Adult Respiratory Flashcards
(92 cards)
Steps to interpreting ABGS
How to interpret if it’s compensated, partially compensated, uncompensated
- Determine if the problem is acidosis or alkalosis. Look at the pH. If it is below 7.4 think acidosis, if it is higher than 7.4 think alkalosis.
- Determine if the problem is respiratory or metabolic in origin. PCO2 (35-45 mmHg) ,an increased PCO2 indicates acidosis, and a decreased pCO2
indicates alkalosis. HCO3 (22-26 mmHg), a decreased HCO3 indicates acidosis and an increased
HCO3 indicate alkalosis - To determine partially compensated – all 3 numbers are abnormal.
- Acute uncompensated (aka uncompensated) pH abnormal and only one parameter is
abnormal. - Fully compensated-ph normal C02 and HC03 abnormal
NOTE: Look at Oxygen First! If patient is Hypoxic – This Is The Priority!
How to do an Allen’s test
- Rest the patient’s arm on the mattress or bedside stand and support his wrist with a rolled towel. Tell him to clench his fist. Using your index and middle fingers, press on the radial and ulnar arteries. Hold this position for a few seconds.
- Without removing your fingers from the patient’s arteries, ask him to unclench his fist and hold his hand in a relaxed position. The palm will be blanched because pressure from your fingers has impaired the normal blood flow.
- Release pressure on the patient’s ulnar artery. If the hand becomes flushed, which indicates blood filling the vessels, you can safely proceed with the radial artery puncture. If the hand does not flush, select another site for the puncture.
Mr. Thomas is a 65-year-old man with pneumonia. He is admitted with dyspnea, fever and chills. His blood gas is:
pH = 7.28
PaCO2 = 56
HCO3- = 25
PaO2 = 70%
What is your interpretation?
Mr. Thomas has uncompensated respiratory acidosis with hypoxemia as a result of his pneumonia.
This is due to inadequate ventilation and perfusion.
What are some causes of respiratory acidosis?
Severe respiratory infections (e.g., pneumonia) can cause respiratory acidosis. Other causes may include CNS depression, pneumothorax, pulmonary edema, pulmonary embolus, bronchial obstruction, etc.
Mr. Thomas is a 65-year-old man with pneumonia. He is admitted with dyspnea, fever and chills. His blood gas is:
pH = 7.28
PaCO2 = 56
HCO3- = 25
PaO2 = 70%
He is is respiratory acidosis with hypoxemia as a result of his pneumonia.This is due to inadequate ventilation and perfusion.
Treatment?
- Improve ventilation and oxygenation – supplemental O2, CPAP, BiPAP, or mechanical ventilation
- Treat underlying cause – antibiotics for infection
- Bronchodilators
- Removal of secretions – chest physiotherapy, suctioning
Ms. Thompson is a 21-year-old college student. She has a history of Crohn’s Disease and is complaining of a four-day history of bloody, watery diarrhea. A blood gas is obtained to assess her acid-base balance:
pH = 7.28
Co2 = 43
P02 = 88
Hco3 = 20
Sao2 = 96%
What is your interpretation?
Ms. Thompson has uncompensated metabolic acidosis due to excessive bicarbonate loss from her diarrhea.
Loss of alkali secondary to severe diarrhea or intestinal malabsorption.
What are causes of metabolic acidosis?
Loss of alkali secondary to severe diarrhea or intestinal malabsorption.
Other causes include those which creates an accumulation of acid including renal failure, DKA, anaerobic metabolism, starvation and salicylate intoxication.
Ms. Thompson is a 21-year-old college student. She has a history of Crohn’s Disease and is complaining of a four-day history of bloody, watery diarrhea. A blood gas is obtained to assess her acid-base balance:
pH = 7.28
Co2 = 43
P02 = 88
Hco3 = 20
Sao2 = 96%
Ms. Thompson has uncompensated metabolic acidosis due to excessive bicarbonate loss from her diarrhea. What is the treatment?
- Treatment with antidiarrheals and bowel rest.
- IV fluids as necessary
- Monitor potassium levels ( range 3.5 – 5.0 mEq/L) (could become hypokalemic due to diarrhea)
- Not necessary to administer bicarbonate at this time
Mr. Higgins is a 64-year-old man brought to the ED by his sister after a 3-week history of worsening confusion, difficulty walking, lack of food intake, and vomiting. He has a long-term history of alcohol abuse, PTSD, and GERD. She reports that his diet is comprised only of Pepsi and alcohol. He has also been taking four spoonfuls of baking soda every day to alleviate dyspepsia. A blood gas is obtained:
pH = 7.64
CO2 = 58
HCO3- = 62
PO2 = 95
SaO2 = 95%
What is your interpretation?
Mr. Higgins has partially compensated metabolic alkalosis due to loss of acid (excessive vomiting) and excessive bicarbonate ingestion (baking soda).
His body is compensating by retaining CO2, most likely from hypoventilation.
He has signs and symptoms which include lethargy, weakness, disorientation and nausea/vomiting.
What are causes of metabolic alkalosis?
Loss of acid (excessive vomiting)
Excessive bicarbonate ingestion (baking soda)
Other causes include excessive ingestion of antacids, administration of diuretics and electrolyte imbalances (hypokalemia and hypochloremia).
Mr. Higgins is a 64-year-old man brought to the ED by his sister after a 3-week history of worsening confusion, difficulty walking, lack of food intake, and vomiting. He has a long-term history of alcohol abuse, PTSD, and GERD. She reports that his diet is comprised only of Pepsi and alcohol. He has also been taking four spoonfuls of baking soda every day to alleviate dyspepsia. A blood gas is obtained:
pH = 7.64
CO2 = 58
HCO3- = 62
PO2 = 95
SaO2 = 95%
Mr. Higgins has partially compensated metabolic alkalosis due to loss of acid (excessive vomiting) and excessive bicarbonate ingestion (baking soda).
His body is compensating by retaining CO2, most likely from hypoventilation.
Treatment?
- Treat underlying cause – stop alcohol consumption, anti-emetics, stop baking soda consumption, and administer IV fluids.
- Monitor serum potassium and replace as necessary.
- Medications that increase excretion of bicarbonate (acetazolamide).
- Dialysis for pH greater than 7.55. Dysrhythmias, seizures and coma may result from alterations in depolarization of neuronal and cardiac muscle cells.
How is alkalosis related to hypokalemia?
pH greater than 7.45 is the ECF = alkalosis
Potassium moves to ICF = hypokalemia
Ms. Carr is patient who was admitted for a drug overdose. She is being mechanically ventilated, and a blood gas is obtained to assess her for weaning:
pH = 7.54
CO2 = 19
HCO3- = 16
PO2 = 100
SaO2 = 98%
What is your interpretation?
Ms. Carr has partially compensated respiratory alkalosis from being over-ventilated.
Hyperventilation and overventilation are common causes because it decreases serum CO2 in the lungs and blood because CO2 is eliminated because of the increased rate of respirations.
Causes of respiratory alkalosis
Hyperventilation and overventilation
Other causes include fever, pain, anxiety, hypoxia and lung conditions (early pulmonary edema, pulmonary embolism, pneumonia).
Ms. Carr is patient who was admitted for a drug overdose. She is being mechanically ventilated, and a blood gas is obtained to assess her for weaning:
pH = 7.54
CO2 = 19
HCO3- = 16
PO2 = 100
SaO2 = 98%
Ms. Carr has partially compensated respiratory alkalosis from being over-ventilated. Treatment?
- She cannot be weaned yet so adjustments to the ventilator need to be made (decrease rate or TV?)
- Treat underlying causes. CXR to determine if pneumonia or pulmonary edema is present. Spiral CT to rule out pulmonary embolus.
- May require sedation if breathing over the set rate (pain).
How does negative-pressure ventilation work?
Typically used for what kind of patients?
- During spontaneous breathing, negative pressure is created when the thoracic cavity expands, causing intrapulmonary pressure to drop and air to flow into the
lungs. - The negative-pressure ventilator provides a negative “pulling” pressure on the external chest wall, assisting in ventilation.
- The patient is fitted with a shell that connects to a ventilator. Through use of the ventilator, the air is removed from the area between the patient and the shell, causing negative pressure on the external chest wall.
- Typically used for patients with respiratory disorders usually associated with neuromuscular disorders that impede normal respiratory muscle function. Example: Iron Lung
How does positive-pressure ventilation work? What are the two types?
- Requires the placement of an endotracheal tube (ETT) or tracheostomy tube.
- Provides positive-pressure ventilation by exerting positive pressures on the airways, pushing air into the lungs, causing the alveoli to participate in gas exchange.
- Exhalation occurs passively.
- Positive-pressure ventilation can be delivered by pressure-cycled or volume-cycled ventilators.
- Pressure- cycled ventilators deliver air into the lungs until a preset air pressure is reached.
- Volume -cycled ventilators deliver air into the lungs until a preset volume is reached.
What is a CO2 Detector used for and how is it used?
Confirms ETT placement
It is attached to the end of the ETT. It contains a nontoxic chemical indicator which quickly responds to exhaled CO2 with a color change from purple to yellow.
What is a Laryngeal Mask Airway used for?
If endotracheal intubation is not feasible or has failed, an alternative airway device, such as a laryngeal mask airway (LMA), may be used until a definitive airway can be placed.
Mechanical ventilator setting
Fraction of inspired oxygen (FiO2)
Goal?
- The amount of oxygen received via the ventilator
- Expressed as a fraction or decimal (Example: FiO2 21% = .21)
- Vent can provide 21% - 100% O2 depending on patient needs
- The goal is to maintain a PaO2 above 60 mmHg at
the lowest possible setting
Mechanical ventilator setting
Respiratory rate (f)
Normal rate?
- The number of respirations the patient receives
per minute via the ventilator - Typically, 8 – 12 depending on patient need
- Gradually decreased in a patient who is
breathing spontaneously - When the respiratory rate is assessed, it
includes the numbers of both the vent and
spontaneous breaths
Mechanical ventilator setting
Tidal volume (Vt)
- The amount of preset air that is delivered to the
lungs with each breath - Setting is based on ideal body weight
- Usual setting is 8 to 10 mL/kg (Example: 62.5 kg x
8mL = 500 Vt) - Adjustments may be made according to ABG results
- Lower Vt may be ordered on patients with ARDS to
prevent barotrauma
Mechanical ventilator setting
Positive-end expiratory pressure (PEEP)
- Constant pressure applied at the end of expiration to
help prevent alveolar collapse and keep alveoli
open. - Improves oxygenation, allowing the FiO2 to be lowered. Prolonged high FiO2 can cause lung injury.
- Typical settings for PEEP are 5 to 20 cm H20
- Indicated in ventilator modes AC, SIMV and
pressure control ventilation
Mechanical ventilator setting
Pressure Support (PS)
- Extra push of air to help with spontaneous breath.
- The more pressure support that is applied, the larger
the spontaneous breath with assistance. - Typical settings are 5 to 20 cm H2O.
- Often used with spontaneous breathing trial.