6 Early Recognition of Respiratory Deterioration

Recognize early changes

Respiratory deterioration can first show up as a change in breathing rate or effort, speech, alertness, oxygen requirement, or overall clinical trend. A low oxygen saturation is not the only warning sign. Assess the whole patient, compare findings with their baseline, and escalate promptly if the patient is worsening or your concern is significant.

Respond to reduced breathing and alertness

A patient who is difficult to rouse after an opioid, with a respiratory rate falling from $16$ to $8$ breaths per minute and an $\mathrm{SpO_2}$ of $92\%$ on supplemental oxygen, may have respiratory depression with inadequate ventilation. Stay with the patient, assess airway, breathing, and responsiveness, and activate the appropriate urgent response. Support the airway and breathing; provide oxygen or reversal medication according to orders and local protocol. Reassess frequently, and obtain blood-gas testing if clinically indicated.

A saturation reading alone may not reveal rising carbon dioxide or worsening ventilation. Do not wait for cyanosis or a further fall in $\mathrm{SpO_2}$ before escalating.

Interpret normal carbon dioxide in severe asthma

In severe asthma, increasing exhaustion, inability to speak in full sentences, very faint air entry (a “silent chest”), or altered consciousness are emergency findings. Call the rapid response or emergency team and urgently escalate care.

An arterial blood gas (ABG) with pH $7.36$ and $\mathrm{PaCO_2}$ $40\ \mathrm{mm\ Hg}$ is not necessarily reassuring in this situation. A patient struggling to breathe may initially lower $\mathrm{PaCO_2}$ by breathing rapidly. As respiratory muscles tire, $\mathrm{PaCO_2}$ may return to a normal range and then rise. The bedside picture and trend matter; a single normal value does not rule out danger.

Interpret blood gases and oxygen targets

Interpret ABG findings alongside the patient’s condition. A low pH with raised $\mathrm{PaCO_2}$ indicates respiratory acidosis. Raised bicarbonate may reflect some chronic compensation.

For example, a patient with COPD and a documented $\mathrm{SpO_2}$ target of $88\text{–}92\%$ who becomes drowsy and confused, with pH $7.29$, $\mathrm{PaCO_2}$ $68\ \mathrm{mm\ Hg}$, $\mathrm{HCO_3^-}$ $32\ \mathrm{mmol/L}$, and $\mathrm{PaO_2}$ $60\ \mathrm{mm\ Hg}$, is concerning for acute-on-chronic ventilatory failure. Escalate urgently for clinical assessment and possible higher-level respiratory support. Continue oxygen titrated to the prescribed target while help is obtained; do not withhold needed oxygen.

Oxygen targets vary by patient. Guidance gives $94\text{–}98\%$ for most adults receiving oxygen and $88\text{–}92\%$ for patients with COPD receiving oxygen. Use the patient’s prescribed oxygen target and local protocol.

Act on worsening effort and mental status

A patient with pneumonia may have an $\mathrm{SpO_2}$ of $95\%$ on room air while deteriorating. If, over an hour, their respiratory rate rises from $20$ to $30$ breaths per minute, they begin using accessory muscles, and they become newly confused, prioritize those changes rather than the apparently acceptable saturation. Reassess promptly, check a full set of observations, and activate the local urgent escalation pathway.

When reporting the change, include the trend, oxygen use, relevant history, and your concern. Structured communication such as SBAR can support handover.

Check readings without delaying care

If a patient appears breathless and restless but a fingertip pulse oximeter reads $97\%$, check whether the result fits the patient. Cold hands and a displayed pulse that does not match the measured pulse raise concern about the reading. Check sensor position and signal, warm the hand if appropriate, and repeat the measurement at a suitable site.

At the same time, assess breathing, circulation, and mental status, and escalate if the patient appears unwell. Pulse oximeters estimate oxygen saturation and readings may be affected by poor circulation, movement, skin pigmentation, skin temperature, or nail polish. $\mathrm{SpO_2}$ complements rather than replaces clinical assessment. A questionable reading must not delay urgent care; further testing, including an ABG, may be needed based on the clinical assessment.

Escalate using the whole clinical picture

Use the patient’s prescribed oxygen target and follow local emergency-response criteria. When the patient is worsening or your concern is significant, escalate promptly. Respiratory rate, work of breathing, speech, alertness, oxygen requirement, and clinical trend all contribute to recognition; neither a single saturation nor a single blood-gas value should override the bedside picture.