RESP 210 quiz 1 study gude

formulas to memorize

• TCT

• VE

• RR

• VT

• Ti

• Flow

• Male predicted VE

• Female predicted VE

• Compliance

• Volume lost

• TCT = Ti + Te

  • TCT = 60 / RR

• VE = RR × VT

• RR = VE / VT

• VT = Flow × Ti

• Ti = VT / Flow

• Flow = VT / Ti

• Male predicted VE = 4 × BSA

• Female predicted VE = 3.5 × BSA

• Compliance = ΔV / ΔP

• Volume lost = PIP × CT

values to memorize

Item	Memorize
MIP	0 to -20 cmH2O critical
MEP	< 40 cmH2O critical
VC	< 10-15 mL/kg IBW critical
RR	> 35/min critical
FEV1	< 10 mL/kg IBW critical
PEF	75-100 L/min critical
VD/VT	> 0.60 critical
ARF II pH	< 7.25
ARF II PaCO2	55 mmHg and rising
P/F	< 200 critical
PaO2	< 70 on >0.60 FiO2 critical
A-a gradient	> 450 mmHg critical
PaO2/PAO2	< 0.15 critical
Initial VT	6-8 mL/kg IBW
ARDS VT	4-6 mL/kg IBW
Initial FiO2	1.0 / 100%
Initial PEEP	5 cmH2O
Ti	0.8-1.2 sec
I:E	1:2 to 1:4
Male IBW	50 + 2.3(inches over 60)
Female IBW	45.5 + 2.3(inches over 60)
Male predicted MV	4.0 x BSA
Female predicted MV	3.5 x BSA
VT	Flow x Ti
TCT	Ti + Te
MV	RR x VT
Volume lost	PIP x CT
ETT mechanical dead space	~1 mL/kg IBW
VC -> PC	Pplat OR PIP - 5
PTA	PIP - Pplat
Pressure conversion	1 mmHg = 1.36 cmH2O
Atmosphere	760 mmHg
Acute CO2 rule	+10 PaCO2 -> +1 HCO3-

what is NIV

• mechanical ventilation without an invasive artificial airway such as an endotracheal tube.

• can be an alternative to intubation in an appropriate patient. It is particularly useful in hypercapnic COPD.

• For cardiogenic pulmonary edema (CPE), CPAP is usually preferred. Do not delay intubation if the patient is failing.

what is the main goal of NIV

• Provide ventilatory support while avoiding intubation and invasive mechanical ventilation.

what are the main benefits for NIV?

• ↓ need for intubation.

• ↓ ventilator-associated pneumonia.

• ↓ ICU/hospital stay.

• Requires less sedation.

• Improves patient comfort.

• Preserves normal airway defenses.

Indications for NIV

• Acute COPD exacerbation with hypercapnia/respiratory acidosis.

• Acute-on-chronic respiratory failure.

• Cardiogenic pulmonary edema.

• Selected patients with acute hypoxemic respiratory failure.

signs for NIV

• Increased respiratory rate.

• Moderate/severe dyspnea.

• Accessory muscle use.

• Paradoxical breathing.

• pH < 7.35 with with PaCO2 >= 45 mmHg

• PaO2/FiO2 < 200.

on NIV patient should be able to

• Protect their airway.

• Cooperate with therapy.

• Manage secretions.

• Maintain adequate spontaneous breathing.

Absolute contraindications for NIV

• Respiratory arrest.

• Excessive/copious secretions.

• Cardiac arrest.

• Hemodynamic instability.

• High aspiration risk.

• Facial/head trauma preventing mask fit.

• Uncooperative/confused patient.

• Unable to protect airway.

Relative contraindications for NIV

• Copious or viscous secretions

• Extreme obesity

• Some nasopharyngeal abnormalities

Mechanism of action for NIV IPAP

• Supports inspiration.

• Improves ventilation.

• ↑ VT.

• ↓ PaCO2.

• ↓ work of breathing.

Mechanism of action for NIV EPAP

• Helps keep alveoli open.

• Improves oxygenation.

what are signs NIV is failing

• Respiratory arrest

• RR > 35

• Severe dyspnea with accessory muscles/paradoxical breathing

• Life-threatening hypoxemia: PaO2 < 40 mmHg or P/F < 200

• Severe acidosis: pH < 7.25 with hypercapnia (PaCO2 > 60 mmHg)

what is pressure support

IPAP − EPAP

3 physiological objectives for mechanical ventilation

1. Support/manipulate pulmonary gas exchange.

• Improve ventilation.

• Improve oxygenation.

2. Increase lung volume.

• Prevent/treat atelectasis.

• Restore/maintain FRC.

3. Reduce work of breathing.

• for mechanical ventilation, what do we want to reverse (clinical objectives)

reverse

• acute respiratory failure (ARF)

• respiratory distress

• respiratory muscle fatigue

• Hypoxemia

• Prevent or reverse atelectasis

• Permit sedation or paralysis (or both)

• maintain FRC

for mechanical ventilation, what do we want to reduce (clinical objectives)

• systemic or myocardial oxygen consumption

• mortality and complications associated with mechanical ventilation

• how can we recognize respiratory distress

• responsiveness/LOC

• cyanosis, pallor, diaphoresis, anxiety and nasal flaring

  • Tachycardia, hypotension and arrhythmias

• Tripoding, accessory muscle use and retractions

• breath sounds

Clinical decision: Does the patient need increased FiO2, NIV, or intubation/mechanical ventilation?

what are the 3 main reasons to initiate mechanical ventilation

1. ARF I = hypoxemic respiratory failure.

• PaO2 < 70 on FiO2 > 0.60

• P(A-a)O2 > 450 mmHG when on O2

• PaO2/PAO2 < 0.15

• P/F ratio < 200

2. ARF II = hypercapnic respiratory failure.

• pH < 7.25

• PaCO2 > 55 mmHg and rising

• VD/VT > 0.60

• Main causes:

  • CNS problem

  • Neuromuscular weakness

  • ↑ WOB

3. Inability to protect the airway.

• Altered mental status

• Aspiration risk

• Trauma/burns

• Unable to handle secretions

4. impending respiratory failure.

what are critical values for oxygenation?

Critical oxygenation value	Threshold
P/F ratio; PaO2 / FiO2	< 200
PaO2/PAO2	< 0.15
A-a gradient	> 450 mmHg
PaO2	< 70 mmHg on ≥ on 0.60 FiO2

Be able to use/interpret MIP/MEP/VC values in case studies for progressive neuromuscular diseases like myasthenia gravis or Guillain Barre and determine patient care choices

In myasthenia gravis, Guillain-Barre and other neuromuscular diseases, watch the TREND in MIP, VC, PaCO2 and clinical status.

Example of deterioration: VC 1.7 L -> 1.2 L; MIP -32 -> -25 cmH2O; PaCO2 52 -> 58 mmHg.

Remember: MIP moving toward zero means inspiratory muscle strength is getting worse.

what is MIP? Also called NIF

MIP, MEP, VC, RR, FEV1, PEF: be able to calculate VC, know the critical values for all of these acronyms, understand what each acronym tells you about the patient, be able to use that data to determine if the patient should have mechanical ventilation initiated

• Inspiratory muscle strength.

• Normal = −50 to −100 cmH2O

• Critical = 0 to −20 cmH2O

• More negative = stronger.

  • Example: -60 is stronger than -15

• Closer to zero = weaker.

what is MEP?

• Expiratory muscle strength / cough effectiveness (strength)

• Critical = < 40 cmH2O

what is VC?

• ventilatory reserve; Maximum volume exhaled after a maximal inspiration

• Normal = 65–75 mL/kg IBW

• Critical = < 10–15 mL/kg IBW

how do you calculate VC

• measured VC (mL) / IBW (kg) = VC in mL/kg

what is VT?

• tidal volume: the amount of air that moves in and out of the lungs with each normal breath

• Normal = 5–8 mL/kg

• Critical = < 5 mL/kg

what is RR?

• respiratory rate, respiratory demand/WOB

• Normal = 12–20/min

• Critical = > 35/min

what is FEV1?

• Forced expiratory volume in 1 sec

• airflow obstruction; volume of air exhaled in the first second

• Normal = 50–60 mL/kg IBW

• Critical = < 10 mL/kg IBW

what is PEF?

Peak Expiratory Flow, a medical measurement of how fast you can breathe air out of your lungsairflow obstruction; maximum speed of exhaled air

Normal = 350–600 L/min

Critical = 75–100 L/min

what equation tells you how well patient can move air out

PEF + FEV1

what is the equation for dead space?

VD = (VD/VT) x VT

VD/VT tells us how much of each tidal volume does NOT participate in gas exchange.

• Critical: VD/VT > 0.60

example equation for dead space

Example:

VD/VT = 0.30 and VT = 500 mL -> VD = 150 mL. Alveolar volume = 500 - 150 = 350 mL

What is the estimated mechanical dead space volume for intubated patients with an endotracheal tube?

Approximately $1\,\text{mL/kg}$ of Ideal Body Weight (IBW).

when interpreting an ABG, include:

• Acute, chronic, or acute-on-chronic.

• Compensated, uncompensated, or partially compensated.

  • uncompensated

    • 1 normal value between co2 & hco3

  • partially compensated

    • all abnormal values

  • fully compensated

    • pH is normal

• Respiratory, metabolic, or mixed.

• Acidosis or alkalosis.

  • pH >7.45 is alkalosis

  • pH <7.35 is acidosis

• Degree of hypoxemia

  • 80-100 mmHg normal

  • 60-79 mmHg mild

  • 40-59 mmHg moderate

  • <40 mmHg severe

what is the rule for acute respiratory acidosis to see HCO3 change

• For every 10 mmHg increase in PaCO2 above 40:

  • HCO3 ↑ approximately 1 mEq/L.

PaCO2	Expected acute HCO3-
40	24
50	25
60	26
70	27
80	28

what are initial volume control settings for ventilators

• VT

• Ti

• FiO2

• I:E

• RR

• PEEP

Setting	Initial value
VT	6-8 mL/kg IBW
Ti	0.8-1.2 sec
FiO2	1.0 (100%), then titrate
I:E	1:2 to 1:4
RR if BSA unavailable	12-20/min
PEEP	5 cmH2O (per test outline)

what are some considerations for ARDS/ lung protective strategies in relation to the ventilator

• VT may be 4–6 mL/kg IBW.

• Keep Pplat < 30 cmH2O.

Permissive hypercapnia may be accepted to protect the lungs

• higher PaCO2 may be accepted (permissive hypercapnia) to limit ventilator-induced lung injury

• Patient-specific oxygenation goals from the slides: ARDS PaO2 55-80 mmHg; COPD SpO2 88-92%; head trauma PaO2 >= 100 mmHg.

How is predicted minute ventilation calculated from BSA for male vs female patients?

Male predicted minute ventilation = 4.0 x BSA.

Female predicted minute ventilation = 3.5 x BSA.

Initial RR = predicted minute ventilation / VT (make sure units match).

what is minute ventilation?

• VE = VT × RR

the total volume of air inhaled or exhaled by the lungs in one minute

• Normal: Approximately 5–6 L/min.

• High VE without increased metabolic demand can indicate:

  • ↑ WOB

  • Patient may not be able to sustain ventilation.

How do we calculate VE minute ventilation for an adjustment for temperate

Increase minute ventilation 10% for every 1°C above 37°C.

How do we calculate VE minute ventilation for an adjustment metabolic acidosis

Increase predicted minute ventilation by 20%.

how do we calculate respiratory rate

• RR = VE / VT

• normal is 12-20

Calculate IBW for VT

IBW:

Males: 50kg + (2.3 x Ht - 60)

Females: 45.5kg + (2.3 x Ht - 60)

• Normal starting VT = 6–8 mL/kg IBW.

• 6’0 = 72 inches

  • multiple by 12

What are the standard initial ventilator settings for PEEP and FiO2?

Initial PEEP is typically $5\,\text{cmH}_2\text{O}$ and $\text{FiO}_2$ is $100\%$ (or matched to previous baseline).

What formula is used to calculate tidal volume lost due to circuit compliance?

• tubing compliance tells us how much volume is lost in the ventilator circuit as pressure ↑.

• formula = PIP × CT

  • where PIP is peak inspiratory pressure and CT is tubing compliance factor.

    • Formula: CT = Volume lost / Pressure

Example equation for lung compliance

Example: PIP 30 cmH2O x CT 1.5 mL/cmH2O = 45 mL lost. If set VT is 500 mL, delivered VT = 455 mL.

Tubing compliance tells us how much volume is lost in the ventilator circuit as pressure increases.

• Formula: CT = Volume lost / Pressure

what are some components for mechanical dead space in relation to the ventilator

this is volume added by equipment that does not participate in gas exchange.

• With ETT: Approximately 1 mL/kg IBW

• Without ETT: Approximately 1 mL/lb IBW

Equipment that adds _____:

• HME = approximately 20–90 mL.

• Corrugated tubing = approximately 50 mL per 6 inches.

what is the difference between VT, flow, and Ti

• VT = how much gas is delivered.

• Flow = how FAST gas is delivered.

• Ti = how LONG gas is delivered.

what are the equations for VT, flow, and Ti

• VT = Flow × Ti

• Ti = VT/Flow

• Flow = VT/Ti

Be careful to convert mL to L and L/min to L/sec when necessary.

What is the formula relating tidal volume, inspiratory flow rate, and inspiratory time?

$V_t = \text{Flow} \times T_i$, where flow is in $\text{L/s}$ (or $\frac{\text{Flow (L/min)}}{60}$).

equation for and inspiratory/expiratory timing?

• TCT = Ti + Te

  • TCT can also be found from 60 / RR.

• Te = TCT - Ti.

equation for I:E

• I:E = Ti/Ti : Te/Ti.

example equation to find I:E

RR 15 -> TCT 4 sec. If Ti = 1 sec, Te = 3 sec 

I:E = 1:3

what are some differences between fast flow and short flow

Faster flow	Slower flow
Shorter Ti	Longer Ti
More expiratory time	Less expiratory time
Higher resistive pressure / PIP	Lower resistive pressure / PIP
Potentially poorer gas distribution	Potentially better gas distribution
More turbulent / less laminar	Can increase mean airway pressure

do COPD & asthmatic patients need more time to inhale or exhale

Select appropriate Ti for asthma/COPD patients in VC (constant flow rate) - obstructive disease profile with air trapping issues

• These patients need TIME TO EXHALE.

• Often increase inspiratory flow -> shorten Ti -> lengthen Te -> reduce air trapping/auto-PEEP.

• Goal:

  • Shorter Ti.

  • Longer Te.

  • Often increase inspiratory flow.

• allows complete exhalation and helps prevent air trapping or auto-PEEP.

How does increasing inspiratory flow rate in constant flow VC mode affect Ti, PIP, turbulence, and RAW?

Increasing flow rate decreases $T_i$, increases Peak Inspiratory Pressure (PIP), increases gas turbulence, increases Airway Resistance (RAW), and alters gas distribution.

What are the four inspiratory flow patterns, and how do constant and decelerating patterns compare?

1. Constant (Square),

• Also called square or rectangular.

• Flow stays constant.

• Commonly used.

• Appropriate for many patients with normal lungs.

• may reduce mean airway pressure.

2. Decelerating/ descending (Ramp)

• Highest flow occurs at the beginning of inspiration.

• Flow decreases throughout inspiration.

• Occurs naturally in pressure ventilation.

• may decrease WOB

• improve gas distribution/oxygenation

• reduce PIP

3.Accelerating/ ascending

4.Sine wave.

How is the initial Pressure Control (PC) level selected when converting a patient from Volume Control (VC)?

Be able to convert from VC mode to PC with a PIP and/or Plat value -- remember to convert from VC to PC, either select the plateau pressure as your PC or you can select PIP - 5 cmH2O. Either choice is OK for initial PC setting

Set PC equal to either the:

• $$\text{PIP} - 5\,\text{cmH}_2\text{O}$$

• use Plateau Pressure ($P_{\text{plat}}$) from inspiratory hold

Then: Adjust pressure until the desired VT is achieved.

why would we use PC pressure control

• Descending inspiratory flow.

• ↓ PIP.

• May improve gas distribution.

• May improve oxygenation.

• May improve patient comfort/synchrony.

• May ↓ WOB.

Which primary mechanical and patient factors determine tidal volume in Pressure Control mode?

Understand the factors that impact Vt in PC modes

• VT is VARIABLE.

• VT depends on:

  • Pressure setting.

  • Compliance.

  • Airway resistance.

  • Inspiratory time.

  • Patient effort.

if there is a ↓ compliance in PC, what happens to VT

↓ VT .

if airway resistance ↑ in PC

VT may ↓.

if Ti ↑ in PC

VT may ↑

How do you calculate a new Pressure Control setting to achieve a target tidal volume?

Using the formula compliance = change in volume / change in pressure, change the PC setting to meet a volume goal.

Compliance = change in volume / change in pressure.

example equation 1 for a new PC

PC 10 cmH2O produces VT 250 mL.

Desired VT 400 mL

Example:

Compliance = 250/10 = 25 mL/cmH2O.

400/25 = PC 16 cmH2O.

example equation for a new PC

if patient is getting 250 ml in PC mode and you want to get 500 ml in PC mode and PC setting is 12 cmH2O

Compliance = 250/12 = 20.83 mL/cmH2O.

500/20.83 = PC 16 cmH2O.

your new PC setting would be 24 cmH2O to obtain the higher Vt

example on how to calculate a new Pressure Control setting to achieve a target tidal volume?

Example:

PC = 10 cmH2O

VT = 250 mL

Compliance:

250 / 10 = 25 mL/cmH2O

Desired VT = 400 mL

400 / 25 = 16 cmH2O

New PC = 16 cmH2O

what happens during quiet inspiration

• Active

• Diaphragm contracts.

• Diaphragm moves downward.

• Chest expands.

• Air enters the lungs.

what happens during quiet expiration

• Passive.

• Requires no muscular work.

• Diaphragm relaxes.

• Chest recoils.

• Air leaves the lungs.

what is Boyle’s law

• Pressure and volume are inversely related.

  • thoracic/lung volume increases → alveolar pressure decreases.

    • air flows in

  • thoracic/lung volume decreases → alveolar pressure increases.

    • air flows out

how does Boyle’s law relate to volume and pressures within lungs during breathing

During inspiration:

• Thoracic volume increases.

• Alveolar pressure decreases.

• Air flows into the lungs.

During expiration:

• Thoracic volume decreases.

• Alveolar pressure increases.

• Air flows out.

what is internal respiration

• O2 moves from systemic blood into the cells.

• Cells use O2 to produce energy.

• CO2 is produced as a by-product of metabolism.

what is external respiration

• Exchange of O2 and CO2 between the alveoli and pulmonary capillaries.

what muscles are used for inspiration when not intubated

• Scalenes.

• Sternocleidomastoid.

• Pectoralis major/minor.

• Trapezius.

what muscles are used for expiration when not intubated

• Rectus abdominis.

• Transverse abdominis.

• External oblique.

• Internal oblique.

• Latissimus dorsi.

how do youconvert mmHg to cmH₂O and cmH₂O to mmHg using conversion values - know that 1 atmosphere = 760 mmHg

• 1 mmHg = 1.36 cmH2O

• 1 atmosphere = 760 mmHg = 1034 cmH2O

mmHg -> cmH2O: multiply by 1.36.

cmH2O -> mmHg: divide by 1.36.

Reference only:

1 kPa = 7.5 mmHg

1 Torr = 1 mmHg

In mechanical ventilation settings, atmospheric pressure is assumed to be

"zero" (because P_AWO = 0) and any pressure added is in cmH₂O above zero

At rest: Alveolar pressure = atmospheric pressure = 0

Therefore: No pressure gradient. No airflow.

define PIP and Pplat

• Highest pressure reached during inspiration.

• Includes pressure needed to overcome:

  • Airway resistance.

  • Elastic resistance of the lungs/chest wall.

define Pplat

• Measured during an inspiratory hold.

• There is NO gas flow. gas flow is zero

• No flow = no resistive pressure.

• is the approximate alveolar pressure.

• Reflects respiratory-system compliance

what is the difference between PIP and PPLAT

• PIP = AIRWAYS + LUNGS

• Pplat = LUNGS

During inspiration:

• Gas is flowing.

• PIP includes airway resistance + elastic pressure.

During an inspiratory hold:

• Flow stops.

• Airway resistance no longer contributes.

• Pplat reflects the pressure needed to hold the volume in the alveoli.

what is the equation for pressure used to overcome airway resistance

• PIP − Pplat (transairway pressure)

• example:

  • PIP 35 - Pplat 25 = PTA 10 cmH2O.

what is transairway pressure

the pressure difference between the airway opening (the mouth or nose) and the alveoli (air sacs in the lungs)

the pressure required to overcome airway resistance

Pta=Pao - Palv

Key Components

• Pta: Transairway pressure

• Pao: Pressure at the airway opening (mouth / airway entry)

• Palv: Alveolar pressure