W11. Lectures 5-8 CVP

Why must physical therapists understand pulmonary diagnostic tests?

PTs must understand them to accurately assess acid-base balance, alveolar ventilation, and oxygenation.

What are the main pulmonary diagnostic tests covered in this lecture?

Arterial blood gases (ABGs), spirometry, DLCO, and imaging such as chest X-ray, CT, MRI, and V/Q scans.

What does an arterial blood gas (ABG) measure?

An ABG directly measures blood pH and gas levels to assess acid-base balance, ventilation, and oxygenation.

What three major things do ABGs help assess?

Acid-base balance, alveolar ventilation, and oxygenation.

Which organs mainly regulate acid-base balance?

The lungs and kidneys.

What do spirometry and DLCO evaluate?

They are standard pulmonary function tests used to assess pulmonary function.

What imaging tests are commonly used in pulmonary diagnostics?

Chest X-ray, CT, MRI, and ventilation/perfusion (V/Q) scans.

What kind of information does an ABG provide?

It provides a snapshot of a patient’s current metabolic and respiratory status.

What should ABG results always be correlated with?

Medical history, vital signs, and previous results.

What does pH represent on an ABG?

The degree of acidity or alkalinity in the blood.

What is the normal blood pH range?

7.35-7.45.

What is the average normal human blood pH?

About 7.40.

What does PaCO2 represent on an ABG?

The partial pressure of dissolved carbon dioxide in plasma.

What is the normal PaCO2 range?

35-45 mmHg.

What does HCO3- represent on an ABG?

The bicarbonate level, or alkali level, in the blood.

What is the normal HCO3- range?

22-28 mEq/L.

What does PaO2 represent on an ABG?

The partial pressure of dissolved oxygen in plasma.

What is the normal PaO2 range?

80-100 mmHg.

What does SaO2 represent on an ABG?

The percentage of hemoglobin saturated with oxygen.

What is a normal SaO2?

95% or greater.

What is base excess (BE)?

It reflects the concentration of bicarbonate in the body.

What is the normal range for base excess?

About plus or minus 2 mEq/L.

Which ABG value most directly reflects adequacy of alveolar ventilation?

PaCO2.

What PaCO2 finding suggests hyperventilation?

PaCO2 less than 40 mmHg.

What PaCO2 finding suggests hypoventilation?

PaCO2 greater than 40 mmHg.

What PaCO2 finding suggests ventilatory failure?

PaCO2 greater than 50 mmHg.

Which ABG value is used to define oxygenation status?

PaO2.

What PaO2 range indicates mild hypoxemia?

60-80 mmHg.

What PaO2 range indicates moderate hypoxemia?

40-60 mmHg.

What PaO2 level indicates severe hypoxemia?

Less than 40 mmHg.

What relationship is described by the Henderson-Hasselbalch equation?

The relationship between carbonic acid and bicarbonate ion.

Why is the Henderson-Hasselbalch equation clinically useful?

It allows quick identification of the four primary acid-base disorders based on pH and CO2.

What is the general order for interpreting an ABG?

Start with pH, then look at PaCO2, and confirm with HCO3-.

In this lecture’s decision tree, what pH suggests acidosis?

A pH less than 7.40.

In this lecture’s decision tree, what pH suggests alkalosis?

A pH greater than 7.40.

What causes respiratory acidosis?

Increased PaCO2 from hypoventilation, also called hypercapnia.

What are common causes of respiratory acidosis?

Oversedation, head trauma, neuromuscular disorders, cardiac arrest, COPD, pneumonia, and chest trauma.

What symptoms are commonly seen with respiratory acidosis?

Confusion, drowsiness, and tachycardia.

What causes metabolic acidosis?

Decreased HCO3-.

What are common causes of metabolic acidosis?

Ketoacidosis, lactic acidosis, renal failure, and loss of alkali through diarrhea.

What symptoms are commonly seen with metabolic acidosis?

Dyspnea on exertion, deep rapid breathing, fatigue, disorientation, and weakness.

What causes respiratory alkalosis?

Decreased PaCO2 from hyperventilation, also called hypocapnia.

What are common causes of respiratory alkalosis?

Anxiety, pain, fear, excessive mechanical ventilation, hypoxemia, chronic heart failure, and pulmonary embolism.

What symptoms are commonly seen with respiratory alkalosis?

Dizziness, sinus arrhythmia, and numbness or tingling of the lips and extremities.

What causes metabolic alkalosis?

Increased HCO3-.

What are common causes of metabolic alkalosis?

Loss of acid from the GI tract or kidneys, such as vomiting or laxative abuse, and increased bicarbonate from excessive antacid use.

What symptoms are commonly seen with metabolic alkalosis?

Muscle hypertonicity, numbness, tetany, or no symptoms at all.

If pH is low and PaCO2 is high, what primary disorder does that suggest?

Respiratory acidosis.

If pH is low and HCO3- is low, what primary disorder does that suggest?

Metabolic acidosis.

If pH is high and PaCO2 is low, what primary disorder does that suggest?

Respiratory alkalosis.

If pH is high and HCO3- is high, what primary disorder does that suggest?

Metabolic alkalosis.

A SNF patient is somnolent after opioids with pH 7.25, PaCO2 55, PaO2 60, and HCO3- 25. What acid-base disorder is present?

Respiratory acidosis.

Why does that opioid case indicate respiratory acidosis rather than metabolic acidosis?

The pH is low and the PaCO2 is elevated, while the HCO3- is normal.

What oxygenation problem is also present in the opioid case with a PaO2 of 60?

Mild hypoxemia.

What is the likely mechanism of the opioid case causing respiratory acidosis?

Opioid-induced hypoventilation causing CO2 retention.

In one sentence, how do you identify respiratory acidosis on an ABG?

Look for a low pH with an elevated PaCO2.

In one sentence, how do you identify metabolic acidosis on an ABG?

Look for a low pH with a decreased HCO3-.

In one sentence, how do you identify respiratory alkalosis on an ABG?

Look for a high pH with a decreased PaCO2.

In one sentence, how do you identify metabolic alkalosis on an ABG?

Look for a high pH with an increased HCO3-.

Why are pulmonary function tests (PFTs) ordered most often?

Most often, PFTs are ordered to diagnose symptomatic disease such as chronic dyspnea, chronic cough, or unexplained hypercapnia/hypoxemia.

Which patients are especially good candidates for PFTs when screening for symptomatic disease?

High-risk patients such as smokers or those with occupational exposures.

Why might PFTs be used in patients without symptoms?

They can be used to screen for asymptomatic disease in high-risk patients.

What medication is specifically mentioned as a reason to screen for asymptomatic pulmonary disease?

Long-term amiodarone therapy because of its pulmonary toxicity.

Besides diagnosis, what are other major reasons clinicians order PFTs?

Prognostication, estimating surgical risk, and monitoring treatment response.

How can PFTs help with surgical planning?

They help estimate the likelihood of a favorable outcome in surgeries such as lung resection in patients with COPD.

What is still the primary method for monitoring most pulmonary diseases, even when PFTs are used?

Symptoms remain the primary method for monitoring most pulmonary diseases.

What are the three broad diagnostic categories of chronic diffuse lung disease identified by PFTs?

Obstructive lung disease, restrictive lung disease, and pulmonary vascular disease.

What defines obstructive lung disease on PFTs?

Impairment of airflow.

What are examples of obstructive lung disease?

COPD, asthma, bronchiectasis, and cystic fibrosis.

What is bronchiectasis?

Irreversible dilation and destruction of the bronchial tree, often leading to chronic infections.

What defines restrictive lung disease on PFTs?

Reduced lung volumes.

What are examples of restrictive lung disease?

Interstitial lung disease, chest wall pathology, obesity, and neuromuscular disease.

What are examples of interstitial lung disease listed in the notes?

Pulmonary fibrosis and sarcoidosis.

What are examples of chest wall pathology that can cause restrictive lung disease?

Kyphosis and scoliosis.

What are examples of neuromuscular diseases that can cause restrictive lung disease?

ALS and muscular dystrophy.

What are examples of pulmonary vascular disease mentioned in the notes?

Primary pulmonary hypertension and chronic thromboembolic disease.

What PFT finding is often associated with pulmonary vascular disease?

A specific abnormal pattern on DLCO testing.

Are obstructive, restrictive, and pulmonary vascular categories always completely separate?

No. These categories are not mutually exclusive.

Give an example of overlap between PFT categories.

COPD can have both obstructive and vascular findings, and sarcoidosis can show a combination of all three categories.

What components of respiration can PFTs assess?

Airway patency, parenchyma, vasculature, bellows/pump mechanism, and neural control.

What does airway patency refer to in PFT interpretation?

The status of both the large and small airways.

What does parenchyma refer to in PFT interpretation?

The health of the alveoli and the interstitium.

What does vasculature refer to in PFT interpretation?

The pulmonary blood vessels.

What is meant by the bellows and pump mechanism?

The diaphragm and chest wall moving air by changing intrathoracic pressure.

What does neural control refer to in respiration?

The brain’s control of the frequency and depth of breathing.

What are the two main categories of PFTs?

Standard PFTs and specialized or bedside PFTs.

What three tests are usually meant by the term “standard PFTs”?

Spirometry, lung volumes, and DLCO.

What does spirometry primarily measure?

Airflow, mainly to diagnose obstructive disease.

What do lung volume studies primarily measure?

Total lung capacity to help diagnose restrictive disease.

What does DLCO measure?

The integrity of the alveolar-capillary membrane, helping suggest pulmonary vascular disease.

What does ABG testing measure in the context of bedside PFTs?

Oxygen and carbon dioxide levels in the blood.

What is exercise oximetry?

Pulse oximetry measured at rest and during modest activity to detect mild subclinical disease.

What is the purpose of the 6-minute walk test?

It measures the distance a patient can walk in six minutes and is used for prognosis and monitoring treatment response.

What does bedside peak flow measure?

Maximum expiratory airflow in a single breath.

What is bedside peak flow mainly used for?

To gauge the severity of asthma exacerbations.

What do maximum inspiratory and expiratory pressure tests estimate?

Diaphragmatic strength in neuromuscular disease and risk of respiratory failure.

In what specific condition are maximum inspiratory and expiratory pressures especially useful?

Myasthenic crisis.

What are the four individual lung volumes?

Tidal volume, inspiratory reserve volume, expiratory reserve volume, and residual volume.

What is tidal volume (TV)?

The volume of air exchanged during each resting breath.

What is inspiratory reserve volume (IRV)?

The amount of air inhaled above normal tidal volume during the deepest possible breath.