Respiratory Complications Flashcards
LIST OF RESPIRATORY COMPLICATIONS
- Hypercapnia
- Hypocapnia
- Hypoxemia
- Airwayobstruction
minute ventilation =
VE=VTx RR
= tidal volume x RR
ETCO2 values; what do they mean
the amount of carbon dioxide (CO2) in exhaled air, which assesses ventilation. So a high ETCO2 is a good sign of good ventilation, while low ETCO2 is bad sign that represents hypoventilation.
if we have an INCREASE IN CO2; > 50 mmHg what is this called? how would this condition arise?
“Hypercapnia”
“Hypercarbia”
* From slow RR, to small VT, to APNEA > causes hypercapnia
- HYPERCAPNIA- CAUSES
- Hypoventilation
- Apnea
- Rebreathing
- Increased CO2 production
- Increased dead space
what is hypoventilation and how might it arise (and contribute to hypercapnia)
- Less efficient VE
- Any drug that depresses the CNS
- Drug concentration in CNS
- Short for induction drugs (e.g., propofol, alfaxalone)
- Longer for sedatives (e.g., opioids) and inhalant anesthetics
- Any disease that depresses the CNS
- Iatrogenic
- IPPV
> Low VT; Slow RR; Combination of both
what is apnea and how might it arise (and contribute to hypercapnia)
- > 1 minute without a breath
- If, CO2 production continues
> CO2 increases 2-3 mmHg/min - Induction overdose
- Inhalant overdose
how might rebreathing contribute to hypercapnia
- Low Fresh gas flow
- Exhausted sodalime
- Incompetent unidirectional valve
how might increased CO2 production in the body arise
- Fever
> Intrinsic (disease)
> Iatrogenic (exercise) - Laparoscopic procedures with CO2 insufflation
- Thyroid storm
- Malignant hyperthermia (MH)
is PaCO2 = ETCO2? why?
no
* Because of alveolar dead space
* PaCO2 > ETCO2 (≈ 5-10 mmHg)
hypoventilation treatment
- Increase TV
- Increase RR
- Combination
apnea treatment
- Intubate and assist breathing
- Wait for induction drug to wear off
- Adjust inhalant %
rebreathing treatment
- Increased FGF
- Change sodalime
- Fix the valve
- INCREASED CO2 PRODUCTION treatment
- Increase TV and/or RR
- Changes not always needed for laparoscopy
- Control fever
- MH- bad prognosis; Dantrolene
increased dead space treatment
- Adjust the endotracheal tube
- Improve perfusion to the lung
Alveolar Dead Space definition? what is hypoperfusion?
- Ventilated but not perfused
- Hypoperfusion (V/Q > 1)
syndrome associated with hypercapnia?
respiratory acidosis (acute)
syndrome associated with hypocapnia?
respiratory alkalosis
what is hypocapnia? what causes this, in general terms?
DECREASE IN CO2; < 30 mmHg “Hypocapnia” “Hypocarbia”
- From fast RR to large VT
- HYPOCAPNIA- CAUSES
- Hyperventilation
- Decreased CO2 production
- Hypoxia
how does hyperventilation arise?
- Exercise/anxiety
- Over ventilation from mechanical ventilation
> RR, VT, or both - Pain
- Drug-induced
> Panting with opioids
how does decreased CO2 production arise?
- Hypothermia
- Decreased cardiac output
- Cardiovascular collapse/cardiac arrest
how to treat hyperventilation
- Anxiety-“Calmdown”
- IPPV
> Decrease VT and/or RR - Pain
> Analgesics
> Deeper plane of anesthesia - Opioids- no action required
how do we treat decreased CO2 production
- Hypothermia- Warming devices
- Cardiovascular collapse
- Sympathomimetics
- CPR
> Epinephrine
> Cardiac massage
how is hypoxemia defined and what types are there?
-PaO2 < 80 mmHg “Relative hypoxemia” (SpO2 <95%)
-PaO2 < 60 mmHg “Absolute hypoxemia” (SpO2 <90%)
Normal arterial blood gas tensions (mmHg)
for CO2 and O2 at sea level in a dog or horse
or cow or sheep or goat or cat, breathing an
FiO2 of 0.2 are:
PaO2 = 95 (90-100)
PaCO2 = 40
The hemoglobin saturation of arterial and
venous blood at room air is:
SO2 = 98% arterial, 75% venous
normal PaO2 and PvO2 and corresponding SO2 values
PaO2 = 95, SO2 = 98
PvO2 = ~40, SO2 = 75
what proportion of room air in O2 and how does PaO2 change on room air vs pure oxygen?
room air ~20% O2
Room PaO2 = 100 mm Hg
Oxygen PaO2 = 663 mm Hg
PaO2 stands for the partial pressure of oxygen, and it is a measurement of the pressure of the oxygen that is found in the blood.
PaO2 is a sensitive and non-specific indicator of the lungs’ ability to exchange gases with the. atmosphere.
- HYPOXEMIA- Causes
- Low FiO2
- Hypercapnia (Hypoventilation)
- Venous admixture
- FiO2 of 0.2 results in PaO2 of 100 mmHg, if:
- VT is adequate
how does hypercapnia affect PaO2?
decreases, eg
PaO2 =0.21(760-47)-70/0.8 = 0.2 (713) – 88
= 150 – 88
= 62 mm Hg
=> should be 100 for room air
can be due to hypoventilation
how does venous admixture occur?
- R-L shunting (V/Q = 0)
- Low V/Q mismatch (V/Q < 0.8)
- Diffusion barrier
> Edema, Neumonia
what is dead space?
Ventilated but not perfused
* Hypoperfusion (V/Q > 1)
what is a shunt?
Perfused but not ventilated
* Complete small airway closure
* Collapsed alveoli (atelectasis)
* Bronchoconstriction (V/Q < 1)
- Low FiO2 treatment
- Increase FiO2 (> 21%)
- Normalize VT
- Hypercapnia (Hypoventilation) treatment
if hypoventilation,
* Increase TV
* Increase RR
* Combination
could also be due to apnea, rebreathing, increased CO2 production, increased dead space… which we would treat accordingly
- Note that increasing FiO2 would help with hypoxemia but the
hypercapnia needs to be treated
- R-Lshunting treatment
- For complete R-L shunting (V/Q=0):
- FiO2 helps but does not correct hypoxemia
- Correct the reason for the shunt
- Heart defect
> Patent ductus arteriosus
> Ventricular septal defect
Low V/Q mismatch shunting treatment
For V/Q 0 to <1:
* FiO2 can significantly overcome hypoxemia
