Cardio Pulm A&P Study Guide Equations and Concepts

Flashcards covering Cardio Pulm A&P Equations, Lung Volumes, Breathing Patterns, PFTs, and related concepts.

Compliance (C)

How readily the elastic force of the lungs accepts a volume of inspired air; change in lung volume per unit pressure change. C = "delta"V / "delta"P. Average at rest is 0.1 L/cmH2O (100mL air/1cmH2O).

Static Compliance (Cstat)

Compliance measured when the volume has been moved into the lungs and held (no airflow).

Airway Resistance (Raw)

The amount of pressure it takes to move air divided by the amount of flow generated. Normal range is 0.6-2.4 cmH2O/L/sec. Defined as the pressure difference between the mouth and alveoli divided by flow.

Driving Pressure

Pressure difference between two points in a tube or vessel. Typically less than 15 cmH2O and calculated as Plateau pressure - PEEP.

Plateau Pressure

Pressure in the lungs at the end of inspiration, used in calculating driving pressure.

Minute Ventilation (Ve)

Total volume of air breathed in or out in 1 minute. Normal is 5-8 L/min. Ve = Vt (tidal vol) x f (respiratory rate).

Alveolar Ventilation (Va)

Volume of air per minute that actually reaches the alveoli and participates in gas exchange. Normal is ~4-5 L/min. Va = (Vt - Vd dead space vol) x f.

IBW (Ideal Body Weight) for Males

50kg + 2.3 x (height in inches – 60) kg.

IBW (Ideal Body Weight) for Females

45.5 kg + 2.3 x (height in inches – 60) kg.

Tidal Volume (Vt)

The amount of air moved in or out of the lungs in one normal breath (~500mL).

Dead Space (Vd)

Portion of each breath that doesn’t participate in gas exchange (~150mL).

PaO2

Partial pressure of O2 in arterial blood (measured by ABG).

PAO2

Partial pressure of O2 in the alveoli.

Vital Capacity (VC)

IRV + Vt + ERV (Inspiratory Volume + Tidal Volume + Expiratory Volume).

Inspiratory Capacity (IC)

Vt + IRV (Tidal Volume + Inspiratory Volume).

Functional Residual Capacity (FRC)

ERV + RV (Expiratory Volume + Residual Volume).

Total Lung Capacity (TLC)

IRV + Vt + ERV + RV (Inspiratory Volume + Tidal Volume + Expiratory Volume + Residual Volume).

Factors that Increase Flow

Higher pressure gradient, larger airway diameter (less resistance).

Factors that Decrease Flow

Smaller airway diameter, more resistance, lower pressure gradient.

Laminar Flow

Smooth, parallel gas flow, characterized by low resistance.

Turbulent Flow

Chaotic gas flow, requires more pressure to move air (occurs in larger airways and at higher flow rates).

Boyle's Law

Principle that volume and pressure are inversely proportional.

Diaphragm during Inspiration

Contracts downward, increasing thoracic cavity size, causing atmospheric pressure to be higher than intra-alveolar pressure, leading to gas inflow until equilibrium.

Diaphragm during Expiration

Relaxes and moves upward, decreasing thoracic volume, causing intra-alveolar pressure to be higher than atmospheric pressure, leading to gas outflow until equilibrium.

Trans Airway Pressure (Transrespiratory Pressure)

The difference between barometric pressure and alveolar pressure; the pressure needed to move gas in and out of the respiratory system.

Transpulmonary Pressure

The difference between the alveoli and pleural pressures; represents the distending pressure of the lungs (higher pressure means more alveolar expansion).

Normal Breathing Excursion of Diaphragm

1.5 cm (deep breathing is 6-10cm).

Vd (Dead Space Volume)

The portion of each tidal volume that does not participate in gas exchange, filling conducting airways or ventilated but non-perfused alveoli.

Anatomical Dead Space

The volume of air in the conducting airways (nose, pharynx, larynx, trachea, bronchi, and terminal bronchioles) that does not participate in gas exchange.

Apnea

Complete absence of spontaneous breathing.

Eupnea

Normal, spontaneous breathing.

Biot's Respiration

Short episodes of rapid, uniformly deep inspirations followed by 10-30 seconds of apnea.

Hyperpnea

Increased depth of breathing with or without an increased respiratory rate.

Hyperventilation

Increased alveolar ventilation produced by an increase in breathing rate or depth.

Hypoventilation

Decreased alveolar ventilation produced by a decrease in breathing rate or depth.

Tachypnea

Rapid rate of breathing.

Cheyne-Stokes Breathing

10-30 seconds of apnea followed by a gradual increase in volume and frequency of breathing, then a gradual decrease in volume until another period of apnea (associated with cerebral & CHF).

Kussmaul Respiration

An increase in both depth and rate of breathing (associated with diabetic ketoacidosis).

Orthopnea

Condition where a person breathes most comfortably in the upright position, unable to lie flat without increased work of breathing.

Dyspnea

Difficulty breathing in which the individual is aware.

Agonal Respiration

Gasping, labored breathing accompanied by strange vocalizations and myoclonus (muscle twitching or jerks).

Cause of Auto PEEP

Inadequate expiratory time.

Diseases causing Air Trapping

Asthma, COPD, and bronchiolitis (due to small airway obstruction or loss of lung elasticity, preventing complete exhalation).

CXR appearance in Air Trapping

Diaphragm pushed down or flattened, increased lung volume, lungs appear darker, rib spaces widened.

FVC (Forced Vital Capacity)

The maximum volume of gas that can be exhaled as forcefully and as rapidly as possible after a maximal inspiration.

FVC in Restrictive Disease

Decreased.

FVC in Obstructive Disease

Decreased due to air trapping.

FEV1 (Forced Expiratory Volume in 1 second)

The amount (volume) of air a person can forcefully exhale during the first second of a forced vital capacity (FVC).

Normal Adult FEV1%

83% or more of the FVC in the first second (decreases with age).

FEV1 in Obstructive Lung Disease

Decreased.

FEV1 in Restrictive Lung Disease

Normal.

PFTs (Pulmonary Function Tests) Purpose (1)

Differentiate between an obstructive and restrictive disorder.

PFTs (Pulmonary Function Tests) Purpose (2)

Determine the severity, reversibility, and gas exchange efficiency of a patient’s disorder.

Alveolar Dead Space

Alveoli that are ventilated but not perfused with blood.

Physiological Dead Space

The sum of anatomical and alveolar dead spaces. In healthy individuals, it is approximately equal to anatomical dead space.

Mechanical Dead Space

Dead space artificially created by ventilator circuits or breathing equipment, adding extra volume of non-gas-exchanging space.

Surfactant Function (1)

Reduces surface tension in the alveoli.

Surfactant Function (2)

Prevents alveolar collapse.

Surfactant Function (3)

Improves lung compliance.

Surfactant Function (4)

Stabilizes alveoli of different sizes.

Surfactant Function (5)

Helps keep alveoli dry.

Surfactant Composition

Composed of approximately 90% lipids (80% phospholipids, especially DPPC 'dipalmitophosphatidylcholine') and 10% proteins.

Ventilation

The process that moves gases between the external environment and the alveoli (O2 from atmosphere to alveoli, CO2 from alveoli to atmosphere).

Time Constant

How quickly a lung unit (alveolus or region of lung) fills with air or empties during breathing.

Dynamic Compliance (Cdyn)

The change in volume for a given change in pressure while air is flowing; reflects forces in action (flow) and is explained by Poiseuille’s Law and the airway resistance equation.