Hemoglobin normally carries oxygen and carbon dioxide- what happens during carbon monoxide poisoning?
carbon monoxide binds tightly to hemoglobin and kicks off oxygen and carbon dioxide
describe the characteristics of carbon monoxide
colorless, odorless, tasteless, non irritant gas
what is the affinity for co to Hb compared to oxygen
250x more attracted to hemoglobin than oxygen
CO+Hb=
HbCO-carboxyhemoglobin
can HbCO carry 02?
no, functional anemia/anemic hypoxemia
what if there is only a small concentration in the air of CO
CO can kill even in small concentrations
what happens when carbon monoxide binds to one Hb site?
it increases the oxygen affinity of the remaining HB sites which causes the hemoglobin molecule to retain oxygen that would otherwise be delivered to the tissue.
during carbon monoxide poisoning which way does the HbO curve shift
to the left- due to the 3 sites have an increase in oxygen affinity and retaining oxygen
LEFT-LOVE OF OXYGEN
what is the result of the increase affinity between hemoglobin and oxygen during CO poisoning.
Blood oxygen content is increased! because oxygen remains on the hemoglobin- none is delivered to the tissues- HYPOXIC TISSUE INJURY
what color do people turn with CO poisoning
Hb turns a bright red color- cadavers acquire an unnatural reddish hue
Can a pulse Ox be reliable during CO Poisoning
NO! Pulse ox is misleading: it can’t differentiate between oxyHb and CarboxyHb
Treatment of CO poisoning
100% 02 (will bump CO from Hb)
S/S of CO poisoning
headache, vertigo, dyspnea, confusion, dilated pupil, convulsion and coma
CO2 is produced in tissues and carried to the lungs. Name the 3 forms
HCO3 (90%0
carbaminohemoglobin (HbCO2)-small amount
Dissolved CO2-(is this in the plasma)?? small amount
what is the formula for dissolved CO2 in the blood
PaCO2 x 0.067=xx/100ml blood
explain the steps of co2 as HCO3
CO2 is produced in the tissues and diffuses into RBC
CO2+H20 (Carbonic anhydrase) form h2co3
h2co3 dissociates into h and hco3
hco3 leaves the RBC in exchange for Cl- and transported to lungs in the plasma
H is buffered inside RBC’s by deoxyHb
explain how the lungs offload c02
HCO3 enters the RBC and Cl leaves
HCO3 bind with h= h2co3
then H20 and CO2
co2 leaves the lung and transport to the alveoli and gets breathed out
Haldane effect
In lungs, oxygenation of Hb promotes dissociation of CO2 from Hb (Haldane effect); therefore, CO2 is released from RBCs
Bohr effect
In peripheral tissue, increase H+ shift curve to right, unloading O2
Central control of breathing name the structure in the brain
medullary respiratory center: located in reticular formation
Apneustic center
Pneumtaxic center
Cerebral cortex
Dorsal Respiratory Group
(PACEMAKER)
Inspiratory Control
Receive Inputs via vagus and glossopharyngeal nerve
output to diaphragm via phrenic nerve and external intercostal nerves
ventral respiratory group
Expiratory control
efferent via internal intercostal nerve
work only during exercise, when expiration becomes an active process
glossopharyngeal nerve
carries signals from carotid bodies and vagus from arch of aorta and lung stretch receptors.
Apneustic center
Located in lower pons
Stimulates inspiration, producing deep and prolonged inspiratory gasp (apneusis)
Pneumtaxic cener
Located in upper pons
Inhibits respiration, and therefore inspiratory volume and respiratory rate.
Adjust rate and depth of respiration
Cerebral cortex
Voluntary breathing; hypoventilation or hyperventilation
Central Chemoreceptors are located where?
medulla
what are these chemoreceptors respond to what?
CO2, H+, 02
Central chemoreceptors are sensitive to??
PH of CSF
if central chemoreceptors sense a decrease in PH what happens?
produces hyperventilation
what does and does not cross the BBB
CO2-crosses the BBB
H+ does not cross the BBB
In CSF: CO2 + H20=
H2CO3= -H + HCO3
H acts directly on central chemoreceptors
increase pco2 and H do what to breathing
stimulate breathing
decrease pc02 and H do what do breathing
Inhibit breathing
what is the role of hyperventilation or hypoventilation
it returns the arterial PCO2 towards normal
Central Control of Breathing. Name the two structures
Brain stem and cerebral cortex
the brain stem coordinates what sensory information and sends signals to respiratory muscles
PC02 Lung stretch irritants muscle spindles tendons and joints
where are peripheral chemoreceptors found?
in the carotid and aortic bodies
what stimulates the peripheral chemoreceptors
decrease p02
increase pc02
decrease PH (increase H)
the peripheral chemoreceptors are stimulated to increase the breathing rate in metabolic acidosis breathing rate is increased Why is that?
because arterial H is increased and PH is decreased
name the last point that peripheral chemoreceptors are responsible for?
responsible to hypoxic drive to respiration
Name the 6 other type of receptors for breathing control
stretch receptors on bronchial walls
irritant receptors stimulated by dust pollen
J (juxtacapillary) receptors
Joint and muscle receptors
Brain Edema
Anesthesia
Stretch receptors on bronchial walls
- Afferent via vagus nerve
- When these receptors are stimulated by distension of the lungs, they produce a reflex decrease in breathing frequency (Hering-Breuer Reflex)
Irritant receptors are stimulated by?
dust, pollen
J (juxtacapillary) receptors
-Engorgement of pul. capillaries in LVH, stimulates J receptors, which then cause rapid, shallow breathing dyspnea
Right-to-left shunts
Normally occur to a small extent because 2% of the cardiac output bypasses the lungs
abnormalities
what congenital anomaly creates a right to left shunt?
to what % of CO is seen with congenital abnormalities
Are seen in tetralogy of Fallot
May be as great as 50% of cardiac output in certain congenital
explain what is seen of PO2 in a right to left shunt
Always result in decrease arterial PO2 because of the admixture of venous blood with arterial blood
how to we determine the magnitude of a right to left shunt?
The magnitude of the right-to-left shunt can be estimated by having the patient breathe 100% O2 and measuring the degree of dilution of oxygenated arterial blood by non-oxygenated shunted (venous) blood
Left-to-right shunts
Are more common than right-to-left shunts because pressures are higher on the left side of the heart
Left to right shunts are usually caused by what?
Are usually caused by congenital abnormalities( e.g. PDA, VSD, ASD) or traumatic injury
in left to right shunt what happens to 02?
Do not result in a decrease in arterial PO2. Instead PO2 will be elevated on the right side of the heart because there has been admixture of arterial blood with venous blood
Supplemental O2
For patient with PO2 ≤ 55mmHg
Hypoxic drive suppression
Oxygen toxicity
Parenchymal damage
Mechanical Ventilation: indication
Apnea, inadequate ventilation
Severe hypoxemia despite O2 supplementation
Airway protection – in coma
Cheyne-Stokes Respiration
Hypersensitivity of resp center to CO2
Period of waxing and waning of tidal volumes separated by periods of apnea
Drug overdose, CHF, hypoxia
Pickwickian Syndrome
Obesity-hypoventilation syndrome
The association of sleep apnea with extreme obesity is referred to as Pickwickian syndrome
Pickwickian Syndrome
Clinical signs
Partial airway obstruction causes snoring Hypoxia-- decrease PO2 Cyanosis Rarely hypercapnia Polycythemia Poor sleep at night Daytime sleepiness
Pickwickian Syndrome
treatment
Oropharyngeal appliances
Positive pressure nasal mask
Surgery
MAC=
Minimum Alveolar Concentration:
tell me about mac
its the concentration of anesthetic gas needed to eliminate movements among 50% of patients challenged by standardized skin incision
MAC is small for potent anesthetics such as halothane and large for less potent gas such as N20
Respiratory Responses to Exercise
O2 consumption CO2 production Ventilation rate Arterial PO2 and PCO2 Arterial pH Venous PCO2 Pulmonary blood flow V/Q ratio
Cardiovascular Responses to Exercise
B. flow to skeletal m.
H.R. SV, CO
Adaptation to High Altitude
Alveolar PO2 Arterial PO2 Ventilation rate Arterial pH Hb Concentration 2,3-DPG Hb-O2 Curve Pul. Vascular resistance