes of acute resp. acidosis

pulm. edema, pneumonia, aw disease, pleural effusions, chest wall abnormalities, neuromuscular disorders

There are two ways you could correct resp. acidosis in VV?

increase the vt to 12 ml/kg of ideal body weight, or if vt is already set at 12 ml/kg of ideal body weight, you could chg the f to correct high Co2

How could you correct resp. acidosis in PV?

increase or decrease the pressure to achieve Vt of 12 ml/kg IBW. then measure the exVt

Causes of Respiratory Alkalosis

hypoxia with compensated hyperventilation, meds, mech. vent., CNS disorders, anxiety, metabolic problems

To correct Resp. Alkalosis in VV, you could?

decrease the f to decrease the Vt

How could you correct resp. alkalosis in PV?

decrease f then set pressure. When you get to a Vt of 12 ml/kg IBW, leave pressure setting there. bc in PV pressure and volume are directly measured

metabolic acidosis

pts at risk for developing resp. muscle fatigue

causes of metabolic acidosis

ketoacidosis, uremic acidosis, diarrhea, renal loss, lactic acidosis, toxins

causes of metabolic alkalosis

vomiting, diuretic, potassium deficiency, bicarb administration

If pure respiratory acidosis persists even after Va has been increased, the pt may have a problem with

increased deadspace

causes of increased deadspace

pulmonary embolism, decreased CO-resulting in low pulmonary perfusion

increased deadspace can also occur when vent support reduces pulmonary blood flow to the lungs by causing

high alveolar pressure, such as application of high peep

Normal Vd/Vt

O.2 to 0.4

EQ for Vd/Vt

Paco2-Peco2/ Paco2

Historically, iatrogenic hyperventilation was used in pts with

acute head injury and increased ICP

Normal ICP


hyperventilaiton reduces Co2 in the blood which is assc. with constriction of cerebral blood vessels and a

decrease in blood flow to the brain

For head injury's with increased ICP

do not recommend prophylactic hyperventilation (Paco2 <25 mmhg) during the 1st 24 hrs

Iatrogenic hyperventilation is only used for _________ when ICP is elevated

brief periods

Pt has a increased ICP, hyperventilated them will

decrease CO2, blood flow to brain

Mild hyperventilation (Paco2 30-35 mmhg) may be used for

longer periods in situations in which increased ICP is refractory to standard txs of sedation, analgesia, neuromuscular block, cerebralspinal fluid drainage

Paco2 should at least be maintained at normal levls for

1st 24 hrs

Occasionally it becomes impossible to maintain normal vent. without risking

lung damage from high pressure and volumes

Pts with ARDS or Status asthmaticus and sometimes COPD, who require vent support are at risk for

vent-induced injury

With permissive hypercapnia you want to

sedate pt (b/c increased Co2 stimulates the drive to breath), let Co2 rise (>50 to 150 mm hg), PH fall ( >7.10 to 7.30), gradually rise not abruptly

Co2 >200 mmhg can result in

Co2 narcosis

Efforts to keep Paco2 near a pts normal might include

removing sources of mech. deadspace, increasing the f

When the decision is made to allow Paco2 to increase, the following may be used

Allow Co2 to increase and Ph to decrease with out changing rate or vol, avoid high vent pressure and maintain O2, administer sodium bicarb-THAM-or carbicarb to keep Ph > 7.25

to decrease Co2 production you can

use a paralytic, cooling pt, restrict glucose intake

Co2 is a powerful

vasodilator of cerebral vessels

increased Co2 levels can result in

cerebral edema and increase ICp

PHY (permissive hyperventilation) is contraindicated in

head traum, intra cranial disease

PHY (permissive hyperventilation) is also contraindicated in

pts with closed head injury and ARDS; so you would want to change to PV, increase rate slightly to maintain PH, then let the Co2 rise

Circulatory effects with PHY

decreased MI contractility, arrythmias, vasodilation- which results in increased CO, pulmonary hypertension

During mech. vent several techniques can be used to help

clear secretions from the AW

You clear secretions from an artifical aw by


Suctioning is performed

PRN, based on assessment of the pt (BS) and visibility examing the artificial aw ( if you can see it)

Acute CHF pts

often have pink frothy secretions that do not block the aw, so suctioning is not necessary. secretions will continue until the cause has been treated.

suctioning CHF pts with pulmonary edema will only worsen the

hypoxemia, which is commonly seen in these pts

Suctioning should be preceded and followed by

hyperoxygenation with 100% O2 for 30sec (before), then 1 min after

hyperoxygenating and hyperventilating pts before/after suctioning can be done by

resusctitation bag

Sx must not exceed how long

15 sec

What are the suctioning pressure for adults

-100 to -120 mmhg

what are the suctioning pressure for a child

-80 to -100 mmhg

what are the suctioning pressure for an infant

-60 to -100 mmhg

Complications with suctioning

can cause pt= discomfort, anxiety, coughing, bronchospasm, hemmorrhage, AW edema, ulceration of the mucosal wall (atelectasis), arrythmias, tachycardia, bradycardia

What is the #1 most common hazard of suctioning?


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