CONCEPTS V WEEK 01

what is gas exchange

the process by which oxygen is transported to cells and carbon dioxide is transported from cells

what is perfusion

the flow of blood through arteries and capillaries delivering nutrients and oxygen to cells

what is hypoxemic respiratory failure

PaO2 less than 60 when the pt is receiving inspired oxygen FiO2 of ≥60%

what is the primary problem of hypoxemic resp failure

inadequate o2 transfer bw alveoli and capillaries

disorders that cause hypoxemic resp failure

pneumonia

pulmonary edema

pulmonary emboli

alveolar injury r/t inhalation of toxic gases

ventilator induced lung injury

4 physiological mechanisms that cause hypoxemic resp failure

VQ mismatch

shunting

diffusion limitation

hypoventilation

normal VQ ratio

1:1

what is the VQ ration

the amount of ventilation (V: air) should be equal to the amount of perfusion (Q: blood) in all parts of the lung

high VQ ratio

more ventilation compared to perfusion

low VQ ratio

less ventilation compared to perfusion

what is shunting

a situation where blood exits the heart without gas exchange occuring

types of shunts

anatomical shunt

intrapulmonary shunt

anatomical shunt

blood passes through an anatomical channel in the heart, bypassing the lungs

ventricular septal defect

intrapulmonary shunt

where blood flows through the pulm capillaries w/o participating in gas exchange

fluid w/in alveoli

what is diffusion limitation

decrease in gas exchange across the alveolar-capillary membrane d/t processes that thicken or destroy the membrane

What is hypercapnic respiratory failure?

PaCO2 greater than normal (45mmhg) and acidemia

primary problem of hypercapnic failure

insufficient CO2 removal

imbalance b/w ventilatory supply and demand

4 categories disorders that can cause hypercapnic resp failure

Abnormalities of the airways and alveoli

-asthma, emphysema, bronchitis, CF

Abnormalities of CNS

-ODs, brainstem infarction, CNS depression

Abnormalities of chest wall

NM conditions

Early manifestations of acute respiratory failure

change in mental status

restlessness, confusion, agitation, combative

tachycardia, mild HTN

severe morning headache (hypercapnia at night)

rapid shallow breaths

late manifestations of acute resp failure

cyanosis

angina, dysrhythmias

permanent brain damage

edema

uremia

impaired renal function

Labs and Diagnostics of acute resp failure

- ↑/↓ pH

- ↑/↓ PaCO2

- ↓ PaO2

- ↑/↓ bicarbonate

- ↓ SaO2

- ↓ tidal volume

- ↓ forced vital capacity

- ↓ minute ventilation

- ↓ negative inspiratory force

- Needs to be documented q1h when a pt in the ICU is on a ventilator

- Altered serum electrolytes, Hgb, WBC, and HCT

- Abnormal findings on chest radiograph

- Abnormal pulmonary artery and pulmonary

artery wedge pressures (PAWP)

different therapies for acute resp failure

respiratory therapy

med therapy

supportive therapy

nutritional therapy

Respiratory therapy for acute resp failure

O2 therapy to maintain PaO2 at 55-60 and SaO2 ≥90%

mobilize secretions through coughing, hydration and suctioning

PPV

medication therapy for acute resp failure: bronchospasm relief

bronchodilators (salbutamol)

IV aminophylline if severe

medication therapy for acute resp failure: airway inflammation reduction

corticosteroids (solumedrol)

medication therapy for acute resp failure: pulmonary congestion

IV diuretics (lasic)

nitroglycerine

CCBs

B Blockers

medication therapy for acute resp failure: pulm infections

IV abx: vanc and ceftriaxone

CXR and sputum cultures

medication therapy for acute resp failure: anxiety pain and agitation

benzos (lorazepam and midazolam)

opioids (morph, fent)

monitor for CV and resp depression

what diet is avoided in those who retain CO2 and why

high carb because carbs metabolize into CO2

what is ARDS

- Sudden and progressive form of acute respiratory failure, where the alveolar-capillary membrane becomes damaged and more permeable by

intravascular fluid

- ↑ capillary permeability → alveoli become filled with fluid → severe dyspnea and hypoxemia refractory to supplemental O2

common direct injuries that can cause ARDS

aspiration

viral or bacterial pneumonia

less common direct injuries that can cause ARDS

trauma

embolism

toxin inhalation

near drowning

O2 toxicity

radiation pneumonitis

common indirect injuries that can cause ARDS

sepsis

severe massive trauma

less common indirect injuries that can cause ARDS

pancreatitis

anaphylaxis

blood transfusion

bypass

DIC

OD

head injuries

shock

Phases of ARDS and timeline

injury or exudative phase occurring 1-7 days post injury

reparative or proliferative phase 1-2 weeks post injury

fibrotic phase 2-3 weeks post injury

manifestations of ARDS (from time of injury to 48hrs post)

dyspnea

tachypnea

cough

restlessness

scattered fine crackles

mild hypoxemia dn resp alkalosis (hypervent)

CXR shows minimal scattered infiltrates

Progressive manifestations of ARDS

increased WOB

tachypnea and tachycardia

retractions (intercostal and suprasternal)

diaphoresis, pallor, cyanosis

sensory and mental changes

diffuse crackles and wheezing

CXR shows extensive bilat infiltrates

hallmark features of ARDS

severe hypoxemia

PaO2/FiO2 ratio < 200, even when FiO2 is ↑ by a mask, cannula, or ET tube

how is ARDS dx

CXR - infiltrates bilaterally

PMH of predisposing condition

Pulmonary artery wedge pressure (≤18mmhg)

refractory hypoxemia (PaO2/FiO2 ratio

complications of ARDS

HA pneumonia

barotrauma

volutrauma

stress ulcers

renal failure

why might ARDS lead to barotrauma

- Rupture of distended alveoli during mechanical ventilation → air will be found in places where it's not usually found → pulmonary interstitial emphysema, pneumothorax, subcutaneous emphysema, pneumoperitoneum, etc.

- Prevention: ventilate pt with smaller tidal volumes

why might ARDS lead to volutrauma

- Large tidal volumes are used to ventilate non-compliant lungs → alveolar fractures, movement of fluids and proteins into alveolar spaces

- Prevention: ventilate pt with smaller tidal volumes

respiratory interventions for ARDS

O2 therapy

invasive ventilation

prone positioning

high frequency oscillation

lateral rotation therapy

medications therapy for ARDS

diuretics

SA bronchodilators

corticosteroids

inotropic or vasopressors for BP

IV fluids

suctioning and coughing

signs of resp distress in the newborn

nasal flaring

retractions

grunting

seesaw breathing

RR

apneic episodes

tachypnea

change in skin colour

newborn respiratory distress syndrome

lung disorder that usually effects preterm infants

caused by surfactant deficiency

how is newborn RDS dx

CXR diffuse granular pattern over both lung fields that resembles ground glass , with dark streaks in this area

low lung volumes

how is newborn RDS tx

establish oxygenation and ventilation

supportive care - maintain homeostasis

surfactant replacement therapy

inhaled NO to prevent shunting

extracorporeal membrane oxygenation (ECMO) add o2 and remove co2