Apex Respiratory Monitors and Equipment practice questions and flashcards

Resistance

The force that acts opposite the relative motion of object

At what cm/H2O does the risk of barotrauma increase?

35 cm/H2O

If barotrauma exists,

Reduce plateau pressure by reducing TV, inspiratory flow, and PEEP.

Sedation could also be used

Compliance

Ability of the lungs to stretch and expand

Also the change in volume for a given change in pressure

Static Compliance

Static= Not moving

Assesses pressure required to keep the lung inflated to a given volume when there is no air movement

Pressure required to keep the lung inflated to a given volume is a function of the tendency of the lung/chest to collapse (no airflow = no resistance to overcome)

Dynamic Compliance

• Dynamic= movement

• Dynamic compliance is the lung/ chest wall during movement

• Pressure required to inflate the lung to a given volume is a function of airway resistance and tendency of the lung/chest to collapse

Formula for Dynamic Compliance

Tidal volume/ (Peak Inspiratory Pressure- PEEP)

What is dynamic compliance impacted by?

Airway resistance and the tendency of the lung/chest to collapse due to the elasticity of lung tissue and the chest wall.

Peak inspiratory pressure

The maximum pressure in the patients small airways and alveolli during when target TV is delivered.

Plateau Pressure

Pressure in the small airways and alveoli after the target tidal volume is achieved

Reflects elastic recoil of the lungs and thorax during inspiratory pause (no gas moving in or out of the lungs)

How does increased resistance present?

Increased PIP with a normal Plateau pressure'

Ex. Kinked endotracheal tube and bronchospasm

How does decreased pulmonary compliance present?

Increased PIP and Plateau pressure

Ex. Endobronchial intubation and pulmonary edema

What is the formula to calculate airway resistance?

[P(airway) - P(alveolar)] / Gas Flow Rate

What is the formula for airway compliance?

delta of V/Delta of P

What factors influence compliance?

Muscle tone

Degree of lung inflation

Alveolar surface tension

Amount of interstitial lung water

Pulmonary fibrosis

What is the formula to calculate dynamic compliance?

Tidal volume / (peak inspiratory pressure - PEEP)

What is the formula for calculating static compliance?

Tidal volume / (Plateau pressure - PEEP)

What is the normal range for adult static compliance?

35-100 cm/H2O

What is the normal range for pediatric static compliance?

>15 cm/H2O

What are complications of elevated plateau pressure?

Ventilator associated lung injury

Pneumothorax

Pneumomediastinum

Subcutaneous emphysema

What does it mean when there is an increase in PIP with no change in plateau pressure?

Resistance has increased

Inspiratory flow rate has increased

What does it mean when PIP increases and plateau pressure increases?

Total compliance has decreased (elastic pressure has increased)

Tidal volume has increased

What are examples of increased resistance?

Kinked ETT

Endotracheal tube cuff herniation

Bronchospasm

Bronchial secretions

Compression of the airway

Foreign body aspiration

What are examples of decreased compliance?

Endobronchial intubation

Pulmonary edema

Pleural effusion

Tension pneumothorax

Atelectasis

Chest wall edema

Abdominal insufflation

Ascites

Trendelenburg

Inadequate muscle relaxation

What type of pulmonary compliance is a function of both airway resistance and the elasticity of the chest wall?

Dynamic compliance

What type of pulmonary compliance is a function of the elasticity of the chest wall only?

Static compliance

What does capnography measure?

End tidal CO2 concentration over time

What can capnography assess?

Continuous assessment of metabolism, circulation, ventilation

Provides insight to equipment related problems like airway obstruction and rebreathing

What does an increased alpha signal suggest?

Expiratory airway obstruction

What does an increased beta angle suggest?

Rebreathing due to a faulty inspiratory valve

What are the two methods of carbon dioxide analysis?

Mainstream (in-line)

Side stream (diverting)

What is CO2 the final product of?

Aerobic metabolism

How does CO2 move from the tissue and enter venous circulation?

By diffusion

How does the rate of CO2 transfer toward the lungs get affected?

By cardiac output

In the lungs how does CO2 diffuse across the alveolocapillary membrane?

By following a concentration gradient

Once CO2 is in the alveolus, how is CO2 eliminated from the body?

By ventilation

What does phase one of the capnography waveform represent?

(A-B): Exhalation of an atomic dead space

What does phase 2 of the capnography waveform represent?

(B-C): exhalation of the anatomic dead space and alveolar gas

What does phase 3 of the capnography waveform represent?

(C-D): exhalation of alveolar gas

What does phase 4 of the capnography waveform represent?

(D-E): inspiration of fresh gas that does not contain CO2

What is the normal angle for Alpha Angle?

100-110 degrees

Where is the alpha angle measured?

Point C

What does an increased alpha angle signify?

Expiratory airflow obstruction like COPD, bronchospasm, kinked endotracheal tube

Where is the beta angle measured?

Point D

What causes an increased beta angle?

Rebreathing specific to a faulty inspiratory valve

When will a beta angle appear normal despite rebreathing?

Exhausted CO2 absorbent

What are the pros to a mainstream CO2 analyzer?

Faster response time

Doesn't require a water tap/pumping mechanism

What are the cons to a mainstream CO2 analyzer?

Increases apparatus dead space

Adds extra weight

How does a side stream CO2 analyzer work?

Pumping mechanism continuously aspirates gas sample from the breathing circuit, causing a slower response time and requires a water trap to prevent contamination of device

Which method of CO2 analysis will take longer to reveal a circuit disconnect?

Sidestream (diverting) because it has a longer response time

The sample must travel through long tubing before it reaches the monitor

What are the characteristics of an airflow obstruction on capnography?

Prolonged upstroke with an increased alpha angle

COPD, bronchospasm, kinked ETT

What creates oscillations on a cardiac oscillation waveform on capnography?

The heart beating against the lungs, more commonly occurring in children due to close proximity of the heart to the lungs

What causes the Curare Cleft waveform on capnography?

Spontaneous breaths during inspiration

Inadequate muscle relaxation or inadequate muscle relaxant reversal

What causes a low EtCO2 waveform on capnography?

Hyperventilation - light anesthesia, metabolic acidosis

decreased CO2 production - hypothermia

increased alveolar dead space - hypotension, pulmonary embolism

What causes an elevated EtCO2 with a normal baseline on capnography?

Increased CO2 production - MH, sepsis, fever, hyperthyroidism

Decreased alveolar ventilation - hypoventilation, narcotics

What does it mean when capnography presents with no return to baseline?

Rebreathing! Due to exhausted CO2 absorbent, incompetent expiratory valve, hole in inner tube of Bain system, inadequate FGF with Mapleson circuit or rebreathing under the drapes in a non-intubated patient

How will an incompetent inspiratory valve present on capnography?

Widened beta angle (decreased slope during inspiratory phase)

What causes the peak at the end of plateau with a leak in sample line waveform on capnography?

Positive pressure during inhalation pushing CO2 rich gas through the sample line

What do the first and second peaks represent in biphasic expiratory plateaus on capnography?

First peak: alveolar gas from the transplanted lung with normal time constant

Second Peak: alveolar gas from the diseased lung with a longer time constant due to air trapping

What causes increased EtCO2?

Increased CO2 production and delivery to lungs

Decreased alveolar ventilation

Equipment malfunction

What causes decreased EtCO2?

Decreased CO2 production and delivery to lungs

Increased alveolar ventilation

Equipment malfunction

For EtCO2 to be detected, what requirements must be met?

Carbon dioxide must be produced during metabolism

Must be adequate pulmonary blood flow to deliver CO2 to the lungs for elimination

Must be an adequate ventilation to transport CO2 to breathing circuit

Must be intact sampling system

What are examples of increased CO2 production and delivery to the lungs resulting in increased EtCO2?

Increased BMR

MH

Thyrotoxicosis

Fever

Seizures

Sepsis

Laparoscopy

Tourniquet or vascular clamp removal

Sodium bicarbonate administration

Shivering

Increased muscle tone - after NMB reversal

Medication side effect

Which law is pulse oximetry based on?

Beer-Lambert Law

What are the examples of decreased alveolar ventilation resulting in increased EtCO2?

Hypoventilation

CNS depression

Residual neuromuscular blockade

COPD

High spinal anesthesia

Neuromuscular disease

Metabolic alkalosis (if spontaneous ventilation)

Medication side effect

What are examples of equipment malfunction resulting in increased EtCO2?

Rebreathing

CO2 absorbent exhaustion

Unidirectional valve malfunction

Leak in breathing circuit

Increased apparatus dead space

What are examples of decreased CO2 production and delivery to the lungs resulting in decreased EtCO2?

Decreased BMR

Increased anesthetic depth

Hypothermia

Decreased pulmonary blood flow

Decreased cardiac output

Hypotension

Pulmonary embolus

V/Q mismatch

Medication side effect

Pain/anxiety (if breathing spontaneously)

What are examples of increased alveolar ventilation resulting in decreased EtCO2?

Hyperventilation

Inadequate anesthesia

Metabolic acidosis (if spontaneous ventilation)

Medication side effect

What are examples of equipment malfunction resulting in decreased EtCO2?

Ventilator disconnect

Esophageal intubation

Poor seal with ETT or LMA

Sample line leak

Airway obstruction

Apnea

At what nm does oxygenated hemoglobin absorb light?

940 nm - near infra red light

At what nm does deoxygenated hemoglobin absorb light?

660 nm - red light

What is the Beer-Lambert Law?

Relates the intensity of light transmitted through a solution (blood) and the concentration of the solute (hemoglobin) within a solution

At the trough of the pulse waveform, what is there a greater amount of in the tissue sample?

Venous blood

At the peak of the pulse waveform, what is there a greater amount of in the tissue sample?

Arterial blood

What is the formula for calculating SpO2?

Oxygenated Hgb / (oxygenated Hgb + deoxygenated Hgb) x 100%

List the pulse oxymetry sites from most to least responsive

Fast - ear, nose, tongue, esophagus, forehead

Middle - finger

Slow - toe

What wavelength of light is preferentially absorbed in venous blood?

Red light (660 nm) is preferentially absorbed by deoxyhemoglobin (higher in venous blood).

What wavelength of light is preferentially absorbed in arterial blood?

Near-infrared light (940 nm) is preferentially absorbed by oxyhemoglobin ( higher in arterial blood).

The pulse oximeter reads 80%. You estimate the PaO2 is approximately:

50 mmHg

The pulse oximeter reads 70%. You estimate the PaO2 is approximately:

40 mmHg

The pulse oximeter reads 90%. You estimate the PaO2 is approximately:

60 mmHg

What does a left shift signify on a oxyhemoglobin dissociation curve?

Increased affinity for O2 (left = love), occurs in the lungs

What does a right shift signify on a oxyhemoglobin dissociation curve?

Decreased affinity for O2 (right = release)

What are some causes of a left shift in the oxyhemoglobin dissociation curve?

Decreased temperature

Decreased 2,3-DPG

Decreased CO2

Decreased H+

Increased pH

Increased HgbMet

Increased HgbCO

Increased HgbF

What are some causes of a right shift in the oxyhemoglobin dissociation curve?

Increased temperate

Increased 2,3_DPG

increased CO2

Increased H+

Decreased pH

What are methods to improve SpO2 signal?

Warm extremity

Protect extremity from ambient light

Apply a vasodilating cream

Administer an arterial vasodilator (extreme)

Place a digital block (extreme)

The pulse oximeter is a useful monitor of:

Vascular compression

The pulse oximeter is a noninvasive monitor of:

Hgb saturation

HR

fluid responsiveness(PPV)

perfusion

Where does the innominate artery (1st branch of aortic arch, 3rd branch off aorta) supply blood?

Right arm

Head

Neck

What is the formula for calculating alveolar oxygen?

FiO2 x (Pb - PH2O) - (PaCO2/RQ)

The pulse oximeter is not a good monitor of:

Anemia

Ventilation

Bronchial intubation

What can affect the reliability of the pulse oximeter?

Dysfunctional hemoglobin (methemoglobin, carboxyhemoglobin)

Decreased perfusion

Altered optical characteristics (dyes, nail polish [blue, green, black]

Non-pulsatile flow

Motion artifact

How does methemoglobin falsely estimate SpO2?

Falsely underestimates SpO2 if O2 is greater than 85%

Falsely overestimates SpO2 if O2 is <85%

How does carboxyhemoglobin falsely estimate SpO2?

Reads the sum of CO-Hgb and Oxy-Hgb = overestimates SpO2

What does not affect the reliability of the pulse oximeter?

Hemoglobin S

Hemoglobin F

Jaundice

Fluorescein

Polycythemia

Acrylic Fingernails

How does mass spectrometry analyze exhaled gas?

Bombards a gas sample with electrons creating ion fragments

How does Raman Scatter Spectrometry analyze exhaled gas?

Uses a high power argon laser to produce photons, which in turn collide with the gas molecules

How do Piezoelectric crystals analyze exhaled gas?

Detects inspired, expired and breath-to-breath changes of a particular gas by incorporating a lipid layer on the crystal

How does infrared absorption analyzed exhaled gas?

Different gases absorb different wavelengths of infrared light, each having a "fingerprint".

Diatomic molecules don't absorb IR light

During anesthetic induction the SpO2 fails to display on the monitor. the circulating nurse notes that the patient is wearing green nail polish. What is the most appropriate intervention at this time?

Rotate the probe 90 degrees on the finger