RESPIRATORY 221 WEEK 3 PULMONARY BLOOD FLOW

Vascular System  Two Systems : Each have its own reservoir, pump and set of vessels  Pulmonary Circulation – low pressure, low resistance system.  Systemic Circulation -

PULMONARY BLOOD FLOW

Right Vs. Left Right Receives deoxygenated blood RV pumps to lungs (what is its reservoir) Pulmonic Valve receives blood from RV marks beginning of Pulmonary Circulation Left 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?  Pulmonary circulation pressure measurement requires invasive procedure.  Pulmonary artery catheter, often referred to as Swan-Ganz catheter, is a multiple lumen, balloon tipped catheter inserted in the heart and pulmonary vessels through the internal jugular vein ( pg. 113 Beechy book). This vein provides a direct path to the right atrium. There is a balloon located at the distal end, which can be inflated through a different channel inside the catheter. There are at least two more channels distal channel- leading to an opening at the tip of the catheter -proximal channel- leading to an opening located at a number of cm back from the tip.

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

Rough Schematic

What do they reflect?  CVP (RAP) measures pressure in right heart ( right atrium)  PAP – measures the pressure it takes to move blood past lungs – the resistance in the lungs (blood pumped from Rt. Ventricle)  PCWP – Reflects (measures) pressures in left Heart. Catheter does not go into left heart. Balloon is inflated and wedged, cuts off flow from right side.  Also 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   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 – mmHg ( 93)

Recap / L/min CVP PAP PCWP QT Rt Lung Lt System

Where is problem? Traffic Jam?  Accident in the pulmonary capillaries, blood backs up, increase in CVP, increase PAP, decrease in left PCWP or CO or Sys. Arterial pressure

INTERPRETATIONS CVP= pressures in the right atrium two 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’t  PAP- elevated PAP are usually found in patients with the following conditions 1. left ventricular heart failure (CHF) or fluid overload 2. Pulmonary hypertension from COPD-(systolic PAP exceeds 40mmHg) 3. Pulmonary hypertension from P.E systolic PAP less than 40mmHg  PCWP- considered “elevated” when its greater than 10mmHg 1. intravascular fluid overload- review charts for renal failure or recent large amounts of oral or intravenous fluids 2. left ventricular dysfunction with CHF- look for hx of CHF 2. left ventricular dysfunction with CHF- look for hx of CHF 3. Mitral valve insuffciency- blood regurgitates back into the left atrium shown as elevated PCWP reading. 3. Mitral valve insuffciency- blood regurgitates back into the left atrium shown as elevated PCWP reading.

Left Heart Issue looks like…  If accident in Left - PCWP increase PAP starts to increase CO decreased if real bad CVP increase (really bad)  All pressures Low  Hypovolemia - All pressures Low low volume low volume

What complication…   Does a COPD’er end up running into?  Right Heart Failure  COR PULMONALE  Can’t exhale air trapping - distends alveoli- compresses blood vessels - blood backs up  Right heart side failure for patients with COPD - PAP is usually higher

Pulmonary Vascular Resistance PVR 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 = dynes

Examples  MEAN PAP OF 20,  PCWP OF 10  CO OF 6L/M  WHAT IS THE CALCULATED PVR ? SO A PRESSURE OF 1.67mmHg is needed TO PRODUCE A FLOW OF 1L/M THROUGH PULMONARY CIRCULATION

Systemic Vascular Resistance SVR SVR is the resistance that vessels pose to blood flowing through the systemic circulation. Normal = dynes   SVR = MAP – CVP Q t

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   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 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 acid Corrodes pulmonary vessels pg. 120 Clinical Focus 6-4 pg 122

Chapter 7 Gas Diffusion   Alveolar-Air Equation

Alveolar-Air Equation 1. Atmospheric PO 2 = 760 mm Hg x 0.21 = 159 mm Hg 2. Airway PO 2 = (760 – 47) x FIO2 = 149 mm Hg   Respiratory exchange ratio (R = 0.8) R = VCO 2 /VO 2 O 2 consumption ≈ 250 mL/min CO 2 production ≈ 200 mL/min Therefore, 3. Alveolar air equation P A O 2 = (760 – 47) x FIO2 – [PaCO2/0.8] Curveball If FIO2 > 60%, P A O 2 = (760 – 47) x FIO2 – PaCO2

 Clinical Focus 7-1 & 7-2  Page

Laws Governing Diffusion Physical 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)   CO 2 diffuses 20 times faster than O 2 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]O 2 )   The P(A-a)O 2 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 gradient B. The oxygenation status of your patient is within normal limits C. The patient has a decreased in A-a gradient D. The patient is hyperventilating

Are you concerned? pH – 7.35 PaCO2 – 40 torr PaO2 – 100 torr HCO3 – 24 mEq/L FIO2 – 80%

PaO2/FiO2 ratio >400Normal Lung Function Mild Pulmonary Disease Moderate Pulmonary Disease <200Severe/Refractory Hypoxemia Example: Is this normal? PaO2 105mmHg on an FiO2 of 90%