Acid Base Balance - WSU N320

Completely Compensated Metabolic Alkalosis

PH= 7.43 PaCO2= 58 HCO3¯=39

Partially compensated Metabolic Alkalosis

PH= 7.52 PaCO2= 52 HCO3¯= 3

What happens to the heart with acidosis? Alkalosis?

Acidosis reduces cardiac contractility.Alkalosis results in hyperexcitability of CNS and peripheral nerves. muscle spasm.

A 23 yr asthmatic female presents in the ED with moderate respiratory distress. Her initial ABG; pH 7.56, PaCO2 20 mm Hg, HCO3 22 mEq/L, PaO2 85 mm Hg.

Acute Respiratory alkalosis, no hypoxemia

What is the P50? High P50 means curve shifted to the ______________ and low P50 means curve shifted to the ____________________.

Measurement of PO2 at 50% Hb saturation. High P50-right shift-lower affinity Low P50-left shift-high affinity

What are 2 causes of metabolic acidosis?

Reduced plasma HCO3¯ or base deficit. Base depleting drugs Aspirin Loss of HCO3¯ Diarrhea Renal disease or failure Increase metabolic acid production. Ketoacidosis (lack of cellular glucose). Lactic acidosis (lack of cellular oxygen). Starvation. Intoxication Ethanol, ethylene glycol

What is the compensation for metabolic acidosis/alkalosis?

Reduction of PaCO2 by hyperventilation. Uncompensated metabolic acidosis is rare. Hyperventilation blows off CO2 quickly-Kussmauls' respirations-diabetic ketoacidosis pH 7.15, PaCO2 26 mmHg, HCO3 - 11

What is the compensation for a respiratory acidosis/alkalosis?

Renal compensation-excrete HCO3¯ ACUTE decrease PaCO2 by 5 mmHg : decrease 1 mEq/L in HCO3¯. CHRONIC decrease PaCO2 by 10 mmHg : decrease 5 mEq/L in HCO3¯.

Give 3 respiratory causes and 3 non-respiratory causes of respiratory acidosis.

Respiratory causes: -Acute upper airway obstruction -Diffuse airway obstruction -Massive pulmonary edema Non-respiratory causes: -Drug overdose -Spinal cord injury -Neuromuscular disease -Head/chest trauma

Factors Influencing the Oxygen Dissociation Curve:SHIFT TO RIGHT (DECREASE IN HEMOGLOBIN-OXYGEN AFFINITY)

-Acidosis -Hypercapnia -Fever

Clinical Findings That May Indicate the Need to Obtain an Arterial Blood Gas Sample: Symptoms

-Acute dyspnea -Chest pain -Hemoptysis -Cough, fever, and sputum production consistent with pneumonia -Symptoms of headache and blurred vision consistent with CO poisoning

Factors Influencing the Oxygen Dissociation Curve:SHIFT TO LEFT (INCREASE IN HEMOGLOBIN-OXYGEN AFFINITY)

-Alkalosis -Hypocapnia -Hypothermia -Fetal hemoglobin -Carboxyhemoglobin

Clinical Findings That May Indicate the Need to Obtain an Arterial Blood Gas Sample: Physical Examination

-Cyanosis -Diffuse crackles or wheezing on auscultation -Severe tachypnea or abnormal breathing pattern -Significant use of accessory muscles -Unexplained confusion -Evidence of chest trauma -Digital clubbing

List 4 clinical signs of hypoxemia.

-Decreased PaO2, SaO2, CaO2 The clinical recognition of hypoxemia often is first suggested by the patient complaining of shortness of breath, especially with exertion. Common clinical manifestations of hypoxemia include tachycardia, tachypnea, hypertension, cyanosis, and confusion. Cyanosis is identified when the level of Hb is at or near normal and its saturation with oxygen drops below 90%. Cyanosis is not recognized in the patient with anemia even if the hypoxemia is severe. As hypoxemia worsens to the extent of tissue hypoxia, metabolic acidosis, bradycardia, and hypotension occur and the patient often becomes comatose. In the intensive care unit, Pv¯o2 less than 35 mm Hg and increases in C(a−v―)o2 above 5 vol% may indicate tissue hypoxia. Tissue hypoxia also may occur with normal arterial oxygenation when inadequate perfusion exists. Clinical signs of an inadequate cardiac output include hypotension, cool extremities, weak or absent peripheral pulses, reduced urine output, and coma.

Clinical Findings That May Indicate the Need to Obtain an Arterial Blood Gas Sample: Chest Radiograph

-Diffuse infiltrates -Hyperinflation -Significant atelectasis -Pneumothorax -Large pleural effusion -Enlarged heart -Lobar consolidation -CO, Carbon monoxide; CO2, carbon dioxide.

Clinical Findings That May Indicate the Need to Obtain an Arterial Blood Gas Sample: Past Medical History

-History of chronic obstructive pulmonary disease (chronic bronchitis and emphysema), especially with cor pulmonale -History of cystic fibrosis -History of pulmonary fibrosis -History of exposure to environmental dusts known to harm the lung -History of diabetes with ketoacidosis -History of chronic renal failure -Significant smoking history (more than 20 pack years)

Clinical Findings That May Indicate the Need to Obtain an Arterial Blood Gas Sample: Laboratory Data

-Unexplained polycythemia -Severe electrolyte abnormalities (e.g., abnormal total CO2)

A 32 year old woman is in the hospital recovering from a fractured hip which she suffered in a motor vehicle accident. At 3 am one morning she develops sharp right sided chest pain and becomes acutely short of breath. She's never had these symptoms before. On physical examination she appears anxious and tachypneic. Her lung examination reveals a pleural friction rub heard over the right lateral chest. A chest x-ray is essentially normal and an electrocardiogram is significant for right atrial enlargement and tachycardia. A blood gas on a 40% oxygen mask shows a pH of 7.35, a PaCO2 of 33, and a PaO2 58. 1. What is wrong with this patient? 2. Why is she hypoxic? 3. What can be done therapeutically?

...

A 64 year old male presents to the emergency room with chest pain, shortness of breath, and nausea. Initially he only had pain upon heavy exertion but over the last week he's had episodes at rest. Today he has had the pain continuously for the past hour. On physical examination he is acutely dyspneic and cyanotic. His lung exam reveals crackles up to the shoulders bilaterally and his neck veins are distended. A blood gas is drawn on 60% oxygen by mask and reveals a pH of 7.34, a PaCO2 of 33, and a PaO2 44. 1. What is wrong with this patient? 2. Why is he hypoxic? 3. What can be done therapeutically?

...

pH: 7.12 PaCO2: 43 HCO3: 27 Your Interpretation Is:

Analytical Error

Why would an anemic patient have tissue hypoxia in spite of having a normal SaO2 and PaO2?

Anemic patients without lung disease may have normal Pao2 and Sao2, but Cao2 is reduced because of the inadequate amount of Hb, and tissue hypoxia may occur without adequate circulatory compensation.

What is the normal CaO2?

Arterial Oxygen Content NORMAL VALUE: 16 to 20 ml/dl blood

Give 4 examples of diffusion defects.

Aveolar collapse (Atelectasis), Thickening of aveolar walls (Aveolar Fibrosis), Aveolar-capillary destruction (Emphysema), Aveolar consolidation (Pneumonia), Frothy secretions (Pulmonary Edema), Interstitial Edema

To determine the degree of ventilation you would look at the _________________ value.

CO2 is a waste product of metabolism; therefore, PaCO2 identifies degree of ventilation in relation to metabolic rate.

What are 3 cardiovascular and central nervous system symptoms of respiratory acidosis?

Cardiovascular Peripheral vasodilation Increased CO Flushed, warm skin Bounding pulse Cerebral vasodilation Arrhythmia's CNS Headache Lethargy Coma (acute hypercapnia >70 mmHg) Cerebral vasodilation Increased ICP

Metabolic and Respiratory Alkalosis Cause

Causes Respiratory alkalosis-pain, anxiety, hypotension, hypoxemia, excessive mechanical ventilation or combination of all. Metabolic alkalosis-NG suctioning, vomiting, antacid therapy pH: 7.59, PaCO2: 42, HCO3¯: 29 Combined Metabolic and Respiratory Alkalosis pH: 7.56, PaCO2: 32, HCO3¯:37, PaO2: 67

What are 3 causes of respiratory alkalosis?

Causes: Pain Hypoxemia-PaO2 < 60 mmHg Acidosis Anxiety

Give 3 clinical manifestations of hypocapnia.

Clinical manifestations Tachypnea Dizziness Sweating Tingling in the fingers and toes Muscle weakness Muscle spasm

pH: 7.36 PaCO2: 29 HCO3: 16 Your Interpretation Is:

Compensated Metabolic Acidosis

pH: 7.38 PaCO2: 17 HCO3: 10 Your Interpretation Is:

Compensated Metabolic Acidosis

pH: 7.43 PaCO2: 51 HCO3: 33 Your Interpretation Is:

Compensated Metabolic Alkalosis

pH: 7.44 PaCO2: 56 HCO3: 37 Your Interpretation Is:

Compensated Metabolic Alkalosis

pH: 7.35 PaCO2: 62 HCO3: 33 Your Interpretation Is:

Compensated Respiratory Acidosis

pH: 7.42 PaCO2: 17 HCO3: 11 Your Interpretation Is:

Compensated Respiratory Alkalosis

For an acute respiratory problem for every 10-15 mmHg increase in PaCO2 the HCO3 increases __________________________.

For acute respiratory acidosis, the plasma HCO3− increases 1 mEq/L for each 10 to 15 mm Hg that the Paco2 increases

Partially compensated respiratory acidosis

High PaCO2, Low pH, Elevated HCO3¯, BE increased pH- 7.32, PaCO2- 60mmHg, HCO3 ¯ 27 mEq/L, BE + 3 mEq/L

Fully compensated respiratory acidosis

High PaCO2, Normal pH, Elevated HCO3¯, BE ++increased pH 7.37, PaCO2 60 mmHg, HCO3¯ -34 mEq/L, BE + 8 mEq/L

Uncompensated or acute respiratory acidosis

High PaCO2, low pH, normal HCO3¯, normal BE pH-7.30, PaCO2-60 mmHg, HCO3¯ - 24 mEq/L, BE 0 mEq/L.

What are the normal values for the following? pH PaCO2 PaO2 HCO3 B.E.

Hydrogen Ion Concentration (pH) NORMAL VALUE: 7.40 with a range of 7.35 to 7.45 Partial Pressure of Arterial Carbon Dioxide (PaCO2) NORMAL VALUE: 35 to 45 mm Hg Arterial Blood Bicarbonate (HCO3) NORMAL VALUE: 22 to 26 mEq/L Base Excess and Base Deficit (BE) normal value: ±2 mEq/L Partial Pressure of Oxygen in Arterial Blood (PaO2) NORMAL VALUE: approximately 80 to 100 mm Hg in room air

Hypoventilation causes _________________ and ______________________.

Hypercarbia and hypoxemia

Define Hypoxia

Hypoxia is a term often associated with hypoxemia and indicates a condition in which tissue oxygenation is inadequate.

K.M. is a 12-year-old boy brought to the emergency department with chief complaints of shortness of breath and cough. His past medical history was positive for allergies and atopic disorders (eczema). His family history was also positive for allergies and asthma. Physical examination revealed the following: Pulse 124 beats/min Respiratory rate 35 breaths/min Blood pressure 120/76 mm Hg Temperature 98.9° F K.M. was restless and used his accessory muscles to breathe. Bilateral expiratory wheezes were heard on auscultation. His chest was clear to percussion but appeared hyperexpanded. His expiratory phase was prolonged. The CBC demonstrated a slight increase in white blood cells as a result of eosinophilia. The Hb and hematocrit levels were within normal limits. ABG measurements were as follows:

INTERPRETATION The pH is alkalotic and corresponds to the decrease in Paco2. Because plasma HCO3− is within normal range, the acid-base status is classified as simple uncompensated respiratory alkalosis. Pao2 and Sao2 are reduced mildly and indicate mild hypoxemia. However, the Cao2 is within the lower limits of normal. Therefore anemia must not be present. The increase in P(A - a)o2 indicates that the respiratory disturbance is causing shunt,V./Q. mismatching, or diffusion defect. The clinical signs of hypoxemia are evident by the tachycardia and tachypnea. The hypoxemia probably would be worse if the patient were not hyperventilating. The respiratory alkalosis is a result of the tachypnea and air hunger. The patient has an increase in the work of breathing because of diffuse airway obstruction, as evidenced by the expiratory wheezing. It is important to note that, although the ABG measurements do not identify any severe abnormalities, the patient's cardiopulmonary system is working hard to maintain these borderline measurements. Without proper treatment, the patient's condition could deteriorate rapidly.

J.B. is a 52-year-old man admitted to the hospital after a sudden onset of severe chest pain and shortness of breath. Thirty minutes after admission to the intensive care unit, J.B. suffered a cardiopulmonary arrest. Cardiopulmonary resuscitation was initiated and was successful after approximately 10 minutes. The initial examination after cardiopulmonary resuscitation revealed that J.B. had hypotension with a spontaneous respiratory rate of 40 breaths/min and a heart rate of 120 beats/min. He was comatose, with central cyanosis, cool extremities, inspiratory and expiratory coarse crackles, and weak pulses. The initial blood gas measurements after resuscitation were as follows:

INTERPRETATION The pH is well below normal, indicating that acidosis is present. The plasma HCO3− is reduced and the Paco2 is normal, indicating metabolic acidosis as the primary problem. When primary metabolic acidosis is occurring, the expected compensatory change in Paco2 can be calculated by using the following formula: Paco2= (1.5×HCO3−)+8±2Expected Paco2=(1.5×14)+8=29±2 Because the measured Paco2 is higher than this value, a ventilatory disorder also must be present. A lack of adequate pulmonary perfusion probably is resulting in an increase in wasted or dead space ventilation. Metabolic and respiratory acidosis are present in this case. The Pao2 of 60 mm Hg is considered mild hypoxemia; however, considering that J.B. is breathing 100% oxygen, the Pao2 is significantly below the predicted value. The P(A - a)o2 is elevated significantly because of shunt,V./Q. mismatching, diffusion defect, or a combination of these. The Sao2 and Cao2 are significantly lower than normal. Because Cao2 is reduced proportionately more than Sao2, the patient must be anemic. The clinical signs of tissue hypoxia and metabolic acidosis probably are related. The lack of adequate oxygenation and circulation of the arterial blood is resulting in anaerobic metabolism and lactic acidosis. When hypoxemia and the clinical signs of inadequate perfusion occur simultaneously, metabolic acidosis from the production of lactic acid is a possibility.

pH: 6.85 PaCO2: 83 HCO3: 14 Your Interpretation Is:

Mixed Disorder- Acidosis

pH: 7.74 PaCO2: 31 HCO3: 41 Your Interpretation Is:

Mixed Disorder- Alkalosis

pH: 7.83 PaCO2: 27 HCO3: 43 Your Interpretation Is:

Mixed Disorder-Alkalosis

Why is the SaO2 not 100%?

Normal anatomic shunt is 3%.

What is the normal SaO2?

Oxygen Saturation NORMAL VALUE: greater than 95%

List the values for mild, moderate and severe hypoxemia

PaO2 60 - 79 (Mild hypoxemia) 40-59 (Moderate hypoxemia) 30- less (Severe hypoxemia)

List the normal values for the following PaO2 PAO2

Partial Pressure of Oxygen in Arterial Blood NORMAL VALUE: approximately 80 to 100 mm Hg in room air Partial Alveolar Oxygen Difference NORMAL VALUE: 100 torr

pH: 6.92 PaCO2: 30 HCO3: 6 Your Interpretation Is:

Partly Compensated Metabolic Acidosis

pH: 7.34 PaCO2: 21 HCO3: 11 Your Interpretation Is:

Partly Compensated Metabolic Acidosis

pH: 7.51 PaCO2: 47 HCO3: 36 Your Interpretation Is:

Partly Compensated Metabolic Alkalosis

pH: 7.62 PaCO2: 46 HCO3: 46 Your Interpretation Is:

Partly Compensated Metabolic Alkalosis

pH: 7.28 PaCO2: 93 HCO3: 42 Your Interpretation Is:

Partly Compensated Respiratory Acidosis

pH: 7.32 PaCO2: 90 HCO3: 45 Your Interpretation Is:

Partly Compensated Respiratory Acidosis

pH: 7.58 PaCO2: 20 HCO3: 18 Your Interpretation Is:

Partly Compensated Respiratory Alkalosis

59 yr male presents in ED with vomiting over the last few days. ABG's are pH 7.55, PaCO2 47 mm Hg, HCO3 34 mEq/L, PaO2 85 mm Hg.

Partly compensated metabolic alkalosis, no hypoxemia

Describe what factors play a role in shifting the oxyhemoglobin dissociation curve to the right and to the left?

The Sao2 measurement is affected by body temperature, arterial blood pH, Paco2, and other factors . Alkalosis, hypocapnia, hypothermia, fetal Hb, and carboxyhemoglobin shift the curve to the left, resulting in higher Sao2 values at the same Pao2. Conversely, acidosis, hypercapnia, and fever shift the curve to the right and result in lower Sao2 values for the same Pao2. These shifts in the curve may be clinically significant. Shifts to the left cause oxygen to be more tightly bound to Hb and make unloading of oxygen at the tissues more difficult, whereas shifts to the right have the opposite effect, resulting in decreased oxygen affinity for Hb and allowing easier unloading of oxygen at the tissues.

A 39 year old female presents to the Emergency Department after being found unconscious by family members up to 2 days prior to presentation. Initial vital signs include: temperature, 29.5 Celsius (rectal); heart rate, 100 beats per minute; respiratory rate, 20 breaths per minute; blood pressure, 139/86 mmHg. Physical examination was significant for depressed mental status, unresponsive to deep pain. Pupils were 4-5 mm and minimally reactive. Initial laboratory testing revealed sodium of 150 mEq/L, chloride of 115 mEq/L, bicarbonate of <5 mEq/L, BUN of 29 mg/dL, creatinine of 3.6 mg/dL and glucose of 130 mg/dL. An arterial blood gas returned: pH 6.66, pCO2 24, pO2 457. Other significant findings included a measured serum osmolarity of 329 mOsm and a lactate of 7.4 mmol/L.

The differential diagnosis for an anion gap metabolic acidosis can be easily remembered using the mnemonic MUDPILES. (See Table 1) Table 1 - MUDPILES M methanol U uremia D diabetic ketoacidosis (DKA), alcoholic ketoacidosis (AKA), starvation ketoacidosis (SKA) P paraldehyde, phenformin (or metformin) CNS depressant I iron, isoniazid L lactic acidosis (cyanide, CO, MetHb) E ethylene glycol (patient ingested this) S salicylates Patient received multiple doses of sodium bicarbonate and hemodialysis Diagnosis made by severe acidosis, increase anion gap 35 (9-14 mEq/L ) Anion Gap = Sodium - (Chloride + Bicarbonate), crystals in urine from ethlene glycol, kidney failure, and my favorite patient admitted ingesting ethylene glycol

List the measurements that are used to assess oxygen status acid-base balance adequacy of ventilation

The measurements obtained from analysis of arterial and mixed venous blood samples are useful in evaluating the following: • Acid-base balance (pH, Paco2, HCO3−, base excess) • Oxygenation status (Pao2, Sao2, Cao2, Pv¯o2) • Adequacy of ventilation (Paco2)

What is the most important indicator of oxygenation?

The most important factor indicating the oxygenation status of the arterial blood is the Cao2. Assessment of the Hb concentration from either the complete blood cell count (CBC) or co-oximeter measurement is crucial in identifying the potential for Cao2. A reduction in Hb (anemia) disallows the possibility of a normal Cao2, regardless of the Pao2 and Sao2, because 99% of the Cao2 is bound to Hb.

pH: 7.08 PaCO2: 42 HCO3: 12 Your Interpretation Is:

Uncompensated Metabolic Acidosis

pH: 7.10 PaCO2: 37 HCO3: 11 Your Interpretation Is:

Uncompensated Metabolic Acidosis

pH: 7.67 PaCO2: 43 HCO3: 48 Your Interpretation Is:

Uncompensated Metabolic Alkalosis

pH: 7.70 PaCO2: 39 HCO3: 47 Your Interpretation Is:

Uncompensated Metabolic Alkalosis

pH: 7.30 PaCO2: 56 HCO3: 27 Your Interpretation Is:

Uncompensated Respiratory Acidosis

pH: 7.53 PaCO2: 27 HCO3: 22 Your Interpretation Is:

Uncompensated Respiratory Alkalosis

A patient with hypoventilation with lung disease will develop hypoxemia from ____________ ________________ and have an increase ____________________.

V/Q mismatch Increase PaCO2

Define hypoxemia

When the measured Pao2 is below the predicted range for a patient breathing room air, regardless of the actual FIO2, it is called hypoxemia. As long as the Pao2 remains above the minimally acceptable limit, hypoxemia does not exist, regardless of the actual FIO2. At any age, a Pao2 of less than 65 mm Hg is considered hypoxemia and a Pao2 of less than 40 mm Hg is considered severe hypoxemia.

A patient has a SpO2 of 90% and the Hgb is 5 gm/dl. Is this patient hypoxic?

Yes. Why? (see below) Dedepending on the patient's gender Hgb Male: 13.5 to 16.5 gm/dl Female: 12.0 to 15.0 gm/dl -if male the Hgb appear normal on towards the low side since 5 gm/dl is under 13.5 gm/dl. -SPO2 cannot distinguish between oxyhemoglobin and carboxyhemoglobin. They provide falsely high oxygen readings even when carboxyhemoglobin levels are as high as 70% Since the PaO2 was not given, I'm using Professor Zimmerman's 40/50/60 ----70/80/90 rule which is PaO2 40---- SPO2 70 50---- 80 60---- 90 -CaO2 = 1.39 x 5 x .90 =6.255 the O2 combined with the Hb is extremely low. =0.003 x 60 mm Hg = 0.18 CaO2 = 6.435 vol % Arterial Oxygen Content NORMAL VALUE: 16 to 20 ml/dl blood The patient's CaO2 estimates to fall below normal limits but as with Sao2, true measurements of Cao2 can be achieved only from a co-oximeter. Cao2 measurements from laboratories without a co-oximeter are only calculated values. A low PaO2 and low Hb produces hypoxic state.

Give 2 causes of a mixed respiratory and metabolic acidosis.

an elevated Paco2 and a reduction in plasma HCO3−. CPR Lack of perfusion-hypoxia Hypoventilation-hypercarbia pH 6.98, PaCO2 98 mmHg, HCO3¯ 10 mEq/L, PaO2 35 mmHg

The relationship between pH and H+

is expressed as follows and demonstrates an important concept: H+ and pH are inversely related. As H+ increases from the addition of acids, pH decreases. Therefore pH values below 7.35 represent increases in the H+ concentration, and the blood is acidotic, or acidemic. When the pH increases above 7.45, the H+ has decreased, and the blood is alkalotic, or alkalemic. It is more exact to refer to deviations in plasma pH with the terms acidemia and alkalemia rather than with acidosis and alkalosis because the reported pH is from blood plasma, and the latter terms do not indicate the compartment that is sampled.

This 49 year old man had his right lung removed because of lung cancer 6 months ago. He presents today for a routine follow-up visit and room air blood gasses are drawn revealing a pH of 7.42, a PaCO2 of 35, and a PaO2 88. 1. Why are this man's blood gases normal?

pH 7.42 (within normal range) PaCO2 over the normal limits PaO2 88 mm Hg (within normal limits) The pt's Left Lung is doing the work of two.

Completely Compensated Respiratory Alkalosis

pH 7.42, PaCO2 33, HCO3¯17

Partially compensated Respiratory Alkalosis

pH 7.47, PaCO2 30, HCO3¯21

Acute Respiratory Alkalosis

pH 7.50 PaCO2 30, HCO3¯23

Acute Metabolic Alkalosis

pH= 7.59 PaCO2 = 42 HCO3¯ =29

Metabolic Acidosis Acute

pH=7.21, PaCO2=37 mm Hg, HCO3¯=19 mEq/L

Metabolic Acidosis Partly compensated

pH=7.31, PaCO2= 27 mm Hg, HCO3¯=14 mEq/L

Metabolic Acidosis Completely compensated

pH=7.37, PaCO2=19 mm Hg, HCO3¯=11 mEq/L

How would you recognize a mixed metabolic and respiratory alkalosis?

recognized by an elevated plasma HCO3− and a Paco2 below normal

If a patient is receiving a FiO2 0.60 and the PaO2 is 95 mm Hg is this patient hypoxemic? Is the PaO2 normal at the given FiO2?

the first answer is No. Why? The PaO2 is normal and the patient is not considered to be hypoxemic. Is the PaO2 normal at the given FiO2? No -The expected PaO2 should be 380 mm Hg. -Thus the A-aDO2 is 285 mm Hg. -Thus serious oxygen exchange is occurring from ventilation-perfusion mismatch.

Can a patient with smoke inhalation with a SpO2 of 98% and Hgb of 13 gm/dl be hypoxic?

yes. Dedepending on the patient's gender Hgb Male: 13.5 to 16.5 gm/dl Female: 12.0 to 15.0 gm/dl -if male the Hgb appear normal on towards the low side since 13 gm/dl is under 13.5 gm/dl. -SPO2 cannot distinguish between oxyhemoglobin and carboxyhemoglobin. They provide falsely high oxygen readings even when carboxyhemoglobin levels are as high as 70% Since the PaO2 was not given, I'm using Professor Zimmerman's 40/50/60 ----70/80/90 rule which is PaO2 40---- SPO2 70 50---- 80 60---- 90 -CaO2 = 1.39 x 13 x .98 =17.708 =0.003 x 60 mm Hg = 0.18 CaO2 = 17.888 Arterial Oxygen Content NORMAL VALUE: 16 to 20 ml/dl blood The patient's CaO2 estimates to fall within normal limits but as with Sao2, true measurements of Cao2 can be achieved only from a co-oximeter. Cao2 measurements from laboratories without a co-oximeter are only calculated values.

Why does diffusion defects respond to increase FiO2?

•Abnormalities in lung structure that slow diffusion of oxygen through ACM, resulting in hypoxemia. •Good response to oxygen therapy.