Oxygenation

  • alveoli are surrounded by pulmonary capillaries

  • diffusion

    • O2 and CO2 cross the alveolar-capillary membrane

    • edema, inflammation or thinkened membranes impair exchange

  • ventillation

    • air moves into and out of the alveoli

  • perfusion

    • blood flows through the pulmonary capillaries

    • pulmonary embolism (PE) and poor circulation can reduce gas delivery

  • respiratory drive control

    • Medullary and pontine centers coordinate

      respiratory rhythm.

      • Chemoreceptors respond to carbon dioxide, pH

      and oxygen changes.

      • Rising CO₂ typically stimulates increased

      ventilation.

  • nursing consideration

    • Sedating medicines and neurologic injury can

      depress respiratory effort.

      • Observe rate, depth and pattern—not just

      pulse oximetry.

      • Change in level of consciousness may be an

      early warning.



  • Effort of breathing

    • lung compliance

      • ability of the lungs to expand with pressure change

      • reduced compliance is lung expansion ease

    • bronchospasms, secretions and swelling increase resistance


  • hypoxemia

    • low O2 level in arterial blood

    • caused by impaired by one or all three: ventilation, diffusion, or perfusion

    • asses clinical findings, SpO2 and, when indicated, ABGs

    • tested through oximeter

  • hypoxia

    • insufficient O2 at the tissue or cellular level

    • can follow hypoxemia or impaired circulation


  • early or late signs

    • restlessness, anxiety, irritable,

    • tachypnea, tachycardia, or increased work of breathing

    • difficulty speaking in full sentences and altered attention

  • late or severe

    • new confusion or decreased consciousness

    • cyanosis, poor perfusion or dysrhythmia

    • marked exhaustion, bradypnea or apnea are emergencies


  • infection can present with subtle changes in function or cognition


  • upper respiratory infection

    • congestion,

  • pneumonia

    • new or worsening cough and sputum

    • fever or temp abnormality, fatigue, dyspnea

    • crackles, tachypnea, low SpO2

      • maintain airway and oxygenation

      • obtain ordered cultures and tests without delaying urgent support

  • COPD is a narrowing of airflow: scar tissue and inflammation

  • limited expansion: pneumonia, edema, pain, or chest wall injury

  • sudden


  • stridor suggest urgent upper-airway obstruction

  • nonproductive does not mean no secretions, could be too thick


capnograghy (measures CO2 in body) or end-tidal CO2 when indicated

artial blood gas cultures are all under labs in diagnostic evaluations


What it measures

• Noninvasive estimate of arterial hemoglobin

oxygen saturation (SpO₂).

• Uses light absorption through a finger, toe or

other appropriate site.

• Supports assessment and trending of

oxygenation.

What it does NOT measure

• Carbon dioxide levels or ventilation adequacy.

• Hemoglobin concentration or full oxygen

delivery.

• Underlying cause of a low reading.


Factors that affect accuracy

• Poor peripheral perfusion, motion and sensor

problems.

• Nail products, skin/site characteristics and

ambient light can interfere.

• Dyshemoglobins can produce misleading

values.

Clinical judgment

• Compare the displayed pulse with the patient’s

actual heart rate.

• Treat the patient, not the monitor alone.

• If the result conflicts with findings, assess and

consider further testing.


Parameter Typical adult reference Clinical meaning

pH 7.35–7.45 Acid–base status

PaCO₂ 35–45 mm Hg Ventilation / CO₂ retention

HCO₃⁻ 22–26 mEq/L Metabolic component

PaO₂ 80–100 mm Hg Arterial oxygen tension

SaO₂ Approx. 95–100% Arterial hemoglobin saturation



Low oxygen or poor ventilation

• Low PaO₂ reflects decreased arterial oxygen

tension.

• Increased PaCO₂ may indicate hypoventilation

or CO₂ retention.

• Interpret results with pH, vital signs and patient

condition.

Before and after sampling

• Check ordered test and oxygen support.

• Document the oxygen device or FiO₂ at

sampling.

• Monitor puncture site and complications

according to protocol.


nasal canula can only deliver 6 L

for coughing, have patient splint (holding a pillow) when coughing

suction secretions only when patient cannot do it independently

incentive spirometry

    position upright, seal lips

    inhale slowly and deeply; hold briefly as instructed

    rest and repeat as ordered; cough after

when given O2 4 L or more put humidification on it


Device Typical adult use Important safety point

Nasal cannula Low-flow oxygen; often 1–6 L/min Estimated FiO₂ varies with breathing pattern

Simple face mask Moderate oxygen needs; often 6–10 L/min Maintain minimum flow to reduce CO₂

rebreathing

Venturi mask Controlled/selected FiO₂ Set flow for the specific adapter

Nonrebreather High-concentration oxygen; often 10–15 L/min Reservoir bag must stay inflated

High-flow nasal oxygen Heated/humidified high-flow system Requires dedicated equipment and monitoring

noncompliant is now non-adherence

bipap are not well tolerated