RESPIRATORY 221WEEK 3 WEEK 3

PULMONARY BLOOD PULMONARY BLOOD FLOWFLOW

Vascular SystemVascular System Two Systems : Each have its own Two Systems : Each have its own

reservoir, pump and set of vesselsreservoir, pump and set of vessels

Pulmonary Circulation – low pressure, low Pulmonary Circulation – low pressure, low resistance system. resistance system.

Systemic Circulation - Systemic Circulation -

PULMONARY BLOOD FLOW

Right Vs. LeftRight

Receives deoxygenated bloodRV pumps to lungs (what is its reservoir)Pulmonic Valve receives blood from RV marks

beginning of Pulmonary CirculationLeft

Receives oxygenated blood from lungs through FOUR major Pulmonary veins

LV pumps to system through aortic valve. AV marks beginning of systemic circulation

Significance of lung injury and cardiac injury

Lung injury to alveoli can cause a decrease in blood flow through the lungs

Cardiac injury: If the left ventricle can’t adequately pump blood to the system, the fluid backs up potentially in the lungs

How do we measure pressure?How do we measure pressure? Pulmonary circulation pressure measurement Pulmonary circulation pressure measurement

requires invasive procedure. requires invasive procedure. Pulmonary artery catheter, often referred to as Swan-Pulmonary artery catheter, often referred to as Swan-

Ganz catheter, is a multiple lumen, balloon tipped Ganz catheter, is a multiple lumen, balloon tipped catheter inserted in the heart and pulmonary vessels catheter inserted in the heart and pulmonary vessels through the internal jugular vein ( pg. 113 Beechy through the internal jugular vein ( pg. 113 Beechy book) . This vein provides a direct path to the right book) . This vein provides a direct path to the right atrium. atrium.

There is a balloon located at the distal end, which can There is a balloon located at the distal end, which can be inflated through a different channel inside the be inflated through a different channel inside the catheter. catheter.

There are at least two more channelsThere are at least two more channelsdistal channel- leading to an opening at the tip of the distal channel- leading to an opening at the tip of the

catheter -proximal channel- leading to an opening catheter -proximal channel- leading to an opening located at a number of cm back from the tip. located at a number of cm back from the tip.

Pulmonary Blood PressurePulmonary Blood Pressure•Swan-Ganz•Quadruple Lumen flow directed balloon tipped catheter•Figure 6-2

Rough Schematic

What do they reflect? What do they reflect? CVP (RAP) measures pressure in right CVP (RAP) measures pressure in right

heart ( right atrium)heart ( right atrium) PAP – measures the pressure it takes to PAP – measures the pressure it takes to

move blood past lungs – the resistance in move blood past lungs – the resistance in the lungs the lungs (blood pumped from Rt. Ventricle)(blood pumped from Rt. Ventricle)

PCWP – Reflects (measures) pressures in PCWP – Reflects (measures) pressures in left Heart. Catheter does not go into left left Heart. Catheter does not go into left heart. Balloon is inflated and wedged, cuts heart. Balloon is inflated and wedged, cuts off flow from right side.off flow from right side.

Also known as PCWP, PAWP, PAOPAlso known as PCWP, PAWP, PAOP

Normal Measurements CVP – Right Heart ( rt atrium) 2-6 mmHg PAP – Lung – Sys. 15 – 25 mmHg,

Diastolic 8-15mmHg Mean PAP = 2 x Diastolic + Systolic / 3 10-15 mmHg PCWP – Left Heart – 4-12 mmHg Cardiac Output (QT or CO) – 4-8 L/min Systemic Arterial – 120/80 MAP – 2 x Diastolic + Systolic / 3 – 70-

105 mmHg ( 93)

Recap

2-6 20/10 4-12 4-8L/minCVP PAP PCWP QTRt Lung Lt System

Where is problem? Traffic Jam?Where is problem? Traffic Jam? Accident in the pulmonary capillaries, Accident in the pulmonary capillaries,

blood backs up, increase in CVP, increase blood backs up, increase in CVP, increase PAP, decrease in left PCWP or CO or PAP, decrease in left PCWP or CO or Sys. Arterial pressureSys. Arterial pressure

INTERPRETATIONSCVP= pressures in the right atriumtwo main factors that influence right atrial pressures are the blood volume returning to it and the functioning of the right ventricle. Decreased CVP usually indicates the patient is hypovolemic. Hypotension (LOW BP) will confirm this. Increased CVP usually suggests one of the following possibilities. Fluid overload- check for elevated BP and crackles (wetness) in the bases of the lungs- this is a late finding Tricuspid or pulmonic valve insufficiency- will show up on abnormal EKG and abnormal heart sounds(Murmur)right ventricular failure- right ventricular heart attack(will show on EKG) or patients with COPD and pulmonary hypertension has right ventricular failure, a condition known as Cor Pulmonale

Con’tCon’t PAP- elevated PAP are usually found in patients with the PAP- elevated PAP are usually found in patients with the

following conditionsfollowing conditions1. left ventricular heart failure (CHF) or fluid overload1. left ventricular heart failure (CHF) or fluid overload2. Pulmonary hypertension from COPD-(systolic PAP exceeds 2. Pulmonary hypertension from COPD-(systolic PAP exceeds 40mmHg)40mmHg)3. Pulmonary hypertension from P.E systolic PAP less than 3. Pulmonary hypertension from P.E systolic PAP less than 40mmHg40mmHg

PCWP- considered “elevated” when its greater than 10mmHgPCWP- considered “elevated” when its greater than 10mmHg1. intravascular fluid overload- review charts for renal failure 1. intravascular fluid overload- review charts for renal failure or recent large amounts of oral or intravenous fluidsor recent large amounts of oral or intravenous fluids

2. left ventricular dysfunction with CHF- look for hx of CHF2. left ventricular dysfunction with CHF- look for hx of CHF 3. Mitral valve insuffciency- blood regurgitates back into 3. Mitral valve insuffciency- blood regurgitates back into

the left atrium shown as elevated PCWP reading. the left atrium shown as elevated PCWP reading.

Left Heart Issue looks like… If accident in Left - PCWP increase PAP If accident in Left - PCWP increase PAP

starts to increase starts to increase CO decreased if real bad CO decreased if real bad CVP increase (really bad) CVP increase (really bad)

Hypovolemia - All pressures Low All pressures Low low volumelow volume

What complication…

Does a COPD’er end up running into? Right Heart FailureRight Heart Failure COR PULMONALECOR PULMONALE Can’t exhale air trapping - distends alveoli-Can’t exhale air trapping - distends alveoli-

compresses blood vessels - blood backs compresses blood vessels - blood backs up up

Right heart side failure for patients with Right heart side failure for patients with COPD - PAP is usually higherCOPD - PAP is usually higher

Pulmonary Vascular ResistancePVR

PVR is the resistance that vessels pose to blood flowing through the pulmonary circulation. ANY FACTOR THAT INCREASES PVR INCREASES THE WORK OF THE RIGHT HEART

Normal = 20-200 dynes

Examples

MEAN PAP OF 20, MEAN PAP OF 20, PCWP OF 10 PCWP OF 10 CO OF 6L/MCO OF 6L/M WHAT IS THE CALCULATED PVR ?WHAT IS THE CALCULATED PVR ?

SO A PRESSURE OF 1.67mmHg is needed TO SO A PRESSURE OF 1.67mmHg is needed TO PRODUCE A FLOW OF 1L/M THROUGH PRODUCE A FLOW OF 1L/M THROUGH PULMONARY CIRCULATIONPULMONARY CIRCULATION

Systemic Vascular ResistanceSVR

• SVR is the resistance that vessels pose to blood flowing through the systemic circulation.

• Normal = 700-1600 dynes

SVR = MAP – CVP Qt

Examples BP 170/90 mmHg CVP 2 mmHg CO (Qt) 3

What is SVR?

To reduce PVR Nitric Oxide Pulmonary Vasodilator Normal amount = ___________ “Inhaled NO gas in extremely low

concentrations has been used therapeutically to treat severe pulmonary hypertension and to selectively dilate pulmonary vessels…” –pg. 118 - 119

Useful in neonates with _____________

Hypoxia? May induce increased PVR – causes

vasoconstriction Known as HPV – low Alveolar oxygen pressure PAO2 is less than _60 -_70__mmHg PaO2 about 50 -60 mmHg HPV is unique to only the pulmonary system Keypoint: Oxygen may cause vasodialation

Curveball Systemically, Hypoxia induces vasodilation Pg 120

Other factors that may increase PVR

Acidosis “High PaCO2 increases PVR…” Acidosis - increase in carbonic acidCorrodes pulmonary vesselspg. 120

Clinical Focus 6-4 pg 122

Chapter 7Gas Diffusion

Alveolar-Air Equation

Alveolar-Air Equation1. Atmospheric PO2 = 760 mm Hg x 0.21 = 159 mm

Hg2. Airway PO2 = (760 – 47) x FIO2 = 149 mm Hg Respiratory exchange ratio (R = 0.8)

R = VCO2/VO2 O2 consumption ≈ 250 mL/min CO2 production ≈ 200 mL/min Therefore,

3. Alveolar air equation PAO2 = (760 – 47) x FIO2 – [PaCO2/0.8]

Curveball If FIO2 > 60%, PAO2 = (760 – 47) x FIO2 – PaCO2

Clinical Focus 7-1 & 7-2 Clinical Focus 7-1 & 7-2 Page 132 -133Page 132 -133

Laws Governing DiffusionPhysical Gas Characteristics and Diffusion Graham’s Law

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

Henry’s Law Gas diffusion is directly proportional to the gas partial

pressure (greater pressure, greater diffusion) CO2 diffuses 20 times faster than O2 across

alveolar capillary membrane because of its much greater solubility (it’s actually a heavier molecule)

Lung Function Using Oxygenation Status

Two Indexes To Determine Lung Status#1 A-a gradient PAO2 – PaO2

#2 P/F Ratio

Alveolar-Arterial Oxygen Tension Difference (P[A-a]O2)

The P(A-a)O2 is the oxygen tension difference between the alveoli and arterial blood.

On room air, an acceptable difference = <20mmHg On 30%, an acceptable difference = <30mmHg On 40%, an acceptable difference = <40mmHg …. On 100%, an acceptable difference = <100mmHg

Example using A-a Gradient

Your patient is on a 60% venturi mask. The PaO2 is 140mmHg. You would conclude that:

A. The patient has an increased in A-a gradientB. The oxygenation status of your patient is

within normal limitsC. The patient has a decreased in A-a gradientD. The patient is hyperventilating

Are you concerned?

pH – 7.35PaCO2 – 40 torrPaO2 – 100 torrHCO3 – 24 mEq/LFIO2 – 80%

PaO2/FiO2 ratio

>400 Normal Lung Function300-399 Mild Pulmonary Disease200-299 Moderate Pulmonary Disease<200 Severe/Refractory Hypoxemia

Example:Is this normal?

PaO2 105mmHg on an FiO2 of 90%