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RESPIRATORY 221 WEEK 3 PULMONARY BLOOD FLOW Vascular System Two Systems : Each have its own reservoir, pump and set of vessels Circulation – low pressure, low resistance system. Pulmonary 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 – 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 – 70105 mmHg ( 93) CVP Recap 2-6 CVP Rt 20/10 PAP Lung 4-12 PCWP Lt 4-8L/min QT 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 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) Hypovolemia - All pressures Low low volume What complication… a COPD’er end up running into? Right Heart Failure COR PULMONALE Can’t exhale air trapping - distends alveolicompresses blood vessels - blood backs up Right heart side failure for patients with COPD - PAP is usually higher Does 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 = 20-200 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 = 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 acid Corrodes pulmonary vessels pg. 120 Clinical Focus 6-4 pg 122 Chapter 7 Gas Diffusion Alveolar-Air Equation Alveolar-Air Equation 1. Atmospheric PO2 = 760 mm Hg x 0.21 = 159 mm Hg 2. 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 Page 132 -133 Laws Governing Diffusion Physical Gas Characteristics and Diffusion Graham’s Law Henry’s Law Gas diffusion rate is inversely proportional to the square root of its gram molecular weight (or density); lighter gas = faster diffusion rate 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 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 >400 Normal Lung Function 300-399 200-299 <200 Mild Pulmonary Disease Moderate Pulmonary Disease Severe/Refractory Hypoxemia Example: Is this normal? PaO2 105mmHg on an FiO2 of 90%