. 2021 Oct 1;14(10):e245301. doi: 10.1136/bcr-2021-245301

Table 1.

Timeline correlating arterial blood gases and respiratory support with select investigations and treatment

Day	0	1	2	2	3	3	8	8	9	10	11	11	12	27	33	39
Time	10:00	01:10	10:20	14:10	08:25	20:00	12:50	21:20	15:50	04:40	04:10	16:30	03:40	12:40	17:10	10:00
Intervention	COVID-19 PCR positive	07:00 steroid started				Day 4 15:00 tocilizumab given	15:00 TTE PFO and RTLIAS anticoagulated		13:00 tracheal intubation				13:00 TOE no RTLIAS	Tracheal extubation		Home
Lymphocytes, ×10⁹/L	0.67	0.92	0.79		0.53				0.65		0.73				2.45
CRP, mg/L		76	70		39		7			17					27
Ferritin, µg/L		1847	2925		1979		785			892
D-dimer, mg/L		0.54	0.55		0.74		9.65			1.95					1.12
LDH, U/L			791		901		1167				726
SpO₂, %	94	91	93	90	92	91	84	94	91	98	98	92	95	92	95	95
RR, breaths/min	24	29	29	30	36	35	29	28	24	32	30	30	30	32	22	21
Position	Sitting	Sitting	Sitting	Sitting	Sitting	Prone	Sitting	Prone	Supine	Prone	Supine	Supine	Prone	Sitting	Sitting
Respiratory support		NC	FM	NRB FM	NRB FM	HFNC	HFNC	Helmet BiPAP	ETT VC+	ETT VC AC	ETT VC AC	ETT VC AC	ETT VC AC	HFNC	NC
FiO₂	0.21					0.35	0.7	1.0	1.0	0.6	0.5	0.5	0.4	0.5		0.21
Flow, L/min		1	10	12	15	40	60	60	60	60	50	50	50	50	1.5
PEEP, cmH₂0								10	14	14	12	12	10
Peak AP, cmH₂0								16	35	34	38	37	35
VT, mL									450	325	441	437	438
Compliance, mL/cmH₂0*									21.4	16.3	17.0	17.5	17.5
pH			7.46	7.45	7.46		7.49	7.45	7.28	7.24	7.37	7.491	7.51	7.5	7.49
PaCO₂, mm Hg			35	37	35		31	35	49	66	51	39.8	37	41	36
BE, mmol/L			1.1	1.3	1.2		0.6	0.2	−4.2	−1.2	2.6	6	5.6	7.6	3.6
PaO₂, mm Hg			52	57	62		43	67	71	97	71	57.6	68	78	66
PaO₂/FiO₂							51	67	71	162	142	115	171	155

Timeline correlating arterial blood gases and respiratory support with select investigations and treatment. Although SpO₂ intermittently fell below 80%, each incident triggered an assessment by a physician and a series of interventions. So, the arterial blood gas analyses presented reflect the patient’s oxygenation after adjustment of respiratory support. For example, on day 9, oxygenation did not improve significantly after endotracheal ventilation and initiation of mechanical ventilation so the patient was positioned prone. The arterial blood gas analyses, performed at 04:40 on day 10 and 03:40 on day 12, reflect the improvement in oxygenation after several hours of prone positioning and reduction of PEEP.

*Dynamic compliance was calculated.

VC AC, volume control-assist control; Peak AP, peak airway pressure; BE, base excess; BiPAP, bilevel positive airway pressure; CRP, C reactive protein; ETT, endotracheal tube; FiO₂, fractional inspired oxygen; FM, face mask; HFNC, high-flow nasal cannula; LDH, lactate dehydrogenase; NC, nasal cannula; NRB, non-rebreathe; PaCO₂, arterial carbon dioxide pressure; PaO₂, arterial oxygen pressure; PEEP, positive end expiratory pressure; PFO, patent foramen ovale; RR, respiratory rate; RTLIAS, right-to-left interatrial shunt; SpO₂, oxygen saturation; TOE, transoesophageal echocardiography; TTE, transthoracic echocardiography; VC+, volume control plus; VT, tidal volume.