Exam 2 full review

Respiration

gas exchange between blood and air

Ventilation

process of moving air in and out of the lungs

Minute Ventilation (VE)

Tidal Volume x respiratory rate

Total Lung Ventilation

The sum of alveolar ventilation (VA) and physiological dead space ventilation (Vd), VE = VA + Vd

Minute Alveolar Ventilation (VA)

Volume of inspired air that reaches the alveolar level and participates in gas exchange; effective ventilation, VA = (VE-Vd)

Physiological Dead Space (Vd)

Portion of gas that enters the lung but doesn't participate in respiration; sum of anatomical and alveolar dead space

Factors that increase physiological dead space

Increased respiratory rate; decreased pulmonary blood flow

Anatomical dead space; Vdanat

conducting airways where no gas exchanged; volume constant unless surgically or artifical airway

Anatomical dead space in ml/lb

1ml/lb ideal body weight

Anatomical dead space in ml/kg

2.2 ml/kg ideal body weight

Ideal Body Weight Males

50 kg + (2.3 x height in inches - 60)

Ideal Body Weight Females

45.5 kg + (2.3 x height in inches - 60)

Alveolar Dead Space (Vda)

Volume of gas in the alveoli that does not participate in gas exchange; any alveolar dead space is abnormal; caused by factors that decrease pulmonary blood flow (pulmonary embolus; low cardiac output

Mechanical dead space

volume of rebreathed gas added by equipment; (endotracheal tubes, tracheostomy, corrugated tubing, ventilator circuit)

Dead space to Tidal Volume ration (Vd/Vt)

representative of the percent of ventilation that isn't present in gas exchange

The Bohr Equation

Vd/Vt = (PaCO2 -PeCO2)/PaCO2

Normal Range of Dead Space to Tidal Volume ratio (Vd/Vt)

.30 to .40 (30-40%)

Rate and depth of ventilation affect

Vd/Vt and VA; Dead Space to Tidal Volume ratio and Minute Alveolar Ventilation

Rapid, shallow breathing

This breathing is inefficient

the most efficient ventilatory pattern in terms of the fraction of alveolar minute ventilation recieved

Slow, deep breathing

Matching of ventilation and perfusion

Regional differences exist in ventilation and perfusion even in healthy adults (Zones I,II,III)

Ventilaiton/Perfusion Ratio

VA/Qc; determines PAO2 and PaO2

Ventilation/Perfusion Ratio normal values;

V= 4L/min, Q= 5L/min; .8 value

Lung apices

>.8

Lung bases

<.8

Absolute Shunt (Venous Admixture)

when deoxygenated mixed venous blood bypasses ventilated alveoli and mixes directly with oxygenated, ventilated arterial blood

Right to left shunts

produce arterial hypoxemia

Normal Anatomical Shunt

occurs when mixed venous blood flows through a normal anatomical channel, physically bypassing the alveoli and mixing with arterial blood; 2-5% of Cardiac Output

Pathologic anatomic shunt

occurs when mixed venous blood flows through an abnormal anatomical channel, physical bypassing the alveoli and mixing with arterial blood; atrial and ventricular septal defects

Physiological Shunt (intrapulmonary shunt)

Occurs when mixed venous blood flows through the pulmonary capillaries of airless, unventilated alveoli; occurs in pneumonia, pulmonary edema, atelectesis

Refractory hypoxemia

hypoxemia that responds poorly to oxygen therapy; occurs in physiological shunt

Ventilation-Perfusion Mismatch (relative shunt)

perfusing blood is exposed to some gas exchange by a poorly ventilated alveolus; most common cause of hypoxemia; shunt-like effect

Alveolar to Arterial PO2 gradient P(A-a)O2

Measures Oxygen Transfer Efficiency; 21% O2 is 7-14 mmHg; 100% O2 is 50-60 mmHg

PaO2/FiO2 ratio

measures oxygenation efficiency; normal range of 380-475

Physiological shunt equation

considers both pulmonary and Non pulmonary factors that influence arterial oxygenation; increased indicates more dead space; decreased indicates increased shunt

Respiratory Quotient (RQ)

ratio of CO2 produced to O2 consumed; At res is .8-.85; Increases to 1 durin exercise as more metabolic substrates are used and CO2 is produced

Respiratory Quotient Exchange ratio

The diffusion gradient between alveolar gas and mixed venous blood; VCO2/VO2; (200mL/min)/(250ml/min) = .8

Diffusion

Net movement of molecules from high to low; continues until equilibrium

Diffusion gradients

individual gas partial pressure differences; Oxygen and CO2 have different diffusion gradients (opposite)

Partial Pressure of Inspired Oxygen (PiO2)

Inspired air contains 21% O2; accounts for humidified air in conducting airways

PiO2 equation

PiO2 = (Pb-Ph20) x FiO2

Alveolar Air Equation (PAO2) if FiO2 is < 60

PAO2 = PiO2 - (PaCO2)1.2

Alveolar Air Equation (PAO2) is FiO2 is >60

PAO2 = PiO2 - PaCO2

The value of PH20

47

Ficks Law

summarized the factors that determine the rate of gas diffusion through the alveolar-capillary membrane;

Ficks Law Equation

Vgas = [A x D x (P1-P2)]/(T)

What increases rate of diffusion in Ficks Law

Increase in Surface Area (A), solubility coefficient (D), and pressure gradient (P1-P2)

What decreases the rate of diffusion in ficks law

The greater the membrane thickness (T)

Grahams Law

Gas diffusion rate is inversely proportional to the square root of its gram molecular weight; lighter gas = faster diffusion rate

Henry's law

the amount of gas dissolving in liquid is directly proportional to the gas partial pressure (greater pressure, greater diffusion)

Resting cardiac output

.75 secs; CO2 diffuses 16 times faster than O2 (.015 to .25 seconds)

Cardiac Output in exercise

.25 secs; greater transfer of blood per minute due to increased blood flow; increased surface area due to increased capillary recruitment

(A-a)DO2 gradient equation

[(Pb=PH20) x FiO2]-[(PaCO2)1.2]-PaO2; 1.2 factor not considered if FiO2 is greater than .6

Methods of O2 transport

Dissolved in Plasma (PaO2)

Bound to Hemoglobin (SaO2)

Amount of Oxygen dissolved in plasma

1.5%

Amount of Oxygen bound with hemoglobin

98.5%

Plasma PO2 is closely related to how much O2 binds with hemoglobin (Hb)

Known as O2 tension

Calculating the amount of O2 dissolved in plasma

PO2 x .002 = mL O2/dL dissolved O2

Heme

an organic molecule with 4 pyrrole rings and a ferrous iron ion at its center

Globin

a complex protein consisting of four link amino acid chains; contains 2 alpha and 2 beta chains

Since there are 4 polypeptide chains

each hemoglobin molecule can bind 4 O2 molecules

20ml of O2 per 100 mL of blood

67x more than plasma; delivers 1000 mL/min of O2 at rest even though we only consume 250 mL/min

Male Oxyhemoglobin

14-28 g/dl

Female Oxyhemoglobin

12-16 g/dl

Each gram of Hb can transport _____ ml O2

1.34 mL O2

Arterial Oxygen Saturation (SaO2)

97.5% (PaO2 of 100 mmHg)

Mixed venous oxygen saturation (SvO2)

75% (PvO2 of 40 mmHg); decreases when CO decreases; O2 consumption increases; O2 carrying capacity decreases

Total Volume of oxygen transported in Arterial blood

(CaO2) = (1.34 x Hb x SaO2) + (.003 x PaO2)

O2 transport in arterial blood example

(CaO2) = (1.34 x 15g/dl x .98) + (.003 x 100) = approx 20 mL/dL

Total Volume of oxygen transported in venous blood

(CvO2) = (1.34 x Hb x SvO2) + (.003 x PvO2)

O2 transport in Venous blood example

(CvO2) = (1.34 x 15 x .75) + (.003 x 40) = 15 ml/dl

Oxygen consumption

CaO2-CvO2 = ~5mL/dl (arterial-venous oxygen content difference)

Oxygen-extraction ratio

O2ER= CaO2-CvO2/ CaO2; equals roughly 25%; tissues extracted about 25% of the oxygen from the arterial blood

Oxyhemoglobin Dissociation (Equilibrium) Curve

The relationship between PO2 of the plasma and the % of Hb saturated with oxygen

Middle (Steep) Portion

20-60 mmHg; reflects rapid unloading of O2 molecules binding or release; the "dissociation' portion

Flat portion

PO2 60-100 mmHg; only decreases by 7.5% showing a considerable safter margin; the "association" portion

Right Shift

less affinity for O2

Left Shift

Greater affinity for O2

Things that increase O2 saturation

Increase pH and F Hb; Decreased temp, PCO2 and DPG

Things that decrease O2 saturation

Increase Temp, PCO2, DPG; Decrease pH and F Hb

Hypoxemia

decreased oxygen in the blood

Hypoxia

low level of oxygen available

Hypoxic Hypoxia

inadequate levels of oxygen in arterial blood; low PiO2 (altitude); Severe hypoventilation; Diffusion impairment (Shunt)

Anemic Hypoxia

inadequate levels of functioning hemoglobin (low CaO2)

Stagnant Hypoxia

Caused by the blood not flowing to a body tissue; decreased CO; localized obstruction

Histotoxic Hypoxia

tissues inability to utilize oxygen; cyanide poisoning (inactivation of cellular enzymes for respiration)

HbA

adult hemoglobin

HbF

fetal hemoglobin

HbS

sickle cell hemoglobin

HbM (met Hb)

Methemoglobin

COHb

carboxyhemoglobin

Body produces how much CO2 at rest

200 ml/min

Carbon Dioxide Hydration Reaction (BONUS)

H2O + CO2 ⇋ H2CO3 ⇋ HCO3^- + H^+

CO2 Mechanisms of transport

10% dissolved in plasma; 90% diffuses into the RBC

CO2 dissolved in plasma

slowly generates carbonic acid; helps determine blood acid levels

CO2 diffused into the RBC

80% bicarbonate; 10% bound to Hb (Carbaminohemoglobin)

carbonic anhydrase

increases the speed of carbon dioxide reaction inside RBC by 13,000x

Most CO2 is transported from the tissues to the lungs in the form of

plasma HCO3-

Chloride Shift

the movement of chloride ions into the red blood cells as hydrogen ions move out to maintain the electrochemical equilibrium.

Chloride shift at tissues

Dissolved CO2 enters RBC; undergoes hydrolysis; excess bicarbonate leaves cell; chloride shift